Plasticity model for reinforced concrete elements subjected to overloads

This paper presents a theoretical and computational framework for the analysis of structures that are subjected to inelastic static or dynamic overloads. Current practice in structural engineering assumes elastic material response for the analysis but applies the resulting solutions to design methods that are based on elastoplastic or perfectly plastic material response. This approach generates inaccuracies which, depending on the amount of overload, can be excessive because force distributions within statically indeterminate structures depend on the relative stiffnesses of the individual structural elements (i.e., beams and columns). The relative element stiffnesses within a structure change continuously under inelastic loading and can be significantly different from their initial elastic values. For this purpose, a new plasticity model that combines the nonlinear material response and the geometric characteristics of a structural element is developed. The model provides the computational efficiency and simplicity of matrix structural analysis and avoids modeling at the material level. Alternative analysis would require very expensive 2D or 3D finite-element computations using solid elements.