With more than 20 years of experience in element analysis, the station team has worked on many projects that fall into the domain of reinforced and moulded plastics.

A Success Story: The Structural Design of GRP Crowns for The Sibaya Casino

Construction of the Sibaya Casino complex is almost complete, and anyone passing by will notice the dome crown decorations, the largest of which is 5.5m high and 7.5m in diameter. These are constructed from GRP, and are supported by an inner steel structure. They were fabricated by G7 Technologies, a small company based in Westmead. G7 contracted the TS to carry out the structural design of both the GRP cladding and the steelwork. The crowns are subjected to gravity, thermal and wind loading, and this necessitated the use of finite element analysis (FEA).

Virtual 3D computer models of the crowns were constructed in an FEA software package, with the appropriate boundary conditions and material properties (see Figure 1). It was proposed that CSM or CSM+UD be used, and the idea was to determine which was appropriate and what the wall thicknesses should be, given the loading conditions. Once these parameters were established, the reaction forces on the steelwork could be determined so that the steelwork itself could be designed.

To simulate the wind loading, some of the exposed surfaces were subjected to a pressure of 1.52 kPa, such that the wind direction caused a bending moments to be induced (see Figure 2). In addition, the model was subjected to a temperature load of 50oC. After choosing an appropriate safety factor, the wall thicknesses and placement of CSM or CSM+UD was finalised. An idea of the stress distribution is given in Figure 1.

In terms if the steelwork, it was assumed that the GRP contributed to the structural integrity of the whole, and was note merely cosmetic. The design was carried out in compliance with SABS 0162-1:1993, and the loads applied to the steelwork were obtained using the limit states design approach; essentially a combination of 1.2 times the dead weight of the structure and 1.3 times the wind induced pressure loading). From the results of the FEA, the greatest forces and moments were used in the design of the steelwork.

The crowns have been fabricated and installed. A helicopter was used to position them, which caused some concern at the TS because the structures were not designed for this kind of loading, but the operation was completed without a hitch.

A Success Story: The Structural Design of a GRP Halo for The ABSA BUILDING

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