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RE: Piles and Seismic Forces

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Thanks, Harold
As usual, your answers are very helpful and in my case
educational.  Our new National Building Code is due to
be out in September and the new seismic requirements
will be more stringent and also more like yours.  Being
seismically challenged, I will have to bone up this
stuff.

Thanks again
Gary

On 22 Aug 2005 at 16:45, Harold Sprague wrote:

> Gary,
> 
> "Seismic loading" is an inertial response force in the structure to
> the earthquake ground motion.  In an earthquake the rock shakes at the
> epicenter.  At the building site, the movement from the rock is
> transfered to the soil to the building foundations to the building
> superstructure and then to your crane.
> 
> The piles will be like noodles and not reduce the lateral eathquake
> ground motions.  The type of soill "site class" WILL have an effect on
> the inertial response of the building structure.  For Puerto Rico,
> with a site class E, and an Ss of 1, the soil will actually work kind
> of like a base isolator and will reduce the lateral earthquake ground
> motion accelerations for short period ground motions.  However, the
> site class E will amplify the long period ground motons.
> 
> Bottom line - LATERAL earthquake in structure inertial response forces
> will not change by using piles.
> 
> Regards,
> Harold Sprague
> 
> >From: "Gary Hodgson & Associates" <ghodgson(--nospam--at)bellnet.ca>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: seaint(--nospam--at)seaint.org
> >Subject: Piles and Seismic Forces
> >Date: Mon, 22 Aug 2005 11:02:13 -0400
> >
> >List,
> >
> >I've been designing a crane runway for Puerto Rico (first designed in
> >'99 and then postponed).  The soil is a Type SE.  Consequently, the
> >seismic forces are quite high.
> >
> >The end customer has said that the foundation will be placed on
> >piles.  How will this affect seismic loading?  As we are not relying
> >on the soil, can we reduce the seismic loading and what can be used
> >in lieu of SE?
> >
> >thanks muchly,
> >Gary
> >
> 
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