钢桁架桥开裂横梁节点足尺疲劳试验研究

Full-scale Fatigue Tests on Cracked Beam Joints of Steel Truss Bridge

文中基于钢桁架桥实桥裂纹检测结果,选择全桥最大实测裂纹处的横梁与纵梁的节点制作足尺试件,进行钢横梁节点开裂前后和用栓接钢板加固前后的多组试件比照的疲劳试验,并基于试件疲劳试验的理论损伤度计算结果进行了加固后节点疲劳性能评估.研究结果表明:钢桁架横梁节点裂纹采用的栓接钢板加固方式对横梁开裂的局部区域应力幅改善显著,在试验荷载工况下,原裂纹几乎不再扩展;各试件破坏时的理论损伤度研究表明:加固后梁的整体寿命提高近8%.试件破坏过程表明在继续承受大应力幅疲劳荷载作用下,梁会在新的薄弱位置形核新的裂纹,可能出现新裂纹的易损部位主要包括肋板下端焊缝、下翼缘板螺栓开孔中心和下翼缘板贴钢板的边缘.

Based on the crack detection results of steel truss bridge,full-scale specimens were made at the joints of beams and longitudinal beams at the largest measured crack of the whole bridge,and fatigue tests were carried out before and after cracking of steel beam joints and before and after reinforcement with bolted steel plates.The fatigue performance of reinforced joints was evaluated based on the theoretical damage degree calculation results of fatigue tests.The research results show that the bolted steel plate reinforcement method for the crack of steel truss beam joints can significantly improve the local stress amplitude of the beam crack.Under the test load condition,the original crack almost no longer propagates.The theoretical damage degree study of each specimen shows that the whole life of the strengthened beam is increased by nearly 8%.The failure process of the specimen shows that the beam will nucleate new cracks at new weak positions under the action of fatigue load with large stress amplitude.The vulnerable parts where new cracks may appear mainly include the weld at the lower end of the rib plate,the bolt hole center of the lower flange plate and the edge of the steel plate attached to the lower flange plate.