Shear and Torsion in Concrete Structures Non-linear Finte Element Analysis in Design and Assessment

Doctoral thesis, 2008

For structural design and assessment of reinforced concrete members, non-linear finite element analysis has become an important tool. However, design and assessment of shear and torsion are still done with simplified analytical or empirical design methods. Modelling methods used to simulate response due to bending and normal forces are well established and verified. The reliability of modelling methods used to simulate response due to shear and torsion, on the other hand, are more often questioned. This study shows how recognized material models implemented in a commercial finite element code can be used to simulate the non-linear shear response in concrete members, both with and without shear reinforcement. Apart from improving the knowledge and understanding of shear and torsion, the aim is to improve the traditional design and assessment methods and to give guidance for the evaluation of response and load-carrying capacity by using advanced non-linear finite element analysis. Modelling methods for non-linear finite element analysis of the shear response and load-carrying capacity of concrete structures subjected to shear and torsion were worked out and verified by comparison with tests. Furthermore, these modelling methods were applied to hollow core units, hollow core floors and a prestressed concrete box-girder bridge. The modelling methods include relevant simplifications to avoid analyses that are too time-consuming. Combining solid or shell elements, in the parts of the structure where failure is expected, with beam elements elsewhere, was shown to be a reasonable modelling level with regard to the desired level of accuracy. The modelling methods proposed can be used separately or in combination with conventional methods to improve the design or assessment of complex structures with arbitrary geometries and loads, when failure due to shear and torsion is the main problem. The modelling methods have shown great potential to reveal higher load-carrying capacity than conventional approaches. Further, the methods have been helpful not only in understanding the behaviour of concrete members subjected to shear and torsion but also to see how analytical methods can be used more correctly. Much can be gained by using these methods instead of or together with traditional design methods.