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Re: Moving Walkway Seismic Restraint

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Daniel,
 
It also greatly depends on the jurisdiction.  For example, if Caltrans or AASHTO are involved (as the should be) in the design, the seismic forces may be much higher than the IBC forces.  The difference in reactions may be 300% or higher.
 
 
V. Steve Gordin, SE
Irvine CA
   
 
 
----- Original Message -----
Sent: Tuesday, February 12, 2008 09:56
Subject: Re: Moving Walkway Seismic Restraint

Ben,

Thanks for your response.  The manufacturer is designing the anchorage;  however, they are designing it for no lateral force.  Their "anchorage" consists of a stack of steel shims and a wood block.  They do know that we are in a fairly high seismic zone, but insist that their structure floats.  Which of course it will, until it collides with our structure.  Then we will have a 50 kip force (plus impact) at unknown locations.

The latest development:  we have asked that their letter be stamped by a structural engineer with a local license.  They are refusing.

Any thoughts are appreciated.  We will be preparing a summary of the IBC/ASCE 7 requirements to demonstrate the magnitude of the forces involved, although this may not help.

Regards,
Daniel

----- Original Message ----
From: Benjamin Maxwell <enginerd666(--nospam--at)yahoo.com>
To: seaint(--nospam--at)seaint.org
Sent: Monday, February 11, 2008 7:34:45 PM
Subject: Re: Moving Walkway Seismic Restraint

Daniel,
 
Maybe they don't know you are talking about lateral load due to a seismic event.  Sounds stupid, and possibly insulting, but you never know.  Unless this thing uses George Jetson technology, you're going to have a seismic load to content with.  You should get that letter from them first though and then put it on the internet.  I'd love to see that one.  Good comedy there.  ;-P
 
On a serious note -
 
One way around having to extract information out of vendors who don't really know what the heck you want is to simply ask them for diagrams of the dead and live loads and an anchorage plan.  They can usually do that pretty readily. Then you can figure out what you need to from there.
 
Are you designing the anchorage of the equipment to the structure, or is this to be designed by the vendor?  Do they know they need to anchor their equipment to the structure to meet the requirements of the building code (assuming IBC-based code)?
 
-Ben Maxwell
 
 

Daniel Popp <drp181(--nospam--at)yahoo.com> wrote:
A current project of ours incorporates a moving walkway on a pedestrian bridge.  The project is at the high end of Seismic Design Category C and thus seismic forces are substantial.  However, the moving walkway manufacturer insists that the walkway will impart no lateral load to our supporting steel structure.  They are willing to put this in writing, but I am not comfortable with a 63,000 pound piece of equipment sitting on my structure without a defined seismic load path.  Calculations using the non-building sections of ASCE 7 indicate lateral forces on the order of 50 kips, which is quite different from zero.

Does anyone have any experience with moving walkway installations?  I am particularly interested to know if anyone has received horizontal (seismic) reactions for such a walkway, particularly in California or other high-seismic areas.  Any suggestions on how to extract this information from the manufacturer would also be appreciated.

Thanks,
Daniel R Popp, S.E.



Benjamin H. Maxwell, S.E.


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