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Re: Moving Walkway Seismic Restraint

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Something hold this thing up. It has points of reaction to your structure. Have them provide you those reactions.

Then get your seismic factor and assume their "anchorage" can transmit the lateral force into your structure by converting the vertical reactions into horizontal seismic forces (or lump the sum of the reactions). Use conservative values for ap and Rp (or their similar values in the new code).

Put a big note on your drawings plans :

"All equipment weighing more than 400lbs shall be seismically anchored via positive connections to the main structure. Per CBC .... anchorage shall not be accomplished via friction alone. Anchorage shall be designed and stamped by a licensed engineer and shall be submitted to EOR prior to installation. Calculations and drawings shall indicate weights, center of gravities in all 3 axis and shall consider both overturning and sliding effects."


On Feb 12, 2008 9:56 AM, Daniel Popp <drp181(--nospam--at)> wrote:

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.


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

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)> 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.

Daniel R Popp, S.E.

Benjamin H. Maxwell, S.E.

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