Are you a structural engineer or student who hates iterating through W-shapes for beam-column interaction? Do architects give you a headache pushing back on beam depth? InteraKt can help. It's a parametric beam-column solver that finds your options for you.
This is a tool meant to assist with early and intermediate phases of the design of steel structures, or for students when learning about beam-column interaction. Currently, AISC Manual interaction tables, hand iterations, and spreadsheets are used to do this, all of which evaluate a single trial section at a time and give the user no broader set of solutions. interaKt seeks to give the user a parametric sweep of valid solutions, ranked by a metric of their choosing.
Inputs
The user simply needs to input the required axial load, bending in the strong or weak axis, unbraced length for axial and bending, Cb factor (if necessary), and grade of steel. The user can then decide whether they want to sweep the solutions for optimum demand to capacity ratio (DCR), depth (for the architects), or weight. Additionally, there is an AISC database that is downloadable, which the user must create a unique path for in Interakt.
Outputs
Once all of these are decided, Interakt’s algorithm sweeps through the entire AISC database, running each compact W-shape through the Chapter E (compression), F (flexure), and H (combined interaction) checks of AISC 360. Every section that passes (meaning its demand-to-capacity ratio is at or below 1.0) is collected, ranked by the metric you chose, and the top five are displayed as live cross-sections in the Rhino viewport. Each section is color-coded by its DCR and labeled with its name, weight, depth, and utilization, so you can compare your options at a glance rather than flipping through tables. Alongside the top five, InteraKt generates a bar chart of the full feasible solution space, grouping every passing section by nominal depth. The height of each bar shows how many valid sections exist at that depth, and the color shows how light the lightest option in the section is. Therefore, the user can immediately see where you have plenty of design freedom and where you're cornered into choosing between one or two options. Together, the ranked sections answer "what should I use?" while the bar chart answers "what are all my options, and how much room do I have to move? Additionally, a panel showing the summary of results is available, listing how many sections passed out of the total swept, along with each top section's name, weight, depth, DCR, governing interaction equation (H1-1a or H1-1b), and governing limit state (compression, strong-axis flexure, or weak-axis flexure). This gives the full numerical breakdown behind the visual results.
How to use it
- Download the AISC database (provided as 2units_NathanCao_Module9_WshapeDatabase.csv) and place it somewhere on your machine. In Interakt, set the file path to point to it. (This is the one setup step. Interakt reads the section properties from this file.)
- Enter your demands. Use the sliders to input the required axial compression (Pu) and bending moments about the strong and weak axes (Mux, Muy).
- Enter the member lengths. Set the effective length for axial buckling about each axis (Lcx, Lcy) and the unbraced length for lateral-torsional buckling (Lb). Enter these as effective lengths (with your K factor already applied) since Interakt is a member checker and assumes you've determined effective length from your frame's bracing conditions.
- Set the secondary inputs. Choose the Cb factor (use 1.0 if you want to be conservative) and the steel grade (Fy).
- Pick your ranking metric. Toggle between weight (lightest first), DCR (most conservative first), or depth (shallowest first) depending on what you're optimizing for.
- Read the results. The top five valid sections appear as ranked, color-coded cross-sections, alongside a text summary listing how many sections passed and the governing limit state for each. The colored bar chart shows how many valid sections exist at each nominal depth and how light the best option is there. telling you where you have design freedom and where you're cornered. The full feasible set is also available, so you can see every section that works, not just the top five. Additionally, a panel showing the summary of results is available within the Grasshopper script. To view the bar plot, you may have to zoom in towards the origin to see it clearly, as it is not on the same scale as the beam columns.
Rendered Top 5 solutions based on metric of choice (depth)
Bar plot representing the entire solution space sorted by section depth and color-coded by the lightest section within the group of viable sections.
Summary Table within GH Script
DEMO VIDEO: Demo_Interakt.mp4
For the most part, I was able to implement everything I wanted to. There were a few extra things I was thinking about doing that I may not have included in the submission as I either ran out of time or did not think they were necessary.
P-M plots - I originally figured it would be cool to see the P-M curve and show where the interaction was occurring across the interaction space. With the number of solutions I have generated, this would look pretty messy. Also, it would be a pain to display in Grasshopper.
Pareto Front - A Pareto Front would basically just show what the bar plot is already showing, but in a more succinct way. For the purposes of what I am trying to achieve, the bar plot is effective and good enough.