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RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS

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Thanks Harold,

The thing about UBC'97 not being the most appropriate code for
calculating silos is exactly what I told our client but he would not
listen. So I am stuck with this code.

The discussion now is wether or not to use section 1632.

However trying to keep the wall-thicknesses of the silos within
realistic limits, I proposed to apply the Veletsos, Younan and
Bandyopadhyay-report (Dynamics of solid-containing tanks, prepared for
the department of energy, Washington, D.C.).
This report allows for a part of the horizontal force to be transferred
to the bottom (in our case the cone-cylinderjunction of the silo)
through intergranular friction.
For those who are interested in this report, it can be downloaded here :
http://www.osti.gov/bridge/purl.cover.jsp?purl=/453784-sUxqbN/webviewabl
e/

This report also formed the base for parts of the new Eurocode 8 Part 4
(Design of structures for earthquake resistance - Silos, tanks and
pipelines).

If any-one has experience with this method of design please let me know.

Kind regards

Stefan Reumers

-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
Sent: woensdag 15 februari 2006 20:31
To: seaint(--nospam--at)seaint.org
Subject: RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS

It sounds like this is an attempt to use importance factors and the 1997
UBC 
to achieve a perceived higher performance.  I would suggest that you use
a 
more up to date code like the ASCE 7-05 and perform a more sophisticated

analysis.  Conservatism on loads does not necessarily buy you better 
performance.

Applicability of the UBC 97 to properly design granular silos is a
reach.  
There were some adjustments made in the NEHRP that have been reflected
in 
the ASCE 7-05.  I would urge you to look at the ASCE 7-05 section 15.3.1
and 
15.3.2 which had granular silos in mind when it was created.  It was in
the 
ASCE 7-02 as well.

Further, there has been coordination between nonstructural components
and 
nonbuilding structures in the NEHRP / ASCE / IBC process to try to
account 
for this as much as possible.  Not much was included in the UBC 97.
This 
was in the early days of the nonbuilding structures effort.

I would look at the relative stiffnesses of the aluminum silos and the 
concrete support structure.  I would also treat the contained product as

just an impulsive mass.  We have looked at the potential of a convective

component but there is not enough data.

Regards,
Harold Sprague

>
>-----Original Message-----
>From: Stefan Reumers [mailto:Reumers.S(--nospam--at)ellimetal.com]
>Sent: Wednesday, February 15, 2006 6:58 AM
>To: seaint(--nospam--at)seaint.org
>Subject: UBC 97 - SEISMIC DESIGN GRANULAR SILOS
>
>
>
>I have to design 24 aluminium silos 720 m3 each for the storage of
granular
>Polyethyleen.
>
>These silos are mounted on a 20 m high concrete structure.
>
>
>
>Prescribed earthquake code is UBC '97.
>
>
>
>Does Section 1632 apply or can I use Sections 1634 together with
Section
>1630 ?
>
>This makes quite some difference in the total lateral force.
>
>
>
>In addition, our customer asks for an importance factor of 1,50 as to
my
>opinion granular storage silos would only require an importance factor
of
>1,0.
>
>
>
>
>
>Any help would be much appreciated
>
>
>
>
>
>Stefan Reumers
>
>Engineering Silo Dept.
>
>Ellimetal nv
>

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