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RE: Cranes and earthquake loads

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Gudrun,

I assume that you are talking about an overhead electric bridge crane.  The
short answer is yes you need to design for earthquake loading.  Generally
the seismic load is calculated based on the crane dead load without the
picked load.  It is generally assumed that if there is any hook extension at
all, the load is essentially isolated because the wire rope can not transfer
a lateral seismic load.

If the duty cycle of the crane indicates frequent use, you may consider the
combination of the maximum gravity load with the rated picked load occurring
at the same time of the lateral seismic load (calculated without regard to
the picked load).

The applied seismic load due to the crane dead load is applied similar to
the lateral and longitudinal crane impact loads, but not at the same time.
The seismic load may or may not govern the lateral design depending on local
seismicity and the magnitude of the picked load (the picked load will
determine lateral impact load).

Regards,
Harold Sprague
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Gudrun Olafsdottir [mailto:gudrun(--nospam--at)hnit.is]
Sent: Thursday, October 01, 1998 3:00 AM
To: seaint(--nospam--at)seaint.org
Subject: Cranes and earthquake loads


Here goes my first question to the list:

I have been asked whether a crane in a steel-frame building
we have been designing needs to be designed for earthquake
loads.  I can't find anything about cranes in our earthquake
code so I was wondering what is done elsewhere and also if
anyone has had any experience with this. 

Thanks in advance for any information!

Gudrun Olafsdottir

Hnit Consulting Engineers Ltd.
Reykjavik, Iceland