| 1. |
- Claeson-Jonsson, Christina, 1967, et al.
(författare)
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Slender concrete columns subjected to sustained and short-term eccentric loading
- 2000
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Ingår i: ACI Structural Journal. - 0889-3241. ; 97:1, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- A test series examining the structural behavior of six slender reinforced concrete columns subjected to short-term and sustained loading is presented. The columns had cross sections 200 x 200 mm and were 4 m long. Concrete strengths used were 35 and 92 MPa with a load eccentricity of 20 mm. Key parameters such as concrete strength, concrete and steel strains, cracking, midheight deflection, and loading rate were studied. The high-strength (HSC) columns subjected to short-term loading displayed less ductility and more sudden failures than the normal strength concrete (NSC) columns. Furthermore, the tests conducted indicated that the structural behaviour of the HSC is favorable under sustained loading, i.e., the HSC column exhibited less tendency to creep and could sustain the axial load without much increase in deformation for a longer period of time. An analysis based on a simplified stability analysis, using a stress-strain relation for concrete that includes creep, aging, and the confining effect of the stirrups was carried out. The model was shown to simulate the load-deflection curves satisfactorily for all of the concrete columns.
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| 2. |
- Fang, Congqi, 1963, et al.
(författare)
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The effect of corrosion on concrete bridges
- 2004
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Ingår i: Bridge Maintenance, Safety, Management and Cost / edited by Eiichi Watanabe, Dan M. Frangopol, Tomoaki Utsunomiya. - 9058096807
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Konferensbidrag (refereegranskat)
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| 3. |
- Grassl, Peter, 1974, et al.
(författare)
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Concrete in compression: A plasticity theory with a novel hardening law
- 2002
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Ingår i: International Journal of Solids and Structures. - 0020-7683. ; 39:20, s. 5205-5223
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the modelling of the behaviour of plain concrete in triaxial compression using the theory of plasticity. The aim is to model the load resistance and the deformation capacity in uniaxial, biaxial and triaxial compression by means of few parameters, which can be determined easily.A novel hardening law based on a non-associated flow rule and the volumetric plastic strain as hardening parameter is combined with a yield surface proposed by Menetrey and William (1995). The novel hardening and softening law differs from a classic strain-hardening law, as instead of the length of the plastic strain vector only the volumetric component of the latter is used as a hardening parameter. Thus, the non-linearity of the plastic potential is utilized to describe the influence of multiaxial compression on the deformation capacity and no additional ductility measure is required.The implementation and calibration of the novel hardening law are discussed. The prediction of the model is compared to results of uniaxial, biaxial and triaxial compression tests. It is shown that with one set of calibration parameters a good prediction of the load resistance and the deformation capacity for all three types of compression tests can be achieved.
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| 4. |
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| 5. |
- Lövgren, Ingemar, 1972, et al.
(författare)
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In-situ Concrete Building - important aspects of industrialised construction
- 2001
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 26:1, s. 61-81
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Tidskriftsartikel (refereegranskat)abstract
- In the ongoing research programme at Chalmers University of Technology, principles and methods for industrialised building with in-situ cast concrete are investigated. The goal is to increase the understanding of, and to develop methods and systems for, industrial building/construction. Improvement of in-situ concrete construction is necessary; partly in order to meet challenges from other materials. The article deals with questions of how the development should proceed and which research disciplines are needed as support. Opportunities for improvement are identified and a framework for the continuing work has been formulated.
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| 6. |
- Lövgren, Ingemar, 1972, et al.
(författare)
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In-situ concrete building - Innovations in Formwork
- 2001
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Ingår i: the 1st International Conference on Innovation in Architecture, Engineering and Construction / Anumba, C.J. , et al.. - 1897911238 ; 1, s. 93-104
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Konferensbidrag (refereegranskat)
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| 7. |
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| 8. |
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| 9. |
- Plos, Mario, 1963, et al.
(författare)
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Evaluering av bärförmåga hos broar med hjälp av förfinade analysmetoder
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this project, enhanced methods of analysis were used to demonstrate how higher load carrying capacities can be proven through detailed assessment of bridges in the Swedish road network. Probabilistic analysis, finite element (FE) analysis and alternative design methods, and combinations of these, were described and used together with results from previously performed measurements. The focus of the project has been the application on prestressed concrete box girder bridges. Two bridges owned by the Swedish National Road Administration (Vägverket) were used as case studies: The Källösund Bridge, built with the free cantilevering method as a part of the Tjörn Bridge connection on the west coast of Sweden, and a continuous three-span bridge at a traffic interchange in Kropp close to Helsingborg in the south of Sweden.An assessment strategy for enhanced evaluation of the load carrying capacity of existing bridges is proposed. As a basis for such an evaluation, an initial structural assessment according to current practice should be performed, but with higher demands on a detailed documentation. The enhanced evaluation should thereafter be made step by step and as an integrated part of the decision process. The detailed assessment involves more advanced analysis and judgement, that are not ruled by the detailed regulations and code of practice used in common structural assessment. However, it should have the same aim, intention and safety requirements. It can be based on research results and more enhanced methods for determination of the capacity, and more advanced analysis models of the bridge can be used together with bridge-specific load and material data. Calculations and analyses are made in a continuous interaction with physical investigations of the condition of the bridge, and decisions whether to proceed with the assessment are made successively.For the Källösund Bridge, the evaluation made showed that the load carrying capacity with respect to bending moments was sufficient for a vehicle bogie load of 210 kN according to the Swedish code for road bridge assessment, see Vägverket (1998). However, the capacity with respect to shear and torsion was too small for the same load level, with the existing shear reinforcement. This was still the case when load effects determined through probabilistic evaluation were used, even though they were found to be 9% lower than the load effects determined from the deterministic code loads. An evaluation based solely on the Swedish concrete code, BBK 94 (1994), gives sufficient safety in the latter case, but, on the other hand, the other methods used (EC 2-1 and the modified compression field theory) give a too low capacity. A FE analysis performed resulted in sufficient load carrying capacity for the critical load case with respect to shear and torsion, but non-linear FE analysis of shear failures need to be studied further before the results of such an analysis can be fully adopted.Strengthening of the Källösund Bridge is, based on the evaluation performed, considered to be the safest alternative. In case of further evaluation, an interesting alternative would be to leave the bridge unstrengthened and to expose it to a test loading with successively increasing vehicle loads up to the maximum load level the bridge has been exposed to earlier. Relevant strains, deformations and possibly the support reactions could be measured in order to check if the analysis models used correctly reflects the response of the bridge. Furthermore, a confirmation of the minimum load carrying capacity would be obtained. The response would be followed during the loading and the load increase be terminated if risk of damage or cracking of the webs arises. Regarding the risk of cracking due to shear at the flange to web connection, the study showed that the bridge has sufficient resistance if the classification with respect to environmental influence is reconsidered.For the bridge at Kropp, the evaluation showed that the load A/B, i.e. the axle and bogie loads according to Vägverket (1998), can be raised from 150/255 kN to about 275/630 kN, if certain assumptions were made regarding the dynamic amplification factor and the accuracy of the traffic load. The reasonableness of these assumptions needs to be further evaluated.Further research and development are needed regarding quantification of uncertainties in the modelling of material parameters, loads and structural capacity.
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| 10. |
- Plos, Mario, 1963, et al.
(författare)
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Structural assessment of a prestressed box girder concrete bridge, using non-linear finite element analysis
- 2004
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Ingår i: Proceedings of the second international conference on Bridge Maintenance, Safety and Management. - 9058096807 ; , s. 837-838
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Konferensbidrag (refereegranskat)abstract
- In this study, it was demonstrated how higher load carrying capacity with respect to shear and torsion can be shown for road bridges through non-linear finite element (FE) analyses. A prestressed box girder bridge, the Källösund Bridge, was evaluated as a case study. The Källösund bridge is a 45 years old, cast-in-situ concrete bridge with four spans, constructed with the free cantilevering method on the west coast of Sweden. The case study indicates a substantially higher load carrying capacity for combined shear and torsion, compared to bridge assessment with conventional design methods. In the non-linear analyses of the Källösund bridge, about 40% higher design bogie load than in the initial structural assessment was reached (B = 250 kN), together with the other design loads in ULS, before a shear failure developed for the studied critical load case. With improvements to the model and with deformation controlled loading, an even higher failure load is likely to be shown. However, non-linear analyses of shear failures in this kind of concrete structures are quite rare, and need to be studied further. Furthermore, the analyses performed need to be complemented for other possible critical sections, and for alternative critical load cases.
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