USGS Seismic Design Maps and the Government Shutdown. 1

[dgraff]

Due to the government shutdown, the website geohazards.usgs.gov is unavailable. I use this website to get all of my seismic design parameters when determining my loads.

What are other avenues to get these design parameters until the government gets up and running again?

David

 

[WillisV]

The maps printed in the building code and ASCE7 work nicely.

 

[dgraff]

Yes, those maps will work for a ballpark figure. However I was looking for something a little more exact than trying to interpolate between two closely placed lines.

David

 

[WillisV]

They are close enough - loads are not known to that kind of accuracy.

 

[msquared48]

Back to my old list of values by Zip Code that I printed out years before this.

Mike McCann
MMC Engineering

 

[dgraff]

Once again, I agree but you are missing the essence of my problem. The site I am working on is in LA County which has a jumble of varying spectral response acceleration values. Even with the best printed maps that I have available to me (ASCE7-05), within a small distance Ss values can vary from .187g to .273g. To me this is a very large difference in loading.

So to get the best value for my client, I would like to have the most accurate values possible. While yes I could take an educated guess at the closest design parameters, I would prefer to have something with a much better accuracy than what I would get using those maps.

David

 

[cvg]

2008 maps are located here

http://earthquake.usgs.gov/hazards/products/conterminous/

 

[dhengr]

I don’t think you are allowed to do any structural design or seismic design while the gov’mt. is shut down. But thankfully, I think they cancelled all the EQ’s during the shut down, so don’t worry. How can you trust any of those maps and charts if the gov’mt. ain’t working to keep them a changin, day by day. I got some values for the south end of my building yesterday, never thought it would come to this, but now I need the values for the middle and north end of the building.

The ‘essence of your problem’ is that we/they don’t know those values to +/- one square foot in position on the face of the earth. Does that web site guarantee those values, and that your building will never have any problems when you use them. Are those lines on the maps perfectly vertical and running to the center of the earth? Or, do some of those EQ zones change on an inclined, even ragged, plane. In which case the footings in a wall might be in one zone, while the first floor is in another.

 

[JStephen]

So plop that map on the copier, hit the 400% button and blow your county up to full-page size, adjust as required, and overlay on a state map, measure it with the ruler, interpolate, etc.

 

[strucguy]

This thread gave me the much need laughter for the day. You guys rock!

 

[cvg]

...they don’t know those values to +/- one square foot...

I doubt those values are accurate to +/- 5 miles. So both ends of the building will experience the same earthquake. Sure, the digital maps are precise, but the accuracy is based on the lousy geologic data. that includes estimated locations of faults, estimated depths and locations of bedrock and a limited number of seismographs and other instrumentation. The only way to tighten that up is with your own geologist on-board telling you different.

 

[SAIL3]

and also based on 5% structural damping....can you accurately determine the strucural damping of your structure????

 

[ajh1]

Call the city building department and ask them what the correct value would be. They are the ones that have to approve a number anyway.

 

[JLNJ]

They turned the website off?

That's just stupid.

 

[steellion]

Calling the local code official is your best bet.

 

[fegenbush]

I read an article yesterday (which I cannot seem to find today) that the move to shut down certain no maintenance or low maintenance services is strictly political to make the shutdown "as painful as possible." I think that is the root cause of the issue. It takes more energy to shut the website down than it does to keep it up assuming the shutdown period is not prolonged.

In the meantime, for bid designs, the maps are of sufficient resolution in most areas as to yield a negligible variance between designs. In areas similar to those dgraff mentions (LA County), all contractors and engineers share the same handicap and should proceed with a level of conservatism with which they agree.

For final designs, I have found the project geotechnical report to be invaluable in determining the appropriate seismic parameters.

 

[FixedEarth]

You can get Ss value from ASCE 7-05 Figures 22-1 to 22-14

You can get S1 value ftom ASCE 7-05 Figures 22-2 to 22-14

Fa is from IBC 2009 Table 1613.5.3(1), page 341

Fv is from IBC 2009 Table 1613.5.3(2), page 341

SMs is Fa*Ss

SM1 is Fv*S1

SDs is 2/3*SMs

SD1 is 2/3*SM1

 

[wannabeSE]

dgraff,

I understand your dilemma. I am attaching a screen shot of L.A. County from the ASCE 7-10 design maps. In some place, it looks like the width of a line is greater than the clear distance between the lines. The USGS tools make life much easier.

I only have a couple suggestions. Have you tried downloading the JAVA script tool that is good up to ASCE 7-05? The design values should be fairly close to ASCE 7-10 (I know one location in L.A. where Ss is going up 10% - the new code takes effect on 1/1/14 in California). Also, you might look at the USGS data sets to see if it can be used (

http://earthquake.usgs.gov/hazards/designmaps/datasets/).

 

[Lambeam]

The web application is up and running this morning:

http://geohazards.usgs.gov/designmaps/us/application.php

 

[a2mfk]

This thread made me simultaneously love and hate these United States of 'Merica.....