Experimental and analytical evaluation of shear strength in steel-fiber-reinforced concrete conventional coupling beams

Abstract

This study examines the shear performance of reinforced concrete (RC) coupling beams with conventional details reinforced with steel fibers. Experimental tests showed that the fiber inclusion enhanced the shear strength by modifying the diagonal crack angle and increasing the shear contribution of the transverse reinforcement. A nonlinear finite element analysis (FEA) using DIANA FEA was conducted to verify these mechanisms and investigate the key parameters. The results closely matched the experimental data in terms of the maximum strength and crack patterns, although the post-peak behavior remained difficult to capture. A parametric study confirmed that the strength improved with higher fiber volume fractions, with notable gains of 1%, whereas the influence of the longitudinal reinforcement decreased. Finally, comparisons with existing design equations indicated that the softened strut-and-tie model yielded the most accurate predictions, while the fib Model Code 2020 equation provided rational and conservative estimates suitable for design.