Nonlinear analysis of RC members subjected to combined bending-shear-torsion stresses: a numerical multi-fiber displacement-based finite element model with warping

International audience; An enhanced multi-fiber beam-column element suitable for the analysis of reinforced concrete members including the torsional effect is presented in this paper. The model is developed based on displacement formulation with the assumptions of small displacement. The section kinematics is based on the assumptions of a two-node Timoshenko beam and enhanced by introducing additional degrees of freedom at each section in order to take into account the warping phenomenon. For this, a system of fixed points is created and interpolated by Lagrange functions and polynomials. To take into account the effect of stirrups, a discretization of control sections into regions following its material response is applied. The basic assumption of the modified compression field theory with a secant-stiffness formulation is used to represent the constitutive material model for reinforced concrete. The model is validated by comparison with analytical solutions and several experimental tests. The simulations include a variety of monotonic load conditions under bending, shear and torsion for specimens with rectangular sections.