# Punching Shear Design

What is punching Shear?

Punching shear arises when a concentrated load is applied to a small area of a slab or, most commonly, the reaction of a column against a slab. The resulting stresses are verified along defined control perimeters around the loaded area.

• Punching Shear is checked automatically in accordance with Codes.

International Design Codes

ACI 318-19 : Punching Shear Design per ACI 318-19 with ideCAD

Notation in ACI 318-19

Ag = gross area of the concrete section, in2
As = area of non-prestressed longitudinal tension reinforcement, in2
bo = perimeter of critical section for two-way shear in slabs and footings.
bslab = effective slab width, in.
b1 = dimension of the critical section bo measured in the direction of the span for which moments are determined.
b2 = dimension of the critical section bo measured in the direction perpendicular to b1, in.
d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.
Ec = modulus of elasticity of concrete, psi
Es = modulus of elasticity of reinforcement, psi
√fc = square root of specified compressive strength of concrete, psi
fc' = specified compressive strength of concrete, psi
fy = specified yield strength for non-prestressed reinforcement, psi
Jc = property of assumed critical section analogous to the polar moment of inertia
Msc = factored slab moment that is resisted by the column at a joint, in.-lb
vc = stress corresponding to nominal two-way shear strength provided by concrete, psi
vuv = factored shear stress on the slab critical section for two-way action, from the controlling load combination, without moment transfer, psi
αs = constant used to calculate Vc in slabs and footings
ϕ = strength reduction factor
λ = modification factor to reflect the reduced mechanical properties of lightweight concrete relative to normalweight concrete of the same compressive strength
λs = factor used to modify shear strength based on the effects of member depth, commonly referred to as the size effect factor
εt = net tensile strain in an extreme layer of longitudinal tension reinforcement at nominal strength, excluding strains due to effective prestress, creep, shrinkage, and temperature
εty = value of net tensile strain in the extreme layer of longitudinal tension reinforcement used to define a compression-controlled section
γf = factor used to determine the fraction of Msc transferred by slab flexure at slab-column connections
γv = factor used to determine the fraction of Msc transferred by the eccentricity of shear at slab-column connections