Shear Strength Evaluation of Ultra-High-Performance Fiber Reinforced Cementitious Composite Beams with Compressive Strengths up to 300 N/mm²

Abstract

The development of ultra-high-performance fiber-reinforced mortars has prompted extensive research on their performance and structural applications. The development of high-performance fiber-reinforced mortar dates to the 1980s in Europe. A major milestone was achieved around the year 2000 with the commercialization of high-performance fiber-reinforced mortars exhibiting compressive strengths (f’_c) of 180 N/mm², later applied to structural and architectural components. Currently, there is increasing demand for fiber-reinforced mortars with approximately f’_c = 100 N/mm² offering improved economy and constructability, while materials exceeding 300 N/mm² have also emerged. However, comprehensive and rational design guidelines applicable across this diverse range of materials have not yet been established. This study proposes a shear strength evaluation formula for RC/PC beams without stirrups, fabricated using ultra-high-performance fiber-reinforced mortar (UHPFRM) with f’_c values of 100 to 300 N/mm² and 2 vol.% steel fibers. Finite element analyses were conducted to reproduce shear behavior, resulting in the development of an analytical model to predict UHPFRM beam behavior. Parametric analyses evaluating f’_c, span-depth ratio, effective depth, longitudinal reinforcement ratio, and prestress clarified their influence on shear strength. Furthermore, regression analysis of experimentally measured diagonal crack angles yielded an evaluation formula that accounts for longitudinal reinforcement ratio and prestress. Based on these findings, an improved shear-strength evaluation formula was developed and validated against experimental results.