When verifying static equilibrium, the check determines whether the foundation remains stable in its position under the acting actions and whether failure due to lateral-torsional buckling occurs.
According to EN 1997-1 [1] 2.4.7.2, the verification is carried out by comparing stabilizing and destabilizing moments at the foundation edges.
EN 1997-1: Static equilibrium
Determination of actions
For the verification, the destabilizing moments at the foundation edges are determined. These result in particular from horizontal forces and from eccentrically acting vertical loads.
Determination of resistances
The destabilizing moments are opposed by stabilizing moments, which essentially result from the vertical loads and the self-weight of the foundation and the overlying soil.
Verification
The verification is carried out separately for each relevant foundation edge. The ratio of the destabilizing moment to the stabilizing moment is determined:
The governing value is the maximum of all considered directions.
IBC 2021 / ACI 318-19 (ASD): Lateral-torsional buckling
Purpose of verification
The lateral-torsional buckling check verifies whether the destabilizing moments caused by horizontal loads do not exceed the stabilizing moments from the vertical load on the foundation.
Moment equilibrium
The verification is carried out about the foundation edge in the direction of lateral-torsional buckling:
Stabilizing moment
The stabilizing moment results from the vertical load on the foundation and its lever arm to the considered buckling edge:
|
P |
gesamte vertikale last auf das fundament [kip] |
|
z |
lever arm of the resulting vertical load to the tilting edge [ft] |
Lateral-torsional buckling moment
|
H |
horizontal force acting on the foundation [kip] |
|
a |
lever arm of the horizontal force to the tilting edge [ft] |
Utilization ratio
The required safety factor Φoverturning,lim can be defined in the Geotechnical Design configuration.
Software configuration
The required safety factor Φoverturning,lim is defined in the Geotechnical Design configuration. All loads acting on the foundation are taken from the defined load cases.