Recent bridge inspection statistics
nation wide show that more than a third of the United States’ half million
highway bridges are either “structurally deficient” or functionally obsolete”.
Bridge components are exposed to deterioration effects because they are
directly subjected to environmental conditions, corrosive action, accidental
vehicular impacts, and cyclic load variations. This may cause defects in
concrete bridges including cracking, scaling, spalling, leaching, chloride
contamination, delamination and partial or full depth damage, and lead to
posting load restrictions on the use of bridges. Retrofit and rehabilitation is
essential in order to restore the bridge to its original design load carrying
capacity.
Fiber reinforced polymer (FRP)
composites are increasingly being used for the repair and strengthening of
deteriorated concrete structural components through adhesive bonding of prefabricated
strips/plates and the wet layup of fabric. Concrete structural elements
strengthened with FRP reinforcement can fail in different ways. Bond failure
modes have attracted the attention of the designers besides the classical
failure modes, such as reinforcing steel rebar fracture, concrete crushing, or
shear failure. The objective of the present study is to evaluate the
interfacial bond strength between the FRP composite strip, adhesive and the
concrete under harsh
exposure conditions-namely simulated tidal conditions and
freeze-thaw exposure. The bond strength is experimentally determined by the
peel test and the results compared with those based on finite element stress
analysis. The fracture toughness for debonding is evaluated and expressed as the
critical strain energy release rate.