Schalkstad parking garage gets ingenious steel structure: Smart, slender and extremely strong

This also applies to the new, above-ground parking garage of the Schalkstad residential and shopping area in Haarlem, the Netherlands, for which Vic Obdam Staalbouw, in collaboration with Tullingh & Partners and commissioned by BAM Wonen Speciale Projecten, is realizing a complete steel structure including steel deck concrete floors.

With its steel structures, Vic Obdam Steel Construction lays the foundation for many a project. "We offer a broad but specialized total package, from 3D measuring/inscanning to total engineering, production, preservation and assembly of the steel structure. From residential construction to utilities and from new construction to renovation and transformation," says project manager Bart van der Gulik. "We are also strong in alternative building assignments, such as inserting and topping buildings and freely divisible and adaptable building volumes. As an organization, we are often awarded the complete steel structure, including stairs and railings, roof and wall cladding and floors, for which we work with trusted partners. For the engineering and execution of the steel plate-concrete floors, that is Tullingh & Partners, which often also engages Vic Obdam Staalbouw for its steel construction projects."

Tullingh & Partners specializes in the structural engineering, material supply and realization of metal roof and façade systems and steel sheet-concrete floors. "A nice interaction between our companies has developed in recent years," said Charles van Oldenbarneveld of Tullingh & Partners. "The transformation of the former office building at Willem Witsenplein in The Hague, the expansion of Flower Auction Royal Flora Holland in Aalsmeer, the expansion of a chemical plant at Westpoort business park in Amsterdam and the new construction of Parkeergarage Schalkstad are telling examples."

"We really pull together on projects," he stresses. "Using the aesthetic and/or structural design as a foundation, we invariably work out our own plan. What are the possibilities to build lighter, with fewer materials, so that the environment is relieved?" Van der Gulik: "For Schalkstad parking garage, too, we mapped out the construction and possible optimizations at an early stage. Initially, an alternative floor was engineered, from a different manufacturer and with a different profile. However, Tullingh & Partners came up with the option for a slender type of steel plate-concrete floor, creating more free height between floors. In addition, the floors are stronger than the prescribed standard. Our joint calculations convinced both principal structural engineer Pieters Bouwtechniek and contractor BAM Wonen Speciale Projecten. They also led to a specification amendment, which was approved by the municipality of Haarlem. At the end of 2018, we were awarded the production, delivery and assembly of the complete structure, except for the reinforcement and concrete."

The above-ground parking garage will accommodate 600 passenger cars. The building has five floors, with the top four being constructed of steel. "In total, we are handling 500,000 kilograms of steel," said Van der Gulik. "The structure consists of steel columns and beams with a span of 16 meters. Big challenge was the high fire resistance.   

If an unexpected fire breaks out, the entire steel structure must remain standing for 60 minutes. We achieved this in part by reinforcing and concreting the columns. In addition, the steel beams were given a special, fire-resistant coating."

Initially, the beams were to be attached to the columns, he says. "However, this could cause major problems if the column steel failed. Therefore, together with Pieters Bouwtechniek, we came up with an alternative solution. In the current design, the beams are integrated into the concrete, right through the steel column. However, this brought new challenges. For example, for Tullingh & Partners, which could no longer make connections at these places. For this, too, we worked out a good alternative together."

"In total, we are installing as much as 15,000 m² of steel plate-concrete floor," says Van Oldenbarneveld. "During assembly, we follow the progress of the steel construction. As soon as the construction of one floor is complete, our steel plates are applied. Quite a challenge, because we are dealing with as many as 11 meters long plates that are hoisted in 15 pieces! Precise planning and coordination are necessary then." Thanks to an overlapping assembly method, work can be done very quickly and efficiently, he emphasizes. "The steel plate concrete floors are assembled in just one week. Then we also have one week for finishing, after which the contractor can apply his concrete and Vic Obdam Staalbouw starts the next floor." 

Compared to traditional floor systems, steel deck concrete floors require significantly less concrete, Van Oldenbarneveld said. "This leads to large weight savings for comparable spans and loads. In addition, the floors are significantly thinner. Whereas the basic design for Schalkstad Parking Garage was a floor 16 cm thick, we were able to reduce that to just 13 cm, with the same span. The load capacity has also been increased from 2.0 kN/m² to 3.0 kN/m². This makes the parking garage excellently prepared for the future, in which the proportion of (heavier) electric cars will continue to increase."

The steel sheet-concrete floors are mounted on 16-meter-long steel beams, which are connected to the floors using steel welding dowels (pins). "Over 3,500 weld studs per floor are required for this attachment (total: 14,000 pieces). The result is an excellent cooperation between the steel structure and steel plate-concrete floor."

Thanks to good construction team cooperation and short lines, Vic Obdam Staalbouw and Tullingh & Partners are able to deliver one complete floor every four weeks. In week 4, the assembly of the last floor of the steel structure started. The structure will be finished all around with steel frames with approximately 4,000 wooden slats, which will also be supplied and assembled by Vic Obdam Staalbouw. By the summer vacations of 2021, the project should be completed.