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Re: Very short load duration

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Jim Carey wrote:

I have a steel duct that is to be designed for, among other things, a “severe pressure pulse” load that lasts 10 milliseconds. I am trying to use STAAD’s Time History Load function to analyze this and want to be able to give it a sanity check. The short duration would seem immaterial for steel design; the quick application brings impact effects to mind. Has anyone dealt with this to know how the results should compare with those from a static load of equal magnitude – better, worse or same? Thanks.

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/*/Jim Carey, P.E./*/

"Impact effects" is just a way of saying "I'm arbitrarily magnifying the force to account for the impulse."

Using the time history load function, assuming it's modeled correctly, is the best way to handle this. It's really difficult to gauge what the "impact effect" will be, since it depends on so many parameters. I've seen situations with blast impulse effects, for example, that were close to "zero."

I have a problem with the notion that you can come up with a "sanity check" for everything. Unless you have a calibrated model to compare it with, the only thing you can bank on is that you're modeling your system correctly.

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