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

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.