Title: On Punching Shear Strength of Steel Fiber-Reinforced Concrete Slabs-on-Ground

Author(s): Raphael Palmier Manfredi, Flávio de Andrade Silva, and Daniel Carlos Taissum Cardoso

Publication: Structural Journal

Volume: 119

Issue: 4

Appears on pages(s): 185-196

Keywords: crack kinematics; punching shear; slabs-on-ground; steel fiber-reinforced concrete (SFRC)

DOI: 10.14359/51734520

Date: 7/1/2022

Abstract:
The work in hand presents the results of an experimental investigation on the punching shear performance of steel fiber-reinforced concrete (SFRC) slabs-on-ground, a problem that has received little attention worldwide. In the first part of the experimental program, residual strengths are obtained according to different methodologies, namely EN 14651 and ASTM C1609, considering normal concrete matrixes reinforced with hooked-end steel fibers in contents of 20, 30, and 40 kg/m3 (33.71, 50.56, and 67.42 lb/yd3). Then, three slabs-on-ground were fabricated (one for each content) and tested for a central single-point load and it was confirmed that the use of fibers increased ultimate load and ductility. The results are compared with those obtained using the predictions of the fourth edition of Technical Report 34 (TR 34) issued by The Concrete Society, and differences of less than 10% are observed. The influence of rotation and relative displacement between the central shear cone and surrounding slab are studied, confirming the relevance of the latter to the crack kinematics. A simple mechanical model is proposed, revealing that the contributions of each load-transfer mechanism according to TR 34 are unrealistic and that the fiber action responds roughly for 40% of the capacity. Finally, design recommendations are proposed to account in a meaningful way for the actual contributions of concrete, fibers, and subgrade to the punching shear strength.