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# Thrust of fire standpipe, Load category and load combination

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## Thrust of fire standpipe, Load category and load combination

(OP)
Hello

I'm working on a steel stair tower design. One of the requirements that was requested is to install fire standpipe and connect it to the stair tower leg. The standpipe has several places where it changes direction and the outlet is at the top of the stair tower where it will be accessed at the last top level. Thrust will be present at the locations where the standpipe changes direction and also at the top outlets. Does anyone know under what type of load thrust will be and what is the load combination for this type of load in combination of other types like dead, wind, seismic, etc? Please let me know.

Thank you
Johnny

### RE: Thrust of fire standpipe, Load category and load combination

The thrust in the standpipe depends on the flow rate. I have calculations for a stand pipe design if you want them. way back, I was a resident engineer on a bridge rehab project and the DOT wanted a standpipe system installed.

### RE: Thrust of fire standpipe, Load category and load combination

Once you know the force directions at the inlet and outlet of the elbow then it will be the resultant vectorial force that determines the magnitude and direction of that thrust. Don't forget to add the dead weights of the pipes filled with water and the effect torques that such dead weights may create on the anchor. Beside the flow rate as mentioned by JMGMA you will need to determine the static pressures at the inlet and outlet of the elbow and that is a bit more problematic because you have to determine the pressure at that flow rate from the fire department pumper, then estimate the pressure loss thru hose connections, and piping leading to the inlet of the elbow at which point the inlet pressure will be static pressure at fire department pumper minus pressure loss; then, use Bernoulli's equation to determine outlet pressure of elbow if it has a reduced outlet, otherwise it will be nearly the same value as the inlet pressure. Forces at inlet and outlet of elbow will be pressure times cross sectional areas, then do as above.

### RE: Thrust of fire standpipe, Load category and load combination

Remember the static head pressure between the pumper fire pump and the elbow was not included because the pressure gauge on the fire pump will register that additional pressure in order to meet the flow rate.

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