Health Monitoring and Evaluation of Long-Span Bridges Based on Sensing and Data Analysis: A Survey <s> Data Transmission <s> For a long time, difficult to achieve large-scale bridge long-term,online, real-time monitoring, a comprehensive study of a large-scale bridge structural health monitoring system data acquisition subsystem of design methods, content and principles of design is done, and software and hardware design of data acquisition subsystem is discussed. <s> BIB001 </s> Health Monitoring and Evaluation of Long-Span Bridges Based on Sensing and Data Analysis: A Survey <s> Data Transmission <s> A real-time wireless sensor network platform capable of maintaining lossless data transmission over several minutes of continuous, high-rate sampling is presented in this paper. The platform was designed specifically to provide the capability to enable expeditious system identification, as well as load rating of highway bridges without compromising the typical data acquisition parameters employed in comparable cable-based tests. Consequently, the hardware signal conditioning interface permits data collection from a variety of sensors typical to structural health monitoring, including accelerometers, strain transducers, and temperature sensors. The embedded software features a proprietary network transmission protocol capable of lossless, real-time delivery of up to 40 measurement channels at an effective sampling rate of 128 samples per second per channel. Documented in this paper is a field study on an end-of-service highway bridge in which ambient vibration monitoring was performed using 60 accelerometers interfaced with 30 wireless sensor nodes operating within one of two simultaneously operating star topology networks. In addition, an experimental load rating of the entire structure was performed through large-scale strain measurement facilitated by the same wireless sensor network platform. <s> BIB002 </s> Health Monitoring and Evaluation of Long-Span Bridges Based on Sensing and Data Analysis: A Survey <s> Data Transmission <s> Structural health monitoring (SHM) systems have excellent potential to improve the regular operation and maintenance of structures. Wireless networks (WNs) have been used to avoid the high cost of traditional generic wired systems. The most important limitation of SHM wireless systems is time-synchronization accuracy, scalability, and reliability. A complete wireless system for structural identification under environmental load is designed, implemented, deployed, and tested on three different real bridges. Our contribution ranges from the hardware to the graphical front end. System goal is to avoid the main limitations of WNs for SHM particularly in regard to reliability, scalability, and synchronization. We reduce spatial jitter to 125 ns, far below the 120 μs required for high-precision acquisition systems and much better than the 10-μs current solutions, without adding complexity. The system is scalable to a large number of nodes to allow for dense sensor coverage of real-world structures, only limited by a compromise between measurement length and mandatory time to obtain the final result. The system addresses a myriad of problems encountered in a real deployment under difficult conditions, rather than a simulation or laboratory test bed. <s> BIB003
Combined with the transmission distance, network coverage, communication facilities, and other factors, reasonable transmission modes of sensing information are respectively selected, which are then followed. (1) If the monitoring range is small, it shall be based on the signal synchronization technology. BIB001 If the monitoring range is large, it shall be based on the time synchronization technology BIB003 . (3) If the electromagnetic interference cannot be shielded in bridge monitoring, cable transmission shall be adopted. (4) If it is in surroundings where the layout and the maintenance of wires are difficult, or if it is necessary to build the monitoring structure which can temporarily transmit network data, wireless transmission BIB002 shall be adopted. (5) According to the needs of the projects, one or more modes can be combined.