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12-Amethyst

## Lusk_Flexible Pipe Design.zip

Pipe materials are classified as either rigid (e.g. concrete, vitrified clay, cast iron, asbestos-cement, etc.) or flexible (e.g. PVC, HDPE, ductile iron, steel, etc.).  The strength of rigid pipe is determined by its crush strength.  The strength of flexible pipe is determined by pipe and soil stiffness and is usually evaluated in terms of the deflection of the pipe wall under load.

The purpose of these two worksheets* is to estimate pipe wall deflection, using the Modified Iowa Formula, for a single pipe (material & diameter), with a solid wall, in a trench condition, with a superimposed wheel load.  Lusk_Flexible Pipe Design - Range of Soil Cover.mcdx is intended for a complete system design where the cover on the pipeline varies from location to location.  Lusk_Flexible Pipe Design - Single Case.mcdx is intended to evaluate a single location and is thus shorter and simpler to use.

These worksheets apply primarily to gravity flow pipelines such as sewers, storm drains, and culverts.  They also apply to situations where such pipelines are subject to minor and/or transient surcharging where the internal pressures will never be enough to warrant a pressure pipe analysis.

*Both worksheets are in Mathcad Prime 3.0 format.  For users of other versions of Mathcad, I have included Adobe Acrobat .pdf files for your viewing pleasure.

2 REPLIES 2
1-Newbie
(To:FredLusk)

I used your calculation on a 150 GRP pipeline and it worked great . I don't understand the {17} multiplying by 4 for full loading, can you explain?

I tried the AWWA M45 approach but my results in Step 9 simply don't make sence. You clearly understand this stuff a lot better than myself, would you be able to assist?

G

12-Amethyst
(To:FredLusk)

Graham…

Holl's integration of Boussinesq's Equation is for one quadrant of the wheel load pressure (i.e. 1/4).  Multiplying by 4 gives the full value of the load.

BTW, I'm glad you found this worksheet useful.

Fred

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