Return to index: [Subject] [Thread] [Date] [Author]

Re: Work points

[Subject Prev][Subject Next][Thread Prev][Thread Next] Bob,

Just because you are designing for an Rw = 2.9, I wouldn't ignore the classic work points.  With an Rw = 2.9, you are still expecting some inelastic behavior to occur if the earthquake is large enough, granted with a higher Rw value the structure would go inelastic sooner.  Remember, we are only guessing as to how big the earthquake is going to be (energy release, duration, distance, site effects, etc.)  If you do move the work point down or up to the beam flange and or column flange you need to consider the secondary moment on the beam and/or column due to the eccentricity of the workpoint and axial forces going through the beam and or column.  These secondary moment may likely increase your beam and/or column member sizes.

Mike Cochran S.E.

In a message dated 3/12/2002 2:28:34 PM Pacific Standard Time, Bob(--nospam--at) writes:

I would like to get opinions on non building structures where bracing does
not fall on classic center of beams or columns. Structure is industrial
equipment support, 2 level.  Rw of 2.9 is used and used strength load cases
for concentric braced connections. The issue I need opinion is if the flange
of the beams is used for work point the weld lengths and plate sizes are
reduced. ($$$) When the allowable to load ratio for plate crippling and weld
is inspected it can vary from 5 to 60. Seems plenty strong to me. Each
framing level has fully braced plans. My thinking is that the classic
bracing detail provisions apply where Rw is higher do not really need to be
literally applied to non building system where bracing is fitted irregularly
and safety factor is high.

Robert M. Hanson,S.E.
Kappa Engineers
Carson, CA.
(310) 233-3800