Seismic site classes for AZ and CA 1

[azTNT]

I am looking for the source of maximum allowable soil bearing pressures i can use without a soil investigation and report. I've only been able to find the requirements spelled out in one or two cities in these two states. Is there a good website or source that would end my frustration with the lack of info spelled out by the state.

 

[oldrunner]

Soils in California vary from 500 psf to 5000 psf. Take your pick.

Soil investigations are only good for the particular site where your project is. I would recommend that you engage a local geotechnical engineer for the area where your project is.

I don't know what your frustration should be about. All civil and structural engineers are cognizant of the soils issue. We do no projects without a soil report.

Did a job once where we were told that the ground was good for 3000 psf. After the structure started to tilt, a very quick boring of the ground found that we had 95 feet of mud.

 

[whyun]

Use the lowest allowable pressure listed in the building code adopted by your local building department. To have the benefit of higher bearing pressure, you need the expertise of a geotechnical engineer to sign off on a higher value.

 

[azcats]

The no-soils-report value that I've used in AZ (mainly the Phoenix Metro area) has been 1500 psf.

 

[skier1578]

Ca has adopted the 2001 CBC (1997 UBC with a fancy new cover), it allows 1000psf max. bearing w/out a soils report.

 

[minorchord2000]

Without a soils report, the local building code department allows us to use 1500 psf max. This can cause very inefficient designs especially for retaining walls. The often unstated goal of the IBC these days is to get a soils report for everything now.

If you have to design a project without a soils report, check with you local agency about what values they would allow. This includes lateral EFP and passive pressure values.

 

[PTslab]

Soil bearing pressures in the Phoenix metro are typically 1500 psf at 1'-6" below grade for natural undisturbed soil (500 psf per 6" depth) Pockets of bad material can be found all around. You should also be aware that you will need to classify the soil per IBC 2003 as some soil in the valley is fill (not native) which does not meet that code assumption. At a minimum, get a classification of the soils.

 

[eric1037]

Why is there always so much resistance to getting a geotechnical report? This is common throughout the nation. The cost and timing of such an investigation is minimal in comparison to the total project budget and schedule.

Sorry, but engineers should know better.

Now that I am off my soapbox, I would suggest contacting the local building official where the project will be located. I have encountered some building officials that will not grant a building permit without a geotechnical report regardless of what the code says.