Application of monitoring technology in bridge construction?

In recent years, the growth rate of domestic traffic volume is amazing. Based on this, many long-span bridges have been put into use, among which suspension bridges are the most noticeable. Suspension bridge has become an important choice for bridge construction because of its large span and less materials. At present, there is a very obvious trend of bridges built in China, that is, the span is getting bigger and bigger, and some even reach thousands of meters. Therefore, these bridges are more sensitive to the influence of wind. Serious bridge damage occurs all over the world, which brings great security risks to people's lives.

In China, there are more and more accidents of large bridges. 1998 During the closure of Ningbo Bridge, the bridge body broke, causing huge economic losses. From 65438 to 0999, Chongqing Rainbow Bridge collapsed seriously, causing 40 casualties and extremely bad social impact. In 2000, the deck of Gaoping Bridge in Taiwan Province Province suffered a serious fracture accident.

In recent years, many bridges have been built in China, such as Xupu Bridge, Yangpu Bridge and nanpu bridge. In addition, China has also started to build suspension bridges, such as Qingma Bridge and Humen Bridge. With the rapid development of traffic in many areas of our country, the construction of long-span bridges is imminent. Monitoring is particularly important in the whole process of bridge construction if these bridges with huge investment want to achieve safe, reliable and durable results.

1 Influence of monitoring on bridge construction

1. 1 prevent bridge accidents.

The most important link in bridge construction is safety guarantee. It is very necessary to monitor and supervise the whole process of bridge construction. After the bridge starts construction, a complete monitoring system is essential. In all stages of bridge construction, the real internal force and deformation of the structure should be comprehensively monitored by monitoring means, so as to fully grasp the process and safety issues. In the whole construction process, when there is a big error between the monitored actual value and the predicted value calculated before construction, the construction cannot be carried out, so the construction should be stopped, necessary inspections should be carried out, and the reasons for the error should be found and analyzed. If you don't do this, or forced construction, is likely to lead to accidents. For example, the Quebec Bridge in Canada spans 548 meters ... During the construction, two major accidents occurred. The Quebec Bridge adopts cantilever assembly method. During the construction process, the south anchorage truss collapsed when it was almost completed. The reason is that the lower chord in the middle is unstable because the truss is too long and the pressure is great, and the whole truss is seriously damaged. In the construction of Quebec Bridge, if the necessary monitoring means are adopted and some monitoring points are arranged to monitor the abnormal phenomena in real time for those members with large internal forces, large-scale collapse and fall accidents will not occur as soon as the abnormal phenomena appear. Therefore, whether the construction of a bridge can be completed on schedule and safely, and whether construction accidents can be eliminated, construction monitoring is a very effective means. Bridge construction monitoring system is very important for bridge construction. If bridge construction is to be carried out safely, the monitoring of bridge construction can not be ignored, especially for long-span bridges with high cost and long construction time.

1.2 provides reliable data for bridge construction.

In the process of bridge construction, the whole construction process should be monitored so as to adjust the construction scheme in time. These data are of great significance to the quality and safety of bridges. During the construction of concrete-filled steel tubular arch bridge, the stress system of the arch structure of the main bridge needs to be changed many times, and the stress of the arch ribs will change and be complex, which is very difficult to construct. Therefore, many complicated factors need to be considered in the construction process, which may lead to the change of internal force of the structure. Although various situations in construction are considered in bridge design, the construction process of the bridge is very complicated, and it is very difficult to accurately estimate the actual state of the structure before construction. Therefore, it is necessary to monitor the bridge superstructure in real time after the hollow steel pipe is closed. Put an end to the situation that the local stress of the main arch rib exceeds the limit or even becomes unstable due to various unpredictable factors, and reduce the accidents caused by bridge deck deformation. During the whole construction process, through real-time monitoring of the bridge structure, the data in the construction process can be obtained, and the control parameters in the construction process can be adjusted in time according to the monitoring data. At the same time, for the projects that have been completed but the structure is out of control, they can be adjusted in time and effectively in the next stage of construction to ensure the smoothness of the structural alignment, and at the same time, the actual internal force distribution can be comprehensively monitored to keep the bridge within the safe tolerance range. Generally speaking, pouring concrete into steel tube arch rib is a very dangerous construction stage. Therefore, in order to ensure the safety of bridge construction, the internal force of the arch rib and the displacement of the arch foot should be monitored at any time when anything on the arch rib is pouring concrete. The whole monitoring should focus on the changes of monitoring points at the top and bottom of L/2, L/4 and 3L/4 sections of the vault. The monitoring point of L/2 section should pay attention to the tension change at the upper edge, and inform the construction unit to change the counterweight value in time to reduce the harm of "roof caving"; At the same time, for L/4 and 3L/4 sections, more attention should be paid to the symmetry values of the two sections. Strictly control the spraying speed, keep the top surface of concrete at both ends rising synchronously, and prevent the elevation of concrete at one side from rising too fast.

Bridge monitoring can rely on data to provide very reliable analysis and solve difficult problems in construction. For example, during the construction of a bridge in Shandong, according to the monitoring results, the prestressed steel strand is tensioned. Although the tensioning tonnage has reached the design value, the elongation of steel strand has not reached the design value. What caused this situation? Monitoring and monitoring data can provide effective help for analysis. This bridge in Shandong is designed as a through arch bridge with three spans. The middle hole of the bridge is a through prestressed concrete tied arch with a span of 80.80m, and the side hole of the bridge is a concrete T-beam with a length of about 30 m, and the length of the whole bridge is close to150 m. The tensioning control mode of the prestressed steel strand of the bridge is double control mode, which is controlled by oil pressure and tensioning elongation. When the steel strand on the tie beam is tensioned on the bridge, the monitoring shows that the oil pressure control index can meet the predetermined requirements, but the stretching elongation can not meet the requirements.

Steel bar gauges are embedded in the five sections of the bridge 1L/6, 2L/6, 3L/6, 4L/6 and 5L/6 to effectively monitor the tension of steel strands. According to the theory, tension is carried out at both ends, and the stress and axial force increment in the middle section can't reach the maximum, so there must be something wrong in the middle of the steel strand. And according to the analysis of valid data, it is judged that the steel strand must be stuck somewhere in the middle. After that, the necessary inspection is carried out by pulling out the whole steel strand. Finally, it is found that there is a very obvious place where concrete sticks in the middle of the steel strand. Therefore, it is inferred that the concrete may accidentally flow into the corrugated pipe when pouring the beam. So the steel strand is stuck, so it is stuck in a certain section of the steel strand when it is tensioned. According to the monitoring results and practice, it is concluded that the analysis and judgment are completely correct. This effectively proves that bridge construction monitoring and monitoring can provide effective basis for difficult problems and situations that need to be analyzed in bridge construction.

1.3 Accumulate technical data

At present, many bridges in China have adopted novel structural systems. In the whole construction process, statically indeterminate or statically indeterminate system becomes a complex structure with more changeable state. Even sometimes, compared with the running state after completion, it is even more unfavorable. Through construction monitoring and supervision, the theory and method of design can be effectively verified, providing very detailed information for future bridge design and bridge safety construction.

2 conclusion

Bridge construction monitoring is to realize the ideal target state of bridge structure internal force and alignment through simulation calculation and actual structure state monitoring in the whole process of construction and erection, and through process monitoring and adjustment. With the more and more scientific bridge construction, scientific detection is particularly important in bridge construction. Accelerate the application of bridge monitoring technology to ensure the safety of bridge construction.

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