De Rotterdam is one of the largest buildings in the Netherlands. Described as a vertical city, it contains offices, apartments and a hotel as well as conference and fitness facilities, shops, cafes, restaurants and parking. It is 44 storeys high and has three interconnected towers rising from a single base plinth. The mass of each tower is offset by 3-8 metres in various directions at half the total height. This makes for a dramatic structure and enhances wind stability, but causes uneven settlements.

Royal HaskoningDHV provided the structural design for the building. Challenges included the building’s height, its open facades, staggered towers and the need to ensure the underground parking does not leak groundwater. However, the most challenging issue was the soil.

How to avoid the core of the building sinking more than the outer edges

The city of Rotterdam sits on a thick layer of clay sandwiched between two load-bearing sand layers. Buildings in Rotterdam are typically supported with piles on the top sand layer so the building will undergo settlement as the clay compresses. The size and height of De Rotterdam meant significant settlement and settlement differences were expected.

Our initial assessments showed that, over a 50-year period, the deformation would reach around 280mm in the middle of the building and 60mm at the edge. A series of 3D models were then used to investigate the impact of such settlement on forces and deformations within the building.

To mitigate the impact, jacks were placed under the columns in the bottom basement to avoid damage to floors, walls, columns and facades resulting from settlement. The columns themselves were made using high-strength concrete and structural steel to keep them as small as possible while maximising the forces they could support. The offset of the building masses at half-height of the building was made possible by applying concrete trusses as transfer structures and modern jack-technology.

Royal HaskoningDHV is proud to have made a meaningful contribution to the realisation of this complex building, which was finished on time and without major problems.
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    To avoid the core of the building sinking more than the outer edges.