Punching shear in concrete reinforced flat slabs with steel fibers and shear reinforcement

T H Musse,G N Guimarães,L M Trautwein,R B Gomes,E A P Liberati

doi:10.1590/s1983-41952018000500011

T H Musse, G N Guimarães + Show 3 more

Open Access

https://doi.org/10.1590/s1983-41952018000500011

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Abstract

Abstract Steel fibers in reinforced concrete increase the performance of slab-column connection once they increase ductility and energy absorption capacity of the concrete. The use of fibers in flat slabs may increase strength and change the mode of failure. The objective of this work is to present an experimental evaluation of punching shear strength of reinforced concrete flat slab with steel fibers and punching shear reinforcement. Eight square slabs, size 1800 mm by 1800 mm by 130mm, were loaded until failure by punching shear around the column. The models were divided in two groups, depending on the type of the concrete used (with or without steel fibers). The steel fiber volume used in the slabs of second group was of 0.9%. Each group was composed of four slabs: one without shear reinforcement and three with shear reinforcement (studs) distributed radially around the column. The use of steel fibers increased the ultimate strength of all flat slabs. In one of the slabs, the association of steel fibers with shear reinforcement changed the failure surface from outside to inside the punching shear reinforcement region.

Highlights

Flat slabs, called flat plates, are structurally reinforced or prestressed concrete slabs supported directly by the columns, without the existence of beams (NBR 6118:2014)
Ultimate loads were 33% higher for slab LF2 compared to slab LF1; both slabs with fibers
The main variables in this study were the use of steel fibers in the concrete and use of shear stud reinforcement

Summary

Introduction

Called flat plates, are structurally reinforced or prestressed concrete slabs supported directly by the columns, without the existence of beams (NBR 6118:2014). Their use has been common for decades, mostly due to the simplicity of the structural system, construction costs and execution time, and flexibility of construction space (Albuquerque, 2010; Nguyen-Minh et al 2011). Punching shear failure may occur in thin slabs under concentrated loads leading to high shear stresses in small regions around the columns Albuquerque, 2010; Nguyen-Minh et al 2011). The use of fibers to increase shear strength of reinforced concrete has been widely studied as shown in research done by Choi et al (2007), Hanai and Holanda (2008), Cheng and ParraMontesinos (2010), Maya et al (2012) and Gouveia et al (2014)

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