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# Re: Steel floor plate

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: Steel floor plate
• From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
• Date: Mon, 12 Mar 2007 10:45:08 -0500

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On Mar 12, 2007, at 9:31 AM, <William.Sherman(--nospam--at)CH2M.com> wrote:

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Actually my application "is" an industrial application - the plate will be used at a platform to be used regularly to access equipment.  I don't want the floor plate to feel excessively "bouncy", so I am trying to establish the criteria to use for deflection.
I don't do buildings (as I've said many times) but I do know some stuff about dynamics. The first part of the 'feel' issue is frequency. Something only feels bouncy if you can feel it, so if you keep the frequency above what people can sense in their middle ears, a floor won't feel bouncy. You can do some calculations to estimate the floor frequency with fairly simple beam formulas from your dynamics text and get a handle on what you have. If I were to guess, you'd want something in excess of 5 Hz. I don't have a scientific basis for that beyond knowing that people can hear frequencies above 20 Hz, so if balance organs could sense that, people would get seasick at concerts…
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One of the problems you come into real quick is that it's hard to stiffen a framework without adding mass. Frequency goes as the square root of the ratio of stiffness to mass, so it's easy to end up fighting yourself. The square root variation means that even if you do increase the stiffness by some percentage the frequency only goes up by half of the same percentage. It gets very tiresome unless you can decrease the span or move the mass around so it's closer to the supports.
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There's
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
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.......................................| John Sedgwick, Spotsylvania 1864)
```http://www.skypoint.com/~chrisw/

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