Research On Key Techniques Of Load Test For Long-span Prestressed Concrete Continuous Rigid Frame Bridges

Since the 1990 s,the construction of highway bridges in China is booming.With the rapid development of national high-end technology,bridge transportation industry is developing actively to meet the needs of modern road traffic.How to ensure the reliability of bridge quality is the most important part today.Therefore,bridge detection has been paid more and more attention.As an important means of bridge detection,load test plays an irreplaceable role in bridge testing technology.It can assess the actual bearing capacity of the bridge and collect and accumulate all kinds of bridge data.It is of great significance to promote and develop the construction of the new and old bridges.For bridge designers and staff summed up valuable experience.The internal force of the bridge structure is understood intuitively,the quality of the bridge construction is judged,and the design is reasonable in theory,which provides a scientific basis for the acceptance of the completion of the bridge and the evaluation of the operation state.It has accumulated important technical data for the future bridge construction with complex structure and larger span.Therefore,the development of load test is essential.Based on a highway bridge in Liaoning Province,this paper discusses the necessity of bridge detection to bridge safety operation and the importance of bridge load test.The development of long span PC continuous rigid frame girder bridge is briefly introduced,and the development process of long span continuous rigid frame girder bridge at home and abroad is summarized.The purpose,test theory and test analysis method of long-span PC continuous rigid frame girder bridge under load test are expounded,and the operation state of the bridge is evaluated.In addition,the 3D beam element model of the bridge is established by using the Midas/Civil finite element analysis software,and the bridge is calculated on the basis of the theory loading.The loading position diagram of beam load test at the most unfavorable section,including positive moment,negative moment and shear force.Under these conditions,the deflection and stress values under load are theoretically analyzed,and the influence lines of the bridge are drawn,the loading scheme and steps of the load test are determined,and the loading efficiency is controlled to ensure that the loading efficiency can reach the standard value.According to the load test of thebridge,the deflection and strain value of each test section are collected and analyzed,and the check coefficient of the structure is calculated.The actual bearing capacity of the bridge is judged by comparing with the theoretical value.Under the dynamic load test,the vibration mode and the solid of the bridge structure are analyzed by the finite element software.Frequency,according to the bridge measured frequency comparison analysis,the dynamic characteristics of the bridge.At the same time,the impact coefficient and damping ratio of the bridge should be calculated according to the test data under dynamic load test.