The Safety Influence Study Of Overload Operation To Existing Reinforced Concrete Beam (Slab) Bridges Structure

The bridge is an important part of the smooth flow of road traffic. With the developmentof the society in recent years, People are also more of the demand for transportion, Also,more road and bridge construction has increased year by year, More and more large vehicleslead to overloading phenomenon.Overloading of vehicles involved in more causes,if you wantto control it, it is difficule. Because of the existence of interest, So it is difficult tofundamentally solve the problem of overload.The safety of the bridge is very important for the whole traffic, For various reasons,Bridges will inevitably produce a variety of diseases from the starting opened to trafficoperations, These diseases seriously threaten the safety of bridge, Especially for overloadedtransport damage on the bridge, The serious influence to the bridge structure and the safety ofpeople’s life and property, Middle and small span bridge occupies a big proportion in thenumber and length of all bridge in our country, Vehicle load impact on these bridges largerthan the large-span bridges,so we should study and analysis the safety of bridge for reducingthe possibility of bridge safety accident.In this paper, regarding the Ganzihe bridge on Gulang S308line in Gansu Province asengineering background, the safety overload operation of existing reinforced concrete beambridges was studied on the basis of Specification for Inspection and Evaluation ofLoad-bearing Capacity of Highway Bridges (JTG/T J21-2011) and random reliability. Thefruitful results are as follows:Firstly,The internal force of reinforced concrete beam bridge caused by vehicle loads iscalculated and compared between the old and the new specifications. Disease types of upperstructure, bottom structure and the bridge pavement deck are introduced. The perniciousnessof overload operation to the bridge decking and the main stress components are summarizedemphatilly.Secondly, Safety assessment methods and theories for existing bridge structures arestudied, analytic hierarchy process, The fuzzy comprehensive evaluation method, designcriterion based method, and reliability theory based method and so on. The merits anddrawbacks are point out, and then the reason for reliability applied to bridge assessment isrepresented.Thirdly, Uncertainty of structure analysis, random variable and random process, andminimum reliability index are introduced in detail. The resistance model and the overloadmodel of existing reinforced concrete beam bridges are elaborated systematically. On thebasis of stationary binomial random process for variable load’s sample function, consideringmodification factor of live load, the probability model of vehicle action effect was presented, and considering durability parameters, the time-vary probability model of componentresistance was offered.Lastly, In order to simplify the complicated reliability calculating process, the reliabilitysolution program was designed by the Matlab. A severe overloading concrete beam bridgewas evaluated by the research fruits upwards. The modification factor of live load wascalculated by the norm on the basis of annual intermittent daily traffic of the bridge.There are many kinds of methods that are about to bridge safety evaluation, the practicalapplication in the research of the bridge should be choose more suitable method according tothe actual situation.