Research On Different Standard Vehicle Load Effect Of Existing Urban Bridge

The urban bridges composing the urban roads are both the hub of urban lifeline engineering and the basic traffic facilities which are essential and related to the national economy and people’s livelihood. Vehicle load is one of the important factors that affect the structural safety and usability of the city bridges. However, with the continuous development of the urban transportation demand and the automotive industry, the vehicle overload phenomenon is worsening and leads to many bridge collapse accidents caused by the overload car in recent years. In order to meet the development requirements of the times, the city bridge design specifications are updated in our country constantly. Inparticular, the vehicle load model are changed from the fleet load pattern to the lane load pattern with concentrated force.According to the change of the vehicle load model, this paper select three different types of fuzhou urban old bridge including simply supported T girder, simply supported hollow slab bridge and continuous box girder bridge which built in 1960s to 1990s as the real engineering bckground. Using of space finite element program Midas/Civil to calculate the model of the bridge structure according to the original design code and Code for design of the municipal bridge (CJJ11-2011),The Standard of Loadings for the Municipal Bridge Design (CJJ77-98), The Standard for design of the municipal bridge (CJJ11-93) three kinds of different versions of the old and new standards of different vehicle standard load, and calculating the our country city Bridges in both old and new rules and regulations of the difference between the vehicle load effect, and design the ultimate bearing capacity, deflection and the difference between impact coefficient.calculates the difference between the design limit carrying capacity of our country city Bridges in both old and new rules and regulations of the vehicle load effect,and the deflection between impact coefficient.The results of the study show that the maximum moments and shear of 1960s simply supported T-beam bridges under the existing 11 norms City-A lane loads and load combination effect are larger than that caused by initial design loads by 122.0%, 156.6%,119.5% and 147.0%. Therefore, it is urgent to strengthen check for mid-span flexural and shear of existing bridges. For 1980s simply supported hollow slab bridges, those are larger by 14.3%,75.2%,4.2% and 41.7%. Therefore, it is urgent to strengthen check for bearing shear of existing bridges. For continuous box girder bridges in the 1990s, the maximum moments in side span, mid-span, Pier Top and shear are larger than that by 42.7%,45.2%,17.9% and 26.0%. Thus, it is urgent to strengthen check for flexural and shear in Pier Top. For the above three kinds of bridge, the deflections caused under standard vehicle loads ruled (excluding impact) by City Bridge Design Specifications meet the requirements of each specification.