Under EN 14439 and DIN 15018 / FEM 1.001, a free-standing tower crane gravity foundation must achieve an overturning factor of safety (FS = Mrestoring / Moverturning) of at least 1.50 under in-service operating conditions (rated hook load plus maximum operating wind speed), and at least 1.30 under extreme out-of-service hurricane storm wind conditions with the slewing brake released for free weathervaning.

When load eccentricity is within the foundation kern (e ≤ B/6), the entire bottom of the concrete pad remains compressed against the soil in a trapezoidal stress distribution. When e > B/6, the windward heel of the footing lifts off the soil (heel uplift), creating a triangular compression block over an effective contact length B' = 3(B/2 - e) where soil tension is zero.

Weathervaning allows the crane's jib to freely rotate 360° like a weather vane, aligning parallel to incoming gale winds to minimize aerodynamic drag. If the slew brake is locked, hurricane winds striking the broadside of the jib increase horizontal base shear and overturning moment by up to 300% to 450%, causing instantaneous foundation toppling.

Concrete has a dry unit weight of ~24 kN/m³ (150 lb/ft³). When groundwater rises and submerges the foundation pad, buoyant upward pressure strips away the unit weight of water (9.81 kN/m³), reducing the effective stabilizing weight of the concrete by ~41% (to ~14.19 kN/m³). Overlooking high water tables is one of the most common causes of crane foundation failures.

Wind can strike from any azimuth. When extreme wind acts along the 45° diagonal axis of a square pad, the resisting moment arm to the toe decreases by a factor of 1/√2 (~29% reduction in stabilizing lever arm), while corner soil pressure spikes because the resisting footprint narrows to a point. Foundations safe orthogonally can fail when checked diagonally.