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ASCE - 7-10 NONBUILDING STRUCTURE FREQUENCY

ASCE - 7-10 NONBUILDING STRUCTURE FREQUENCY

ASCE - 7-10 NONBUILDING STRUCTURE FREQUENCY

(OP)
DEAR ALL

I AM DESIGNING A STRUCTURE WHICH IS SUPPORTING A LARGE SILO ON TOP, AS PER ASCE CHAPTER 15 - IF NON-BUILDING STR SUPPORTED
ON BUILDING HAVING WEIGHT 25% MORE THAN COMBINED WEIGHT OF BOTH TO BE DESIGNED AS PER CL.15.3.2.

I AM HAVING DOUBT THAT FOR CALCULATING FUNDAMENTAL FREQUENCY OF THE NON-BUILDING STR (THAT IS SILO) - ONLY THE
FREQUECY OF THE SILO WITH DEAD WEIGHT OF SILO PLATE HAS TO BE CONSIDERED OR
SILO WITH FULL FILLING WEIGHT OF INSIDE MATERIAL TO BE CONSIDERED FOR FREQUENCY
CALCULATION

RE: ASCE - 7-10 NONBUILDING STRUCTURE FREQUENCY

Why not check both, to define the boundary conditions? If your silo is a short, squatty style, it will likely be much stiffer than, and will have a very different period from, a taller, more slender style. For seismic analysis I have often used a weight of 80% full of product. Of course, there is some dampening with intergranular friction and shifting during a seismic event. This is similar to sloshing of water in liquid storage tanks. And this friction, along with its static inertia, will place a reactance load on the side wall of the silo. There is a reference paper, "Dynamics of Solid-Containing Tanks", which can be downloaded from the internet as a PDF, and it contains some useful information on this subject.

Thaidavid

RE: ASCE - 7-10 NONBUILDING STRUCTURE FREQUENCY

The normal operating conditions of the structure is what I would use. If the silo will be empty for 5% of its lift span, 100% full for another 5%, then neither of those qualify. If the normal condition is between 30 and 70% full then that would be what it should be designed for. Very little possibility that the earthquake will strike during the rare cases where the silo is 100% full.

Same rational about why we don't design building structures for 100% live load.

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