Understanding Side Loading and Point Loading on Rigging Components

Engineering guide to side loading and point loading on rigging hardware under ASME B30.26: hook tip-loading risks, shackle side-load derating (up to 50%), and centering protocols.

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Rigging accessories—including shackles, hooks, master links, and eyebolts—are designed and proof-tested to absorb tensile forces applied in specific, engineered directions. For most hardware, this primary design direction is in pure tension along the component's major longitudinal centerline. When unapproved forces are introduced—specifically **Side Loading** (forces applied out of plane or across the body) and **Point Loading** (concentrated force applied on a narrow tip rather than the broad bearing seat)—the component's mechanical strength collapses catastrophically. In fast-paced port and shipyard environments across Central Africa, side loading and point loading are leading causes of sudden hardware failure. Rigging teams must understand the physical mechanisms behind these loading errors and enforce strict positioning discipline during every lift. ## The Mechanics of Side Loading Side loading occurs when tensile force is applied at an angle to the major axis of a component: - **Shackles:** If a shackle is pulled out of plane (across its jaws), the pin experiences severe bending moments rather than pure double-shear tension. Under **ASME B30.26**, side loading on bow shackles requires severe capacity derating: - 0° to 5° in-line: 100% WLL. - 6° to 45° off-axis: **30% reduction** (70% WLL retained). - 46° to 90° off-axis: **50% reduction** (50% WLL retained). - Loading beyond 90°: **Strictly prohibited**. - **Dee shackles must NEVER be side-loaded at any angl...