Prefabricated prestressed variable truss to strengthen RC beams based on the concept of geometrically unstable system

Abstract

A new prefabricated prestressed variable truss (PPVT) system based on the concept of geometrically unstable system is proposed for the strengthening of reinforced concrete (RC) beams. The advantages of truss and external prestressing can be combined in this system. The novelty of the system lies in that the external prestressing is applied through a variable truss during the assembly process rather than the final stability truss, which improves both the utilization of prestressing and the cooperativity between truss and beam. An experimental test is performed in the present study to investigate the strengthening efficiency of the proposed PPVT system. The effects of the anchorage strength of external prestressing and the pre-damage of structure on the strengthening efficiency of the system are also discussed. Results show that the structural behaviors of RC beams after strengthened by PPVT system are significantly improved. In the present test, the crack resistance and bearing capacity of the beams after strengthening increased by 210% and 125%, respectively. The anchorage strength has a slight effect on the strengthening efficiency of the PPVT system, but can affect the deformation of beams. The PPVT system has an excellent strengthening effect on the pre-damaged members, and even can increase the bearing capacity of the completely damaged beam by 108%.