S960 steel is a high-strength material known for its impressive load-bearing capacity and durability, making it an excellent choice for demanding construction projects. Compared to commonly used S355 steel, S960 is both lighter and stronger, offering significant advantages for large infrastructure projects such as bridges and high-rise buildings. However, the challenge with S960 steel lies in the welding process. When welded, the material can suffer a loss in mechanical properties, including a reduction in strength and ductility by as much as 20% to 30%. This issue has traditionally limited its widespread use in construction, particularly in projects requiring welded connections.
Addressing this critical issue, a research team from the Department of Civil and Environmental Engineering at The Hong Kong Polytechnic University has developed an innovative welding technology that maintains the steel's mechanical properties during the welding process. Led by Professor Kwok-fai Chung, the team conducted a series of experimental investigations and numerical simulations to understand how heat input affects S960 steel. By precisely controlling the heat energy during welding, they discovered optimal ranges for different weld joint designs and steel thicknesses, allowing the material’s strength and ductility to be preserved.
This breakthrough has already been applied in a major public infrastructure project in Hong Kong: the construction of a footbridge in the Fanling North New Development Area. This footbridge, which is part of the first phase of the Fanling Bypass Eastern Section, marks the first public works project in Hong Kong to use this advanced welding technique for S960 steel. The bridge features two segments made from stiffened box girders fabricated from S960 steel. These segments were welded with the new technology in a controlled factory environment, ensuring that the mechanical properties of the steel were not compromised.
The use of S960 steel in the footbridge has numerous benefits. The material’s superior strength allows for the use of thinner steel components, which reduces the overall weight of the structure. This, in turn, minimizes the need for a large number of foundation piles, which are typically required to support heavier structures. Fewer piles mean reduced construction costs and less disruption to the surrounding environment. Furthermore, the reduction in steel usage and the more efficient design lead to a significant decrease in carbon emissions, making the project more sustainable.
This innovative welding technology also holds great promise for the future of steel construction, particularly in large, long-span structures where weight and material efficiency are crucial. Professor Chung emphasized the importance of this research in providing engineers with the knowledge and tools needed to incorporate high-strength steels like S960 and S690 into their designs. The technology not only sets a new standard for modern steel construction but also offers valuable insights for creating technical guidelines and specifications for the broader adoption of these materials in the construction industry.
The impact of this research is already being felt in other notable infrastructure projects in Hong Kong. The welding technology developed by Professor Chung's team has been implemented in several key projects, including the Double Arch Steel Bridge of the Cross Bay Link, the long-span roof structures of the Kowloon Tsai Swimming Pool, and the steel roofs of the East and West Stands at the Yuen Long Stadium. These applications demonstrate the versatility and potential of S960 steel in various types of large-scale, high-performance construction.
As the global demand for sustainable and efficient infrastructure continues to grow, innovations like this welding technology will play a crucial role in shaping the future of construction. By optimizing the use of high-strength materials like S960 steel, engineers can create lighter, stronger, and more cost-effective structures that meet the demands of modern urban development. The successful implementation of this technology in Hong Kong’s infrastructure projects is just the beginning of what could be a global trend in steel construction, helping to push the boundaries of what’s possible in engineering and architecture.
