The Pitch
Intended user: Structural designers who are making decisions regarding concrete mixes and reinforcement quantities
The need:
When choosing the size of concrete columns, engineers have to decide between using higher strength concrete, which has higher embodied carbon associated with it, or adding more reinforcing, which also has a negative impact on embodied carbon. When designing, safety should always be the priority, but it is important to understand the tradeoff in embodied carbon for the safety of our planet. There is a need for a tool that is able to determine the optimal combination of concrete strength and reinforcement ratio, that, without compromising strength, is able to minimize embodied carbon.
Inputs:
Number sliders | |
Input | Units |
Axial Load | kips |
Column height | ft |
Concrete Strength | psi |
Reinforcement Ratio | % |
Constants | |
GWP Value | lbCO2 eq |
Underlying logic:
Value | Formula | Code Source |
Column Area | A=P/(0.80*φ*(0.85·f'c·(1−ρ)+fy·ρ)) | ACI 318-19 |
Concrete Volume | Vc=A*h | |
Rebar Volume | Vs=A*ρ*h | |
Embodied Carbon | EC=GWP*m |
Outputs:
Output | Unit |
Column Size | inxin |
Concrete Carbon | lbCO2 eq |
Rebar Carbon | lbCO2 eq |
Total Carbon | lbCO2 eq |
Brief Overview:
This tool is a design assistant developed using Dynamo that helps structural engineers assess the embodied carbon tradeoffs when selecting concrete strength and reinforcement ratios in columns. Users are able to adjust the axial load, column height, concrete strength and reinforcement ratio, which will automatically output how the total embodied carbon and individual contribution changes as strength and reinforcement change.
This tool sizes the column for axial loads using equations from ACI 318-19, selects embodied carbon values based on concrete strength, and computes the embodied carbon of the concrete and the rebar. It then adds them together to find the total contribution of each material.
It is intended to be used by engineers who want to understand the embodied carbon tradeoffs between having larger, lower strength columns with more rebar, versus more slender, high strength columns with low reinforcement ratios.
Catchy Name: Column Print
Teaser Image:
Creativity Points:
In addition to being a design assistant tool that guides users through what to do if either the steel or the concrete is governing the embodied carbon, I created a generative design study that allows users to see the optimal embodied carbon for a specific column load. That is, it runs through all the possible concrete strength and reinforcement ratio combinations.
The graph above shows the generative design optimization performed for a 15ft column with a 1000 kip axial load applied to it. Several combinations of concrete strength to reinforcement ratio were evaluated, and the total embodied carbon was optimized. The results showed that in this case, using 6000psi concrete and a reinforcement ratio of 1% would yield the lowest embodied carbon.
Recording using the tool: https://drive.google.com/file/d/1LVh8S_FTZPYiYbc-v76yYl47W4Q8L5dx/view?usp=sharing