# Re: Seismic Joint Size

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: Seismic Joint Size
• Date: Thu, 28 Mar 2002 14:55:31 -0800
```A good discussion of this is in "Elements of Earthquake Engineering and
structural dynamics" by A. Filiatrault page 261.

regards,

Celso O. Mendoza, P. Eng.
----- Original Message -----
From: "Peter Griem" <griem(--nospam--at)slamcoll.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, March 28, 2002 9:44 AM
Subject: Seismic Joint Size

> I interpret the building codes to read that the seismic joint between two
> buildings must be sized by:
> 1. taking the elastic deflection calculated for each building (say by RAM,
> 2. multiplying that value for each building by the appropriate Cd factor
of
> the lateral system (to account for additional plastic deflection)
> 3. adding those amplified deflection values for each building together (so
> that if the buildings move toward each other in an earthquake they don't
> crash into each other)
>
> First question - do you agree that that is the way the code READS?  Second
> question - do you agree that is the INTENT of the code?  Third question -
Do
> you size seismic joints this way?
>
> Here's the problem - take a building categorized in a lower Seismic Hazard
> Exposure Group, e.g. SHEG I in the BOCA or IBC.  The allowable story drift
> (inc. Cd) = .020hsx.  For a four story building at 12' per story, the
> allowable deflection at the 3rd floor would be (3)x12'x12"/'x.020=8.6in.
> Say the design shows that two adjacent MF bldg are limited to 75% of that
> value - you need a seismic joint between them of .75x8.6x2= 13 in.  A 13"
jt
> at the third story of a building.  Try to explain to the architect -
> especially in a low/moderate seismic zone.
>
> How do you or others you know treat this issue.  I would especially like
to
> know how this is treated on the west coast.  What is the largest
> manufactured seismic joint that can be found to bridge a corridor?
>
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