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RE: controlling vibration on existing steel joist floor

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For the most part reducing the span of an open web joist is typically not a problem (if you provide the new support point at the top chord) particularly if the web members are "bars".  If the webs are angles then you will have to be careful that the revised shear envelope does not place webs that were sized for tension only in compression. You will also need to carefully detail the top chord bearing shoe at the new support point which should include the addition of new web reinforcing angles each side of the support to properly engage the last bottom chord panel point with new top chord panel point.
Matthew Stuart


From: Pedro Khouri [mailto:khouri_p(--nospam--at)]
Sent: Wed 1/5/2005 5:21 PM
To: seaint(--nospam--at)
Subject: controlling vibration on existing steel joist floor

(Sory if a repost)

Does any one have recommendation on controlling vibration on existing steel
joist floor.

The floor is supporting pool tables in a open room with no partitions.

The floor system is concrete (do not know the thickness) over metal deck
supported by 24" deep joist (Vulcraft 11 J 2 per attached tag) spaced at 24"
O.C. with a clear span of approximately 48 ft.

The contractor is subjecting the addition of a mid span support with some
posts to the room bellow to reduce the joist's span. I am concern that the
added support will negatively affect the joist by inducing negative moments
at mid span although the joist members (top / bottom chord & web members)
appear to be constant thru the length of the joist.

Any comments will be appreciate.

Thank you,

Pedro Khouri, P.E.

Coral Springs, FL

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