November 26 (Report) Recently, the international standard ISO 16521:2024,Design of concrete-filled steel tubular (CFST) hybrid structures, led by China and completed under the chairmanship of Han Linhai, Tenured Professor of Tsinghua University and President of Guangxi University, was officially released and put into implementation. This standard is the first standard issued by the International Organization for Standardization (ISO) in the field of concrete-filled steel tubular structures since its establishment, filling the gap in ISO international standards in this field and creating conditions for the scientific promotion and application of such structures worldwide. It is reported that the standard has been adopted by countries such as the United Kingdom and Denmark as their national standard.

Cover of the international standard ISO 16521:2024

A concrete-filled steel tubular (CFST) hybrid structure is a structure that uses CFST (formed by filling a steel tube with concrete) as its main component and is hybridized and works together with other structural members (parts). It offers advantages such as high load-bearing capacity, high stiffness, good ductility, strong seismic, fire and impact resistance, and economic and low-carbon performance, and is becoming one of the preferred forms for the main structures of major civil engineering projects in fields such as construction, transportation and energy. The international standard ISO 16521:2024 comprises 16 chapters and 2 annexes, and systematically specifies the scope of application, terms, symbols, materials, design and construction processes, general provisions, specific provisions, actions (loads), analysis, ultimate limit states, serviceability limit states, protective design, joint and connection design, and construction and acceptance of CFST hybrid structures.

Table of contents of the international standard ISO 16521:2024

Professor Han Linhai, the chair of the international standard ISO 16521:2024, has devoted himself to research on CFST structures for more than 30 years. He established the full-life-cycle safety analysis theory and design technology for such structures, innovatively developed high-performance CFST hybrid structural forms, and expanded the safe and applicable scope of the main structural systems of large and complex civil engineering projects. His research results have been widely promoted and applied, with significant social and technical-economic benefits. His research results, including the concept of the confinement effect coefficient of CFST, the constitutive models of concrete inside steel tubes under static and dynamic loads, the load-bearing capacity calculation methods for CFST truss-type and stiffened hybrid structures, and key detailing measures for CFST structures, have been systematically incorporated into this standard.

Han Linhai

On the basis of the successful development of the international standard ISO 16521:2024, the ISO Technical Management Board, ISO's highest technical management body, through its 2024 Decision No. 45, officially approved the establishment of the Subcommittee on Composite and Hybrid Steel-Concrete Structures (ISO/TC 71/SC 9) under the organization's Technical Committee on Concrete, Reinforced Concrete and Prestressed Concrete (ISO/TC 71). This is the first subcommittee established by ISO in the field of composite and hybrid steel-concrete structures, with Professor Han Linhai serving as its first chair. ISO Secretary-General Sergio Mujica recently visited the secretariat of ISO/TC 71/SC 9 and fully affirmed the international standard ISO 16521:2024 and the work of the subcommittee, noting that ISO 16521:2024 is of great significance for ensuring the scientific promotion and application of CFST structures worldwide. He also expressed the hope that ISO/TC 71/SC 9 will continue to pool the strength of global experts, play an active role in the formulation of international standards in this field, and contribute to global civil engineering infrastructure construction.

With ISO 16521:2024 as the core standard, Professor Han Linhai further proposed a proposal to establish a "technical standard system for CFST structures." The proposal has been reviewed and approved at the plenary meeting of ISO/TC 71/SC 9 and formed Decision No. 8, which is of important guiding significance for promoting the construction of the ISO technical standard system for CFST structures.