Nonlinear numerical simulation of punching shear behavior of reinforced concrete flat slabs with shear-heads

Abstract

This paper examines the structural response of reinforced concrete flat slabs, provided with fullyembedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application.

Behaviour and design of hybrid RC beam-to-steel column connections

“…The numerical validation was carried out for specimens with varying geometry and constitutive parameters for 14 hybrid members, as described above [23,24], 12 reinforced concrete beams from an established test series [25,26], as well as 40 flat slab connections with or without shear-keys [27][28][29][30][31] In all cases, the results were assessed in terms of the stiffness, cracking force, ultimate strength, crack kinematics and overall failure modes. For brevity, only selected validations are presented in this paper, whilst the complete load-deformation curves and full details are described elsewhere [28].…”

Investigation of the punching shear behaviors of reinforced concrete slab–steel reinforced concrete L-shaped column connections

“…The CDP model accounts for a non- associated potential plastic flow, in which the plastic volume expansion is not proportional to the increase in stresses. This is represented in the plastic potential flow function by the dilation angle measured in the p-q plane at high confining pressure and surface eccentricity ( ε = 0.1) (Bompa and Elghazouli, 2020). In CDP , the material dilation angle ( φ ) is used to represent the stress increase at high confining pressures in the normal-shear stress plane.…”

Axial and bending behaviour of steel tubes infilled with rubberised concrete

“…Furthermore, the normal behaviour was defined as ''hard contact'' allowing for separation after contact, and the tangential behaviour was defined as the ''penalty'' algorithm with a friction coefficient. The friction coefficient was considered first within a range of 0.2-0.8 based on existing literature [38,39], then taken as 0.5 based on a sensitivity analysis. As the main objective is to obtain stiffnesses and strengths of various configurations, for the parametric investigations, the surfaceto-surface contact was replaced by a tie.…”

“…(2) for axial compression, the common definition of compression damage 𝑑 c = 1 − 𝑓 c ∕𝑓 cu is considered [38,39], having maximum values around 0.7-0.8 due to the residual strength; (3) for eccentric compression, to consider concrete crushing at the buckling region, a linear damage towards crushing strain (the compression damage factor 𝑑 c reaches values close to 1.0) is suggested. For case (3), the crushing strain is suggested considered as 𝜀 rc = (90 − 1.6f rc )𝜀 c0 for 𝑓 rc ≤ 30 MPa.…”