Step 1 - Generative Design Framework
- Design Decision 1: Architectural Openness vs. Structural Columns
- Design Variables
- Tier height
- Tier scale to bottom area
- Target tributary area per column
- Evaluators
- Average column spacing in the building
- Total column material volume needed
- Weighted average column diameter
- Most Important Tradeoffs to Consider
- Larger column spacing creates a more open and flexible floor plan, but each column must carry more load.
- Increasing tier height or tier scale increases building area and weight, which can increase column sizes and total material volume.
- Design Decision 2: Building Resilience vs Cost
- Design Variables
- Foundation type
- Level of seismic strengthening
- MEP system efficiency
- Material durability
- Evaluators
- Initial construction cost
- Long-term maintenance cost
- Energy use and cost
- Repair cost after damage or extreme events
- Building lifespan/resilience
- Most Important Tradeoffs to Consider
- Better foundations, seismic retrofitting, materials and MEP systems cost more initially, but can reduce repair, energy, and maintenance costs over time.
- With a limited budget, it is important to decide which upgrades provide the most resilience per dollar.
- Design Decision 3: Building Mass vs Profit
- Design Variables
- Building height
- Floor plate size
- Number of floors
- Setbacks or tapering
- Evaluators
- Total floor area
- Estimated profit or rentable area
- Facade/surface area
- Construction cost
- Structural complexity
- Most Important Tradeoffs to Consider
- More building mass can increase floor area and profit, but it also raises facade area, structural demand, MEP loads, and construction cost.
- Taller floors or higher-level spaces may generate more revenue, but they are also more expensive to build because they require stronger systems, larger foundations, and more complex construction.
Step 2 - Generative Design Study
Chosen Design Option: Option 1
Objective: The objective of the study is to find a design option that provides a good amount of open floor space while keeping the required column sizes and total column material volume reasonable.
Model: The Dynamo model creates a three-tier circular building form, similar to a stacked birthday cake. Each tier is modeled as a cylinder, and the three cylinders are joined to create the overall building mass. The building is then sliced by floor using the constant story height to estimate the floor area at each level.
The graph calculates the floor area for each story, then estimates the perimeter from the floor area assuming the floors are circular. The perimeter is used to include a simplified facade load in the floor weight calculation in additional to the floor area. The graph then calculates the cumulative weight supported at each level. This means the lower floors carry the weight of all floors above, so the lower columns are larger than the upper columns. The number of columns is based on the target tributary area per column. Then the model calculates the actual tributary area, average column spacing, required column area, column diameter, and column volume. The weighted average column diameter is used so floors with more columns have a larger effect on the overall average. Column sizes were determined using floor weights.
Pictures of the Dynamo node graph are included at the end of Step 3.
Design Variables
- Tier Height: Controls the height of each tier and the total number of floors.
- Tier Scale to Bottom Area: Controls how much smaller the upper tiers are compared to the bottom tier.
- Target Tributary Area per Column: Controls the approximate column spacing. A larger value creates fewer columns and more open floor space.
Constants
- Base Radius: 180 ft
- Story Height: 15 ft
- Floor Load: 120 psf
- Facade Load: 30 psf
- Allowable Column Stress: 4000 psi
Evaluators / Outputs
- Average Column Spacing in Building: Higher values are better for architectural flexibility because they mean fewer columns and more open floor space.
- Total Column Volume: Lower values are better because they reduce material use, cost, and embodied carbon.
- Weighted Average Column Diameter: Lower values are better because smaller columns are easier to transport, construct, and coordinate with the building layout.
Main Tradeoff
The main tradeoff is between architectural openness and structural demand. Increasing column spacing improves the floor plan, but it also increases the load carried by each column. This can lead to larger column diameters and more total column material. Tier height and tier scale also affect the results because taller buildings and larger upper tiers increase the total weight supported by the lower columns.
Step 3 - Generative Design Study Results
Scatterplot:
Parallel Coordinates Graph:
The plots above show the tradeoff between average column spacing, total column volume, and average column size. In general, as column spacing gets larger, the building has fewer columns and more open floor space. Maximizing column spacing is good architecturally because it creates a more flexible floor plan.
However, having fewer columns(each column having larger tributary area) means each column needs to carry more load. This increases the required column diameter and may also increase the total column material volume. The other inputs also affect this relationship. A taller tier height creates more floors, so the lower columns support more cumulative weight and become larger. A larger tier scale creates bigger upper tiers, which increases floor area, building weight, and column demand. Smaller tier scales reduce floor area and weight, but also reduce usable space.
As seen in the scatterplot, increasing spacing always increases column size, with red showing the smaller columns and blue showing the larger columns. Total column volume decreases as spacing increases up to around 30 ft, stays relatively constant until around 50 ft, and then increases again at larger spacings. This suggests that increasing spacing is efficient only up to a certain point. After that, the columns become large enough that the design becomes less efficient.
I would use this information to avoid the extreme options. Very small spacing creates too many columns and limits architectural flexibility, while very large spacing creates oversized columns and higher material demand. Based on the scatterplot, I would choose one of the green options right before the colors shift into blue, because it gives relatively high column spacing without making the column volume or average column size too high.
Full Dynamo Study Graph:
Notes / Limitations:
- Values are based on 4 ksi concrete and general numbers from experience. Exact numbers depend on many factors, such as building height, occupancy type, loading, structural system, and code requirements.
- Simplified structural assumptions were made for the purposes of this assignment. The results should not be taken as a final structural design.
- In real life, column sizes have a minimum practical size, but this was neglected here to make the comparison between options clearer.
Zoomed in:
