Study On The Large-cargo Transportation Analysis Methods And Control Standard Of Conventional Bridge On Chongqing Highway

With the rapid development of Chongqing City’s modern industry andtransportation, both traffic volume and cargo tonnage of large-cargo transportation oncity highway are gradually increasing. Bridges in Chongqing are of great number andcomplexity, which differ in types, span, technical status and many other aspects.Meanwhile, there is no unified and clear control standard for large-cargotransportation, which has its specialty in load distribution and transit frequency. Thoseproblems are threatening highway bridge safety in Chongqing, and also decreasing theefficiency of administrative approval of large-cargo transportation, which would bringdifficulties to the transportation department. Investigation and research on car typesand transit routes of large-cargo transportation and distribution of bridge types,technical status and span of highway bridges have been performed. Via calculating,factor definition and load control analysis, this essay has presented the load controlstandard for regular large-cargo transportation on Chongqing highway, aimed atbringing technical basis for administrative approval of large-cargo transportation andadditionally, improving the working efficiency of transportation department to letthem serve people better and faster.Firstly, the main transit routes, vehicle models and random load characteristic oflarge-cargo transportation has been determined through investigation on vehicle statusand transit routes of overload vehicles on Chongqing highway. Combing with the datafrom researches on distribution of bridge types, technical status and span of highwaybridges, prefabricated prestressed hollow slab and T girder concrete bridges,commonly second grade bridges, are determined to be the type of regular bridges,which make the foundation for the further study of large-cargo load control standard.Secondly, evaluation methods for bearing capacity of serving bridges underlarge-cargo transportation has been presented through bearing potentiality and maindiseases analyses. According to the special randomness and transit pattern oflarge-cargo transportation and analyses of dependence principal and relevant code,calculation of load control standard of large cargo only includes dead load andlarge-cargo vehicle load, whose partial safety factors are1.2and1.1. Transversedistribution coefficient is the bigger one between values calculated while vehiclesdriving in the middle of the bridge and0.5m deviated from the middle of the bridge, which is supported by dynamic programming principal. Meanwhile. Afterwards,primary load control standard is presented according to relevant code and law.Thirdly, conclusion that cracking resistance can be controlled by crack width hasbeen made. Limit crack width is0.1mm, which is determined referring to the closureperformance of crack on prestressed concrete. Three kinds of load control principalhave been presented, which is ‘no tensile stress’,‘less than nominal tensile stress’and‘meet the ultimate bearing capacity’.Finally, regular load control standards for large-cargo transportation on highwaybridges have been achieved, based on conclusions in the essay and modeling andcalculation on Yuqian highway. Recommendations for use of the standard are alsopresented through comparisons, while applying to each3different principals, bridgeswith different types and span and bridges with same types but different section.