Earthquake-Resistant Fiber Reinforced Concrete Coupling Beams Without Diagonal Bars

Results from large-scale tests on fibre-reinforced concrete coupling beams subjected to large displacement reversals are reported. The main goal of using fibre reinforcement was to eliminate the need for diagonal bars and reduce the amount of confinement reinforcement required for adequate seismic performance. Experimental results indicate that the use of 30 mm long, 0.38 mm diameter hooked steel fibres with a 2300 MPa minimum tensile strength and in a volume fraction of 1.5% allows elimination of diagonal bars in coupling beams with span-todepth ratios greater than or equal to 2.2. Further, no special confinement reinforcement is required except at the ends of the coupling beams. The fibre-reinforced concrete coupling beam design was implemented in a high-rise building in the city of Seattle, WA, USA. A brief description of the coupling beam design used for this building, and construction process followed in the field, is provided

Earthquake-resistant fibre-reinforced concrete coupling beams without diagonal bars

Results from large-scale tests on fibre-reinforced concrete coupling beams subjected to large displacement reversals are reported. The main goal of using fibre reinforcement was to eliminate the need for diagonal bars and reduce the amount of confinement reinforcement required for adequate seismic performance. Experimental results indicate that the use of 30 mm long, 0.38 mm diameter hooked steel fibres with a 2300 MPa minimum tensile strength and in a volume fraction of 1.5% allows elimination of diagonal bars in coupling beams with span-todepth ratios greater than or equal to 2.2. Further, no special confinement reinforcement is required except at the ends of the coupling beams. The fibre-reinforced concrete coupling beam design was implemented in a high-rise building in the city of Seattle, WA, USA. A brief description of the coupling beam design used for this building, and construction process followed in the field, is provided

Elimination of diagonal reinforcement in earthquake-resistant coupling beams through use of fiber-reinforced concrete

The design of reinforced concrete coupling beams in regions of high seismicity typically includes the use of diagonal bars designed to resist the entire shear demand, along with closely spaced transverse reinforcement to provide concrete confinement and diagonal bar support. While results from experimental investigations indicate that this design leads to stable behavior under large displacement reversals, the required reinforcement detailing is labor intensive and time consuming. One alternative that has been proven successful to simplify reinforcement detailing in coupling beams is the addition of discontinuous, deformed steel fibers to the concrete. Test results indicate that elimination of diagonal reinforcement, along with substantial reductions in confinement reinforcement over most of the beam span, are possible in coupling beams with span-to-depth ratios greater than or equal to approximately 2.2 when a tensile strain-hardening fiber reinforced concrete is used. Given the advantages of eliminating diagonal reinforcement in coupling beams, this new design was incorporated in high-rise structures in the State of Washington, USA, starting in the early 2010s. In this paper, a brief summary of relevant experimental results and the implementation of fiber reinforced concrete coupling beams in high-rise earthquake-resistant construction is provided