Study On The Mechanism Of Lateral Displacement Disease Of Inclined Highway Bridge

Based on the engineering background of a span bridge of Zhangshi high-speed highway and the actual bridge diseases,the finite element model is established to study the influence of temperature load(including the overall uniform lifting and gentle temperature gradient),automobile load(including the vertical load and horizontal braking force),longitudinal slope,transverse slope and differential settlement of support on the lateral displacement of the skew bridge.At last,various factors are considered comprehensively,and the deformation and reaction distribution law of the skew bridge are analyzed respectively when the joint is not squeezed to death(the beam body and the breast wall are in contact with each other but weak action)and the expansion joint is squeezed to death,and the main factors affecting the lateral displacement of the skew bridge are summarized.Main conclusions are as follows:(1)When all kinds of loads act alone,the object of load is skew bridge or subgrade behind abutment;When all kinds of loads are combined,the object of the load should be the structural system composed of the bridge and the subgrade behind the abutment;(2)The lateral displacement of skew bridge is caused by various factors.The factors that affect the longitudinal displacement of skew bridge are overall uniform temperature rise and fall,temperature gradient,vehicle load,longitudinal slope,cross slope and bearing settlement.The main factors that cause the longitudinal displacement of skew bridge are vehicle braking force and overall uniform temperature rise and fall.When the longitudinal displacement is too large,the expansion joint may collapse,which is the direct cause of the lateral displacement of the skew bridge;(3)The mechanism of lateral displacement disease of skew bridge is: when the beam end is just in contact with the abutment breast wall(assuming that the ambient temperature is 40 ℃),the corresponding longitudinal displacement(25.63 mm and5.45 mm respectively)occurs in the beam and subgrade,which makes the beam and breast wall contact each other,but has no effect.If other loads remain unchanged after that,only the ambient temperature continues to rise,the longitudinal displacement of the beam end will be constrained by the breast wall,and the longitudinal displacement of the breast wall will also be constrained by the beam.The deformation of the beam body is squeezed by the breast wall,which produces a huge longitudinal force on the breast wall.At this time,the reaction of the breast wall to the beam end is the restraint reaction perpendicular to the beam joint and the friction parallel to the beam joint(these two reactions keep balance with the longitudinal force at the beam end);When the deformation of the beam body continues to be squeezed,the force of the beam end on the breast wall continues to increase.When the component of the force along the beam joint direction is greater than the friction force along the beam joint direction(if the lateral restraint of the beam end has been destroyed at this time),there will be dislocation between the beam end and the breast wall along the beam joint direction,resulting in the maximum lateral displacement of 87.79 mm.