钢箱梁横隔板疲劳裂纹特征与实桥试验的轮载应力

The fatigue crack characteristics and wheel load stresses of steel box girder diaphragms in an existing bridge

弧形切口处横隔板母材开裂是正交异性桥面板钢箱梁常见的疲劳病害。因研究方法的局限性,对其疲劳机理尚缺乏公认的认识。对此,考察并给出了两个背景工程的横隔板疲劳裂纹特征;针对无裂纹横隔板,进行了现场多种纵横向移动布载工况的轮载试验及相应的FEA计算,给出了结果及其规律。研究表明:(1)横隔板母材开裂常出现在远离U肋的上起弧点附近;开裂后,裂纹两侧的横隔板常有平面外的错动;(2)远离U肋的上起弧点附近横隔板的轮载应力始终为压应力,且应力绝对值最大;与U肋交界附近横隔板的轮载应力始终为拉应力,应力值次之;(3)横隔板平面外弯曲变形引起的应力相对膜应力很小,特别是弧形切口周边的潜在起裂处,两表面应力差几乎为0;(4)横隔板母材起裂处的压应力方向与裂纹方向几乎垂直;(5)顶板厚16mm、U肋厚10mm的背景工程,紧邻横隔板的U肋轮载应力不超过22MPa,应力幅小,几乎无疲劳开裂风险;(6)弧形切口周边轮载应力的最不利纵向加载位置为纵向距该横隔板约1倍的U肋间距;稍远处轮载应力的最不利纵向加载位置为其正上方。

The cracks in the diaphragm arc incision are common fatigue diseases of orthotropic steel deck. Due to the limitations of research methods, there is no general recognition for the fatigue mechanism of the diaphragm as yet. Thus, the characteristics of diaphragm fatigue cracks of two existing bridges was given and examined in this paper. The FEA analysis and stress test of a variety of vertical and horizontal moving load conditions for the crack-free diaphragm was conducted,and corresponding results and the laws were given. The research indicates that： （1） The cracking of diaphragm usually initials near the arcing point of far away from the U rib, the surface on both sides of the crack dislocated out of plane. （2） The stress of arcing point far away from the U rib under the wheel load is always compressive, and the absolute value is maximum. The stress on the arc incision near the diaphragm-U rib junction is tensile stress. （3） The stress caused by the out of plane bending is relatively small, especially on the crack potential initiation around the arc incision, where the stress difference between the two surfaces is almost 0. （4） The direction of compressive stress is almost perpendicular to the cracks. （5） For the background project with 16mm-thick roof and 10mm-thick U rib, the stress of U rib near the diaphragm is less than 22MPa, which almost introduce no fatigue risk. （6） The maximum absolute stress on the are incision emerges when the location of the wheels are one U rib spacing from the diaphragm. The longitudinal loading position for maximum absolute value of the farer is just above the diaphragm.