Which types of structural framing systems and materials are most commonly used in the US for residences? For office buildings?

What factors determine why these are the most used materials?

When constructing residential projects in the US, the most commonly used structural framing system is platform framing and the most commonly used material is wood because it is both cost-effective and easily attainable. When constructing commercial office buildings, structural steel is the most commonly used material due to its versatility. Most office spaces utilize a metal stud wall framing system as it bears the weight most effectively. These decisions are often determined by the expected function of the structure, the weight it will need to bear, the location of the project, available resources, and cost restraints, as well as a slew of other factors that may arise on a case by case basis.

Why do different teams of designers and subcontractors link and share their models during the design process? 

What are the advantages of linking models?

Are there any disadvantages to linking models?

How do you think design coordination was done before we started using digital models? 

What advantages does doing this coordination digitally have over previous methods?

Prior to digitization, I imagine design coordination would have been a much more tedious process in which numerous sheets would have had to be created, and then overlaid, to examine the correlations between each emphasized element. Architectural models would have been created individually and separately from structural models making this process more prone to mistakes and errors. Doing this coordination digitally allows all varying forms of a model to be created simultaneously, atop the other using numerous layers, making the entire process much more efficient and accessible for all members of the design team.

What strategies can design teams use to find and avoid clashes prior to the start of construction? 

What can be done besides sharing the models digitally?

At what point in the project development process should design coordination start? 

Is it ever too early?

I believe design coordination should begin near the very beginning of the design process as it allows all members of the team, coming from different disciplines, to be included from the start. This allows for all members to essentially sign off their approval at every stage in the design process, eliminating the chance for any problems to arise at a later stage in the creative process.