Abstract

The increasing demand for sustainable construction materials has encouraged the use of waste-derived crumb rubber (CR) and steel fibers (SF) in reinforced concrete (RC). Although CR can improve ductility and energy absorption, it often reduces compressive strength and shear resistance, raising concerns for shear-critical applications. This study experimentally and analytically investigated the shear behavior of eight large-scale RC beams with 0-12% CR replacement by volume of sand and a constant SF dosage of 0.75% (by volume). To ensure shear failure in the test zone, stirrups were omitted only in the critical shear-span region and provided elsewhere. The beams were tested under four-point bending to assess shear capacity, normalized shear stress, load-deflection response, crack patterns, and failure modes. Results showed that CR alone reduced shear strength by up to 21% compared with the control beam, mainly due to weakened aggregate interlock and bond. However, adding SF increased shear capacity by 20-59%. Based on the experimental results and a combined database, a regression-based shear equation was proposed for steel-fiber-reinforced rubberized concrete beams without stirrups. The model incorporates both a crumb-rubber penalty term, reflecting reduced shear transfer efficiency, and a steel-fiber term, representing crack-bridging resistance. A conservative strength-reduction factor of ϕ = 0.80 was proposed to provide code-consistent design estimates. The study contributes new large-scale shear test data for beams with stirrup-free shear spans and proposes a unified, design-oriented equation that explicitly captures both the adverse effect of rubber and the beneficial contribution of fibers.