How to Use the Lifting Lug and Weld Size Calculator
A lug used to lift a structure or piece of equipment with a crane must safely carry the lift load, which requires checking both net-section tension at the pin hole and shear at the weld attaching the lug to the base metal. This calculator applies a design load - the lift load times a design factor - to find the minimum lug thickness and the minimum fillet weld leg size needed.
Lug thickness is sized so the net section at the pin hole (lug width minus pin diameter) does not exceed the steel's yield strength. Weld leg size is based on the allowable shear stress of E70-series weld electrode (30% of its 70,000 psi tensile strength), sized so the fillet weld's effective throat (leg size x 0.707) times the weld length can carry the design load.
Lifting operations involve swing and shock beyond static loading, so a design factor of 3 to 5 times the rated load is typically applied. This calculator only covers net-section tension and weld shear - pin bearing stress and prying action are not included - so have a qualified structural engineer verify the final lug design.
Frequently Asked Questions
Lifting operations involve dynamic effects like swing and shock beyond static load, so members are designed for a design load equal to the rated load times a safety factor - commonly 3 to 5 times.
No. This calculator only considers net-section tension and fillet weld shear strength. Pin bearing stress, prying action, and eccentric loading are not included, so have the final design verified by a qualified engineer.