斜度对斜交桥地震作用下的扭转效应影响

为满足交通工程中线路运行的需要,桥梁斜交有时不可避免.相对于正交桥而言,斜交桥在地震作用下有扭转破坏的趋势.斜度作为斜交桥的主要特征参量,其对斜交桥在地震作用下扭转效应的影响作用,目前研究还存在彼此不同的看法.为此,以一实际工程为原型,建立了不同斜度的桥梁分析模型,利用模态分析和非线性时程分析方法对不同斜度的斜交桥梁在地震作用下的扭转效应展开研究.通过研究发现:斜度增大,斜交桥的扭转周期与平动周期之比线性增加,结构的抗扭刚度减弱,同时桥墩在地震作用下的扭矩作用也将增大.对于上部结构平面内的扭转位移,若梁体端部与桥台之间的伸缩缝宽度足够大,梁体与桥台不发生接触碰撞,增大桥梁的斜度并不能引起上部结构的扭转位移;若梁体与桥台发生接触碰撞,斜度增大,上部结构的扭转位移增大.

Torsion effects of skew angles on skew bridges during earthquakes

To meet the requirement of traffic lines,skew bridges sometimes cannot be avoided.In comparison with orthogonal bridges,there is a tendency for torsion damage of skew bridges during earthquakes.As the main characteristic parameter for skew bridges,the skew angle may have a significant effect on torsion damage of skew bridges during earthquakes.However,this theory has not been confirmed and there are several existing opinions.In this paper,a real bridge was used as the prototype,and bridge models with different skew angles were developed.The torsion effects of the skew angle on skew bridges during earthquakes were studied using the modal analysis and nonlinear time history analysis methods.From the research,it can be found that by increasing the skew angle,the ratio for the torsion period and translation period will increase linearly,and the torsion stiffness will decrease.The torque of piers under earthquakes will also increase with the increase of the skew angle.For the torsion displacement of the superstructures,if the width of expansion joints is enough to avoid the collision between superstructures and abutments,the increase of the skew angle will not result in torsion displacement of superstructures;on the other hand,if a collision between superstructures and abutments takes place,torsional displacement of superstructures under earthquakes will increase with the increasing of the skew angle.