Assessment And Study On Load Test Of Long Span Continuous Rigid-frame Bridge

With the advancement of technology and the rapid development of highway traffic,the detection of bridges is catching more widely emphasis gradually.As an important method of detection,load test showing its vital significance in the following aspects:assessing the actual bearing capacity of existing bridges, establishing and accumulating technical information of bridges,developing the old assess theories and the new design theories of bridges.Through the load test,the construction quality and structure stress capacity of the bridge can be tested,the actual bearing capacity of the bridge can be judged and the actual operation condition and the use conditions of the bridge can be determined.It can provide scientific basis for final acceptance and the operation,as well as accumulate important technical information for the bridge of a greater span and more complicated structure in the future.The thesis elaborated the significance of the bridge detection as well as the importance of load test first;Based on the support project of Ma Shuihe Bridge on the western section of the main trunk line HuRong Road in Hubei,the paper reviewed the development process of long-span continuous rigid-frame bridge,and discussed the purpose of load test,the theoretical analysis methods,the experimental key points and the status assessment principle of prestress concrete continuous rigid-frame bridge. Using the beam element of large-scale finite element software MIDAS/CIVIL established a 3-D finite element model to calculate the stress and deflection of each control section under the design load,and drew up the corresponding influence line. In the premise of ensuring the load test efficiency,we determine the control load and load conditions of static loading test.The verification coefficient of the structure can be calculated according to the results of comparison between the actual values of stress and deflection result from load conditions and the theoretical values of the controlling sections.Then the actual carrying capacity of Ma Shuihe Bridge can be evaluated based on the verification coefficient.At the same time,analyzing the modality of the actual bridge model to obtain the bridge structual mode of vibration and natural frequency.Compared with the measured natural frequency of the dynamic load test, the power property of the bridge structure can be determined.The bridge's damping deflection period and impacting coefficient can be calculated according to the measured data obtained through dynamic load test.The relations between the damping natural frequency and the non-damping natural frequency are theoretically probed in the fifth chapter.There are some problems about the present way of the static and dynamic load test to evaluate a bridge's load carrying capacity.A finite element model method that more conforms to the bridge should be revised based on the measured natural frequency,and then calculating the static load test using the amended model.Consequently,the paper revised the related parameters of the model and obtained more reasonable ones, analyzed and calculated the load condition one and load condition two of the static load test,and then assess the carrying capacity of the bridge compared with the measured values.