Thrust Block Design 5

[mtroche]

I need information about the thrust block design procedure. In one side I have the momentum formula, and in the other side I have this formula T=2PAsin(phi) where “P” is the pressure, “A” is the pipe cross section area where the flow goes, and “phi” is the bend angle. Is the last formula a "rule of thumb" for the thrust block design? Using this formula, an engineer calculated 10 concrete trucks to build a thrust block for a 45 degrees, 48inches, vertical bend, and using the momentum formula I get only 2 concrete trucks for the vertical thrust block. The pressure (P) that he used was an assumed value equal to two times the working pressure for this pipeline. The working pressure for this pipeline is 150psi. So, at the end, the engineer is multiplying the working pressure by four!!

I know... I know. To design a Thrust Block I have to use the momentum formula and take in account the weight of the bend itself and the water inside the bend if it's a vertical thrust block, but I am a little confused with the engineer using that formula.

I'll be grateful if someone of you show me an example on how to design a vertical and horizontal thrust block.

Thank you for your information.

 

[mikolay]

Have you checked the example used in the DIPRA publication on thrust restraint design?

 

[Denis]

Suggest you check out the following reference: "Pipe Restraints: Design Fallacies" by Patrick J. Creegan, F. ASCE which appeared in the Journal of Transportation Engineering, Vol. 109, No. 6, November, 1983. This peer reviewed paper will give you clear definitive guidance and several worked examples.

 

[nec]

If you have not found the information needed,contact me I can put you in touch with an engineer that has designed pipe systems for twenty years. NEC,

http://WWW.NATIONALEROSION.COM

 

[obzpae]

DENIS

Can you tell me where I might be able to get a copy of the "Pipe Restraint....." paper?

Thanks,


John

 

[cvg]

better yet, do what most agencies are doing now, and eliminate the thrust block altogether. Restrain the joints! For a 48" pipe, this is a better idea. Sure, it's easier to just dump a bunch of "cement" in there - and a lot easier than installing those expensive mechanical joints, - but what a mess if you ever have to dig up those 10 truckloads of concrete.

Chuck
cgopperton@stantec.com

http://www.stantec.com/