Fail-Safe Bolted Joint Design

Sole Analyst — MECH3110 Individual Assignment

A structural design brief for a public swing installation in Christchurch, one of New Zealand's most seismically active regions. The requirement was fail-safe: if Joint C collapses entirely, Joint B must still hold. That left a 3.5 m cantilever carrying full dynamic swing loads from three simultaneous users with no redundancy.

• Modelled worst-case loading as three 100 kg adults swinging at 12 km/h simultaneously, giving 7,852 N vertical reaction and 14,134 N·m bending moment at the joint
• Chose 250UC73 Universal Column over standard UB for superior torsion resistance from its square 254 × 254 mm profile
• Applied non-uniform moment distribution rather than equal-split assumption; the outermost bolts carry 19.17 kN tensile and 9.65 kN shear each
• All three failure modes cleared (FOS 3.95 yield, 13.81 separation); caught geometric edge distance at 1.44 and recommended moving from 65 mm to 72 mm