Which structural framing systems and materials are most commonly used in the United States for residences? For office buildings?
In the US, most houses and low-rise apartments use wood light-frame construction. Mid-rise apartments often use wood framing over a one- or two-story concrete podium. Office buildings mostly use steel frames with composite metal decks, although concrete is more common on the West Coast and in some dense cities. These systems are popular mainly because of cost and construction speed. Wood framing is relatively cheap, skilled labor is widely available, and building codes allow it up to about five or six stories. Office buildings need longer spans and flexible floor layouts, which makes steel a good choice.
I chose concrete because my building has seven residential floors above L1, which is beyond what conventional wood framing can handle. PT slabs also help keep the floor system relatively thin, which is important with a 10 ft floor-to-floor height. However, concrete costs more and takes longer to build than wood. The band beams also reduce the ceiling height inside the units, and any future slab penetrations need to avoid the PT tendons.
You sized members by judgment rather than analysis.
Design teams link and share models rather than working in one file.
Not every clash is a problem.
My rule was pretty simple. If resolving a clash requires a design change, I consider it an issue. If it is just a duplicate element in another model, or if the overlap is intentional, I don't consider it an issue. Most of the 2,183 clashes I found were not actual issues. For example, structural slabs overlapped with architectural floors, and columns were located inside walls, which was expected. The real issues were band beams interfering with unit ceilings and the elevator model not matching the pit dimensions.
On a real project, the BIM coordinator would run the clash detection, but I don't think the coordinator should close clashes alone. The discipline responsible for the element should review and close the clash. If two disciplines are involved, both leads should agree on the solution during a coordination meeting. If the solution requires a design change, such as lowering a ceiling, it should go back to the architect because the architect is responsible for coordinating the overall design.
Your beam depths just constrained next week's ductwork.
The tightest area is the L3 parking level in the podium. The L4 garden girders are 36 in. deep, so with a 10 ft floor-to-floor height, only about 7 ft remains below the girders. This leaves almost no space for ducts or sprinklers. The tower corridors are also tight because the coupling beams and tie beam cross the corridor where the main duct would normally run.
To create more space, I could increase the podium floor-to-floor height, use a PT flat plate system without beams, or add some columns to reduce the spans. However, each option has its own disadvantages in terms of building height, cost, or floor layout. I think the structural engineer should have coordinated with the mechanical engineer before deciding on the beam sizes and spans. Beam depth directly affects where ducts can run, and it is much easier to address these conflicts during design than to fix them later.