Founded in 1964, Teräselementti Oy is a Finnish family business specializing in hall construction, steel building frames and facade solutions for commercial buildings. The company supplies its products primarily on a turnkey basis, including product design, manufacture and installation services. Projects are realized either as design-build projects or according to client plans. Additionally, some of its facade products are also supplied without the service package.

The challenge:

Maximum column-free space at minimum cost
Located in the Finnish capital of Helsinki, the exhibition and convention center is the largest of its kind in the country, welcoming over a million visitors annually. A new hall, Exhibition Hall 7, was envisioned to be a multi-purpose hall with maximum column-free space.

With a surface area of 14,700 m² (nearly 158, 235 ft²), the sheer size and weight of the trusses posed challenges for producing suitable elements for the hall’s steel frame. In addition, the frame had to be as economical as possible.

The solution

Best results with double-grade steel

The project called for a steel grade that would allow constructing a 78-meter, column-free area. The steel frame consists of 17 individual 78-meter space trusses with a maximum height of 7 meters and maximum width of 3.5 meters, each weighing between 65 to 80 tonnes. Each truss consisted of two 39-meter segments. Teräselementti Oy, contracted for constructing the frame, used double-grade S420MH / S355J2H hollow sections as the material for the steel frame’s space trusses. The light, high-strength double grade combines the best properties of both S420MH and S355J2H grades.

Construction of the steel frame for Exhibition Hall 7 began in June 2010, and the expansion project was successfully completed in August 2011.

A lighter construction

SSAB’s double-grade structural hollow sections can be used to build structures that are more than 15 percent lighter. During the expansion project, the structural properties of the S420 steel meant that uniform sections could be used even in places subject to greater loads. Sections with identical external radii could be used. And approximately 100 tonnes less steel was needed than if S355 steel had been used. With S420, only about 1,700 tonnes of steel was used for the expansion.

An affordable solution

Using double-grade steel in steel structures substantially lowers material costs, providing a financially attractive option. It also reduces the environmental effects of the material use and production. Also, using double-grade hollow sections decreases storage costs. “Double grade’s benefits for the builder were clear during the expansion project: It resulted in a lighter, more economical solution,” says Markku Laine, head of steel construction operations at Teräselementti Oy.

The steel tubes were delivered cut to length directly from the factory to the client, allowing them to cut down on additional welding costs.

Seamless collaboration

Teräselementti and Ruukki (now part of SSAB) cooperated seamlessly during the Exhibition & Convention Centre expansion project. Roughly 70–75% of the material requirements were known right from the project’s start, allowing Teräselementti to instantly reserve the required production volume.
Even when the builder made substantial changes to the plans during the final phase of the project, necessitating extra material, Teräselementti got the last-minute material and kept the project right on schedule.