City Gate, standing at 144 -metres- tall, is Gothenburg’s tallest office building, located on a narrow plot near the city centre. The building’s slender profile posed significant engineering challenges, particularly in ensuring stability on a clay foundation.
CHALLENGE
CCL were tasked with implementing vertical post-tensioning using CCL XV tendons and active CCL XM anchors, involving the installation, tensioning, and grouting of 67 tons of strands. Key challenges included stabilising the slender structure on clay, prompting a design shift after tests showed natural uplift resistance. The narrow base and fast jump form construction also added complexity.
SOLUTION
CCL’s early involvement enabled a detailed analysis of the clay foundation and structural needs. Testing pile friction led to a shift from pile-tensioning to post-tensioning the core to resist wind-induced tensile loads. This added compression, allowed thinner walls, reduced concrete and reinforcement use, improving both structural stability and sustainability.
BENEFITS
- Structural Stability: Post-tensioning the core resisted wind loads.
- Sustainability: Thinner walls reduced concrete and reinforcement, cutting CO₂ emissions.
- Efficient Construction: One-floor-per-week progress without compromising integrity.
- Cost Savings: Lower material use reduced construction costs.
