Research On Health Monitoring And Condition Assessment Of East Tower Suspension Bridge

Quality problems during bridge operation are common problems in civil engineering,and more and more bridge collapse accidents have occurred in recent decades.In order to avoid the occurrence of bridge accidents,bridge health monitoring and condition assessment are particularly critical.At the same time,the reasonable placement of sensors in health monitoring and scientific assessment of the health status of bridges have also become problems that researchers have been working hard to solve but have not yet solved well.This thesis takes the East Tower Suspension Bridge as the engineering background,and conducts health monitoring and condition assessment research on it.Because the East Tower Suspension Bridge is located in Liaoshen,it is relatively affected by environmental factors such as temperature.It is of great significance to grasp the deformation and stress during its operation,to reasonably assess its health status,and to maintain normal operation and reasonable maintenance.At the same time,the research results can also provide a reference for the evaluation and maintenance of such suspension bridges.The main content of this thesis:(1)Based on the Midas Civil finite element software,the East Tower Suspension Bridge was modeled and analyzed.The same conditions as the load test of the completed bridge were applied.The simulation results were compared with the test data to verify the accuracy of the model.And analyze the change trend of displacement,stress and internal force of various components under temperature,vehicle,wind and other load conditions,and design the main tower,main beam and main cable in health monitoring based on the parts with large numerical changes,Sensor placement,quantity and type of boom.By comparing the effects of temperature on each component,the cooling conditions of the surface system have a great influence on the stress and displacement of each component of the suspension bridge,which is much greater than the effect of the system temperature increase and other conditions.Attention should be paid to winter monitoring.(2)Based on the analytic hierarchy process,the monitoring scheme of this bridgeis further optimized.Determine the judgment matrix and hierarchy evaluation system of each level of this type of suspension bridge.And the eigenvalue algorithm in the analytic hierarchy process is used to confirm the weight of 33 monitoring indicators of the suspension bridge.The damage proportion of each part of the suspension bridge was determined.From all indicators,the main monitoring points of the sensor and the main maintenance indicators of the bridge were analyzed as the vertical displacement of the main beam and the tension of the main cable hanger.The indexes with the lowest weights are the humidity at the upper edge of the main beam and the stress at the bottom of the main tower.Provide a reference for the maintenance and repair of such bridges,and the reasonable arrangement of measuring points.(3)The fuzzy mathematics theory is introduced according to the evaluation system based on the analytic hierarchy process to determine the scheme set,index set and weight set of the fuzzy comprehensive evaluation method for such suspension bridges.Using Midas Civil to simulate the temperature and vehicle operating conditions of the East Tower Suspension Bridge during operation,through the finite element analysis results and on-site measured data as the main basis,combined with the fuzzy statistical method and expert questionnaire method,the fuzzy comprehensive evaluation method set of the East Tower Suspension Bridge was determined.The value of the membership function for the index set.And construct the fuzzy evaluation matrix of each level,and finally judge the health status level of each monitoring index of the bridge to be "good" or higher by the maximum membership level in the fuzzy evaluation matrix.The fuzzy comprehensive evaluation method is used to analyze that the future operation of the East Tower Suspension Bridge should focus on the fatigue damage of the lower section of the mid-span,the lower section of the main span,the upper part of the tower column,and the middle of the main beam.