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From CAD User AEC Magazine  Vol 22 No 11 - NOVEMBER/DECEMBER 2009

The Malvern Hills find an echo in the new Worcester Library - thanks to Bentley's GenerativeComponents

remodelling. It has not been in use on a daily basis for over a year, now - being reworked as the design evolves. CONES AND BAFFLES At the point where the naturally ventilated air leaves the building, it is assisted by the unique configuration of one of seven cones. Each cone is designed by a self- supporting sail shape, enabling them to stand up under their own dead weight, and sitting on the top of each cone are series of baffles and glazing. Each cone had to be modelled independently of the others, and had constraints built in to fulfil a number of functions - to facilitate efficient airflow and to allow the maximum amount of light to enter through the atrium below, so that visitors could look up through all the floors and out of the atrium over 21 metres above them. Modelling such complex asymmetrical geometry, which depended on many different factors, would have been either impossible using traditional 3D modelling, or at best would take at least a week to look at each design option. It would also be likely to contain any number of inaccuracies. The design has many factors, all of which have consequences for the rest of the design, with wall construction, baffle interaction with the walls, materials used, and changes in how the building is to be used all playing a part. The only way that any sort of solution could be achieved in the available timescale was to use GenerativeComponents - which converted the seemingly insolvable problems into something that could be achieved within seconds, rather than weeks and months! THE BAFFLING SOLUTION The orientation of the tops of the baffles, and how they intersect the roof cones, was specific to the environmental and contractor's requirements. The two cones to the south maximised the solar penetration to increase solar gain, increasing the stack effect, and the two northerly oriented cones optimised northlight and reduced the need for internal shading. One of the cones was also angled to the East to reduce the height of the baffle. Further complexity arose from the contractors requiring the baffles to be as small as possible. Wind tunnel tests, though, and the ventilation strategy defined a minimum height of the baffles for them to work effectively. Every design change, conducted using GenerativeComponents, provided an accurate model each time, and also proved,that the baffles were a viable integral environmental design feature, and that they should not be removed from the scheme. MAINTAINING CONTROL Although GenerativeComponents was used, it was kept under the control of Feilding Clegg Bradley Studios. They were running a design driven project, and wanted to be the designers. They required more of the software than could be provided by a traditional 3D model, but didn't want to use a self-generating form, or put in place 'hard-code' restrictions that prevented them from remodelling or making decisions about the design under their own terms. The key to this was starting off with a well- designed parametric model with a Microstation and Excel interface. Simple changes within the Excel sheet were used to modify the model. For instance, rotating the plane in the bottom of the baffles around an x and y axis which demonstrated how much of an effect it made to the shape, both for aesthetic and aerodynamic purposes - and similarly for the orientation of the top of the baffle and, therefore, the glazing angle. Besides the many variables that had to be considered to orientate and optimise the height of the cones and baffles, GenerativeComponents was also used to define the L-shaped timber ribs to the bottom halves of the baffles, each of which are unique, as the form changes along each baffle. Using a traditional method would mean that these could only be generated by creating many sections along each edge of each baffle. 250 TONNES SAVED Besides using GenerativeComponents to handle complex design problems that would have been virtually impossible to solve otherwise, the software enabled the architects to omit 250 tonnes of steel from the roof alone - confirming that the use of cross-ply timber panels could be used instead of the originally proposed steel beams. With less weight in the roof, support columns could be smaller and fewer, assisting in maximising the transparency of the spaces below. Altogether a satisfactory conclusion. www.bentley.com

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