The Telegraph Road Bridge (TRB), a multi-girder steel composite bridge located in Monroe, MI, has been selected for installation of a permanent wireless sensor network designed to monitor the acceleration and strain response of the bridge to traffic and environmental loads. The sensing strategy of the wireless monitoring system is designed to target specific deterioration modalities commonly encountered in steel girder-concrete deck bridges located in the harsh northern climates of the United States. The wireless sensor network on the bridge is interfaced to the Internet via a cellular modem so that raw sensor data from the bridge can be stored in a scalable database system called SenStore. SenStore combines sensor data with bridge design information (e.g., geometric details, material properties) and exposes application programming interfaces that permit data processing tools to extract information from bridge data.
In this study, a low-cost wireless sensing platform has been used to permanently instrument a long-span bridge for long-term monitoring of structural behavior under normal operational loading profiles including exposure to wind, temperature and traffic loads. The Alfred Zampa Memorial Bridge (also termed the New Carquinez Suspension Bridge) located in Vallejo, California was instrumented to monitor bridge accelerations, strains, and displacements. In addition, the wireless monitoring system was used to indirectly monitor thermal and wind loads by measuring temperature and wind characteristics (i.e.,direction and speed) respectively. The study’s primary focus is on the autonomous extraction of modal characteristics of the bridge using the outputonly stochastic subspace identification (SSI) method. Using extracted modal frequencies, relationships are presented between the modal characteristics of the bridge and environmental parameters such as temperature and traffic activity.