基于失效模式的双联塔非对称PC斜拉桥弹塑性极限承载力分析

Analysis on Elasto-plastic Ultimate Bearing Capacity of United Twin-pylon Asymmetrical PC Cable-stayed Bridge Based on Failure Mode

为了研究双联塔非对称PC斜拉桥主梁的破坏形式和弹塑性极限承载力,利用其破坏形式和安全储备指导实际车辆合理安全运营。以某在建斜拉桥为研究对象,基于弹塑性有限位移理论,考虑材料、几何双重非线性,采用三维弹塑性实体有限元法,利用Abaqus软件建立了作用公路-Ⅰ级和汽车-超20级设计荷载的成桥三维实体弹塑性有限元模型。计算分析了5个最不利荷载工况下结构成桥状态的破坏形式及弹塑性极限承载力。结果表明:在两种设计荷载作用下,主跨最大正弯矩区加载为结构安全系数最小工况,其安全系数分别为2.61和2.79,极限承载状态为主梁受压区破坏;公路-Ⅰ级荷载作用与汽车-超20级荷载作用相比较,5种工况下前者的结构安全系数均小于后者,差值在3.6%~17.2%,且两者的结构安全系数最小工况一致;荷载增量因子小于5时,结构基本处于弹性状态;结构达到极限承载状态时,汽车-超20级荷载增量因子大于公路-Ⅰ级;由于汽车-超20级荷载作用下的结构极限安全系数大于公路-Ⅰ级荷载作用下的,因此在桥梁运营阶段,按汽车-超20级的车辆布置形式进行实际车辆的运行管理控制是有效且安全的。分析结果对更好地保障结构的设计承载能力安全设计水平有积极作用。

In order to study the failure mode and elasto-plastic ultimate bearing capacity of main girder of united twin-pylon asymmetrical PC cable-stayed bridge,the destruction form and safety reserve are used to guide the rational and safe operation of actual vehicles.Taking a cable-stayed bridge under construction as research object,based on the elastoplastic finite displacement theory,considering the double nonlinearity of material and geometry,the 3D solid elasto-plastic bridge model for Highway-I load and Vehicle-Super 20 load is established by using 3D elasto-plastic solid FE method and Abaqus software.The failure modes and the ultimate bearing capacity of the complete bridge under the 5 most unfavorable load conditions are calculated and analyzed.The result shows that(1)under the 2 kinds of design loads,the loading on the maximum positive bending moment zone of the main span is under the condition of the minimum structural safety factor,the values are 2.61 and 2.79 respectively,and the ultimate bearing state is the damage at the compression zone of main girder;(2)the safety factor of the structure under the Highway-I load is smaller than the that under the Vehicle-Super 20 load under 5 working conditions,the difference is in the range of 3.6%-17.2%,and working condition of the minimum structural safety factors under the 2 kinds of load is the same;(3)when the load increment factor is less than 5,the structure is basically in the elastic state;(4)when the structure reaches the ultimate bearing state,the load increment factor of the Vehicle-Super 20 load is greater than that of Highway-I load;(5)since the structural ultimate safety factor of the Vehicle-Super 20 load is greater than that of the Highway-I class load,it is effective and safe to control the actual vehicle operation and management according to the Vehicle-Super 20-level vehicle layout in the bridge operation phase.The analysis result has a positive effect on better guaranteeing the design bearing capacity and the safety design level of the structure.