Implementation of Bond Durability in the Design of Flexural Members with Externally Bonded FRP

Externally bonded fiber-reinforced polymer (FRP) composites are becoming a method of choice for the repair/strengthening of civil structures, some of which are situated in environments detrimental to FRP-concrete bond durability. Based on analysis of an extensive database of durability test results from notched-beam three-point bending tests, a bond durability factor (BDF) of 0.60 was identified as an appropriate estimate of bond durability for wet-layup carbon fiber-reinforced polymer (CFRP). This factor was compared to a normalized database of durability data from the literature, and it was found that a 0.60 BDF agrees well with these data. A modified procedure for determining the ultimate design strain primarily in bond-critical applications (such as external flexural and shear FRP reinforcement), is proposed. This procedure makes a distinction between durability properties associated with the FRP rupture and debonding failure modes. When used for practically feasible strengthening ratios and in conjunction with BDF of 0.60, the proposed procedure yields overall ultimate flexural-member design strengths that are 0-15% lower than those determined using current design procedures. (C) 2015 American Society of Civil Engineers.