The effect of joint deformations on steel plane frames behaviour

A very simple model for the behaviour of the panel zone of welded beam-to-column joints is proposed in this work, to the aim of studying the possibility of dissipating the energy input by a strong earthquake not only in beam end zona but also in joint pannel. A relation for the hysteretic behaviour of the panel zone is then proposed, in terms of the average shear stress-strain; this relation, based on experimental data, is capable to reproduce the cyclic behavious of the joint under alternate loadings, as those due to the earthquake. The joint model, together with a nonlinear 2-D beam element, has been implanented in a computer code, perfonning a nonlinear static incremental analysis in displacement control, and the analytical response of a prototype story subassembia e has then been determined for different values of the ratio between the strength of the beam and that of the joint.