Experimental investigation on the tensile performance of resin-filled steel pipe splices of BFRP bars

Abstract

The absence of effective connection methods for FRP (fiber reinforced polymer) bars is one of the limitations that restricts the widespread use of FRP bars in civil engineering. In view of this, a simplified connection method with the form of resin-filled steel pipe is proposed in the paper for FRP bars. Based on the tensile tests of 37 resin-filled steel pipe splices of BFRP (basalt fiber reinforced polymer) bars, the tensile performance of the proposed connection method was systematically investigated with the variables of epoxy resin type, epoxy resin layer thickness, BFRP bar diameter and BFRP bar anchorage length. The test results showed that, for splices with the same sectional configuration, the failure mode varies from BFRP bar pullout to BFRP bar rupture with the increase of the BFRP bar anchorage length. And for specimens fabricated with different BFRP bars in diameter, the critical anchorage length increased dramatically with the increase of the BFRP bar diameter. Besides, the tensile performance of the splices improved gradually with the increase of the epoxy resin layer thickness before 3 mm reached. In addition, the relative slip between the steel pipe and the BFRP bar is significantly affected by the elastic modulus of the grouted epoxy resin. The higher the elastic modulus is, the lower the relative slip is and vice versa. At last, an analytical method for calculating the ultimate tensile capacity of the resin-filled steel pipe splices of FRP bars is proposed based on a simplified bi-linear bond-slip model. The effectiveness of the method is verified with the comparison between the tested results and calculated ones.