Nemetschek Engineering User Contest 2009 • Category 2: CAE Housing & Buildings 65 2 Achmea office, Zwolle For the round outward slanting high-rise part of the building a lightweight structure consisting of steel columns and beams and composite steel/concrete floors was chosen. Design In his preliminary design the architect chose for a floor bearing structure consisting of a beam over three columns. One upright steel column (610 mm dia.) at the right gable and two (middle and left gable) slanting ones towards the outward slanting left gable. This would create enormous horizontal forces on the prefab liftshafts. The design of the architect was slightly changed by reversing the angle of the middle columns (2 x 406,8 mm dia.). The horizontal forces resulting from the slanted columns neutralise each other largely. The outer column (610 mm dia.) slants 1200 mm outward per 3600 mm storey and by means of iteration a 600 mm slant for the middle columns (2 x 406,8 mm dia.) was determined. This was a logical choice, for the middle column carries approximately twice the load of the outer columns. The structure was modelled in Scia Engineer and an ocean of results became available. To verify the results of the 3D calculation, a 2-dimentional calculation was converted to “3-D”, with utmost exertion and many hours of labour, to check the resulting horizontal forces on the prefab lift-shaft. The results came within 5% of each other. Designing this building using Scia Engineer was of enormous value to the project. Interesting numbers and facts The torsion moment on the high-rise lift shaft exceeds 39.100kN.m. The bending moment on the high-rise lift shaft exceeds 129.560kN.m in the extreme case. The shear force on the high-rise prefab lift shaft is ca. 4.950kN. The extreme windload on the total structure exceeds 6100kN (610.000kg). The expected extreme horizontal deformation of the roof will not be greater than 45 mm. Steel columns with a diameter of 610 mm, a thickness of 12 mm and a length of 25.100 mm were used, as well as columns with a diameter of 406,8 mm, a thickness of 20 mm and a length of 24.150 mm. HEA600 steel beams with a span greater than 13.500 mm were used in the top storey floor. For the high-rise part of the building no storey has the same size due to the slanting of the left gable and the beams have varying lengths for the eleven storeys. More than 573 prefab concrete piles make up the foundation of the building. In the high-rise part of the building it took the contractor 14 days to assemble the structure of one storey and proceed with the erection of the next one. The building was completed within 20 months.
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