Diagnosis and prognosis of Stonecutters Bridges based on structural health monitoring system

As a critical type of infrastructure in modern society, long-span bridges always draw considerable attention to their serviceability and safety. However, they are still exposed to substantial uncertainties in their long service life, e.g. performance deterioration due to harsh environment, potential failure due to unexpected natural and manmade hazards. Therefore, structural health monitoring (SHM) system has been embraced worldwide as an efficient means to provide long-term diagnosis and prognosis of bridge conditions and reliabilities. For example, a comprehensive SHM system has been recently installed on Stonecutters Bridge by Hong Kong's Highways Department, and it is composed of totally 1,571 sensors in 15 different types. Such an SHM system would considerably improve the accuracy of long-term diagnosis and prognosis of the bridge health in the sense that: (1) it provides comprehensive and real-time information of various loads, bridge conditions and bridge response; (2) it provides an efficient way to validate and update the finite element model (FEM) used; and (3) it is able to timely capture any unexpected catastrophic events and consequent structural change. This paper summarizes the work on the safety evaluation of Stonecutters Bridge under extreme events based on the installed SHM systems. The paper comprises three major parts: (1) establishing and updating the FEM of Stonecutters Bridge according to the field measurement data; (2) predicting seismic performance of Stonecutters Bridge under non-uniform ground motions at multi-supports, in which conditional simulation of ground motions based on measured records at limited points takes into account the effect of wave passage, local soil conditions and incoherence; (3) performing fully coupled buffeting analysis of Stonecutters Bridge under non-stationary typhoon, in which time-varying features of mean wind speed and evolutionary power spectra density extracted from filed measurement are appropriately considered. The latter two analyses employ the SHM-oriented FEM developed in Task 1. The effects of non-uniform seismic ground motions and non-stationary typhoon loads on the bridge's response and safety are discussed based on the comparison with conventional methods considering either uniform seismic ground motions or stationary wind loads.