Reinforcement solutions for bulb floors

Various reinforcement solutions have since been devised following the collapse of the Eindhoven parking garage. The safety of many concrete floors in the Netherlands has since been called into question. Research into solutions to reinforce such floors is in its final stages.

As a supplier of construction tools and materials, Hilti of Berkel en Rodenrijs is closely involved. Research conducted by TNO and engineering firm Hageman revealed the cause to be the faulty connection between the precast broad plates of the bulbous floors and the in situ concrete. "In September 2017, we were asked to help think about a solution for reinforcing existing bulb floors," said Marjan Vos-Pols, technical advisor at Hilti. "Now we are involved in several reinforcement projects across the country. These now involve all similar concrete floors. Together with BAM Advies & Engineering, Ingenieursbureau Hageman, Van Rossum Raadgevende Ingenieurs and ABT, we are in a task force. Initial tests showed that the top of the wide slabs of the bulbous floors were too smooth to absorb the shear force in the intermediate plane. Further official regulations surrounding this issue will be made public soon."

Possible solutions
Reinforcements can be provided by attaching strips to the underside of the floor with Hilti anchors. These are inserted into the 70 mm wide plate without touching the tie reinforcement.
Another reinforcement solution are through-and-through joints that go right through the floor. The first solution has the disadvantage that many ceiling elements, i.e. large areas, must be removed. The second requires the removal of existing floor finishes as well. Since most buildings whose floors need to be reinforced are in use, a solution must also be economical and practical. Fast, easy to apply, dust-free and noise-free.

Hilti anchors
An even more effective reinforcement solution is to apply a single row of Hilti anchors on either side of the seam between the slabs. The position of the anchors is less dimensional than with the strips and fewer drill holes are required. The anchors are drilled into the in situ concrete. Thus, the slab is roughened. Vos: "With our system, limited space is needed on both sides of the seam and the finish is not affected. After all, it happens under the floor. However, some ceiling parts do have to be removed. These are usually system parts, which makes this easy to do. And should reinforcement be encountered, a position shift with our anchors is much easier than with dimensionally stable steel strips."   

Text | Irene Teunissen  Image | Hilti
Featured image: Hilti anchors will be installed.