Retrofitting Actual-Size Precracked Precast Prestressed Concrete Double-Tee Girders Using Externally Bonded CFRP Sheets

摘要

Precast prestressed double-tee (DT) girders are considered a crucial element of modern infrastructure used to accelerate building construction worldwide. These girders can be deficient because of local damages and develop cracks as a result of improper transportation and handling. Therefore, it is very important to develop an efficient retrofitting technique in order to restore the lost capacity and/or even outperform it. The objective of this paper is to develop retrofit strategy of the deficient girders using the externally bonded carbon-fiber-reinforced polymer (EB-CFRP) technique and verify it using field data. A field test was conducted on three actual-size precast pretensioned DT girders having different levels of damage and retrofitted using CFFP sheets. The girder stems for two of them were strengthened in flexure using unidirectional U-shaped CFRP sheets, while all girders were shear-strengthened at their dapped ends. Each girder was loaded incrementally up to collapse while the deflection of the girder and normal strains developed on both concrete surface and the CFRP sheets were recorded at each load increment. Test results assured the adequacy of the adopted strengthening technique with respect to both ultimate capacity and ductility. In addition, the experimental flexural and shear resistances of the retrofitted girders are far greater than those obtained from equations available in design codes by at least 60%.