Behavior of Tendons with Multiple CFRP Rods

Abstract

Research works related to the fiber-reinforced polymer (FRP) tendons have focused on the anchor system, but the anchor is not the only contribution to performance. Since civil structures require tendons consisting of multiple rods (e.g., cables, suspenders in bridges, or rock bolts in ground anchors), the characteristics of multirod tendons require targeted research. This paper presents a study on the behavior of tendons with multiple carbon FRP (CFRP) rods. Four specimens including two cable-type assemblies (TA12-9 and TA12-20) and two ground anchors (GA12-9 and GA12-20) with large-tonnage capacities were built and tested. Using strain gauges set along individual rods, the nonuniform force distribution among individual rods was observed and is discussed. The test results showed that nonuniformity is a recurring feature of a multirod tendon, with the variation in the initial length of the rods caused by installation error as its main reason. Based on the premise that tension in multiple rods obeys a normal distribution, the relationship between the nonuniformity coefficient, η, and a corresponding capacity reduction coefficient, λ, was established. The tendon consisting of nine CFRP rods in TA12-9 (GA12-9) shows a capacity reduction factor of 0.83 (0.89), while the capacity reduction factor of the tendon consisting of 20 rods in TA12-20 (GA12-20) decreases to values of 0.79 (0.87).