Instrumentation and health monitoring of cable-supported bridges

Instrumentation and health monitoring of cable-supported bridges in Hong Kong involve the integration of instrumentation, analytical and information technologies with knowledge and experiences in design, construction, operation and maintenance of cable-supported bridges for continuous monitoring of performance throughout their life-span. A bridge health monitoring system, called the WASHMS (wind and structural health monitoring system) has been devised and operated by Highways Department to monitor the structure conditions of the Tsing Ma (suspension) Bridge, the Kap Shui Mun (cable-stayed) Bridge and the Ting Kau (cable-stayed) Bridge. The main objective of instrumentation and health monitoring is to detect and evaluate any symptoms of operational anomalies and/or deterioration or damage that may induce adverse effects on service or safety reliability through the processing and analysis of data collected from transducers and sensors. This WASHMS is composed of six modules, namely, the sensory system, the data acquisition and transmission system, the data processing and control system, the bridge health evaluation system, the portable data acquisition system and the portable inspection and maintenance system. The monitoring items are in general classified into three categories, namely, the loading sources (or input parameters) which include: wind, temperature, traffic (highway and railway) and seismic loadings; system characteristics (or system parameters) which include: static influence coefficients and global dynamic characteristics; and bridge responses (or output parameters) which include: variation in geometric configuration (or displacements of the bridges), stress/strain distribution, cable forces and fatigue stress estimation. This paper introduces the system architecture of the WASHMS with a brief functional description of each module. Categorization of the monitoring parameters and corresponding monitoring procedures are also outlined. The applications of the monitoring results are illustrated by some typical graphical plots such as wind-rose diagrams, spectral analysis, bogie loading and remaining fatigue life assessment. For successful design and operation of a bridge health monitoring system, conclusions are drawn with reference to the integration of knowledge and experience in four aspects: (i) design, construction, operation and maintenance of long-span bridges; (ii) instrumentation technologies for collection and processing of data; (iii) graphical CAD and numerical analytical technologies for modeling and analysis; and (iv) information technologies for transmission, processing and visualization of data. Copyright © 2004 John Wiley & Sons, Ltd.