Study On Stability Against Overturning Of Curved Box-Girder Bridge With Single-Column Piers

With the accelerating of urban modernization pace,the population density is improving unceasingly,and the followed problem of urban traffic congestion lead to inconvenient trip.In order to alleviate traffic congestion problem and improve the quality of travel,lots of interchange overpasses and viaducts are born at the right moment.Curved bridge is more appreciated by the designers because this bridge type is more suitable to the complex topography and smooth vehicle traveling of cities.Relative to the straight line bridge,“bending-torsion coupling” is one of the biggest characteristics of curved bridge,and this phenomenon also can appear even though under the action of gravity.The designers focus more on the structural behaviors of bending resistance and shearing resistance of the curved bridges,and pay insufficient attention to their occasional eccentric loading action so that bridge rollover accidents happen occasionally in recent years.In this paper,finite element models of different curvature radiuses and bearing eccentrics were established by combining with the actual project,and the stability against overturning of three equal span curved box girder bridge with single-column piers was studied via applying different vehicle load,the main results are as follows:(1)When the support of middle piers is located on the inner side of the connecting line of the end outer side supports,overturning axis is the connection line between outside bearings of the bridge end;When the support of middle piers is located on the outer side of the connecting line of the end outer side supports,overturning axis is the connection line of the adjacent middle piers.When the outside supports at the bridge end and the supports of the middle pier are in close to one straight line,the eccentricity of the support has a great influence on the selection method of the overturning axis.(2)Support eccentricity has a great influence on inside and outside bearing reaction of the bridge end.With the increasing of eccentricity,the outside bearing reaction decreases continuously and the inside bearing reaction increases continually.However,support eccentricity has a little impact on the bearing reaction of middlepiers anyway.(3)According to the factors of safety against overturning calculated by the formula of Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(opinion draft),when the curvature radius is smaller,support eccentricity has a greater influence on the factors of safety against overturning;when the curvature radius is larger,support eccentricity has a little impact on the factors.This is due to that the increment of the moment produced by bearing reaction of bridge end is essentially the same as the decrement of the moment produced by bearing reaction of middle piers,so it has a little impact on the factors after the operation of formula.(4)It can be seen via the factors of safety against overturning calculated by the formula of opinion draft that the factors of safety against overturning under lane load is less than the factors under vehicle load,so lane load should be adopted when check the safety resistance to overturning of superstructure.(5)Under the reasonable preeccentricity,the increasing radius of curvature leads to that the factor of safety against overturning shows the increase after decrease tendency.So the corresponding curvature radius leading to lower the factors of safety against overturning should be avoided.