Investigation Of Heavy-Duty Traffic And Analysis Of Load Effect On Short To Medium Span Bridges

With the rapid development of China's economy,transportation structures have improved significantly in traffic volume and vehicle load,which has brought a severe challenge to the safety of highway bridges.Therefore,this paper took Shijiazhuang to Cixian section of Beijing-Hong Kong-Macao Expressway as background,Carried out a traffic vehicle survey and analyzed parameters of heavy-duty vehicles,including influence on short to medium span concrete beam bridges and coMParative analysis of differences between the vehicle load obtained by survey and the one specified in the specification,which will help to provide basic data and reference for highway bridge design and specification improvement.The main work carried out and main conclusions are as follows:(1)Using weigh-in-motion system to investigate traffic information of the typical bridge section,the data of vehicle samples were screened and classified.The distribution characteristics of vehicle model,axle number,axle load and shaft spacing of the investigated vehicle data were obtained by means of mathematical statistics and probability theory method.A 2-axis truck of 1+2 axis type weighed 25 tons was determined as the main vehicle,while a 6-axis truck of 1+2+3 axis type weighed 77 tons was determined as the heavy truck model.Considering China's current highway overtaking vehicle identification standards,we finally got the car fleet model under heavy duty traffic.(2)Finite element models of new-built small to medium span concrete simply supported girder bridges were established.The load effects of each span beam bridge under the load of heavy-duty traffic is coMPared with that of highway-I vehicle load of "General Specifications for Design of Highway Bridges and Culverts" in 2004 version.The results show that:The bending moment,shear force and deflection effect of heavy load vehicle model are respectively 1.20?1.40 times,0.92?1.32 times and 1.31?1.40 times of the highway-I load effect of simply supported girder bridges with 10m to 50m spans.And smaller the span,the more obvious the load effect of vehicle load is.For structural design of simply supported girder bridges with the heavy traffic characteristics,the effect of heavy vehicle action can be conservatively assumed to be 1.40 times of that of the highway-I load effect of the 2004 code.(3)Finite element models of old-built small to medium span concrete simply supported girder bridges were established.The load effects of each span beam bridge under the load of heavy-duty traffic is coMPared with that of vehicle-ultra class 20 load of"General Specifications for Design of Highway Bridges and Culverts" in 1989 version.The results show that:The bending moment,shear force and deflection effect of heavy load vehicle model are respectively 1.28?1.49 times,1.14?1.32 times and 1.22?1.44 times of vehicle-ultra class 20 load effect of simply supported girder bridges with 10m to 40m spans.And smaller the span,the more obvious the load effect of vehicle load is.For structural design of simply supported girder bridges with the heavy traffic characteristics,the effect of heavy vehicle action can be conservatively assumed to be 1.50 times of that of vehicle-ultra class 20 load effect of the 1989 code.(4)The highway-I load in 2015 code is coMPared respectively with the load effect of the highway-I load in 2004 code,the vehicle-ultra class 20 load effect in 1989 code and the heavy vehicle load,the results are as follows:The smaller the span of beam bridge,the more obvious the lifting of the load effect is.The bending moment,shear force and deflection effect of heavy load vehicle model are respectively 1.02?1.25 times,0.92?1.13 times and 1.06?1.29 times of those of highway-I in 2015 code for the new-built simply supported girder bridges with 10m to 50m spans.While the bending moment,shear force and deflection effect of heavy load vehicle model are respectively 0.94?1.20 times,0.82?1.13 times and 1.08?1.30 times of those of highway-I in 2015 code for the new-built simply supported girder bridges with 10m to 40m spans.For structural design of simply supported girder bridges with the heavy traffic characteristics,the effect of heavy vehicle model can be conserved to 1.30 times of that of the highway-I in 2015 code.