Enriched Timoshenko beam finite element for modeling bending and shear failure of reinforced concrete frames

Abstract

In this work, we present a new finite element for Timoshenko beam model that enables a very efficient computation of the ultimate limit load for reinforced concrete frames. The proposed stress-resultant model combines the descriptions of the diffuse plastic failure in the beam and the localized failure with creation of the corresponding plastic hinges representing both bending and shear failure mechanisms. The latter requires introducing the corresponding enhancement of the beam finite element kinematics by using the rotation and displacement discontinuities. Such an enhancement is formulated in the appropriate variational framework with the numerical implementation placed in the framework of incompatible mode method. The proposed model is shown to be capable of enforcing the mesh objectivity of the post-peak response computations. The results of several numerical simulations are given in order to illustrate a very satisfying performance of the proposed methodology for ultimate limit load computation of reinforced concrete frames.