Experimental Study on Cyclic Behavior of SFCBs with Different Slenderness Ratios

Abstract

This paper presents an experimental study on the cyclic behavior of steel-fiber-reinforced composite bars (SFCBs) with different slenderness ratios. Twenty-four specimens, including SFCB specimens and corresponding inner steel bar specimens, were designed and tested under cyclic loading. The cyclic tests of the SFCBs proved that their tensile and compressive behaviors were almost identical before the outer fiber layer started splitting or fracturing. Excellent restorability of SFCBs was observed during the hysteretic process. The compressive peak stress of the SFCBs was irrelevant to specific loading modes, i.e., monotonic loading or cyclic loading. The maximum absolute value of the compressive peak stress of the SFCBs (under cyclic loading without lateral confinement) was approximately 50% of their tensile peak stress (under monotonic tensile loading). A bidirectional degradation effect, which could lead to a rapid decrease in strength, was found during the cyclic loading after the fiber’s initial failure. Therefore, a complete fiber failure mode was suggested for the seismic design of the SFCBs once the fiber layer started failing. A new set of simplified hysteretic rules of SFCBs was proposed based on the actual hysteretic properties summarized from the experimental studies. The new hysteretic rules subdivided unloading and reloading curves into two stages based on the stress state variation of the different SFCB materials, and their accuracy was further verified with the test results.