Design and assessment for shear and torsion in prestressed concrete bridges A state-of-the-art investigation

Rapport, 2006

By using non-linear finite element (FE) analysis, a higher load carrying capacity can be shown for many bridges. The work presented in this report is part of a project that aims to develop enhanced methods and guidelines for design and assessment with respect to shear and torsion in prestressed concrete bridges. The aim of this work is to present, shortly, the analytical methods available for predicting the shear and torsion capacity and, to investigate the use of the non-linear finite element method to analyse the shear and torsion response of reinforced concrete members in general and of concrete bridges in particular. Tests of reinforced concrete members subjected to shear, torsion or both, reported in the literature, which could be used to evaluate and verify non-linear finite element analysis methods are also presented. Full-scale tests on reinforced concrete structures subjected to shear, torsion or both, which could be of interest to use for evaluation in this project, are summarised in this report. This includes shear panel tests, shear beam tests, torsion beam tests, shear and torsion beam tests, and tests on bridges. Both shear forces and torsional moments are after cracking transmitted by compression in the concrete between inclined cracks, tension in the transverse reinforcement crossing the inclined crack, tension in the longitudinal reinforcement, compression in the compressive zone and shear transfer in the crack. Today, design and assessment for shear and torsion are made using simplified design methods based on sectional forces and moments. These methods, for example the truss model, only predict the shear capacity at failure, and they are calibrated against tests on relatively small laboratory beams. There exists enhanced design methods for shear and torsion, but these are still based on sectional forces and moments. These methods, for example the modified compression field theory, predict the non-linear shear behaviour. Another way is to use non-linear finite element analysis to predict the behaviour of concrete structures. Some material models available for non-linear analysis of concrete are shortly described in the report. Furthermore, non-linear analyses of reinforced concrete structures subjected to shear and torsion found in the literature are summarised. The number of references within the area of structural design and assessment of concrete bridges, using non-linear finite element analysis, is rather limited and mainly associated with bending and normal forces. In several cases a more favourable load distribution, compared to conventional analysis, has been found. Analysis results indicate that the response may vary significantly depending on support conditions and material properties.