Manufactured engineered supports have had safety factors of 5 to 6 in the past I have read. I understand in the 1990s the MSS safety factor was 4.0. In 2002, MSS reduced the safety factor to 3.5. All these safety factors are based on "ultimate" strength.

1. Why was the MSS safety factor decreased?

Another safety factor for supports is one relative to yield, which I believe is about half that of ultimate.

2. When modeling existing systems, when do analysts look or measure for plastic deformation of restraints - anytime the calculated loads in a preliminary model exceed the listing, or do analysts routinely have all restraints checked before model development?