Shear beams in finite element modelling

Abstract

Fiber models for beam and shell elements allow for relatively rapid finite element analysis of concrete structures and structural elements. This project aims at the development of the formulation of such elements and a pilot implementation. The reduction of calculation time and degrees of freedom and the few required input variables are advantages of the reduced models making them especially popular FEM options in the engineering practice. Standard nonlinear fiber beam formulations do not account for shear effects and cannot capture all failure modes (like shear failure) and hence cannot be used in the assessment of structures with shear problems, as it may result in large overestimations of ultimate carrying capacities. Solving this handicap would provide a tool for faster and simpler nonlinear analysis that is advantageous for pre- and quick scan assessment stages. The shear-sensitive beam model to be implemented in DIANA is based on the PhD work of D. Ferreira (2013) developed at Universitat Politècnica de Catalunya, BarcelonaTECH (UPC). The present report relates to the implementation of 2D and 3D shear-sensitive beam elements in DIANA software and its validation with various benchmarks. The case-studies include the ones previously analysed in Report #1 ‘Calculation of benchmarks with a shear beam model’ (TUD/CITG/B&I/CM-2015-13). The goal of this work is to capture shear effects with beam elements (2D and 3D). In this manner, transversal reinforcement is considered and the beam model is able to compute multiaxial strains and stresses in concrete, as well, as inclined cracking. Shear failures can be captured by failure of transversal reinforcement or crushing of the diagonal concrete strut. These capabilities enlarge the range of application of the standard beam elements, which were limited to bending problems.