空间缆索悬索桥吊索断裂时的强健性分析

Analysis on Robustness of Spatial Cable Suspension Bridge with Fracture of Slings

悬索桥吊索是整个结构较为薄弱的位置,吊索突然断裂对相邻吊索存在巨大冲击,内力在短时间内迅速增大,存在破坏的风险,从而影响整个桥梁结构安全。依托空间缆索悬索桥宝塔坪特大桥,在有限元分析软件ANSYS中建立结构空间模型,采用杀死单元的方式使特定位置的吊索退出工作。考虑结构阻尼的影响,进行瞬态非线性时程分析,研究空间缆索悬索桥不同位置、不同数量吊索断裂时,相邻吊索瞬时内力响应情况以及整个结构的强健性。结果表明:单根吊索断裂时,对左右两侧相邻3根吊索的内力扰动较大,更远处的吊索在内力重分布平衡之后,其内力值变化很小;吊索断裂位置越往跨中靠拢,相邻吊索的损伤动力响应越大,结构破坏风险以及安全隐患越高;跨中同侧连续两根吊索同时断裂时,相邻吊索的瞬时损伤动力超过吊索的破断力,断索瞬间有一定概率导致相邻吊索也发生断裂,进一步可能引起邻近吊索依次连续断裂,最终导致结构破坏。因此有必要在跨中短吊杆处设置中央扣或者采用刚性短吊杆,防止跨中短吊杆疲劳破坏,达到提高结构强健性的目的,同时有必要加强跨中短吊索的疲劳检测频率。

The slings of suspension bridge are the weak position of the whole structure.The sudden fracture of sling has a huge impact on the adjacent slings,and the internal force increases rapidly in a short time,and there is a risk of damage,which affects the safety of the whole bridge structure.Based on the spatial cable suspension bridge(Baotaping Grand Bridge),the structural spatial model is established by the FE analysis software ANSYS,and the sling at a specific position is taken out of work by killing the element.Considering the influence of structural damping,the transient nonlinear time history analysis is conducted to study the instantaneous internal force response of the adjacent slings and the robustness of the whole structure when different positions and numbers of slings are broken.The result shows that(1)the internal forces of the 3 adjacent slings on the left and right sides is disturbed greatly by the fracture of a single sling,and the internal force of the more distant slings change little after the internal force redistribution is balanced;(2)the closer the sling fracture position is to the mid-span,the greater the damage dynamic response of the adjacent slings,and the higher the risk of structural damage and potential safety hazard;(3)when 2 consecutive slings on the same side of the mid-span are fractured at the same time,the instantaneous damage power of adjacent slings exceed the breaking force of the slings,and there is a certain probability that the adjacent slings will fracture at the moment of breaking,which may further cause the adjacent slings to fracture successively and finally lead to structure damage.Therefore,it is necessary to set a central buckle or use a rigid short sling at the mid-span short suspender to prevent the fatigue failure of the short sling at mid-span,o as to improve the structural robustness,meanwhile,it is necessary to strengthen the fatigue detection frequency of mid-span short sling.