Fatigue Behavior of Basalt Fiber-Reinforced Polymer Tendons for Prestressing Applications

Abstract

This paper studies the fatigue behavior of high-strength basalt fiber-reinforced polymer (BFRP) tendons for potential applications in prestressed structures. An effective anchoring method of winding fiber sheets was first developed for fatigue testing of BFRP tendons to avoid premature failure at the anchorage. The fatigue stress ranges from 0.05 to 0.14fu (fu = ultimate tensile strength) and maximum stresses from 0.6 to 0.8fu were determined, whereas the elastic modulus of BFRP tendons during the fatigue tests was measured. The fatigue failure mechanism was analyzed and elaborated at both the macro- and microscopic levels. The appropriate fatigue stress range and maximum stress level were predicted from both experimental fitting and reliability analysis. The results show that the fatigue failure of a BFRP tendon is mainly induced by the debonding among fiber-matrix interfaces at the outer layer of the tendon. The fatigue stress range greatly affects the fatigue life of BFRP tendons. The BFRP tendons can sustain 2 million cyclic loadings under a stress range of 0.05fu (85 MPa) and maximum stress of 0.6fu (1,018 MPa). Furthermore, the elastic modulus of BFRP tendons before failure remains constant regardless of the number of cycles. Prediction of fatigue strength (limit of stress range and maximum stress to sustain 2 million cyclic loadings) based on experimental fitting shows a satisfactory consistency with the previously mentioned experimental results (0.05 and 0.6fu). A recommendation of a stress range of 0.04fu (68 MPa) and maximum stress of 0.53fu (899 MPa) are proposed with 95% reliability for BFRP tendons in prestressing applications.