Roshanakm:
You asked.... “Am I on right track for concrete pipe?” And, the short answer is maybe, but you haven’t even really defined your problem yet. It seems to me that you have the cart way way ahead of the horse, right now. You may have some parts of a formula for a piece of concrete pipe, but they hardly make for the development of the whole problem, at this stage. What is your background in Civil/Structural Engineering, please explain? The question you have posed is akin to the total degree course work in Civil Engineering, some Civil, some GeoTech, some Structures. And, then involves advanced courses in Strength of Materials, Soil Mechanics, and thousands of hours of product testing. And, you don’t seem to be there yet. There is no simple formula or a few equations which cover what you are asking.
It seems to me that the first thing you should do is really lay out the intent of your investigation. Are you checking this 6' dia. pipe as a beam spanning some soft soil over some distance? Are you checking this pipe as an arch/ring structure under compression and supported all around by a soil structure? Are you checking the pipe for a concentrated wheel load, from above, on a small area? These are all legitimate questions, but completely different formulas and analyses, and probably must be investigated. You should certainly understand the strengths and weaknesses of the two different pipe systems, that is conc. vs. corrugated steel culverts. I don’t think the question should be ‘is the lined deteriorated steel pipe as strong as conc. pipe’ (answer... no); but rather ‘will the lined steel pipe economically and practically serve its intended purpose’? I would talk to some conc. pipe suppliers, some corrugated steel pipe suppliers, and to some of the liner suppliers and installers. It seems all you have is some data on the Nuflow resin right now. But, all of these people should have much more test data on their complete products and design aids too, or they couldn’t sell their products and systems. Then your job may be to critique their tests and data for your needs, not reinvent the wheel/pipe design methodology. Your lining of a corroded corrugated pipe will finally involve a composite cross section made up of a partially deteriorated corrugated steel pipe (how deteriorated?), plus the new lining material. And, I would hope the Nuflow people could be of much more help to you than the chance of finding someone on E-Tips who just happened to do that same problem yesterday. What was the extent of the deterioration of the steel, how was it cleaned prior to lining, what is the bond btwn. the two materials, etc. etc.? Now you can start to define the new composite pipe material cross section. If the pipe has been in place a long time without any failures due to concentrated loading or soil deflection, then I would think your primary concern may be comparing its compressive arch/ring/pipe strength to that of conc. pipe. Or, that its new strength is as good as the original corrugated pipe was.
This storm water pipe design is not my forte, and I don’t have the standard AS/NZS 4058 you are looking at, but your question should be, ‘does your lined deteriorated corrugated pipe meet the standards and the normal design criteria?’ How long will it last? Can it de-bond or de-laminate? Not is it as strong as new conc. pipe. That might be a secondary comparison of some interest, but also compare first cost, replacement vs. repair cost, initial weight, installation costs, etc., also. The corrugated pipe get its strength from the corrugated configuration, the conc. pipe gets its strength from thickness, compressive strength and reinforcing, they are two very different animals.
