Experimental Study of Pre-Stress Loss of Steel Structure Strengthened with Pre-Stressed CFRP Strips

This paper focuses on the experimental study on the pre-stress losses of pre-stressing CFRP plates bonded on damaged steel structures. Both pre-tensioned and post-tensioned members are theoretically and experimentally analyzed. The results show that, firstly the instantaneous pre-stress losses due to elastic deformations are up to 50% of the initial pre-stress for the steel plates strengthened with CFRP plate pre-stressed by the pre-tensioned method. The longer length of CFRP plate reduces the instantaneous pre-stress loss significantly. Because of the small value of the long-term pre-stress losses in the test, the approximate estimates of total pre-stress losses can be simplified as the instantaneous pre-stress losses with considering a safety factor. Secondly for the steel girders strengthened with pre-stressing CFRP plate by the post-tensioned method, the effective pre-stress of girder specimens are directly controlled by the anchorage set, and both the instantaneous and long-term pre-stress losses are slight. However the anchorage set with jacking system is rather complicated and difficult to design. From the view of pre-stress losses, the post-tensioned method is more effective than the pre-tensioned method.