1. 1
PROJECT REPORT
On
EFFECTS OF EARTHQUAKE ON FOUNDATIONS AND
DESIGN FOR EARTHQUAKES
FOUNDATION ENGINEERING
By
ROHIT SAHAI 1012135591
Under the guidance of
PROFESSOR ÖMER BILGIN
(Assistant Professor)
NOVEMBER 2014

2. 2
TABLE OF CONTENT
CHAPTER TITLE PAGE
ABSTRACT iii
LIST OF TABLES iv
LIST OF FIGURES v
1 INTRODUCTION 1
1.1 CHARACTERISTICS AND TYPES OF WAVES 1
1.1.1 Compression or P-Waves 1
1.1.2 S-Waves 1
1.1.3 Love Waves 2
1.1.4 Rayleigh Waves 2
1.2 CAUSES OF EARTHQUAKE 3
1.3 EARTHQUAKE LOADS ON STRUCTURES 3
1.4 SEISMIC RISK ZONE 3
1.5 SEISMIC RESPONSE OF BUILDING SYSTEM 4
2 METHODOLOGY 5
2.1 SOIL PROFILE TYPE FOR A BUILDING SITE 5
2.1.1 Inertia Forces on Structures 5
2.1.2 Flow of Inertia Forces to Foundations 5
2.2 SEISMIC DESIGN REQUIREMENTS 5
2.2.1 Calculations of Base Shear Due To Earthquake 6
2.2.2 Overturning Moment Due to Earthquake 8
2.3 RESPONSE CONTROL 9
2.3.1 Base Isolation and Isolating Devices 9
2.3.2 Rubber Pads 10
2.3.3 Lead Rubber Bearings 10
2.3.4 Spherical Sliding Base Isolation 10
2.4 RETROFITTING 11
2.4.1 Adding Shear Wall/Infill Wall 11
2.4.2 Adding Bracing 11
2.4.3 Adding Wing Wall/Buttress 12
2.4.4 Wall Thickening 12
2.4.5 Supplement Damping 13
2.4.6 Masonry Foundation Retrofit 13
REFERENCES 14

3. 3
EFFECTS OF EARTHQUAKE ON FOUNDATIONS AND DESIGNING FOR
EARTHQUAKES
R. Sahai1, A.M. A.S.C.E,
1University of Dayton, Department of Civil and Environmental Engineering,
929-H Wilmington Avenue, Dayton, OH 45420; PH (937) 607-8864; email:
sahair1@udayton.edu
ABSTRACT
Uncertainties involved in the characterization and seismic response of soil
foundation structure systems along with the inherent randomness of the earthquake
ground motion result in very complex (and often controversial) effects of soil
foundation structure interaction on the seismic response of structures.
The earthquake responses of structures are usually analyzed under the
assumption that the foundation is firmly bonded to the soil. Such analyses often
predict a base overturning moment that exceeds the available overturning resistance
due to gravity loads, which implies that a portion of the foundation mat or some of
the individual column footings would intermittently uplift during the earthquake.
Therefore, it is a vital subject to investigate the influence of uplift on earthquake
response of structures including the effect of different kinds of seismic waves evolved
during an earthquake.
The paper provides an introduction to principles of seismic design, including
strategies for designing earthquake resistant buildings to ensure safety and security of
building occupants and assets.
Retrofitting is the process of modifying something after it has been
manufactured. The primary purpose of earthquake retrofitting is to keep your home
from being displaced from its concrete foundation making the building safer and less
prone to major structural damage during an earthquake. Hence, the expectation of
improving amenities of the buildings which is achieved due to the development of
new technology that allows significant reduction in energy and loss of property will
be studied precisely in the paper.

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LIST OF TABLES
TABLE TITLE PAGE
2.1 Seismic Coefficient Ca 6
2.2 Seismic Coefficient Cv 6
2.3 Value of R factor for most common structural systems 7

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LIST OF FIGURES
FIGURE TITLE PAGE
1 Propagation of P-waves 1
2 Propagation of S-waves 2
3 Propagation of Love waves 2
4 Propagation of Rayleigh waves 2
5 Intensity of major earthquake activity in the United States 4
6 Effect of inertia in a building 5
7 Base Isolation Technique 9
8 Structure of elastomer rubber pad 10
9 Lead rubber bearing 10
10 Spherical Sliding Base Isolation 11
11 Shear wall and Infill wall 11
12 Cross bracings 12
13 Wing wall/Buttress 12
14 Wall thickening 12
15 Supplement Damping 13
16 Strengthening of foundations 13

6. 6
CHAPTER 1
INTRODUCTION
1.1 CHARACTERISTICS AND TYPES OF EARTHQUAKE WAVES
An earthquake (also known as a quake, tremor or temblor) is the result of a
sudden release of energy in the Earth's crust that creates seismic waves. The
seismicity or seismic activity of an area refers to the frequency, type and size of
earthquakes experienced over a period of time.
Earthquakes are measured using observations from seismometers. Seismic
waves are propagating vibrations that carry energy from the source of the shaking
outward in all directions.
There are many different seismic waves, but all basically of four types:
 Compression or P waves (for primary)
 Transverse or S waves (for secondary)
 Love waves
 Rayleigh waves
1.1.1 Compression or P-Waves
P-waves are the first waves to arrive on a complete record of ground shaking
because they travel the fastest (their name derives from this fact - P is an abbreviation
for primary, first wave to arrive). They typically travel at speeds between ~1 and ~14
km/sec (shown in figure 1).
Fig. 1: Propagation of P-waves
1.1.2 S-Waves
Secondary, or S waves, travel slower than P waves and are also called "shear"
waves because they don't change the volume of the material through which they
propagate, they shear it. S-waves are transverse waves because they vibrate the

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ground in the direction "transverse", or perpendicular, to the direction that the wave is
traveling (shown in figure 2).
Fig. 2: Propagation of S-waves
1.1.3 Love Waves
Love waves are transverse waves that vibrate the ground in the horizontal
direction perpendicular to the direction that the waves are traveling (shown in figure
3). Love waves are dispersive waves and they are formed by the interaction of S
waves with Earth's surface and shallow structure. The speed at which a dispersive
wave travels depends on the wave's period. In general, earthquakes generate Love
waves over a range of periods from 1000 to a fraction of a second, and each period
travels at a different velocity but the typical range of velocities is between 2 and 6
km/second.
Fig. 3: Propagation of Love waves
1.1.4 Rayleigh Waves
Rayleigh waves are the slowest of all the seismic wave types and in some
ways the most complicated. Like Love waves they are dispersive so the particular
speed at which they travel depends on the wave period and the near-surface geologic
structure, and they also decrease in amplitude with depth. Typical speeds for Rayleigh
waves are on the order of 1 to 5 km/s (shown in figure 4).
Fig. 4: Propagation of Rayleigh waves

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1.2 CAUSES OF EARTHQUAKES
The earthquakes are caused by various natural and artificial phenomenon’s:
 Inertial forces generated by severe ground shaking.
 By direct fault displacement at the site of a structure.
 By landslides, or other surface movements.
 Large-scale tectonic changes in ground elevation.
 By seismically induced water waves such as seismic sea waves (tsunamis) or
fluid motions in reservoirs and lakes.
1.3 EARTHQUAKE LOADS ON STRUCTURES
Earthquake forces are inertia forces, created at every molecule of mass in
every member of the structure as the structure is being shaken by earthquake motions.
The earthquake creates both lateral motions and vertical motions in a
structure. Under Newton’s second law relating force F, mass m and acceleration a
(F=ma), it is the rate of acceleration of these motions that governs the magnitude of
the earthquake forces. In general, vertical earthquake motions can produce vertical
inertia forces as high as 20% of the dead load, acting either upward or downward.
Similarly, lateral earthquake motions can produce lateral inertia forces as high as 30%
or even 40% of the dead weight of the building, acting laterally in any direction.
Structures are typically designed for vertical gravity loads of 100% dead load
plus 100% live load, with a nominal margin of safety of roughly 70% to failure load.
Consequently, the additional vertical load created by an earthquake (25% of dead
load) is not regarded as serious overload. In general, the vertical load produced by an
earthquake is considered to be within acceptable limits for a one time load and special
measures are not needed to account for the vertical load.
The base shear created by earthquake forces on a structure is an inertia force.
In earthquake design, the inertia force is computed as a factor times the dead weight
of the structure. The only loads that can contribute to base shear are the loads that will
be accelerated by the earthquake motion. The live loads are usually loose, or at least
so loosely fastened that they will not be accelerated at the same rate as the structural
frame. Even a small amount of slippage of an object will reduce the inertia force so
sharply that it will make very little contribution to base shear. Though only fixed
loads produce inertia forces, codes do require a small percentage of live load be
included with the dead load.
1.4 SEISMIC RISK ZONES
The location and intensity of major earthquake activity in the United States is
charted in figure 5.

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Fig.5: Intensity of major earthquake activity in the United States
1.5 SEISMIC RESPONSE OF BUILDING SYSTEMS
The magnitude of the earthquake inertia forces on a structure will vary with
the natural period of oscillation of the structure. The type of structural system thus
has a bearing on the magnitude of the inertia forces and the consequent base shear.
Codes separate the various structural systems in common use into groups that
have similar responses. Each system is assigned a response factor R (shown in Table
2.3). The response factor R take into account the relative rigidity of the structural
system. A very flexible structure will sway when subjected to motions at its base,
thereby reducing the base shear considerably. In contrast, a low rigid building having
a stiff structural system can actually undergo accelerations as much as 2×1/2 times as
large as ground accelerations.
The structural systems that are most likely to utilize shallow spread footings
are the low diaphragm shear wall structures; in these structures, walls carry all lateral
loads. Typically, these structures are low and rigid, having heights less than 65 feet
and periods less than 0.7 seconds.
The moment resistant frames are more likely to be used for taller structures;
they are not often competitive in cost for lower buildings.

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CHAPTER 2
METHODOLOGY
2.1 SOIL PROFILE TYPE FOR A BUILDING SITE
Earthquake forces are called inertia forces which are related to the mass,
stiffness and energy absorbing characteristics of the structure. The magnitude of the
earthquake inertia forces is also dependent on the type of soil at the site as well as its
strength and its depth.
2.1.1 Inertia Forces on Structures
Earthquake causes shaking of the ground. So a building resting on it will
experience motion at its base. From Newton’s First Law of Motion, even though the
base of the building moves with the ground, the roof has a tendency to stay in its
original position. But since the walls and columns are connected to it, they drag the
roof along with them. This tendency to continue to remain in the previous position is
known as inertia. In the building, since the walls or columns are flexible, the motion
of the roof is different from that of the ground as shown in figure 6.
Fig. 6: Effect of inertia in a building
2.1.2 Flow of Inertia Forces to Foundations
Under horizontal shaking of the ground, horizontal inertia forces are generated
at level of the mass of the structure (usually situated at the floor levels). These lateral
inertia forces are transferred by the floor slab to the walls or columns, to the
foundations, and finally to the soil system underneath.
2.2 SEISMIC DESIGN REQUIREMENTS
The two most important elements of concern to a structural engineer are
calculation of seismic design forces and the means for providing sufficient ductility.

11. 11
Based on the risk zone Z of a building site, the soil profile type for the site and
the type of structural system to be used, an average seismic coefficient for the
structure is defined by the Tables of values for two such coefficients Ca and Cv are
given in Table 2.1 and Table 2.2, respectively.
Table 2.1: Seismic Coefficient Ca
Soil
Profile
Seismic Zone
Factor, Z
Type Z = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4
SA 0.06 0.12 0.16 0.24 0.32 Nv
SB 0.08 0.15 0.2 0.3 0.40 Nv
SC 0.09 0.18 0.24 0.33 0.40 Nv
SD 0.12 0.22 0.28 0.36 0.44 Nv
SE 0.19 0.3 0.34 0.36 0.36 Nv
SF See Footnote1
1Site-specific geotechnical investigation and dynamic site response analysis shall be performed to
determine seismic coefficient for Soil Profile Type SF
Table 2.2: Seismic Coefficient Cv
Soil
Profile
Seismic Zone
Factor, Z
Type Z = 0.075 Z = 0.15 Z = 0.2 Z = 0.3 Z = 0.4
SA 0.06 0.12 0.16 0.24 0.32 Nv
SB 0.08 0.15 0.20 0.30 0.40 Nv
SC 0.13 0.25 0.32 0.45 0.54Nv
SD 0.18 0.32 0.40 0.54 0.64Nv
SE 0.26 0.50 0.64 0.84 0.96 Nv
SF See Footnote1
1Site-specific geotechnical investigation and dynamic site response analysis shall be performed to
determine seismic coefficient for Soil Profile Type SF
2.2.1 Calculations of Base Shear Due to Earthquake
In recognition of all the foregoing influences, Code specifies the value of the
design base shear V based on the average acceleration of the superstructure:
𝑉 =
𝐶 𝑣 𝐼
𝑅𝑇
𝑊 (1)

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Where,
Cv is an average seismic coefficient specified by Code, given in Table 2.2
I is the importance factor
R is the interactive response factor specified by Code, given in Table 2.3
T is the natural period of the structure
W is the dead weight of the structure
For simplicity in all following discussions, the importance factor I is again
taken at its base value of 1.0.
Table 2.3: Value of R factor for most common structural systems
S.No. Lateral force resisting system description R
1 Special Moment Resisting Frame Systems. 8
2
Dual System With Special Moment Resisting Frames which are
capable to resist at least 50% of Prescribed Seismic Force 7.5
3
Dual System With Special Moment Resisting Frames which are
capable to resist at least 25% of Prescribed Seismic Force. 6.5
4
Dual System With Special Moment Resisting Frames which are
capable to resist at least 10% of Prescribed Seismic Force. 5.5
5
Bearing Shear Wall System without Special Moment Resisting
Frames 4.5
For the low structures (about 65 feet or less) that are likely to be founded on
shallow foundations, the calculations of the base shear can be simplified considerably
over the calculations required for higher structures. In the low structures that are of
primary interest here, the upper bound for the base shear is also specified by Code.
𝑉 =
2.5𝐶 𝑎 𝐼
𝑅
𝑊 (2)
Where,
Ca is an average seismic coefficient given in Table 2.1
Code gives equation (2) as an absolute upper bound on all values computed
from equation (1). For the low structures of interest here, the upper bound is found to
be the applicable equation for most structures up to about 50 feet high, and is only
slightly in error up to about 70 feet. In all cases the error is on the “safe” side.
Adopting the upper bound for the design of routine shallow foundations
provides a worthwhile simplification of the design procedure.

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Experimentation with equation (2) reveals that for a low structure founded on
shallow spread footings, the maximum earthquake force will be about 10% to 13% of
the vertical dead load. In areas of light earthquake intensity, the lateral load may drop
to as little as 2.5% of the dead load. These percentages of the vertical dead weight are
known as the “lateral g-load” or “lateral g-force” on the structure.
2.2.2 Overturning Moment Due to Earthquake
Since the base of the structure is securely anchored to the ground, the base
will undergo accelerations identical to the accelerations of the ground. The top of a
structure, however, can undergo accelerations as much as 2×1/2 times that of its base.
Such amplification maybe attributed either to the effects of partial resonance or the
effects of “whip” or a combination of both.
The overall effect of inverting the acceleration rates (zero at the base,
maximum at the top) is to increase markedly the inertia forces toward the top of the
structure. This “whip” effect also increases significantly the overturning moment
produced by these inertia forces.
The component of the base shear to be assigned to any level x between levels
from 1 to n is computed by multiplying the base shear V by the inertia factor Cx for
that level, or,
𝐹𝑥 = 𝐶 𝑥 𝑉
Where,
𝐶 𝑥 =
𝑊𝑥ℎ 𝑥
∑ 𝑊𝑖ℎ𝑖
Where,
Wi= dead load weight at the level i
hi = height of level i above the base
hn = height of the highest level
aavg= average acceleration (at hLAT)
The overturning moment Mov produced by these forces Fx is calculated as,
𝑀 𝑜𝑣 = ∑ 𝐹𝑖 ℎ𝑖
The location of the center of lateral inertia forces above the base, hLAT, is
calculated as,
ℎ 𝐿𝐴𝑇 =
𝑀 𝑜𝑣
𝑉

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As the base shear and the overturning moments are evaluated using above
equations, the total lateral and longitudinal load is obtained. The foundation is then
designed based on these seismic forces and moments.
For severe seismic zones, individual spread footing or pile caps should be
interconnected with ties, except when individual spread footing are directly supported
on rock. All ties should be capable of carrying, in tension and in compression, an
axial force equal to Ah/4 times the larger of the column or pile cap load, in addition to
the otherwise computed forces.
2.3 RESPONSE CONTROL
The conventional approach to seismic design of structures relies on the ductile
behavior of the structural system to dissipate the seismic energy through plastic
deformation cycles. Devices proposed and in use are either to prevent an earthquake
force from acting on a structure (isolators) or to absorb a portion of the earthquake
energy (dampers) that is introduced to the structure.
2.3.1 Base Isolation and Isolating Devices
In order for a structure to withstand the distortions resulting from the
earthquake motions, an adaptive system is designed to isolate the upper portions of a
structure from destructive vibrations, by confining the severe distortions to a specially
designed portion at its base. The building is detached or isolated from the ground in
such a way that only a very small portion of seismic ground motion is transmitted up
through the building (shown in figure 7).
A practical base isolation system should consist of the following:
 A flexible mounting to increase the period of vibration of the building
sufficiently to reduce forces in a structure above.
 A damper or energy dissipater to reduce the relative deflection between the
building and a ground to a practical level.
 A method of providing rigidity to control the behavior under minor
earthquakes and wind loads.
Fig.7: Base Isolation Technique

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2.3.2 Rubber Pads
Laminated rubber pads prevent ground motion from being transmitted from
the building foundation in the superstructure (shown in figure 8).
Fig.8: Structure of elastomer rubber pad
2.3.3 Lead Rubber Bearings
A lead rubber bearing is made from layers of rubber sandwiched together with
layers of steel. In the middle of the solid lead “plug”. On top and bottom, the bearing
is fitted with steel plates which are used to attach the bearing to the building and
foundation. The bearing is very stiff and strong in the vertical direction, but flexible
in the horizontal direction (shown in figure 9).
Fig.9: Lead rubber bearing
2.3.4 Spherical Sliding Base Isolation
Spherical sliding isolation systems are another type of base isolation. The
building is supported by bearing pads that have a curved surface and low friction.
During an earthquake the building is free to slide on the bearings. Since the bearings
have a curved surface, the building slides both horizontally and vertically. The forces
needed to move the building upwards limits the horizontal or lateral forces which
would otherwise cause building deformations (shown in figure 10).

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Fig.10: Spherical Sliding Base Isolation
2.4 RETROFITTING
Retrofitting is the process of modifying something after it has been
manufactured. Typically this is done with the expectation of improving strength and
performance of the building. The development of new technologies mean that
building retrofits can allow for significant reductions in energy caused due to
earthquake. Different retrofitting measures are described briefly:
 Adding shear wall/infill wall
 Adding bracing
 Adding wing wall/buttresses
 Wall thickening
 Masonry foundation retrofit
 Supplemental damping
2.4.1 Adding Shear Wall/Infill Wall
Shear walls and infill walls are vertical elements of the horizontal force
resisting system. When the sheathing is properly fastened to the stud wall framing,
the shear wall can resist forces directed along the length of the wall. They have the
strength and stiffness to resist the horizontal forces (shown in figure 11).
Fig.11: Shear wall and Infill wall
2.4.2 Adding Bracing
This is another way to stiffen the existing building. Adding diagonal cross
bracings (shown in figure 12) to the columns on a multi-storey building stiffens the
structural foundations and allows better shear resistance.

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Fig.12: Cross bracings
2.4.3 Adding Wing Wall/Buttress
These are not so popular since they require vacant area around the building.
Lateral strength of the building can be increased using wing walls (shown in figure
13).
Fig.13: Wing wall/Buttress
2.4.4 Wall Thickening
This is done by making grooves in an existing masonry wall and dowelling in
epoxy as shown in figure 14. A new set of reinforcements are made to anchor the
grooves which is finished with reinforced concrete. It increases strength and stiffness
of the structural members like slab, infill wall and shear wall.
Fig.14: Wall thickening

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2.4.5 Supplement Damping
The supplement damping devices are the viscous dampers, visco-elastic
dampers and frictional dampers (shown in figure 15). These are provided between
two adjacent columns like a bracing and they have the tendency to absorb shocks like
a shock up which in turn reduces the earthquake response.
Fig.15: Supplement Damping
2.4.6 Masonry Foundation Retrofit
The foundation can be retrofitted by drilling a gap through the foot of the wall
and add reinforcements with stirrups which contains connector keys that anchors it to
the wall as shown in figure 16. The reinforcements are then finished by concreting to
form and R.C. beam.
Fig.16: Strengthening of foundations

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REFERENCES
1. Samuel, E. French, (1930). “Design of Shallow Foundations” Lateral loads on
foundation, Reston, Virginia 20191-4400: 31-66.
2. S.K. Duggal, (2007). “Earthquake Resistance Design of Structures”, New
Delhi, 110001: 103-180.
3. Michael R. Lindeburg, (2011). “Seismic Design of Building Structures”,
California, 2011934772: 7-1 – 7-11.
4. Robert E. Englekirk, (2003). “Seismic Design of Reinforced and Precast
Concrete Buildings”, New Jersey, 2002008561: 738-753.