Static analysis of flexibly connected thin-walled plane frames

Abstract

The static response of plane frames including nonlinear semi-rigid connection behavior, post-local-buckling strength of thin-walled steel members and first-order geometric nonlinearity is presented. Semi-rigid connection behavior is modeled using an exponential approximation of the connection flexibility-moment relationship. Post-local-buckling behavior is approximated using an effective width concept. Both axial and bending stresses are included in the direct iteration scheme used to calculate the cross section properties for the locally buckled members. Discretization of the nonlinear equilibrium equations is based on an exact elastic stiffness matrix formulation coupled with a finite element representation of first-order geometric nonlinearity. Solution of the resulting nonlinear algebraic equations is obtained using an iterative predictor-corrector strategy along with a constant spherical arc-length constraint algorithm for the automatic selection of the load step increments. Numerical results are presented for a two story, two bay frame which demonstrate the influence of flexible connections, local buckling and/or beam-column, P-delta secondary moments.