# Kevin O’Marah

Journal Entry For
Module 7 - Study Your Options
Created By
Kevin O'Marah
Property
Related to 120C/220C Students - Spring 2022 (1) (Related to Design Journal Entries | Winter 2022 (Linked Student))

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• Your Name as the Card title
• The link to your Module 7 folder in our Autodesk Construction Cloud project

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### Step 1 - Generative Design Framework

A very brief description of the design decisions from Step 1 following the Generative Design Framework.

• Design Decision 1: Material Cost
• Design Variables
• Variables
• Cost of the Roofing & Wall Materials
• Total Surface Area of Each
• Evaluators
• cost per area times the area
• Most Important Tradeoffs to Consider
• The cost will be a limiting factor primarily for other parameters that require more material such as lateral stiffness or the fundamental period
• Design Decision 2: Seismic Performance
• Design Variables
• Variables
• Building Height
• mid-height fraction
• building density
• Evaluators
• Evaluators
• Fundamental Period
• Building weight
• Most Important Tradeoffs to Consider
• A larger weight means greater seismic forces but a larger fundamental period means less accelerations during an earthquake
• Design Decision 3: Lateral Resistance
• Design Variables
• Variables
• Height
• Floor Area
• mid-height fraction
• number of sides
• Evaluators
• floor area*h*number of sides^mid height fraction
• Most Important Tradeoffs to Consider
• more lateral stiffness means better resistance to deflections under loads like wind but stiffness decreases the fundamental period.

### Step 2 - Generative Design Study

• My design included 4 inputs, 4 outputs, and three constants. The 4 inputs are the height of the building, mid-height fraction, the number of sides on the building, and the radius of the initial circle. The height is simply the total height of the building, the number of sides is the number of sides for the polygon at the floor and the roof, the radius is the radius of the circle used to create the geometry at the floor and roof before is turned into a polygon (effectively it’s the size of the polygon at the roof and floor), and the mid-height fraction is the fraction of the size of the circle at mid-height making it more slender at the middle.

Here the geometry is being created

Here the roof and walls are being isolated to calculate the different parameters for the out puts

Here three of the output parameters are being calculated. The stiffness is approximated by taking the ratio of the floor area to the height because it is assumed that more floor area will result in bigger or more columns. Then the stiffness is adjusted by multiplying by the number of sides raised to the power of the mid-height fraction. This is because in order to achieve a shape with more sides a column will be placed at each corner and since reducing the cross-section reduces the moment of inertia (which reduces the lateral stiffness) I decide to make the function exponential since moment of inertia has units of distance^4. For weight, I take the volume of the building multiplied by a constant value of the average density. The fundamental period is 2pi*sqrt( building weight/gravitational constant/lateral stiffness).

Here the total cost is being calculated by multiplying the cost per area of the floor or area by their respective areas and then being summed up for a total cost.

Here are the four outputs. The total cost will be minimized to not only reduce the total cost of the building but also to capture the different costs of the different building materials. Especially since some parameters are a function of the surface area of the roof and some include the entire volume of the building. The lateral stiffness will be maximized to reduce deflections from lateral loads such as wind, however, this is a trade-off with the fundamental period which decreases with stiffness. The overall weight of the building will be minimized to reduce the equivalent lateral forces that will be used for the design of the building. The fundamental period will be maximized to reduce accelerations during a seismic event. This will reduce the equivalent lateral forces that are used in design but also reducing accelerations is important for buildings such as hospitals where nonstructural damage plays a much bigger role. Greater accelerations means expensive equipment may fall over and break or patients may be thrown from their beds or fall over causing more injury.

### 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.

Here we see the fundamental period v material cost from my generative study. As we see the fundamental period generally increases with material cost but as shown from the size of the dots the number of sides helped significantly reduce the cost while maintaining a long period. The bigger dots indicate more sides

• 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?
• 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.

Input