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  • Thin Shell: Structure Analysis

    M.Sc Year 1. TU Delft.

    8 weeks

    Team with : Peter Polhuijs, Puttakhun Vongsingha

    Assignment parallel with Folded Plate Glass Dome

     The assignment was to redesign a Heinz Isler concrete shell structure that covers a sloped area of 42m by 28m, with a height difference of 4m. The height of the structure should be around 10m. The function underneath the structure is an open air theatre. Therefore the design is a wide span structure; there shouldn’t be any columns or supports in the covered area of the structure.

    The design process involved workshops about physical form finding, computer regeneration of the design, FEM calculations and structure analysis.

    Form Finding: Multiple physical models were made by hanging fabric covered in wax. When the wax is cured, the fabric will become stiff. The fabric before being stiff in the hanging position, will form the in the near optimum shape. There is only tension in fabric surface, with no or bending moments. After being cured and flipped, the tension in the membrane will become compression and has the structure behaviour of a shell structure. For convenience of reference, we scaled our model designs roughly to 1:200.

    A larger gypsum model was made to scale 1:100 in a similar method. The surface is thinner and structural behaviour will be more visible and closer to thin concrete shell.

    FEM: The model was drawn up in Rhinoceros software. To make calculations we used different softwares packages. The NUBS-geometry was imported from Rhinoceros to FX+ for Diana to create a mesh, apply loads and constrains. Then, the calculation was done in Diana and export to iDiana to present the results.

    Load cases: A total of 6 load cases were used. These are. Dead weight & snow load in z direction, wind load in x direction , wind load in y direction , serviceability limit state with wind load in x direction (all loads), serviceability limit state with wind load in y direction (all loads) and ultimate limit state (all loads multiplied by safety factor) in x and y direction respectively.</pr>

    Displacement, support reactions, bending moment and stresses were studied. Based on these, reinforcement plan was dawn, and extra reinforcement was provided at the supports as well as at the cut outs and dip n the structure to allow for the additional stresses.