Analysis Method Of Highway Bridge Load Limit Under Different Verification Load Levels

With the rapid development of economy and the change of heavy-duty vehicles,highway bridges are frequently damaged and collapsed due to overloading.How to ensure the safe operation of highway bridges and how to formulate accurate and reliable bridge load limit standards are urgent problems for highway operation management departments.However,due to different design bridge load level and different developed environment in various regions,the safety operation management of highway bridges has great challenges and difficulties.Therefore,it is significant for the formulation of load limit standards to establish an effective load-limiting analysis method for highway bridges.In the existing load limit analysis methods,the analysis and research on the load limit of the bridge after the static load test are unavailable.Therefore,this paper takes the medium-span and small-span reinforced concrete simply supported bridges with good technical conditions of on-site detection and static load test as the research object,and puts forward a method of highway bridge load limit analysis considering the verified load level by introducing the left truncated distribution of resistance.The main research contents are as follows:(1)Taking the live dead load ratio adopted in the design of reinforced concrete beam bridges as the basic parameter,the left truncated limit value of resistance corresponding to different static load test load efficiency is calculated,and the left truncated distribution model of resistance random variables is constructed.Assuming that the resistance and dead load effect are independent random variables,and based on the existing simplified analysis model of bridge load limit,an inverse analysis model of bridge load limit coefficient considering the efficiency of static load test is proposed.Based on this load limit analysis model,the designed load limit values of bridges are calculated according to the Design Code for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTJ 023-85,JTG D62-2004 and JTG 3362-2018),and the influence laws of different static load test efficiency on the above designed values are analyzed.The calculation results show that the load limit values of the bridges evaluated by the static load test and calculated by the simplified analysis model are quite different.For the same type of bridges,the greater the load efficiency of the static load test used in the test,the greater the corresponding load limit values,which provides a scientific basis for formulating the load limit strategy of this type of bridge.(2)According to the proposed load limit analysis model,the rationality of the model under ideal resistance conditions is verified.Taking the static load test efficiency as the control parameter,the sensitivity analysis of the effect of load limit values on the structure’s tail-cutting resistance and dead load effect is carried out by using the control variable method.The the change laws of ηq-ζq relation curves are explored under the conditions that the tail-cutting resistance and dead load effect are increased or reduced to a certain extent.(3)Taking the static load test of a hollow slab beam bridge as an example,the typical vehicle load limit values obtained by the load limit analysis model is taken as the test load.Then,the finite element model of single-span reinforced concrete hollow slab beam bridge through the finite element software Midas/civil is established and simulated.The simulation results show that the bridge structure completely meets the functional requirements of safety,applicability and durability under the load limit values,thus confirming that the highway bridge load limit analysis model considering the vehicle load level meets the engineering applicability,and provides a scientific reference for the formulation of the bridge load limit standard.