Prestressingkabels

Prestressingkabels, or prestressing cables, are high-strength steel tendons used to introduce compressive stresses into concrete members. By applying an initial pretension, these cables counteract tensile forces generated during service, reducing crack formation and minimizing deflections. They are central to the construction of prestressed concrete elements such as beams, slabs, and bridges.

Most prestressingkabels consist of strands or wires made from high-strength steel. Common forms include seven-wire strands, multi-strand tendons, and single wires. In post-tensioning projects, tendons pass through ducts embedded in the concrete; in pretensioning, the cables are tensioned before casting and anchored at fixed ends to transfer the prestress when the concrete hardens.

Pretensioning involves tensioning cables against fixed end supports prior to concrete placement, then releasing the anchors after curing so the bond transfers prestress to the member. Post-tensioning places ducts in the formwork, casts the concrete, then threads and tensions the tendons after curing, anchoring them at the ends and often grouting the ducts for protection and stiffness.

Design must account for long-term losses from relaxation, concrete creep and shrinkage, friction between tendons and ducts, and anchorage slip. Material protection includes grease, sheathing, and post-grouting for corrosion resistance. Bonded systems provide local load transfer between steel and concrete; unbonded systems allow greater ductility and faster construction in certain layouts.