Abstract
This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded 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.
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Abbreviations
- A vv :
-
shear-head shear active area
- a :
-
distance between parallel steel profiles
- b 0 :
-
control perimeter
- b c :
-
column size
- b v :
-
shear-head width
- cc, ck :
-
location of neutral axis
- CBX:
-
closed box shear-head
- CRH:
-
cruciform shear-head made of I sections or back-to-back welded channels
- CTP:
-
cruciform shear-head with two-way two pair of channels running at the column
- support d :
-
bending effective depth
- d 0 :
-
shear effective depth
- dg0, dg :
-
aggregate size
- d vfb :
-
centroid of bottom flange
- E c :
-
elastic concrete modulus
- Es, Ev :
-
steel elastic modulus
- f c :
-
concrete strength
- f ct :
-
tensile strength of concrete
- f ys :
-
reinforcement yield strength
- f yv :
-
shear-head yield strength
- h :
-
flat slab thickness
- h v :
-
shear-head depth
- k ψ :
-
factor for failure criterion
- K c :
-
factor for the shape of the deviatoric plane
- L :
-
specimen size/span
- l m :
-
mesh size
- l v :
-
shear-head embedded length
- M vi :
-
moment carried by one shear-head
- M v,i, R :
-
moment capacity of one shear-head
- m i :
-
moment action per unit width
- m Rk :
-
plastic moment of hybrid sectors
- m Rc :
-
plastic moment of concrete sectors
- n v :
-
number of shear-heads
- rc = 2bc/π and bc = (bc1 + bc2)/2:
-
(for rectangular columns)
- r e :
-
exterior slab radius
- r s :
-
slab radius (loading radius)
- t f :
-
shear-head flange thickness
- t w :
-
shear-head web thickness
- V :
-
load
- V e :
-
volume of the mesh element
- V flex :
-
is the flexural strength
- V i :
-
is the shear action
- V test :
-
test ultimate strength
- V num :
-
numerical ultimate strength
- V u :
-
ultimate punching shear strength
- W v,pl :
-
shear-head plastic section modulus
- δ :
-
displacement response
- ε :
-
strain
- ε c1 :
-
crushing strain
- η :
-
shear-head distribution factor
- κ :
-
force distribution factor
- λ y :
-
rotation coefficient
- λ m :
-
flexibility factor
- μ :
-
steel-concrete friction coefficient
- ρ l :
-
flexural reinforcement ratio
- σ :
-
stress
- σ c,max :
-
strut crushing strength
- θ :
-
punching shear crack angle
- φ :
-
dilation angle
- ψ :
-
rotation
- ε :
-
potential eccentricity
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Bompa, D.V., Elghazouli, A.Y. Nonlinear numerical simulation of punching shear behavior of reinforced concrete flat slabs with shear-heads. Front. Struct. Civ. Eng. 14, 331–356 (2020). https://doi.org/10.1007/s11709-019-0596-5
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DOI: https://doi.org/10.1007/s11709-019-0596-5