Margaret Gereghty

• Structural Material Sustainability v.s. Cost
• Design Variables
• Material type
• Level of prefabrication
• Local material availability
• Cost per unit weight
• Typical member size
• Evaluators
• Embodied carbon
• Structural performance
• Construction schedule impacts
• Construction cost
• Most Important Tradeoffs to Consider
• Lower-carbon materials may increase upfront costs.
• Lightweight systems can reduce foundation demands but may require additional vibration control or fire protection.
• Prefabrication can reduce waste and improve construction speed but may increase transportation costs.
• More sustainable materials may be weaker and need more structural elements than less sustainable materials
• Sustainable materials may have longer lead times or higher costs depending on regional availability.
• Flexibility v.s. Structural Efficiency
• Design Variables
• Structural bay spacing
• Floor system type and span capability
• Column spacing and grid layout
• Beam and slab depth
• Occupancy and loading requirements
• Evaluators
• Floor-to-floor height
• Total structural material volume
• Architectural flexibility and usable space
• Most Important Tradeoffs to Consider
• Larger spans reduce the number of columns but require heavier structural members.
• Smaller bays reduce member sizes but increase column and foundation quantities.
• Deeper structural systems improve span efficiency but can impact building height and MEP coordination.
• Optimized structural grids balance material efficiency with functional and architectural flexibility.
• Lateral Force Resisting System v.s Cost
• Design Variables
• Governing lateral forces (wind, seismic, etc.)
• Geographic location and hazard level
• Gravity framing system
• Building height and fundamental period
• Evaluators
• Interstory drift ratio (IDR)
• Impact on architectural space planning
• Construction cost
• Most Important Tradeoffs to Consider
• Stiffer systems reduce drift but often increase material usage and cost.
• Braced frames are cost-effective but can limit architectural openness and flexibility.
• Moment frames provide greater spatial flexibility but require more complex and expensive connections.
• Shear walls improve structural efficiency but reduce planning adaptability and usable floor area.
• Stiffer systems may reduce nonstructural damage during extreme events, though they can increase maintenance and construction costs.

Study Outline and Goals

I wanted to study the interaction between architecture and structure, so I chose to evaluate the “Flexibility vs. Structural Efficiency” metric outlined in Step 1. To do this, I first simplified the problem space into a set of controllable inputs and measurable outputs.

From my structural background, I know that beam depth and column dimensions are strongly correlated with bay size. To establish this relationship, I focused on a typical structural material (concrete) and used common engineering rules of thumb relating span length to member depth for beams and columns. This made bay size the first primary input variable.

For the second input, I wanted to explore how structural span impacts architectural quality and spatial experience, so I introduced level-to-level height as a variable. While larger spans and taller floor heights may improve flexibility and architectural openness, they can also increase structural demands and material use. These two variables therefore create a useful tension between architectural flexibility and structural efficiency.

I chose to use three evaluators to really test the logic of the study, the structural system volume, architectural volume (under the structural system) and the efficiency of use between structural volume and architectural volume.

Generative Design Framework

• Design Variables
• Span Length
• Level to Level Height
• Structural Material (Span to Depth Ratios for Columns and Beams)
• Derived Quantities
• Structural Depth
• Beam Volume
• Column Volume
• Usable Interior Height
• Evaluators
• Structural System Volume
• Architectural Volume (Floor-to-Floor Height x Bay Floor Area)
• Efficiency (Arch Volume/Structural Volume)
• Most Important Tradeoffs to Consider
• Larger bay sizes means more uninterrupted (no columns) architectural volume but also more structural volume.
• Larger bays means deeper elements which also means smaller architectural volume beneath the structural system.
• Higher level to level height means more structural volume but also more architectural volume (a smaller increase in structural compared to increasing bay size).

Study Results

I chose to run an optimization design study with the Level to Level height and bay size as the inputs to change and Concrete Volume as the output to minimize and Architectural Volume and efficiency as outputs to maximize. The results of the study can be seen in the following images.

The scatterplots and parallel coordinates graph illustrate how the design inputs, bay size and level-to-level height, affect the outputs of concrete volume, architectural volume, and structural efficiency in this optimization study. In the scatterplots, smaller bay sizes tend to correspond with higher structural efficiency because they require less concrete while still achieving similar architectural volume. The results also suggest that greater level-to-level heights improve efficiency, likely because the increase in usable architectural volume is proportionally greater than the increase in structural material.

The parallel coordinates graph helps visualize these relationships simultaneously, making it easier to identify combinations of inputs that produce lower concrete volumes and higher efficiencies. By tracing the lines across variables, it becomes possible to see which design options consistently perform better across multiple criteria rather than optimizing only one parameter at a time.

The tradeoff being illustrated is between structural/material efficiency and architectural functionality. Smaller bays may reduce concrete use and improve efficiency, but they can also introduce more columns and reduce openness and flexibility in the floor plan. Larger bays, while less efficient structurally, may provide more desirable open spaces and architectural freedom. Similarly, taller floor-to-floor heights may improve efficiency metrics and spatial quality, but they could also increase façade, MEP, and circulation costs.

It is important to note that this study evaluates only a single bay condition. To better represent real-world building behavior, a next step would be to normalize the study by calculating how many bays of each size would be required to create the same overall floor plate area. Comparing the total concrete volume across equivalent floor plates would provide a more accurate understanding of the true material impact of different bay sizes and lead to more informed design decisions.

Dynamo Graph Logic

The dynamo logic was made using cuboids to represent the beams and column elements, then the volumes of the total bay was extracted and compared with the volume under the elements (the architectural volume).