ISO 16521:2024

Overview

ISO 16521:2024 - Design of concrete-filled steel tubular (CFST) hybrid structures provides authoritative guidelines for the design, construction and inspection of CFST hybrid structures. The standard applies where CFST members are used as main structural components - such as columns, girders, piers or arches - particularly in high‑rise buildings, long‑span spatial structures, and large‑scale bridges. CFST chords may be circular, square or rectangular sections.

Key topics and technical requirements

The standard is organized to support full life‑cycle delivery of CFST hybrid structures. Major technical topics include:

• Materials (Clause 5): requirements and specifications for concrete, steel tubes, reinforcement, welding consumables, fasteners and protective coatings; storage of materials.
• Design and construction procedure (Clause 6): overall workflow from concept through inspection.
• Limit states and design formats (Clauses 7–8): ultimate and serviceability limit state frameworks, design working life, and selection of construction methods.
• Actions (Loads) (Clause 9): treatment of dead, live, snow, wind, seismic, thermal and other actions; load combinations and partial factors.
• Analysis (Clause 10): structural analysis objectives, methods, construction‑stage analysis, and material stress–strain relationships for concrete and steel.
• Ultimate limit states (Clauses 11–12): detailed resistance models for trussed and concrete‑encased CFST hybrids - axial compression, bending, combined compression/bending, shear, slenderness and long‑term effects.
• Serviceability (Clause 13): calculation of deflections, cracking, and other serviceability criteria.
• Inspection and construction detailing: welding, reinforcement detailing, and inspection guidance are integrated through the document.

Practical applications and users

ISO 16521:2024 is intended for professionals involved in the planning, design, fabrication, erection and inspection of CFST hybrid structures, including:

• Structural and bridge engineers
• Design offices and architects specifying composite/hybrid systems
• Fabricators, contractors and erectors of tubular steel and concrete elements
• Inspection bodies, certification agencies and code authorities
• Researchers and manufacturers developing CFST products and connection details

Practically, the standard supports safe, consistent design and construction practices for CFST systems used in buildings and bridges where hybrid tubular members are preferred.

Related references and implementation

The standard includes normative references (Clause 2) and defined terms/symbols (Clauses 3–4) to ensure consistent application. For project‑level use, consult ISO 16521:2024 alongside national building codes and local seismic/bridge design regulations.

Keywords: ISO 16521:2024, CFST, concrete‑filled steel tubular, hybrid structures, design guidelines, seismic design, ultimate limit state, serviceability, structural analysis, bridge design.