Which types of structural framing systems and materials are most commonly used in the US for residences? For office buildings?
For office and commercial buildings, steel is commonly used. For single family residential buildings wood is mainly used. The main reason for this discrepancy is due to building size and fire hazards. Steel is stronger so therefore it used in larger buildings, it also has a high fire resistance and once a building reaches a certain height (or is used for a specific occupancy) it becomes a mandatory structural material.
Why do different teams of designers and subcontractors link and share their models during the design process?
What are the advantages of linking models?
Linking models helps facilitate collaboration. If you're an architect with knowledge of structures, it's much easier to provide the architectural design to a contractor/structural engineer to link to their structural plan.
Are there any disadvantages to linking models?
Linking models can cause discrepancies if they are loaded incorrectly or use different units. Clashes can also be very common.
At what point in the project development process should design coordination start?
I don't think there is ever a phase too early for coordination. Having someone of a different discipline within the room while you discuss preliminary designs can help to create a more integrated process and interdisciplinary solution.