Fracture Characteristics of Notched Concrete Beams Shear-strengthened with CFRP Sheets Subjected to High Temperature

摘要

This paper presents the residual fracture characteristics of concrete beams shear-strengthened with carbon fiber reinforced polymer (CFRP) sheets subjected to high temperature ranging from 25°C [77°F ] to 200°C [392°F] for three hours. The beams are intentionally unreinforced to focus on strengthening effects. Three levels of initial shear deficiency are simulated by notching the beams: a0/h ratios = 0.25, 0.38, and 0.50 where a0 is the notch depth and h is the beam height. Ancillary tests are conducted to examine the temperature-dependent residual material properties of concrete, CFRP, and epoxy-concrete interface. Empirical equations are then generated to predict such properties for a potential modeling purpose. The interfacial fracture capacity is significantly affected by the level of temperature exposure, including two different failure modes such as failures at the concrete substrate and within the adhesive layer. CFRP debonding, associated with diagonal tension cracking of the concrete, is the primary source of the failure of the strengthened beams. High temperature exposure above the glass transition temperature (T_g) of the adhesive accelerates the bond failure. Energy dissipation of the strengthened beams is influenced by the elevated temperatures. The contribution of the CFRP to compliance variation is, however, not significant.