到展覽現場看了各個提案的圖面,每支參加競圖的團隊都做了大量的圖面解說,包括基本的平面立面剖面、3D示意圖、基地分析、活動分析等,但是 Toyo Ito 提出的東西更為完整,把結構、設備等分析都做出來了,我認為這是一種「精神」的表現,姑且不論那些提議是否可行,但是 Toyo Ito 帶來的東西就真的值得一看。
Construction Process
The structural system is developed together with the construction method to realize the freeform geometry in rational and efficient manner. The freeform concrete surfaces are shotcrete (spray concrete). It is commonly utilized for tunnel construction and suitable for curved surface. It can be shot horizontally or vertically. Rather than constructing doubly curved formwork that is expensive and time consuming on site, the temporary structure in the void creates faceted surfaces that best-fit the finished surface. Between the temporary steel work, expanded metal mesh is Expanded metal mesh spans between the temporary steel work to act as faceted formwork. 150mm thick concrete can be shot at one time. The surface layer of 25mm is shot separately without large aggregate to achieve smooth surface finish.Concrete thickness varies between 200mm at the top floor and 350mm at the bottom.
Sprayed concrete Construction method
Typically, an expanded metal mesh is used as a permanent back shutter and the reinforcing mesh is then fixed to this. The concrete is sprayed onto the expanded metal and the reinforcement isfully enclosed.The concrete is typically sprayed using one of two methods. With the dry process.the dry constituents of the concrete are mixed in a portable batching plant and the water is added to the mix at the nozzle. With the wet process, the water is added to the batching plant and premixed with the dry constituents and the wet concrete is sprayed from the nozzle. The benefits of the wet process are that there is greater control over the concrete mix as the concrete is often mixed off site by readymix contractors and delivered in lorries.lt is common practice to apply the concrete in two layers. The first thick layer is usually applied using the wet process. Once sufficiently cured, a second, thin finishing layer is then applied using the dry process.lt is essential that the finished product is cured appropriately to mitigate shrinkage and to ensure the design strength is achieved.Spraying concrete is a messy process. Some concrete will rebound a'nd some will pass through the expanded metal back shutter. It may be necessary to install temporary protection to avoid polluting the surrounding area.