Which structural framing systems and materials are most commonly used in the United States for residences? For office buildings?
◦ What factors explain why those dominate?
For residences, light-frame wood systems dominate because they are cheap and easy to build. Because residential buildings have repetitive walls, wood is more efficient.
For offices, structural steel dominate mid- to high-rise offices. Steel is easier to implement and cheaper than concrete, which makes it favourable. Steel is also very flexible, which is good for offices as all floors are different and need adaptable layouts.
◦ Why did you choose your system, and what did it cost you?
I chose a concrete frame system for my commercial floor because it can support high loads with long-span spaces. It cost me embodied carbon, as concrete has high upfront carbon emissions. It is also more expensive, and takes more time to construct.
For my residential floors, I chose a wood frame system because the structural load is low and the walls are repetitive. However, it limits supportable structural loads in the apartments.
You sized members by judgment rather than analysis.
◦ What did you base your first guess on?
I based my first estimate on what typical columns and members are used for residential/commercial buildings. I typed the question into the search engine and looked at whatever results showed up to base my guess.
◦ Why is it safer to guess large and shrink than to guess small and grow?
It’s safer to start larger because there is no risk in having more structural stability. If you guess too small, the building can be unsafe, and it can be hard to undo. As well, if you design the building around a smaller size than what is actually required, there may not be enough space to accommodate a larger size. Therefore, it is safer and easier to make space for a larger member and then adjust it afterwards.
◦ At what point in a real project does the engineer take over from the guess?
After the architectural drawing is complete, an engineer should take over to ensure that the member sizes are actually safe for humans. Engineers should be involved in the project once the initial conceptual design is complete, as structural limitations will dictate architectural design as well.
Design teams link and share models rather than working in one file.
◦ What are the advantages of linking?
◦ What errors does linking make possible that a single model would not?
◦ Why is getting shared coordinates right at the start so much cheaper than fixing it later?
Not every clash is a problem.
◦ On what basis did you classify a clash as an issue versus not an issue?
Certain clashes existed because the structural and architectural models were separate. For example, in the structural model, we had to create walls for the elevator and mechanical room shaft. However, I already had existing walls for the shaft in the architectural drawing, and thus the two walls ended up overlapping and causing a clash. However, in reality, the two walls are the same, and thus will not interfere with each other, and thus I classified it as not an issue. When the class was between two items that did not exist on both models, I classified it as an issue because it will cause issues when the models overlap.
◦ Who should have authority to close a clash on a real project?
The structural engineer should have authority to close a clash because structural safety depends on the fact that there are no overlapping elements. If two elements are overlapping, and one is structural and the other is architectural, and the structural element ends up getting removed as a result, that poses a safety hazard to the project. Thus, the structural engineer must ensure that the structural elements are in place before clashes get closed.
Your beam depths just constrained next week's ductwork.
◦ Where in your building is the ceiling plenum now tightest?
◦ What would you give up to get it back?
◦ Should the structural engineer have consulted the mechanical engineer before setting spans?