Load case

Posted by: Abdelkader

Load case - 06/30/10 02:39 AM

I got a mission to calculate a pipe line (B31.3) under seismic load (U1, U2) and wind load (Win1, Win2) so I defined the load cases below by using the CAESAR II user guide

L1=W+T1+P1
L2= W+T1+P1+U1
L3= W+T1+P1-U1
L4= W+T1+P1+U2
L5= W+T1+P1-U2
L6= W+T1+P1+Win1
L7= W+T1+P1-Win1
L8= W+T1+P1+Win2
L9= W+T1+P1-Win2
L10= W+ P1
L11=L1-L10
L12=L2-L1
L13=L3-L1
L14=L4-L1
L15=L5-L1
L16=L6-L1
L17=L7-L1
L18=L8-L1
L19=L9-L1
L20=L12+L14
L21=L12+L15
L22=L13+L14
L23=L13+L15
L24=L16+L18
L25=L16+L19
L26=L17+L18
L27=L17+L19
L28=L10+L20
L29=L10+L21
L30=L10+L22
L31=L10+L23
L32=L10+L24
L33=L10+L25
L34=L10+L26
L35=L10+L27

From L12 to L19: Algebraic Method
From L20 to L27: SRSS Method
From L28 to L35: ABS Method

Is this combination are wright?
the results were acceptable and logic but I have some doubt about the load cases combinations



Posted by: Loren Brown

Re: Load case - 06/30/10 09:19 AM

I wouldn’t normally combine the U1+U2 (L22 above) or Win1+Win2 (L24 above) together without adding a scale factor. What that is doing is changing the wind or seismic direction to 45 degrees off the Caesar II coordinate axes, but it is also making the skewed wind and seismic forces 1.4 times larger than defined in the input. I would probably do something like this:

L22=0.707L13+0.707L14

Also note that you don't review forces, moments, restraint loads, or displacements for any combination case (L11 to L35).
Posted by: Abdelkader

Re: Load case - 06/30/10 10:34 AM

Thank you for your answer. It was really very helpful
in my case I have only to calculate the line under seismic and wind load cases Thats why I didin't conciderate any forces, moments, restraint loads, or displacements.