Your Design Journal entries this week should highlight your design thinking that influenced your decisions about:
- your overall strategy and the features of the structural system
My structural system uses a steel-concrete hybrid approach optimized for the curved geometry of the building design and open spaces on the first two levels.
- the material and framing system selected
The primary material of the structural system is steel for the columns, beams, and trusses, supporting floors of 3” LW concrete on a 2” metal deck. I used steel W10X49 columns, W14X30 beams, W8X10 beams for the beam systems, and both 4’ and 5’ tall Howe Flat Trusses. While I initially wanted to use a mass timber framing system, this wasn’t feasible due to the project site (NYC). To remain in alignment with my sustainability goal of minimizing the building’s embodied carbon, I want to specify the use of high-recycled-content steel and low-carbon concrete mixes like GGBS or fly ash.
- the locations of structural columns and major framing elements
I used a radial grid to match the circular building design, with maximum spacing between columns at around 25’ and beam systems spaced at 4’. For the first two levels where I wanted to maximize open spaces, I use steel trusses with spans of 45’-52’ to prevent columns from breaking up the open exhibition spaces. On the remaining 6 floors, the beams and columns are more regularly spaced according to the radial grid intersections along the building perimeter, with beams spanning 16’-25’.
- any special structural challenges
The curved geometry of the building made it slightly more challenging to space the beams and columns evenly. Also, my initial design goals of providing open exhibition spaces required some longer-span trusses in place of regular beam elements. With regard to the concrete elements, the site’s proximity to water may require careful waterproofing of the concrete foundation.
Steel skeleton:
Steel skeleton with floors:
