Numerical Modeling of Compound Element for Static Inelastic Analysis of Steel Frames with Semi-rigid Connections

Abstract

The effect of geometric nonlinearity and material nonlinearity in the analysis of semi-rigid jointed steel frame is investigated. Nonlinear analysis of semi-rigid jointed frame is carried out using general purpose finite element software SAP-2000 NL. In the numerical model, Link elements and one dimensional beam elements are adopted. A compound element modeled with a Link element is considered to take care of combined effect of semi-rigid connection and material nonlinearity (member inelasticity). In the study, semi-rigid connections are simulated by its linear, multi-linear or nonlinear moment-rotation curve and member inelasticity is simulated by plastic hinges. Also, elastic analysis is carried out to study the independent and combined effects of semi-rigid connections, geometric nonlinearity and material nonlinearity. The verification and application of the simplified numerical model developed in the present study are demonstrated by considering three different examples. Results in terms of beam moment and nodal displacement are presented for both inelastic and elastic analyses. The influence of connection nonlinearity is observed to be predominant in comparison to material and geometric nonlinearity. From the force displacement curve, it is observed that presence of semi-rigid connection changes the sequence of plastic hinge formation.