The development of reliable analytical models is§essential for the advance of performance-based§earthquake engineering in the design of new§structures and in the seismic condition assessment of§existing structures.§This book describes the formulation of a beam finite§element model for the analysis of shear critical§steel and reinforced concrete (RC) structural members§under monotonic and cyclic loading conditions. The§element is based on a mixed formulation with three§independent fields and exhibits numerical stability§and robustness under cyclic loading conditions. The§validity of the proposed beam element is confirmed by§correlation studies of its nonlinear response with§experimental results from steel shear links, slender§RC beams and columns, and RC shear walls of moderate§to low span to depth. The model proves capable of§representing very accurately the global response, the§failure mode, and several local response measures of§each specimen. The efficiency of the element§formulation makes it suitable for the seismic§response analysis of large structural systems.