Cal Osha Construction Safety Orders requires guard rails/posts to hold a minimum 200lb load in any direction without "failure" (key point here) It also refers to the use of "select lumber" as defined by the Safety Order which defines the lumber in the Westerns Woods Grading book with a value of 1500 psi material. Which without any factors would require the use of Douglas fir "Select" lumber. However if you test the lumber to failure ( which is specified in the Cal OSHA Construction Orders) would allow the use of a lower grade lumber. Testing to failure also allows for severl less nails as apposed to an engineered design. The Safety Orders do not address the allowable stresses for design.
So what does industry use for allowable values for nails/ screws/lumber, steel etc in the design of guardrails when they treat an allowble test to 200 lbs without failure as acceptable?