<p>One of the most significant challenges in structural civil engineering is accurately modeling the nonlinear behavior of structures under various loading conditions. To address this challenge, it is essential to consider three fundamental variables in mathematical modeling: the type of structural element, the material properties, and the complexity of the model used. In this context, the present investigation compares the structural responses of several reinforced concrete wall specimens, both with regular and irregular sections, subjected to complex loading protocols. Different two-dimensional material models, such as the fixed angle approach (FSAM) and the rotation angle approach, are evaluated using a novel computational element called the Membrane Element with Fibers in 3D (MEFI-3D). This element has been designed to predict the nonlinear behavior and response of three-dimensional reinforced concrete (RC) wall systems. In addition, this research presents the implementation of this novel element, MEFI-3D, in the open-source analysis software OpenSees (Open System for Earthquake Engineering Simulation). The element uses four nodes with a total of 24 degrees of freedom (DOF), encompassing six DOF per node (three translations and three rotations). The formulation employs a tangent stiffness matrix approach, effectively coupling nonlinear membrane effects with linear bending effects, addressing shear-flexure-compression interactions within the plane of the element. The study demonstrates that the MEFI-3D element is a reliable tool for predicting both global and local nonlinear responses of reinforced concrete walls based on different loading conditions, quadrature points and material approaches, thus MEFI-3D offers a promising advance in predicting the complex behavior of three-dimensional reinforced concrete walls contributing to more efficient and accurate structural analyses.</p>