seismic design of reservoirs 1

[Cherie]

Hi,

I'm designing a 0.5 MG reservoir in Seismic Zone 4 in California, and the geotech engineer has supplied us with three different design spectra graphs by 1) Campbell & Bozorgnia, 2) Boore, and 3) Sadigh. I've been instructed to use the most conservative of the three. Sadigh results in the most conservative zero period acceleration, but Boore results in more conservative freeboard and shear anchorage requirements.

In past projects, I see that our company has been given a graph containing the average of the three spectral graphs by the geotech engineer, and therefore used that.

Are there any clear requirements by AWWA, or is it up to us as engineers to make a judgement call? Can we just stick with the Sadigh graph to make it simple?

Thanks.

 

[JStephen]

The person who decides which method to use should be someone who is familiar with all three. Hopefully, that's your geotech. Just put it up to him straight: "Which method should I use for design?" If he needs it, send him the info from the appropriate AWWA standard. If he can't answer your question, consider a new geotech.

Your geotech could tell you "The allowable bearing is 5000 PSF. Or if I do it the other way, it's 3000 PSF. Or method 3 gives 1200 PSF. Take your pick." That's not really a reasonable answer, and sounds like an attempt to shift design responsibility from him to you.

Don't assume that the "most conservative" answer is the best, by the way. I have seen tanks with seismic design criteria that were just completely silly. It is not a good situation, and it is doubtful the owners really gained anything from the exercise.

 

[JStephen]

I just now noticed this is in the "Water Treatment" forum- also try the "Structural Engineers- Structural Engineering Other Topics" forum. A lot of knowledge there.

 

[swine]

Cherie do you have a link that summarizes these ARS curve construction? Earthquake design is like runoff analysis, lots of false precision. Ultimately, the soils engineer must specify the curve, and you must agree that it is correct, sounds like something that can be taken care of with a phone call. But, ultimately one of you must know what your doing.

1) Campbell & Bozorgnia, 2) Boore, and 3) Sadigh.....?