Understanding Heger Pressure Distribution

[ITsSB]

I am trying to design an RC Pipe culvert to AASHTO LRFD, SI Units 12.10 and trying to plot heger pressure distribution on an RC Pipe and I am having difficulties understanding it. So, my questions are: -
1. In the this picture, is my understanding of A3 correct?

If so, here i got y1 negative for a unit external diameter of pipe. So, something must be wrong. (maybe the external diameter of the pipe has something to do with it? so my next question will be : -​

2. How do i apply the parameters (coefficients/arching factors) of a unit external diameter pipe to my actual one? do the coefficients change? and how?
3.What kind of software options do i have to model and analyse this pressure distribution. (mainly the parabolic ones.)

 

[CarlB]

A3 appears to be the entire trapezoid over the top of the pipe, since A3=VAF. So use 0.5xA3 in your equation, then y1 should be positive.

 

[ALK2415]

Dear Simeneh
if you have the papers of AASHTO that contains the formula and the notations of each variables
i could help in make simple program that calculate and draw it for u ?

 

[ITsSB]

@adn26 Unfortunately, this is the most i could get from AASHTO LRFD SI units on heger pressure distribution. Nothing more.
Also, installation type is just a category based on the type of bedding material, thickness or compaction level to be provided and is given elsewhere on the code. We can just assume it as type 1 for this.

 

[robyengIT]

previously there was a software program (the one I have) called "PIPECAR", now superseded by "ERIKSSON PIPE" available at ACPA-American Concrete Pipe Association updated to 7th edition of AASHTO LRFD (30 days trial)

 

[ITsSB]

@robyengIT Thank you for your kind response, but, I have that it doesn't explain what goes under the programme or plot the heger pressure distribution. I really need to know the science behind this and what is being done. Not just the final outputs. Or, at this point, any decent material where i can read on heger pressure distribution. I don't think it is well documented like the other topics. There is no wikipedia page explaining it too. I just don't want to play a guessing game on the diagram and proceed with it.

 

[robyengIT]

additional info (ASCE 15-98 : Standard practice for Direct Design of buried precast concrete pipe using Standard Installation - SIDD)

 

[robyengIT]

biblio ref

 

[ITsSB]

@robyengIT Thank you. The second reference is actually the original thesis of Heger. I got it from the MIT website here. I see a lot of calculus/integration written all over it, it is going to be a long ride, but, I am willing to give it my time as this is going to be a part of one crucial skill for my current job. I really appreciate your effort. Thank you again!