A distributed load (ex. 100 lbs/ ft) is applied over a pipe line and is assigned to Load case = GR:
When Load/Static Earthquake is selected, the Static Earthquake dialog is displayed. This dialog enables the user to define static earthquake load cases (E1 - E30) where forces are generated as multiples of gravity load in the (global) X, Y and Z directions).
However when reviewing the Seismic Load case results it appears that the distributed load was ignored during the Seismic analysis, why?
AutoPIPE is working correctly...
The philosophy is that distributed loads can represent many things for different reasons. Therefore they needed to be implemented into the program to be as flexible to use as possible.
If you define a concentrated force to GR, it is not taken into account when analyzing a static seismic load case. Concentrated forces and distributed loads generally do not represent loads due to weight. Static Seismic only considers added weight to be part of the Gravity load.
The point is that forces applied in GR case is not always due to weight. If the user wants to apply a distributed force in static seismic case, then define a separate distributed load and assign to Static Seismic load case E1..En as needed.
Example:
Apply a 20 lbs/ft distribute load over the pipeline.for code combinations Sus+E1 to Sus+E4,
1. Add Distributed load cases that is assigned to GR.
2. Add individual Distributed loads for each Static Seismic load case so that the total weight of pipe + distributed loads are considered.
Note: this is not double or triple counting distributed loads in the Static Analysis results.
a. Assigning Distributed load to GR will account for all combinations involving GR load case.
b. Assigning Distributed load to E1..En as needed correctly accounts for the total weight multiplied by the seismic factor for the respective load case.
c. Remember that distributed loads are calculates a linearly interpolated value at the position along the pipe.
"Static Earthquake" - AutoPIPE Load Case
Bentley AutoPIPE