FINITE-ELEMENT MODEL FOR THIN-WALLED SPACE FRAME FLEXIBLE CONNECTION BEHAVIOR

A finite-element formulation for modeling flexible connection behavior in space frames composed of thin-walled members is presented. The fin ite-element model is based on a distributed linear spring representati on over the physical contact area of the connection that is capable of representing translational, rotational, and warping deformations of t he connection. Second-order geometric and nonlinear moment-rotation re sponse of the connection is considered. An updated Lagrangian formulat ion is used to model second-order geometric nonlinear effects. A Rambe rg-Osgood representation is used to model the nonlinear moment-rotatio n connection behavior. Details for transforming the resulting stiffnes s equations for connection-to-member eccentricities are included. Resu lts for a cubic, portal space frame composed of I-section and C-sectio n members are presented to demonstrate the versatility of the develope d element.