Design Code Lecture
April 25, 2013
International Building Code
Seismic Provisions
CEE 572 Earthquake Engineering
Lecture Notes:
Prof/ Amr S. Elnashai
Mid-America Earthquake Center
Prepared by:
Dr./ DoSoo Moon
Building Code
 A set of rules that specify the minimum acceptable level of
safety for constructed objects such as buildings
 No legal status until it is adopted by government regulation
 International Building Code (IBC)


a model building code developed by the International Code
Council (ICC)
minimum standards to insure the public safety, health and
welfare insofar as they are affected by building construction
and to secure safety to life and property from all hazards
incident to the occupancy of buildings, structures or premises
2
Building Code History
 first seen in the United States in the early 1700’s
 In the early 1900’s, local code enforcement officials
developed most of the building codes

In 1915, Building Officials and Code Administration (BOCA) was
established, and developed the BOCA National Building Code
(BOCA/NBC)
- mainly used in the Northeastern United States

In 1927, the International Conference of Building Officials (ICBO) was
established, and developed the Uniform Building Code (UBC)
- mainly used in the Midwest and Western United States

In 1940, the Southern Building Code Congress International (SBCCI)
was founded, and developed the Standard Building Code (SBC)
- mainly used in the Southern United States
3
Building Code History
 Over the years each of these codes (BOCA/NBC, UBC, & SBC)
was revised and updated
 In 1994, BOCA, ICBO, and SBCCI formed International Code
Council (ICC)
 In 1997, the first edition of the International Building Code (IBC)
was published by ICC
 IBC is updated every 3 year
( 1997, 2000, 2003, 2006, 2009, 2012)
4
IBC
IBC 2009
BOCA/NBC
- BOCA
UBC
- ICBO
SBC
- SBCCI
IBC
- ICC
every 3 year
( 1997, 2000, 2003,
2006, 2009, 2012 )
5
IBC Adoption by State
IBC is adopted at the state or local level in 50 states plus Washington, D.C
http://www.iccsafe.org/gr/Pages/adoptions.aspx
as of 04/20/2010
6
IBC Code Structure
 arranged in a systematic manner for easy reference
 35 Chapters and 11 Appendices (684 pages)
7
IBC Section 1613 Earthquake Loads
“ Every structure, and portion thereof, including nonstructural
components that are permanently attached to structures and
their supports at attachments, shall be designed and
constructed in accordance with ASCE 7, excluding Chapter 14
and Appendix 11A. The seismic design category for a structure
is permitted to be determined in accordance with Section 1613 or
ASCE 7.”
(ASCE 7 Chapter 14 contains Material-Specific Seismic Design and
Detail Requirements)
(ASCE 7 Appendix 11A contains Quality Assurance Provisions)
 Both are replaced by similar (not identical) IBC Provisions
8
ASCE 7
 Minimum Design Loads for
Buildings and Other Structures
 Developed by ASCE/SEI
 Publication Date Varies (1993,
1995, 1998, 2002, 2005, 2010)
 ASCE 7-05 is adopted by IBC 2009
 ASCE 7-10 is adopted by IBC 2012
9
Seismic Design Procedure
Occupancy Category
& Importance Factor, I
Min. permissible analysis proc.
MCE Spectral Accel., SS& S1
Equivalent Lateral Force
Site Class (A ~F)
- Seismic Base Shear
- Vertical Distribution
- Horizontal Distribution
Site Coef., Fa & Fv
Response Modification Factor, R
Adjusted MCE Accel, SMS & SM1
Structure Period, T
Design Values, SDS & SD1
Diaphragms, Irregularity,
Redundancy Factor
Seismic Design Category (A~F)
Drift and Deformation
10
Seismic Design Category (SDC)
Structure Occupancy
Category
Structure Importance
Factor, I
Structure Location
SS, S1
(Hazard Map)
SMS, SM1
(Site Soil Condition)
SDS, SD1
(Design Values)
SDC
(Occupancy Category & SDS or SD1)
11
Occupancy Category and Importance Factor
Nature of
Occupancy
Minor storage, agricultural & temporary facilities
Occupancy
Category
Importance
Factor
I
I
1.0
Normal Buildings
II
Substantial hazard to human life:
• Schools
• Public assembly >300 occupants
• Jails & detention facilities
• Some types of healthcare > 50 occup.
• Power-generation, water-treatment facilities
• Any building > 5,000 occupants
• Hazardous occupancies
III
1.25
IV
1.50
Essential facilities:
• Hospitals, Fire, rescue, & police stations
• Emergency preparedness centers, & more
12
Seismic Ground Motion Values - SS, S1, SMS, SM1, SDS, SD1
 Traditional 10%/50 yr (475-year event) is history
 ASCE 7-05 uses 2/3 of the 2%/50 yr (2,500 year event)
 Ss and S1 : map values of 2,500 year event

Maps assume Type B (rock) soil conditions
 SMS and SM1 : 2,500 year values adjusted for design soil
conditions by coefficients Fa and Fv

Default soil is Type D
 SDS= 2/3 SMS and SD1= 2/3 SM1 : design values

SS, S1 values are invisibly converted from a 2,500-year “probabilistic”
event to a “deterministic” event defined as “150% of the median
accelerations of the characteristic event.”
13
MCE ground motion, SS ,S1
 Seismic Hazard Map




Response spectrum ordinates are mapped
Near-fault effects are included in basic maps
Data is “location-specific”
Soil effects still handled separately  Site Coef. Fa & FV
 Maximum Considered Earthquake (MCE) ground motion


Ss = Mapped 5% damped, spectral response acceleration
parameter at short periods (0.2 sec)
S1 = Mapped 5% damped spectral response acceleration
parameter at a period of 1 sec.
─ Use Seismic Hazard Map
─ Use online tool at http://eqhazmaps.usgs.gov
14
Seismic Hazard Map
 The contours are irregularly spaced
 Values are in % of g
15
Adjusted MCE ground motion, SMS ,SM1
 SMS = FaSS ,
SM1 = FvS1
Site Coef.
Fa 
Site Coef.
FV 
16
Site Class
default
softer
17
Design Values, SDS ,SD1
 SDS = 2/3SMS ,
SD1 = 2/3 SM1

SDS : the design, 5% damped, spectral
response acceleration for short periods
(0.2 sec)

SD1 : the design, 5% damped, spectral
response acceleration at a period of 1 sec
 SDS and SD1 are used in selecting the
Seismic Design Category and in the
analysis methods.
18
Spectral Response Acceleration , Sa (g)
Design Response Spectrum
SDS
Sa=SD1/T
SD1
Sa=SD1TL/T2
0.4SDS
T0
=0.2SD1/SDS
Ts
=SD1/SDS
1.0
TL
Period, T (sec)
19
Summary of Ground Motion Values
Structure Location
 Hazard Map
 Site class, SS and S1


SS, S1
SS, S1
(Hazard Map)
Fa, Fv
 SMS = Fa  SS
SMS, SM1
(Site Soil Condition)
SM1 = FV  S1
 SDS = 2/3  SMS
SD1 = 2/3  SM1
 Design !!
SDS, SD1
(Design Values)
20
Seismic Design Category (SDC)
 Every structure must be assigned to a SDC
 Function of:

Occupancy Category

Design Spectral Response Acceleration SDS and SD1
 Used to determine analysis options, detailed requirements, height
limitations, and other limits on usage.
 Seismic Design Categories labeled A-F (6 class)
21
SDC” A–F vs. “Site Class” A-F
 will cause confusion
 Site Class = Soil Type

Default site class = D
 Seismic Design Category = SDC

Defines structure detailing requirements

Limits permissible structural irregularities

Replaces Zone-dependent detailing
22
Seismic Design Procedure
Occupancy Category
& Importance Factor, I
Min. permissible analysis proc.
MCE Spectral Accel., SS& S1
Equivalent Lateral Force
Site Class (A ~F)
- Seismic Base Shear
- Vertical Distribution
- Horizontal Distribution
Site Coef., Fa & Fv
Response Modification Factor, R
Adjusted MCE Accel, SMS & SM1
Structure Period, T
Design Values, SDS & SD1
Diaphragms, Irregularity,
Redundancy Factor
Seismic Design Category (A~F)
Drift and Deformation
23
Analysis Procedure Selection
24
Seismic Load Analysis Procedures
 Equivalent Lateral Force (ELF) – Section 12.8

Static approximation

May not be used on structures of Seismic Design
Categories E or F with particular irregularities
 Modal Response Spectrum Analysis – Section 12.9

2D and 3D dynamic analysis

Required for buildings with particular irregularities
 Seismic Response History Procedure – Chapter 16

Permitted for all structures
25
Minimum Lateral Force – SDC A
 Very limited seismic exposure and risk
 Lateral forces taken to equal 1% of structure weight
Fx=0.01wx
Fx = the design lateral force applied at story x
wx = the portion of the total dead load of the structure,
D, located or assigned to Level x
 A complete load path must be in place
26
Equivalent Lateral Force (ELF)
 Base Shear Determination
V = CsW
Cs = I/R  SDS
Cs = seismic response coefficient
W = the effective seismic weight, including applicable portions of other
storage and snow loads
 Seismic Weight, W

all dead load

25% of any design storage floor live loads

Consider partition loads and snow load
27
Equivalent Lateral Force (ELF)
 Seismic Response Coefficient, Cs
• 0.01
for S1 < 0.6g
• 0.5S1(I/R)
for S1 > 0.6g
<
Cs = SDS  (I/R)
<
• SD1/T(I/R)
for T < TL
• SD1TL/T2(I/R)
for T > TL
SDS = design spectral response acceleration parameter
R = response modification factor
I = occupancy importance factor
TL = long period transition periods, 8 or 12 sec
28
Response Modification Coefficient, R
Cs = SDS  (I/R)
 accounts for the dynamic characteristics, lateral force resistance,
and energy dissipation capacity of the structural system.
 can be different for different directions
29
MINIMUM DESIGN LOADS
Table 12.2-1 Design Coefficients and Factors for Seismic Force-Resisting Systems
ASCE 7
Section
Response
Where
Modification
Detailing
Deflection
Requirements Coefficient, Overstrength Amplification
Ra
Are Specified
Factor, Cdb
Factor, Ω0g
Seismic Force-Resisting System
Structural System
Limitations Including
Structural Height, hn (ft)
Limitsc
Seismic Design Category
B
C
Dd
Ed
Fe
A. BEARING WALL SYSTEMS
1. Special reinforced concrete shear
wallsl, m
14.2
5
2½
5
NL
NL
160 160
100
2. Ordinary reinforced concrete shear
wallsl
14.2
4
2½
4
NL
NL
NP
NP
NP
14.2
2
2½
2
NL
NP
NP
NP
NP
14.2
1½
2½
1½
NL
NP
NP
NP
NP
k
40
k
40k
3. Detailed plain concrete shear wallsl
l
4. Ordinary plain concrete shear walls
l
14.2
4
2½
4
NL
NL
40
14.2
3
2½
3
NL
NP
NP
NP
NP
7. Special reinforced masonry shear walls 14.4
5
2½
3½
NL
NL
160 160
100
8. Intermediate reinforced masonry shear
walls
14.4
3½
2½
2¼
NL
NL
NP
NP
NP
9. Ordinary reinforced masonry shear
walls
14.4
2
2½
1¾
NL
160 NP
NP
NP
10. Detailed plain masonry shear walls
14.4
2
2½
1¾
NL
NP
NP
NP
NP
11. Ordinary plain masonry shear walls
14.4
1½
2½
1¼
NL
NP
NP
NP
NP
12. Prestressed masonry shear walls
14.4
1½
2½
1¾
NL
NP
NP
NP
NP
13. Ordinary reinforced AAC masonry
shear walls
14.4
2
2½
2
NL
35
NP
NP
NP
14. Ordinary plain AAC masonry shear
walls
14.4
1½
2½
1½
NL
NP
NP
NP
NP
15. Light-frame (wood) walls sheathed
with wood structural panels rated for
shear resistance or steel sheets
14.1 and 14.5 6½
3
4
NL
NL
65
65
65
16. Light-frame (cold-formed steel) walls
sheathed with wood structural panels
rated for shear resistance or steel
sheets
14.1
3
4
NL
NL
65
65
65
17. Light-frame walls with shear panels of
all other materials
14.1 and 14.5 2
2½
2
NL
NL
35
NP
NP
18. Light-frame (cold-formed steel) wall
systems using flat strap bracing
14.1
4
2
3½
NL
NL
65
65
65
1. Steel eccentrically braced frames
14.1
8
2
4
NL
NL
160 160
100
2. Steel special concentrically braced
frames
14.1
6
2
5
NL
NL
160 160
100
3. Steel ordinary concentrically braced
frames
14.1
3¼
2
3¼
NL
NL
35j
NPj
5. Intermediate precast shear walls
l
6. Ordinary precast shear walls
6½
B. BUILDING FRAME SYSTEMS
35j
Continued
73
CHAPTER 12
SEISMIC DESIGN REQUIREMENTS FOR BUILDING STRUCTURES
Table 12.2-1 (Continued)
ASCE 7
Section
Response
Where
Modification
Detailing
Deflection
Requirements Coefficient, Overstrength Amplification
Ra
Are Specified
Factor, Cdb
Factor, Ω0g
Seismic Force-Resisting System
4. Special reinforced concrete shear
wallsl,m
Structural System
Limitations Including
Structural Height, hn (ft)
Limitsc
Seismic Design Category
B
C
Dd
Ed
Fe
14.2
6
2½
5
NL
NL
160 160
100
5. Ordinary reinforced concrete shear wallsl 14.2
5
2½
4½
NL
NL
NP
NP
NP
l
6. Detailed plain concrete shear walls
14.2 and
14.2.2.8
2
2½
2
NL
NP
NP
NP
NP
7. Ordinary plain concrete shear wallsl
14.2
1½
2½
1½
NL
NP
NP
NP
NP
k
40
k
40k
l
8. Intermediate precast shear walls
14.2
5
2½
4½
NL
NL
40
9. Ordinary precast shear wallsl
14.2
4
2½
4
NL
NP
NP
NP
NP
10. Steel and concrete composite
eccentrically braced frames
14.3
8
2½
4
NL
NL
160 160
100
11. Steel and concrete composite special
concentrically braced frames
14.3
5
2
4½
NL
NL
160 160
100
12. Steel and concrete composite ordinary
braced frames
14.3
3
2
3
NL
NL
NP
NP
NP
13. Steel and concrete composite plate
shear walls
14.3
6½
2½
5½
NL
NL
160 160
100
14. Steel and concrete composite special
shear walls
14.3
6
2½
5
NL
NL
160 160
100
15. Steel and concrete composite ordinary
shear walls
14.3
5
2½
4½
NL
NL
NP
NP
NP
16. Special reinforced masonry shear walls 14.4
5½
2½
4
NL
NL
160 160
100
17. Intermediate reinforced masonry shear
walls
14.4
4
2½
4
NL
NL
NP
NP
NP
18. Ordinary reinforced masonry shear
walls
14.4
2
2½
2
NL
160 NP
NP
NP
19. Detailed plain masonry shear walls
14.4
2
2½
2
NL
NP
NP
NP
NP
20. Ordinary plain masonry shear walls
14.4
1½
2½
1¼
NL
NP
NP
NP
NP
21. Prestressed masonry shear walls
14.4
1½
2½
1¾
NL
NP
NP
NP
NP
22. Light-frame (wood) walls sheathed
with wood structural panels rated for
shear resistance
14.5
7
2½
4½
NL
NL
65
65
65
23. Light-frame (cold-formed steel) walls
sheathed with wood structural panels
rated for shear resistance or steel sheets
14.1
7
2½
4½
NL
NL
65
65
65
24. Light-frame walls with shear panels of
all other materials
14.1and 14.5
2½
2½
2½
NL
NL
35
NP
NP
25. Steel buckling-restrained braced
frames
14.1
8
2½
5
NL
NL
160 160
100
26. Steel special plate shear walls
14.1
7
2
6
NL
NL
160 160
100
74
MINIMUM DESIGN LOADS
Table 12.2-1 (Continued)
Seismic Force-Resisting System
ASCE 7
Section
Response
Where
Modification
Detailing
Deflection
Requirements Coefficient, Overstrength Amplification
Ra
Are Specified
Factor, Cdb
Factor, Ω0g
Structural System
Limitations Including
Structural Height, hn (ft)
Limitsc
Seismic Design Category
B
C
Dd
Ed
Fe
C. MOMENT-RESISTING FRAME
SYSTEMS
1. Steel special moment frames
14.1 and
12.2.5.5
8
3
5½
NL
NL
NL
NL
NL
2. Steel special truss moment frames
14.1
7
3
5½
NL
NL
160 100
NP
h
h
3. Steel intermediate moment frames
12.2.5.7 and
14.1
4½
3
4
NL
NL
35
NP
NPh
4. Steel ordinary moment frames
12.2.5.6 and
14.1
3½
3
3
NL
NL
NPi
NPi
NPi
5. Special reinforced concrete moment
framesn
12.2.5.5 and
14.2
8
3
5½
NL
NL
NL
NL
NL
6. Intermediate reinforced concrete
moment frames
14.2
5
3
4½
NL
NL
NP
NP
NP
7. Ordinary reinforced concrete moment
frames
14.2
3
3
2½
NL
NP
NP
NP
NP
8. Steel and concrete composite special
moment frames
12.2.5.5 and
14.3
8
3
5½
NL
NL
NL
NL
NL
9. Steel and concrete composite
intermediate moment frames
14.3
5
3
4½
NL
NL
NP
NP
NP
10. Steel and concrete composite partially
restrained moment frames
14.3
6
3
5½
160 160 100 NP
NP
11. Steel and concrete composite ordinary
moment frames
14.3
3
3
2½
NL
NP
NP
NP
NP
12. Cold-formed steel—special bolted
moment framep
14.1
3½
3o
3½
35
35
35
35
35
D. DUAL SYSTEMS WITH SPECIAL 12.2.5.1
MOMENT FRAMES CAPABLE OF
RESISTING AT LEAST 25% OF
PRESCRIBED SEISMIC FORCES
1. Steel eccentrically braced frames
14.1
8
2½
4
NL
NL
NL
NL
NL
2. Steel special concentrically braced
frames
14.1
7
2½
5½
NL
NL
NL
NL
NL
3. Special reinforced concrete shear wallsl 14.2
7
2½
5½
NL
NL
NL
NL
NL
4. Ordinary reinforced concrete shear
wallsl
14.2
6
2½
5
NL
NL
NP
NP
NP
5. Steel and concrete composite
eccentrically braced frames
14.3
8
2½
4
NL
NL
NL
NL
NL
6. Steel and concrete composite special
concentrically braced frames
14.3
6
2½
5
NL
NL
NL
NL
NL
Continued
75
CHAPTER 12
SEISMIC DESIGN REQUIREMENTS FOR BUILDING STRUCTURES
Table 12.2-1 (Continued)
Seismic Force-Resisting System
ASCE 7
Section
Response
Where
Modification
Detailing
Deflection
Requirements Coefficient, Overstrength Amplification
Ra
Are Specified
Factor, Cdb
Factor, Ω0g
Structural System
Limitations Including
Structural Height, hn (ft)
Limitsc
Seismic Design Category
B
C
Dd
Ed
Fe
7. Steel and concrete composite plate
shear walls
14.3
7½
2½
6
NL
NL
NL
NL
NL
8. Steel and concrete composite special
shear walls
14.3
7
2½
6
NL
NL
NL
NL
NL
9. Steel and concrete composite ordinary
shear walls
14.3
6
2½
5
NL
NL
NP
NP
NP
10. Special reinforced masonry shear walls 14.4
5½
3
5
NL
NL
NL
NL
NL
11. Intermediate reinforced masonry shear
walls
14.4
4
3
3½
NL
NL
NP
NP
NP
12. Steel buckling-restrained braced
frames
14.1
8
2½
5
NL
NL
NL
NL
NL
13. Steel special plate shear walls
14.1
8
2½
6½
NL
NL
NL
NL
NL
E. DUAL SYSTEMS WITH
INTERMEDIATE MOMENT
FRAMES CAPABLE OF
RESISTING AT LEAST 25% OF
PRESCRIBED SEISMIC FORCES
12.2.5.1
6
2½
5
NL
NL
35
NP
NP
2. Special reinforced concrete shear wallsl 14.2
6½
2½
5
NL
NL
160 100
100
3. Ordinary reinforced masonry shear
walls
14.4
3
3
2½
NL
160 NP
NP
NP
4. Intermediate reinforced masonry shear
walls
14.4
3½
3
3
NL
NL
NP
NP
NP
5. Steel and concrete composite special
concentrically braced frames
14.3
5½
2½
4½
NL
NL
160 100
NP
6. Steel and concrete composite ordinary
braced frames
14.3
3½
2½
3
NL
NL
NP
NP
NP
7. Steel and concrete composite ordinary
shear walls
14.3
5
3
4½
NL
NL
NP
NP
NP
8. Ordinary reinforced concrete shear
wallsl
14.2
5½
2½
4½
NL
NL
NP
NP
NP
12.2.5.8 and
14.2
4½
2½
4
NL
NP
NP
NP
NP
1. Steel special concentrically braced
framesf
F. SHEAR WALL-FRAME
INTERACTIVE SYSTEM WITH
ORDINARY REINFORCED
CONCRETE MOMENT FRAMES
AND ORDINARY REINFORCED
CONCRETE SHEAR WALLSl
76
14.1
MINIMUM DESIGN LOADS
Table 12.2-1 (Continued)
Seismic Force-Resisting System
G. CANTILEVERED COLUMN
SYSTEMS DETAILED TO
CONFORM TO THE
REQUIREMENTS FOR:
ASCE 7
Section
Response
Where
Modification
Detailing
Deflection
Requirements Coefficient, Overstrength Amplification
Ra
Are Specified
Factor, Cdb
Factor, Ω0g
Structural System
Limitations Including
Structural Height, hn (ft)
Limitsc
Seismic Design Category
B
C
Dd
Ed
Fe
12.2.5.2
1. Steel special cantilever column
systems
14.1
2½
1¼
2½
35
35
35
35
35
2. Steel ordinary cantilever column
systems
14.1
1¼
1¼
1¼
35
35
NPi
NPi
NPi
3. Special reinforced concrete moment
framesn
12.2.5.5 and
14.2
2½
1¼
2½
35
35
35
35
35
4. Intermediate reinforced concrete
moment frames
14.2
1½
1¼
1½
35
35
NP
NP
NP
5. Ordinary reinforced concrete moment
frames
14.2
1
1¼
1
35
NP
NP
NP
NP
6. Timber frames
14.5
1½
1½
1½
35
35
35
NP
NP
14.1
3
3
3
NL
NL
NP
NP
NP
H. STEEL SYSTEMS NOT
SPECIFICALLY DETAILED FOR
SEISMIC RESISTANCE,
EXCLUDING CANTILEVER
COLUMN SYSTEMS
a
Response modification coefficient, R, for use throughout the standard. Note R reduces forces to a strength level, not an allowable stress level.
Deflection amplification factor, Cd, for use in Sections 12.8.6, 12.8.7, and 12.9.2.
c
NL = Not Limited and NP = Not Permitted. For metric units use 30.5 m for 100 ft and use 48.8 m for 160 ft.
d
See Section 12.2.5.4 for a description of seismic force-resisting systems limited to buildings with a structural height, hn, of 240 ft (73.2 m) or less.
e
See Section 12.2.5.4 for seismic force-resisting systems limited to buildings with a structural height, hn, of 160 ft (48.8 m) or less.
f
Ordinary moment frame is permitted to be used in lieu of intermediate moment frame for Seismic Design Categories B or C.
g
Where the tabulated value of the overstrength factor, Ω0, is greater than or equal to 2½, Ωo is permitted to be reduced by subtracting the value of 1/2
for structures with flexible diaphragms.
h
See Section 12.2.5.7 for limitations in structures assigned to Seismic Design Categories D, E, or F.
i
See Section 12.2.5.6 for limitations in structures assigned to Seismic Design Categories D, E, or F.
j
Steel ordinary concentrically braced frames are permitted in single-story buildings up to a structural height, hn, of 60 ft (18.3 m) where the dead load of
the roof does not exceed 20 psf
(0.96 kN/m2) and in penthouse structures.
k
An increase in structural height, hn, to 45 ft (13.7 m) is permitted for single story storage warehouse facilities.
l
In Section 2.2 of ACI 318. A shear wall is defined as a structural wall.
m
In Section 2.2 of ACI 318. The definition of “special structural wall” includes precast and cast-in-place construction.
n
In Section 2.2 of ACI 318. The definition of “special moment frame” includes precast and cast-in-place construction.
o
Alternately, the seismic load effect with overstrength, Emh, is permitted to be based on the expected strength determined in accordance with AISI S110.
p
Cold-formed steel – special bolted moment frames shall be limited to one-story in height in accordance with AISI S110.
b
77
Fundamental Period, T
 May be computed by approximate means, Ta
Ta = CThnx
CT = building period coefficient
hn = building height
 moment frames (< 12 stories, >10ft)
Ta =0.1N (N = # of stories)
 May be computed by analytical means, T
T < Cu Ta
CU = Coefficient for upper limit
30
Base Shear Summary
V = CsW
W = building seismic weight
0.01 or 0.5S1(I/R) <
(I/R)  SDS < SD1/T(I/R)) or SD1TL/T2(I/R)
MCE ground motion
Base on seismic hazard map
T (from analysis) or
Ta = CThnx or Ta = 0.1N
response modification factor
based on seismic force-resisting system
occupancy importance factor
CT = 0.028, 0.016, 0.030, or 0.020
hn = building height
N = number of storys
based on occupancy category
design spectral response
acceleration
31
Vertical Distribution of Base Shear

For short period buildings the vertical distribution
generally follows the first mode of vibration in
which the force increases linearly with height for
evenly distributed mass.

For long period buildings the force is shifted
upwards to account for the whipping action
associated with increased flexibility

Story Force, Fx
Fx = CvxV,
Cvx = wxhxk / Σwihik
Cvx = vertical distribution factor
V = total design lateral force or shear at the base
wi and wx = portion of the total effective seismic weight of the structure located to level i or x
hi and hx = height from the base to level i or x
k = exponent related to the structure period as follows:
k=1
, T ≤ 0.5sec
k=2
, T ≥ 2.5sec
k=2 or linear interpolation between 1 &2
, 0.5 < T < 2.5
32
Horizontal Distribution
 Being an inertial force, the Story Force, Fx, is distributed in
accordance with the distribution of the mass at each level.
33
Drift and Deformation
 Story Drift
∆ = Cd /I  δxe
cf) V = CsW = I/R  SDS W
δxe = the deflections determined by an elastic analysis
Cd = the deflection amplification factor
I = the importance factor
34
Drift Limits
 Depend on:

Occupancy category

Structural system (masonry or not masonry)

Building height and nonstructural component design
35
Seismic Design Procedure
Occupancy Category
& Importance Factor, I
Min. permissible analysis proc.
MCE Spectral Accel., SS& S1
Equivalent Lateral Force
Site Class (A ~F)
- Seismic Base Shear
- Vertical Distribution
- Horizontal Distribution
Site Coef., Fa & Fv
Response Modification Factor, R
Adjusted MCE Accel, SMS & SM1
Structure Period, T
Design Values, SDS & SD1
Diaphragms, Irregularity,
Redundancy Factor
Seismic Design Category (A~F)
Drift and Deformation
36
Reference
 International Building Code 2009
 ASCE 7-05 Minimum Design Loads for buildings and other
Structures
 2007 CBC Structural Provisions – Seismic
 ASCE 7-05 Seismic Provisions - A Beginner's Guide to ASCE 7-05
 http://www.iccsafe.org
 https://www.asce.org
 IBC 2006 & ASCE 7-05 Structural Provisions by ABS consulting
 2007 CBC Structural Seismic Provisions by City of Huntington
Beach
37
Design Code Lecture
April 25, 2013
International Building Code
Seismic Provisions – Sample Example
CEE 572 Earthquake Engineering
Lecture Notes: Prof/ Amr S. Elnashai
Prepared by: Dr/ DoSoo Moon
Mid-America Earthquake Center
1
Seismic Design Procedure
Occupancy Category
& Importance Factor, I
Min. permissible analysis proc.
MCE Spectral Accel., SS& S1
Equivalent Lateral Force
Site Class (A ~F)
- Seismic Base Shear
- Vertical Distribution
- Horizontal Distribution
Site Coef., Fa & Fv
Response Modification Factor, R
Adjusted MCE Accel, SMS & SM1
Structure Period, T
Design Values, SDS & SD1
Diaphragms, Irregularity,
Redundancy Factor
Seismic Design Category (A~F)
Drift and Deformation
2
Seismic Design Category (SDC)
Structure Occupancy
Category
Structure Importance
Factor, I
Structure Location
SS, S1
(Hazard Map)
SMS, SM1
(Site Soil Condition)
SDS, SD1
(Design Values)
SDC
(Occupancy Category & SDS or SD1)
3
Example 1 Calculation of Design Accelerations SDS & SD1
 Given : Site Data

Site Location: 24000 Hollyoak, Aliso Viejo, California
Latitude
Longitude

= 33.57806
= -117.71010
Site Class: D
4
Example 1 Calculation of Design Accelerations SDS & SD1
 Using Seismic Hazard Map:

MCE
─ SS = 1.462
─ S1 = 0.516
Site Coef.
Ss

Modified MCE for Site Class D
─ SMS = FaSS = 1.0 x 1.462 = 1.462
─ SM1 = FvS1 = 1.5 x 0.516 = 0.774

Design Acceleration
S1
─ SDS = 2/3 SMS = 0.975
─ SD1 = 2/3 SM1= 0.516
5
Example 1 Calculation of Design Accelerations SDS & SD1
 Using USGS ground motion JAVA application:
http://earthquake.usgs.gov/hazards/designmaps/buildings.php
6
Example 1 Calculation of Design Accelerations SDS & SD1
 Calculate Ss and S1
7
Example 1 Calculation of Design Accelerations SDS & SD1
 Calculate SM and SD
8
Example 2 Calculation of Base Shear
 Given : Seismic Design Criteria

Design Acceleration for Site Class D
─ SDS = 0.975
─ SD1 = 0.516

Four Story Regular Residential Building
─ R = 6.5
─ T = 0.4 s
9
Example 2 Calculation of Base Shear
 Seismic Design Category

Four Story Residential Building
─ Occupancy Category II
─ (Importance Factor I = 1.0)

Design Acceleration
─ SDS = 0.975, SD1 = 0.516

SDC: D
SDS = 0.975
SD1 = 0.516
10
Example 2 Calculation of Base Shear
 Determine the Analysis Method

SDC: D, Occupancy Category II
T = 0.4 s < 3.5 Ts = 3.5 SD1/SDS = 3.50.516/0.975 = 1.85
11
Example 2 Calculation of Base Shear
V = CsW =(I/RSDS) W
 Seismic Response Coefficient, Cs

R = 6.5
I = 1.0
Cs = SDS(I/R) = 0.975(1/6.5) = 0.15
─ not more than
SD1/T(I/R) = 0.516/0.4 (1/6.5) = 0.198
, T=0.4 < TL =8
─ not less than
0.01
, S1= 0.516 < 0.6g
 Base Shear, V
V = CS W = 0.15 W
12
Example 3
 The wood framed office building shown here is to be
constructed in a “suburban” area in Juneau, Alaska out
near the airport. The site conditions consist of stiff soil.
 Other Given Data





Roof DL = 15 psf
Typical Floor DL = 12 psf
Partition Load = 15 psf
Snow Load = 30 psf (use 25%)
Exterior Wall DL = 10 psf
13
Determine Seismic Design Category
 Get SS and S1 from the maps or online
 Using USGS software with a 99801 zip code:
 SS = 0.612, S1 = 0.289
 The building Site Class is D
 Fa = 1.311; Fv = 1.822
 SMS = FaSS = 1.311(0.612) = 0.802
SM1 = FvS1 = 1.822(0.289) = 0.526
 SDS = (2/3) SMS = 2/3(0.802) = 0.535
SD1 = (2/3) SM1 = 2/3(0.526) = 0.351
 The building is in Occupancy Category II
 Seismic Design Category is D
14
Determine Seismic Design Category
Fa = 1.4-0.2/0.25*(0.612-0.5) = 1.311
Fv = 2.0-0.2/0.1*(0.289-0.2) = 1.822
SS = 0.612
Site Coef.
Fa 
S1 = 0.289
Site Coef.
FV 
15
Determine I & SDC
SDS = 0.535
SD1 = 0.351
16
Categorize the Plan Irregularities
 Plan Irregularities

Re-entrant corners (Type 2) since the projection is more than 15% of
dimension
─ 0.15(60’) = 9’ < 30’
 No Vertical Irregularities
17
Determine the Analysis Method
T = 0.318 sec < 3.5 Ts = 3.5 SD1/SDS = 3.50.351/0.535 = 2.3 sec
18
Response Modification Coefficient, R
V = CsW =(I/RSDS) W
19
Fundamental Period, T
V = CsW =(I/RSDS) W
 Approximate fundamental period for the building
hn = 40’
Ta = CThn x = 0.020(40’)0.75 = 0.318 sec.
20
Seismic Response Coefficient, Cs
V = CsW =(I/RSDS) W
 Cs = SDS(I/R) = 0.535 (1/6.5) = 0.0823

Lower limit = 0.01
S1= 0.289g < 0.6g

Upper limit = SD1/T (I/R) = 0.351/0.318  (1/6.5) = 0.169
T=0.318 < TL =8
21
Determine Building Weight, W
V = CsW =(I/RSDS) W
Roof:
Unit
psf
Roof
Ext. Walls
Snow/4
Area
ft^2
2040
1120
2040
Unit
psf
Roof
Ext. Walls
Partitions
Area
ft^2
2040
2240
2040
Typ. Floor
Total Building
Level
Roof
4th flr
3rd flr
2nd flr
15
10
12.5
12
10
15
Weight
lb
30600
11200
25500
67300
Weight
lb
24480
22400
30600
77480
Weight
k
67.3
77.48
77.48
77.48
299.74
22
Base Shear, V
V = CsW =(I/RSDS) W
 V = CsW = 0.0823(299.74 k) = 24.67 kips
─ total lateral force on the structure.
23
Compute the Vertical Distribution
Fx = CvxV,
Cvx = wxhxk / Σwihik
Base Shear, V =
k=1 since T=0.318sec ≤ 0.5sec
24.67 kips
wx
hx
wxhxk
(k)
(ft)
(ft-k)
Roof
67.3
40
2692
0.367
9.05
4th floor
77.48
30
2324.4
0.317
7.81
3rd floor
77.48
20
1549.6
0.211
5.21
2nd floor
77.48
10
774.8
0.106
2.60
Sum:
299.74
7340.8
1.000
24.67
Level
Cvx
Fx
(k)
24
Horizontal Distribution
 Load is distributed
according to mass
distribution.
 Since the loading is
symmetrical, each of
the two supporting
shear walls receives
half the story shear.
25
Reference
 International Building Code 2009
 ASCE 7-05 Minimum Design Loads for buildings and other
Structures
 2007 CBC Structural Provisions – Seismic
 ASCE 7-05 Seismic Provisions - A Beginner's Guide to ASCE 7-05
 http://www.iccsafe.org
 https://www.asce.org
 IBC 2006 & ASCE 7-05 Structural Provisions by ABS consulting
 2007 CBC Structural Seismic Provisions by City of Huntington
Beach
26