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Max span for 250NPS
2

Max span for 250NPS

RE: Max span for 250NPS

Kevin,
Amazing!  Where is that?
Regards,
Bill

RE: Max span for 250NPS

I wonder whether they intend to brace it against swaying?

RE: Max span for 250NPS

KevinNZ,
        This is not new practice. Seen this done in the UK many years ago to span across a motorway, except there were two lines approaching from two direction which were tied together to give some lateral stability.  

RE: Max span for 250NPS

That's a big exception.  

Must not be much wind or earthquakes there.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

RE: Max span for 250NPS

(OP)
It is located at Kawerau New Zealand.

The earthquake design loads are quite high .85g static equilivant.

We used modal anayisis for the Earthquake design. First period is quite long.

Wind loads are upto 95% allowable stress.

We started with a design with two loops. Then one braced loop with stay wires. Then we found a conbination of pipe that did not require stays.

RE: Max span for 250NPS

Impressive!

What's inside the pipe gas, oil, water?

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

RE: Max span for 250NPS

KevinNZ (Mechanical)

Thank you for the technical update

steve

L S THILL

RE: Max span for 250NPS

KevinNZ,

never seen that before!

Do you assess this piping by hand, with software like CAEPIPE or CII, or more detailed FEA?

yours,

RE: Max span for 250NPS

Very clever!  Can you give some details of the erection?  Is the pipe actually arched or is it simply "flexed"?

RE: Max span for 250NPS

I'm still kinda' wondering why.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

RE: Max span for 250NPS

(OP)
The pipe was first design checked with Autopipe and all the piping code rules apllied. We then passed the design on structual engineers who looked at the compressive load and blucking issues.

The pipe is constructed with mitres. Was fabricated and isulated on the river bank then lifted into place with one lift from far side.  

RE: Max span for 250NPS

Was this construction method cheaper than getting the appropriate permits to trench?  Who covers the liability insurance for kids trying to use it as piece of playground equipment to cross the creek?  Will this be fenced off?  Anyways, if it is possible for anyone to attempt to climb and it is not protected, an attorney in my country might call this an attractive nuisance.  

Anyways, it looks very cool.  At first glance (and second for that mater) I would question the controlling occasional load being wind at 95% when you have a static seismic loading of 0.85g.  What was the greatest miter angle in the piping?
 

RE: Max span for 250NPS

(OP)
This is hot pipe and needs to expand and stay dry so trenching was never an option.

The loop ends is on private land and normal pipe bridge or straight span would have the same temptation to climb. The owners may yet fence the ends.

If we used static loading for EQ then it would have been 0.85g but we used modal design and an acceleration spectrum. Wind does not combine with EQ loads.

Mitres are only a few degrees.
 

RE: Max span for 250NPS

It looks good, but what happens if a group of kids come along and think it will make a good swing?

RE: Max span for 250NPS

Nice picture.  Alas, we are of course all now governed by all kinds of codes, regulations, and standards of practice.  Pipes no doubt also have real limitations, based on their own innate/unique strengths, moduli, and sometimes also I will note by properties of coatings and linings that come along with the package.  Nevertheless, what is actually possible is perhaps governed no less by the imagination of the designer/engineer, as well as how all the pieces are put together.  
In that regard you are right in that what you are showing of a pipe crossing in the form of an arch is in fact far from "new practice", and you may be interested in an installation depicted in the foreground of the picture at http://www.archives.gov/research/american-cities/images/american-cities-025.jpg and that perhaps even more interesting in  the image at http://www.civil-war-photos.com/Misc/imagepages/Bridge%20across%20Rock%20Creek,%20on%20Line%20of%20Penn.%20Ave.,%20carrying%20Washington%20Aqueduct..html.  I think the latter is of a newer installation, circa 1858- also in the Washington, D.C. area, that was accomplished with twin 48" gray cast iron (special flanged) pipes that carry not only water, but also carried for many years the structural dead and live/vehicular loads of this Pennsylvania Avenue bridge crossing.  This 60+ meter pipe/bridge crossing has arguably even a little more basic redundancy than the modern single pipe arch design, in the form of twin lines and also by lateral stability of the twin pipes harnessed together.  The bridge/pipeline depicted in the old Mathew Brady image was designed (of course a few years before the American Civil War) by Captain Montgomery Meigs of the "War Department" (working there/then for one Jefferson Davis), and I suspect these pipes are still in service today (albeit at lower pressure than yours!)          

RE: Max span for 250NPS

(OP)
Rconner

When researching what we could do for this loop we did find other examples using twin pipes and even a patent for such. Nothing as old as your pictures though. Thanks.
 

RE: Max span for 250NPS

Kevin,

I am very, very curious about the piping details encased in the concrete anchors on either end..

Did you include some kind of trunion structure or welded plate design within the concrete ?

How about a local analysis of the welds at the concrete/steel interface ?

It seems to me that, depending on the piping design code, such a design might fail a "local stress check" at the anchors before it would fail bending stress in the mid-span...

My opinion only

-MJC

   

RE: Max span for 250NPS

(OP)
The main pipe is 250NPS and the trunions are 500NPS. The weld between the truion and the pipe is a full weld around the pipe much like a slip on flange.

The stresses in the 500 pipe are not high. We included the trunions in the pipe stress model.

Kevin

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