钢桥面板面外变形下顶板与U肋连接焊缝应力特征

THE STRESS CHARACTERISTICS OF THE RIB-TO-DECK WELD JOINTS UNDER OUT-OF-PLANE DEFORMATION IN ORTHOTROPIC STEEL BRIDGE

为研究顶板与U肋面外变形对两者连接焊缝处疲劳开裂的影响,建立了顶板-U肋有限元局部模型。分析了各类面外变形工况下顶板和U肋连接焊缝局部区域的应力特征,预测了疲劳裂纹易出现的位置和类型,并讨论横隔板构造对顶板与U肋连接焊缝处疲劳裂纹的萌生以及面外变形的影响。研究表明：面外变形将导致顶板与U肋的夹角变化,角度减小处易萌生疲劳裂纹,横隔板使得裂纹开裂方向更易由垂直向水平方向转变发展。焊根处萌生的疲劳裂纹以张开型或张开-滑开型裂纹为主,而焊趾处则以滑开型为主。横隔板有效地减小了顶板和U肋的面外变形。

In order to study the influence of out-of-plane deformation of the deck and the U-rib on the fatigue cracking,a local finite model was established. Several kinds of deformation of deck-to U-rib were modeled. The stress characteristics of rib-to-deck weld joints were analyzed,and the locations and types of fatigue cracks were predicted. The influence of crossbeam on the fatigue crack initiation and out-of-plane deformation of rib-to-deck weld joints was discussed. The study found that the out-of-plane deformation results in the angle between the deck and Urib changing,the fatigue crack was easy to appear in the location of decrease in angle. The fatigue crack between deck and U-rib,and the crack direction tending from verticality towards horizontal was caused by crossbeam. The fatigue cracks at the root were mainly the mode opening model cracks and mixed mode opening-sliding type cracks,while the cracks at welding toe were mainly mode II cracks. The crossbeam could effectively restrict the out-of-plane deformation of deck and U-rib.