Seismic Behavior of Beam–Column Joint Using Hybrid Fiber Reinforced High-Strength Concrete

Abstract

Experimental studies on the seismic behavior of exterior beam–column joint specimens are presented in this paper. Two types of joint detailing were taken into account for this study. Type-1 specimens were detailed as per IS: 13920-1993 and were cast with high-strength concrete of grade M60. Longitudinal reinforcements in Type-2 beam specimens were adopted at standard 90° bent anchorage as per ACI 318-2005, without hoop reinforcements within the joint core. Uniform spacing of transverse reinforcement was maintained for beam and column. These specimens were cast in two ways: using plain high-strength concrete of grade M60 and fiber reinforced high-strength concrete with steel fibers of volume fractions 0.5, 1.0, 1.5 and 2.0%. Studies were also conducted using steel and polyolefin straight fibers (hybrid fibers) with 80–20 and 60–40% combinations for each volume fraction. All the specimens were subjected to forward cyclic loading. During the tests, first crack load, ultimate load and deflections were noted. From the test results, ductility factor, energy absorption, energy dissipation and stiffness degradations were determined for all specimens. It is found that Type-2 specimens with hybrid fiber combination of 80–20% gave better performance compared to other parameters in each volume fraction. The same combination of fibers at 2.0% volume fraction yielded results comparable to the seismic—detailed plain high-strength concrete specimen in terms of strength, ductility factor, energy absorption and stiffness.