Use of structural steel diagonal reinforcement in coupling beams

Coupling beams are a key structural element for resisting seismic loading because of their energy dissipating capabilities and high ductilities. In coupling beams with short span-to-depth ratios, diagonal reinforcement is used to provide the amount of ductility required. Because of the large amount of steel congestion within traditionally reinforced diagonally reinforced coupling beams, however, alternative reinforcement layouts are desired to simplify their construction. Two specimens were constructed and tested under reversed cyclic loading. The results were then compared to previous experimental results to evaluate the viability of these construction techniques. One specimen contained No. 20 diagonal bars placed in a symmetrical arrangement and confined with closely spaced headed reinforcing bars in place of hoops. The second specimen used diagonal reinforcement constructed using structural steel elements that were anchored in the shear wall elements with shear studs. For comparison, the structural steel elements used in the design of the second specimen were chosen to match the yield force of the diagonal reinforcement of the first specimen.;The hysteretic responses of the two specimens showed that the specimen containing the structural steel diagonal reinforcement had a higher ductility and was able to dissipate more energy than those using headed reinforcing bars or traditional hoops. This indicates that the use of structural steel is a viable alternative for the diagonal reinforcement of coupling beams. In addition, these results also demonstrated that the use of headed reinforcing bars as confinement for diagonal reinforcement is similar to, and therefore a feasible replacement for, diagonal reinforcement confined with closely spaced hoops.