Punching of reinforced concrete slab without shear reinforcement: Standard models and new proposal
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RESEARCH ARTICLE
Punching of reinforced concrete slab without shear reinforcement: Standard models and new proposal Luisa PANI, Flavio STOCHINO* Department of Civil, Environmental Engineering and Architecture, University of Cagliari, Cagliari 09123, Italy Corresponding author. E-mail: [email protected]
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© Higher Education Press 2020
ABSTRACT Reinforced concrete (RC) slabs are characterized by reduced construction time, versatility, and easier space partitioning. Their structural behavior is not straightforward and, specifically, punching shear strength is a current research topic. In this study an experimental database of 113 RC slabs without shear reinforcement under punching loads was compiled using data available in the literature. A sensitivity analysis of the parameters involved in the punching shear strength assessment was conducted, which highlighted the importance of the flexural reinforcement that are not typically considered for punching shear strength. After a discussion of the current international standards, a new proposed model for punching shear strength and rotation of RC slabs without shear reinforcement was discussed. It was based on a simplified load-rotation curve and new failure criteria that takes into account the flexural reinforcement effects. This experimental database was used to validate the approaches of the current international standards as well as the new proposed model. The latter proved to be a potentially useful design tool. KEYWORDS
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punching shear strength, reinforced concrete, slabs, reinforcement ratio
Introduction
The use of reinforced concrete (RC) slabs has a number of advantages, including reduced and simpler formwork, versatility, and easier space partitioning. They represent economical and efficient structural systems, but however common their use may be, their structural behavior is not straightforward and has been analyzed over numerous years [1]. It is the subject of current studies that are considering its response under impulsive and blast loading [2–5]. Therefore, the analysis of punching in RC slab is topical for a number of reasons. Punching collapse can be dangerous as it develops with a brittle mechanism and affects the integrity of the structure. A localized punching collapse can result in a general structural failure. A very interesting state of the art report is presented in Ref. [6]. International standards (Eurocode 2 [7], ACI 318 [8], and Model Code 2010 [9]) present different punching models and prescriptions that yield different structural
Article history: Received Jun 18, 2019; Accepted Feb 9, 2020
design results. In addition, if a comparison between theoretical and experimental punching shear strengths [10–20] is conducted, different safety coefficients are obtained. In Model Code 2010 (MC10) [9], the punching shear strength model is based on the critical shear crack theory (CSCT) [21], whereas ACI 318 [8] and Eurocode 2 (EC2) [7] refer to empirical models based on the maximum shear stress. The CSCT also provides an estimate of the slab rotation
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