Effect of temperature variation on the full-range behavior of FRP-to-concrete bonded joints

Service temperature variations (thermal loadings) may significantly affect the behavior of the bond between externally bonded fiber reinforced polymer (FRP) and concrete. This paper presents an analytical solution for the full-range deformation process of FRP-toconcrete bonded joints under combined thermal and mechanical loadings. The solution is based on a bilinear bond-slip model and leads to closed-form expressions. The validity of the solution is demonstrated through comparisons with both experimental results and finite-element predictions. Numerical results from the solution are presented to illustrate the effect of thermal loading on the interfacial shear stress and slip distributions in addition to the global load-displacement response. Provided the material properties are not affected by temperature variations, a temperature rise is shown to increase the ultimate load, whereas a temperature reduction decreases the ultimate load; the latter can have serious implications for the safety of the strengthened structure. Although the solution is developed with particular reference to FRP-toconcrete bonded joints, it is also applicable to similar bonded joints made of other materials (e.g., FRP-to-steel bonded joints). A useful function of the closed-form solution lies in the interpretation of pull test results: the solution allows the effect of thermal stresses to be isolated from the effect of property changes of the bondline in obtaining bond-slip responses from pull tests.