Seismic Loading

1. CVE 12: BUILDING DESIGN
EARTHQUAKE LOAD
BY: ENGR. MARK IPA

4. Definition of Terms
• BASE SHEAR, V
- the total design lateral force or shear at the base of
a structure
• DESIGN SEISMIC FORCE
- is the minimum total strength design base shear
• DUAL SYSTEM
- is a combination of moment-resisting frame and
shear walls or braced frames

5. Definition of Terms
• LATERAL-FORCE RESISTING FRAME
- part of the structural system designed to resist the design
seismic forces
• MOMENT RESISTING FRAME
- is a frame in which members and joints are capable of
resisting forces primarily by flexure
• ORTHOGONAL EFFECTS
- are the earthquake load effects on structural elements
common to the lateral force resisting systems along two
orthogonal axes

6. Definition of Terms
• STORY SHEAR, Vx
- is the summation of lateral forces above the story
under consideration
• STRUCTURES
- is an assemblage of framing members designed to
support gravity loads and resist lateral forces . May be
recognized as building or non-building.

7. TABLE 208-1
OCCUPANCY
CATEGORY
SEISMIC IMPORTANCE
FACTOR, I
SEISMIC IMPORTANCE
FACTOR, Ip
I. Essential Facilities 1.50 1.50
II. Hazardous Facilities 1.25 1.50
III. Special Occupancy
Structures
1.0 1.0
IV. Standard Occupancy
Structures 1.0 1.0
V. Miscellaneous
Structures
1.0 1.0

8. Table 208-6 – Seismic Source Types
SEISMIC SOURCE
TYPE
SEISMIC SOURCE
DESCRIPTION
SEISMIC SOURCE
DEFINITION
MAXIMUM MOMENT
MAGNITUDE, M
A
Faults that are capable of
producing large magnitude
events and that have a high
rate of seismic activity
M ≥ 7.0
B
All faults other than Type A
and C
6.5 ≤ M < 7.0
C
Faults that are not capable of
producing large magnitude
earthquakes and that have
low rate of seismic activity
M < 6.5

9. Table 208-2 – Soil Profile Types
SOIL
PROFILE
TYPE
Soil Profile
Name/Generic
Description
Average Soil Properties for Top 30m of Soil
Profile
Shear Wave
Velocity, Vs
(m/s)
SPT, N
(blows/
300mm)
Undrained
Shear
Strength, Su
(kPa)
SA
Hard Rock > 1500
SB
Rock 760 to 1500
SC
Very Dense
Soil and Soft
Rock
360 to 760 > 50 > 100
SD
Stiff Soil Profile 180 to 360 15 to 50 50 to 100
SE
Soft Soil Profile < 180 < 15 < 50
SF
Soil Requiring Site-Specific Evaluation

10. TABLE 208-3 Seismic Zone Factor Z
ZONE II IV
Z
.20 .40
TABLE 208-4 Near Source Factor Na
SEISMIC SOURCE
TYPE
Closest Distance to Known Seismic Source
≤ 5 km ≥ 10 km
A 1.2 1.0
B 1.0 1.0
C 1.0 1.0

11. TABLE 208-5 Near Source Factor Nv
SEISMIC SOURCE
TYPE
Closest Distance to Known Seismic Source
≤ 5 km ≥ 15 km
A 1.6 1.0
B 1.2 1.0
C 1.0 1.0

12. TABLE 208-7 Seismic Coefficients, Ca
SOIL PROFILETYPE
Seismic Zone Z
Z = .20 Z = 0.40
SA 0.16 0.32Na
SB 0.20 0.40Na
SC 0.24 0.40Na
SD 0.28 0.44Na
SE 0.34
0.44Na
SF
Soil Requiring Site-Specific Evaluation

13. TABLE 208-8 Seismic Coefficients, Cv
SOIL PROFILETYPE
Seismic Zone Z
Z = .20 Z = 0.40
SA 0.16 0.32Nv
SB 0.20 0.40Nv
SC 0.32 0.56Nv
SD 0.40 0.64Nv
SE 0.64
0.96Nv
SF
Soil Requiring Site-Specific Evaluation

14. Configuration Requirements
• REGULAR STRUCTURES
- have no physical discontinuities in plan or vertical
configuration or in their lateral-force-resisting systems such
as irregular features
• IRREGULAR STRUCURES
- have significant physical discontinuities in configuration
or in their lateral-force-resisting systems

15. Configuration Requirements

16. Configuration Requirements

17. Configuration Requirements

18. Configuration Requirements

19. Configuration Requirements

20. Configuration Requirements

21. Configuration Requirements

22. Configuration Requirements

23. Configuration Requirements

24. Configuration Requirements

25. STRUCTURAL SYSTEMS

26. STRUCTURAL SYSTEMS

27. STRUCTURAL SYSTEMS

28. STRUCTURAL SYSTEMS

29. LATERAL FORCE PROCEDURE
• STATIC LATERAL FORCE PROCEDURE
All structures (regular of irregular) in occupancy IV and V in
Seismic Zone II
Regular structures under 75m in height
Irregular structures no more than five stories or 20m in
height
Structures having a flexible upper portion supported on a
rigid lower portion

30. LATERAL FORCE PROCEDURE
• DYNAMIC LATERAL FORCE PROCEDURE
Structures 75m or more in height
Structures having stiffness, weight or geometric vertical
irregularity of Type 1, 2 or 3, or structures having irregular
features
Structures over five stories or 20m in height in Seismic
Zone IV not having the same structural system throughout
their height
Structures, regular or irregular, located on soil Profile Type
SF that have period over than 0.7 sec.

31. STATIC FORCE PROCEDURE
TOTAL DESIGN BASE SHEAR, V
W: Weight of the structure being considered
R: Overstrenght Factor
I: Importance Factor
T: Period of the Structure
Cv: Seismic Coefficient
Ca: Seismic Coeeficient
Z: Zone Factor
Vbase
Cv I
R T
W

32. STATIC FORCE PROCEDURE
The total design base shear need not exceed the following
The total design base shear shall not be less than the
following:
In addition, for Seismic Zone IV, the total base shear shall
not be less than the following:
Vbase
2.5Ca I
R
W
Vbase .11Ca I W
Vbase
0.8Z Nv I
R
W

33. PERIOD OF A STRUCTURE
Method A:
Ct = 0.0853 for steel moment-resisting frames
= 0.0731 for reinforced concrete resisting frames and
eccentrically braced frames
= 0.0488 for all other structures
Tperiod Ct hn 
3
4


34. PERIOD OF A STRUCTURE
Method B:
fi = applied lateral force
δi = elastic deflection
g = gravity
gf
w
T n
i
ii
n
i
ii
)(
)(
1
2
1
2








35. NEXT MEETING
Sample Calculations of Earthquake
Reminder:
Spreadsheet #3: Due Next Week