Seismic Diagonal Load?
Seismic Diagonal Load?
(OP)
I'm designing elevated structural steel support for a set of four ash hoppers at an existing electric power plant. Each hopper is essentially a tank with four short legs. Each leg has a base plate that will be anchored to the new steel members.
The hopper manufacturer has given the table of loads (dead, live, tank contents, seismic) at each base plate.
My question concerns the seismic loading, three load are given:
1. "Seismic Normal"
2. "Seismic Shear"
3. "Seismic Diagonal"
I have not encounterd the term "Seismic Diagonal" before. Insight into to this term will be appreciated.
The hopper manufacturer has given the table of loads (dead, live, tank contents, seismic) at each base plate.
My question concerns the seismic loading, three load are given:
1. "Seismic Normal"
2. "Seismic Shear"
3. "Seismic Diagonal"
I have not encounterd the term "Seismic Diagonal" before. Insight into to this term will be appreciated.






RE: Seismic Diagonal Load?
RE: Seismic Diagonal Load?
Anyway, don't be afraid to just call the designer and ask- no reason to guess on something like this.
RE: Seismic Diagonal Load?
RE: Seismic Diagonal Load?
RE: Seismic Diagonal Load?
RE: Seismic Diagonal Load?
Seismic Normal: plus/minus 8 kips
Seismic Shear: plus/minus 3 kips
Seismic Diagonal: plus/minus 11 kips
For now, I have been assuming the following:
"Normal" is vertical.
"Shear" is horizontal (from any direction).
Had considered "Diagonal" as being the result of vector addition, but that does not seem to make sense with the numbers presented.
JStephen - Will call the vendor, if necesssary, however it is still early in the project and was assuming that this "Diagonal" force was a "gap" in my knowledge. (Didn't want risk embarrassment if this is an "easy" question.)
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RE: Seismic Diagonal Load?
Let us know when you find out. We can see if anyone was close and we will know if we ever come across it.
RE: Seismic Diagonal Load?
The magnitude of the loads makes me think it's something similar to AASHTO's seismic load cases (1.0Longit. + 0.3Trans. & 1.0Trans. + 0.3Longit.) to account for forces "diagonal" to the structure.
RE: Seismic Diagonal Load?
Normal is vertical.
Shear is horizonal.
Diagonal is exactly that, the force assuming acceleration across the diagonal of the hopper such that opposite corner columns provide the push pull effect. - 8xroot(2) - Its also a vertical load.
RE: Seismic Diagonal Load?
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