Analysis Of The Dynamic Characteristics And Response Under Vehicle Load For Small And Medium Span Slope Highway Bridge

Slope bridges become more and more common in the southwest mountains of China, the phenomena of local failure in slope bridges is more serious than those in bridges with no slope recently. At the same time, in order to decelerate the speed of vehicle in the bridge, vibration speed control humps are usually set on the bridge at random whereas, there is less research about speed bumps’ effect on the structural dynamic characteristics of bridge. So analysis of dynamic characteristics and response for slope highway bridge under vehicle load is necessary.Based on the study of National Natural Science Foundation of project“Research on dynamic load allowance of long span curved continuous rigid frame bridge with high piers under stochastic vehicle” and the Central University Fund“Dynamic analysis of long span slope bridges”, the natural vibration characteristics of simply supported beam and continuous beam with different slope and forms of support are studied by using the finite element program in the paper, and the natural frequency formula of slope bridge is verified by laboratory test. Dynamic load allowance(DLA) of simply supported slope beam and continuous slope beam bridge is analyzed according to “General Code for Design of Highway and Culverts”(JTG D60-2004). The effect of deflection and bending moment of bridge with longitudinal slope under vehicle loads are studied according to the principle of vehicle-bridge coupling vibration, then, time-history curves of different speed, different driving directions are obtained, and the DLA of bridge is solved according to the traditional calculation method. The influence of longitudinal slope direction and deck surface roughness on DLA of continuous slope bridge is analyzed, which are compared with DLA by the specification method. Based on the principle of vehicle-bridge coupled vibration, the effects of speed control bumps number, distance and position on dynamic characteristics and DLA of slope bridges with different slope under different driving speed are researched, and suggestions for reasonable setting of speed control bumps of slope bridges are finally put forward. The results show that the vibration mode of slope bridge is the same as that of general bridge, the bearing arrangement has some influence on the frequency of the bridge, the frequency of slope bridge is less than that of general bridge when bearing setting along the horizontal direction, the frequency of slope bridge is the same as that of general bridge when bearing is set perpendicularly to the girder. and fixed support is suggested to be arranged at the lower pier. Longitudinal slope has little effect on the DLA of simply supported bridge and continuous beam according to the specification method, and longitudinal slope direction has a certain influence on the DLA of continuous beam according to the principle of vehicle-bridge coupling vibration. Speed control humps enlarges dynamic response of slope bridge, so it is suggested to no speed control bumps on the slop when conditions permit, unless it is necessary, eight groups speed control bumps and 8m distance from each other as well as 8m form the end of slop bridge is recommended.The research results can provide a basis and reference for the dynamic evaluation of slope bridge and setting of transportation facilities.