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RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS

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Stefan,
Let me know the location of your site. I may already have the Ss and S1 for your site, or at least get you close. I do a lot of work in the Middle East.

I would go with your somewhat conservative approach. I see where you are in a difficult situation with the concrete base engineer being a different entity.

Regards,
Harold Sprague





From: "Stefan Reumers" <Reumers.S(--nospam--at)ellimetal.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS
Date: Thu, 16 Feb 2006 18:18:09 +0100

Thanks again Harold for your quick reply.

I'm aware of the shortcomings of the UBC-code, and I would very much
like to make the comparison between UBC and ASCE 7-05, but here's the
tricky part :

The silos will be installed somewhere in the Middle-East, and there is
no exact data available to make a spectral response analysis.
Is it possible to translate the zone 2B of the UBC'97 to a certain value
of the spectral response acceleration according ASCE ?

In addition, there's another problem :

The engineering of the silos is our responsibility while the supporting
structure will be designed by a Korean engineering company, so the exact
flexibility of this structure is still pending.
Of course it is possible to estimate the flexibility and make an
analysis of the combination of both silos and supporting structure.
To my opinion however, the calculations will be conservative if we
consider the supporting structure as having an infinite rigidity.

Regards

Stefan Reumers








-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
Sent: donderdag 16 februari 2006 17:00
To: seaint(--nospam--at)seaint.org
Subject: RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS

Stefan,
Given your constraints, treating the silos as nonstructural components
per
section 1632 should result in a more conservative design.

I just get nervous when I see the UBC zones being used.  There were many

significant changes in the transition to the IBC.  Studies have shown
that
you can be very far off with base shear calculations when compared to
using
seismic specral ordinates.

It might be worth a little extra time and see how your design would look
if
you used the ASCE 7-05.  You don't have to tell your client, but it
would be
an intersting check.

It is worth noting that the Veletsos paper is about the best document
that
there is on seismic design of silos and bins containing granular
material.

Another good document for reference is Tubular Steel Structures by
Troitsky.
  But the Veletsos paper is what should be used for seismic design.

Regards,
Harold Sprague





>From: "Stefan Reumers" <Reumers.S(--nospam--at)ellimetal.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: RE: UBC 97 - SEISMIC DESIGN GRANULAR SILOS
>Date: Thu, 16 Feb 2006 09:01:44 +0100
>
>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/webviewab
l
>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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