Change search
Refine search result
12 1 - 50 of 57
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Experimental Evaluation of Influence of Member Thickness, Anchor-Head Size, and Orthogonal Surface Reinforcement on the Tensile Capacity of Headed Anchors in Uncracked Concrete2018In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 144, no 4, article id 04018012Article in journal (Refereed)
    Abstract [en]

    Cast-in-place headed anchors with different head sizes embedded in plain and reinforced concrete members of various thicknesses were subjected to pullout tests. The influence of member thickness, size of the anchor head, and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts was evaluated. The member thickness varied from 1.5 to 3.0 times the anchor embedment depth and headed anchors with small, medium, and large heads were tested.

    The experimental results of the present study showed that increasing member thickness and/or the use of orthogonal surface reinforcement lead to increased anchorage capacity and anchorage ductility, whereas the anchorage stiffness decreases slightly. In contrast to the anchorage ductility, the tensile breakout resistance and the anchorage stiffness increase significantly with increasing size of the anchor head.

    The experimental results corresponded closely to numerical results from a previous study (Nilforoush et al. 2016 a & b), which suggested a modified model incorporating several modification factors for improving the predictive capability of the Concrete Capacity (CC) method. In the present study, these factors yielded improved prediction of the tensile breakout capacity of the tested headed anchors.

  • 2.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. College of engineering, University of Mosul, Iraq.
    Jonasson, Jan-Erik
    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.
    Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks2018In: European Journal of Environmental and Civil Engineering, ISSN 1964-8189, E-ISSN 2116-7214, Vol. 22, no 2, p. 226-245Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurately predicting the risk of early thermal and shrinkage cracking in concrete structures. The stress in young concrete is affected by changes in its dimensions during hydration and the restraint imposed by adjoining structures. In concrete culverts, the restraints from existing structures acting upon the first and second casting sections to be cast are different, causing them to exhibit different early cracking behaviour. This work presents a new method for predicting restraint in complex concrete structures using artificial neural networks (ANNs). Finite element calculations were performed to predict restraint in 108 slabs, 324 walls and 972 roofs from second sections of concrete culverts, and the results obtained were used to train and validate ANN models. The ANN models were then used to study the effects of varying selected parameters (the thickness and width of the roof and slab, the thickness and height of the walls, and the length of the culvert section) on the predicted restraint. Mathematical expressions for predicting restraint values in slabs, walls and roofs were derived based on the ANN models’ output and implemented in an Excel spreadsheet that provides a simple way of predicting restraint in practical applications. Restraint values predicted in this way agree well with the results of finite-element calculations

  • 3.
    Elfgren, Lennart
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilforoush, Rasoul
    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.
    Assessment of Fasteners to Concrete: A Tribute to Rolf Eligehausen2017In: Connections between Steel and Concrete: 3rd International Symposium / [ed] Akanshu Sharma and Jan Hofmann, Stuttgart, 2017, p. 1294-1302Conference paper (Refereed)
    Abstract [en]

    Some examples are given of assessment of fastenings to concrete structures and the work started by Rolf Eligehausen in fib Task Group 2.9 “Fastenings to structural concrete and masonry”. Studies have been made on e.g. the influence of creep on adhesive anchors and of surface reinforcement and size effects on headed anchors.

  • 4.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Experimental evaluation of tensile behaviour of single cast-in-place anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete2017In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 147, p. 195-206Article in journal (Refereed)
    Abstract [en]

    Cast-in-place anchor bolts embedded in plain and steel fibre-reinforced normal- and high-strength concrete members were subjected to monotonic tensile loads. The influence of the concrete member thickness, concrete strength, and the addition of steel fibres to the concrete mixture, on the anchorage capacity and performance was evaluated. The experimental results were evaluated in terms of anchorage capacity, anchorage ductility and stiffness as well as failure mode and geometry. Furthermore, the validity of Concrete Capacity (CC) method for predicting the tensile breakout capacity of anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete members was evaluated.

    The anchorage capacity and ductility increased slightly with increasing member thickness, whereas the anchorage stiffness decreased slightly. In contrast to the anchorage ductility, the anchorage capacity and stiffness increased considerably with increasing concrete compressive strength. The anchorage capacity and ductility also increased significantly with the addition of steel fibres to the concrete mixtures. This enhanced capacity and ductility resulted from the improved flexural tensile strength and post-peak cracking behavior of steel fibre-reinforced concrete.

    The average ratio of measured strengths to those predicted by the CC method for anchors in plain concrete members was increased from 1.0 to 1.17 with increasing member thickness. In steel fibre-reinforced concrete, this ratio varied from 1.29 to 1.51, depending on the member thickness and the concrete strength.

  • 5.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ožbolt, Joško
    University of Stuttgart .
    Hofmann, Jan
    University of Stuttgart .
    Eligehausen, Rolf
    University of Stuttgart .
    Influence of Surface Reinforcement, Member thickness and Cracked Concrete on Tensile Capacity of Anchor Bolts2017In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 114, no 6, p. 1543-1556Article in journal (Refereed)
    Abstract [en]

    An extensive numerical study was carried out to evaluate the influence of concrete member thickness and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts in uncracked concrete members. Anchor bolts at various embedment depths (hef=50 to 300 mm (1.97 to 11.81 in.)) in unreinforced and reinforced concrete members of various thicknesses (H=1.5 – 5.0∙hef) were simulated. The reinforced concrete slabs were considered to be lightly-reinforced and over-reinforced to evaluate also the influence of amount of reinforcement. Furthermore, the behavior of anchor bolts at various embedment depths in pre-cracked reinforced concrete members was numerically investigated. The numerical results were compared with predictions from current design models including the Concrete Capacity (CC) method.

    The numerical results show that in uncracked concrete the tensile capacity of anchor bolts increases up to 20% and the anchorage behavior becomes more ductile with increasing member thickness or by having surface reinforcement. The numerical results also show that the CC method underestimates the tensile capacity of deep anchors (hef≥200 mm (7.87 in.)), while it slightly overestimates the capacity of short anchors (hef≤100 mm (3.94 in.)) in thin unreinforced members. It was also found that the over-reinforced concrete does not improve the anchorage capacity and performance any further than the lightly-reinforced concrete. Based on the numerical results, several recommendations are proposed to account for the influence of member thickness, surface reinforcement and cracked concrete. Further experimental studies are ongoing to verify and generalize the recommendations of this study.

  • 6.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Numerical and Experimental Evaluations of Influence of Member Thickness, Anchor Head Size, and Surface Reinforcement on Tensile Breakout Capacity of Anchor bolts2017In: Connections between Steel and Concrete / [ed] Akanshu Sharma, Jan Hofmann, Stuttgart, 2017, p. 752-764Conference paper (Refereed)
    Abstract [en]

    The influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of cast-in-place headed anchors in uncracked concrete was studied both numerically and experimentally. The aim of this paper is to form a background for developing improved methods for the design of new fastenings as well as the assessment of current anchorages in practice. For this purpose, anchor bolts at various embedment depths (hef=50–500 mm) were simulated in plain and reinforced concrete members of various thicknesses (H=1.5–5.0∙hef). Three different head sizes of anchor bolts (i.e. small, medium and large) were also considered at each anchor embedment depth. Furthermore, to verify the numerical findings, a series of anchor pullout tests were carried out at which the testing parameters were similar to those in the numerical study.

    Numerical and experimental results show that the tensile breakout capacity of anchor bolts increases by increasing the member thickness or if surface reinforcement is present. The anchorage capacity further increases with increasing the anchor head size. The anchorage behavior becomes ductile by increasing member thickness or by having surface reinforcement, whereas it becomes stiff and more brittle by increasing the size of anchor head. To account for the influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of headed anchors, the CC method was modified and extended by incorporating three modification factors.

  • 7.
    Nilforoush, Rasoul
    et al.
    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.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sustained load performance of adhesive fastening systems in concrete2017In: Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure / [ed] Jaap Bakker; Dan M Frangopol; Klaas van Breugel, Leiden: CRC Press/Balkema , 2017, p. 2365-2371Conference paper (Refereed)
    Abstract [en]

    Influence of several sustained loading levels and various in-service conditions on the long-term performance of adhesive bonded anchors are experimentally evaluated. Adhesive bonded anchors with 16 and 20 mm diameters were subjected to sustained load levels between approximately 23 and 70% of their mean ultimate short-term capacities. The creep deformation of tested adhesive anchors was monitored over approximately 28 years. The tested in-service conditions were indoor, outdoor, wetness (i.e. water on the surface of concrete) and presence in the concrete of salt additives. The tested adhesive anchors in the indoor conditions could carry sustained loads up to 47% of their mean ultimate short-term capacities. However, the adhesive anchors under outdoor environment showed larger creep deformations and failure occurred for anchors subjected to sustained loads higher than 23% of the anchors’ mean ultimate short-time capacities. Wet condition seemed to have no adverse effect on the anchors’ creep behavior, but caused corrosion of the steel in the anchors over time. Salt additives in concrete had negligible influence on the long-term performance and creep deformation of the tested adhesive anchors

  • 8.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Tensile breakout capacity of cast-in-place headed anchors in concrete2017In: XXIIIth Symposium on Nordic Concrete Research & Developement / [ed] Marianne Tange Hasholt, Oslo, Norway, 2017, p. 235-238Conference paper (Refereed)
    Abstract [en]

    The influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of cast-in-place headed anchors was studied both numerically and experimentally. The aim of this paper is to form a background for developing improved methods for the design of new fastening systems as well as the assessment of the current anchorage systems in practice. Numerical and experimental results showed that the tensile breakout capacity of anchor bolts increases by increasing the member thickness or if surface reinforcement is present. Furthermore, the anchorage capacity increases with increasing the anchor head size.

  • 9.
    Nilforoush, Rasoul
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Ožbolt, Joško
    University of Stuttgart .
    Hofmann, Jan
    University of Stuttgart .
    Eligehausen, Rolf
    University of Stuttgart .
    Tensile capacity of anchor bolts in uncracked concrete: Influence of member thickness and anchor’s head size2017In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 114, no 6, p. 1519-1530Article in journal (Refereed)
    Abstract [en]

    This study evaluated the influence of concrete member thickness and size of anchor head on the tensile capacity and performance of anchor bolts in concrete. Anchor bolts at various embedment depths (hef=50 – 500 mm (1.97 – 19.69 in.)) in concrete members of various thicknesses (H=1.5 – 5.0∙hef) were simulated. Three different sizes of anchor head (small, medium and large) were considered at each anchor embedment depth. The numerical results were compared with predictions from several theoretical and empirical models, including current design models, as well as some test results.

    The numerical results show that the concrete cone resistance increases with increasing thickness of concrete member and/or size of the anchor head. Simulations also indicate that current design models generally underestimate the tensile capacity of large anchors.

    Two modification factors are proposed to account for the influence of the member thickness and the size of anchor head. Predictions of anchorage capacity using the proposed modification factors have good correlation with the available test results found in the literature.

  • 10.
    Hösthagen, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. anders.hosthagen@ltu.se.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Emborg, Mats
    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.
    Thermal Crack Risk Estimations of Concrete Walls: Temperature and Strain Measurements Correlated to the Equivalent Restraint Method2017In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper (Refereed)
    Abstract [en]

     Self-induced non-elastic deformations in hardening concrete, caused by restrained volume changes due to thermal dilatation and moisture deformations, often leads to cracking. In crack risk analyses, determination of the degree of restraint is vital. One model to estimate the restraint and calculate the thermal crack risk is the Equivalent Restraint Method, ERM. The method has previously been analyzed but needs to be further examined and validated. Recordings of tunnel sections were performed and compared to calculated values by ERM. Satisfying correlation between theoretically estimated and observed temperatures, strains and time of through cracking was achieve which is promising for future implementation and testing of the method.

  • 11.
    Nilsson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Edelbro, Catrin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edström, Kristina
    Kungliga tekniska högskolan, KTH.
    Adapting CDIO to Civil Engineering: Investigate - Plan - Desig - Construct - Operate and Maintain2016In: The 12th International CDIO Conference: Proceedings – Full papers / [ed] Jerker Björkqvist; Kristina Edström; Ronald J. Hugo; Juha Kontio; Janne Roslöf; Rick Sellens; Seppo Virtanen, Turku, 2016, p. 164-172Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to propose an alternative expression for engineering practice in thecontext of the civil engineering and built environment sector. Our first objective is todemonstrate that the CDIO approach can, with these modifications, be applied in developingcivil engineering and built environment programs. Our second objective is to showcase theadaptability of the CDIO approach, thereby encouraging other thoughtful modifications andtransformations. We outline the ideas underpinning the original expression, and identify therole it plays in the CDIO methodology for curriculum development. Taking these factors intoaccount, a modified expression is proposed to describe the engineering process in civilengineering and built environment. We divide the process into ‘investigation – planning –design – construction – operation and management’. Further, to ‘products, processes andsystems’, we propose the addition of ‘environments’.

  • 12.
    Nilforoush, Rasoul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. 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 Construction Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Söderlind, Gunnar
    SP Technical Research Institute of Sweden, Borås.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Long-Term Performance of Adhesive Bonded Anchors2016In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 113, no 2, p. 251-261, article id MS No. S-2014-302.R2Article in journal (Refereed)
    Abstract [en]

    Post-installed adhesive anchors used for fastening nonstructural and/or structural elements to concrete structures are prone to creep under sustained loads over their service life, which may considerably affect their long-term performance. In this study, the influence of various in-service conditions and sustained loading levels on the long-term performance of adhesive anchors was experimentally examined. The tested adhesive was an unsaturated polyester resin and the bonded anchors were subjected to sustained loads of 23, 47 and 70% of their mean ultimate short-term capacities for up to 10376 days (28.4 years). The tested in-service conditions were indoor temperature, outdoor temperature and humidity variations, wetness and presence in the concrete of salt additives.Results indicate that the tested bonded anchors did not fail indoors when subjected to sustained loads up to 47% of their mean ultimate short-time capacity. However, the long-term performance was substantially impaired outdoors, presumably due to temperature and humidity variations, leading to failure for sustained loads higher than 23% of the anchors’ mean ultimate short-time capacity.

  • 13.
    Nilforoush, Rasoul
    et al.
    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.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Numerical Modelling and Experimental Verification of Pullout Loading of Anchor Bolts in Reinforced Concrete Structures2016In: 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. 2172-2178Conference paper (Refereed)
    Abstract [en]

    The aim of this study is to provide a numerical model which can realistically present the failure load and failure mechanism of pullout loaded anchor bolts (headed studs) in reinforced concrete structures. The numerical analysis is carried out through a three-dimensional finite element (FE) code based on the Microplane constitutive law. The intension is to calibrate the FE model and to verify the numerical results against available test results. The calibrated FE model is intended to be used for an ongoing study to evaluate the influence of member thickness, surface reinforcement and size of anchor head on the tensile capacity and performance of anchor bolts.

    The simulation results showed very good agreements with the available test results. The objectivity of numerical modelling in respect to the size of finite elements as well as the defined boundary conditions was confirmed by additional numerical analyses.

  • 14.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    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 Construction Engineering.
    Reduction of Early Age Crack Risks in Concrete Walls by Using a New Casting Technique2016In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 26, no 3, p. 216-224Article in journal (Refereed)
    Abstract [en]

    Volumetric changes in early age concrete that are restrained might lead to cracks. The degree of restraint is influenced by the casting sequence and the dimensions of the castings. In the current study a new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that lower part of the wall is cast together with the slab, and that part is called a kicker. Hereby, the behavior of the structure changes from a typical case wall-on-slab to a typical case wall-on-wall. It has been proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers. In the paper different kicker heights are studied with the aim of determining the minimum restraint in the upper part of the wall cast in contact with the kicker. The technique using kickers is compared with common measures used in the field to avoid cracking, such as cooling pipes in the new casting and/or heating cables in the adjoining old concrete. The presented method is both cost and time effective, as it opens the possibility to use larger structural length of each casting sequence.

  • 15.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    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.
    Using Artificial Neural Network to Predict the Restraint in Concrete Culvert at Early Age2015In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 25, no 3, p. 258-265Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurate prediction of the risk of concrete cracking at early age. The present study predicts the restraint in 324 walls and 972 roofs for a concrete culvert. A parametric study included the thickness and width of the roofs, thickness and height of the walls, thickness and width of the slab, and length of the structures. Each parameter increased or decreased the restraint in the walls and the roofs. The calculation of the restraint was done elastically by the finite-element method (FE). The results were used by an artificial neural network (ANN) tool, where firstly an influential percentage was investigated as input parameters on the restraint prediction. Equations have been derived by the ANN model to calculate the restraint in the walls and the roofs. It was then used in an Excel sheet to calculate the restraint and compare the result with the result from the finite-element calculations giving high accuracy between the ANN model and the FE calculations

  • 16.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    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.
    Effect of casting sequences on the restraint in slab-on-ground2014Conference paper (Refereed)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks. Restraint represents one of the main sources of thermal and shrinkage stresses at early age concrete. The casting sequence is affected by the restraint from adjacent structures. The present study discusses the influence of five casting sequences for the typical structure slab-on-ground. The aim is to map restraints for a number of possible casting sequences, and to identify the sequence with the lowest restraint. The study covers both continuous and jumped casting sequences, which include one, two and three contact edges. The result shows that the best casting sequence is the continuous technique with one contact edge

  • 17.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    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.
    Effect of the boundary conditions on the crack distribution in early age concrete2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 347-351Article in journal (Refereed)
    Abstract [en]

    Restrained movement in early age concrete may cause cracking. The boundary conditions – restraint – influence the possible crack distribution. This study aims at highlighting the effect of such restraint on the crack distribution. This is done by using the “Cracking Model for Concrete” in ABAQUS/Explicit simulating the non-linear behaviour under and after cracking. In the study the typical case wall-on-slab was in focus using a structure previously been tested in laboratory with both fixed and free bottom slab. The result of the modelling shows fairly good agreement with the cracks observed in the tests.

  • 18.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Re-usage of Concrete Elements: To determine their new possible environment2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 229-232Article in journal (Refereed)
    Abstract [en]

    40% of the energy consumption in Sweden is used in the construction industry. Recycling – including re-usage, recycling and energy recovery – could possibly reduce this energy consumption. Re-usage gives the largest energy savings, evaluated by calculating the recycling potential. Designing for disassembly means planning how structures can easily be disassembled into original components and then recycled. Concrete elements must be designed, documented and assessedregarding reinforcement, cutting locations and degradation, respectively, for a safe reusage in new environments. A plan is designed for how to assess concrete elements and for which new environments they can be used in.

  • 19.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    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.
    Large-scale tests on a composite bridge with prefabricated concrete deck and dry deck joints2013In: Stahlbau, ISSN 0038-9145, E-ISSN 1437-1049, Vol. 82, no 2, p. 122-133Article in journal (Refereed)
    Abstract [en]

    This paper describes the large-scale tests on a composite bridge with prefabricated deck elements and dry joints between the elements. The work is part of the European R&D project ELEM (RFCS-CT-2008-00039). This type of bridge has been used for three single-span bridges in Sweden and has contributed to minimizing construction time as well as disturbance to traffi c. The behaviour at midspan and the behaviour over an internal support of a continuous bridge were studied in the tests, and the results analysed by FEM and discussed. Conclusions regarding the design of this type of bridge are drawn, with respect to the global analysis as well as cross-section capacity.

  • 20.
    Hatem, Mohammed
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Pusch, Roland
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Emborg, Mats
    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.
    Alireza, Pourbakhtiar
    Talc-based concrete for sealing borehole optimized by using particle packing theory2013In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, no 4, p. 440-455Article in journal (Refereed)
    Abstract [en]

    The paper describes assessment of the performance of cement-poor concreteson the basis of packing theory. The concretes are intended for sealing segments of deep boreholes and have a small amount of cement for minimizing the mutual chemical impact on the contacting clay seals. The composition is examined by application of packing theory with respect to the cement/aggregate ratio and the gradation of the aggregate material which is crushed quartzite for providing high internal friction after maturation, as well as to talc added for fluidity and to the small amount of cement. Low porosity and micro-structural stability must be guaranteed for very long periods of time. The study exemplifies how packing theory assist designers in selecting optimal proportions of the various components. Optimum particle packing implies minimizing the porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles. The use of talc as inorganic super-plasticizer since ordinary organic additives for reaching high fluidity at casting are undesirable, and since talc reacts with cement and provides high strength in along-term perspective.

  • 21.
    Nilsson, Martin
    et al.
    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.
    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.
    Fastenings (anchor bolts) in concrete structures: influence of surface reinforcement2012In: 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. 419-422Conference paper (Refereed)
    Abstract [en]

    Tests have been carried out to study the influence of surface reinforcement on the load bearing capacity of cast-in headed bars. In 66 tests, rods with a diameter of Φ30 mm and a Φ45 mm nut at the end, were cast-in place centrically in concrete slabs. Width, length and thickness of the slabs varied from 1.2 m × 1.2 m × 0.3 m up to 2.2 m × 2.2 m × 0.6 m. The top reinforcement varied from 0% to about 1.2% (Φ 16 #100). A considerable increase in the load-bearing capacity was noted. The increase depends on the geometry and the amount and placement of the reinforcement. A numerical model to evaluate the influence is proposed.

  • 22.
    Nilforoush, Rasoul
    et al.
    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.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Project: Anchorage in Concrete Structure2012Other (Other (popular science, discussion, etc.))
  • 23.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Robustare brobaneplatta2012Report (Other academic)
  • 24.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    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.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hösthagen, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 1: Development of Equivalent Restraint Method2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 17-38Article in journal (Refereed)
    Abstract [en]

    The present study deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.

  • 25.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Yousif, Salim T
    Mosul University.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 2: Restraint factors for typical case wall-on-slab2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 39-56Article in journal (Refereed)
    Abstract [en]

    Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.

  • 26.
    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)
  • 27.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    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.
    A study of concrete shear keys in prefabricated bridges with dry deck joints2011In: Nordic Concrete Research: Proceedings of the XXI Nordic Concrete Symposium, Hämeenlinna, Finland 2011, Oslo: The Nordic Concrete Federation , 2011, p. 495-499Conference paper (Refereed)
  • 28.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    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.
    Concrete shear keys in prefabricated bridges with dry deck joints2011In: Nordic Concrete Research, ISSN 0800-6377, Vol. 2011, no 44Article in journal (Refereed)
    Abstract [en]

    A prefabricated concrete deck with dry joints between deck elements has been developed to make prefabricated bridges even more competitive. This type of bridge deck has been used on single span bridges in Sweden, and is now under development for multi span bridges. This paper describes how the deck system works. Results from laboratory tests of shear keys between deck elements are also presented together with an analysis comparing the predicted capacity with the measured failure load.

  • 29.
    Nilsson, Martin
    et al.
    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.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Effects of surface reinforcement on bearing capacity of concrete with anchor bolts2011In: Nordic Concrete Research, ISSN 0800-6377, Vol. 2011, no 44, p. 161-174Article in journal (Refereed)
    Abstract [en]

    66 tests of the influence of surface reinforcement on the tensile load capacity of cast-in fasteners have been carried through. In the tests threaded rods ∅30 mm with a ∅45 mm nut at the end were cast-in centrically in concrete slabs (1.2 m × 1.2 m × 0.3 m up to 2.2 m × 2.2 m × 0.6 m). The amount of surface reinforcement was varied from 0% up to about 1.2%. There is a considerable increase in the load capacity with surface reinforcement present. The increase depends on the geometry and the amount and placement of the reinforcement.

  • 30.
    Häggström, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin (Editor)
    International Workshop on Eurocode 4-2, Composite Bridges2011Report (Other academic)
    Abstract [sv]

    Under de senaste åren har ingenjörer och designers i Europa börjat att använda Eurokod 4-2 – Samverkansbroar. Tillämpningen är nästan densamma i de olika länderna, fast med vissa skillnader, som det kan vara i början. Man har funnit en del svårigheter, problem och fördelar. Den 17 mars 2001 hölls en workshop om Eurokod 4-2 – Samverkansbroar på Ramböll i Stockholm och som lockade omkring 55 personer från tio olika länder. Workshopen fokuserade på bakgrunden till reglerna, på erfarenheter från Frankrike, Storbritannien, Sverige och Italien och avrundades med lite innovativa utveckling av samverkansbroar och en diskussion om möjlig forskning och utveckling för vidare utveckling av Eurokod 4-2.

  • 31.
    Jonasson, Jan-Erik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wallin, Kjell
    Cement- och betonginstitutet.
    Nilsson, Martin
    Gjutning av vägg på platta: studier av sprickrisker orsakat av temperaturförloppet vid härdningen2009Report (Other academic)
    Abstract [en]

    Tests casting the construction "wall on slab" have in the project been realized for three different situations. Measurements have been performed with respect to temperatures, deformations, strains and mapping of crack patterns. In addition, properties for the young concrete have been investigated to get basic data in order to estimate temperatures and risks of cracking. The construction wall on slab represents a typical case, which can be found in many real structures like walls, retaining walls, tray structures, tunnels and bridges.The project has two main questions: 1) What are the differences in restraint conditions between the three tested constructions? Is it correct to model a wall, that both has a horizontal casting joints against the slab, and a vertical casting joint against an adjacent wall, with a free wall of double length?, and 2) Does a slip in the horizontal casting joint exist, and does is reduce the restraint in the wall?The answers are that the supposed models describe the real behaviour very well. This was confirmed by the fact that both the temperatures as well as the crack risks agreed very well between the test results and the calculation results. For the walls that cracked a slip in the casting joints could be indicated, but these test results could not be quantified. In summary, the project has been successful and clearly answered questions that previously only were based on assumptions.

  • 32. Collin, Peter (Editor)
    Hällmark, Robert (Editor)
    Nilsson, Martin (Editor)
    International workshop on prefabricated composite bridges2009Report (Other academic)
  • 33. Eriksen, Jörgen
    et al.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Monitoring of a bridge with integral abutments2009In: Proceedings of Workshop: COST Action C25 : Sustainability of Constructions - Integrated Approach to Life-time Structural Engineering, 2009, p. 176-183Conference paper (Refereed)
    Abstract [en]

    Preliminary results obtained from short term test-loading are used to illustrate possibilities of FEM used to calibrate complex interaction characteristics between a pile and soil in a bridge with integral abutments. The measurements are obtained during the winter season on the bridge over Leduån, in Northern Sweden. The bridge is built in 2006 and used for long term monitoring within the international project INTAB supported by RFCS. The main objective of the on-going research project is to propose recommendations for rational analysis and design of bridges with integral abutments.

  • 34.
    Hällmark, Robert
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Collin, Peter
    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.
    Prefabricated composite bridges2009In: Sustainable Infrastructure: environment friendly, safe and resource efficient ; proceedings of IABSE symposium, Bangkok, Thailand, Sept. 9 - 11, 2009 / [ed] Mahāvidyālăy Culālaṅkărṇ, Zürich: International Association for Bridge and Structural Engineering, 2009, p. 282-283Conference paper (Refereed)
  • 35.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Evaluation of in-situ measurements of composite bridge with integral abutments2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bridges are an important element of the infrastructure today. The technical competence has reached high levels in most countries and the limits given to a bridge designer are set by economic restrictions rather than technical skill. The ever lasting chase for more economic solutions and procedures includes both a wish for cheaper constructions as well as for a decrease in the following maintenance costs. The roller bearings used in conventional bridges are known to generate high costs both during construction and due to maintenance, and the possibility to remove these bearings and accompanying expansion joints are therefore investigated since several years. In Sweden, the absence of bridges built with integral abutments has made it difficult to test and evaluate this solution. In 2005, an international project called Intab was launched with the explicit aim to look at different solutions possible to use if joints and bearings are excluded. One of the most common discussed problems concerning bridges built without expansion joints is the accommodation of longitudinal elongation due to temperature variations. A bridge built with integral abutments is often supported by piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a moment in these piles, which in time may cause a fatigue failure. Therefore it is of big interest to look at the amplitude of these strains. Within the Intab project, a pilot object was built in Nordmaling, ~50 km south of Umeå. It is a 40 meter long and 5 meter wide composite bridge with two steel girders and a concrete deck. The steel piles in this bridge is equipped with strain gauges who are used both for longterm and shortterm measurements. The sampled data from longterm measurement is collected on a computer on site, and then downloaded through a traditional modem. The data from the shortterm measurement is sampled and collected immediately during the test. The shortterm test is performed during both summer and winter conditions, and consists of a lorry passing the bridge while different measurements are done. The result from the measurement is also compared to calculations and a 2-D FE-model. It seems that short-term measurements performed during warmer months, May and October, show better agreement with the FE-simulations than the tests performed during the winter. The used FE-model is based on restrictions from Bro 2004. Regarding the long-term measurements, the obtained strain values are not in a range where fatigue can be considered as a severe problem.

  • 36.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint in early concrete walls cast on slabs determined by a semi-analytical method2008In: Proceedings, Nordic Concrete Research, Bålsta, Sweden: [ ... XXth Symposium on Nordic Concrete Research & Development ... The current proceedings contain 90 summaries of oral poster presentations] / [ed] Johan Silfwerbrand, Oslo: Norsk Betongforening , 2008, p. 36-37Conference paper (Refereed)
  • 37.
    Nilsson, Martin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Eriksen, Jörgen
    Luleå tekniska universitet.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Towards a better understanding of behaviour of bridges with integral abutments2008In: Composite construction in steel and concrete VI: proceedings of the 2008 conference, July 20 - 24, 2008, Devil's Thumb Ranch, Tabernash, Colorado / [ed] Roberto T. Leon, Reston: American Society of Civil Engineers (ASCE), 2008, p. 717-727Conference paper (Refereed)
    Abstract [en]

    One of the issues that has not been completely resolved in bridges built without expansion joints is the influence of seasonal temperature variations and soil characteristics on the maximum bridge length. To study this problem, a 40 meter long road composite bridge over the river Leduân in the north of Sweden was built in 2005. The bridge superstructure was cast integrally with the substructure. One row of piles on each side of the bridge was constructed to support the abutment. The bridge was continuously monitored for 18 months in order to provide information on the strain level at the top of the pile as a function of the air temperature variations. The results from the measurements were compared to results obtained from 2D Finite Element Analysis. Soil characteristics were varied in the FEA to investigate its influence on the overall bridge behaviour as well as on the level of strain variations at the top of the piles. The bridge monitoring was a part of a research project, INTAB, Economic and Durable Design of Composite Bridges with Integral Abutments, 2005-2008. The main objective of the project was to propose recommendations for rational analysis and design of bridges with integral abutments. The total environmental impact and the life cycle costs of the integral abutment bridge were compared with a concrete bridge alternative for the same crossing

  • 38.
    Emborg, Mats
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simonsson, Peter
    Carlswärd, Jonas
    Nilsson, Martin
    Industrial casting of bridges combining new production methods materials: like a robust SCC, utilizing lean construction principle2007In: Proceedings of the 5th International RILEM Symposium on Self-Compacting Concrete: SCC2007 / [ed] G De Schutter; V Boel, Bagneux, France: Magnel Laboratory for Concrete Research, Ghent University , 2007, Vol. 1, p. 485-490Conference paper (Refereed)
  • 39. Nilsson, Martin
    et al.
    Husson, Wylliam
    Collin, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Petursson, Hans
    Monitoring of a bridge with integral abutment2007In: Improving Infrastructure Worldwide: IABSE symposium, Weimar 2007, [September 19 - 21, 2007] ; report / [ed] Ulrike Kuhlmann, Zürich: International Association for Bridge and Structural Engineering, 2007Conference paper (Refereed)
    Abstract [en]

    Preliminary results obtained from short term test-loading are used to illustrate possibilities of FEM used to calibrate complex interaction characteristics between a pile and soil in a bridge with integral abutments. The measurements are obtained during the winter season on the bridge over Ledån, Northern Sweden. The bridge is built in 2006 and used for long term monitoring within the international project supported by RFCS. The main objective of the on-going research project is to proposed recommendations for rational analysis and design of bridges with integral abutments.

  • 40. Enochsson, Ola
    et al.
    Puurula, Arto
    Stenlund, Anders
    Thun, Håkan
    Nilsson, Martin
    Täljsten, Björn
    Olofsson, Thomas
    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.
    Condition assessment of concrete bridges in Sweden2005In: Concrete repair, rehabilitation and retrofitting / [ed] Mark G. Alexander; Hans-Dieter Beushausen; Frank Dehn; Pilate Moyo, London: Taylor and Francis Group , 2005, p. 257-259Conference paper (Refereed)
    Abstract [en]

    Examples are given of methods used and results obtained from two bridges assessed in Sweden. The following sectional forces were critical: (a) Bending, shear and fatigue in a two-span railway trough bridge and (b) Shear and torsion in a three-span prestressed cantilever box girder road bridge. In the assessments we evaluated material properties, loads and load carrying capacity using deterministic and probabilistic methods

  • 41.
    Emborg, Mats
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Nilsson, Martin
    Utsi, Sofia
    Simonsson, Peter
    Designing robust SCC for industrial construction with cast in place concrete2005In: Second North American Conference on the Design and Use of Self-Consolidating Concrete [and] Fourth International RILEM Symposium on Self-Compacting Concrete; [October 30 - November 2, 2005];Second North American Conference on the Design and Use of Self-Consolidating Concrete [and] Fourth International RILEM Symposium on Self-Compacting Concrete; [October 30 - November 2, 2005: [proceedings] / [ed] Surendra P. Shah, Hanley Wood, 2005, p. 1251-1257Conference paper (Refereed)
  • 42.
    Stenlund, Anders
    et al.
    Trafikverket.
    Nilsson, Martin
    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 Bridge Research: A Survey 2005 Sustainable Bridges SB-D1.42005Report (Refereed)
    Abstract [en]

    An overview is reported of current research regarding railway bridges. Research themes and active institutes and organisations are listed. The work has been carried out during 2004/2005 in the project “Sustainable Bridges –Assessment for Future Traffic Demands and Longer Lives”, an Integrated Research Projectwithin the Sixth Framework Programme of the European Commission. Most of the material has been obtained from the web but personal knowledge and direct communication with some of the institutes/organisations has also been used. An overview like this can never be complete and we apologize for all unintended omissions. Research is going on all over the world. The most studied subjects are:

    • Assessment

    • Structural behaviour and monitoring

    • Repair and strengthening

    • Dynamic effects and vibration

    • Life cycle analysis

  • 43.
    Carolin, Anders
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Täljsten, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Enochsson, Ola
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Fahleson, Claes
    Tillförlitlighetsanalys för reparerade eller förstärkta byggnadskonstruktioner2004Report (Other academic)
    Abstract [sv]

    I rapporten visas på möjligheterna med att använda tillförlitlighetsanalys på byggnadskonstruktioner som förstärks. I det stora fokuseras på betongkonstruktioner och särskilt diskuteras förstärkning av betongkonstruktioner med hjälp av utanpåliggande kolfiberkompositmaterial. Förstudien visar att tillförlitlighetsanalys i generella termer kan vara mycket användbart när det gäller att studera bärförmågan samt vilken konsekvens detta har för den befintliga konstruktionen, speciellt tydligt blir detta när det kopplas till verkliga objekt. Utöver detta visar studien på möjligheter att på ett mer nyanserat sätt förstärka konstruktioner där tillförlitlighetsanalys är ett viktigt verktyg. Studien visar också på behov av fortsatt forskning, speciellt tydligt är detta när det gäller vilka värden samt vilka partialkoefficienter man ska välja för de nya materialen som börjar användas, dvs. för kompositmaterial. I tillägg till detta behöver en nyanserad studie göras gällande de beräkningsmodeller som används i samband med förstärkning och även avseende på de brottmoder som kan uppstå.

  • 44. Nilsson, Martin
    et al.
    Elfgren, Lennart
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Partial coefficient for thermal cracking problems determined by a probabilistic method2003In: Nordic Concrete Research, ISSN 0800-6377, Vol. 27, p. 107-125Article in journal (Refereed)
    Abstract [en]

    The aim of this work is to calculate partial coefficients for thermal cracking problems of young concrete and to compare the results with the values stated in the Swedish building code for bridges, [1]. The code values are only based on experiences and logical reasoning, whereas the calculated values form a more theoretical base for their determination. The coefficients are calculated with a probabilistic method. Various different possible variations of the used variables have been studied showing the wide range of possible results depending on the input. However, with use of material properties and reasonable assumptions related to thermal cracking problems, fairly good agreement has been found between the stated values in the Swedish code [1] and the values obtained through the probabilistic method. The calculated values are based on many assumptions and assumed values and should therefor not be seen as what is right but rather more as an indication on the reasonableness of the values stated in the Swedish code. Further investigations, calculations and judgements should be performed before wider conclusions can be drawn.

  • 45.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint factors and partial coefficients for crack risk analyses of early age concrete structures2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is well known for contractors that due to volume change during the hydration phase in concrete structures, large stresses can arise if the structures are restrained, stresses that may cause extensive cracking. Crack risk estimation of early age concrete structures can be based on five steps. Firstly, the type of structure, the material proportions and possible measures to avoid cracking have to be chosen. Secondly, the temperature development has to be determined, and thirdly the restraint situation. Fourthly, structural calculation of the stress or strain ratios follows, which in the fifth step are compared to stated partial coefficients that should not be exceeded. The restraint situation is one of the crucial factors in the crack risk analyses. A semi-analytical method has been derived for the determination of the restraint variation in early age concrete structures and especially for the case wall on slab. The method is derived using compensated line theory. The model depends on the geometry of the structure, the boundary restraint situation, and the location of the young parts on the old parts. The model is supplemented with the effects of high walls and the effects of short structures and/or possible slip failure in the ends of the joint between the young and the old concrete. The model is by regression technique compared to almost 3000 3D elastic FEM calculations of the restraint variation in walls on slabs with different dimensions and base restraint situations. The effective width of the slab is introduced as the only adjustment parameter to get the model to correspond with the FEM calculations. Partial coefficients for thermal cracking problems of young concrete have been calculated and compared with the values stated in the Swedish building code for bridges. The code values are only based on experiences and logical reasoning, whereas the calculated values form a more theoretical base for their determi-nation. The coefficients are calculated with a probabilistic method. Various possible variations of the used variables have been studied showing the wide range of possible results depending on the input. However, with use of material properties and reasonable assumptions related to thermal cracking problems, fairly good agreement has been found between the stated values in the Swedish code and the values obtained through the probabilistic method.

  • 46.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint factors and partial coefficients for crack risk analyses of early age concrete structures: diagrams and tables2003Report (Other academic)
    Abstract [en]

    This report contains all background data for the Doctoral Thesis 2003:19 "Restraint Factors and Partial Coefficients for Crack Risk Analyses of Early Age Concrete Structures" by Martin Nilsson.

  • 47.
    Enochsson, Ola
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hejll, Arvid
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Thun, Håkan
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Elfgren, Lennart
    Bro över Luossajokk: beräkning med säkerhetsindexmetod, böjdragkapacitet i överkant i mittsnittet i korta spannet2002Report (Other academic)
    Abstract [sv]

    I samband med projektet "30 ton på Malmbanan", Paulson-Töyrä (1996), konstaterades att bron över Luossajokk i Kiruna inte klarade de nya förhöjda lasterna. Bron har två spann och en utkragande konsol 10,25 + 6,3 + 3,4 m. Överbyggnaden utgörs av ett slakarmerat betongtråg med ett nytt mellanstöd som uppfördes 1965 då en äldre överbyggnad byttes ut. En klassningsberäkning och en utredning av förstärkningsbehov utfördes. Efter en förnyad översyn av brons bärförmåga utfördes töjningsmätningar vintern och sommaren 2001. Töjningsmätningarna indikerade förvånansvärt små påkänningar i bron. En närmare utredning av brons säkerhet att bära uppträdande laster genomförs därför i denna rapport. Detta sker med hjälp av en nyanserad säkerhetsberäkning med säkerhetsindexmetod. Den nya genomgången visar att medelvärdet för bärförmågan för moment är 2,89 MNm med standardavvikelsen 0,19 MNm i det mest utsatta snittet med dragpåkänningar i överkant i korta spannet. Detta kan jämföras med det formella dimensioneringsvärdet 1,99 MNm som erhölls i klassningsberäkningen med beaktande av aktuella partialkoefficienter. I det nya medelvärdet har en lägre uppmätt effektiv höjd beaktats, att ett av tolv armeringsjärn borrats av samt att betong- och armeringshållfastheterna är högre än de nominella dimensioneringsvärdena. På lastsidan gav klassningsberäkningen i motsvarande snitt att det formella dimensioneringsvärdet för momentet är 2,79 MNm. En analys av verkliga uppträdande laster ger att medelvärdet maximalt uppgår till 2,05 MNm. Detta lastfall utgörs av ett lok placerat med tre axlar i längsta spannet och tre axlar placerade på konsolen, om såväl bromslast som ojämn temperaturlast och dynamiskt tillskott uppträder samtidigt. Enligt BV Bärighet (1996) behöver ojämn temperatur inte beaktas, vilket är rimligt med tanke på att detta är ett statiskt obestämt lastfall som försvinner vid uppsprickning i brottstadiet. Det har heller inte medräknats i tidigare klassningsberäkningar. I så fall fås att lasten har medelvärdet 1,66 MNm och att säkerhetsindex β varierar mellan 3,8 och 6,0 beroende på vilka antaganden som görs om lasternas statistiska fördelning. För en rimlig fördelning innehålls kravet i säkerhetsklass 3 att säkerhetsindex β 4,75. Bron visar sig därför, enligt vår bedömning och med beaktande av erhållna mätresultat, ha erforderlig bärförmåga om hastigheten begränsas på bron så att eventuella dynamiska tillskott blir låga och/eller inverkan av ojämn temperatur försummas. Brons fortsatta uppförande bör kontrolleras genom ett mätprogram. Detta bör förutom armeringstöjningar med befintliga givare även inkludera mätningar av nedböjningar för att säkerställa att använda beräkningsmodeller och randvillkor på ett korrekt sätt återger brons beteende. Storleken på den dynamiska förstoringsfaktorn D bör även mätas liksom inverkan av bromskrafter och ojämn temperaturfördelning. På så sätt kan ett säkrare underlag erhållas för bedömning av frekvensfunktionerna för dessa vanliga lasteffekter. Dessa värden borde även vara av intresse vid säkerhetsbedömning av likartade järnvägsbroar.

  • 48. Jonasson, Jan-Erik
    et al.
    Wallin, Kjell
    Emborg, Mats
    Gram, Annika
    Saleh, Iad
    Nilsson, Martin
    Larsson, Mårten
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Handbok med sprickriskbedömning inklusive åtgärder för betongkonstruktioner2001In: Bygg & Teknik, ISSN 0281-658X, Vol. 93, no 7, p. 16-20Article in journal (Other (popular science, discussion, etc.))
  • 49.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Rotational boundary restraint factor2001Report (Other academic)
  • 50. Jonasson, Jan-Erik
    et al.
    Wallin, Kjell
    Emborg, Mats
    Gram, Annika
    Saleh, Iad
    Nilsson, Martin
    Larsson, Mårten
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Temperatursprickor i betongkonstruktioner: handbok med diagram för sprickriskbedömning inklusive åtgärder för några vanliga typfall. Del D och E2001Report (Other academic)
    Abstract [sv]

    Föreliggande handbok är framtagen i ett SBUF-projekt med Kjell Wallin, Peab som projektledare. Projektet har genomförts i nära samarbete mellan Peab Sverige AB och Luleå tekniska universitet. Arbetet har inneburit att ett stort antal datorberäkningar har genomförts, och de redovisas i diagramform i denna handbok. Resultaten avses att användas att fylla i en blankett i ett Excel-ark. Syftet är att för typfallet vägg-på-platta ska handboken ge underlag för sprickriskbedömning och i förekommande fall ange vilka typåtgärder som ska sättas in. Avsikten är därvid att man inte ska behöva göra några externa beräkningar, men användaren har full frihet att själv ta fram temperaturen eller tvångssituationen på godtyckligt annat sätt. Handboksmetodiken avser en fortsättning på det som i Bronormen (Bro 94, bilaga 9-5) kallas metod 2, och den redovisade kompletteringen innefattar främst att erforderliga åtgärder (kylning och/eller värmning) för det valda typfallet inkluderas.

12 1 - 50 of 57
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf