Step 1 - Generative Design Framework
- Design Decision 1: Cantilever Retaining Wall Geometry Optimization
- Design Variables
- Toe Length (ft)
- Heel Length (ft)
- Stem Thickness (ft)
- Evaluators
- Total Concrete Volume per linear foot (Minimize)
- Factor of Safety against Overturning (Maximize)
- Factor of Safety against Sliding (Maximize)
- Most Important Tradeoffs to Consider
- Extending the heel length utilizes the weight of the retained soil to prevent overturning without adding extra concrete, but requires significantly more site excavation. Widening the toe prevents sliding and bearing failure, but adds pure concrete dead weight, driving up material costs and embodied carbon.
- Design Decision 2: Office Building Column Grid & Slab Thickness
- Design Variables
- Column spacing in the X-direction (ft)
- Column spacing in the Y-direction (ft)
- Concrete slab thickness (in)
- Evaluators
- Total Concrete Volume (Minimize)
- Maximum Slab Deflection (Minimize)
- Total Number of Columns (Minimize)
- Most Important Tradeoffs to Consider
- Pushing columns further apart creates highly desirable, open architectural layouts by minimizing the column count. However, to prevent the slab from exceeding deflection limits over these longer spans, the slab thickness must be drastically increased, which heavily drives up the total concrete volume and project cost.
- Design Decision 3: High-Rise Massing and Wind Sail Reduction
- Design Variables
- Building base width (ft)
- Top taper percentage (%)
- Corner chamfer/radius size (ft)
- Evaluators
- Total Wind Surface Area (Minimize)
- Total Leasable Floor Area (Maximize)
- Structural Center of Mass Height (Minimize)
- Most Important Tradeoffs to Consider
- Tapering the building as it rises and heavily chamfering the corners drastically reduces the wind surface area, saving a fortune in lateral structural steel. However, every square foot shaved off the building envelope is a square foot of prime, high-altitude real estate that cannot be leased out.
Step 2 - Generative Design Study
Detailed Description: For this study, I chose to model the Cantilever Retaining Wall Geometry. The goal is to determine the optimal cross-sectional dimensions of a concrete cantilever retaining wall that minimizes material usage while safely maintaining strict structural stability requirements (Factor of Safety of 1.5 or greater).
Generative Design Framework Setup:
- Objective: Minimize the total concrete volume of the retaining wall while maximizing (or constraining > 1.5) the Factor of Safety against sliding and overturning.
- Model: A parametric 3D Dynamo model that generates a 1-foot unit strip of the retaining wall, alongside the retained soil and toe water blocks. The graph uses a physics engine code block to calculate static equilibrium and includes conditional logic to automatically deploy a concrete shear key if the initial FOS against sliding drops below 1.5.
- Design Variables:
- Toe Length (1.0 ft to 5.0 ft)
- Heel Length (2.0 ft to 8.0 ft)
- Stem Thickness (1.0 ft to 3.0 ft)
- Constants: - Total Height (15 ft)
- Base Thickness (1.5 ft)
- Soil Unit Weight (120 pcf)
- Concrete Unit Weight (150 pcf)
- Active Earth Pressure Coefficient (0.33)
- Base Friction Coefficient (0.5)
- Evaluators:
- Total Concrete Volume (Minimize)
- FOS Overturning (Maximize)
- FOS Sliding (Maximize)
Step 3 - Generative Design Study Results
Explanation of the Scatterplot and Tradeoff Impact: The scatterplot illustrates the direct tension between material efficiency (Concrete Volume on the X-axis) and structural stability (Factor of Safety on the Y-axis). The cluster of points in the bottom-left corner represents highly efficient designs that ultimately fail the safety checks, while the top-right shows over-engineered, massive walls. By filtering out any options where the FOS is less than 1.5, the "Pareto front" reveals the optimal geometries at the bottom edge of the safe zone. This data allows a structural engineer to confidently select the absolute minimum wall profile that satisfies safety codes, knowing exactly how much extra safety margin each additional cubic yard of concrete buys.
