Mechanical Analysis And Health Monitoring Of The Reinforced Concrete Beam Bridge

Due to various internal and external actions,such as vehicles,earthquakes,wind,the bearing capacity of the bridge has continued to decline,and even caused bridges collapse.Monitoring the healthy condition of the bridge and judging the operating status of the bridge is of great significance to reduce losses caused by bridge failures.This thesis took a simply-supported T-beam bridge in Guangdong Province as the engineering background,and used the finite element software ANSYS to perform static and dynamic analysis of the bridge.After the mechanical analysis was carried out,the weak parts of the bridge were obtained,the monitoring sites were arranged in these locations,and then designed the Bridge Health Monitoring system.The thesis mainly includes the following parts:(1)The engineering background of the bridge studied in this article was introduced,and then ANSYS software was used to build the finite element model of the bridge based on material parameters,geometric parameters and other information.The finite element model of the bridge is treated as the basis for subsequent static analysis and dynamic analysis.The separate modeling method was adopted to build the finite element model of the bridge.Element type Solid 45 and Link8 were selected to build concrete and rebars,respectively,and then the coupling command was used to make the steel bars and concrete work together to receive forces.(2)The force condition of the bridge under the action of vehicles with different overload rates was studied.This chapter firstly introduced the hazards of vehicle overload to the bridge.Secondly,three representative overload vehicle models were determined,and then,studied the impact of vehicles on the bridge under different overload rates.According to the above-mentioned mechanical analysis results,the weak parts of the bridge under the action of overload vehicles were obtained,and sensors were arranged in these parts as the basis for the design of the sensor system.The research showed that under the action of overloaded vehicles,the mid-span web of the bridge generated greater displacement,larger stresses were generated at the mid-span webs and bearings of the bridge.When the vehicle traveled to the mid-span of the bridge,a large compressive stress was generated at the mid-span position of the bridge deck.When the compressive stress exceeds the compressive strength of the concrete,the concrete in the compression zone of the bridge deck is crushed,resulting in brittle failure of the bridge without warning,this is prohibited in actual engineering.Therefore,it is essential to monitor the stress and displacement of the mid-span webs,bearings,and bridge deck.(3)According to the mechanical analysis results,the weight limitation standards for different types of vehicles were obtained.According to the mechanical analysis results of the bridge under the action of vehicles with different overload rates,we can conclude that the weight limitation of the M1three-axle vehicle is 47.5 t,the weight limitation of the M2 four-axle vehicle is 65 t,the weight limitation of the M3 five-axle vehicle is 100 t.(4)The bridge dynamic analysis was performed.The inherency frequency of the bridge was calculated,and the vibratory-type and inherency frequency of the bridge were obtained.The mechanical properties of bridges under moving loads were studied,and obtained the displacementtime curve,stress-time curve,speed-time curve,acceleration-time curve of the bridge mid-span web position under the moving load.The research showed that,with the increase of the speed of the moving load,the peak acceleration response of the bridge mid-span web position increases rapidly.Due to the acceleration response will greatly affect the safety of the bridge,it is necessary to monitor the acceleration response of the mid-span web of the bridge.(5)Introduced the composition and functions of the Bridge Health Monitoring system,and pointed out the importance of Bridge Health Monitoring.The design of the health monitoring system for this bridge includes the following four parts: sensor system design,data acquisition and transmission system design,safety assessment and early warning system design,data management system design.