Shear Behavior Of Concrete Slabs Research Articles

Influence of openings on the punching shear behaviour of concrete slabs supported on special-shaped columns

Punching shear of special-shaped columns supporting reinforced concrete two-way slabs has been addressed in design codes since the late 1970s. While these provisions have existed for over 40 years their basis is unclear as previous studies related to the punching shear behaviour of irregular column geometries, such as L, T, and cruciform shapes, are limited. In this paper, the punching shear behaviour of L, T and cruciform slab-column connections, with or without slab openings near the connection, under concentric vertical loading is studied using a three-dimensional nonlinear finite element model (FEM) implemented in Abaqus/Explicit. The nonlinear FEM, based on the concrete damaged plasticity model, is used to study the influence of both the opening size and location on the punching shear behaviour of special-shaped (irregular) slab-column connections of various sizes. Based on the FEA results, the ideal location for openings around special-shaped slab-column connections (SS-SCCs) is between the column flanges. This location minimizes their negative influence on concentric punching capacity and is also beneficial architecturally. Finally, the accuracy of the ACI 318–19 punching shear provisions is evaluated. Based on the FEA results modifications to the existing provisions are necessary, particularly to account for the location of openings around special-shaped slab-column connections.

Punching shear behaviour of RC flat slabs incorporating recycled coarse aggregates and crumb rubber

This paper presents experimental, analytical and numerical investigations to evaluate the punching shear strength of concrete slabs incorporating a combination of recycled coarse aggregate (RCA) and crumb rubber (CR). Therefore, twelve different concrete mixes were designed with various substitution ratios of RCA and CR as a partial replacement of natural coarse aggregate (NCA) and fine aggregate (FA), respectively. Four substitution ratios of RCA (0%, 25%, 50% and 100%) by NCA and three substitution ratios of CR (0%, 10% and 20%) by FA were considered. Twelve simply supported two-way RC slabs with dimensions of 1000 × 1000 × 100 mm were cast and tested. The experimental programme was divided into two stages. The first and second stages were respectively conducted to evaluate the mechanical properties and the punching shear behaviour of concrete slabs incorporating a combination of RCA and CR. Experimental results show that the combination of RCA and CR negatively affects the mechanical properties of concrete. The substitution ratios of rubber content had a more significant effect on the reduction of the concrete strengths than the RCA content. The punching shear strength, stiffness and toughness of RC slabs incorporating RCA and CR decreased with increasing CR and RCA contents. Based on the experimental results, a combination of 25% RCA and 10% CR is the optimum substitution ratios that can be used on the concrete mixture, as it has a minor effect on the punching shear strength of concrete slab. The predictions of five approaches, namely ACI 318–2014, ECP 203, Euro −2, BS8110 and CSA A23.3, were compared with the experimental results. Finally, nonlinear element analysis (ANSYS) was conducted to verify the experimental results with numerical ones.

Finite element analysis of punching shear behaviour of concrete slabs supported on rectangular columns

Design provisions for punching shear of reinforced concrete flat slabs supported on rectangular columns vary greatly and are typically based on empirical results. Due to the large cost and time required to conduct experimental tests the empirical database for slabs supported on rectangular columns is small. Properly calibrated, nonlinear finite element models (FEM) provide an efficient way to expand experimental databases, conduct parametric studies and verify design provisions. In this paper, the results from a parametric study of the impact of column rectangularity (aspect ratio) on the punching shear behaviour of interior slab-column connections without shear reinforcement under static concentric vertical loading are provided. The study was conducted using a three-dimensional nonlinear FEM based on the concrete damaged plasticity model available in ABAQUS. The FEM, summarized herein, was calibrated using seven experimental specimens of slabs supported on square and rectangular columns from literature. The parameters studied were the column aspect ratio, and the ratio of the minimum column dimension to the effective slab depth. These parameters were selected based on a review of literature and design provisions. The impact of column rectangularity on the predicted load-deflection response, slab crack patterns and shear stress distribution in the slab along the column perimeter are analyzed. The results for the 77 slab-column connections simulated in the parametric study demonstrate that the impact of column rectangularity is not dependent on the column aspect ratio alone, and becomes more severe as the ratio of the minimum column dimension to the effective slab depth increases.

Punching shear behaviour of concrete slabs reinforced with CFRP grids

Punching shear action has been a focus for research in the field of civil engineering and using a fiber-reinforced polymer (FRP) grid is a novel configuration of the engineering materials. We present the test results of an experimental program on the punching shear performance of carbon-fiber-reinforced polymer (CFRP) grid reinforced concrete slabs. Six full-scale 1600 × 1600 × 150 mm slab specimens including one control steel reinforced concrete (RC) slab and five CFRP reinforced concrete slabs were fabricated and tested under monotonic loading till failure. The experiment aimed to investigate the effects of CFRP grids as flexural reinforcement and shear reinforcement on the punching behaviour of concrete slabs. Furthermore, three different shear reinforcement layouts were devised to verify which arrangement is better. Compared with the control RC specimen, the concrete slab with CFRP grids as flexural reinforcement reached almost the same punching strength with a lower reinforcement ratio. Moreover, adding extra shear CFRP grids was beneficial for improving the resistance of the concrete slab to punching. Among the three topological schemes of shear CFRP gird arrangements, the perpendicular layout was proven to be more effective than radial and rectangular arrangements.

Shear Behavior of Concrete Slabs Longitudinally Reinforced with High-Performance Steel

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address