Instability and collapse of flexibly-connected gabled frames

Abstract

A nonlinear elasto-plastic instability analysis of flexibly connected and supported gabled frames with uniform and nonuniform geometry is presented. The analysis incorporates stability and strength. The procedure is based on nonlinear kinematic relations and linearly elastic material behavior except at the plastic regions (concentrated plasticity). The nonlinear flexible connections are represented by polynomial models. Thus, various types of response can be predicted. Through the chosen examples, the following types of response have been observed: elastic bifurcation instability, elastic limit point instability, elasto-plastic limit point instability and plastic collapse. The effect of several parameters is assessed in order to enhance our understanding of frame behavior. These include the effects of nonuniform geometry, of rotational restraints at the supports, of rise to span ratio, of beam to column stiffness ratio, of load eccentricity and of joint flexible connections.