Bridges have received much attention because of their high cost, long service life and the safety of people. In order to avoid catastrophic accidents caused by difficulty in detecting structural and system damage, bridge structure health monitoring is particularly important.
Among the bridges in the world where there are no accidents, there are also many bridges with varying degrees of performance degradation. According to the literature, there are nearly 600,000 bridges in the United States, and the statistics of the US Federal Highway Administration indicate that about one-third of the bridges are old or structurally flawed and need to be repaired. It is estimated that the investment needs to be 70 billion US dollars. 150-200 bridges collapse every year; in the UK, one-third of the bridges are reported to be repaired; in Canada, it is estimated that $500 billion will be spent on repairing all damage to the bridge; by the end of 2006, China’s existing There are 533,600 modern bridges, including 340,000 highway bridges and 180,000 railway bridges. With the increase of traffic volume and the continuous increase of vehicle load, combined with the lack of routine maintenance, many bridges are in a state of overload with disease, and more old bridges arrive or are about to reach the design service period.
Large bridges are the lifeblood of the country or region. It is costly. In the event of a bridge collapse, it will cause significant personal injury and death, huge economic damage, and adverse social impact. In order to grasp the performance degradation of large bridges in time and prevent sudden collapse accidents, it is necessary to apply scientific methods to monitor the health of large bridges. At present, this has gradually gained the academic, engineering and government departments. Widely recognized.
In the long-term operation of modern long-span bridges, due to the repeated effects of loads, the shrinkage and creep of concrete, temperature changes, the decline of foundations, the cracking corrosion of reinforced concrete and other factors, the geometry of the bridge structure changes. The strength of the structural members is attenuated, which causes the stress and strain changes at each test section. Conversely, the bridge with excessive fatigue will affect the safety of the vehicles on the bridge, so the long-term, remote, real-time and online health of the bridge structure is carried out. Automatic monitoring is of great significance for the long-term operation of bridges. The main part of the bridge's strain monitoring system is the acquisition and control of the bridge stress signal. Based on the detailed analysis of the stress monitoring system characteristics of the bridge structure, the FPGA embedded technology and the wireless network technology are combined, and the bridge stress acquisition module is realized. Bridge stress data acquisition and A/D conversion, stress data is serialized to GPRS DTU, then converted to TCP/IP data packet, transmitted to the Internet via GPRS network using GPRSDTU and then sent to the remote Web server to realize bridge stress data. Real-time remote detection and monitoring.
GPRS (General Packet Radio Service) is an abbreviation of General Packet Radio Service, which is a packet-switched data bearer and transmission method developed on the basis of GSM. Compared with the original GSM, GPRS has the advantages of high rate and real-time online in the bearer and support of data services. In addition, the GPRS charging method is more flexible, and supports charging according to data traffic; and GPRS can also support voice calls while performing data transmission, etc. Compared with wireless data communication services such as short messages, the price of GPRS has considerable price. Advantage. At present, China Mobile's GPRS Internet service has a maximum of 3 cents per kilobyte, and users can further reduce the cost of GPRS communication in various forms such as monthly rent and monthly subscription according to their own needs.
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