×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

CRUSHING OF CAST IRON PIPE

CRUSHING OF CAST IRON PIPE

CRUSHING OF CAST IRON PIPE

(OP)
This is a bit out of my area. I need to confirm that a buried 30 year old cast iron pipe is ok for resistance to crushing due to new construction work above.

Pressure stress, that's easy. My questions are ...

1. how to evaluate crushing stress ... should I assume zero assistance maintianing circularity from surrounding soil (seems a good approach)?

2.How to actually calculate a crushing stress if I can get hold of a (presumably) uniform vertical load (Roark ??)?

3. How should pressure and crushing stresses be combined ... Can I assume that due to the oval section shape that would result from crushing load, there will be an internal tensile stress in the wall that can be combined directly with pressure ?

Assistance greatly appreciated.

 

RE: CRUSHING OF CAST IRON PIPE

You have received links to some good references. While I didn't catch exactly what pipe and service you are dealing with, I suspect from the question you are asking it is probably some form of gray cast iron (and maybe indeed "soil pipe" for drainage as others know or have assumed). I will nevertheless add to the list yopuhave received an article written a few years ago from a consultant in sizable firm that I see still posted at http://ww.pennnet.com/display_article/311279/41/ARTCL/none/none/1/Engineering-Analysis-Determines-Rehab-Potential-for-Cast-Iron-Pipe/, and also if applicable ANSI standards A21.1, A21.6, and A21.8 (AWWA C101, C106, and C108 etc.].  If this by some chance e.g. at least a little older and this is instead a pressure pipeline, these latter references show one how to do standard combined internal pressure and external loading analyses of any applicable rigid gray cast iron piping, as the effects of internal pressure and (in your case it appears increased) external loading including any applicable live loads or transients are as depicted to some extent "additive".  
Of course the actual thickness and iron strength, original and present bedding/support conditions, existing condition of the pipe (including joining systems), and future needs in all regards etc. are all factors that go into looking at existing pipelines in such fashions.   

RE: CRUSHING OF CAST IRON PIPE

verify if this is cast iron or ductile iron, then determine if it is a sewer drain line or a pressure waterline. also, you seem to be confusing rigid and flexible pipe. Rigid pipe does not deform into an oval shape, a flexible pipe would.

cast iron would be considered rigid and ductile iron would be flexible:

http://www.cispi.org/handbook/chapter6.pdf

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources