Chapter 123 Modular Architecture of SHM System for Cable-supported Bridges Kai-Yuen Wong1 and Yi-Qing Ni2 1 Highways Department, Government of Hong Kong, China 2 Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong, China reasoning and experience so that the current and 1 Introduction 1 expected future performance of the bridge, for at least 2 System Architecture of WASHMS 2 the most critical limit events, can be predicted or evaluated. Bridge health monitoring system has been 3 Operation of WASHMS 15 adopted in the past decade to monitor and evaluate 4 Conclusions 16 the structural health conditions of cable-supported References 16 bridges in Hong Kong [1–5]. The bridge health moni- toring system in Hong Kong is referred to as wind and structural health monitoring system (WASHMS ). Bridge health monitoring system is currently consid- ered as an integral part of bridge operation, bridge inspection, and bridge maintenance and has been 1 INTRODUCTION included as a standard mechatronic system in the design and construction of most large-scale and Bridge health monitoring is the tracing of the multidisciplinary bridge projects such as Stonecut- structural health conditions of the bridge in terms ters Bridge (SCB) in Hong Kong [6], and Sutong of the physical parameters categorized as environ- Bridge [7] and Donghai Bridge in mainland China mental loads and status, traffic loads, bridge features, [8]. The experience gained in the design, installa- and bridge responses by reliably measured data and tion, operation, maintenance, and development of the evaluation techniques, in conjunction with inductive WASHMS for Tsing Ma Bridge (TMB), Kap Shui Mun Bridge (KSMB), Ting Kau Bridge (TKB), and Encyclopedia of Structural Health Monitoring. Edited by the cable-stayed bridge in Hong Kong side of the Christian Boller, Fu-Kuo Chang and Yozo Fujino 2009 Hong Kong-Shenzhen Western Corridor (HSWC) has John Wiley & Sons, Ltd. ISBN: 978-0-470-05822-0. a significant influence on the design of new structural 2 Civil Engineering Applications health monitoring systems (SHMSs) in Hong Kong the modular architecture and input/output block and in mainland China. The WASHMS in Hong diagram of WASHMS. Of these six modules, Kong, which is based on modular design concept, modules 1–3, which are the key modular systems has been improved particularly in the aspect of data for the execution of real-time structural health interpretation, health evaluation, and data manage- monitoring, are composed of different types of SSs, ment and such improvements have been incorporated data/video logging systems, cabling network systems, in the design and installation of the WASHMS for servers and software facilities for data acquisition, SCB (SCB-WASHMS) [6]. transmission, and processing. The schematic layout of typical connections among modules 1–3 is shown in Figure 2. Modules 4 and 5, which are key modular 2 SYSTEM ARCHITECTURE systems for the execution of offtime structural health OF WASHMS evaluation, are composed of servers, workstations, and software facilities for data interpretation, health The modular concept of WASHMS [9–11], which evaluation, data management, and generation of is devised to monitor structural condition and reports. Module 6 is a set of portable computers (that evaluate structural degradation as it occurs rather store the system design information and operation than to detect structural failures, is composed of and maintenance manual of WASHMS) and tools for six integrated modules, namely, module 1—sensory carrying out inspection and minor maintenance of the system (SS); module 2—data acquisition and WASHMS itself. transmission system (DATS); module 3—data processing and control system (DPCS); module 4—structural health evaluation system (SHES); 2.1 Module 1—sensory system (SS) module 5—structural health data management system (SHDMS); and module 6—inspection and The SS that refers to the sensors and their corre- maintenance system (IMS). Figure 1 illustrates sponding interfacing units for input signals gathered Wind and structural health monitoring system (WASHMS) Module 2 Module 3 Data acquisition and Data processing and transmission system control system Module 5 Structural health data management system Module 6 Module 4 Inspection and Module 1 Structural health maintenance system Sensory system evaluation system Analytical models: Bridge data and information: Finite element models Bridge design criteria Surrogate models Bridge monitoring criteria As-built bridge records Bridge inspection and Measurement quantities: Monitoring reports: Maintenance records Environmental status Instant display reports Traffic loads Detailed reports Bridge characteristics Special reports Bridge responses Bridge rating reports System inspection Data and information transmission Updating of data and information Figure 1. Modular architecture and input/output block diagrams of WASHMS. Modular Architecture of SHM for Cable-supported Bridges 3 Sensors Sensors Sensors Sensors building Administration DAU or DAU or DAU or DAU or DVC DVC DVC DVC DPCS DAU or DAU or DAU or DAU or DVC DVC DVC DVC Sensors Sensors Sensors Sensors DAU Data-acquisition unit Bridge site DVC Digital video converter DPCS Data processing and control system Global cabling network system—ring-type single mode optic fiber Figure 2. Schematic layout of module 2—data acquisition and transmission system. from various monitoring equipment and sensors is correlated or compared with the design values; (ii) the categorized into four groups: (i) sensors for moni- SS is required to integrate the predictive modeling toring of environmental loads and/or status, which and data interrogation processes with the sensing include anemometers (three-dimensional ultrasonic system design process; (iii) the SS should have the type and two-dimensional propeller type), tempera- function to acquire data in a consistent and retriev- ture sensors (for the measurement of temperatures in able manner for long-term statistical data processing respective air, asphalt pavement sections, structural and analysis; (iv) all sensors should be chosen from concrete sections, structural steel sections, suspension the contemporary commercially available sensors that cables, and stay cables), corrosion cells, hygrome- best match the defined sensing performance require- ters, barometers, and rainfall gauges; (ii) sensors for ments; (v) the SS should include additional measure- monitoring of traffic loads, which include dynamic ments by removable/portable sensors to quantify weigh-in-motion stations, digital video cameras, and changing operational and environmental conditions; dynamic (weldable foil type) strain gauges; (iii) and (vi) at key locations, different types of sensors sensors for monitoring of bridge characteristics, should be deployed so that cross calibration of sensors which include fixed and removable/portable servo- could be carried out. type accelerometers, global positioning systems, level The major parameters monitored by each type sensing stations, and dynamic strain gauges; and of sensors are listed in Table 1. Figures 3–7 illus- (iv) sensors for monitoring of bridge responses, trate the layouts of the SSs in TMB, KSMB, which include dynamic strain gauges, static (vibrating TKB, HSWC, and SCB on their respective full wire type) strain gauges, displacement transducers, three-dimensional finite element models, which are global positioning systems, tiltmeters, fixed servo- built by MSC-PATRAN. The layouts of the SSs type accelerometers, buffer sensors, bearing sensors, as shown in Figures 3–7 are deployed or arranged and elastomagnetic sensors. in such a manner that the measured raw data can In the design/selection of the types and locations be used to derive the information or parameters of SSs, the following six basic criteria should be as listed in the fourth column of Table 1. These fulfilled: (i) the SS should have the ability to capture derived information and parameters are then used to the local- and system-level responses, which could be compare/correlate with (i) the corresponding bridge 4 Civil Engineering Applications Table 1. List of required sensory systems and physical parameters for processing and derivation Monitoring Physical Required types of Physical parameters for category quantity sensory systems processing and derivation Environments Wind load • Ultrasonic-type anemometers • Wind speed and wind direction plots monitoring • Propeller-type anemometers (time-series data) • Barometers(a,b) • Wind speeds (mean and gust) and • Rainfall gauges(a,b) directions (histograms) • Hygrometers(a,b) • Terrain factors and wind speed profile plots • Wind rose diagrams • Wind incidences at deck level • Wind turbulence intensities and intensity profile plots • Wind turbulent time- and length-scale plots • Wind turbulent spectrum and cospectrum plots • Wind turbulent horizontal and vertical coherence plots • Wind response and wind load transfer function • Wind-induced accumulated fatigue damage • Histograms of air pressure, rainfall, and humidity Temperature load • Platinum resistance • Effective temperatures in towers, deck, and monitoring temperature detector (RTD) cables type for temperature • Differential temperatures in deck and tower measurements in structural • Air temperatures and asphalt pavement steel, concrete, asphalt temperatures pavement, and air • Temperature response • Thermocouplers for cables • Temperature load transfer function Seismic load • Fixed servo-type •