Based On Dynamic Testing Of Bridge Carrying Capacity Evaluation Method Research

With the increasing traffic and vehicle weight,most of the Bridges in our country appear problems such as lower and inadequate bearing capacity and durability,and thus lead to many accidents at present stage.Throughout the development of the highway Bridges in China,from the sustainable development strategy analysis,the focus of the highway Bridges in China should transfer from construction to maintenance,repair and reinforcement.So,in a timely manner to understand the status of the technology of Bridges is becoming a top priority.At the same time as the highway traffic increases,the current domestic specification,bridge load test is still used design load of highway grade I and II.It does not reflect the actual passage under the bridge in the mechanical load condition.For current specification imperfect part,this article focuses on the study of the model analysis,the bridge condition state analysis and the method dynamic assessment of bridge bearing capacity which under the actual traffic condition.This paper firstly carries on the theoretical derivation,and came to a conclusion of method of theoretical calculation of vehicle-bridge coupled vibration system.Meanwhile,with the aid of mathematical methods,this paper testified the feasibility of using the simplified finite element model to solve the problem of vehicle-bridge coupled vibration.By using the simplified finite element model,this paper validate that the spring system's movement speed and mass is the most significant factor for the dynamic signal of vehicle-bridge coupled vibration system.By establishing the whole bridge model,and analyzing the vehicle-bridge coupling vibration in the influence of crossing direction of bridges,this paper proposes to apply the vehicle-bridge coupled vibration of the whole bridge model to the calculation of the theoretical value in bridge load test to obtain more accurate and more reasonable result.Secondly,this paper respectively puts forward the highway bridge design of convoy simulation method and method of get bridges dynamic response under design load.Main introduces the bridge carrying capacity assessment method based on dynamic testing.First,according to the rules and actual situation to determine the design lanes of a bridge and it's maximum speed standard,and according to the most adverse effects of traffic on the bridge to establish finite element model to simulate the natural vehicle team to get the base value(SA)of most adverse effect;Then using finite element model of the bridge structure to simulate the loading vehicles which numbers are equal to the standard number of lane.By regulating the loading vehicles'speed and mass,to make the error ratio of effect value of control point(S_B)and mechanical effects base value(S_A)within 95%-105%;According to the requested speed and weight of the vehicle load to conduct field tests,and synchronously collect the deflection and strain values of each control point(SC);The final measurement results were analyzed in order to evaluate the carrying capacity of the bridge.Final,applied the above"assessment based on the carrying capacity of the bridge dynamic test methods"to the actual project.In the actual project validation,discuss the accuracy and usefulness of the research methods.Analysis the differences of the proposed method with the conventional static load test in the time to determine its convenience and quickness.