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RE: Vibration - Office Floor Guidelines

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To start with, contact your local steel fabricators in the area. They will be able to zero you in on the most economical structural system. You will have to add in the concrete costs yourself.

I do not know your project (bay spacing, live load, flr to flr height, etc.), but the use of 9/16 form deck and bar joists at 30" has not been the most economical system in most areas for many years. The composite decks and increase in joist spacing for bar joists of 5 or 6 ft is generally a more economical soution. It will make your joist girders work out better too. Once you increase the span to 5 or 6 ft, your system stiffness and mass will increase, but your cost per square foot will decrease. Your bouncy floor problem will take care of itself with a more economical structural syste.

Reducing piece count is generally considered more economical

Harold Sprague

From: "Rich Lewis" <seaint03(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: Vibration - Office Floor Guidelines
Date: Mon, 31 Jul 2006 08:30:22 -0500

I am designing an office building, something I used to do a lot in the past.
My typical design for buildings that do not require a fire rated floor
assembly is to use steel bar joists at about 30 inches on center, 9/16
corrugated form deck and a 3 inch total slab thickness.

I'm using AISC Design Guide 11, ""Floor Vibrations Due to Human Activity"
and having a hard time coming up with a system that satisfies the 0.5% g
value for office floor vibrations.  In my study girders seem to have a
greater influence than the joists.  My girder sizes were getting extremely

Are there typical slab thicknesses and joist spacing that others have found
that make it easier to meet the 0.5% g value? I know a lot of the vibration
influence has to due with the spans of the joists and girders.  Should
girders be having such a large impact on my design, or is it possible I'm
doing something wrong in my calculations?  Do others find that girders are
the main influence in vibration?  I was wondering if a different slab and
deck configuration, along with joist spacing is more conducive to reducing
the '%g' vibration value.

Thanks for your help.

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