Effect of member length on the parameter estimates of joints

Abstract

Concept models of joints are used in the early stages of structural design because they are more economical and practical than detailed models. The concept joint models usually use torsional springs. The magnitudes of torsional spring constants and the positions and orientations of torsional springs can be used as parameters in order to account for the flexibility, location of rotation centers, and coupling effect of joints, respectively. These parameters are usually identified using the results of experiments performed on a substructure that contains a joint itself and the attached members. However, the estimates of parameters may change with the length of the attached members. This is due to the fact that the magnitude of the shear deformation of the cross sections of the joint members changes with the length of members. The effect of member length on the parameters of the concept joint models is studied using system identification as well as decomposition of the total deformation of the substructure into contributions from a joint itself and the attached members. The study is applied to a T-shaped joint made of simple box beams and to a joint in a real automotive body structure.