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RE: www.seismicfactor.com

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Bill,
The site does not actually determine the actual Ss and S1 values from the
address input or the zip code. It is nice in the sense that it calculate or
looks-up the Site latitude and Longitude based on the actual address give
(even without entering the Zip code), but it does not determine the Site
Class (nor does the USGS software). Bother require the user to input the
Site Class and Occupancy Category.

The fault in the web tool is that it does not automatically tell the user if
he or she has exceeded the allowable building height limits since it appears
that the tool is intended to be restricted to two family or less
light-framed residential. If the user inputs a height of 650 feet, it will
calculate the Approximate Fundamental Period, but will not warn the user
that the building height he or she entered is not permitted under the
provisions of table 12.2-1 and for other conditions the user needs to
consider the Overstrength Factors as well as the redundancy factor that
changes when less than 35% of the base shear is distributed to any diaphragm
level.

The problem with tools like this is not so much the author, but the user who
will accept the results without verification or understanding of the code
methods. Yes, there are other requirements that must be considered and at
the very least, the author should have entered the appropriate boiler plate
or performed sufficient beta testing.

The USGS software is specific to the site conditions and does not calculate
the minimum base shear. This program should probably have stopped at the
same results that the USGS software produces since it goes one step better
than the USGS software. The USGS software defaults to a soil classification
of type B. The user has to remember to increase the Soil Class to a minimum
of 'D' depending on the site location or geotechnical report. If the tool
wants to go further than this, then the author should be warning the user to
verify the results and to take responsibility for the output being adequate
or accurate for the site that he or she is working with. This holds true of
most software out there.

I'm not attempting to disparage the software because the ability to input
the address and have it determine the accurate Ss, S1, Fa, Fv, Sds, Sd1, Sms
and Sm1 is still worthwhile and a time saver. I'm curious as I would like to
be able to learn how to institute something like this into my spreadsheet
which requires the user to use a secondary (albeit free) tool such as the
USGS Java software and Google Earth.

>From a learning perspective, it would be a value to the professional
community as long as it is clear that the program may produce inaccurate
results when limits are exceeded. I am never one who would discourage anyone
who is willing to share his education on creating tools that we can use to
assist our work.

There is not one software on the market that I would use without questioning
or testing the accuracy. This is our responsibility as a professional
community and the majority of boiler plates on the best software out there
warns the user of potential bugs or inaccurate results if input limits are
not clearly understood. 

Dennis
  

-----Original Message-----
From: xmy987 [mailto:xmy987(--nospam--at)gmail.com] 
Sent: Friday, June 27, 2008 11:24 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: www.seismicfactor.com

Actually Gordon, www.seismicfactor.com does not use the zip code average. It
is obtains specific Ss and S1 based on the actual address. I know many
programs out there use the zip code average which can result in seismic
coefficients being off by as much as 40 percent. I use it regularly and
found it quite reliable and saves me quite a few steps.

Bill

-----Original Message-----
From: Gordon Goodell [mailto:GordonGoodell(--nospam--at)harmonydesigninc.com] 
Sent: Friday, June 27, 2008 10:56 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: www.seismicfactor.com

Exactly what I was looking for.  Thank you.

Gordon



<<I map the address in Google Maps to get the lat/lon.  Then I use the
USGS tool to get the design values.

You can get it here:

http://earthquake.usgs.gov/research/hazmaps/design/index.php

Chris>>




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