IBC 2021 / ACI 318-19 (LRFD): Punching shear check
Purpose of check
The punching shear check verifies whether the shear force acting on the column does not exceed the ultimate limit state of the foundation slab in the area of the critical perimeter. The check is performed at the critical perimeter at a distance of d/2 from the loaded area.
Punching shear capacity
The punching shear capacity is determined according to ACI 318 for slabs without shear reinforcement as the smallest value from three failure criteria (ACI 22.6.5.2):
|
λ |
Modification factor for lightweight concrete (= 1.0 for normal concrete) |
|
αs |
location factor (40 for interior column, 30 for edge column, 20 for corner column) |
|
d0 |
Length of the critical perimeter [in] |
The design resistance is φ · vc with φ = 0.75 (strength reduction factor for shear and torsion, ACI 21.2).
Punching shear demand
The existing punching shear stress consists of the basic stress component from the shear force at the critical perimeter and the stress components resulting from the moment transfer (unsymmetrical shear stress distribution):
|
Vu,res |
design shear force within the critical control perimeter (support force minus soil pressure component within the section) |
|
Msc,1, Msc,2 |
rechnerisches Plattenmoment in 1./2. Richtung |
|
e1, e2 |
Distance from the center of gravity of the punching shear perimeter to the point of the greatest stress |
|
J1, J2 |
Moment of inertia for bending of the critical perimeter |
Check / Utilization ratio
Software configuration
The material properties are adopted from the assigned concrete and reinforcement materials. The geometry of the critical perimeter (b₀, position with respect to edge/corner/interior column) is determined automatically from the foundation and column dimensions. The shear force and the moment components are determined from the governing load combinations.