85 In General The block of flats “OBYDICK” is planned to be erected in Bratislava. The structural design for the building licence was elaborated by ELTER Constructions s.r.o. of Slovakia. The detail structural design was elaborated by Ing. Daniel Bukov OK TEAM . Basic Parameters of the Building The total number of floors is 25 above ground level and two floors below ground level. The total height of the building is 85.27 m. The total area is more than 21.000 m², that is more than 650 m² per floor. Main bearing system The main bearing system of the building is created from cast instead of reinforced concrete. In the middle of the building is located a small core with the dimension 5.85 m x 12.5 m, the thickness of the walls are 200 mm. Oval columns support perimeter concrete walls. These walls create an outside tube. The tube transmits a big portion of the horizontal loads. The outside wall has thicknesses from 500 mm to 200 mm. The ground floor level has the thickness of the wall: 500 mm. On the inside layout circle there are located columns with diameter of 600 mm. Method of Detail Designing For the computation of the shape of the structure, cross sections, thicknesses and loads were taken into account. New information concerning the openings (location and dimension) were also included in the structural analysis. For the calculation of the main bearing system, the 3D model is created. For the separate parts, an own model was created (floor slabs, columns, attic etc.). The results from the global calculation are included into separate models as external loads or are included in the proportioning. All calculations are performed according to the Slovak valid codes. Computational model A 3D computational model, created by the finite element method, calculates the main bearing system of the building. The foundation slab, including soil interaction, core walls and columns, is exactly modelled in this space model. Floor slabs are also modelled precisely, but for computational reasons only a very large mesh is used. For the seismic response, the calculation linear response spectra method is used. For a combination of modal responses, the CQC method is used. Soil interaction has been solved with the theory of half space. The proportioning of the foundation slab and core walls is done in this model without any other influence or consideration. For columns proportioning from the global structural calculation, only normal forces have been adopted. The bending moments were added from floor slabs analysis. All calculations are performed by NEXIS 32.60.20 program (ESA-Prima Win). For tall buildings it is necessary to take into consideration the influence of the longitudinal deformation of the columns on the main bearing system. Deformations of columns due to high compression have to deal with elastic deformation creeping and shrinkage of the concrete. Floor slab levelling eliminates some deformation; some has to be predicted by calculation. It is also necessary to take into the consideration the decreasing normal forces in the columns due to the decreasing effect of the live load depending on the number of the floors above. Influence of the settlement in the core area, which is higher than settlement in the perimeter columns, also plays a role in the designing of the bearing system. For seismic response calculation, different sub grade properties have to be used (stiffness or resistance of the soil in the case of the dynamic loads is higher). At least two models have to be calculated for one proportioning. With ESA-Prima Win we have the possibility to make many calculations in real time Foundation Slab Design and Calculation The internal force and the calculation of the foundation slab on the 3D model for global structure analysis were used here. The proportioning was performed in the same model. Columns calculation Calculation Columns are calculated in a separate calculation. Normal forces are adopted from global structural analysis. Bending moments are adopted from floor slab calculation. For each type of column, a calculation is performed and influence due to live load is taken into consideration. Perimeter walls- tube calculation The tubes are perforated by window openings. The critical parts of the tube are those where they are connected to the columns. For these parts a very fine mesh was used, also a separate calculation of the detail was performed. Floor Slab Calculation Floor slabs are calculated in a separate model, punching shear and connection to the core walls is taken into account. In this model also bending moments in the columns are calculated. Around the columns a more dense mesh is used. On one side, there are decreased bending moments in the columns, and on the opposite side, there are increased positive moments in the floor slab. The proportioning of the slab in the columns is done based on sections and the reinforcement is distributed accordingly. Conclusion In order to obtain a solution of such a demanding structure, a very effective program for the calculation of internal forces calculation is needed. It must be able to prepare the structural model and to offer various possibilities to check the results. The incorporation of the proportioning in one package is also a big advantage. ESA-Prima Win fulfils these requirements. High rise building
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