Hyundai Engineering said on the 12th that it has won technical certification from the Korean Society of Steel Construction for a steel modular joint structural system co-developed with Hyundai Steel (004020).
The certified technology covers the joint structure used when box-type module units manufactured in factories are stacked and assembled on site. Hyundai Engineering said the system simultaneously secures structural safety, considered the biggest challenge in high-rise modular construction, and improves on-site constructability.
Under seismic design standards for steel structures revised in May 2024, newly developed steel joint technologies must be verified by the Korean Society of Steel Construction, designated by the Ministry of Land, Infrastructure and Transport, before they can be applied to actual projects. Hyundai Engineering passed cyclic loading tests using two or more identical specimens, as well as a technical review.
Existing modular buildings of medium height or taller have mainly used built-up rectangular steel tube members, fabricated by cutting and welding steel plates to support loads. The fabrication process is complex, which can raise costs, and quality and dimensional precision can vary by manufacturer. Material procurement was also a disadvantage.
Hyundai Engineering addressed those issues by adopting standardized, off-the-shelf H-beams as the primary structural members. Using standardized materials cut costs and improved the stability of material supply, and the open cross-section of H-beams secured uniform section quality, the company said. Fireproof coating is also easier to apply, allowing the system to meet a range of fire-resistance requirements.
Two technologies were applied to improve constructability. A two-way alignment guide system directs modules into the correct position as they are lifted and installed by crane. Guides mounted on the modules absorb errors within a set range in both horizontal directions, helping each module settle into its proper place.
The company also adopted a horizontal bolting method. Previously, bolts had to be fastened vertically in cramped spaces inside ceilings or columns, making it difficult to secure working space and causing frequent interference with other structural elements. The new method is designed so that workers fasten bolts from the front, securing working space and making power tools easier to use. The company said this improves worker safety and cuts on-site assembly time by more than 20%.
Structural safety verification was conducted with researchers from the Korean Society of Steel Construction. In cyclic loading tests on a full-scale two-story frame, the technology maintained performance without structural damage or strength degradation at a story drift of 4%, double the 2% maximum required under the current Korean Design Standard. Simplifying the structure so that building loads transfer directly to the columns also reduced force concentration in specific areas and leaning to one side.
The technology has been applied at H-Modular Lab, a full-scale modular test facility that Hyundai Engineering and Hyundai Steel built together in November 2024, where stacked construction was verified.
Hyundai Engineering plans to expand the use of off-site construction technology in data centers and industrial buildings on the back of the certification. "The competitiveness of modular construction depends not only on the precision of factory production but also on how quickly and safely modules can be assembled on site," an official at Hyundai Engineering said. "This H-beam steel modular joint structural system secures construction tolerance absorption, worker safety and seismic structural performance all at once."