- An Interpretation of the International Approach in the Standard for Design of Steel Structures with Yield Strengths from 690 MPa to 960 MPa
As China's steel structure industry moves toward higher performance and lighter weight solutions, the demand for high-strength steel has grown significantly. In July 2026, the China Steel Construction Society officially released the group standard Standard for Design of Steel Structures with Yield Strengths from 690 MPa to 960 MPa (hereinafter referred to as "the Group Standard"), filling a domestic gap in unified design provisions for this strength range. Notably, the new standard explicitly references the design philosophy and presentation format of the European Standards (EN 1993-1 and EN 1994-1), aiming to build a bridge between Chinese standards and internationally accepted practices.
Why Benchmark Against Eurocode?
The Group Standard was developed by a team led by The Hong Kong Polytechnic University, Tsinghua University, and other institutions, incorporating the latest research findings, design methods, and construction experience in the field of high-strength steel. The drafting committee identified early on that the Eurocode has established a relatively mature framework for designing high-strength steel members and connections, whereas China previously had no unified provisions for steel grades above Q690.
"By adopting the design philosophy and presentation format of the Eurocode, it becomes easier for Chinese engineers to familiarise themselves with international practices and to communicate with their overseas counterparts. At the same time, it helps foreign engineers understand Chinese standards more readily," said a representative of the standard drafting committee. This reflects the core objective of the Group Standard: to promote interoperability and mutual recognition between Chinese and international standards.
Where Does the Standard Reference the Eurocode?
The influence of the Eurocode is evident in several key technical aspects:
Cross-section Classification – The Group Standard directly adopts the cross-section classification system from Eurocode 3, categorising section plate slenderness into Class 1, Class 2, and Class 3, and explicitly states that Class 4 cross-sections are not permitted for high-strength steel members. This differs from the traditional GB 50017 approach, which classifies sections into five grades from S1 to S5.
Plastic Design for Full Cross-sections – For the strength and stability calculations of members under bending, combined bending and axial tension, and combined bending and compression, the Group Standard introduces the plastic design method from the Eurocode. It rationally accounts for the effects of local buckling or plastic development on load-bearing capacity and ductility based on cross-section type and section modulus, offering a more economical solution for engineering applications.
Composite Structure Design – For steel-concrete composite beams and composite columns, the standard references the relevant methods from EN 1994-1-1 and the UK SCI design guide P142, systematically deriving calculation formulas for the flexural and shear capacities of composite beams with partial and full shear connection.
Connection Design – The standard adopts the Eurocode design methods for welded K‑joints, T‑joints, X‑joints in circular and rectangular hollow sections, while calibrating the reduction factors for high-strength steel connections based on experimental data to ensure that the resulting capacity formulas remain generally conservative.
The Deeper Significance of International Alignment
The international orientation of the Group Standard is a microcosm of China's broader strategy to "export" its engineering standards. In recent years, as infrastructure connectivity under the Belt and Road Initiative has accelerated, Chinese enterprises engaged in overseas EPC (engineering, procurement, and construction) projects have faced a major challenge: standard barriers. Issues such as the limited international recognition of Chinese standards, the lack of comprehensive English versions, and discrepancies between domestic design practices and host-country requirements have all constrained the global reach of Chinese technology and products.
By proactively aligning with the Eurocode, the Group Standard lowers the threshold for applying Chinese standards in overseas projects. Professor K.F. Chung, the lead drafter of the standard from The Hong Kong Polytechnic University, noted that public works in Hong Kong are designed, constructed, and inspected strictly in accordance with Eurocode requirements. This mature standards system, already aligned with international norms, provides a natural interface for promoting Chinese high-strength steel products globally. An English version of the Group Standard is currently being compiled and will be published as soon as possible.
From Pilot Projects to Systematic Standards
From the Hong Kong Tseung Kwan O Cross Bay Bridge, which used 690 MPa high-strength steel in 2022, to the world's first pedestrian bridge using 960 MPa high-strength steel at Lung Yeuk Tau in Hong Kong, and now to the release of a group standard covering the entire 690–960 MPa range, China's application of high-strength steel has evolved from isolated pilot projects to systematic standardisation.
The Tseung Kwan O Cross Bay Bridge used domestically produced S690QL high-strength steel for its steel arches, reducing steel consumption from approximately 8,800 tonnes under a conventional design to 4,400 tonnes - a saving of about half - and cutting project costs by approximately HK$100 million for the Hong Kong SAR government. The S960 footbridge at Lung Yeuk Tau reduced its total structural self‑weight from 6,500 tonnes (in a traditional reinforced concrete solution) to just over 600 tonnes, a reduction of 90%. These real‑world projects not only demonstrate the economic benefits of high‑strength steel but also provided solid engineering data that informed the drafting of the new standard.
That said, challenges remain for the large‑scale application of high‑strength steel. Professor Chung pointed out that fatigue performance after welding is a key area for further research, particularly for demanding service conditions such as vehicle bridges and railway bridges, where systematic fatigue testing is needed.