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Re: Questions about Residential design and 1997 UBC

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Thanks to Ralph and Dennis for their support of my realistic "design" approach
to engineering.

When one considers that our seismic load on the building is based on highly
accurate coefficients such as Rw (Is it 6 for a steel frame? Is it 8?  Is it
12?  Why not 7.25?  Does the frame know if it's ordinary or special?) and Z
and I ("We'd better chuck in an extra factor of safety of 50% - after all it
is a hospital.), we shouldn't get too wrapped up in the precision of the
analysis that the computer allows us to pursue.  Of course the same gross
assumptions also apply to the loading for vertical design.  Why is assembly
live loading 100 psf, why not 80, why not 92?

All told, for design we always have VERY rough numbers going in.  We should be
careful not to get too caught up in the analysis and modeling hype of the
results. It's important not to lose sight of the big picture and the desire to
design structurally safe and properly performing buildings.

Bruce Resnick, SE
Parker Resnick Str. Eng.