LEBANESE UNIVERSITY
FACULTY OF ENGINEERING
BRANCH II - ROUMIEH
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Evaluation of the Static Seismic Base
Shear Using IBC 2012 and ASCE 7-10
Prepared by
Eng. Wassim J. Elias
Supervised by
Dr. Michel F. Khouri
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Introduction
The purpose of the earthquake
provisions herein is primarily to
safeguard against major structural
failures and loss of life, not to limit
damage or maintain function.
The seismic base shear V in a given
direction shall be determined in
accordance with the following equation:
V = Cs . W
Cs = the seismic response coefficient.
W = the effective seismic weight.
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Base Shear Distribution The lateral seismic force โFx"
induced at any level shall be determined
from the following equations:
๐ญ๐ = ๐ช๐๐ . ๐ฝ ๐ช๐๐ =๐๐. ๐๐
๐
๐๐๐๐๐๐
๐=๐
๐ = ๐. ๐๐ + ๐. ๐. ๐ป, ๐๐จ๐ซ ๐ฌ๐ญ๐ซ๐ฎ๐๐ญ๐ฎ๐ซ๐๐ฌ ๐ก๐๐ฏ๐ข๐ง๐ ๐ ๐ฉ๐๐ซ๐ข๐จ๐ "๐ป" ๐๐๐ญ๐ฐ๐๐๐ง
๐. ๐ ๐ฌ ๐๐ง๐ ๐. ๐ ๐ฌ.
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Calculation of the effective
seismic weight โWโ
๐พ = ๐พ๐
๐
๐=๐
๐ = ๐๐ข๐๐๐๐ ๐๐ ๐ ๐ก๐๐๐๐๐ .
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Calculation of the seismic
response coefficient Cs
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Calculation of the seismic
response coefficient Cs
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๐บ๐ซ๐ =๐
๐๐บ๐ด๐
Where, ๐บ๐ด๐=๐ญ๐. ๐บ๐ โ ๐น๐ฃ= ๐ก๐๐ ๐ ๐๐ก๐ ๐๐๐๐๐๐๐๐๐๐๐ก ๐๐๐๐๐๐๐ ๐๐ ๐ก๐๐ ๐๐๐๐๐๐ค๐๐๐ ๐ก๐๐๐๐:
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โ ๐1= ๐ก๐๐ ๐๐๐๐๐๐ ๐๐ถ๐ธ๐ ๐ ๐๐๐๐ก๐๐๐ ๐๐๐ ๐๐๐๐ ๐ ๐๐๐๐๐๐๐๐๐ก๐๐๐ ๐๐๐๐๐๐๐ก๐๐ ๐๐ก ๐ ๐๐๐๐๐๐ ๐๐ 1๐ .
User Note: Electronic values of mapped acceleration
parameters, and other seismic design parameters, are
provided at the USGS web site at:
http://geohazards.usgs.gov/designmaps/ww/.
or through the SEI Web site at:
http://content.seinstitute.org.
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Calculation of ๐๐ท๐
๐บ๐ซ๐บ =๐
๐๐บ๐ด๐บ
Where, ๐บ๐ด๐บ=๐ญ๐. ๐บ๐บ โ ๐น๐= ๐ก๐๐ ๐ ๐๐ก๐ ๐๐๐๐๐๐๐๐๐๐๐ก ๐๐๐๐๐๐๐ ๐๐ ๐ก๐๐
๐๐๐๐๐๐ค๐๐๐ ๐ก๐๐๐๐:
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Calculation of ๐๐ท๐
โ ๐๐= ๐ก๐๐ ๐๐๐๐๐๐ ๐๐ถ๐ธ๐ ๐ ๐๐๐๐ก๐๐๐ ๐๐๐ ๐๐๐๐ ๐ ๐๐๐๐๐๐๐๐๐ก๐๐๐ ๐๐๐๐๐๐๐ก๐๐ ๐๐ก ๐ ๐ ๐๐๐๐ก ๐๐๐๐๐๐๐ .
User Note: Electronic values of mapped acceleration
parameters, and other seismic design parameters, are
provided at the USGS web site at:
http://geohazards.usgs.gov/designmaps/ww/.
or through the SEI Web site at:
http://content.seinstitute.org.
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Site Classification
The site soil shall be classified in accordance with the
following table:
๐ฃ๐ ๐ =๐บ๐๐๐ ๐
๐บ๐ =๐ธ๐
2(1 + ๐๐)
โ ๐บ๐= Soil Shear Modulus.
โ ๐๐ ๐= Soil Density. โ ๐๐= Poisson Coefficient. 12
Site Classification
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Risk Category of Structures The risk category of buildings and other structures for flood,
wind, snow, earthquake and ice loads can be chosen
according to the following table:
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Importance Factor and Seismic Design Category
SDC Calculation The importance factor by risk category of buildings and other structures for snow,
ice and earthquake loads can be chosen according to the following table:
The Seismic Design Category SDC can be chosen according to the following
table:
SDC=E when ๐1 โฅ 0.75 for risks categories I, II or III.
SDC=F when ๐1 โฅ 0.75 for risks categories IV.
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Response Modification Coefficient
โRโ Calculation The response modification coefficient R can be chosen
according to the following table:
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Response Modification Coefficient
โRโ Calculation
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Calculation of "T" the fundamental period of the structure
Where the values of approximate period parameters ๐ถ๐กand x
are given in the following table:
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Evaluation of "TL" the mapped long โ
period transition period
Where the values of mapped long-period transition period are
given in the following maps:
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Evaluation of "TL" the mapped long โ
period transition period
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Evaluation of "TL" the mapped long โ
period transition period
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Evaluation of "TL" the mapped long โ
period transition period
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Evaluation of "TL" the mapped long โ
period transition period
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Application on the IBC
2012 and ASCE 7-10
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Calculation of the effective
seismic weight โWโ
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๐บ๐ด๐=๐ญ๐. ๐บ๐ = ๐. ๐ โ ๐. ๐๐ = ๐. ๐๐ โ ๐น๐ฃ= ๐ก๐๐ ๐ ๐๐ก๐ ๐๐๐๐๐๐๐๐๐๐๐ก ๐๐๐๐๐๐๐ ๐๐ ๐ก๐๐ ๐ก๐๐๐๐ 11.4.2.
๐บ๐ซ๐ =๐
๐๐บ๐ด๐ =
๐
๐*1.36=0.91
๐บ๐ด๐บ=๐ญ๐. ๐บ๐บ=1*2.2=2.2
โ ๐น๐= ๐ก๐๐ ๐ ๐๐ก๐ ๐๐๐๐๐๐๐๐๐๐๐ก ๐๐๐๐๐๐๐ ๐๐ ๐ก๐๐ ๐ก๐๐๐๐ 11.4.1.
๐บ๐ซ๐บ =๐
๐๐บ๐ด๐บ=
๐
๐โ ๐. ๐ = ๐. ๐๐
Seismic Design Category SDC
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The Risk Category is II & Seismic Design Category
SDC=E, can be chosen according to the following tables 1.5-1 &
11.6-1,2:
Seismic Design Category SDC
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SDC=E when ๐1 โฅ 0.75 for risks categories I, II or III. SDC=F when ๐1 โฅ 0.75 for risks categories IV.
Seismic
Design
Category
SDC
&
Risk
Category
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Response
Modification
Coefficient
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The importance factor by risk category of buildings and other structures for snow,
ice and earthquake loads can be chosen according to the following table:
Importance Factor
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Where the values of approximate period parameters ๐ถ๐กand x
are given in the following table:
Period of the Structure
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Long-Period Transition Period of the Structure
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Seismic Response Coefficient Cs
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Calculation of the seismic
response coefficient Cs
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๐พ = ๐พ๐
๐
๐=๐
๐ = ๐๐ข๐๐๐๐ ๐๐ ๐ ๐ก๐๐๐๐๐ .
Effective Seismic Weight
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Base Shear & Lateral Seismic Forces
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Base Shear Distribution The lateral seismic force โFx" induced at
any level shall be determined from the
following equations:
๐ญ๐ = ๐ช๐๐ . ๐ฝ ๐ช๐๐ =๐๐. ๐๐
๐
๐๐๐๐๐๐
๐=๐
๐ = ๐. ๐๐ + ๐. ๐. ๐ป, ๐๐จ๐ซ ๐ฌ๐ญ๐ซ๐ฎ๐๐ญ๐ฎ๐ซ๐๐ฌ ๐ก๐๐ฏ๐ข๐ง๐ ๐ ๐ฉ๐๐ซ๐ข๐จ๐ "๐ป" ๐๐๐ญ๐ฐ๐๐๐ง
๐. ๐ ๐ฌ ๐๐ง๐ ๐. ๐ ๐ฌ.
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Static Base Shear UBC97 Berkeley city seismic zone is 4 (Z=0.4) according to
the following seismic zone map of USA:
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Static Base Shear UBC97
๐ฝ๐ผ๐ฉ๐ช๐๐ =๐ช๐ฝ.๐ฐ.๐พ
๐น.๐ป =๐.๐๐โ๐โ๐๐๐๐
๐.๐โ๐.๐๐= ๐๐๐๐ ๐ฒ๐๐๐.
* The soil profile is Sd the seismic coefficient Cv=0.64*Nv (Table
16-R) where Nv=1 (Table 16-T) for a seismic source type Aโฅ 15 ๐พ๐.
* The occupancy Category is I=1 (Table 16-K).
* W= Total Structure Construction Weight = 9655 Kips.
* T= the structure period =๐ถ๐ก . ๐๐34 =0.03* 52
34 =0.58 s.
* ๐ถ๐ก=0.030 for reinforced concrete moment resisting frames and
eccentrically braced frames.
* R=Coefficient of the inherent over strength and global ductility = 8.
5 for SMRF (Table 16-N).
๐ฝ๐ฐ๐ฉ๐ช๐๐๐๐ = ๐ช๐บ.๐พ =0.18*9655 =1738 Kips.
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