Steven Song - Module 8 - Part 1

Journal Entry For
Module 9 - Make Your Pitch
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Structural Bay Size Optimizer

A generative design assistant for architects and engineers during schematic design

Intended users

Users: Structural engineers, architects, sustainability consultants

Need you’re trying to provide a solution or support for

What problems do they face?

  • Designers often guess initial bay spacing and floor heights using rules of thumb.
  • These assumptions significantly influence structural spans, system weight, and mechanical clearances.
  • Carbon and cost estimates are rarely quantified at this stage, even though early decisions lock in long-term impacts.

Need: Early design decisions like bay width have major implications on structural efficiency, material use, and embodied carbon.

Inputs

Variable Input Name
Description
Number of Bays X
User-selected horizontal and vertical grid spacing
Variable
Floor-to-floor height
Impacts story height
Variable
Structural system type
(e.g., steel moment frame, concrete beam-slab)
Variable
Building footprint
Total length
Variable
Point Load (P)
Horizontal or vertical force at any node (user-defined)
Variable
Uniform Line Load (w)
Applied in Z-direction (gravity); distributed load per bay
Constant
Material database
Includes density, strength, and embodied carbon (kg CO₂e/m3)
Constant

Underlying logic of the model you’ll implement

  • 2D Frame Generation:
    • Create a single-story 2D frame in Revit based on bay width and height inputs.
    • Generate nodes and members with pinned supports at the base.
  • Loading and Statics:
    • Apply user-specified point load (P) at any node (horizontal or vertical).
    • Apply uniform user specified + material-related gravity line load (w) on all beams.
    • Solve for member axial forces, shears, and bending moments using statics.
  • Member Design Check:
    • For each beam and column, compute Demand/Capacity (D/C) ratio
      1. Where:

      2. Demand: internal axial/shear/moment due to applied loads
      3. Capacity: based on material strength and cross-section
  • Performance Metrics:
    • Total structural weight: computed from section areas and material density
    • Embodied carbon: computed from material volume × density × CO₂e/kg
    • Demand/Capacity (D/C)
  • Generative Optimization Logic:
    • Multi-objective evaluation based on:
      • Minimized embodied carbon
      • Minimized material weight
      • Maximized D/C ratios (≤ 1, no overloads)
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Outputs

Type
Output Description
Visual (Revit)
2D framing layout auto-generated based on chosen bay size
Weight
Table of material takeoffs (lb)
Sustainability
Total embodied carbon summary (lb CO₂e)
Strength
Demand Capacity ratio per element
Exportable
CSV or Excel of assumptions and performance metrics