| The effect of earthquakes on reinforced concrete structures is uncertain due to its duration, frequency of occurrence, and intensity. Reinforced concrete bridges with eccentric loadings, unsymmetrical geometries, skewed, curved, or with unequal spans and column heights can be subjected to combined axial, flexure, shear and torsion loads during earthquakes. The analytical modeling of the behavior of structures under axial, bending, shear and torsional loads is complex; and failure can potentially be at lower ductility levels. The effect of these loadings on structures can be accurately simulated using the finite element method providing their interaction is properly accounted for.;The proposed model is formulated to address the interaction between the axial force, shear, bending, and torsion loads. The shear mechanism along the beam is modeled by adopting the Timoshenko beam approach for two dimensional (2-D) and three dimensional (3-D) frame elements with arbitrary cross-section geometry. The problem consists of solving a system of equations by combining the equilibrium and compatibility conditions, and constitutive laws of the materials at the section and structural level. The concrete constitutive model follows the Softened Membrane Model (SMM) with a tangent-stiffness formulation. The validity of the model is established through a correlation study of experimentally tested reinforced concrete bridge piers and shear walls subjected to static, reversed cyclic, and dynamic loading conditions. |
