For a sustainable built environment, the choices for materials commonly comes down to Steel or Mass Timber. For this reason, I will be avoiding using concrete on a large scale. Only to use concrete for concrete topping and foundations.
Pros of Timber: Lightweight, Sustainable, Low Carbon Footprint, Aesthetic
Cons of Timber: Fire Rating Issues, Shorter Spans
Pros of Composite Steel: Recyclable, Modular, Fireproof, Larger Spans
Cons of Composite Steel: Higher Carbon Footprint than Timber, Higher Cost, Longer Scheduled installs
For this project as an Exhibition Center, it is important to have large spans so that columns do not interfere with exhibits. Furthermore, the curvy nature of the building may be wasteful for timber framing. Hence, the building will be a composite steel framing system.
Beams and Girders: W12x26 (to be updated once HVAC is considered as loads and penetrations)
Columns: W10x49 spanning two floors
Foundations: Isolated Footings + 5” Slab on Grade to make a raft foundation
Floors/Decks: 3” LW Concrete on 2” Steel Deck - typical Vulcraft Composite Deck
Structural Walls: N/A - to use braced frames around the core and middle of bldg once HVAC penetrations are known
Exposure of Structural System
The structural system will be hidden from the viewers. Gypsum board to be used around columns, Our floor sandwich is pretty relaxed so ceiling baffle systems to cover up beams and girders. Furthermore, floor finishes to be applied to the concrete topping.
Due to the presence of high curtain walls, some columns may be exposed to the exterior view. Saving up on the cost of materials to cover up these systems on the exterior is cheaper and more sustainable.
The building is circular on one side and flat on the back. Hence, the grid system for the Exhibition Center is pretty complex. It starts with a rectangular grid in the middle, which have the office spaces, kids zone and education rooms. However, as we move radially outwards, this switches to a circular grid system until the exterior walls.
For the atrium space, the shaft extends all the way up to the roof. The roof structure is self supported, Once the parametric roof is panelized, the framing members will support the dome in an arch-like manner. Hence, the framing for the atrium simply needs to be a void with columns at the edges of the void to end the framing system at these edges.
Depth of Members & HVAC
As a Structural Engineer, I can easily design preliminary beam sizes ranging from W12 to W24 for this system on RAM Structural Systems. Once I know how my HVAC routing, I plan to update the framing members to more relevant depth sizes.