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  • 1.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bernspång, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Norut Northern Research Institute, Narvik.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. College of Civil Engineering, Southeast University, Nanjing.
    Carolin, Anders
    Trafikverket, Trafikverket, Luleå.
    Performance of a prestressed concrete bridge loaded to failure2015In: IABSE Conference Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, Geneva: International Association for Bridge and Structural Engineering, 2015, p. 1088-1095Conference paper (Other academic)
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  • 2.
    Bagge, Niklas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Enochsson, Ola
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Emborg, Mats
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Lundmark, Tore
    Ramböll Sverige AB, Luleå.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Protecting a five span prestressed bridge against ground deformations2015In: IABSE Conference Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, Geneva: International Association for Bridge and Structural Engineering, 2015, p. 255-262Conference paper (Other academic)
    Abstract [en]

    A 55 year-old, 121.5 m long, five span prestressed bridge was situated in the deformation zone close to a mine in Kiruna in northern Sweden. There was a risk for uneven ground deformations so the bridge was analyzed and monitored. Results and measures taken to ascertain the robustness of the bridge are presented.The analysis resulted in an estimate that the bridge could sustain 24 mm in uneven horizontal and 83 mm in uneven vertical displacement of the two supports of a span. To be able to sustain larger deformations, the columns of the bridge were provided with joints, where shims could be inserted to counteract the settlements. To accomplish this, each one of the 18 columns of the bridge was unloaded by help of provisional steel supports. The column was then cut and a new foot was mounted to it. This made it possible to lift each individual column with two jacks, when needed, and to adjust its height by inserting or taking away shim plates.The deformations of the bridge and the surrounding ground were monitored. The eigenmodes of the bridge were studied with accelerometers and by analysis with finite elements (FE) models. Comparison indicated good agreement between the model and the actual bridge, with calculated eigenfrequencies of 2.17, 4.15 and 4.67 Hz, for the first transversal, vertical and torsional modes, respectively. Measurements during winter resulted in higher values due to increased stiffness caused by frozen materials.

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  • 3.
    Blanksvärd, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Häggström, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Trafikverket, Luleå & Borlänge, Sweden.
    Paulsson, Björn
    Trafikverket, Luleå & Borlänge, Sweden.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Southeast University, Nanjing, PR China.
    Test to failure of a steel truss bridge – Calibration of assessment methods2014In: Bridge Maintenance, Safety, Management and Life Extension: proceedings of the Seventh International Conference of Bridge Maintenance, Safety and Management, 7-11 July 2014, Shanghai, China / [ed] Airong Chen; Dan M. Frangopol; Xin Ruan, London: CRC Press, Taylor & Francis Group , 2014, p. 1076-1081Conference paper (Refereed)
    Abstract [en]

    The steel truss railway bridge at Åby River was built in 1957 with a span of 32 m (105 feet). In 2012 it was replaced by a new steel beam bridge and the old bridge was placed beside the river. It was tested to failure to study its remaining load-carrying capacity in September 2013. The test was carried out by Luleå University of Technology by commission from Trafikverket as a part of the European Research Project MAINLINE (www.mainline-project.eu). In this paper some preliminary results are given. Two hydraulic jacks, anchored by cables to the bedrock, pulled the bridge downwards. The bridge remained elastic up to about three times the original design load and the load could then be almost doubled with substantial yielding deformations before a buckling failure appeared in the top girders for a load of ca. 11 MN (1000 short tons) for a midpoint deflection of ca. 0, 2 m (8 inches). No brittle or fatigue failure in any of the joints appeared and the bridge proved to behave in a ductile way with a substantial hidden capacity.

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  • 4.
    Cai, Jianguo
    et al.
    Key Laboratory of C & PC Structures of Ministry of Education, National Prestress Engineering Research Center, Southeast University, Si Pai Lou No. 2, Nanjing 210096, China.
    Deng, Xiaowei
    Department of Structural Engineering, University of California, San Diego, USA.
    Ya, Zhou
    Wuxi Architectural Design and Research Institute Co. Ltd, Wuxi, Jiangsu 214001, China.
    Feng, Jian
    Key Laboratory of C & PC Structures of Ministry of Education, National Prestress Engineering Research Center, Southeast University, Si Pai Lou No. 2, Nanjing 210096, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bistable behavior of the cylindrical origami structure with Kresling pattern2015In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001, Vol. 137, no 6, article id 61406Article in journal (Refereed)
    Abstract [en]

    The deployment of a cylinder based on origami with Kresling pattern, whose basic mechanisms are formed by the buckling of a thin cylindrical shell under torsional loading, is studied in this paper. The model consists of identical triangular panels with cyclic symmetry and has a small displacement internal inextensional mechanism. First, geometric formulation of the design problem is presented. Then, assuming that the deployment and folding process is uniform, the bistable behavior of the cylinder is discussed. It can be found that, during the deployment, the dimensionless strain energy increases first and then reduces to zero but followed by another sharp increase. Moreover, the limit condition of geometry parameters for the bistable phenomenon is also discussed. Finally, the bistable behavior is also studied by using numerical simulations for simple and more complex case of the cylinder with multistory. The numerical results agree well with the analytical predictions. Therefore, comparisons with finite element predictions have shown that the analytical solutions given in this paper are accurate and have validated the assumptions made in the derivations.

  • 5.
    Cao, Dafu
    et al.
    College of Civil Science and Engineering, Yangzhou University.
    Ge, Wenjie
    College of Civil Science and Engineering, Yangzhou University.
    Wang, B.Y.
    College of Civil Science and Engineering, Yangzhou University.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Study on the flexural behaviors of rc beams after Freeze-Thaw cycles2015In: International Journal of Civil Engineering, ISSN 1735-0522, Vol. 13, no 1, p. 92-101Article in journal (Refereed)
    Abstract [en]

    order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, compressive strength test of concrete cubes after 0, 50, 100, 125 freeze-thaw cycles were made, and static flexural experiment of 48 RC beams after 0, 50, 100, 125 freeze-thaw cycles were made. The relationships of relative compressive strength, mass loss rate, relative dynamic elastic modulus and numbers of freeze-thaw cycles were analyzed. The influences of different numbers of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete cubes’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Experimental values of test beams stiffness under short-term load were smaller than theory value. Some under-reinforced RC beams occurs over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after certain numbers of freeze-thaw cycles was derived and its correctness was verified by experiment. Current code for design of concrete structures about crack load and ultimate load are still suitable for RC beams after freeze-thaw cycles

  • 6.
    Cao, Da-fu
    et al.
    School of Civil Science and Engineering, Yangzhou University, No.198 HuaYang XiLu, HanJiang District, Yangzhou 225127, P.R. China.
    Qin, Xiao-Chuan
    School of Civil Engineering, Southeast University, No.2 SiPaiLou, XuanWu District, Nanjing 210096, P.R. China.
    Meng, Shao-Ping
    School of Civil Engineering, Southeast University, No.2 SiPaiLou, XuanWu District, Nanjing 210096, P.R. China.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. School of Civil Engineering, Southeast University, No.2 SiPaiLou, XuanWu District, Nanjing 210096, P.R. China.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Evaluation of prestress losses in prestressed concrete specimens subjected to freeze–thaw cycles2016In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 12, no 2, p. 159-170Article in journal (Refereed)
    Abstract [en]

    Prestressed concrete structures are considered to be reliable and durable. However, their long-term performance when subjected to frost attack is still unclear. In this work, experiments were carried out to evaluate the prestress losses in post-tensioned prestressed concrete specimens subjected to freeze–thaw cycles (FTCs). Two cases were considered: in one case, a series of specimens were prepared and tested in a freeze–thaw chamber; in the second case, the same series of specimens were tested in an indoor environment (outside the chamber). The difference between the prestress losses of the specimens inside the freeze–thaw chamber and those outside the chamber equalled the prestress losses due to FTCs. When using mathematical models to predict the prestress losses due to the FTCs, it was found that they were relatively small when the concrete was slightly damaged. However, they increased rapidly when the FTCs were repeated. The eccentricity of the prestress wires led to larger prestress losses when subjected to FTCs. Moreover, the same cross section and eccentricity resulted in similar prestress losses due to the FTCs, and the relatively high-strength concrete could withstand more FTCs.

  • 7.
    Cao, Jie
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Kong, Lingyi
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Shi, Pan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular dynamics simulations of ion migration and adsorption on the surfaces of AFm hydrates2023In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 615, article id 156390Article in journal (Refereed)
    Abstract [en]

    Chloride salts can cause severe corrosion damage to reinforcing steel bars in cement-based materials whereas nitrite salts inhibit corrosion. The storage and release of these two anions in cement materials occurs mainly at the interface of monosulfoaluminate (AFm) hydrates. In this paper, molecular dynamics are used to analyze the interaction between anions and AFm phases and clarify the competitive relationships between the anions at adsorption sites on the AFm surface. It was found that the ordered structure of the [Ca2Al(OH)6]+ layers of the AFm plays a key role in anion adsorption and that the mobility of ions desorbed from AFm layers decreases linearly with increasing proximity to the AFm surfaces.

  • 8.
    Cao, Jie
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Tongfang
    Southeast University, Nanjing, China.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, Nanjing, China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Effects of Temperature and NaCl Concentration on the Adsorption of C-S-H Gel in Cement Paste: A Multi-fidelity Molecular Dynamics Simulation2023In: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2 / [ed] Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt, Springer, 2023, Vol. 2, p. 499-508Conference paper (Refereed)
    Abstract [en]

    The durability and compressive strength of concrete will vary with the material components, ambient temperature, external intrusion. Using molecular dynamics (MD) methods to study the dynamic behavior of particles in cement-based materials can help us understand the underlying mechanism of property changes in concrete caused by above factors at the atomic level. So far, MD methods have been widely used to analyze the physical and chemical properties of concrete materials and the interaction mechanism between different interfaces at the nanoscale. However, too much complexity in the models will reduce the result accuracy and increase the computational cost. A suitable neural network structure can not only ensure the accuracy of analysis results, but also reduce the computational cost. In this work, MD methods are applied to build the models to explore the diffusivity of Na+ and Cl− in the calcium silicate hydrate (C-S-H) gel pores at different concentration and temperatures. In the process of running models, part of the MD models’ fidelity is reduced to save the computational cost, then the trained multi-fidelity physics informed neural network framework was used to obtain more accurate analysis results. The combination of MD simulations and deep learning methods expands the application range of MD in the field of concrete structure, has good development prospect and application value.

  • 9.
    Du, Linpu
    et al.
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, China.
    Zhang, Wei
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189, Nanjing, China.
    Song, Shoutan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189, Nanjing, China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shaking table test on a novel mega-frame suspended structural system2022In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 52, article id 104440Article in journal (Refereed)
    Abstract [en]

    This paper designed a 1/20 scaled two-segment 19-story mega-frame suspended structure. The seismic behaviors of the structure equipped with viscous dampers (named damping suspended structure, DSS) or rigid connecting rods (named normal suspended structure, NSS) were studied and evaluated by a series of shaking table tests, where three seismic ground motions with two intensities were selected as input motions. Both acceleration and displacement responses of the primary and suspended structures were recorded. The results revealed that the mega-frame suspended system showed good seismic behaviors and viscous dampers could effectively improve its energy dissipation capacities. For DSS, the maximal acceleration and displacement reduction of suspended structures were 75.4% and 39.8% while those of the primary structure were 29.4% and 35.3% respectively. White noise tests showed all models were at the elastic stage under all cases. Evident relative displacements between the primary and subordinate structures were observed for DSS, in this case, the suspended floors were considered as the additional mass of the primary structure and the energy could be dissipated by the swing of suspended floors. The energy dissipation mechanism of DSS was theoretically analyzed while the effect of connection forms on vibration reduction was discussed.

  • 10.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Bell, Brian
    UIC, Network Rail, London.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Häggström, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. College of Civil Engineering, Southeast University, Nanjing.
    Lundgren, Karin
    Chalmers University of Technology, Department of Civil and Environmental Engineering.
    Plos, Mario
    Chalmers University of Technology, Department of Civil and Environmental Engineering.
    Larsson, Oskar
    Faculty of Engineering, LTH, Department of Constructional Sciences, Lund University.
    Casas, Joan Ramon
    Universitat Politècnica de Catalunya.
    New technologies to extend the life of elderly rail infrastructure: Deliverable 1.3 in MAINLINE - a project within the EC 7th Framework Programme2015Report (Refereed)
    Abstract [en]

    There are many traditional technologies available to extend the life of elderly rail infrastructure, some of which are being improved or developed, whilst new technologies continue to emerge.In two earlier reports a benchmark of new technologies was given and assessment methods were presented, ML-D1.1 (2013) and ML-D1.2 (2013). In this report, ML-D1.3, an overview is given of some of the most promising new or updated technologies. Based on the findings, work in the Mainline project has focused on the following two areas for bridges, tunnels and track:- Assessment methods- Repair and Strengthening methodsSome of the methods are still under development and may not yet be available commercially. Hence these are presented on a “for information” basis and as something that may be introduced on a broader scale in a near future.In the report assessment and strengthening of bridges are treated in Chapter 4 and Chapter 5.Tunnels are treated in Chapter 6 and track and earthwork in Chapter 7.The report also includes with five appendices with details of important work that has been donein the MAINLINE project. Appendix A presents results from the assessment and full scale testing to failure of a 50 year old metallic truss bridge. Appendix B presents results from the strengthening by post-tensioning of a concrete trough bridge. Appendix C presents methods to extend life for tunnels. Appendix D proposes methods for the assessment of fatigue andAppendix E, finally, gives a fairly comprehensive list of references on how to extend the life of structures.A Guideline for application of the new technologies is given in ML-D1.4 (2014).

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  • 11.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. WSP, Luleå, Sweden.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Puurula, Arto
    Savonia University of Applied Sciences, Kuopio.
    Häggström, Jens
    Trafikverket, Luleå, Sweden.
    Paulsson, Björn
    Charmec, Chalmers University of Technology.
    Load-testing used for quality control of bridges2018In: Quality Specifications for Roadway Bridges: Workshop of COST TU 1406 / [ed] José Matos, 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Load testing is a way to control the capacity and function of a bridge. Methods and recommendations for load testing are described and examples are given form tests carried out. In order not to damage the bridge being tested, the load must be limited, often to be within the serviceability limit state (SLS). Numerical models can be calibrated by load tests and then be used to check the carrying capacity for higher loads than what has been tested. Need for further work and recommendations are discussed. By effective planning costs can be saved and a more sustainable use of bridges can be obtained.

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    fulltext
  • 12.
    Fang, Mengxiang
    et al.
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wang, Tongfang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Shi, Pan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Jiang, Biao
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Compressive reactive molecular dynamics on mechanical and structural behaviors of geopolymers: Imposing lateral constraints and varied temperatures2024In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 249, article id 107257Article in journal (Refereed)
  • 13.
    Ge, Wenjie
    et al.
    College of Civil Science and Engineering, Yangzhou University.
    Zhang, Jiwen
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, Nanjing.
    Cao, Dafu
    College of Civil Science and Engineering, Yangzhou University.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Flexural behaviors of hybrid concrete beams reinforced with BFRP bars and steel bars2015In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 87, p. 28-37Article in journal (Refereed)
    Abstract [en]

    Flexural behaviors of hybrid concrete beams reinforced with BFRP (Basalt Fiber Reinforced Plastic) bars and steel bars are studied in this paper. Tensile test, standard pull-out test of BFRP bars, and static flexural experiment of five different hybrid reinforced concrete beams were made. The tests show that BFRP bars have high tensile strength and low elastic modulus compared with steel bars. The bond strength between BFRP bars and concrete is similar to the bond strength of steel bars and concrete and shows good bond performance. The bond strength relative coefficient of BFRP bars can be considered to be 1.0. The crack spacing and crack width are analyzed and suitable formulas for calculation are proposed. The flexural capacity of appropriate hybrid reinforced beams is analyzed and a simplified formula for calculating its value is proposed. Results show that the value of the flexural capacity calculated by the proposed simplified formula is close to the experimental value. This proves that the formula can be successfully applied. By controlling the reinforcement ratio and the value of Af/As appropriately, the ductility of hybrid reinforced beams can meet the requirements of normal service conditions.

  • 14.
    Grip, Niklas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, Nanjing.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Vibrationsanalys för tillståndsbedömning av byggkonstruktioner: Tillämpningsexempel : (Main results and summary in Swedish. Detailed results in English Appendices.)2017Report (Other academic)
    Abstract [en]

    In the project,methods are presented and appliedfor assessment ofdifferent types ofbuilding structures with and without damages.The assessmentis done withhelp ofvibration analysis.Detection of defects of different types and sizes are discussed. The influence of boundary conditions isstudied in order to get agreement between predicted and measured Eigen modes and Eigen frequencies.With the program that has been developed,is it now possible to detect cracks in simple concrete structures with help of measurements of vibrations. For more advanced structures there is a potentialto further develop the program. Measurements and analyses have been made for fivestructures:(1) A concrete slab–Cracks have been detected based on vibrationmeasurementsand a successivelyupdated Finite Element Model (FEM).(2) Aconcrete archbridge at Långforsen in Kalix River-Unknown boundary conditions havebeen possible todetermine with help of vibration measurementsregarding for example foundation properties. Detection of specific damages hasnot yet been possible.(3) A steel truss bridge over Åby River–Some detection of damages hasbeen possible to carry outwith Finite Element Model updatingregarding corrosion and mechanical damages.. (4) A prestressed concrete bridge to the mine in Kiruna-Several models of theundamaged and damagedbridgehave been established and they have been calibrated to measured vibration propertieswith good results.(5) A nine storey concrete building in Luleå–A FEM model has been developedfor the serviceability limit stateand results from it has been compared to measured vibrationswith good results.A general presentation is given ofthe developedmethods and resultsin the main text. Detailed descriptions are provided in Appendices.A program is presented with ready-to-use models for the studied structures. The program may be downloaded and is presented in detail in an Appendix.

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    Projektsammanfattning (project summary in Swedish, 11 pages)
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    Huvudrapport (main report in Swedish, 34 pages)
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    Appendices with some more detailed results (English, 260 pages)
  • 15.
    Huang, Zheng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Modelling of Damage and its Use in Assessment of a Prestressed Bridge2016Report (Other academic)
    Abstract [en]

    A 55 years old and 121.5 m long ve-span prestressed bridge has been subjected toshear failure test in Kiruna, Sweden. This in-situ test is a desirable test to validate andcalibrate the existing nonlinear nite element program for predicting the shear behaviorof reinforced and prestressed concrete structures.Two 3D nite element (FE) models of the Kiruna Bridge are built in commercial soft-ware Abaqus, one using shell-elements and one using a combination of shell and beam ele-ments. Predictions obtained from these two models are well consistent with mode shapesand eigenfrequencies computed from acceleration measurements on the bridge before andafter loading it to failure. Shear-failure test of this bridge performed by Lulea Universityof Technology (LTU) is also simulated using the built-in concrete damage plasticity (CDP)model in Abaqus. The predicted load-displacement curve is in good agreement with themeasurement. Verication of the CDP model is conducted at element and member levelwith two dierent damage parameter evolutions. According to the verication, it indi-cates the damage parameter will aect the predicted shear behavior of reinforced concretestructures and it is not reliable to adopt the CDP model to simulate the shear behaviorof reinforced concrete structures based on the present research.A long term goal is to use use the measured mode shapes, eigenfrequencies and FEmodels for evaluating methods for damage identication. Such methods are important formaintenance of dierent structures, for extending their life span and for better knowledgeof their load carrying capacity. We describe how so-called sparse regularization niteelement method updating (FEMU) methods can be used. We then demonstrate someimportant properties of such methods with simulations on a Kirchho plate. For instance,the simulations suggest that both eigenfrequencies and mode shapes should be used forprecise localization of the damage.

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  • 16.
    Huang, Zheng
    et al.
    Southeast University, Nanjing, China.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Bagge, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Modelling of Damage and its use in Assessment of a Prestressed Concrete Bridge2016In: IABSE CONGRESS, STOCKHOLM, 2016: Challenges in Design and Construction of an Innovativeand Sustainable Built Environment / [ed] Lennart Elfgren, Johan Jonsson, Mats Karlsson, Lahja Rydberg-Forssbeck and Britt Sigfrid, CH - 8093 Zürich, Switzerland, 2016, p. 2093-2108Conference paper (Refereed)
    Abstract [en]

    A five-span prestressed concrete bridge has been subjected to a loading test up to failure in Kiruna, Sweden. The bridge was 55 years old and had a length of 121.5 m. The test has been used to validate and calibrate existing nonlinear finite element programs for predicting the shear behavior of reinforced and prestressed concrete structures. Two 3D finite element (FE) models of the Kiruna Bridge are built in commercial software Abaqus, one using shell-elements and one using a combination of shell and beam elements. Predictions obtained from these two models are well consistent with mode shapes and eigenfrequencies computed from acceleration measurements on the bridge before and after loading it to failure.The shear failure of the bridge is also simulated using the built-in concrete damage plasticity (CDP)model in Abaqus. The predicted load-displacement curve is in good agreement with the measurements. Verification of the CDP model is conducted at element and member level with two different damage parameter evolutions. The verification indicates that the damage parameter will affect the predicted shear behavior. It does not seem to be reliable to adopt the CDP model to simulate the shear behavior in the present research. A long term goal is to use use the measured mode shapes, eigenfrequencies and FE models for evaluating methods for damage identification. Such methods are important for maintenance of different structures, for extending their life span and for better knowledge of their load carrying capacity. The use is described of so-called sparse regularized finite element method updating (FEMU) methods. Some important properties of such methods are demonstrated using simulations on a Kirchhoff plate. For instance, the simulations suggest that both eigenfrequencies and mode shapes should be used for precise localization of the damage.

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    fulltext
  • 17.
    Huang, Zheng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University, Nanjing, China.
    Bagge, Niklas
    Department of Bridge & Hydraulic Design, WSP Sverige AB, Gothenburg, Sweden.
    Nilimaa, Jonny
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Validation of a numerical method for predicting shear deformation of reinforced concrete beams2019In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 197, article id 109367Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to validate a 2D nonlinear finite element (FE) model for estimating the post-cracking shear deformation of reinforced concrete (RC) beams. The proposed FE model treated the cracked concrete as an orthotropic material in the framework of the fixed-crack approach. The experimental data for both the overall response (including the total and shear-induced deflection) and the detailed response (including the mean shear strain, mean vertical strain and principal compressive strain angle) of five I-section RC beams, monitored by the main authors of this paper with the Digital Image Correlation technique, were used to verify the proposed model. In addition, 27 further test beams evaluated in independent research programs were collected to assemble a database. The proposed FE model was further verified against the database. Two additional FE models (the rotating-crack model developed in this work and Response-2000 developed by Bentz (2000)) were also evaluated by simulating the detailed responses of the beams in the database. The results obtained validate the proposed FE model for predicting the post-cracking shear deformation of RC beams and indicate that the proposed FE model is more suitable for simulating the shear behaviour of RC beams than the rotating-crack model or Response-2000.

  • 18.
    Huang, Zheng
    et al.
    School of Civil Engineering, Southeast University,Nanjing, China.
    Tu, Yongming
    School of Civil Engineering, Southeast University,Nanjing, China.
    Meng, Shaoping
    School of Civil Engineering, Southeast University,Nanjing, China.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A practical method for predicting shear deformation of reinforced concrete beams2020In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 206, article id 110116Article in journal (Refereed)
    Abstract [en]

    This paper presents a practical method for predicting the deflections, including both the flexure and shear contributions, of reinforced concrete (RC) beams. The shear force - shear strain (V-γ) curve of a section in the shear span of RC beams is represented by a piecewise model and the tangent shear stiffness after shear cracking, Kt,cr, is assumed to be constant. A 2D finite element model, which has been validated for predicting shear deformation of RC beams, was used to identify factors that may affect the shear reduction factor (the ratio of Kt,cr to the elastic shear stiffness) and establish methodology for predicting the V-γ curve. Two types of methods, integration-form and closed-form, for predicting the total deflection were developed, in which the flexure-induced deflection (FD) was predicted using the Bischoff model while the shear-induced deflection (SD) was predicted using the method proposed in this paper. Comparison of the predictions with experimental results confirms that the Bischoff model provides reliable predictions of FDs of RC beams with and without shrinkage. It also shows that the proposed method can provide accurate predictions for SD after shear cracking, provided the effect of shrinkage on the shear cracking load is adequately quantified.

    Support from: National Natural Science Foundation of China (No. 51378104) and A Project Funded by the Priority Academic Program Development ofJiangsu Higher Education Institutions. The Development Fund of the Swedish Construction Industry (SBUF), the Swedish Research Council Formas and Elsa and Sven Thysell Foundation

  • 19.
    Häggström, Jens
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, School of Civil Engineering, Nanjing.
    Full-scale testing to failure of a steel truss railway bridge2017In: Proceedings of the Institution of Civil Engineers: Engineering Sustainability, ISSN 1478-4637, E-ISSN 1751-7664, Vol. 170, no 2, p. 93-101Article in journal (Refereed)
    Abstract [en]

    Significant resources have been invested in maintaining existing infrastructure. Many structures are becoming old, do not meet current requirements, or are reaching the end of their life cycle. It is not feasible or sustainable to replace all of those that may be deemed obsolete; however, often their specified capacities are very conservative. So there is an urgent need to obtain more robust knowledge of their true status. This paper describes a unique project, in which a 33 m long steel truss railway bridge (over the Åby River) was tested to failure. The findings can be used to identify optimal solutions for other bridges of the same design that are still in use, notably the bridge over Rautasjokk (a river in Sweden). These two bridges were tested in three stages. This paper focuses on the second stage, wherein Åby Bridge was subjected to static full-scale testing to failure, by pulling it downwards. The global failure mode consisted of buckling of the top chord with yielding of the steel starting at a total load of 8 MN and the peak load being reached at around 11 MN, corresponding to a load approximately four to five times higher than the characteristic design load.

  • 20. Ji, Yuanhui
    et al.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Coupling mass transfer with mineral reactions to investigate CO2 sequestration in saline aquifers with non-equilibrium thermodynamics2011In: Proceedings of the World Renewable Energy Congress 2011 (WREC 2011): 9-13 May, Linköping, Linköping University Electronic Press, 2011Conference paper (Refereed)
    Abstract [en]

    The coupling behaviors of mass transfer of aqueous CO2 with mineral reactions of aqueous CO2 with rock anorthite are investigated by chemical potential gradient and concentration gradient models, respectively. SAFT1-RPM is used to calculate the fugacity of CO2 in brine. The effective diffusion coefficients of CO2 are obtained based on the experimental kinetic data reported in literature. The calculation results by the two models and for two cases (mass transfer only and coupling mass transfer with mineral reaction) are compared. The results show that there are considerable discrepancies for the concentration distribution with distance by the concentration gradient and chemical potential gradient models, which implies the importance of consideration of the non-ideality. And the concentrations of aqueous CO2 at different distances by the concentration gradient model are higher and further than that by the chemical potential gradient model. The mineral reaction plays a considerable role for the CO2 geological sequestration when the time scale reaches 10 years for the anorthite case.

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  • 21.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Freeze-thaw damage evaluation and model creation for concrete exposed to freeze–thaw cycles at early-age2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 312, article id 125352Article in journal (Refereed)
    Abstract [en]

    Concrete subjected to freeze–thaw cycles action at early-age will suffer serious physical damage, resulting in degradation of the concrete’s performance. The subsequent curing conditions after early-age freeze–thaw cycles (E-FTCs) are critical to the development of the properties of frost-damaged concrete. Four test environments were set up for this study, based on different numbers of E-FTCs and subsequent curing conditions. The later-age resistance to freeze–thaw of concrete exposed to E-FTCs was evaluated by analysing the influence of pre-curing times and curing conditions. Results show that the earlier the FTCs occur, the worse the later-age freeze–thaw resistance is. In particular, for the frost-damaged concrete with a pre-curing time of 18 h, its freeze–thaw resistance is significantly worse than that of other concretes that have a longer pre-curing time. The increase in the number of E-FTCs exacerbates the damage to early-age concrete, which causes the reduced later-age freeze–thaw resistance. Subsequent water curing can significantly improve the freeze–thaw resistance of damaged concrete, while air curing is the least effective. Based on previous freeze–thaw damage models, prediction models for concrete exposed to E-FTCs were created by using the test data obtained in this study. The critical pre-curing strengths which can ensure that the damaged concrete has satisfactory frost resistance at later-age were thus obtained. For concrete structures expected to experience E-FTCs, adequate pre-curing strength and good re-curing conditions are essential.

  • 22.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, People’s Republic of China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, People’s Republic of China.
    Shi, Pan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, People’s Republic of China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, 8517, Narvik, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mechanical and durability properties of concrete subjected to early-age freeze–thaw cycles2021In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 54, no 6, article id 211Article in journal (Refereed)
    Abstract [en]

    Early-age frost damage to concrete used in winter construction or in cold environments negatively affects the development of the hydration process and the performance of the concrete, thereby reducing the service life of the building structure. Experimental research was carried out to investigate the compressive strength, resistance to chloride penetration and resistance to freeze–thaw of concrete specimens subjected to early-age freeze–thaw cycles (E-FTCs). The effects that different pre-curing times of concrete and mineral admixtures have on the properties of early-age frost-affected concrete were also analyzed. Results show that the earlier the freeze–thaw cycles (FTCs), the poorer the later-age performance. Later-age water-curing cannot completely restore the damage that E-FTCs do to concrete. In the same conditions used in this study, the effects of E-FTCs on later-age mechanical and durability properties of ordinary Portland cement concrete (OPC) are small. The incorporation of fly ash significantly reduces the resistance to freeze–thaw of concrete during early-age and later-age. The presence of silica fumes has an adverse effect on the later-age resistance to freeze–thaw. In general, the recovery percentage of later-age durability indexes of concrete subjected to E-FTCs is lower than that of compressive strength. For concrete subjected to E-FTCs, it is more important to ensure the recovery of later-age durability.

  • 23.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, P.R. China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Zhang, Yu
    School of Civil Engineering, Southeast University, P.R. China.
    Resistance to salt-corrosion of concrete with externally bonded FRP sheets in marine environment2022In: Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability: Proceedings of the Eleventh International Conference on Bridge Maintenance, Safety and Management (IABMAS 2022), Barcelona, Spain, July 11-15, 2022 / [ed] Joan Ramon Casas; Dan M. Frangopol; Jose Turmo, CRC Press, 2022, p. 2495-2502Conference paper (Refereed)
    Abstract [en]

    FRP sheets are often externally bonded onto concrete surface to strengthen concrete bridges. Salt-corrosion resistance of concrete strengthened with three types of FRP sheets, i.e. unidirectional CFRP, unidirectional BFRP, bidirectional BFRP, was evaluated by measuring the compressive strength and chloride ion concentration (CIC) profile after NaCl solution immersion. Results show that as exposure time increases, the compressive strength of BFRP-strengthened concrete decreases, while that of CFRP-strengthened concrete changes little, but both are higher than that of un-strengthened concrete. Internal CICs of FRP-strengthened concrete decrease significantly, with the reduction of over 80%. Wrapping bidirectional BFRP sheet shows the strongest chloride penetration resistance, followed by unidirectional CFRP and finally unidirectional BFRP. Chloride diffusion coefficient of the concrete shows obvious time and depth dependence, which reduces with time, and increases and tends to stabilize along depth. A model of chloride diffusion coefficient considering time-depth dependence was established to predict CICs in the concrete.

  • 24.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Enoksson, Ola
    Trafikverket.
    Höjsten, Tommy
    Trafikverket.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Numerical simulation of train-induced aerodynamic pressure on railway noise barriers2023In: XII International Conference on Structural Dynamics, Delft, Netherlands, July 2-5, 2023., 2023Conference paper (Refereed)
    Abstract [en]

    Noise barriers built parallel to the railway to reduce noise pollution, will be subjected to strong aerodynamic pressure from high-speed trains and have significant dynamic responses under such pressure. Based on computational fluid dynamics (CFD), a numerical simulation of train-induce aerodynamic pressure on noise barriers was performed. Time-varying pressure and its distribution along height direction of noise barriers were analysed, and the effect of different factors on results, i.e., the distance from noise barriers to track centre and the height of noise barrier, were discussed. Results show that the geometric changes in train nose and tail cause the obvious transient pressure pulse, and the pressure magnitude from nose is higher than that from tail. When the measuring height increases, the pressure gradually decreases, which can be well characterized by a height coefficient equation from Germany DB code. The pressure magnitude increases non-linearly when the distance to track centre decreases. Importantly, the height of noise barrier is also an important factor affecting pressure magnitude on noise barriers and when the height of noise barrier increases, the pressure magnitude gradually increases but tends to be stable at higher heights. An exponential equation can well characterize such effect of height of noise barrier on train-induced aerodynamic pressure.

  • 25.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mensah, Rhoda Afriyie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, 211189, China.
    Correlation between early- and later-age performance indices of early frost-damaged concrete2022In: IABSE Symposium Prague 2022: Challenges for Existing and Oncoming Structures - Report, International Association for Bridge and Structural Engineering / [ed] František Wald, Pavel Ryjáček, International Association for Bridge and Structural Engineering, 2022, p. 934-941Conference paper (Refereed)
    Abstract [en]

    Freeze‐thaw cycles can lead to serious damage of early‐age concrete and influence its behaviour at later ages. In this study, the later‐age compressive strength, resistance to chloride penetration and resistance to freeze‐thaw of early frost‐damaged concrete were experimentally studied and the relationship between its early‐ (i.e., strength and resistivity) and later‐age (i.e., strength, chloride ion electric flux and freeze‐thaw durability factor) performance indices were analysed. Results show that the later‐age performance of the concrete subjected to freeze‐thaw cycles at early age was generally worse than that of the control samples, which had not undergone early frost damage. This was especially significant for the concrete subjected to freeze‐thaw cycles before the age of 24 h. The compressive strength after early frost action had a higher linear correlation with the later‐age indices of the concrete than the compressive strength before early frost action. Results also showed that the early‐age resistivity is a good indicator for the later‐age performance of early frost‐damaged concrete if the pre‐curing time before frosting is at least 24 h. 

  • 26.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Modified calculation model of train-induced aerodynamic pressure on vertical noise barriers considering the train geometry effectManuscript (preprint) (Other academic)
  • 27.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Enoksson, Ola
    Trafikverket, Luleå, Sweden.
    Hojsten, Tommy
    Trafikverket, Luleå, Sweden.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, Nanjing, China.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Numerical Analysis of High-Speed Train Induced Aerodynamic Load on Noise Barrier Considering Wind Effect2023In: Building for the Future: Durable, Sustainable, Resilient - Proceedings of the fib Symposium 2023 - Volume 2 / [ed] Alper Ilki, Derya Çavunt, Yavuz Selim Çavunt, Springer, 2023, Vol. 2, p. 332-341Conference paper (Refereed)
    Abstract [en]

    Along the high-speed railway lines, the noise barriers need to be installed to protect nearby inhabitants from noise pollution caused by the running trains. When a high-speed train passes through the noise barriers, due to the blocking effect of noise barrier on air movement, transient train-induced aerodynamic pressure will increase significantly. Field measurement and computational fluid dynamics (CFD) simulation are main ways to study the train-induced aerodynamic pressure on the noise barriers. Due to the complexity of the environmental conditions in field test, however, it is difficult to take into account the wind effects on measurement results. Based on CFD simulation, in this paper, the aerodynamic effects on noise barrier from high-speed trains was simulated by applying the wind flow in the opposite direction to the train running. Influences of train speed and distance from noise barrier to track centre on such aerodynamic pressure were analysed. In addition, by applying the wind flow perpendicular to the longitudinal of train body, the effect of cross wind on the train-induced aerodynamic pressure was evaluated. Results show that pressure magnitude on the noise barriers increases non-linearly with the train speed. There is good nonlinear relationship between the pressure and the square of the distance to track centre. Cross wind increases the magnitude of positive pressure and makes the duration of high-pressure zone longer and absolute value of negative pressure peak decreases. There is a coupling effect of cross wind effect and train-induced aerodynamic effect on noise barriers. 

  • 28.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, P.R. China.
    Cao, Jie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, P.R. China.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    A review of concrete properties under the combined effect of fatigue and corrosion from a material perspective2023In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 369, article id 130489Article, review/survey (Refereed)
    Abstract [en]

    When in use, reinforced concrete bridge structures not only experience high-frequency fatigue loading caused by passing vehicles, but also suffer from the effects of a corrosive environment. In addition to fatigue damage to reinforcement, long-term fatigue loading also causes concrete cracking and deterioration of pore structures, thereby accelerating the ingress of external corrosive substances and reducing concrete durability. Long-term exposure to a corrosive environment also reduces the performance of concrete and causes corrosion of reinforcement materials, affecting the fatigue performance of the structure. Therefore, there is a combined effect between fatigue loads and corrosion on concrete. This paper is a review of the current literature from a material perspective on the performance degradation of concrete under the combined action of fatigue loading and corrosion, that is, carbonation, chloride ion attack, freeze–thaw cycles, and sulphate attack. The paper includes (1) a description of a test method for examining the combined action of fatigue loading and corrosion, (2) a summary of performance degradation of concrete under the combined effect of fatigue loading and corrosion, and (3) an introduction to durability deterioration models considering fatigue damage, and fatigue models that can account for corrosion. Finally, potential future research on concrete under the combined effect of fatigue loading and corrosion is described.

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  • 29.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189, Nanjing, PR China.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A review on aerodynamic load and dynamic behavior of railway noise barriers when high-speed trains pass2023In: Journal of Wind Engineering and Industrial Aerodynamics, ISSN 0167-6105, E-ISSN 1872-8197, Vol. 239, article id 105458Article in journal (Refereed)
    Abstract [en]

    Noise barriers need to be installed along high-speed railway lines to protect nearby inhabitants from the noise pollution caused by the running of high-speed trains (HSTs). The vertical noise barrier is the main structural type. However, when an HST passes through the noise barriers sited along the track, significant and transient aerodynamic pressure will act on the surface of the noise barriers, resulting in strong dynamic responses and even fatigue damage. Therefore, it is important to determine the train-induced aerodynamic load on the barrier surface and analyze the dynamic behaviors of the noise barriers under such a load for its structural design and to guarantee its safety and durability. This paper is a systematic review of the current literature on the aerodynamic load and dynamic behavior of vertical noise barriers; it includes (1) a summary and analysis of characteristics of such aerodynamic pressure and relevant influencing factors, (2) an introduction to measurement methods of aerodynamic load and relevant pressure models on the surface of noise barriers, and (3) a description of the dynamic response and fatigue analysis of noise barriers under such loads. Finally, potential further studies on this topic are discussed, and conclusions are drawn.

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    fulltext
  • 30.
    Liu, Dongyun
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, Nanjing, PR China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, Nanjing, PR China.
    Gonzalez-Libreros, Jaime
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ge, Yuanfei
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, Nanjing, PR China and.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, Nanjing, PR China; Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Time-depth dependent chloride diffusion coefficients of self-compacting concrete2023In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763XArticle in journal (Refereed)
  • 31.
    Min, Xinzhe
    et al.
    School of Civil Engineering and Architecture, Nanjing Institute of Technology, Nanjing, China.
    Zhang, Jiwen
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Li, Xing
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A nonlinear prediction model of the debonding process of an FRP-concrete interface under fatigue loading2023In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 369, article id 130583Article in journal (Refereed)
    Abstract [en]

    Externally bonded Fiber Reinforced Polymer (FRP) strengthening has been proven to be an efficient and reliable method for structural strengthening of reinforced concrete (RC) members. However, the beneficial effects of this method can be diminished due to the debonding of the FRP laminates. The mechanism of FRP debonding still requires further research, especially for strengthened members under fatigue loading. To understand and predict the FRP fatigue debonding process better, eleven FRP-concrete joint specimens were tested under static or fatigue loading. Both the theoretical derivation and the experimental study indicated that the debonding growth rate of the FRP laminate depended not only on the mean level (), but also the amplitude () of the applied fatigue load. In addition, the debonded portion of the FRP laminate had a significant impact on the following debonding process due to the friction and mechanical interaction between the debonded FRP and the concrete surface. Therefore, a new nonlinear prediction model is proposed in this paper. The proposed model explicitly took into account the amplitude and the mean level of the fatigue loading, which enabled the effect of both to be modelled. Meanwhile, a correction term was also introduced into the model to account for the influence of the previously debonded FRP laminate. The predicted results of the debonding growth rate and the debonding length agreed well with the experimental results.

  • 32.
    Min, Xinzhe
    et al.
    School of Civil Engineering and Architecture, Nanjing Institute of Technology, Nanjing, China.
    Zhang, Jiwen
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Li, Xing
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    An experimental study on fatigue debonding growth of RC beams strengthened with prestressed CFRP plates2022In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 273, article id 115081Article in journal (Refereed)
    Abstract [en]

    Externally bonded Fiber Reinforced Polymer (FRP) laminates are increasingly used to strengthen Reinforced Concrete (RC) members. However, FRP debonding remains a major drawback of this strengthening method. To better understand the mechanisms of FRP debonding, six RC beams strengthened with prestressed or non-prestressed Carbon Fiber Reinforced Polymer (CFRP) plates were subjected to static and fatigue loading. CFRP plate debonding was observed in both cases. However, the mechanism of debonding differed: under cyclical fatigue loading, debonding was initiated under both loading points simultaneously and propagated synchronously towards the nearest support whereas in static tests debonding began under a single loading point and progressed suddenly towards its adjacent support. The results also showed that stress redistribution induced coupling between accumulated fatigue damage in the steel reinforcement and fatigue debonding of the CFRP plate, accelerating the fatigue failure of the specimens.

  • 33.
    Min, Xinzhe
    et al.
    School of Civil Engineering and Architecture, Nanjing Institute of Technology, Nanjing, China.
    Zhang, Jiwen
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189, Nanjing, China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189, Nanjing, China.
    Li, Xing
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189, Nanjing, China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    A full-range fatigue life prediction model for RC beams strengthened with prestressed CFRP plates accounting for the impact of FRP debonding2024In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 301, article id 117305Article in journal (Refereed)
  • 34.
    Nilimaa, Jonny
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Häggström, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Trafikverket, Trafikverket, Luleå.
    Paulsson, Björn
    Trafikverket, UIC, Banverket.
    Extend the life of existing railway bridges: Results from EU FP7 project MAINLINE2015In: IABSE Conference Geneva 2015: Structural Engineering: Providing Solutions to Global Challenges, Geneva: International Association for Bridge and Structural Engineering, 2015, p. 1219-1226Conference paper (Other academic)
    Abstract [en]

    There is a need to extend the life and capacity of many existing bridges. One of the objects of the EU FP7 Project MAINLINE, 2011-2014, was to facilitate this. Guidelines for assessment and strengthening methods are presented as well as case studies in which existing bridges are studied in order to extend their life length. One example is the prestressing of the slab in a one-span concrete trough bridge in order to increase its load-carrying capacity. Horizontal holes were drilled trough the slab and in them steel bars were placed and post-tensioned. In this way a compressive stress was introduced into the concrete section so that it’s bending and shear capacity was increased.In another study a metal truss bridge was monitored in order to check strain and stress ranges in critical connections to enable an enhanced evaluation of the remaining fatigue resistance. The studied bridge was then replaced and loaded to failure to study its robustness and the reliability of applied assessment methods. The results could then be applied to prolong the life of an identical twin bridge located in the northern part of Sweden. A Life Cycle Assessment Tool (LCAT) has been developed to enable Infrastructure Managers to choose optimal maintenance strategies.

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  • 35.
    Qin, Xiao-Chuan
    et al.
    School of Civil Engineering, Southeast University.
    Meng, Shao-Ping
    School of Civil Engineering, Southeast University.
    Cao, Da-Fu
    School of Civil Science and Engineering, Yangzhou University.
    Tu, Yong-Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sabourova, Natalia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Evaluation of freeze-thaw damage on concrete material and prestressed concrete specimens2016In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 125, p. 892-904Article in journal (Refereed)
    Abstract [en]

    The pore structure of the hardened concrete and the microscopic changes of a few selected pores throughout the freeze-thaw test were investigated by a method combining RapidAir and digital metalloscope. Traditional tests were also performed to evaluate the macroscopic change caused by freeze-thaw cycles (FTCs). The investigation shows that the concrete material, of which the spacing factor is 0.405 mm and the air content is 2.38%, can still withstand more than 300 FTCs. Severe microscopic damages occurred after approximately 200 FTCs and the freeze-thaw damage were gradually aggravated afterwards. Prestress forces have a remarkable impact on the failure pattern under FTCs. It was further found that the compressive strength as an indicator is more reliable than the relative dynamic modulus of elasticity in evaluating the freeze-thaw damage on concrete material. In addition, the test and analysis show that the measured prestress losses of bonded specimen are larger than that of unbounded specimen under the attack of FTCs due to the duct grouting effect. The ultimate freeze-thaw prestress loss is about 5% of σconσcon for both the bonded and unbonded specimens because the grouting cement paste will eventually be completely destroyed.

  • 36.
    Sabourova, Natalia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Duvnjak, I.
    University of Zagreb, Zagreb, Croatia..
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Damjanovic, D.
    University of Zagreb, Zagreb, Croatia..
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, China.
    Popescu, Cosmin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Detection of sparse damages in plates2020In: IABSE Symposium, Wroclaw 2020: Synergy of Culture and Civil Engineering – History and Challenges / [ed] Jan Bień, Jan Biliszczuk, Paweł Hawryszków, Maciej Hildebrand, Marta Knawa-Hawryszków, Krzysztof Sadowski, Zürich: International Association For Bridge And Structural Engineering (IABSE) , 2020, p. 1141-1148Conference paper (Refereed)
    Abstract [en]

    Structural damage is often a spatially sparse phenomenon, i.e. it occurs only in a small part of the structure. This property of damage has not been utilized in the field of structural damage identification until quite recently, when the sparsity-based regularization developed in compressed sensing problems found its application in this field. In this paper we consider classical sensitivity-based finite element model updating combined with a regularization technique appropriate for the expected type of sparse damage. The validity of the proposed methods is demonstrated using simulations on a bridge. The pros and cons of these methods are discussed.

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    Sabourova
  • 37.
    Sabourova, Natalia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Puurula, Arto
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Carolin, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Thun, Håkan
    The railway concrete arch bridge over Kalix river: dynamic properties and load carrying capacity2012In: Concrete Structures for Sustainable Community: proceedings of the International FIB Symposium 2012, Stockholm, Sweden, 11 - 14 June 2012 / [ed] Dirch H Bager; Johan Silfwerbrand, Stockholm: Swedish Concrete Association , 2012, p. 609-612Conference paper (Refereed)
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    FULLTEXT01
  • 38.
    Sabourova, Natalia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, Nanjing, China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Southeast University, Nanjing, China.
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Boden Kommun.
    Blanksvärd, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ohlsson, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Railway Concrete Arch Bridge over Kalix River at Långforsen: Dynamic Properties and Load-Carrying Capacity2019Report (Refereed)
    Abstract [en]

    The concrete arch bridge over Kalix River at Långforsen was built in 1960 and has a mid-span of 89,5 m and a height of 13,7 m. The bridge owner, Trafikverket, wanted to increase its allowable axle load from 225 to 300 kN. Field tests were carried out under service condition and with ambient vibrations. The test results were used to update and validate Finite Element Models. At last, the refined models were used to check the possibility to increase the axle load.

    According to earlier assessments, most parts of the bridge is capable of carrying an axle load of 330 kN. The only critical sections are located in the beams carrying the rail on top of the arch in the section where the beams are united with the arch. Here the stresses in the longitudinal bottom reinforcement are slightly too high.

    These sections have been studied in a FEM model for different loads and results show maximum strains of about 50·10-6 corresponding to stresses of only about 10 MPa in the reinforcement in the critical sections. Live load vertical deflections of the crown of the arch is of the order of only ± 6 mm. Dynamic studies have also been made showing that fatigue is no issue. Altogether the studies show that the bridge is able to carry an increased axle load of 300 kN without problems.

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    App A Drawings
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    App B Design calculations
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    App C Photos construction
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    App D Assessment 2002-04
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    App E Measurements
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    App F FEM
  • 39.
    Shi, Pan
    et al.
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast Univ., Nanjing 211189, PR China.
    Lin, Yuxuan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast Univ., Nanjing 211189, PR China.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast Univ., Nanjing 211189, PR China.
    Fang, Mengxiang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast Univ., Nanjing 211189, PR China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast Univ., Nanjing 211189, PR China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Stiftelsen for industriell og teknisk forskning (Norwegian) (SINTEF Narvik AS), Rombasveien 47, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shock Wave-Induced Dynamic Mechanical Behavior of Calcium Silicate Aluminate Hydrate at the Molecular Scale2023In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 35, no 8, article id 04023232Article in journal (Refereed)
  • 40.
    Song, Shoutan
    et al.
    School of Civil Engineering, Southeast University, 211189, Nanjing, PR China. National Prestress Engineering Research Center, Southeast University, 211189, Nanjing, PR China.
    Wang, Guan
    China Construction Infrastructure Co., Ltd., 100044, Beijing, PR China.
    Min, Xinzhe
    School of Civil Engineering, Southeast University, 211189, Nanjing, PR China.
    Duan, Ning
    School of Civil Engineering, Southeast University, 211189, Nanjing, PR China.
    Tu, Yongming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, 211189, Nanjing, PR China. National Prestress Engineering Research Center, Southeast University, 211189, Nanjing, PR China.
    Experimental study on cyclic response of concrete frames reinforced by Steel-CFRP hybrid reinforcement2021In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 34, article id 101937Article in journal (Refereed)
    Abstract [en]

    A novel section with Steel-carbon fiber reinforced polymer (CFRP) hybrid reinforcement is introduced. CFRP longitudinal reinforcements are placed in the outer layer of the section, while steel reinforcements are arranged in the inner layer. The new type section is utilized to reduce the residual deformation of anti-seismic structures and improve the durability of structures. Cyclic loading tests are conducted on the four concrete frame structure with an axial compression ratio of 0.31. Seismic performances of concrete frames with steel reinforcements, steel-CFRP hybrid reinforcements and CFRP reinforcements are compared and studied. The major objectives of study are focus on the performance of CFRP reinforcements under the axial compression ratio of 0.31 and the ductility, energy dissipation, strength degradation, unloading stiffness, residual deformation of the frame structure with different reinforcement modes. Test results showed that as compared with the steel reinforced concrete frame, Steel-CFRP hybrid reinforced concrete frame exhibited excellent post-earthquake repairabilities, comparable hysteretic energy dissipation abilities and reasonable strength degradation. Furthermore, when the axial compression ratio is 0.31, the ultimate tensile strength of CFRP reinforcements calculated in accordance with the bearing capacity is 27.2%-32% of the static ultimate tensile strength. The concrete frame with ideal mechanical properties can be obtained by reasonable allocation of steel and CFRP reinforcement.

  • 41.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, 211189 Nanjing, PR China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189 Nanjing, PR China.
    Cao, Jie
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wen, Rongjia
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Shi, Pan
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Yuan, Lei
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Ji, Yuanhui
    School of Chemistry and Chemical Engineering, Southeast University, 211189 Nanjing, PR China.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular dynamics simulation study of the transport of pairwise coupled ions confined in C-S-H gel nanopores2022In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 318, article id 126172Article in journal (Refereed)
    Abstract [en]

    Ions that penetrate concrete micropores have a significant influence on concrete’s properties. Studying the microscopic interaction mechanisms between ions and concrete materials allows the discovery of factors that significantly affect concrete properties from a new perspective. In this study, molecular dynamics techniques were used to simulate the transport processes of different ionic compounds (Na2SO4, NaCl and NaNO2) in C-S-H gel nanopores in a pairwise coupled way, so that a detailed investigation into how these ions interact with each other and how they affect C-S-H gel could be carried out. It was found that for anions entering the C-S-H gel nanopores, the order of transport rate is SO42->Cl->NO2. Furthermore, the SO4-Na ion pair greatly affects the transport rate of solution due to its strong binding stability. Additionally, this study found that the presence of sulfate ions changed the transport characteristics of nitrite ions, such that nitrite ions aggregated into clusters more easily, thereby disrupting the compatibility between nitrite ions and water molecules. As a result, the presence of sulfate ions reduced the rustproofing effect of nitrite ions.

  • 42.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Fang, MengXiang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Guo, Tong
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Wang, Tongfang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Yuan, Lei
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Shi, Pan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, National Engineering Research Center for Prestressing Technology, School of Civil Engineering, Southeast University, 211189 Nanjing, China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shock-induced reactive molecular dynamics simulation in sodium aluminosilicate hydrate: Wave propagation, mechanical response, and structural deformation2023In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 612, article id 122350Article in journal (Refereed)
    Abstract [en]

    Sodium aluminosilicate hydrate (N-A-S-H) gels have gained attention due to their potential use as components of geopolymers to improve structural and mechanical properties. In this study, we investigated the propagation of shock waves in N-A-S-H gels subjected to impact velocities (Up) ranging from 0.1 to 3.0 km/s, as well as the resulting mechanical responses and structural deformations. Our results showed that when Up<0.4 km/s, only one elastic wave existed, and the Hugoniot elastic limit was estimated to be 4.1 GPa. Above this limit, a two-wave structure formed. The elastic and elastoplastic deformation mechanisms involved initial compaction and densification of the N-A-S-H gel structure, followed by bond angle bending. The Hugoniot Us-Up relationship was found to be linear in the elastoplastic region, with a linear parameter λ of approximately 2.75. These new atomistic insights into the shock compression of N-A-S-H gels will provide valuable guidance for future studies.

  • 43.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, 211189 Nanjing, PR China. National Engineering Research Center for Prestressing Technology, Southeast University, 211189 Nanjing, PR China.
    Liu, Dongyun
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wang, Tongfang
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Yuan, Lei
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Evaluation on later-age performance of concrete subjected to early-age freeze–thaw damage2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 270, article id 121491Article in journal (Refereed)
    Abstract [en]

    This research studies the influences of pre-curing time, the number and environment of early-age freeze–thaw damage (E-FTD) and later-age curing methods on later-age performance of concrete subjected to E-FTD. The concrete specimens with pre-curing time of 18 h, 24 h, 48 h and 72 h were subjected to four different E-FTD systems. Subsequently, three later-age curing methods were performed to the time of 28 days respectively and finally the later-age compressive strength, resistance to chloride penetration and freeze–thaw of concrete were evaluated. The results show that all three later-age performance indexes improve gradually as the pre-curing time prolongs. The damage of the salt freeze–thaw environment to early-age concrete is severer than that of the water freeze–thaw environment, resulting in the unsatisfactory later-age performance even with restorative curing. Among all later-age curing methods, the restoration effect of water curing on later-age performance is the best. Compared to the standard curing, the restoration effect of natural air curing on later-age compressive strength and resistance to chloride penetration of concrete is better, but that on resistance to freeze–thaw is worse. For the concrete with shorter pre-curing time, the recovery percentage of durability indexes, especially the resistance to freeze–thaw, is always lower than that of compressive strength. The pre-curing time should be prolonged appropriately for the early-age freeze–thaw damaged concrete with the requirement of durability.

  • 44.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, and National Engineering Research Centre for Prestressing Technology, Southeast University, 211189, Nanjing, P.R. China.
    Liu, Dongyun
    School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Yuan, Lei
    School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Wang, Tongfang
    School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Early Hydration Process and Kinetics of Concrete Based on Resistivity Measurement2021In: Journal of Advanced Concrete Technology, ISSN 1346-8014, Vol. 19, no 3, p. 196-206Article in journal (Refereed)
    Abstract [en]

    The resistivity of fresh concrete was obtained for the period from casting to the age of 72 h by a non-contact electrical resistivity measurement. Early hydration process of three types of concrete with the ratio of water to binder in mass of 0.4, including ordinary Portland cement concrete (OPC), concrete with fly ash of 30% (FAC) and concrete with silica fume of 5% (SFC), were analysed and compared. Based on resistivity data and Krstulovic-Dabic model, parameters of kinetics model were obtained, and hydration kinetics process was characterized. Results show that early hydration process of concrete can be characterized by the development of resistivity. Early hydration process is divided into five stages, which are ion dissolution, induction, acceleration, transition and deceleration. Incorporation of fly ash reduces the peak of hydration rate and delays the second hydration acceleration, whereas addition of 5% of silica fume has little effect on the early hydration of concrete. The compressive strength and electrical resistivity of three types of concrete show a good linear correlation at early age. The parameters of Krstulovic-Dabic kinetic model can be fitted well by using resistivity data of concrete.

  • 45.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, Nanjing, P.R. China; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P.R. China.
    Liu, Dongyun
    School of Civil Engineering, Southeast University, Nanjing, P.R. China.
    Yuan, Lei
    School of Civil Engineering, Southeast University, Nanjing, P.R. China.
    Zhang, Yu
    School of Civil Engineering, Southeast University, Nanjing, P.R. China.
    Corrosion resistance of concrete strengthened with fibre-reinforced polymer sheets2022In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 74, no 2, p. 54-69Article in journal (Refereed)
    Abstract [en]

    The corrosion resistance of concrete strengthened with three types of fibre-reinforced polymer (FRP) sheets (unidirectional carbon-FRP (CFRP), unidirectional basalt-FRP (BFRP) and bidirectional BFRP) was evaluated under chloride attack and the combined attack of chloride and ultraviolet radiation. After different corrosion durations, powder samples were collected from various depths of the concrete specimens to measure the total chloride ion concentrations (CICs). Scanning electron microscopy (SEM) was conducted to analyse the microscale morphology changes of the concrete surface layer, FRP fibre layer and resin matrix layer before and after combined attack. The results showed that all three types of FRP sheet provided significant chloride ion resistance, with the barrier effect of CFRP being better than that of BFRP under the same conditions. The total CIC of the FRP-strengthened concretes was higher under the combined attack than under chloride attack alone. The SEM observations showed that the resin matrix and fibre filaments of the FRP layer under combined attack were damaged, resulting in an increase in the permeability of the FRP-strengthened concretes. Finally, a time-varying model of CIC inside the FRP-strengthened concrete under chloride attack was established.

  • 46.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P. R. China ; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P. R. China.
    Shi, Pan
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P. R. China ; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P. R. China.
    Liu, Dongyun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Wen, Rongjia
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P. R. China.
    Yu, Qian
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P. R. China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway .
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Mechanical properties of calcium silicate hydrate under uniaxial and biaxial strain conditions: a molecular dynamics study2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 2, p. 1156-1166Article in journal (Refereed)
    Abstract [en]

    Calcium silicate hydrate (C-S-H) is the main hydration product of cementitious materials, often experiencing complex stress conditions in practical applications. Therefore, reactive molecular dynamics methods were used to investigate the mechanical response of the atomistic structure of C-S-H under various uniaxial and biaxial strain conditions. The results of uniaxial simulations show that C-S-H exhibits mechanical anisotropy and tension–compression asymmetry due to its layered atomistic structure. By fitting the stress–strain data, a stress–strain relationship that accurately represents the elastoplasticity of C-S-H was developed. The biaxial yield surface obtained from biaxial simulations was ellipsoidal, again reflecting the anisotropy and asymmetry of C-S-H. Four yield criteria (von Mises, Drucker–Prager, Hill, and Liu–Huang–Stout) were further investigated, and it was found that the Liu–Huang–Stout criterion can effectively capture all the major features of the yield surface. During a uniaxial tensile process in the z direction, multi-crack propagation was observed, which was aggravated and weakened by y direction tensile and compressive strains respectively. The results of chemical bond analyses revealed that, for different strain conditions, the CaW–OS and CaS–OS bonds play different roles in resisting deformation.

  • 47.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P.R. China; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P.R. China.
    Wang, Tongfang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P.R. China; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P.R. China.
    Wen, Rongjia
    College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, P.R. China.
    Cao, Jie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Fang, Mengxiang
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, P.R. China; National Engineering Research Center for Prestressing Technology, Southeast University, Nanjing, P.R. China.
    Wang, Chao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular dynamics study on the adsorption of radioactive ions by geopolymers2023In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605Article in journal (Refereed)
    Abstract [en]

    The construction of nuclear power plants necessitates careful consideration of the discharge and fixation of nuclear waste. Geopolymers are new cement-based materials (CBMs) with three-dimensional cage-like structures that enable effective nuclear waste fixation. In this work, the adsorption of radioactive caesium and strontium ions by sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymers, was investigated using molecular dynamics simulations to obtain nanoscale insights into the ions' interactions with the gel. The formation of strong ion-oxygen bonds allowed both ions to be effectively adsorbed on the NASH surface, but the adsorption ratio of strontium ions (17.2%) was slightly lower than that of caesium ions (21.0%). Because strontium ions are divalent, they can form stronger electrostatic interactions with water molecules and chloride ions, which hinders their approach to the interface. For the same reason, the diffusion coefficient of strontium ions in solution is lower than that of caesium ions. These results provide new insights into the nuclear waste fixation capacity of NASH gel and guidance for the design of new CBMs for radioactive waste disposal.

  • 48.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, 211189 Nanjing, PR China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189 Nanjing, PR China.
    Wen, Rongjia
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Yu, Qian
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Cao, Jie
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Ji, Yuanhui
    School of Chemistry and Chemical Engineering, Southeast University, 211189, Nanjing, PR China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular dynamics study on coupled ion transport in aluminum-doped cement-based materials2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 295, article id 123645Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations were performed to investigate coupled ion transport in the two main hydration products of aluminum-doped cement-based materials, including calcium aluminate-silicate hydrate (C-A-S-H) gel and calcium hydroxide (CH). Each material was simulated in three solutions (1 mol/L NaCl, 0.5 mol/L NaCl + 0.5 mol/L Na2SO4, and 1 mol/L Na2SO4). Sulfate ions were found to promote the aggregation of other ions in solution to form ion clusters that block the materials’ nanopores to some degree, slowing their erosion. The magnitude of this reduction is significantly greater for the C-A-S-H than for CH because the ion clusters in the C-A-S-H gel are adsorbed at the interface where they cause “necking”, whereas in CH they move with the solution and are not adsorbed at the material’s surface. Sodium ions adsorb more strongly to C-A-S-H gels than chloride ions, but the opposite is true for CH. The two hydration products thus have markedly different effects on ions transport.

  • 49.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. School of Civil Engineering, Southeast University, 211189 Nanjing, PR China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189 Nanjing, PR China.
    Yu, Qian
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Wen, Rongjia
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Shi, Pan
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Yuan, Lei
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Ji, Yuanhui
    School of Civil Engineering, Southeast University, 211189 Nanjing, PR China.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular dynamics simulation of coupled water and ion adsorption in the nano-pores of a realistic calcium-silicate-hydrate gel2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 299, article id 123961Article in journal (Refereed)
    Abstract [en]

    The adsorption behavior of water and ions at the surfaces of porous calcium-silicate-hydrate (C-S-H) gels affects the durability of concrete. This paper presents the results of molecular dynamics simulations performed using the Clay Force Field that were conducted to investigate the local structure, adsorption behavior, and dynamic properties of water and ions in the pores of C-S-H gels. A realistic C-S-H gel channel model was constructed and simulated with three mixed salt solutions (NaCl + Na2SO4, NaCl + Na2CO3, and Na2SO4 + Na2CO3) in the pores. The realistic C-S-H gel surface was found to be hydrophilic, causing water molecules to adopt an orderly arrangement near the substrate surface. This hydrophilicity is due to defective silicon chains in the substrate that provide large numbers of hydrogen bonding sites for surface water molecules. Additionally, calcium atoms near the surface attract water molecules to form hydration layers. The adsorption of cations near the substrate correlated negatively with the strengths of the ionic clusters formed by the dissolved anions and cations. As a result, the adsorption of sodium ion was strongest for the NaCl + Na2SO4 solution and weakest for the Na2SO4 + Na2CO3 solution. There were also clear differences in the adsorption behaviors of the anions. Chloride adsorption was mainly driven by ion pairing with calcium atoms near the surface, while sulfate adsorption was mainly due to ion pairing with surface-adsorbed sodium ions. Conversely, carbonate ions exhibited weaker surface adsorption because of their tendency to form ionic clusters in solution. These insights into the adsorption behaviors of common ions near a realistic C-S-H gel surface will be useful in future efforts to develop modified cement-based materials with improved properties.

  • 50.
    Tu, Yongming
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China; National Engineering Research Center for Prestressing Technology, Southeast University, 211189, Nanjing, P.R. China.
    Yuan, Lei
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Liu, Dongyun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Cao, Jie
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Ding, Yihui
    Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, School of Civil Engineering, Southeast University, 211189, Nanjing, P.R. China.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. SINTEF Narvik AS, Narvik 8517, Norway.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Molecular Dynamics Simulations of Chloride and Sulfate Ion Transport in C-S-H gel and γ-FeOOH Nanopores2022In: JOURNAL OF ADVANCED CONCRETE TECHNOLOGY, ISSN 1346-8014, Vol. 20, no 12, p. 720-731Article in journal (Refereed)
    Abstract [en]

    Interactions between Cl-, SO42-and cementitious materials, reinforcement passive films influence the durability of rein-forced concrete structures. Transport of three solutions (NaCl, Na2SO4, mixed) in calcium silicate hydrate (C-S-H) gel, gamma- FeOOH nanopores was investigated using molecular dynamics. Solution transport in gamma-FeOOH nanopores is slower than in C-S-H gel nanopores because of the lesser hydrophilicity of gamma-FeOOH surface. SO42-can form ion clusters to hinder the solution transport and atomic motion, and the ion clusters appear in the solution more frequently than at the interface. Temporary adsorption of Cl-, SO42-on substrate surfaces occurs during transport because of Ca-Cl, Ca-SO4 ionic bonds on the C-S-H surface and Ho (hydroxyl hydrogen atoms)-Cl, Ho-SO4 hydrogen bonds on the gamma-FeOOH surface, and these bonds are influenced by the local structure. Two substrates interact with water, Cl-, SO42-via distinct microscopic mechanisms.

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