拱桥钢绞线吊杆不对称断丝后的力学行为

Mechanical Behavior of Damaged Strand Suspender with Asymmetric 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，建立了不对称断丝后钢绞线吊杆的损伤力学模型，并推导了不对称断丝后钢丝应变与影响长度、吊杆拉力损失率之间关系的表达式.结果表明：不对称断丝后，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，其余钢丝拉力变化与断丝形式显著相关，在影响长度外各钢丝拉力分布又变为均匀；随着到断裂处距离的增加，断丝拉力呈指数或线性增加，而与断丝相邻钢丝拉力则呈指数衰减.在影响长度范围内，钢绞线拉力损失率基本为一限值，略高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.

关键词:拱桥;吊杆;不对称断丝;力学模型;内力重分布

Abstract:

A mechanical model is proposed to describe the behavior of a damaged strand suspender with asymmetric broken wires in this paper, and the relations between the coefficient of interwire friction, the external contact force between sheathing and wires, the affected length of the suspender with broken wires, and the remaining tensile force of the suspender are investigated. Results show that forces in the broken and unbroken wires of the suspender are not equal over the affected length, centered at the break, but are equal beyond. The unbroken wire strains within the affected length are not uniform and have maximum strains occurring in the unbroken wires adjacent to the broken wires, but the rest of unbroken wires are significantly associated with the forms of broken wires. The strain in the broken wire is zero at the wire break and increases exponentially with distance from the break. The strain in 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 a little more than the loss of the crosssectional area of the suspender. Meanwhile, the stress redistribution of a damaged suspender with asymmetric broken wires is significantly affected by contact forces between sheathing and outer wires, and frictions between broken wires and king wires.

Key words:arch bridge; suspender; asymmetric broken wire; mechanical model; stress redistribution