With the development of national economy, the concept of bridge construction in China has gradually changed from "reconstruction to light maintenance" to "lifelong management and maintenance". The service life of the bridge occupies almost the whole life of the bridge. It is of great significance to pay attention to the state of the bridge in service and ensure that the bridge is in good service at all times to ensure the safety of people's lives and property. Taking a long-span reinforced concrete arch bridge as the research object, the design of its health monitoring system is studied, which has reference significance for similar bridges.
2. Overview of bridges
The total length of reinforced concrete arch bridge is 493. 14m. Layout of bridge span: 9×20m+220m+4×20m, width of bridge deck: 2× (net 1 1+2×0.5m wall guardrail). The main hole is an articulated cantilever box arch with equal cross section, and the cross section is a three-chamber box. The arch axis coefficient m= 1.543, the clear distance L=220m, the clear height f=40m, the rise-span ratio f/L= 1/5.5, and the buildings above the arch are13x17. Design load: steam -20, hook-120. Design flood frequency:1/300; Seismic intensity: 6 degree zone, 7 degree fortification.
3. Design of health monitoring system
3. 1 health monitoring system positioning
The arrangement of common bridge health monitoring systems can be mainly divided into these levels, namely: a comprehensive online real-time health monitoring system; Online and offline health monitoring systems; Special online real-time health monitoring system.
Level 1: comprehensive online real-time health monitoring system.
According to international standards, the bridge is systematically monitored. The sensor system has comprehensive layout, many measuring points, strong system function and high reliability. Adopting the most advanced and mature sensors and equipment in the world ensures the advanced and durable monitoring system, but the cost is relatively high.
Level 2: Online and offline health monitoring system.
The combination of online and offline health monitoring system has the advantages of moderate number of measuring points and high system reliability. Adopt advanced and mature sensors and equipment at home and abroad to ensure that the monitoring system is advanced and durable and the project cost is moderate.
Level 3: dedicated online real-time health monitoring system.
This level of health monitoring system simplifies the layout of the sensor system, selects some key contents for monitoring, with fewer measuring points, good domestic production technology of sensors and equipment, high cost performance, convenient maintenance and replacement in the future, excluding manual inspection system, and low project cost.
Level 4: Offline Health Monitoring System
The fourth-class system is mostly suitable for small and medium-span bridges, or it is selected under the condition of insufficient funds. Generally, the response of the bridge is tested on site regularly, and then the structure is evaluated according to the test results, and suggestions for maintenance and management are put forward.
For this bridge, the structural form of the bridge is complex and the structural importance is high, but the cost of the first-level health monitoring system is too high, so the second-level combination of online and offline is more suitable for this bridge. The design of online and offline health monitoring system for this bridge is studied below.
3.2 Health monitoring and testing items
Based on the secondary health monitoring system.
3.3 Design of data transmission system
Data transmission is an important part of bridge monitoring system. Data transmission adopts a combination of wired and wireless transmission: wired connection is adopted for field networking; The field test data is transmitted to the remote control center and the whole network transmission system through the remote data transmitter.
3.4 Interface design of health monitoring software
Bridge health monitoring is inseparable from the development of monitoring software, and the software system of health monitoring needs to have the functions of data display, data query, structural early warning and issuing monitoring reports.
4. Conclusion
A health monitoring system of reinforced concrete arch bridge is designed, and the grade selection, test content, measuring point layout, data transmission and health monitoring software interface design of health monitoring are discussed, which is beneficial to the health monitoring of long-span reinforced concrete arch bridge.
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