REASONABLE DISCRETE ELEMENT LENGTH OF FORCE-BASED NONLINEAR BEAM-COLUMN ELEMENTS

Force-based nonlinear beam-column elements are frequently used in structure nonlinear analysis. In this study, the reasonable discrete element length and the corresponding integration point number are derived theoretically to eliminate computational errors. Subsequently, a numerical model is established, using the OpenSees finite element program, for a set of single-pier cyclic pushover tests. The derivation is verified by comparing both the force-displacement hysteresis curves for load point and the section curvature hysteresis curves at the pier bottom. Results show that: the discrete element length should be determined on the basis of the integration point number when force-based nonlinear beam-column elements are used, and the relationship between the discrete element length and the integration point number is to ensure the length of plastic curvature increments in FEM equal to the plastic hinge length in the actual structure. In practice, the equivalent plastic hinge length can be used to pre-calculate the reasonable discrete element length. If the aforementioned relationship is ensured, the more force-based nonlinear beam-column element integration points are employed, the more reliable the results are.