High-strength steel reinforced squat UHPFRC shear walls: Cyclic behavior and design implications

Ultra-high performance fiber reinforced concrete (UHPFRC) is characterized by ultra-high compressive strength and ductile tensile strain hardening behavior accompanied by dense fine cracks. This study experimentally investigated the seismic behavior of squat UHPFRC shear walls. For this purpose, four squat shear walls were tested under displacement reversals, with the experimental variables including the strength of steel reinforcement, shear stress demand for the wall, steel fiber, and dowel bar. In particular, the performance of squat UHPFRC shear walls reinforced with high-strength steel rebar with an actual yield strength above 685 MPa was explored. The seismic behaviors of the squat walls were evaluated using various performance measures, such as the hysteretic response, steel reinforcement strain, stiffness, strength, energy dissipation capacity, and detailed displacement component. The results revealed that the presence of steel fibers enhanced the strength, confinement, and crack-width control ability of squat UHPFRC shear walls, allowing the walls to exhibit ductile flexural-dominant behavior even when the shear stress demand for the wall was 20% greater than the code-specified maximum allowable value. Furthermore, the proposed novel squat shear wall not only took advantage of the ultra-high mechanical properties of high-strength steel and UHPFRC materials, but also resolved the concern of the potential premature failure modes for high-strength reinforcement and concrete.