Effect of Bond Properties on the Behavior of FRP-Strengthened RC Girders Subjected to Monotonic and Cyclic Loads


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Title: Effect of Bond Properties on the Behavior of FRP-Strengthened RC Girders Subjected to Monotonic and Cyclic Loads

Author(s): Feifei Lu and Ashraf Ayoub

Publication: Special Publication

Volume: 258


Appears on pages(s): 117-136

Keywords: Carbon Fiber, Laminates, Interface, Debonding, Finite Element Analysis, Degradation, Seismic Analysis

Date: 12/1/2008

Externally bonded carbon fiber reinforced polymer (CFRP) is a feasible and economical alternative to traditional methods for strengthening and stiffening deficient reinforced and prestressed concrete bridge girders. The behavior of bond between FRP and concrete is the key factor controlling the behavior of these structures. Several experiments showed that debonding failure occurs frequently before FRP rupture and therefore the FRP strength can not be fully utilized. For design accuracy, the FRP strength must be reduced. This paper analyzes the effect of the bond properties on the response and failure modes of FRP-strengthened RC beams. A nonlinear RC beam element model with bond-slip between the concrete and the FRP laminates is used to analyze a test specimen subjected to monotonic and cyclic loads typical of seismic excitations, and to investigate the corresponding failure mode, and whether it is due to FRP rupture, debonding, or concrete crushing. The model is considered one of the earliest studies to numerically evaluate the behavior of FRP-strengthened girders under seismic loads. The model was also used to study the reduction factor of FRP tensile strength of simply supported strengthened RC girders due to debonding failure. This reduction factor seems to be directly affected by the bond strength between FRP and concrete interface. The study concludes with a numerical evaluation of the current ACI-440 guidelines for bond reduction factors.