美国新泽西州马纳霍金海湾大桥的疲劳问题

Fatigue Problem of Manakawkin Bay Bridge in New Jersey,the United States

美国新泽西州72号公路马纳霍金海湾大桥的上部结构由17跨连续及悬臂铆接钢板梁和横梁系统组成,其中包括5跨销钉-吊杆悬挂梁。由于桥梁的"结构性能不足",20世纪90年代初对大桥进行了系统的修复工作。修复实施过程中,在很多部位发现了疲劳裂纹和桥面板混凝土剥落,疲劳裂纹主要为出现在横梁腹板的水平裂纹、横梁与主梁间托板连接角钢处的竖向裂纹。采用钻孔止裂并在随后的定期检查中采用电化学疲劳传感器(EFS)进行疲劳裂纹生长监测,监测发现疲劳裂纹的数量及规模都在持续增长,且有些裂纹又在既有的钻孔上继续生长。推断疲劳损伤是由于活载以及温度变化时在混凝土桥面板与主梁上翼缘之间产生的相对位移引起的反复面外弯曲造成的。

The superstructure of Rt. 72 Manakawkin Bay Bridge in New Jersey, the United States consists of seventeen riveted steel spans, continuous, cantilevered girder and floor beam system with five pin/hanger suspended spans. Since the bridge was structurally deficient, reha- bilitation work was carried out in early 1990s. During rehabilitation, fatigue cracks and deck haunch damage were found at numerous locations. The fatigue cracks were all similar, that is, horizontal cracks in the floor beam webs and vertical cracks in the floor beam-to-girder bracket connection angles. The horizontal cracks have been repaired by hole-drilling method and moni- tored in each following routine inspection by electrochemical fatigue sensor （EFS）. Over the years, the number and extent of the fatigue damage has been continuously increased since they were first reported. Some cracks further propagated beyond the previously drilled holes, it ap- pears that fatigue cracks and deck haunch spalling were due to out-of-plane bending resulted from relative displacement between the concrete deck and the top flange of the girder as live load passes across the bridge as well as the differential temperature movement.