## 5 Application Analysis  
### Monitoring System and Sensor Layout  
We applied the dynamic analysis and monitoring optimization strategies outlined above to a reinforced concrete bridge located in Beijing. A section of the bridge is presented in Figure 3. The structure is a simply supported T-girder beam bridge with a span of 30 m. The girder has a width of 12.50 m and a height of 1.80 m, featuring an equivalent cross-sectional moment of inertia of 0.80 m\({}^{4}\). The number of traffic lanes is two. The equivalent elastic modulus is 3.53 \(\times\) 10\({}^{6}\) MPa, and the reduced density of the main beam is 3.66 \(\times\) 10\({}^{3}\) kg/m\({}^{3}\). The monitoring is carried out in normal traffic conditions.  
Figure 3: The bridge with a health monitoring system: (**a**) the monitored bridge; (**b**) schematic diagram of the health monitoring and evaluation system.  
Figure 2: Flow chart for health monitoring strategy.  
This bridge is equipped with a health monitoring system, specifically designed to observe bearing capacity and durability. Five items are considered in the health monitoring and evaluation system, namely sensing and data acquisition, data interrogation, modeling and simulation, correlation analysis and data management. Sensing and data acquisition consists of the following eight parts: monitoring strategies for damage prognosis, types of data for acquisition, required sensory systems and their properties in terms of measurable bandwidth and sensitivity, calibration and stability, sensor durability, typical numbers of sensors and locations of sensors, data acquisition/transmission/storage system and data cleaning. Data interrogation consists of the following six parts: data validation, feature extraction, data normalization, characterization of feature distribution, statistical inference for damage prognosis, and prediction modeling for future loading estimates. Modeling and simulation consists of the following two parts: types of models (numerical models, statistical models, etc.) and uncertainty analysis (environment variability, parametric variability and modeling variability). Correlation analysis consists of the following three parts: correlation of analysis-to-analysis for model verification and calibration, correlation of measurement-to-measurement for features extractions, defects detection and correlation of analysis-to-measurement for model verification and updating, performance monitoring, etc. Data management consists of the following four parts: communications among different hardware and software platforms, security, visualization and accessibility.  
Five servo-controlled accelerometers and five inclinometers were symmetrically installed on the midspan and other symmetrical positions to collect and analyze the dynamic response. The accelerometer and inclinometer are shown in Figures 4 and 5, respectively.  
The sampling rate of accelerometer is 100 Hz. The sampling rate of inclinometer is 10 Hz. Two piezoelectric thin film sensors, spaced 8 m apart, were installed in the bridge deck to collect traffic signals, as shown in Figure 6.  
Figure 4: Illustration of low-frequency accelerometers: (**a**) accelerometers before installation and (**b**) an accelerometer placed in the protecting jacket in the field.  
Figure 5: Illustration of the inclinometer.  
The sampling rate of piezoelectric thin film sensor is 100 Hz. In addition, fifteen fiber Bragg grating strain sensors were installed on the bending bottom and inside the beam to monitor the load-bearing capacity of important components, as shown in Figure 7. The arrangement of the instruments was shown in Figure 8. The sampling period was 4 months.