Bond-Slip Relationship for CFRP Sheets Externally Bonded to Concrete under Cyclic Loading

Area of Science:

• Civil Engineering
• Materials Science
• Structural Engineering

Background:

• Carbon fiber-reinforced polymer (CFRP) composites are increasingly used for strengthening concrete structures.
• Understanding the bond-slip behavior between CFRP and concrete is crucial for structural integrity, especially under cyclic loading conditions.

Purpose of the Study:

• To investigate the bond-slip relationship of CFRP sheets bonded to concrete under cyclic loading.
• To develop an analytical model for predicting CFRP-concrete bond-slip behavior under cyclic conditions.

Main Methods:

• Experimental investigation using modified beam tests under static and cyclic loading.
• Analysis of experimental results and existing data to identify key influencing parameters.
• Development and verification of a bilinear bond-slip model.

Main Results:

• The bond-slip curve's ascending slope decreased with increased load cycles, while peak shear stress slip remained consistent.
• Higher concrete strength reduced the slope reduction rate, whereas increased load level or CFRP-to-concrete ratio accelerated it.
• Bond length did not significantly affect behavior beyond the effective bond length.

Conclusions:

• Cyclic loading degrades the bond-slip performance of CFRP-concrete joints.
• A validated bilinear bond-slip model can accurately predict CFRP-concrete bond behavior under cyclic loading.
• The developed model accounts for critical factors such as concrete strength, load level, and CFRP-to-concrete ratio.