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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Joe,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>The return period defined in the national
seismic hazard mapping is not comparable to the mean recurrence intervals of
flood, wind, and other natural hazards. This may be one of the reasons that the
users have difficulty to select design ground motions. Attached are comments on
the national seismic hazard maps (2007 update).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Zhenming <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
ceus-earthquake-hazards-bounces@geohazards.usgs.gov
[mailto:ceus-earthquake-hazards-bounces@geohazards.usgs.gov] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Joe Tomasello<br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, January 19, 2008
3:17 PM<br>
<b><span style='font-weight:bold'>To:</span></b> afrankel@usgs.gov;
ceus-earthquake-hazards@geohazards.cr.usgs.gov; 'Seth Stein'<br>
<b><span style='font-weight:bold'>Subject:</span></b> [CEUS-earthquake-hazards]
The balance</span></font><font size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Art:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>I’m sorry for delaying my response, my time isn’t always mine. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Your evaluation is essentially correct, my previous evaluation was an
overly simplified evaluation (equation 16.56) and didn’t properly reflect the
topic. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>It was never a question of which code to pick as a baseline. I don’t
hold the view that the 99 SBC has any particular advantage over the IBC (except
that it’s easier to use from a designer’s standpoint). The lower base shear
found in the 03 IBC with <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
amendments reflects the level of hazard for 1:500 return period shown on the
1996 maps your prepared for NEHRP. The 1:500 return period is a traditionally
accepted level of hazard found to be appropriate for building with a 50 year
life. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Recurrence periods for performance levels of natural hazards except for
earthquake are 500 years or less (ASCE – 7.02):<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Local Flooding
100-year<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Regional Flooding
500-year<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Snow
Loading
50-year<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Wind Loads
500-year (previously 100-years)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Rain
Loads
10-year<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Ice
Loads
50-year<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Thus we found the use of a recurrence interval 50 times greater than
the statistical life of the building to be meaningless – in effect becoming a
level of hazard matching the maximum probable event. This is a level of
hazard seldom used for the design of any structure. As an example, the
level of hazard used for the <st1:place w:st="on"><st1:PlaceName w:st="on">Hernando</st1:PlaceName>
<st1:PlaceName w:st="on">Desoto</st1:PlaceName> <st1:PlaceType w:st="on">Bridge</st1:PlaceType></st1:place>
seismic retrofit was substantially less; in spite of its importance to the
region. The <st1:State w:st="on"><st1:place w:st="on">Tennessee</st1:place></st1:State>’s
Department of Transportation’s structural engineer told me that the reason for
not meeting the 1:2500 year criterion was the cost. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>The difference between 10%PE maps in the 99 SBC and the 10%PE maps
found in 03 IBC reflects the improved state knowledge of your maps over the SBC
maps. The 10%PE 03 maps reflect the earthquake hazard perceived by the public
in this region. The <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
amendments encourage the building owner to build to a level that best reflects
his sensitivity to casualty and property loss.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>However, in the event that the 99 SBC was used as a baseline code,
you’d find that the differences between 99 SBC and the 03 IBC are quite
different depending on location in the county and the height of the building.
Using only 100 foot tall buildings skews the conclusions. The
predominance of the buildings in the county are less than 5 stories. And those
in the Northwest portions of the county are almost exclusively 1 and 2 story
buildings. Outside of downtown <st1:City w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City>
any building in excess of 5 stories is unusual. Therefore we added weight
to the impact to the shorter building more than to the taller buildings.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Looking at a cross section of buildings across the county we found the
following in <st1:place w:st="on"><st1:PlaceName w:st="on">Shelby</st1:PlaceName>
<st1:PlaceName w:st="on">County</st1:PlaceName></st1:place>:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Table 1<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>03IBC(Mem.)/99SBC<o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:PlaceName w:st="on"><font size=2
face="Times New Roman"><span style='font-size:11.0pt'>Shelby</span></font></st1:PlaceName>
<st1:PlaceName w:st="on">County</st1:PlaceName></st1:place>
2-story
5-story
10-story<o:p></o:p></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Southeast
0.90
0.77
0.61<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Middle
0.94
0.70
0.56<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Northwest
0.94
0.75
0.60<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Since we are using the 99 SBC as a baseline code it would only be fare
to compare the 03IBC (without amendments) versus the 99 SBC. See the evaluation
below.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Table 2<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>03IBC/99SBC<o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:PlaceName w:st="on"><font size=2
face="Times New Roman"><span style='font-size:11.0pt'>Shelby</span></font></st1:PlaceName>
<st1:PlaceName w:st="on">County</st1:PlaceName></st1:place>
2-story
5-story
10-story<o:p></o:p></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Southeast
1.73
2.47
1.96<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Middle
1.87
2.94
2.33<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Northwest
2.91
4.77
3.79<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>These tables, like your evaluation, assumed the Response factor did not
contribute to the evaluation, and we used a D Site Class (the dominant Site
Class in the county.) Even still, in order properly evaluate the differences in
the code the resultant base shears should include redundancy and overload
factors prescribed differently in the IBC than in the SBC. The
overstrength factor, usually 2 or 3 applies all cases equally, while in most
cases the redundancy factor would not apply to table 1. A conservative
multiplier for all the entries in both tables would be 1.5. In so doing
we see that the differences between 03 IBC (MEM) versus 99 SBC become
relatively small. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Because of these differences illustrate in Table 2, <st1:City
w:st="on"><st1:place w:st="on">Memphis</st1:place></st1:City> elected to
utilize all three codes, the 03 IBC with amendments to the map, the 99 SBC, and
the 03 IBC without the amendments. This best represented the perceived
hazard, and allowed the building owner to select the code that best represented
his threshold of risk. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'>Considering the above whys is USGS opposed to individual communities to
selecting their own seismic risk? </span></font><font color="#1f497d"
face=Arial><span style='font-family:Arial;color:#1F497D'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face="Times New Roman"><span style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><b><font size=3 face=Arial><span style='font-size:12.0pt;
font-family:Arial;font-weight:bold'>Joseph Tomasello, PE</span></font></b><font
size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:Street w:st="on"><st1:address w:st="on"><b><font
size=3 face=Arial><span style='font-size:12.0pt;font-family:Arial;font-weight:
bold'>5880 Ridge Bend Rd.</span></font></b></st1:address></st1:Street><font
size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:City w:st="on"><b><font size=3
face=Arial><span style='font-size:12.0pt;font-family:Arial;font-weight:bold'>Memphis</span></font></b></st1:City><b><font
size=3 face=Arial><span style='font-size:12.0pt;font-family:Arial;font-weight:
bold'>, <st1:State w:st="on">TN</st1:State> <st1:PostalCode w:st="on">38120</st1:PostalCode></span></font></b></st1:place><font
size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=MsoNormal><b><font size=3 face=Arial><span style='font-size:12.0pt;
font-family:Arial;font-weight:bold'>Phone:</span></font></b><font size=3><span
style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><b><font size=3 face=Arial><span style='font-size:12.0pt;
font-family:Arial;font-weight:bold'>(901) 761-2016 office</span></font></b><font
size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><b><font size=3 face=Arial><span style='font-size:12.0pt;
font-family:Arial;font-weight:bold'>(901) 821-4968 direct</span></font></b><font
size=3><span style='font-size:12.0pt'><o:p></o:p></span></font></p>
<p class=MsoNormal><b><font size=3 face=Arial><span style='font-size:12.0pt;
font-family:Arial;font-weight:bold'>(901) 412-8217 mobile</span></font></b><o:p></o:p></p>
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