Tallest precast building in the world

In this blog article we describe some of the design and construction aspects of the tallest precast concrete building in the world.

The Zalmhaven tower which is currently under construction in Rotterdam, the Netherlands is a perfect example of modern precast concrete technology and innovation. This residential tower has 58 floors and measures 215 meters with a total of 257 apartments (picture 1). Construction of the building started in October 2018 and it is scheduled to be finished by the end of 2021. Once completed it will be the tallest precast concrete building in the world.

The foundation system consists of a 38m x 38m reinforced concrete foundation raft of 2.5m thickness which is supported by a total 163 number of Tubex grout injection piles of 66m length (picture 2). The Tubex foundation piles are formed by steel thin-wall tubes with attached drill tips.  The drill tips are welded to the first steel tube segments and the piles are immersed into the ground by applying a vertical load on the tubes combined with screwing and grout injection. The 66m long piles are made of two steel tube segments of each 33m length which are welded during installation. Into the hollow tubes reinforcement cages are lowered and the entire tube is filled with concrete. These Tubex piles do not create any vibration during execution and are 100% displacement piles.

The entrance and lobby area of the building which are situated at the first levels of the building require large open spaces and therefore the structural system of the lower floors consists of a combination of cast in-situ reinforced concrete columns, shear walls and slabs. The reinforced concrete shear walls at this level are made 600mm thick in concrete grade C55/67 and the reinforced concrete columns in grade C80/95. The floors directly above this area form a two storey high transfer girder which is created around the exterior of the building (picture 3). The transfer girders are made as reinforced concrete walls with 500mm thickness in C55/67 concrete grade and they will be transferring the loads from the upper floors to the below column-wall system. 

Another structural feature of the he transfer structure is to prevent progressive building collapse by providing secondary load paths in case due to a calamity one of the lower columns is removed.

From 5th floor level onwards the residential units are starting for which the structural system is formed by precast concrete load bearing walls in combination with a precast lattice girder slabs (half slabs). The precast half slab system consists of precast slabs (100mm thick) with protruding lattice girders on which a 170mm thick reinforced concrete topping will be poured. The partially cantilever balconies are made as precast concrete solid slabs which are connected to the main structure by steel angle connections. Coupled precast shear walls in T-shapes running in x-direction and y-direction are forming the lateral load resisting system (picture 5). To form the large T-shape walls the interior precast concrete walls are properly connected to the exterior precast sandwich panels. Moreover at the intersections the interior precast walls are connected by wet concrete connections with protruding reinforcement to create a fully monolithic joint. The interior load bearing precast concrete wall thickness is 500mm for 5th to 20th floor and 400mm for the 21st to 40th floor. Precast wall thickness further reduces to 300mm for the 41st to 52nd floor. The structure of the 53rd to 58th floor consists of a steel structure in combination with 250mm thick interior precast walls. The exterior precast sandwich panel thickness varies from 400mm to 300mm. The staircase and lift are also fully made as precast concrete solid walls but are not part of the lateral load resisting system.

 

 

The contractor shall be using a climbing factory for the erection of the precast structure of the Zalmhaven tower. The climbing factory system is formed by a 14m high steel frame structure of size 45m x 55m which shall be placed on top and around the perimeter of the building (picture 6). This forms a temporary tent which is wind and waterproof and serves as a platform for the construction laborers to build one floor at a time. 

 

The climbing factory will have two overhead gantry cranes with 40 tons lifting capacity for material handling out of which one crane can be used for horizontal movement and installation of precast elements and the other crane for vertical lifting. Once one floor has been completed the factory will “jump” to the next storey by the use of a hydraulic jacking system. The climbing factory weighs around 900 tons and for the first time a jacking system with external columns and hydraulic jacks shall be used (picture 7). Some of the advantages of the climbing factory are the improved working and safety conditions as well as the high construction speed that can be achieved. The erection cycle for the Zalmhaven tower will be one floor per week (with 5 working days per week).