Which types of structural framing systems and materials are most commonly used in the US for residences? For office buildings?
Timber for single family units, RCC/steel for apartments/office buildings. Residences typically carry lighter loads than offices/commercial buildings, so they don't require steel/concrete beams (cost).
Why do different teams of designers and subcontractors link and share their models during the design process?
Linking models enable collaborators to identify and address issues early on as the models are continually updated, before lots of time is spent on what could be a problematic part of the design. But collaborators might need to be more proactive about setting aside time to communicate the changes they make as the linked models are synchronized/updated with new changes.
What strategies can design teams use to find and avoid clashes prior to the start of construction?
At kickoff, design teams can start with general design rules as guidelines...for example each floor needs X amount of space for utilities etc. From there, collaborators can set up regular meetings/linked model synchronization timelines, or employ a coordinator role on the team.