Transcript 2012 PowerPoint Template - AEG Southern California Section

consulting engineers and scientists
Updates on Ground
Motion and
Geotechnical Data
Requirements in the
2013 CBC
Jorge F. Meneses, PhD, PE, GE, D.GE, F.ASCE
Carlsbad, California
AEG Inland Empire Chapter
Continuing Education Series
May 31, 2014
Outline
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Overview
Design earthquakes
Maximum direction
Risk-targeted
General procedure
Examples
Geotechnical Requirements
Summary
Building Code Cycle
NEHRP 2009
ASCE 7-10
IBC 2012
2012
(Effective January 1, 2014)
Source, Path and Site
Evaluating Seismic Hazard and Ground Motions
Some definitions
• Definitions
– Hazard: a phenomenon that has the potential to cause
damage
– Risk: the probability that damage will occur
• In general, it is accepted that Earthquake Hazard
cannot be avoided
• Hence, the philosophy behind building codes is to
“mitigate risk”
– We can’t avoid earthquakes, so we will build structures
that can withstand earthquakes
• Key concept: acceptable risk
MCER
RISK-TARGETED MAXIMUM CONSIDERED
EARTHQUAKE (MCER) GROUND MOTION
RESPONSE ACCELERATION
The most severe earthquake effects considered by
ASCE 7-10 determined for the orientation that results
in the largest maximum response to horizontal ground
motions and with adjustment for targeted risk
(ASCE 7-10, Chapter 11, p.60)
MCEG
MAXIMUM CONSIDERED EARTHQUAKE
GEOMETRIC MEAN (MCEG) PEAK
GROUND ACCELERATION
The most severe earthquake effects considered by
ASCE 7-10 determined for geometric mean peak ground
acceleration and without adjustment for targeted risk
The MCEG PGA adjusted for site effects (PGAM) is used
for evaluation of liquefaction, lateral spreading, seismic
settlements, and other soil related issues.
(ASCE 7-10, Chapter 11, p.60)
Orientation of Maximum Response (Max. direction)
Maximum direction
Geomean and maximum Sa
(Whittaker et al 2009)
Landers, Joshua Tree
Loma Prieta, LGPC
DUZCE, BOLU
Directivity Effects on Ground Motions
Comparison of various models SaRotD100/SaRotD50
(Shahi and Baker 2013)
Maximum Response
• Ground motion values contoured on maps
incorporate factors to adjust from a geometric
mean to the maximum response regardless of
direction
• These factors are 1.1 for 0.2 second spectral
response acceleration (SS) and 1.3 for 1.0
second spectral response acceleration (S 1)
(ASCE 7-10, Figures 22-1 through 22-6)
General procedure
• Use mapped values and tables
from code
• USGS Seismic design maps
web application
Seismic Ground Motion Values
(ASCE 7-10, Chapter 11, p.65-66)
SMS, SM1
Fa , Fv
Site Class B
SS, S1
SDS, SD1
Site Classification
(ASCE 7-10, Chapter 20, p.204)
Site Coefficient Fa
Mapped risk-targeted MCER Sa at short second
Site class
Ss ≤ 0.25
Ss = 0.50
Ss = 0.75
Ss = 1.0
Ss ≥ 1.25
A
0.8
0.8
0.8
0.8
0.8
B
1.0
1.0
1.0
1.0
1.0
C
1.2
1.2
1.1
1.0
1.0
D
1.6
1.4
1.2
1.1
1.0
E
2.5
1.7
1.2
0.9
0.9
F
(Chapter 11, p.66)
Site-specific study required
Site Coefficient Fv
Mapped risk-targeted MCER Sa at 1 second
Site class
S1 ≤ 0.1
S1 = 0.2
S1 = 0.3
S1 = 0.4
S1 ≥ 0.5
A
0.8
0.8
0.8
0.8
0.8
B
1.0
1.0
1.0
1.0
1.0
C
1.7
1.6
1.5
1.4
1.3
D
2.4
2.0
1.8
1.6
1.5
E
3.5
3.2
2.8
2.4
2.4
F
(Chapter 11, p.66)
Site-specific study required
SAN DIEGO SITE
SITE CLASS C (Fa = 1.0, Fv = 1.3)
2.00
PGA = 0.378g
Spectral Acceleration (g)
MCER Site Class C
SS *Fa= SMS
1.50
DE = 2/3 MCER
Sa = SDS (0.4+0.6 T/To)
1.25
Sa = SD1/T
SDS = 2/3*SMS=0.946
1.00
SM1=Fv*S1 To = 0.2 SD1/SDS
Ts = SD1/SDS
0.75
S1
0.50
0.25
MCER Site Class B
5 percent
damping
1.75
PGA = 0.4 SDS = SDS/2.5
SD1 =2/3*SM1
=0.454
0.00
0.0
0.2
To=0.10
0.4
0.6
TS=0.48
0.8
1.0
Period (seconds)
1.2
1.4
1.6
1.8
2.0
Risk Category of Buildings
Use or occupancy of buildings and structures
Risk category
Buildings and other structures that represent a low risk to human
life in the event of failure
I
All buildings and other structures except those listed in Risk
Categories I, III, and IV
II
Buildings and other structures, the failure of which could pose a
substantial risk to human life
III
Buildings and other structures designated as essential facilities.
Buildings and other structures, the failure of which could pose a
substantial hazard to the community
IV
(Chapter 1, p.2)
Seismic Design Category based on S1
Risk category
Value of SDS
S1 ≥ 0.75
S1 < 0.75
(Chapter 11, p. 67)
I or II or III
IV
E
F
See following tables
Seismic Design Category based on SDS
Risk category
Value of SDS
I or II or III
IV
SDS < 0.167
A
A
0.167 ≤ SDS < 0.33
B
C
0.33 ≤ SDS < 0.50
C
D
0.50 ≤ SDS
D
D
(Chapter 11, p. 67)
Seismic Design Category based on SD1
Risk category
Value of SDS1
I or II or III
IV
SD1 < 0.067
A
A
0.067 ≤ SD1 < 0.133
B
C
0.133 ≤ SD1 < 0.20
C
D
0.20 ≤ SD1
D
D
(Chapter 11, p. 67)
Seismic design category D through F
For liquefaction studies
PGAM = FPGA PGA
PGAM = MCEG PGA adjusted for site effects
PGA = Mapped MCEG PGAs
FPGA = Site coefficients (see table)
(ASCE 7-10, Section 11.8.3.2, p.68-69)
Site coefficient FPGA
Mapped MCEG PGA
Site class
PGA ≤ 0.1
PGA = 0.2
PGA = 0.3
PGA = 0.4
PGA ≥ 0.5
A
0.8
0.8
0.8
0.8
0.8
B
1.0
1.0
1.0
1.0
1.0
C
1.2
1.2
1.1
1.0
1.0
D
1.6
1.4
1.2
1.1
1.0
E
2.5
1.7
1.2
0.9
0.9
F
Site-specific study required
(ASCE 7-10, Chapter 11, p.68)
Location of three selected sites
Rose CanyonNewport-Inglewood
Fault Zone
Coronado Bank
Fault Zone
San Diego
Trough Fault
Zone
http://geohazards.usgs.gov/designmaps/us/application.php
Comparison of design response spectra
1.2
Site 1
Site Class D
Design Spectral Accelerations (g)
1
0.8
0.6
0.4
ASCE 7-05
0.2
ASCE 7-10
0
0
0.5
1
1.5
2
Period (seconds)
2.5
3
3.5
4
Site 2
1
Design Spectral Accelerations (g)
0.9
Site 2
Site Class C
0.8
0.7
0.6
0.5
0.4
0.3
0.2
ASCE 7-05
0.1
ASCE 7-10
0
0
0.5
1
1.5
2
Period (seconds)
2.5
3
3.5
4
Site 3
1
Site 3
Site Class E
Design Spectral Accelerations (g)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
ASCE 7-05
0.2
ASCE 7-10
0.1
0
0
0.5
1
1.5
2
Period (seconds)
2.5
3
3.5
4
Site 2
Site Class E? Watch out!
Site Class E?
Site Class E? SM1 > SMS !
Comparison of SDS
(Luco 2009)
Comparison of SD1
SDS – Southern California
(OSHPD 2012)
SDS – Northern California
Maxima and Minima Values for California
Maxima
Ss = 3.73 g
S1 = 1.28 g
Minima
Ss = 0.204 g
S1 = 0.107 g
SDS = 0.22 g
SD1 = 0.17 g
Seismic design category D through F
For seismic lateral earth pressures:
The determination of dynamic seismic lateral earth
pressures on foundation walls and retaining walls
supporting more than 6 feet (1.83m) of backfill height
due to design earthquake ground motions
(2013 CBC, Section 1803A.5.12, p. 177)
Seismic design category D through F
An assessment of potential consequences of
liquefaction and soil strength loss, including, but
not limited to:
-
Estimation of total and differential settlement
Lateral soil movement
Lateral soil loads on foundations
Reduction in foundation soil-bearing capacity and lateral soil
reaction
- Soil downdrag and reduction in axial and lateral soil reaction
for pile foundations
- Increases in soil lateral pressures on retaining walls
(2013 CBC, Section 1803A.5.12, p. 177)
Seismic design category D through F
Discussion of mitigation measures such as, but
not limited to:
- Selection of appropriate foundation type and depths
- Selection of appropriate structural systems to accommodate
anticipated displacements and forces
- Ground stabilization
- Any combination of these measures and how they shall be
considered in the design of the structure
(2013 CBC, Section 1803A.5.12, p. 177)
Geotechnical Peer Review
(DSA-SS and DSA-SS/CC)
When alternate foundations designs or ground improvements
are employed or where slope stabilization is required, a
qualified peer review by a California-licensed geotechnical
engineer, in accordance with Section 3422, may be required by
the enforcement agency. In Section 3422, where reference is
made to structural or seismic-resisting system, it shall be
replaced with geotechnical, foundation, or ground improvement,
as appropriate.
(2013 CBC, Section 1803A.8, p. 178)
Retaining Walls – Design lateral soil
loads
Retaining walls shall be designed for the lateral loads
determined by a geotechnical investigation in accordance with
Section 1803A and shall not be less than eighty percent of the
lateral soil loads determined in accordance with Section 1610A.
(2013 CBC, Section 1803A.8, p. 178)
Table 1610A.1 Lateral Soil Load
(2013 CBC, Section 11610A, p. 87)
For further information
Contact
Jorge F. Meneses, PhD, PE, GE, D.GE, F.ASCE
[email protected]
(760)795-1964