During pretensioning, how is the prestressing force primarily transferred to the concrete?

During pretensioning, the prestressing force is primarily transferred to the concrete through bond. In this process, high-strength steel tendons are stretched and anchored at the ends of the concrete member before the concrete is poured. Once the concrete hardens, the tension in the steel tends to return to its original length, effectively compressing the concrete along the entire length of the member due to the bond that is developed at the interface where the tendons and concrete contact each other.

This bond is crucial as it ensures that the compressive stresses induced in the concrete coincide with the tensile stresses that the external loads will apply, improving the overall performance of the member under service conditions. Without adequate bond, the prestressing force would not effectively translate into compressive stresses in the concrete, diminishing the structural advantages offered by the pretensioning process.

In this context, shear transfer, friction, and compaction don’t play significant roles in the primary mechanism of force transfer in pretensioned members. Shear transfer is more relevant in post-tensioned systems, friction typically concerns the movement between surfaces and is not a direct transfer mechanism, and compaction relates to the uniformity of the concrete mix rather than to the transfer of prestressing forces. Thus, the method