Friction-slip: an efficient energy dissipating mechanism for suddenly released prestressing bars

The movement of high tensile smooth prestressing bars cast in cement or mortar grout has been studied experimentally on instrumented beam models. Release of load was achieved by a cutting mechanism positioned at one end of the model. Time history signals of load and axial strain in the bar were recorded and analysed using a computer containing a high speed analogue to digital converter and advanced data acquisition and processing software. Analytical simulation of the experiments was carried out using Oasys-DYNA3D Finite Element package. The test and FEA results have both indicated that because of the high energy dissipating feature of the friction-slip mechanism at the bar–grout interface, the movement of the bars was limited despite the generation of longitudinal splitting in the surrounding grout.