Snow load on piping-ASCE 7-16 2

[harrdick]

I am having trouble understanding the ASCE 7-16 Figure 7.13-2b figures for determining snow loads on a Pipe.

Could somebody walk me through this? (e.g., Pf = 80 psf, D = 10in, angle = 70°)

I can understand figure 7.13-2a but i have not understand what if D>0.73Pf/gamma???

What would the equation be for Qs if D > .73pf/gamma ??? (Trapezoidal snow load??)

 

[HTURKAK]

If the pipe diameter greater than 0.73pf ∕γ snow load shall be designed for a trapezoidal loading assumption.

For your case , pls look FIGURE 7.13-2b Snow Load on Individual Pipes and Cable Trays . Height of trapezoidal loading Pf = 80 psf,=0.556 psi
bottom width = 0.934 D = 9.34 in or round to 10.0 in.
the angle theta 70 degr. ( angle of repose of snow )
Top width of the loading = 9.34- 2* 0.556/TAN70 =8.94 say 9 in.

Uniformly distributed load along the pipe length Qs=9.5*0.556= 5.38 lb/in =65 lb/ft

...

 

[harrdick]

Great explanation!!!

But I can't understand top width of the loading , Could you please walk me through this??

How top width of the trapezoidal found?? formula for bottom width??

 

[HTURKAK]

Bottom width could be rounded to external dia. (D ) =10 in.
Height of trapezoidal snow section Pf= 80 psf or =0.556 psi
The snow build ups with an angle θ and equal to angle of repose = 70°
The top width + 0.556/TAN70 + 0.556/TAN70 = Bottom width = D=10 in
Top width=10-0.2-0.2 =9.6 in or conservatively take 10 in.

In this case the area of snow cross section 10*0.556=5.56 lb/in or 66 .7 lb/ft

It is not required to calculate the loads with high sensitive calculations . Eventually you will multiply with load factors or would have safety factor.

 

[harrdick]

Thank you for the explanation.

But how top width and bottom width are same????

 

[HTURKAK]

But how top width and bottom width are same????

Top width is different 9.6 in while bottom width 10.0 in. For simplicity, conservatively you can assume top width and bottom width are same. No need to sharpen the pencil and do precise calculation.