钢桥面板U肋嵌补段对接焊缝多轴疲劳特征

Multiaxial fatigue characteristics of U-rib butt weld in steel bridge deck

为了研究U肋对接焊缝多轴疲劳特征,建立了钢桥面板节段模型与对接焊缝子模型,得出不同工况下对接焊缝上各关注点的应力状态。通过平板模型的单、多轴疲劳应力对比,提出了采用绝对值最大的主应力与主要应力分量的偏差作为评判多轴疲劳的依据。然后对U肋对接焊缝进行了受力分析与变形分析,并对比了影响该细节多轴疲劳的主要因素。研究结果表明:纵桥向正应力、截面弯曲剪应力和顶板厚度方向正应力的量值较大,是引起对接焊缝多轴疲劳开裂的重要原因;U肋弯曲应力占膜应力的比例很小,对接焊缝多轴疲劳开裂主要由面内变形引起;多轴疲劳效应随荷载中心线偏离U肋对称轴越发显著,单轴疲劳仅为荷载中心线与U肋对称轴重合时,在U肋对称中心点产生的瞬时效应。

The steel bridge deck was modeled to study the multiaxial fatigue characteristics of U-rib butt weld.The stress state of U-rib butt weld was obtained by submodel under different working conditions.The deviation between the principal stress with the greatest absolute value and the main stress component was proposed to assess the multiaxial fatigue according to comparison of uniaxial and multiaxial stress in the plate model.The stress and deformation of U-rib butt weld were analyzed and factors which have influence on the multiaxial fatigue performance were compared.The results show that the longitudinal normal stress, shear stress in the cracking section and normal stress in the direction of deck thickness are great, which are main reasons for the multiaxial fatigue cracks in the U-rib butt weld.The bending stress accounts for a small proportion of the membrane stress, indicating that the fatigue cracks of U-rib butt weld were induced by in-plane deformation.The multiaxial fatigue effects increase with loading center deviating from the symmetric axis of U-rib. The uniaxial fatigue is only an instantaneous state when the centerline of load coincides with that of U-rib.