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Popescu, C., Täljsten, B., Blanksvärd, T. & Elfgren, L. (2019). 3D reconstruction of existing concrete bridges using optical methods. Structure and Infrastructure Engineering, 15(7), 912-924
Åpne denne publikasjonen i ny fane eller vindu >>3D reconstruction of existing concrete bridges using optical methods
2019 (engelsk)Inngår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 15, nr 7, s. 912-924Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Routine bridge inspections usually consist of visual observations. These inspections are time-consum-ing and subjective. There is a need to identify new inspection techniques for infrastructure that reducetraffic disturbance, and improve the efficiency and reliability of the acquired data. This study comparedthe performance of three different imaging technologies for the three-dimensional (3D) geometricmodeling of existing structures: terrestrial laser scanning, close-range photogrammetry, and infraredscanning. Each technology was used to assess six existing concrete railway bridges. The technologieswere compared in terms of geometric deviations, visualization capabilities, the level of the inspector’sexperience, and degree of automation. The results suggest that all methods investigated can be usedto create 3D models, however, with different level of completeness. Measurements such as spanlength, deck widths, etc. can be extracted with good accuracy. Although promising, a full off-siteinspection is currently not feasible as some areas of the bridges were difficult to capture mainly dueto restricted access and narrow spaces. Measurements based on terrestrial laser scanning were closerto the reality compared to photogrammetry and infrared scanning. The study indicates the no specialtraining is needed for photogrammetry and infrared scanning to generate a 3D geometric model.

sted, utgiver, år, opplag, sider
Taylor & Francis, 2019
Emneord
3D geometric modeling, terrestrial laser scanning, photogrammetry, infrared scanning, bridge inspection, remote sensing
HSV kategori
Forskningsprogram
Byggkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-73644 (URN)10.1080/15732479.2019.1594315 (DOI)000466668000001 ()2-s2.0-85064494122 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-07-12 (johcin)

Tilgjengelig fra: 2019-04-15 Laget: 2019-04-15 Sist oppdatert: 2019-07-12bibliografisk kontrollert
Bagge, N., Plos, M. & Popescu, C. (2019). A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure. Structure and Infrastructure Engineering, 15(1), 27-53
Åpne denne publikasjonen i ny fane eller vindu >>A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure
2019 (engelsk)Inngår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 15, nr 1, s. 27-53Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper describes a multi-level strategy with increased complexity through four levels of structural analysis of concrete bridges. The concept was developed to provide a procedure that supports enhanced assessments with better understanding of the structure and more precise predictions of the load-carrying capacity. In order to demonstrate and examine the multi-level strategy, a continuous multi-span prestressed concrete girder bridge, tested until shear failure, was investigated. Calculations of the load-carrying capacity at the initial level of the multi-level strategy consistently resulted in underestimated capacities, with the predicted load ranging from 25% to 78% of the tested failure load, depending on the local resistance model applied. The initial assessment was also associated with issues of localising the shear failure accurately and, consequently, refined structural analysis at an enhanced level was recommended. Enhanced assessment using nonlinear finite element (FE) analysis precisely reproduced the behaviour observed in the experimental test, capturing the actual failure mechanism and the load-carrying capacity with less than 4% deviation to the test. Thus, the enhanced level of assessment, using the proposed multi-level strategy, can be considered to be accurate, but the study also shows the importance of using guidelines for nonlinear FE analysis and bridge-specific information. 

sted, utgiver, år, opplag, sider
Taylor & Francis, 2019
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-71356 (URN)10.1080/15732479.2018.1476562 (DOI)000455942800003 ()2-s2.0-85054830749 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-04-12 (johcin)

Tilgjengelig fra: 2018-10-26 Laget: 2018-10-26 Sist oppdatert: 2019-04-12bibliografisk kontrollert
Huang, Z., Tu, Y., Meng, S., Sabau, C., Popescu, C. & Sas, G. (2019). Experimental study on shear deformation of reinforced concrete beams using digital image correlation. Engineering structures, 181, 670-698
Åpne denne publikasjonen i ny fane eller vindu >>Experimental study on shear deformation of reinforced concrete beams using digital image correlation
Vise andre…
2019 (engelsk)Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 181, s. 670-698Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper presents an experimental program aimed at providing reliable and comprehensive experimental data for assessing the available models of predicting the shear deformation of diagonally-cracked reinforced concrete (RC) beams. The non-contact measuring technique, Digital Image Correlation (DIC), was used to monitor the full-field displacement and strain in the shear span of five RC beams with thin webs. Virtual measuring grids were created to measure the mean shear strain and other critical deformation results which reflects the mechanism of shear deformation after shear cracking (i.e. the principal compressive strain angle, the principal compressive strain, the mid-depth longitudinal strain and the mean vertical strain). The experimental mean shear strain and other critical deformation results were compared with the predictions with several available models. The comparison indicates the available models fail to reproduce the principal compressive strain angle, the mid-depth longitudinal strain and the mean vertical strain which constitute the key parameters in estimating the shear deformation after shear cracking. As a result, significant discrepancies in the shear deformation of the beams tested in this paper are observed between the experimental and calculated results. It is also found that the predicted shear deformation of a number of beam specimens tested by other researchers with the available models deviates considerably from the experimental results. In general, the existing models are not capable of providing accurate predictions of the shear deformation of RC beams and further investigation into this topic is needed.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
Reinforced concrete beams, Shear deformation, Experimental study, Digital image correlation
HSV kategori
Forskningsprogram
Byggmaterial
Identifikatorer
urn:nbn:se:ltu:diva-72817 (URN)10.1016/j.engstruct.2018.12.056 (DOI)000456754400049 ()2-s2.0-85058962784 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-02-07 (johcin)

Tilgjengelig fra: 2019-02-07 Laget: 2019-02-07 Sist oppdatert: 2019-02-22bibliografisk kontrollert
Sabau, C., Popescu, C., Bagge, N., Sas, G., Blanksvärd, T. & Täljsten, B. (2019). Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings. Engineering structures, 187, 57-72
Åpne denne publikasjonen i ny fane eller vindu >>Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings
Vise andre…
2019 (engelsk)Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 187, s. 57-72Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper presents the finite element analysis (FEA) results of a multi-story reinforced concrete (RC) building having precast and cast-in-place load bearing walls. Door-type cut-out openings (height: 2.1 m, width: 0.9–4.4 m) were created at the first and second story of the building. Results from experimental tests on axially loaded RC panels were used to verify the modeling approach. The influence of cut-out openings on the response of individual RC panels, failure modes, and load redistribution to adjacent members was analyzed. Moreover, the wall bearing capacities obtained from FEA were compared with the values calculated from design equations. The results revealed that the robustness of multi-story buildings having RC load bearing wall systems decrease considerably with the creation of cut-out openings. However, owing to the initial robustness of the buildings, large cut-outopenings could be created under normal service conditions without strengthening of the building structure. Furthermore, design equations provided very conservative predictions of the ultimate capacity characterizing the solid walls and walls with small openings, whereas similar FEA and analytically predicted capacities were obtained for walls with large openings.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
FEM, reinforced concrete, building assessment, wall, openings
HSV kategori
Forskningsprogram
Byggkonstruktion
Identifikatorer
urn:nbn:se:ltu:diva-70883 (URN)10.1016/j.engstruct.2019.02.046 (DOI)000462689900006 ()2-s2.0-85062088838 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-03-07 (inah)

Tilgjengelig fra: 2018-09-18 Laget: 2018-09-18 Sist oppdatert: 2019-04-23bibliografisk kontrollert
Sabau, C., Popescu, C., Sas, G., Blanksvärd, T. & Täljsten, B. (2018). Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites. Journal of composites for construction, 22(6), 04018046-1-04018046-16, Article ID 04018046.
Åpne denne publikasjonen i ny fane eller vindu >>Axially Loaded RC Walls with Cutout Openings Strengthened with FRCM Composites
Vise andre…
2018 (engelsk)Inngår i: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 22, nr 6, s. 04018046-1-04018046-16, artikkel-id 04018046Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Upgrading existing buildings to new functional requirements may require new openings that can weaken the structure, promptingthe need for strengthening. In such cases traditional strengthening solutions, such as creating a reinforced concrete (RC) or steel frame aroundthe opening, imply long-term restrictions in the use of the structure compared to solutions that use externally bonded composites. Two fabricreinforcedcementitious matrix (FRCM) composites were used in this study to restore the capacity of panels with newly created doortype openings to that of a solid panel. Five half-scale RC panels acting as two-way action compression members were tested to failure.Two full-field optical deformation measurement systems were used to monitor and analyze the global structural response of each testedpanel (i.e., crack pattern, failure mechanism, and displacement/strain fields). The performance of existing design methods for RC panelshas been assessed in comparison with the experimental results. The capacity of strengthened panels with small openings (450 × 1,050 mm) was entirely restored to that of the solid panel. However, for panels with large openings (900 × 1,050 mm), only 75% of the solid panel’scapacity was restored. The capacity of the strengthened panels was about 175 and 150% higher compared to that of reference panels withsmall and large openings, respectively.

sted, utgiver, år, opplag, sider
American Society of Civil Engineers (ASCE), 2018
Emneord
FRCM, Reinforced concrete, Walls with openings, Digital image correlation
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-70579 (URN)10.1061/(ASCE)CC.1943-5614.0000867 (DOI)000447252600001 ()2-s2.0-85051927413 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-08-24 (andbra)

Tilgjengelig fra: 2018-08-24 Laget: 2018-08-24 Sist oppdatert: 2018-10-29bibliografisk kontrollert
Täljsten, B., Blanksvärd, T., Sas, G., Bagge, N., Nilimaa, J., Popescu, C., . . . Häggström, J. (2018). Bridges tested to failure in Sweden. In: IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the FutureJune 25-27 2018, Copenhagen, Denmark: . Paper presented at IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the Future June 25-27 2018, Copenhagen, Denmark.
Åpne denne publikasjonen i ny fane eller vindu >>Bridges tested to failure in Sweden
Vise andre…
2018 (engelsk)Inngår i: IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the FutureJune 25-27 2018, Copenhagen, Denmark, 2018Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

Five bridges of different types have been tested to failure and the results have been compared to analyses of the load-carrying capacity using standard code models and advanced numerical methods. The results may help to make accurate assessments of similar existing bridges. There it is necessary to know the real behaviour, weak points, and to be able to model the load-carrying capacity in a correct way.The five bridges were: (1) a strengthened one span concrete road bridge - Stora Höga ; (2) a one span concrete rail trough bridge loaded in fatigue – Lautajokk; (3) a two span strengthened concrete trough railway bridge - Övik; (4) a one span railway steel truss bridge -Åby; and (5) a five span prestressed concrete road bridge - Kiruna. The unique results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy and shortcomings/potentials of different codes and models for safety assessment of existing structures

Emneord
Test to failure, bridges of concrete and steel, Assessment, Strengthening, Monitoring, Bending, Shar, Torsion, Bond, Fatigue, Carbon Fibre Reinforced Polymers (CFRP)
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-72378 (URN)
Konferanse
IABSE Conference 2018 – Engineering the Past, to Meet the Needs of the Future June 25-27 2018, Copenhagen, Denmark
Tilgjengelig fra: 2018-12-28 Laget: 2018-12-28 Sist oppdatert: 2019-09-06
Bagge, N., Popescu, C. & Elfgren, L. (2018). Failure tests on concrete bridges: Have we learnt the lessons?. Structure and Infrastructure Engineering, 14(3), 292-319
Åpne denne publikasjonen i ny fane eller vindu >>Failure tests on concrete bridges: Have we learnt the lessons?
2018 (engelsk)Inngår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 14, nr 3, s. 292-319Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Full-scale failure tests of bridges are important for improving understanding of bridges’ behaviour and refining assessment methods. However, such experiments are challenging, often expensive, and thus rare. This paper provides a review of failure tests on concrete bridges, focusing on lessons from them. In total, 40 tests to failure of 30 bridges have been identified. These include various types of bridges, with reinforced concrete or prestressed concrete superstructures, composed of slabs, girders and combinations thereof. Generally, the tests indicated that theoretical calculations of the load-carrying capacity based on methods traditionally used for design and assessment provide conservative estimates. It can also be concluded that almost a third of the experiments resulted in unexpected types of failures, mainly shear instead of flexure. In addition, differences between theoretical and tested capacities are often apparently due to inaccurate representation of geometry, boundary conditions and materials

sted, utgiver, år, opplag, sider
Taylor & Francis, 2018
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-65060 (URN)10.1080/15732479.2017.1350985 (DOI)000423625400002 ()
Merknad

Validerad;2018;Nivå 2;2017-12-20 (andbra)

Tilgjengelig fra: 2017-08-14 Laget: 2017-08-14 Sist oppdatert: 2018-02-16bibliografisk kontrollert
Popescu, C., Schmidt, J. W., Goltermann, P. & Sas, G. (2017). Assessment of RC walls with cut-out openings strengthened by FRP composites using a rigid-plastic approach (ed.). Engineering structures, 150, 585-598
Åpne denne publikasjonen i ny fane eller vindu >>Assessment of RC walls with cut-out openings strengthened by FRP composites using a rigid-plastic approach
2017 (engelsk)Inngår i: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 150, s. 585-598Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Building refurbishment works frequently require the cutting of new openings in concrete walls. Cutting new openings weakens the overall response of such elements, so they usually require strengthening. However, current design codes offer little guidance on strengthening walls with openings, and less still on the use of non-metallic reinforcements such as FRP (Fibre Reinforced Polymers) to ensure sufficient load bearing capacity. This paper proposes a new procedure based on limit analysis theory for evaluating the ultimate load of walls with cut-out openings that have been strengthened with carbon-FRP (CFRP). First, the approach is verified against transverse (out-of-plane) and axial (in-plane) loading for unstrengthened specimens. These loading types result in different failure mechanisms: transverse loading leads to failure due to yielding/rupture of the steel reinforcement while axial loading leads to failure by concrete crushing. Second, the proposed method is further developed for CFRP-strengthened specimens under axial loading. It accounts for the contribution of CFRP indirectly, by updating the concrete model with an enhanced compressive strength as a result of confining the piers. Predictions made using the new method agree closely with experimental results.

sted, utgiver, år, opplag, sider
Elsevier, 2017
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-9022 (URN)10.1016/j.engstruct.2017.07.069 (DOI)000413125800044 ()2-s2.0-85026533028 (Scopus ID)794c01ea-1ee7-4cdf-8f59-1d088954f9bf (Lokal ID)794c01ea-1ee7-4cdf-8f59-1d088954f9bf (Arkivnummer)794c01ea-1ee7-4cdf-8f59-1d088954f9bf (OAI)
Merknad

Validerad; 2017; Nivå 2; 2017-08-15 (andbra)

Tilgjengelig fra: 2016-09-29 Laget: 2016-09-29 Sist oppdatert: 2017-11-24bibliografisk kontrollert
Popescu, C. (2017). CFRP Strengthening of Cut-Out Openings in Concrete Walls – Analysis and Laboratory Tests. (Doctoral dissertation). Luleå: Luleå University of Technology
Åpne denne publikasjonen i ny fane eller vindu >>CFRP Strengthening of Cut-Out Openings in Concrete Walls – Analysis and Laboratory Tests
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Redesigning buildings to improve their space efficiency and allow changes in use is often essential during their service lives to comply with shifts in living standards and functional demands.This may require the introduction of new openings in elements such as beams, walls, and slabs,which inevitably reduces their structural performance and hence requires repair or strengthening.However, there are uncertainties regarding both the effects of openings and the best remedial optionsfor them. Traditionally, two methods have been used to strengthen reinforced concrete (RC) walls with openings, these being either to create a frame around the opening using RC/steel membersor to increase the cross-sectional thickness. Currently, intervention in existing buildings must be minimal in order to minimise inconvenience caused by limiting the use of the structure during repairs. One option is to use externally-bonded fibre-reinforced polymers (FRPs).

In this study, the author reports on an experimental investigation of the effectiveness of carbonFRP (CFRP)–based strengthening for restoring the axial capacity of a solid reinforced concretewall after cutting openings. Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were tested to failure. The walls were tested in two-way action and subjected to axial loading with low eccentricity (defined as one sixth of the wall’s thickness) along the weak axis to represent imperfections due to thickness variation and misalignment of the panels during the construction process. An extensive instrumentation scheme was used to monitor the specimen’s behaviour during the loading cycles. In addition to classical approaches for measuring strains and displacements, optical 3D measurements were also acquired using the digital image correlation (DIC) technique. These provided better overviews of the failure mechanism by recording the crack pattern development and deformation of the walls throughout the loading history.

Reducing the cross-sectional area by cutting out openings i.e. 25% (hereafter referred to as small opening) and 50% (hereafter referred to as large opening) led to 36% and 50% reductions in peak loads, respectively. In both situations the failure was brittle due to crushing of concrete with spalling and reinforcement buckling. The CFRP strengthening increased the axial capacity of walls with small and large openings by 34 – 50% and 13 – 27%, respectively. This partially restored theircapacities to 85 – 95% and 57 – 63% of their precutting capacity (i.e. solid wall), respectively. A procedure based on a rigid-plastic approach for evaluating the ultimate load of walls with cut-out openings that have been strengthened with FRPs was also proposed in this study. Predictions made using the proposed method agree closely with experimental results.

sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2017. s. 159
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-61515 (URN)978-91-7583-794-9 (ISBN)978-91-7583-795-6 (ISBN)
Disputas
2017-02-23, F1031, Luleå, 10:00 (engelsk)
Opponent
Veileder
Merknad

Examining Committee: Professor Karin Lundgren, Division of Structural Engineering, Department of Civil and Environmental Engineering, Chalmers University of Technology, Gothenburg, Sweden

Professor Henrik Stang, Section for Structural Engineering, Department of Civil Engineering, Technical University of Denmark, Lyngby, Denmark

Professor Mats Oldenburg, Division of Mechanics of Solid Materials, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden

Tilgjengelig fra: 2017-01-20 Laget: 2017-01-18 Sist oppdatert: 2017-11-24bibliografisk kontrollert
Popescu, C., Sas, G., Blanksvärd, T. & Täljsten, B. (2017). Concrete walls with cutout openings strengthened by FRP confinement (ed.). Journal of composites for construction, 21(3), Article ID 04016106.
Åpne denne publikasjonen i ny fane eller vindu >>Concrete walls with cutout openings strengthened by FRP confinement
2017 (engelsk)Inngår i: Journal of composites for construction, ISSN 1090-0268, E-ISSN 1943-5614, Vol. 21, nr 3, artikkel-id 04016106Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Redesigning buildings to improve their space efficiency and allow changes in use is often essential during their service lives tocomply with shifts in living standards and functional demands. This may require the introduction of new openings in elements such as beams,walls, and slabs, which inevitably reduces their structural performance and hence requires repair or strengthening. However, there are uncertaintiesregarding both the effects of openings and the best remedial options for them. Here, the authors report on an experimental investigation ofthe effectiveness of fiber-reinforced polymer (FRP)–based strengthening for restoring the axial capacity of a solid RC wall after cutting openings.Nine half-scale specimens, designed to represent typical wall panels in residential buildings with and without door-type openings, were testedto failure. It was found that FRP-confinement and mechanical anchorages increased the axial capacity of walls with small and large openings(which had 25 and 50% reductions in cross-sectional area, respectively) by 34–50% and 13–27%, to 85–94.8% and 56.5–63.4% of their precuttingcapacity, respectively. 

sted, utgiver, år, opplag, sider
American Society of Civil Engineers (ASCE), 2017
HSV kategori
Forskningsprogram
Konstruktionsteknik
Identifikatorer
urn:nbn:se:ltu:diva-2760 (URN)10.1061/(ASCE)CC.1943-5614.0000759 (DOI)000400524800008 ()2-s2.0-85017517559 (Scopus ID)071b8226-9b6c-41f9-9efc-499979742502 (Lokal ID)071b8226-9b6c-41f9-9efc-499979742502 (Arkivnummer)071b8226-9b6c-41f9-9efc-499979742502 (OAI)
Merknad

Validerad; 2017; Nivå 2; 2017-04-25 (andbra)

 

Tilgjengelig fra: 2016-09-29 Laget: 2016-09-29 Sist oppdatert: 2018-11-20bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0001-9423-7436