I have always seen occational and expansion cases usually be greater in stress than the sustained. Now however, my sustained case is the highest stress. I am at a loss to explain this. I am wondering if there is an error in my setup. My intermediate cases are combined algebraically while my overall stress cases are combined ABS. Any ideas would be helpful. My setup is posed below...

W+H(HGR)
WW+T1+P1(HGR)
WW+HP+H(HYD)
W+T1+P1+H(OPE)
W+T2+P1+H(OPE)
W+T1+P1+H(SUS)
W+T1+P1+H+U1(OPE)
W+T1+P1+H-U1(OPE)
W+T1+P1+H+U2(OPE)
W+T1+P1+H+U3(OPE)
W+T1+P1+H-U3(OPE)
W+T1+P1+H+U1(OPE)
W+T1+P1+H-U1(OPE)
W+T1+P1+H+U2(OPE)
W+T1+P1+H+U3(OPE)
W+T1+P1+H-U3(OPE)
W+T1+P1+H+WIN1(OPE)
W+T1+P1+H+WIN2(OPE)
W+T1+P1+H+WIN3(OPE)
W+T1+P1+H+WIN4(OPE)
W+P1+H(SUS) (alg)
L4-L21(EXP) (alg)
L5-L21(EXP) (alg)
L4-L5(EXP) (alg)
L12-L6(OCC) (alg)
L13-L6(OCC) (alg)
L14-L6(OCC) (alg)
L15-L6(OCC) (alg)
L16-L6(OCC) (alg)
L17-L4(OCC) (alg)
L18-L4(OCC) (alg)
L19-L4(OCC) (alg)
L20-L4(OCC) (alg)
L25+L21(OCC) (abs)
L26+L21(OCC) (abs)
L27+L21(OCC) (abs)
L28+L21(OCC) (abs)
L29+L21(OCC) (abs)
L30+L21(OCC) (abs)
L31+L21(OCC) (abs)
L32+L21(OCC) (abs)
L33+L21(OCC) (abs)

Hi boise-nick

Yes suatain stress % may be higher than expansion stress or occational stress %.
Sustain & expansion stress develop with entirely different reason so it will be like this.
If you like to reduce suatain stress you have to add more support & have to check input pressure & pipe thickness.
To reduce expansion stress you have to add flexibility.

Your load case need to change a little.

W(HGR)
W+T1+P1(HGR)
WW+HP(HYD)
W+T1+P1+H(OPE)
W+T2+P1+H(OPE)
W+T1+P1+H+U1(OPE)
W+T1+P1+H-U1(OPE)
W+T1+P1+H+U2(OPE)
W+T1+P1+H-U2(OPE)
W+T1+P1+H+U3(OPE)
W+T1+P1+H-U3(OPE)
W+T1+P1+H+WIN1(OPE)
W+T1+P1+H+WIN2(OPE)
W+T1+P1+H+WIN3(OPE)
W+T1+P1+H+WIN4(OPE)
W+P1+H(SUS)
L4-L16(EXP) (alg)
L5-L16(EXP) (alg)
L4-L5(EXP) (abs) not require if T1 & T2 both have same Sign ( +Ve or -Ve)
L6-L4(OCC) (alg)
L7-L4(OCC) (alg)
L8-L4(OCC) (alg)
L9-L4(OCC) (alg)
L10-L4(OCC) (alg)
L11-L4(OCC) (alg)
L12-L4(OCC) (alg)
L13-L4(OCC) (alg)
L14-L4(OCC) (alg)
L15-L4(OCC) (alg)
L20+L16(OCC) (abs)
L21+L16OCC) (abs)
L22+L16(OCC) (abs)
L23+L16(OCC) (abs)
L24+L16(OCC) (abs)
L25+L16(OCC) (abs)
L26+L16(OCC) (abs)
L27+L16(OCC) (abs)
L28+L16(OCC) (abs)
L29+L16(OCC) (abs)

Note: U1,U2 & U3 may require to add combine with SRSS

Hi, there!

I believe your problem is case no. 6, where the actual Design/Operating loading case (pressure, weight and Thermal Expansion applied simultaneously) has been qualified as SUStained case instead of OPErating case. Most probably, the actual SUS case (no. 21) yields to pertinent results.

In fact, you've defined correctly this case as case no. 4. I believe it's a simple absent mindedness. You should delete case no. 6 and renumber the loading cases accordingly. "Shr" did this already....


Regards,