The cause and treatment of broken wire of steel strand

The general causes of broken wire of steel strands are: uneven steel strand material or serious corrosion; The steel strand contacts the welding spark or the welding machine wire, and the mechanical properties change; Serious crossover of steel strands near the anchor hole; The anchor deviates from the anchor pad stop point, the middle of the steel strand, or the end of the horn tube has a large bending angle with the bellows, resulting in the stress concentration of individual steel wires; The hardness of the sandwich does not match the steel strand; The tensioner is not checked as required, or the oil pressure gauge is faulty, resulting in excessive tension.
After the wire break, the commonly used treatment methods: first, increase the control tension of other steel strands as compensation; However, it should be noted that in any case, the maximum tensile stress shall not exceed 0.8 times the standard value of the ultimate tensile strength of the steel strand. The second is to change the bundle, that is, unload, anchor, change the bundle, and tension again to the design stress value. Third, use backup bundles if necessary. For long-span prestressed concrete girder bridges, spare holes are often designed and backup bundles can be used when wire breaks are severe.