huangyhg

load factors for ws pipe pressures
i am designing a 10'deep x 10' x60' concrete trench housing a water supply pipe at a pump station. the trench need not meet watertightness requirement. is the load combination of
(1.4 d + 1.4 f) per aci 318-08 sufficient for designing the trench walls for lateral thrust from the pipe pressure? (this is the test pressure specified for the pipe).

i don't know why aci doesn't seem to respect fluid forces, but i would use 1.7 times your test pressure. to me it's a live load with the same uncertainties as any other ll.
i would assume only the end walls could feel any internal pipe pressure and then only with push joint pipe and rigid connection between the wall of the pipe and the wall of the trench. if mechanical flanges or restrained joints are used, (or a sleeve through the trench concrete), then the walls will never experience the internal pipe pressure.
clampett - i used the conservative 1.7 as you suggested.
civilperson - to clarify, since i may not have explained well the conditions of the pipe.
i was told by the process/mechanical engineer that the wall would be subject to the pipe internal pressure.
the far end of the pipe in the trench is a dead or capped end, while the joint where the pipe exits the trench is a special flange (referred to on the mechanical drawings as a harness). i can see where the reaction of the pipe pressure against the capped end should be resisted by the wall unless there was some other anchored element to resist it. does this help?

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