Everything must be accurate to the centimeter

Construction and installation of rolling door floodgate Kornwerderzand

The design and realization of the 60 meters longer roller door in the floodgate at Kornwerderzand, is more than precision work. After all, how do you catch the tolerances? And how do you place a 950-ton door on the rails to the nearest centimeter? Project engineer Pieter Woudenberg and project leader Edwin Schepers explain how they went about it.

Two completely new floodgates will be built at Den Oever and Kornwerderzand. They will protect the hinterland from extremely high water. The floodgate at Kornwerderzand consists of a rolling door that can be driven over a threshold in the waterway. HSM Steel Structures was engaged for the realization and installation of the rolling gate at Kornwerderzand. Woudenberg explains how the principle of the rolling door works: "If a storm is expected, the rolling door is driven into the fairway. Due to the high water on the Wadden Sea side in times of storm, the roller door will be pressed against the concrete by the water pressure and thereby completely reverse the water."

Own yard

The rolling door is 950,000 kilograms in weight, 56 meters wide and 15 meters high. HSM Steel Structures built the enormous structure at their own yard in Schiedam. Woudenberg: "We are strong in the larger civil projects. Our site is fully equipped for that and we are located on open water. We therefore always try to make the components as large as possible so that you can place it at the final destination in one go efficiently and with as little disruption as possible. For example, we as HSM have already built several bridges longer than 200 meters completely on our site and installed the entire length directly on site."

Millimeter work

The challenge in the design was accuracy. "We are dealing with a large structure where you have to work with tolerances of millimeters. The interfaces are the most important part. The steel door has to connect seamlessly to the concrete and turn completely when it needs to close. There is a lot of welding involved. The heat from the welding causes the material to deform. We have already taken this into account in the design and construction process. For example, during the construction process you have to continuously measure and build in pre-formed molds. In the design, welds are chosen as small as possible which ensures less heat input and thus less deformation."

Winch system

The design is unique, according to Schepers. "The roller door stands on two bottom rollers and is set in motion by a winch system. Attached to the roller door is the sheave beam, through which the winch cables are sheared to move the roller door. The winch system consists of two cables: a closing cable to pull the roll door into the fairway and an opening cable to pull the roll door into the door case. The under rollers run on a rail that is embedded in the concrete. To clean the rails of mud and remove other large objects, the roller door is equipped with a jet system that sprays the rails clean."

Tension rises

The complete structures, roller door and motion gear have been thoroughly tested and are ready for transport. The roller door is completely built and will be sailed by sea to the Afsluitdijk on a sea barge. Schepers: "We will then have everything on hand to hoist the door into place. This has to be done within two days because the waterway has to be closed." The moment of hoisting in is another exciting moment. This must be done to the centimeter. "The door must be positioned exactly on the under rollers of 40 tons each. We are already preparing that. Because we already have it all figured out, tested and prepared at our yard, we expect to be able to smoothly perform the installation on site in March 2023. Then only the weather has to cooperate."