2-D Finite Element Analysis of Massive RC Structures

Nonlinear analysis of concrete structures using finite elements is discussed. The applications include a thick-walled top-closure for a pressure vessel as well as the delicate problems of beams failing in shear. The top-closure analysis evaluates the effect of two different failure criteria and modeling of a realistic post-failure behavior is demonstrated to be mandatory for accurate structural predictions. For shear beams it is shown that the primary cause of failure is strain softening adjacent to the load point. This softening causes a strain localization which in turn results in a tendency toward diagonal cracking. Stirrups prevent this tendency and a shear-compression failure follows. Otherwise, a diagonal tension failure results. This again highlights modeling of strain softening. The influence of the shear retention factor is found to be relatively moderate. Variation of the uniaxial tensile strength influences the results insignificantly. Modeling of secondary cracks is found to be essential. Finally, it is shown that dowel action must be treated through the bending of the bars and not through their shear deformation.