Geotechnical Design Memorandum GD-3, Rev A

[msquared48]

I received a comment back from a local jurisdiction pertaining to the seismic factors used in the design of some concrete stairs for a light rail parking garage.

I have no clue what the reference is and may have to ask the reviewer, but do not want to look uninformed, although I presently am...

Anyone have a link to this publication, whatever it is?

Googling does not seem to help, as least not for Washington... Still looking.

Thanks.

Mike McCann, PE, SE (WA)

 

[Mjkkb2]

...was there supposed to be an attachment showing said comment??? Otherwise, not sure how we can help.

 

[BUGGAR]

Sounds like the WASHDOT Geotechnical Design Manual and/or a memo related to it. I have a copy of the manual somewhere, or you can internet it.
Bob

 

[msquared48]

In thinking further on this, I believe this was a Geotechnical addendum to an existing site specific Geotechnical report (that we never received) where the seismic coefficients were modified by the Geotech due to some local anomalies, hopefully to save money, which would mean lower values than the USGS values...

Great to be in the loop here!...

Client is going to love this one. I just hope the Seismic values we used are higher than the changes...

Luckily, the stairs have not been cast yet - any change would affect the connections, but not the stair reinforcing. Still...

My client has asked for the addendum. We'll see...

Mike McCann, PE, SE (WA)

 

[Settingsun]

Is it common for geotechnical engineers in your area to stick their necks out and recommend lower values than standard?

 

[msquared48]

Yes, Not uncommon.

Many anomalies in this area due to past glaciation and fault lines, known and unlnown.

Mike McCann, PE, SE (WA)

 

[BUGGAR]

When the geotech found the extension of the Spanish Bight Fault under the new aircraft carrier wharves in San Diego, they merely lowered the safety factor of their recommendations. But they already had safety factors on their safety factors so they had wiggle room.