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RE: Subject: Calculations of Base Shear

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Subject: Calculations of Base Shear
• From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
• Date: Mon, 24 Feb 2003 21:26:00 -0500

```I agree with Mark's approach. I usually use the full wall weights in the
diaphragm design for simplification; but I recently separated the parallel
and perpendicular wall weights according to seismic direction for a design
with tall, fully grouted 12-inch masonry walls. In any case, the total
weight of walls must be accounted for in calculating total base shear.

William C. Sherman, PE
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

> -----Original Message-----
> From: Mark Gilligan [mailto:MarkKGilligan(--nospam--at)compuserve.com]
> Sent: Monday, February 24, 2003 3:10 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Subject: Calculations of Base Shear
>
>
> Bobby
>
> There are two approaches:
>
> In both approaches you must consider all building weight above that is
> tributary to the level above the found floor when calculating
> the total
> base shear.
>
> When distributing the forces to the shear walls you can
> ignore the weight
> of the shear walls at that level when the shear walls are
> parallel to the
> direction of the earthquake motion.  This ignored weight
> times the proper
> coefficient should then be applied directly to the shear
> wall.   This can
> be worthwhile if you have a particularly heavy wall or when
> you want the
> absolute minimum force in the diaphragm.  This is more
> difficult when you
> are using a computer program to analyze the structure as
> opposed to a hand
> analysis.
>
> The more common approach is to assume all of the wall weight
> tributary to
> the diaphragm is lumped together.  This is quickier and less prone to
> mistakes.
>
> Mark Gilligan

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