Selection
This building will be constructed using Two-Way Flat Slab strategies. Two-way sitecast concrete was selected because of the needed flexibility for the irregular angular footprint of the building and the possibility to deviate from column grid up to 10% of the span. The system will allow for a fairly thin slab and the use of round columns. The round columns suggest the shape of the surrounding trees and add to the "forrest". Even though the round column needs to be larger in diameter, it is important to my design. The whole system provides noncombustible construction needed for a five story building. The slab itself will provide opportunities to utilize its thermal mass, especially on the east side of the residential tower, which will be curtiain wall.
Description
The building have a basement which will sit on a conventionally reinforced structural slab that rests on structural precast piles 80-100' deep, because of the waterlogged soil. 10' tall square columns will hold the first floor slab (10" thick). The first through fifth floor columns will be round, (although those which are burried in walls could be square). Column grid spacing will be roughly 30'x3o', with 14' tall columns on the first and second floors, and 11' tall columns on subsequent floors. All floor slab thicknesses will be 10". Edge columns will need to be 24" diameter and center columns will need to be 18" diameter. It may be desirable to use arrangements of reinforcing in the slab called shearheads to avoid overly large drop panel widths.
6" Non-load bearing precast insulated sandwich panels with brick ties will infill as the wall system, and recycled brick will be the veneer. This is true in several locations- not much differently than shown in previously posted renderings of the building. Other locations will use curtian wall, and the first floor will probably use a storefront.
The roof of the smaller building will be a green roof. I will be considering this tommorow and revising the post as needed.
The roof of the low portion of the larger building will also be a green roof, but will utilize the self irrigating low maintence grass roof tiles, introduced by Toyota, which do not require additional sizing of the structural system, because they are lightweight.
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2 comments:
Anne, Cast-in-place concrete for your structure sound reasonable. The largest structural bay is 30’ x 25’; you should be able to reduce your slab thickness to 8”. With some adjustment of the grid to 25’ x 20’, the slab could even be 7” thick only.
Center columns are typically the biggest, as they have the largest loads (to determine the load visually, divide each area between two columns in two, half of the load goes to the center, half to the edge), edge columns are smaller, and the corner columns the smallest. Some of the continuous walls at stair and elevator could become load bearing and also help to brace the building.
I don’t quite understand the choice of back-up for the brick veneer: insulated pre-cast panels. Pre-cast is typically economical when there is a large quantity of repetitious elements, when the amount of elements can be reduced to as few of up to 11’ x 30’ panels as possible (size determined by transportation, quantity held low to erection cost). Your building is highly irregular, perfect for a cast-in-place structure and perfect for a brick veneer. But for your back-up I would recommend a 6” light metal stud wall with exterior sheathing, air barrier and 2” to 3’ rigid insulation, 1 ½” air space and the veneer.
The sizing for the edge columns came from page 115 in the studio companion. This recommended the edge columns to be considerably larger- I went by the chart. I'm sure the slab can be reduced for 30'x25', and I will see if the grid can be adjusted at all. I wasn't sure about the precast back-up myself, but I really wanted the building to be airtight and well insulated- thus my original curiosity about the sip panels. Maybe metal studs can do this as you describe and we studied in our technical lecture.
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