Seismic Design - Introduction

1 MAY 2015
SEISMIC DESIGN - INTRODUCTION1
SEISMIC DESIGN - INTRODUCTION
Dr. Ajit C. Khanse, Ph. D.

Agenda
1 MAY 2015
Seismic
Design
Introduction
SDC &
Design
Structural
failures
Plate
Tectonics
Seismicity
Fault
Rupture
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1 MAY 2015
WORLD SEISMICITY: 1900 – 2013
Seismicity refers to the geographic and historical distribution of earthquakes. The dots
represent the epicenters of significant earthquakes. It is apparent that the locations of
the great majority of earthquakes correspond to the boundaries between plates.
Mw ≥ 7.0

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Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-
called Ring of Fire, a zone of frequent earthquakes and volcanic eruptions.
RING OF FIRE

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The Earth is made up of a dozen major plates and several minor plates. Tectonic
plates are constantly on the move. The fastest tectonic plate constantly races
along at 6” per year while the slowest plates crawl at less than1” per year [USGS]
PLATE TECTONICS

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CONTINETAL DRIFT
www.tectonics.caltech.edu

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SAN ANDREAS FAULT, CA
The Pacific Plate (western side of San Andreas fault) is
moving horizontally in a northerly direction relative to the
North American Plate (eastern side of fault)

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RUPTURE PROPAGATION With Compliments from Prof. Krishnan, Caltech

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EARTHQUAKE MAGNITUDE
Earthquake magnitude
M, is a measure of the
kinetic energy released
by an earthquake.
Due to limitations in the
ability of some recording
instruments to measure
values above a certain
amplitude, some of these
magnitude scales tend to
reach an asymptotic
upper limit. To correct this,
the moment magnitude,
Mw, scale was developed.

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EFFECTS OF EARTHQUAKE
1)Ground Shaking
2)Permanent Ground Deformation
3)Liquefaction (a) Sand Boils
(b) Lateral Spreading Landslides
(c) Graben and Horst
4)Basin Effect
5)Tsunami
6)Landslides
7)Structural Destruction

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PROGRESSIVE COLLAPSE, Mw = 7.9 With Compliments from Prof. Krishnan, Caltech

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GROUND SHAKING RESULTING IN STRUCTURAL FAILURE
The reverse-oblique fault line crosses the largest concrete gravity 石岡
Shigung dam in Taiwan. The eastern 80 % of the dam is uplifted by about
33 ft and the western part by about 10 ft. At fault-line, the concrete dam
wall was cut off and 23 ft difference appeared in the elevation.
The 1999 Chi Chi, Taiwan Earthquake, Mw = 7.6 www.infra.kochi-tech.ac.jp/

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PERMANENT GROUND DEFORMATION
The 1999 Chi Chi, Taiwan Earthquake, Mw = 7.6
Ref: kyoto-u.ac.jp

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SOIL LIQUEFACTION describes a phenomenon whereby
a saturated soil substantially loses strength and stiffness in
response to earthquake shaking or other sudden change in
stress condition, causing it to behave like a liquid.

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A SAND BOIL is sand & water that
come out onto the ground surface
during an earthquake as a result of
liquefaction at shallow depth.
. .

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Lateral spread or flow are terms referring to landslides that commonly form
on gentle slopes and that have rapid fluid-like flow movement, like water.
LIQUEFACTION: Lateral Spreading Landslides

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LIQUEFACTION: Lateral Spreading
Lateral spreading in the
soil beneath the roadway
embankment caused the
embankment to be pulled
apart, producing the large
crack down the center of
the road. (REF: USGS)
The 1964 Alaska Earthquake, Mw = 7.9

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BASIN EFFECT – I
Epicenter was 220 miles away from
Mexico City. Estimated 35,000 people
died in Mexico City, where 412
multistory (8 to 25 floors) buildings
collapsed completely and another
3,124 were seriously damaged. (USGS)
21-story, steel-frame building 15-story reinforced concrete building
8-story RC building
The 1985 Michoacán (Mexico) Earthquake, Mw = 8.3

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BASIN EFFECT – II
Characteristics of the soil profiles
• Extremely soft, saturated surface clays
• At some places Plasticity Index ≈ 300
• Friction angles as low as, ϕ = 5-15o
Zone Depth
(ft)
Eff. Vs
(ft/s)
Predominant
period (s)
Transition 43 285 0.6
Lake 125 250 2.0
Deep Lake 185 200 3.4
Dynamic characteristics of
Soil deposits play vital role
[Aviles and Perez-Rocha 1998]
Map of seismic zonation and isoperiod
curves (in sec) of Mexico City

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BASIN EFFECT – III
 Source-averaged basin amplification is period-dependent,
with the highest amplifications occurring for the longest
periods and greatest basin depths.
 Relative to the very-hard rock reference structure, general
maximum amplification is about a factor of 8. At Mexico
city (1985 Michoacán earthquake), seismic motion was
amplified up to a factor of 60 compared to the bedrock.
[Aviles and Perez-Rocha 1998]

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Earthquake Magnitude vs Tsunami Intensity (1896 – 2005)
Earthquake Magnitude
REF: USGS

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TSUNAMI 津波 Seismic Sea Waves
Tsunamis are ocean waves caused by large earthquakes & landslides
that occur near or under the ocean.
Generated when thrust faults associated with convergent or destructive
plate boundaries move abruptly, resulting in water displacement, owing
to the vertical component of movement involved.
Sumatra and the Andaman Islands are part of an island arc.
REF: USGS

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Details of Tsunami Generation
REF: USGS
Tsunami generation from an inter-plate thrust fault
The displacement of rock surrounding the inter-plate thrust
Diagram of tsunami splitting, soon after generation

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USGSThe 2004 Mw =9.2 Sumatra Earthquake: Rupture Propagation

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LANDSLIDES
Landslide north of Fort Funston, San Mateo Coast, CA
The 1989 Loma Prieta Earthquake
Landslides occur due to ground shaking alone or shaking-caused
dilation of soil materials, which allows rapid infiltration of water. REF: USGS

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LANDSLIDE MITIGATION
The hazard from landslides can be reduced by
 avoiding construction on steep slopes and existing landslides
 stabilizing the slopes.
Slope stability is increased when
 a retaining structure &/or the weight of a soil/rock berm are
placed at the toe of the landslide.
 when mass is removed from the top of the slope.
 When ground water is prevented from rising in the landslide
mass.

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TUNNEL DESTRUCTION
2004 Niigata Earthquake, Japan
1995 Kobe Earthquake, Japan

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‘There is not a fiercer hell than the failure in a great object’ – Keats
LOMA PRIETA 1989, Mw=6.93KOBE, JAPAN 1995, Mw= 6.9

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FEW Q&A
Q: There are no faults in the Central and Eastern United States
(CEUS). Earthquakes are rare. Is seismic design mandatory?
• An intraplate earthquake occurs in the interior of a tectonic plate,
which could be due to unknown causative fault buried inside a plate.
• Recall Load Combinations of AASHTO 2010 & ASCE 7-10.
• Site-specific investigation of Seismic Design Category (SDC)
determines the type of design procedure.
Q: Traditionally unreinforced concrete liner has been provided in some
cases – is it acceptable?
AASHTO 2010 has no comment. ACI 318-14 Ch. 18 on ‘Earthquake
Resistant Structures’ does not allow unreinforced concrete. Further, the
ovaling deformation may induce considerable tensile hoop forces.

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FEW Q&A
Q: Since liner in rock is anchored to rock, the tensile hoop forces in liner
are apparent during ovaling response. Do we have these for liner in soil?
Liner in Soil

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FEW Q&A
Liner in Soil

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FEW Q&A
F = m.a
Forces due to motion,
Liner in Soil
T
T

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SEISMIC DESIGN CATEGORY (SDC)
There are various correlations of the qualitative Modified
Mercalli Intensity (MMI) with quantitative characterizations
of ground-shaking limits for the various SDCs.
MMI V No real damage SDC A 0 < SM1 <0.1g
MMI VI Light nonstructural damage SDC B 0.1g < SM1 < 0.2g
MMI VII Hazardous nonstructural damage SDC C 0.2g < SM1 < 0.3g
MMI VIII Hazardous damage to susceptible structures SDC D 0.3 < SM1 < 1.12g
MMI IX Hazardous damage to robust structures SDC E SM1 > 1.125g
[§11.6, ASCE 7-10]

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MCER 1-second spectral response acceleration parameter, SM1 (%g)
Map with associated regions of Seismic Design
Category, assuming Site Class D conditions

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SEISMIC DESIGN CATEGORY (SDC)
[ASCE 7-10, AASHTO 2010]
Seismic Design Category (SDC) depends upon
 Topographic location,
 Site soil class,
 Occupancy (risk) category,
 Deterministic design spectral response parameter at short
period SDS and that at 1-sec period SD1.
The design requirements depending upon SDC:
 SDC A: No seismic design. Certain provisions shall be met.
 SDC B & C: Analytical closed-form analysis procedure.
 SDC D, E & F: The finite-element or finite-difference numerical
modelling approach.

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LOAD CASE EXTREME EVENT - I
[AASHTO 2010]
• Designed to withstand seismic ground motions with a
Return Period of 2,500 years, corresponding to 2%
probability of exceedance in 50 years.
• Values from Maximum Considered Earthquake (MCER)
shall be used for Load Case Extreme Event I.
The recurrence interval, or Return Period (RP), is the
average time span between earthquake occurrences.
In 1
100
T
RP
PE

 
  
 
For PE = 2 and T = 50 years, RP ≈ 2,500 years

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LOAD CASE EXTREME EVENT - I
[AASHTO 2010]
, site-specific, deterministic
http://earthquake.usgs.gov/designmaps/us/application.php

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RESPONSE SPECTRA
Response spectra
establish the ground
motion shaking intensity
level and are used for
deriving other ground
motion parameters, e.g.,
PGA / SM1 is used to find
PGV, shear strain, etc.
Response spectra are
used as target spectra for
generating design ground
motion time histories for
refined numerical analysis
Minimum three points are required
to establish Response Spectra

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LOAD CASE EXTREME EVENT - II
[AASHTO 2010]
area-specific, probabilistic
http://geohazards.usgs.gov/hazards/apps/cmaps
 A 'realistic design basis earthquake',
typically taken as occurring once in a
period equal to about three times the
design life (3 x 100).
 For CEUSA, the Return Period of
500 years i.e., 10% probability of
exceedance in 50 years.
 The values for site class B are
obtained from USGS hazard maps.
 Values for other soil class are
derived from Ch. 11 of ASCE 7-10

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LOAD CASE EXTREME EVENT - III
[AASHTO 2010]
area-specific, probabilistic, all soil types
http://geohazards.usgs.gov/hazardtool/application.php
 The Extreme Event III and
Construction Strength I combination
should consider “a smaller
earthquake as a static load” to be
combined with other loads
 A Return Period of 10 years i.e.,
99% probability of exceedance in 50
years
 The values for all site classes for
any probability are obtained from
USGS hazard maps.

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SEISMIC DESIGN TOOL – WORLDWIDE
http://earthquake.usgs.gov/hazards/designmaps/wwdesign.php
Salah Bey Cable Bridge, Constantine, Algeria

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SIMPLIFIED PROCEDURE FOR SDC B & C:
Ovaling/Racking Deformation of
Circular/Rectangular c/section to
Vertically Propagating Shear Waves
Axial/Curvature Deformation Along
Tunnel Due to Traveling Waves

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SIMPLIFIED PROCEDURE FOR SDC B & C:
 The values of "Peak Gravitational Acceleration (PGA)" and
"Maximum spectral response at 1-s period (SM1)" are obtained
from the site-specific, deterministic hazard analysis from USGS.
 SM1 is used to calculate the shear wave peak particle velocity Vs
of soil
 Using closed-form analytical equations, the free-field shear
strain, γ at the required depth is evaluated from PGA and Vs,
separately.
 Bending moments and axial hoop forces are evaluated from γ
using closed-form equations.
 Seismic forces are added to static loads with appropriate load
factors.
Ch. 13 of AASHTO 2010

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FE NUMERICAL PROCEDURE FOR SDC D, E & F:
(A) Pseudo-Static Seismic Coefficient Deformation Method for
(a) underground structures buried at shallow depths,
(b) when the subsurface conditions are not highly variable,
nor ground stability is a concern,
(c) simple and non-critical structures,
(d) low seismic area
(B) Dynamic Time History Analysis:
In a dynamic time history analysis, the entire soil-structure
system is subject to dynamic excitations using ground motion
time histories as input at the base of the soil-structure system

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DYNAMIC TIME HISTORY ANALYSIS using Plaxis
Tunnel of any shape can be modeled
Dynamic Load input options:
1) Simple sinusoidal wave
2) Any time-dependent force
3) Earthquake Time History

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SOIL STRUCTURE INETRACTION (SSI)
The response of a structure to
earthquake shaking is affected by
interactions between three linked
systems:
1) the structure,
2) the foundation, and
3) the geologic media underlying
and surrounding the foundation.
[Fig. from H. Allison Smith & Wen-Hwa Wu, 1997]

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FLUID STRUCTURE INTERACTION (FSI)
Femarnbelt Immersed Tube Tunnel, Denmark Offshore structures

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Thank You! Q?
“Earthquake effects on structures
systematically bring out the mistakes
made in design and construction,
even the minutest mistakes” –
Newmark and Rosenblueth

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DESIGN STANDARDS
(1)AASHTO Technical Manual for Design & Construction of Road Tunnels –
Civil Elements 2010
(2)FHWA-NHI-11-032, LRFD Seismic Analysis and Design of Transportation
Geotechnical Features and Structural Foundations, 2011
(3)FHWA-HRT-05-067 Seismic Retrofitting Manual for Highway Structures: Part
2 – Tunnels, Retaining Structures, Slopes, Culverts & Roadways, 2005
(4) ASCE/SEI 7-10 Minimum Design Loads for Buildings and Other Structures
(5)AASHTO LRFD Bridge Design Specifications, 6th Edition, 2014
(6) AASHTO LRFD Seismic Bridge Design, 2nd Edition, 2011
(7)AISC 341-10 Seismic Provisions for Structural Steel Buildings, 2010
(8)ACI 318-14 Building Code Requirements for Structural Concrete & Commentary

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MCER = Risk-targeted Maximum Considered Earthquake Ground Motion.
Design response spectrum shall be determined by dividing ordinates of
MCER response spectrum by 1.5.
FEW NOTATIONS & DEFINATIONS
CR = risk coefficient; see Section 21.2.1.1
CRS = mapped value of the risk coefficient at short periods as defined by Figure 22-3
CR1 = mapped value of the risk coefficient at a period of 1 second as defined by Figure 22-4
SSD = mapped deterministic, 5 percent damped, spectral response acceleration parameter at short
periods as defined in Section 11.4.1
SSUH = mapped uniform-hazard, 5 percent damped, spectral response acceleration parameter at short
periods as defined in Section 11.4.1
S1D = mapped deterministic, 5 percent damped, spectral response acceleration parameter at a period of
1 second as defined in Section 11.4.1
S1UH = mapped uniform-hazard, 5 percent damped, spectral response acceleration parameter at a period
of 1 second as defined in Section 11.4.1
SS = 5 percent damped, spectral response acceleration parameter at short periods as defined in Sec. 11.4.3
S1 = spectral response acceleration parameter at a period of 1 second as defined in Section 11.4.3
SaM = the site-specific MCER spectral response acceleration at any period
SMS = the MCER, 5 percent damped, spectral response acceleration parameter at short periods adjusted
for target risk and site-class effects as defined in Section 11.4.3
SM1 = the MCER, 5 percent damped, spectral response acceleration parameter at a period of 1 second
adjusted for target risk and site-class effects as defined in Section 11.4.3
[Sec. 11.2, 11.3, ASCE 7-10]

Presentation Title
DESIGN RESPONSE SPECTRA
54
for TS ≤ T ≤ TL (Eq. 11.4-10)
for T > TL (Eq. 11.4-11)
SDS = ⅔.Fa.CRS.SSUH or ⅔.Fa.SSD, lesser. (Eq. 11.4-1, 11.4-2, Table 11.4-1)
0
0
0.4 0.6 ( .11.4 9)DSa
T
S for T T EqS
T
 
    
 
SD1 = ⅔.Fv.CR1.S1UH or ⅔.Fv.S1D, lesser. (Eq. 11.4-3, 11.4-4, Table 11.4-2)
[Sec. 11.4, ASCE 7-10]
Response Spectra

Seismic Design - Introduction

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