Step 1 - Generative Design Framework
A very brief description of the design decisions from Step 1 following the Generative Design Framework.
- Structural Weight vs Building Roof Drift
- Design Variables
- Column and Beam Member Sizing
- Spacing of the bays (number of columns along building width/depth)
- Material Type/Strength
- Story Height
- Evaluators
- Total building weight
- Maximum Roof Drift
- Most Important Tradeoffs to Consider
- An increased size of structural members like columns and beams will reduce the building roof drift but will increase structural weight.
- A more open bay layout will decrease structural weight but increase the overall roof drift.
- A stiffer lateral force resisting system or increased material strengths can improve on roof drift but can lead to an increase in overall cost (although this is not an evaluator for this generative design).
- A decreased story to story height will decrease flexibility and improve on drift ratios but will increase structural weight.
- Material Cost vs Carbon Footprint
- Design Variables
- Structural Material Type
- Member Sizes and Floor System type
- Facade Material Type
- building width/height
- Evaluators
- Material Cost
- Embodied Carbon
- Material Quantity
- Most Important Tradeoffs to Consider
- If structural members are reduced in size too drastically, although they will have a decreased material cost and carbon footprint, the strength of the structure will be greatly reduced. This will then lead to a reduction in structural performance.
- There’s often a correlation between lower costing materials and higher embodied carbon.
- Construction Cost vs Daylight Quality
- Design Variables
- Window to Wall ratio
- Structural bay/grid spacing
- Building Width/depth
- Floor to Floor height
- Shading depths
- Evaluators
- Construction Cost
- Daylight Exposure
- Facade Area
- Most Important Tradeoffs to Consider
- While larger floor to floor heights can reduce construction cost to a certain extent, there will be larger structural members required. Additionally, a larger floor to floor height will decrease daylight penetration.
- Higher window to wall ratios can increase construction cost due to an increased facade complexity but will provide greater daylight exposure within the structure.
- Adding shading elements would help control daylight exposure but would increase the cost of constructing the facade.
Step 2 - Generative Design Study
- A more detailed description of the design decision from Step 2 that you decided to run a Generative Design Study with.
The generative design decision I decided to run a generative design study with was the Structural Weight vs Building Roof Drift.
Overview: A building with a fixed structural height and width is being built. The beam and column member dimensions will be varied, thereby varying the stiffness of each element. The total volume of the beams and columns will determine the estimated structural weight based on material density. Roof drift shall be estimated through an estimation of structural stiffness. The total roof drift and story heights will be used to estimate the interstory drift ratio.
Objective: For a building, find the building layout and material type that will minimize structural weight and minimize building roof drift.
Variable Inputs: Number of Stories (story height), Member depths, Material Type/Strength, Bay Spacing (Number of Columns along building width/depth)
Fixed Inputs/Constants: Building Height, Building Width, Member widths, Material Density and Elastic Modulus for each Material Type Option, Applied lateral load
Geometry: I first created a grid of points based on the number of columns in each direction and the specified building height and width/depth. Then I created a series of lines in the x and y directions (neglecting the base layer). I also created a series of lines to act as my columns. Then I used Cuboid.ByLength to create solids from the midpoints of the lines I created. I obtained the volumes of all the elements and summed them together for later calculation of structural weight.
Outputs: I had an output of roof drift, which I calculated based on the stiffness of the structure, which I assumed was a shear/cantilever structure where the story deformations acted in series (1/Kbuilding = 1/K1+1/K2+…), and an applied lateral load of 200 kips. From the geometry, I gathered the volume and multiplied by the material density to obtain the structural weight. Each of the output values were given a watch node to set up for the generative study.
Step 3 - Generative Design Study Results
- The screenshot of the Scatterplot or Parallel Coordinates Graph illustrating the tradeoff that you chose to model and study.
- Provide a brief explanation of what’s being shown in the Scatterplot or Parallel Coordinates Graph and how the tradeoff being illustrated would impact the design decision. What would you do with this info?
The scatterplot and parallel coordinates graph illustrate the relationship between structural weight and roof drift for the inputs of Column/Beam Depth, number of stories, number of columns along the building, and material type (Steel, 3500psi Concrete, 5000psi Concrete, and Glulam). There is a clear inverse relationship between structural weight (kips) and roof drift (inches). Larger point sizes, representing a greater number of columns tend to lead to a lower roof drift. Additionally, stiffer materials (red) result in lower roof drift, but often result in higher structural weight. Buildings with fewer columns and smaller members are lighter, although they have a larger roof drift. With this knowledge, we are able to better determine which building configurations result in lightweight and a good lateral structural performance. For example, based on the information above, I’d likely avoid the glulam designs as although they have the lightest structures, they produce the largest roof drift.
- An image of your Dynamo Study Graph (showing all your nodes and the connecting logic) -- You can use the File > Export Workspace As Image... command in Dynamo to save a PNG image to upload with your posting.
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