Modeling of joints for the dynamic analysis of truss structures

Abstract : A method for modeling joints to assess the influence of joints on the dynamic response of truss structures has been developed. The analytical models, which are based on experimental joint load-deflection behavior, use springs and dampers to simulate joint behavior. An algorithm for automatically computing nonlinear coefficients of the analytical models is also presented. The joint models are incorporated into a nonlinear finite-element program through use of special nonlinear spring, viscous, and friction elements. Next, the effects of nonlinear joint stiffness, such as dead band in the joint load-deflection behavior, are studied. Linearization of joint stiffness nonlinearities is performed to assess the accuracy of linear analysis in predicting nonlinear response. Viscous and friction damping are then used to show the effects of joint damping on global beam and truss structure response and equations for predicting the sensitivity of beam deformations to changes in joint stiffness are derived. In addition, the frequency sensitivity of a truss structure to random perturbations in joint stiffness is discussed and results are shown which indicate that average joint properties may be sufficient for predicting truss response.