A theoretical and experimental study on the pre-tensioning and anchorage of composite materials based on shape memory alloys

Prestressing technology can not only improve the bearing capacity of beam but also improve the utilization rate of carbon fiber-reinforced polymers (CFRPs). However, the existing prestressing and anchorage devices are complicated and have many components, which makes the construction process time-consuming and labor-intensive. In this study, a new tensioning technique based on the shape memory effect of shape memory alloy (SMAs) is proposed to simplify the prestressing process. A theoretical model of SMA-controlled recovery for prestressing is established, and the iterative solution of the theoretical model with multi-variable coupling is obtained. The tension anchorage device used in the new technology is designed based on the proposed theoretical model. Finally, the proposed theoretical model is used to simulate the prestressed CFRP reinforcement of a steel beam, and the SMA actuator manufactured from Ni55.2Ti44.7 is used for pre-tensioning and anchorage of CFRP plate on a steel beam. Further, the size of the prestressed CFRP plate is measured during the tensioning and anchorage process. The results verify that the proposed pre-tensioning and anchorage technique can exert the expected prestress force on the carbon fiber plate, and the accuracy of the established theoretical is also validated by comparing the experimental and theoretical results.