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# RE: Floor vibration design

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Floor vibration design
• Date: Mon, 19 Nov 2001 12:51:02 -0700

```your equation has unit problems:
{m}{dx^2} + {c}{dx} + {x} = {fn}
x-displacement (ft)
fn-forcing function (lb)
it should be:

[m]{dx^2/dt^2)+[c]{dx/dt}+[k]{x}={fn}
where dx^2/dt^2 is acceleration, k is the stiffness matrix
and x are relative displacements

-----Original Message-----
From: Eric Green [mailto:egreen(--nospam--at)exponent.com]
Sent: November 19, 2001 11:40 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Floor vibration design

True, I guess what I should have said is that this works only for
discretized systems, while there are many excellent closed-form (nominally
exact) solutions for beams and floors. Consult something such as Roark &
Young. I suspect what the requirements really mean is the peak particle
velocity of the primary mode shape. Anybody know?

Eric Green
-----Original Message-----
From: Scott, William N. [mailto:William.Scott(--nospam--at)veco.com]
Sent: Monday, November 19, 2001 1:29 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Floor vibration design

Eric,

Actually, the equation is multi-degree with stated in matrix form.

{m}{dx^2} + {c}{dx} + {x} = {fn}

x is displacement, not initial displacement.

Bill

-----Original Message-----
From: Eric Green [mailto:egreen(--nospam--at)exponent.com]
Sent: Monday, November 19, 2001 10:06 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Floor vibration design

for a single degree of freedom system only. not many of those in structures.

Eric Green,

-----Original Message-----
From: Scott, William N. [mailto:William.Scott(--nospam--at)veco.com]
Sent: Friday, November 16, 2001 6:38 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Floor vibration design

the equation is

m*dx^2 + c*dx + x = fn

where m = mass
dx^2 = acceleration
c = damping
dx = velocity
x = initial displacement
fn = forcing function

Bill

-----Original Message-----
From: Mark Pemberton [mailto:Markp(--nospam--at)lbdg.com]
Sent: Friday, November 16, 2001 2:48 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Floor vibration design

I just do not see how to develop a force given only
a velocity.

Mark Pemberton, P.E.
Sacramento, CA

-----Original Message-----
From: dmorrow(--nospam--at)swensonsayfaget.com [mailto:dmorrow(--nospam--at)swensonsayfaget.com]
Sent: Friday, November 16, 2001 1:48 PM
To: seaint(--nospam--at)seaint.org
Subject: Floor vibration design

I believe it is the maximum velocity of the floor system calculated from the
maximum displacement of the floor system due to induced vibrations.  See
AISC's Steel Design Guide 11, "Floor Vibrations Due to Human Activity".

Dan Morrow
Swenson Say Fagét
2124 3rd Ave. Suite 100
Seattle, WA  98121
206-956-3745 (direct)
206-443-4870 (fax)

-----Original Message-----
Sent: Friday, November 16, 2001 12:00 AM
To: dmorrow(--nospam--at)swensonsayfaget.com
Subject: seaint Digest for 15 Nov 2001

From: Mark Pemberton <Markp(--nospam--at)lbdg.com>
To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
Subject: Floor vibration design

We have some plans that specify that the floor system shall
be designed for a "max velocity of 4000 micro-inches/sec".
What does this mean and how do you accomplish this?

Mark Pemberton, P.E.
Project Engineer
Lionakis Beaumont Design Group
1919 19th Street
Sacramento, CA 95814
Phone: (906) 558-1900, ext. 300
Fax: (916) 558-1925
www.lbdg.com

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