Parametric Concrete Column Interaction Curve

This project looks to create a parametric tool to calculate and plot the moment - axial force interaction curve for concrete column sections.

 
 
 
 

Overview

In Spring 2021, I was an Undergraduate Researcher in the Digital Structures Group, and for my semester project I created a parametric script to calculate and diagram the moment-axial force interaction curve for concrete column sections. The script works in real time, therefore, as the section changes that calculations and diagrams also change.

Project Members

  • Nebyu Haile

Programs + Tools used

  • Rhinoceros 3D

  • Grasshopper

 

Goal

The goal for the project was to make a grasshopper script that can calculate and plot a 7 point interaction curve for dynamically changing column section in real time.

What is a column interaction curve?

Any column can fail both in bending (moment) or in crushing (axial force), oftentimes it is a combination of these two that leads to a failure of a column. A column interaction curve is a curve that, for a given column section design, outlines all the combinations of moment and axial force for which the section will fail and for which the section will not fail. 

Sample Column Interaction Curve - Sky Civ

In the diagram above any point (combination of moment and axial force) inside the curve is a safe combination and any point outside is a failure combination. The dashed line in the figure represents the change between ductile failure and crushing failure. During crushing failure the compressive forces dominate and the column fails suddenly, during ductile failure the section bending forces dominate and the column fails over time.

Approach

For the calculation of the interaction curve the methods provided by ACI 318-14 were used.

 

Demo of Script

Bellow is a video demo of the script in action. Note there is a slight error at time 15:30; the ductile failure is any point in the red shaded area not any point below the balance point.

 
 

Moving Forward

The hope is that moving forward this script can be paired with other work the Digital Structures Group is doing to create a grasshopper plugin that can optimize the structural system of entire buildings for embodied carbon, embodied energy, and other metrics.

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