Mechanical modeling of semi-rigid joints for the analysis of framed steel and composite structures

Abstract

Some mechanical models of semi-rigid joints are analyzed, taking into account the behavior of the joint with actual dimensions. A new model is described that can be used with available software for the analysis of framed steel-structures. Semi-rigid connection is a type of moment connection for which the initial angle among the connected members, at the intersection of their axes, changes with the connection moment. This chapter describes the different types of joint deformation modes:deformation caused by pure bleeding, deformation caused by pure shear, and deformation of the connection and the column regions opposite to the beam flanges, analysis of some existing semi-rigid joint mechanical models— for example non-displaced rotational spring model, displaced rotational spring model, etc., new proposal for semi-rigid joint mechanical modeling and finally the transformation problems between finite and infinite joint-models. The joint is an infinite small point. Based on this concept, the first mechanical model used to represent a semi-rigid connection consisted of a rotational spring placed between the end of the beam axis and the column axis as used in EC3 Annex J. Because of the local deformations that arise when column web stiffeners are absent and because of the bending and shear deformations of the column zone between the upper and lower-beam flanges (joint zone), the more general concept of semi-rigid joint is introduced.