bring compression forces in the concrete. Under this core there are vibro combination piles which are a combination of a cast in place (in ground) pile with a prestressed prefab concrete pile. The prefab pile is stiff as well under tension loads. Because the foundation of the tower lies next to the harbour there are structural elements needed to keep it in place. A steel sheetpile wall together with bracings are bearing the horizontal loads on the tower. Stiffness of the floors The floors form diaphragms that carry the wind loads to the cores. Diagonals in the floor plane model these floors. We have recalculated the forces in these diagonals to determine the wind forces in the steel frame and the concrete floors. The ESA-Prima Win Model The entire structure is modelled as a 3d model in ESA-Prima Win. The steel structure, the concrete structure and the foundation are all designed and engineered in one model. With this model we have made different checks and investigated several alternatives. The different checks are described in this chapter. 3 Dimensional rendering The 3d rendering allowed us to show the ideas for the structure to the different parties in the design process. With the pictures that ESA-Prima Win provided we were able to make clear the philosophy of the structure and the consequences of different alternatives. Load combinations As stated before, the tower balances on the big XX columns. Therefore the vertical loads that work on the structure are divided in three parts. One part (of the loads) in the cantilever, one part in the bridge above the street and one part above the concrete core. Beside the vertical loads, wind loads are also present on the building in four directions. In the Dutch building codes we use four load factors: 1,2 and 1,35 for the dead loads, 1,5 for the live loads and 0,9 for the beneficiary working dead loads. With these load factors we have made a selection of the possible combinations. We have worked out 20 load combinations for the ultimate limit state and 15 load combinations for the serviceability limit state. Steel code check The steel parts are checked with the embedded steel code check of ESA-Prima Win. This check helped to engineer different alternatives during the design process. With the weight data that ESA-Prima Win gave we were able to estimate the costs for the structure very quickly. Pile foundation The pile foundation is an integral part of the structural model. The flexible supports are put under the foundation of the XX columns and the concrete core. To investigate the long time effects of creep we used the same model. We just adapted the flexible supports to the smaller stiffness. 2nd order calculation To investigate the second order behaviour of the structure we have used the three dimensional model. With the model we could analyse the behaviour of the structure under horizontal loads and the increase of deformations due to the vertical loads. Dynamic behaviour Since the tower has a particular shape and slenderness the dynamic behaviour of the tower is very interesting. To make sure that the accelerations are beneath an acceptable level we have used the dynamics tool in ESA-Prima Win. ESA-Prima Win determined the lowest Eigenfrequencies. These Eigenvalues gave a good idea of the natural flexibility of the structure. With the Eigenfrequencies we could calculate the accelerations of the tower and make sure the comfort for occupants was guaranteed. Shortlist Location: Terwenakker, Rotterdam, The Netherlands Height: 80 metres from street level to the highest point Width: 30 metres north - south44 metres east - west Storeys: 22 storeys and one basement Used steel: approximately 1000 tons of high grade steel S460 Cubic metres concrete: 2.500 m³ Floor area: 12.000 m² Number of apartments: 12 to 36 (depending on the size) 103
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