Kaaibrug Gets a New Boost from an Unexpected Source

Reinforcing a bridge without excavating the embankment on either side? It turned out to be possible at the Kaaibrug in Klundert. The 28 Relast lateral force anchors from Würth ensure that the columns once again comply with current design codes. A relatively simple intervention, but one with a significant impact on the bridge’s remaining service life.

The municipality of Moerdijk commissioned an inspection of several bridges and engineering structures in Klundert after a risk analysis revealed that various structures were being subjected to heavier loads than originally anticipated. Nebest conducted the reassessment of the Kaaibrug and found that, among other things, the shear capacity of the central girder column was insufficient for current traffic loads. The reinforcement in the deck also no longer met current requirements. In line with the Moerdijk municipality’s policy of reinforcing engineering structures whenever possible rather than replacing them, the bridge was repaired.

Anker as an alternative

“To reinforce the central girder, we looked for a reinforcement method that was not only structurally sound but also practically feasible,” says Tim Pauli, a structural engineer at Nebest. “Reinforcing it the traditional way would mean we’d have to drill all the way through the columns and anchor them on both sides. To do that, we’d have to excavate the soil behind the columns. That’s obviously a major undertaking and would make the project considerably more complex and expensive.”“ The Relast system offered an alternative. ”The beauty of this system is that the anchors are drilled in and bonded from one side,“ explains Pauli. ”Before curing, they are tightened to the specified torque, eliminating the need for a structural connection or excavation at the rear of the column. That turned out to be the ideal solution here.”

Drilling from a pontoon

BATEC was responsible for the reinforcement work. “Nebest first used a rebar scanner to accurately map the existing reinforcement and marked the drilling points. The anchors were then drilled from a pontoon using a diamond drill mounted on a tripod,” explains Sjoerd Groot, project manager at BATEC. “A total of 28 Relast anchors were used for the Kaaibrug, each with a diameter of 22 millimeters and a length of approximately 1.2 meters.” According to Groot, installing the anchors themselves turned out to be relatively straightforward. “Drilling, bonding, and tightening to torque (50 Nm). The curing phase does not affect the rest of the schedule. This allows the anchors to be installed quickly and tightened to the specified torque. The entire operation therefore took only a few days—including filling all the holes and applying a coat of paint to the columns. You can hardly see any trace of it now.”

BATEC also reinforced the bridge deck. “To that end, the bridge deck was renovated in phases using high-pressure water jets—up to 2,500 bar—carefully removing deteriorated concrete without causing unnecessary damage to the structure,” says Groot. “We then installed additional reinforcement and refilled the concrete. Combined with the Relast anchors in the central girder, this ensures that the Kaaibrug is structurally sound for the next thirty years.”