Cast-in-place-pipe for an "egg" sewer. (U.S.A.) 1

[plastcc]

I have a specification to design a liner for non-circular gravity flow pipe using the beam method. There is no reference to any ASTM or other standard regarding the beam method. Any information on this method would greatly be appreciated.

 

[civilperson]

Perhaps you mean "Steam" method. This cures a plastic liner after pressure forms it to the inner shape of the pipe.

 

[plastcc]

Thank you, civilperson. The liner will be cured by steam rather than water, however, the liner thickness must first be calculated to withstand the external loading. We spec ASTM F1216-07b for calculating the liner thickness of round pipe applications. Non-circular pipes, such as this egg, must have the liner thickness calculated by the beam method. My best guess of this method is that the cured liner shape will either be considered as a beam for loading or there is a simulated beam acting as a load on the shape. I really don't know. I do appreciate your response and I hope this clarifies my original question.

 

[bimr]

Perhaps you are referring to:

ASTM D 2344 Apparent Horizontal Shear Strength of Reinforced Plastics by Short Beam Method

http://www.interplastic.com/UserFiles/File/M_VEBrochure.pdf

 

[dicksewerrat]

You have to use the Wrc method that originated in England. There are two equations, one for deflection and one for buckling. If you are not very familiar with the design process, don't try to explain it in the spec. Just say you have an egg shape,giving the inside width and height. . Let the contractors bidding tell you what you need for liner thickness.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[dicksewerrat]

One other thing, we call it Cured-in-Place. Cast-in-place normally refers to concrete.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[plastcc]

Bimr, thanks for the suggestion. I checked and unfortunately it doesn't seem to apply.

Dick, the existing spec calls for liner thickness for round pipe to be provided by use of ASTM F1216 and for non-circular pipe to be provided by the beam method. The contractor will submit his liner thickness, telling me what thickness is needed. Before I hold him to providing the thickness, calculated by the beam method, I want to be sure I have an understanding of the method and a resource for it, should he request it.

Nice catch on the "Cast" instead of "Cured". I think I was in holiday mode a little early, plus I have two CIP concrete projects in progress.

My in-company experts are back from vacation and are looking into this. I'm still open for suggestions.

 

[dicksewerrat]

Here is a design for a 64 by 42 ellipse. the formula are the same for an egg.
Height 42.8 inches 1070 mm
Width 64 inches 1600 mm
Assumed Thickness (t') 1.8 inches 45 mm
EffectiveLength (L) 60.400 inches 1510 mm
Ht of WT above invert (H) 5.7 m

Physical Properties

Modulus of Elasticity (Es) (Short term) 507614PSI 3500 MPa
Modulus of Elasticity (El) (Long term) 253807PSI 1750 MPa
R (0.5 for straight sides, 1 for curved) 1
Limiting Stress (Sl) 2901PSI 20 MPa
Design
H = 340Sl(t/L)² (Stress)
Rewriting
t = L (H / (340 Sl)) 0.5

t = 43.7 mm 1.721 inches

H = 236REl(t/L) 3 (Deflection)
Rewriting
t = L (H / (236 R El )) 0.333

36.2 mm 1.426 inches


Lining Thickness Required = 43.7 mm 1.721 inches

This will give you a good idea of the liner thickness. It is always thicker than the round equivalent pipe. But that is where i always start. Also, inthe formula there is no place for the live load or soil load. Convert them to feet of water and add to the hater head on the pipe. the liner gets thick in a hurry.


Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[plastcc]

One more question, Dick. In researching the WRc manual, I found that the 4th edition is the last "Sewerage Rehabilitation Manual". It has been superceded by the on-line version and renamed, "Sewerage Risk Management". What I want to know is if I subscribe to the new SRM, will I get what I want as far as structural design methods, to include liner thickness calcs?

I am under the impression that the old SRM was a three volume set. Has it merged into one volume at the 4th edition? Does the new "Sewerage Risk Management" manual include the information from the old "Sewerage Rehabilitation Manual"?

Thanks.

 

[dicksewerrat]

I have the old manuals so I can't really say what the online version has.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[plastcc]

Were the older editions multi-volume sets?

 

[dicksewerrat]

Yes they were.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

Here is the ASTM test method:

ASTM D790 - 07e1 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials

1. Scope

1.1 These test methods cover the determination of flexural properties of unreinforced and reinforced plastics, including high-modulus composites and electrical insulating materials in the form of rectangular bars molded directly or cut from sheets, plates, or molded shapes. These test methods are generally applicable to both rigid and semirigid materials. However, flexural strength cannot be determined for those materials that do not break or that do not fail in the outer surface of the test specimen within the 5.0 % strain limit of these test methods. These test methods utilize a three-point loading system applied to a simply supported beam. A four-point loading system method can be found in Test Method D 6272.


ASTM F1216 - 09


ASTM F1216 - 09 Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube

 

[dicksewerrat]

F1216 is for round pipe and round pipe that is less than 10% ovality. Most people will want a design based on the Wrc(beam) method. Anything over 10% is a major risk, since it is already in failure according to most people.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

"This paper has shown that the WRc rehabilitation design for Type I liners has serious theoretical and practical flaws. Although this paper focuses on the brick egg sewer problem the design method is applicable to circular sewers and for this case it appears that the WRc formula for
crown bending moment is in error by a factor of two."

http://www.nastt.org/store/technical_papersPDF/416.pdf

"The German code ATV-M 127-2 published in 2000 for the design of linings to rehabilitate sewers has proved as a helpful guideline to find the optimum wall thickness of any liner material, e.g. CIPP and stainless steel manchettes. Much rehabilitation work in different European countries has been performed successfully using the code."

http://www.hb.fh-muenster.de/opus/fhms/volltexte/2008/220/pdf/Falter_NoDig2008_C_1_03_corrected.pdf

http://www.nodigshow.com/2008/TrackOne.html

 

[dicksewerrat]

However, the process that is recognized in the US for non-circular pipe and pipe more than 10% ovality is still the Wrc or beam method of design.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com