Evaluation of stiffness of semi-rigid joints in pultruded profiles from dynamic and static data by using model updating technique

A model updating technique with static and dynamic data has been applied to identify the stiffness of bolted joints for pultruded framed structural systems used in civil construction. The real behavior of the joints in pultruded framed structures is semi-rigid, which will influence the response of the structure as a whole. Knowledge of the joint behavior allows an adequate degree of safety for the ultimate and serviceability limit states in the design process. By modifying the design variables (joint stiffnesses) of the numerical model, a problem of parametric identification can be formulated. Unknown stiffnesses are identified by a technique of model updating from dynamic and static tests, based on the minimization of the response residuals (frequencies/mode shapes and static deformed shapes), which express the distance of the mechanical behavior between the model and the real structure. Practical aspects concerning model updating procedure are presented, such as the finite element modeling and the robustness of eigensolutions to the parameter uncertainty. Results obtained by experimental tests show the efficiency of the proposed approach.