钢丝脆断后钢绞线吊杆对称断丝力学行为

Mechanical Behaviour of Damaged Strand Suspender with Symmetric Broken Wires in Arch Bridges

摘要:

基于断丝前后吊杆两端边界位移约束条件不变的相容条件，确立对称钢丝脆断后钢绞线吊杆截面内力重分布规律，并推导对称断丝后钢丝应变与影响长度、吊杆拉力损失率之间的关系表达式.结果表明：对称断丝后，在影响长度内各钢丝拉力分布不均匀，与断丝相邻的外层未断钢丝拉力增大，而与断丝相对的钢丝拉力减小，其余钢丝拉力变化不显著；在影响长度外，各钢丝拉力分布又变为均匀.随到断裂处距离的增加，断丝拉力呈指数或线性增加，而与断丝相邻钢丝则呈指数或线性衰减.在影响长度范围内，钢绞线拉力损失率基本为一限值，略低于钢绞线内钢丝断丝率，而护套握裹力、摩擦力等对吊杆内力重分布影响显著.

Abstract:

The mechanical behaviour of a damaged strand suspender with symmetric broken wires is studied. Based on the compatibility condition that the total suspender elongation before and after wire breaks must be the same because it is “locked in” by the anchorages, the stress redistribution of a damaged suspender with symmetric broken wires is identified. Expressions are derived for the wire strains, the affected length, and the remaining prestressing fraction. Results show that forces of the broken and unbroken wires of the suspender are not equal within the affected length, especially, at the break, but equal beyond the length. The strains of unbroken wires within the affected length are not uniform. The maximum strains occur to the two unbroken wires adjacent to the broken wires and the minimum strains at the unbroken wires opposed to the broken wires. The strain of the broken wire is zero at the wire break and increases exponentially with distance from the break. The strain of the unbroken wires is a maximum at the wire break and decreases exponentially with distance from the break. Within the affected length, the remaining prestress fraction approaches a lower limit, which is equivalent to or less than the loss of the cross sectional area of the suspender. Meanwhile, the stress redistribution of a damaged suspender is significantly affected by contact forces between the sheathing and outer wires and frictions between the broken wires and the king wires.