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Re: IRREG - Plan Irregularities

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>Our plan is basically an L shape, with one leg
>being a 180' by 180' square.  The other leg is
>about 90' wide and sticks out 105' from the big
>square.  Current plans call for the moment frames
>to be on the four edges of the big square.
>Do we need to do a dynamic analysis of the

Three comments:
1. To cantilever a 90ft wide diaphragm 105 ft is not a good configuration
2. You should do a dynamic analysis because of the large irregularity
between the center of mass and the center of rigidity of the SMRF.
3. You still have a reentrant corner problem because the mass associated
with the "cantilever section" could be moving opposite to the direction of
the "big square".

>We're looking at a nominally 7 story structure
>that is to be steel SMRF (using a proprietary
>joint system).    We have a few questions on what
>kind of special provisions we should be looking at
>(suppose for the moment, that we don't have any
>vertical irregularities per 16-L.)

>Do we need to follow 1631.2.9 Items 6 and 7?    If
>you look at Table 16-M Item 2 it says:
>Plan configurations of a structure AND its lateral
>force-resisting system contain reentrant
>Now, if you look at a plan of the building, we
>have a reentrant corner, however, if you look at
>just the plan of our frames, we have a nice
>squarish configuration (and none of the frame are
>located out on the projecting wing).
>Stan Johnson, PE
>NEWS FLASH - Disaster is the jolly rancher welding
>program. :o(  We had fabricated (by pressure
>setting) some full size joints for cyclic testing,
>and had put the first one on the test rig, but it
>was getting late so we retired for the night.
>When we came back in the next morning, all of our
>specimens were swarming with ants.  We wiped them
>away and found that they had eaten through almost
>a quarter inch of weld material!  Looks like we're

           Harry Jones II, S.E.
          140 42nd Ave
           San Mateo, Ca. 94403
           Ph: 415-725-7016   Pager: 415-335-0699
           Email: hjii(--nospam--at)