Determination of Target Modes for Monitoring the Stiffness of Cable Domes Considering Random Pretension Deviations

Abstract

Dynamic modal testing is an economical method of evaluating structural key stiffness, the accuracy of which relies on the determination of selected target modes. Pretension deviations are usually inevitable in cable domes; their stiffness, however, depends highly on the pretensions in the system. The target modes thus cannot be determined effectively based only on idealized numerical models regardless of pretension deviations. A method is proposed to select the target modes based on the idealized numerical model and to accomplish its expansion based on perturbed structural models considering the randomness of pretension deviations. The sensitivity relationships between member length errors and their effect on eigenvalues and mode shapes are established. For the prescribed error limits on member lengths, the possible variations of target modes obtained based on the idealized numerical model can be distinguished. To monitor the key stiffness, a two-step strategy for expanding the assembly of target modes is suggested by considering the mode shape change and mode jumping. An illustrative Geiger cable dome is employed to investigate the validity of the target mode determination method put forward in this paper.