Concrete Pipe Strength Evaluation 1

[WARose]

I got a buried concrete (storm water) drain pipe that I am trying to figure if it is ok to run a heavy load across. I have the Concrete Pipe Design Manual and it is clear how to get the loads. I just don't get how to figure the strength. It appears there are "classes".....but I don't see a corresponding load to each class (at least within the manual, I have seen it elsewhere). Does anyone know how to figure what these pipes are good for? Thanks.

 

[SlideRuleEra]

See the American Concrete Pipe Association's "Fill Height Tables". In addition to pipe wall thickness, you will have to determine bedding and backfill used or make an assumption.

The tables are for AASHTO HL-93 live load, which could be used as a starting point for determining other loads.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[robyengIT]

robyengIT (Mechanical)19 Sep 18 14:09
strength classes for concrete pipes : ASTM C76 (U.S.A.) ; EN 1916 (Europe)

From American Concrete Pipe Association You can dowload (free) a software called "Pipepac". Any way attached an excerp from ASTM C76 (my copy of standards is a bit old, but I think the classes din't change)

 

[WARose]

Thanks for the feedback. So how do I know what class my pipe is? Would I just have to make a conservative assumption?

 

[robyengIT]

U.S.A.

http://www.concretepipe.org

resources "pipepac"

Australia

http://www.CPAA.asn.au

resources "pipeclassV2" (I don't know why but I am convinced You are Aussie)

 

[cvg]

many agencies install class III as a minimum standard. but without as-builts or a mark on the pipe, or standard specification, than you may have to assume class I. If you don't know the class are you also sure it is reinforced?

The ACPA design manual also includes formulas and examples for heavy or point loading

https://www.concretepipe.org/wp-content/uploads/2014/09/cp-manual.pdf

 

[oldestguy]

If you do not know the class and are concerned about collapse, pipes can be reinforced by installing struts (timber) between the crown and the invert. There are other means usually requiring excavation and replacement of fill above the pipe. One means is called "imperfect trench".

 

[robyengIT]

At present yes, because at least you should know if it is reinforced or not. Commonly unreinforced pipes are used till ID 800 mm and furthermore the strength of the buried pipe is strictly related to bedding and filling (if it has been well compacted or not and since how long). You can, for instance, knowing diam and wall thickness, figure out ("pipepac" sftw) the theoretical necessary strength of your pipe with your new "heavy load" : the most common characteristics of pipes used are class 3 and 4. Check the pipes for existing cracks inside : crown and invert.
PS : sometime concrete makes miracles (see the video for a particular test)

https://mega.nz/#!IJk3xKAL!EnlqUucq8W4WnS2YmzcxTD8c4U7jLciK_pCLwn7PTnw

 

[robyengIT]

imperfect trench

https://rosap.ntl.bts.gov/view/dot/21685/dot_21685_DS1.pdf?

 

[WARose]

[blue](cvg)[/blue]

many agencies install class III as a minimum standard. but without as-builts or a mark on the pipe, or standard specification, than you may have to assume class I.

It appears so.

[blue](cvg)[/blue]

If you don't know the class are you also sure it is reinforced?

I think it is. Are there some classes that are routinely not reinforced?

 

[cvg]

your pipe could be any of the following, non reinforced, class pipe or D-Load:

ASTM C14-15a Standard Specification for Nonreinforced Concrete Sewer, Storm Drain, and Culvert Pipe

ASTM C76 - 18 Standard Specification for Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe

ASTM C655-15 Standard Specification for Reinforced Concrete D-Load Culvert, Storm Drain, and Sewer Pipe

 

[cvg]

or it could be some sort of low or high pressure concrete pipe also, such as AWWA C300, C301, C302 or C303, all of which would look similar and might be used for drainage and irrigation applications

https://acppa.org/what-is-cpp/types-of-cpp/

 

[oldestguy]

Before any drastic work, such as a concrete slab to spread out the pressures, get a getotech involved to look at these aspects. Depending on cover over the pipe the actual load increase on the pipe may be negligible. What has been the history of the pipe experience?

 

[robyengIT]

Be careful : if there is no enough filling depth it can become a worse load situation

 

[WARose]

@cvg: ASTM C 76 is the only one with Class I, II, etc for circular pipe correct?

 

[robyengIT]

No! in ASTM C14 are stated Class 1 - 2 and 3 as per attached table (unreinforced pipes)

 

[cvg]

suggest you scan the ACPA design manual, I posted a link. that will explain all of this and gives a methodology for evaluating loading

 

[WARose]

Thanks cvg. Will check again.

 

[robyengIT]

The ACPA design manual (that is the "Concrete Pipe design Manual" You said you have already) by hand with the help of hundred tables and diagrams, let You find the effective load on the pipe according to the laying procedure (trench, embankment, etc) and with the bedding class You can find the D-load (that is the strength of the pipe found under T.E.B. test) that is the required min strength Class according to ASTM standards. But this is an annoying and long procedure if done by hand calculations with the ACPA manual. To do this and quickly is better if You use the software (free download) called "Pipepac" : it doesn't do anything else than the calculation shown in the ACPA manual. But finally, if You don't know the strength class of the real buried pipe You can't compare anything ! You can just estimate.

 

[oldestguy]

It would help in our comments if we know the loads or vehicles, etc. as well as the cover over the pipe and its diameter. Wall thickness also would help.