Comparative Evaluation of Excitation Schemes for Multi-Shaker Testing of Bridges

Abstract

Many researchers are working to develop more rational, robust and timely condition evaluation approaches for the nation’s inventory of aging and deteriorating bridges. Dynamic characterizations of bridges using forced or ambient vibration testing techniques have received much attention in this regard since the measurements can effectively capture and describe the actual in situ properties and behavior of the structure. The dynamic excitation is an important consideration for bridge vibration testing applications. It is challenging and expensive to adequately excite a full-scale bridge for forced vibration testing using one or two traditional dynamic shakers, and ambient vibration testing requires assumptions related to the nature of the unmeasured dynamic excitation that cannot be easily validated. The writers have been evaluating a new approach for multiple-input, multiple-output forced vibration testing of short to medium span bridges that employs a spatially distributed network of low-cost exciters. Forced vibration testing of a large-scale, laboratory model structure was performed using the prototype multi-shaker excitation system to identify the optimal dynamic excitation signals. Deterministic multisine signals and stochastic burst random signals with various durations and force levels were evaluated with the system. The resulting system identifications and the merits of the different excitation signals are presented and compared.