Lessons learnt from blind competition of shear behavior of fiber‐reinforced concrete T‐beam

Abstract

The positive effect of fiber‐reinforced concrete (FRC) on shear capacity of reinforced concrete beams is well presented in many experimental studies since 1970s. However, as the main effect of fibers is in the cracking stage, it increases the complexity to analyze such structures numerically. With the increased availability of nonlinear finite element analysis software, structural designers are encouraged to use them to solve complex structural problems. In such cases, understanding and correct definition of material laws in cracked stage of FRC structures are crucial. A blind competition was organized by fib WG 2.4.2 to address this issue. It revealed that the numerical predictions of almost all of the participants overestimated the shear capacity of a T‐beam subjected to bending. The aim of the current study is to demonstrate critical aspects in the definition of input parameters of FRC analysis. A comprehensive parametric analysis is performed considering tensile softening law, shear stiffness, and shear strength definition in cracked stage as well as shrinkage effects. The results suggest that most important aspect is the correct definition of tensile softening law, which should correspond to the lower bound of residual strength obtained by standard notched prisms tests according to EN 14651 or even smaller.