xarch start previous up next end

the skin and its bones
and how they connect
i have already mentioned a small project that was very influential for the kunsthaus - an exhibition pavillion made of plexiglas on an aluminum substructure. ephemeral buildings allow you to experiment with new techniques since building constraints may be less restrictive.

this particular pavillion (done for bmw by architect bernhard franken) was designed for indoor use and then eventually put on display outside for two weeks in september (with no rain and gentle temperatures)

the kunsthaus on the other hand required constant indoor temperature throughout the year and had all the restrictions of a museum with precious exhibits inside. thermal insulation, ductwork and electrical appliances were additional layers of the outer shell and increased its complexity.
one of the ambitious goals of the bmw pavillion was the idea to omit the metal substructure and let the plexiglass panels carry the load of the building. it turned out that this was far too difficult for several reasons. gluing the paneels side-by-side was very tricky and thermal expansion and contraction were very hard to handle. finally an aluminum substructure had to be made and the the function of the panels was reduced to a mere 'cladding'. nevertheless the acrylic panels acted as the waterproof layer of the building. thermal insulation was not required and therefore problems concerning condensation, vapor barriers and so on did not have to be considered. the same applies to fire regulations - the pavillion only had ground level spaces and escape routes were very short. for the kunsthaus the dimensions of the building made it impossible to think of plexiglas as a structural material, let alone fire regulations or thermal stability. it was quite clear that a substructure would be necessary and this would preferrably be a spaceframe made of steel. furthermore the expected shearing forces would require a triangular mesh for stiffness, especially since at the time we still thought that we would use screwed (but not welded) connectors in each node at that time. since we knew that only about 30 percent of the shell would be transparent we considered to clad the spaceframe with sheet metal und use it structurally. this would contribute to the stiffness of the ribs - a structural concept very similar to the steel hull of a ship. the ribs might therefore be thinner and more elegant than a comparable spaceframe. but calculations revealed that that the sheet metal cladding gets very heavy when it is used structurally and subsequently we abandoned this concept. the next decision concerned the connection between substructure and plexiglas cladding. inevitably the first thing to know was the shape and the maximum size of a plexiglas element that manufacturers could deliver. (i must mention that since the kunsthaus is a public building for legal reasons the austrian law does not allow to ask a supplier to become a consultant unless he refrains from bidding in the tendering process that usually comes afterwards. moreover it is not possible to give away the contract at such an early stage when the bidding documents are not precise enough to avoid a subsequent flood of additional mark-ons. therefore we found ourselves in an unpleasant situation as planners when we had to get the information from secondary sources)