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 inner column, 30 for edge column, 20 for corner column) |
|
d0 |
Length of the perimeter section [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 |
Governing shear force within the basic control perimeter (support force minus the soil pressure component within the perimeter section) |
|
Msc,1, Msc,2 |
Calculated plate moment in the 1st/2nd direction |
|
e1, e2 |
Distance from the center of mass of the perimeter section to the point of maximum stress |
|
J1, J2 |
Moment of inertia for bending of the basic control 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.