Monitoring And Early Warning Of Long-span Suspension Bridges Based On Design Effect And Long-term Effect

Suspension bridges have a large spanning capacity and beautiful lines.Many long-span suspension bridges have been built at home and abroad,but the suspension bridges are complicated and subject to environmental and other complex factors.Therefore,it is necessary to install a health monitoring system on the long-span suspension bridge to monitor the operation status of the bridge in real time.In this paper,on the basis of existing research,through a suspension bridge health monitoring system of long-term monitoring data and established the finite element model of suspension Bridges,in order to study large span suspension bridge based on the design effect and long-term effect of monitoring and early warning value,and through the bridge operation periods set warning value and real time monitoring data contrast,will gain control of bridge operation state,to ensure safe operation in the bridge.The main research contents and conclusions of this article are as follows:(1)When the suspension bridge was just opened to traffic,the bridge components were not damaged.At the same time,because the suspension bridge has just begun to serve,there is no need to consider the service life of the bridge,and there is no need to modify the variable load,so the early warning value of the suspension bridge component is at the design load under the combined effect.This article takes the suspension rope and the lower chord of the main truss as examples for research,firstly,the finite element model of the suspension bridge is established.and the load combination of the finite element model is carried out according to the specifications to obtain the suspension bridge components in each load combination.The cable force value and stress value under the action,and then through the statistical comparison of the cable force value and stress value under each working condition,the maximum value of the suspension bridge component under each load combination is obtained,and take this maximum value as the initial warning value set in the detection system.(2)The warning value set for the suspension bridge components in the health monitoring system needs to be modified as the service life of the suspension bridge increases,so as to more monitor the operation of the bridge accurately,therefore,it is necessary to study the long-span suspension bridge components under long-term effects how the warning value has changed.On the one hand,as the service life of the bridge increases,the variable load considered at the design stage needs to be corrected.According to the "equal transcendental probability criterion" proposed by Academician Ou Jinping,the correction factor for the variable load of the bridge during different service periods is obtained,thus Obtained the early warning value of the suspension bridge component under the variable load correction during the service period,and the study found that the warning value caused by variable load correction changes little when the suspension bridge has been in service for a short time,but the influence caused by variable load correction is relatively large when the suspension bridge has been in service for a long time,so enough attention should be paid to it;On the other hand,based on the long-term measured data of the health monitoring system,the cumulative fatigue damage degree of the suspension bridge component is obtained through the rain flow counting method and the fatigue damage accumulation theory,so as to study the early warning value of the suspension bridge component after fatigue damage under long-term effects.The results show that within the same period of service of the suspension bridge,the impact of fatigue damage on the early warning value of the suspension bridge components is much greater than the effect of variable load correction on the early warning value.(3)Combining the above research contents,a set of research methods for early warning value of suspension bridge components is proposed.According to this method,combined with the long-term measured data of the health monitoring system,the warning can be updated in real time as the service life of the bridge increases in the health monitoring system.This purpose is to ensure the safe operation of the bridge.