Strain rate effect on effective bond length of basalt FRP sheet bonded to concrete

• The dynamic effective bond length of BFRP sheet bonded to concrete is investigated.
• The dynamic elastic modulus of BFRP sheet increases with the increasing strain rates.
• The dynamic effective bond length of BFRP decreases with the increasing strain rates.
• A calculation model of dynamic effective bond length of BFRP is established.

Reinforced concrete structures strengthened by fiber-reinforced polymer (FRP) always suffer dynamic loadings. The success of this strengthening method relies on the effectiveness of the bond between the FRP sheet and concrete. Determination of the bond strength between FRP and the concrete substrate is an important issue in this technology because the typical failure mode of FRP-to-concrete joints involves the debonding of the sheet from the concrete substrate. Most theoretical bond strength models are established based on effective bond length. Therefore, determination of the effective bond length is necessary to determine bond strength. Although numerous experimental studies have investigated this effective bond length, experimental data from dynamic tests on the effective bond length of the interface between basalt fiber-reinforced polymer (BFRP) sheets and concrete under different strain rates remain lacking. This paper presents an experimental investigation of the dynamic effective bond length between BFRP sheets and concrete under different strain rates. Double-lap shear specimens were utilized in the tests. Results of dynamic tests were discussed to evaluate and compare the influence of strain rate on the dynamic effective bond length between BFRP sheets and concrete. Data show that bond stress and effective bond length are sensitive to strain rate. The dynamic effective bond length of the BFRP–concrete interface is affected by both BFRP stiffness and concrete strength. The dynamic elastic modulus of BFRP increases with the increase in strain rate, and the failure mode under different strain rates involves debonding in the concrete layer. The dynamic effective bond length of the BFRP–concrete interface decreases with the increase in strain rate as a logarithmic function. A calculation model of dynamic effective bond length in consideration of the influence of strain rate was established through regression analysis of bond length data.