ISO 8686-3:2018

Overview

ISO 8686-3:2018 - "Cranes - Design principles for loads and load combinations - Part 3: Tower cranes" specifies how to apply the general rules of ISO 8686-1 to tower cranes used for construction work (as defined in ISO 4306-3). It provides specific requirements and values for loads, dynamic factors and load combinations used in structural calculations, including rules for in-service and out-of-service wind, erection/dismantling, climbing systems and mobile self-erecting tower cranes. The standard assumes tower cranes fitted with a hook as the load‑handling device; alternative uses may require different values.

Key topics and requirements

• Scope of application: Adapts ISO 8686-1 for tower cranes and integrates tower‑crane specific rules (rigid body stability, wind in out-of-service state, climbing systems).
• Loads and classifications: Defines regular (A), occasional (B) and exceptional (C) load categories for design and verification.
• Dynamic factors (ϕi): Guidance values for dynamic coefficients applied to hoisting, drive forces, inertial effects, and test loads. Example values from the standard:
  • a = 0.05 for tower crane structural considerations.
  • Hoisting unrestrained grounded load: for load combinations A1 and B1, ϕ2,max = 1.3.
  • Hoist drive classes: only HD1 or HD4 are allowed for tower cranes.
• Wind loading:
  • Minimum in‑service wind pressure: q = 250 Pa (v = 20 m/s); for special load charts q = 125 Pa (v = 14.1 m/s).
  • Test wind pressure minimum: q = 40 Pa (v = 8 m/s).
  • Detailed treatment of out‑of‑service wind including empirical load cases to cover delayed slewing and turbulent sites.
• Proofs and checks: Prescribes proof of strength, proof of stability (including rigid body stability), fatigue checks and load combinations for structural and support‑structure design.
• Special cases: Loads during erection, dismantling, transport, access means, buffer forces, and hoist rope rupture or accidental load drop (use of ϕ = −0.3 for some stability/strength checks or dynamic analysis).

Applications and users

ISO 8686-3:2018 is intended for:

• Tower crane manufacturers for design and load chart development.
• Structural and mechanical engineers performing strength, stability and fatigue calculations.
• Test laboratories and certification bodies conducting proof tests per ISO 4310.
• Construction site managers, clients and safety engineers ensuring safe crane selection, siting and operational limits. Practical uses include structural calculation inputs, design verification, preparation of operating instructions and conformance to regulatory requirements.

Related standards

• ISO 8686-1:2012 (general design principles for loads)
• ISO 4302 (wind load assessment)
• ISO 4306-3 (tower crane vocabulary)
• ISO 4310 (test code and procedures)
• ISO 20332 (proof of competence of steel structures)
• ISO 12488-1 (tolerances for wheels and tracks)

Keywords: ISO 8686-3:2018, tower cranes, loads, load combinations, dynamic factors, structural calculation, out-of-service wind, proof of strength, proof of stability.