Earthquake Resistant Design Techniques

EARTHQUAKE RESISTANT CONSTRUCTION
DETAILS
Various types and construction details of foundation, soil
stabilization, retaining walls, underground and overhead tanks,
staircases and isolation of structures
UTKARSH SHAKYA (11601)
SAHIL KAUNDAL (11602)
B.Arch. ,7th
Sem.
National Institute of Technology Hamirpur
1

CONTENTS
1. Why earthquake resistant construction details?? (Introduction)
2. Various types and construction details of foundation.
3. Soil stabilization
4. Retaining walls
5. Underground and overhead tanks
6. Staircases and isolation of structures
2 AR-414 Earthquake Resistant Building Design Earthquake Resistant Construction Details

Why Earthquake resistant
construction??
India is a large country. Nearly two thirds of
its area is earthquake prone. A large part of
rural and urban buildings are low-rise
buildings of one two three storeys. Many of
them may not be adequately designed from
engineers trained in earthquake engineering.
Most loss of life and property due to
earthquakes occur due to collapse of
buildings. The number of dwelling units and
other related small-scale constructions might
double in the next two decades in India and
other developing countries of the world. This
amplifies the need for a simple engineering
approach to make such buildings
earthquake resistant at a reasonably low
cost.

Various types and construction
details of foundation

Types of Foundations:
Stone Masonry Foundation

Brick Masonry Foundation

Concrete Block Masonry Foundation
- In case of loose soil, provide some nominal
reinforcement in foundation bed concrete.
- If stone soling is used under foundation
reduce the thickness of foundation strip to 3”.
- The vertical steel bars indicated in the
foundations are to be provided at corners and
junction of walls as explained in the later
sections.

Foundations
One of the most frequent causes of deterioration of the walls of a house is their direct
contact with the ground humid thus making them vulnerable in the event of an
earthquake.
Example: ground sloping towards the wall,
unstable and poor quality foundations and
wall bases, prone to settling due to the effect
of humidity and the inferior quality of the
ground.

Alternative 1: Cleaning & Drainage
If after an earthquake the wall has cracks in certain
sections
and the bricks are in a satisfactory state we must
eliminate the
earth which covers the wall base, and level out the
ground a
minimum of 100mm below the wall base.
Alternative 2: Demolition & Reconstruction
If after an earthquake the base of the wall has become
loose,
if there are cracks in the entire wall and sinking which
makes
the wall unstable and dangerous, we must then:
Dismantle it
after propping it up and build a new wall from the
foundations.

WOOD FRAMED WALLS
Foundations
Timber construction shall preferably start above the plinth level, the portion below
being in masonry or concrete. The superstructure may be connected with the foundation
in one of the two ways:
A) The superstructure may simply rest on the plinth masonry, or in the case of
small buildings of one storey having plan area less than 50 sq.m., it may rest
on firm plane ground so that the building is free to slide laterally during ground
motion
B) The superstructure may be rigidly fixed into the plinth masonry or concrete
foundation as shown in fig.13.1 or in case of small buildings it may be fixed to
vertical poles embedded into the ground.
Details of connection of column
with foundation

Wall Footings
Pier Post and Column Footings

SHALLOW FOUNDATION - Spread Footings: Single footing, Stepped footin
Spread footings are those which spread the
super-imposed load of wall or column over a
larger area. Spread footings support either a
colunm or wall. Spread footings may be of the
following kinds:
(i) Single footing [ Fig. 2.2(a)] for a column
(ii) Stepped footing [ Fig. 2.2(b)] for a column
(iii) Sloped footing [ Fig. 2.2(c)] for a column
(iv) Wall footing without step [ Fig. 2.3(a)]
(v) Stepped footing for wall [ Fig. 2.3(b)]
(vi) Grillage foundation [ Fig. 2.4]

Fig. 2.2 SPREAD FOOTINGS FOR COLUMNS.
Fig. 2.2 (a) shows a single footing for a column, in which
the loaded area (b x b) of the column has been spread to the size
B x B through a single spread. The base is generally made of concrete.
Fig. 2.2 (b) shows the stepped footing for a heavily loaded column,
which requires greater spread. The base of the column is made of
concrete. Fig. 2.2 (c) shows the case in which the concrete base does
not have uniform thickness, but is made sloped, with greater thickness
at its junction with the column and smaler thickness at the ends.
FIG. 2.3 SPREAD FOOTING FOR WALL : STRIP
FOOTING.
Fig. 2.3 (a) shows the spread footing for a wall, consisting
of concrete base without any steps. Usually, masonry walls have
stepped footings as shown in Fig. 2.3 (b), with a concrete base

FIG. 2.4 GRILLAGE FOUNDATION.
Fig. 2.4 shows a steel grillge foundation for a steel stanchion carrying
heavy load. It is a special type of isolated footing generally provided
for heavily loaded steel stanchions and used in these locations where
bearing capacity of soil is poor. The depth of such a foundation is
limited to 1 to 1.5 m. The load of the stanchion is distributed or
spread to a very large area by means of two or mor tiers or rolled
steel joints, each layer being laid at right angle to the layer bellow it.
Both the tiers of the joists are then embeden in cement concrete to
keep the joists in position and to prevent their corrosion.
The detailed method of construction has benn explained in 3.6
Grillage foundation is also constructed of timber beams and planks
(Fig. 3.12 and 3.13)

General problems of ground instability
include:
• Landslip
• Surface flooding and soil erosion
• Natural caves and fissures
• Mining and quarrying
• Landfill
• Natural geological variation – faults,
changes in geology – differential settlement

Improving the ground
• There are a number of different methods that
can be used to increase the strength and
stability of the ground.

Ground stabilisation
• Dynamic compaction
• Vibro compaction - Vibro displacement
• Vibro flotation - high pressure water jets (improves
penetration of hard substrates)
• Pressure grouting
• Surcharging
• Geotechnic membranes
• Soil modification and stabilisation

Dynamic compaction
• This involves dropping heavy weights onto the
ground.
• The weight causes the ground to compact.

Dynamic compaction
• Ground is consolidated by repeatedly dropping dead
weights and specially designed tampers
• Weights include: Flat bottomed and cone tampers
• Traditional weights are flat bottomed with cable
• Modern systems use cones with guide rails
• Dynamic compaction is suitable for granular soils,
made-up and fill sites
• Using dynamic compaction bearing capacities of 50
to 150kN/m2
can be achieved

Dynamic
compaction Typical weight (mass) 7-11 tonnes
Tamer drops and exerts known
impact energy on strata
Pass 2 Pass 2Zone compacted
2nd Pass
Zone compacted
1st Pass
Pass 1 Pass 1
Zone compacted
3rd Pass
Sound strata
Pass 1 and
pass 2
Pass 3
50 – 150 kN/m2
Typical bearing
capacity
Required treatment
depth

Typical cone type tampers
(adapted from www.roger-
bullivant.co.uk)
Long cone Flower pot
cone
Multiple point
cone
Used for densifying
deep layers of
strata
Consolidates
strata closer to the
surface
Typical weight (mass) 7-11
tonnes
2.5
m
Traditional
weight
10 – 20 tonnes
Energy does not
penetrate the
ground as much as
the cone weights

Vibro compaction or displacement
• Vibrating rods are forced into the ground
causing the surrounding ground to compact
and consolidate.

Vibro compaction or vibro
displacement
• Vibrating mandrels (poker, shaft or rod) penetrates,
displaces and compacts the ground.
• Void Created is filled with stone and recompacted
• Produces stone columns in the ground, compacts
surrounding strata enhancing the ground bearing
capacity and limiting settlement
• Typical applications include support of foundations,
slabs, hard standings, pavements, tanks or
embankments.

Vibro compaction - continued
• Used in soft soils, man made and other strata, can be
reinforced to achieve improved specification
• On slopes it can limit the risk of slip failure.
• Ground bearing capacities, for low to medium rise
buildings and industrial developments, is in the
region of 100kN/m2
to 200kN/m2
.
• Improved ground conditions may allow heavier loads
to be supported.
• Used in granular and cohesive soils

Benefits of vibro-compaction
• Buildings can be supported on conventional
foundations (normally reinforced and shallow
foundations).
• Work can commence immediately following the vibro
displacement. Foundations can be installed straight
away.
• The soil is displaced. No soil is produced.
• Contaminants remain in the ground – reduces disposal
and remediation fees.
• Economical, when compared with piling or deep
excavation works.
• Can be used to regenerate brownfield sites
• Can use reclaimed aggregates and soils.

Vibrofloatation
• Vibro floatation uses a similar process to vibro
compaction
• Water jets at the tip of the poker
• Water jets help the vibrator penetrate hard
layers of ground
• Major disadvantage is that the system is
messy and imprecise, thus rarely used

Vibro displacement - Typical
sequence
2. As the mandrel drives into
the ground the soil is
displaced (surrounding
granular soil is compacted.
1. A grid is marked out and the
vibrating mandrel (poker) is
inserted to the required depth

Vibro displacement - Typical sequence
3. Having reached the engineered
depth the mandrel is withdraw and
hardcore is placed up to the first level.
The hardcore is built up in layers of 0.3
to 0.6m. The mandrel is inserted into the
hardcore, it penetrates and compacts
each layer before the next load of
hardcore is placed
Rigs weighs 14 – 55
tonnes
4. By compacting in layers
and reintroducing the cone
mandrel a dense stone
column is constructed.

Mandrel
positioned ready
to compact and
displace

Hardcore is repeatedly displaced and
compacted

Grouting
• Grouting may be used to fill the voids in the
ground increasing the strength of the ground.

Pressure grouting
• In permeable soils, pressure grouting may be used to
fill the voids.
• Holes drilled using mechanically driven augers.
• As the auger is withdrawn cement slurry is forced
down a central tube into the bore under pressure.
• Pressures of up to 70,000 N/mm2
can be exerted by
the grout on the surrounding soil.
• Slurry contains cementious additives, e.g. pulverised
fuel ash (pfa), microsilica, chemical grout, cement or
a mixture.

Soil modification and stabilization
• Machines are available that can break-up the
ground, mix the ground with new cementious
material and improve the ground quality.

Soil modification and recycling
• Additives used in soil stabilisation increase the
strength better, improve compacted and maximise
bearing capacity and minimise settlement.
• The technique can be used to provide stabilised or
modified materials for earthworks, or may be used
to provide permanent load transfer platforms or
hard standings.
• Can be used to treat and neutralise certain
contaminants or encapsulate the contaminants,
removing the need for expensive removal and
disposal.

Soil modification, stabilisation and
recycling machine
Milling and mixing chamber
Working direction
Unstable soil Stable or modified
soil ready for
compaction

Schematic of
soil modification and mixing chamber
The milling and mixing
rotor breaks down soil
and mixes the soil and
additives
Hopper and cellular wheel
sluice spread lime or cement
or other additive
Variable milling and mixing
chamber.
Soil mixture with reduced
water content – ready for
compaction
Working direction

Soil modification and stabilization rig
www. roger-bullivant.co.uk

Soil modification and stabilization
plant
www. roger-bullivant.co.uk

Surcharging
• This involves placing heavy loads on the ground for
long periods of time.
• Over time the ground will compact.
• Surcharging is time consuming and ties up the land
• Can be used if long lead-in time available
• Can be used on roads
• May be used on investment land (land bank). The
increase in strength will increase the value of the
land.

Surcharging
• Excavated material, quarried stone or other
heavy loads.
• Settlement and compaction period 6 months
to a few years.
• For economics the surcharging acts as a
temporary storage facility

Geotechnical membranes
• Geotechnical membranes provide a sheet of
reinforcing material that can be added to the
ground. This increases the stability and
tensile strength of the ground.

Geotechnical membranes
• Natural
• Plastic manmade
• Built up in layers compacted between ground
hardcore
• Sheets, fibres and strips

59
5. Field Compaction Equipment
and Procedures

60
5.1 Equipment
Smooth-wheel roller (drum) • 100% coverage under the wheel
• Contact pressure up to 380 kPa
• Can be used on all soil types
except for rocky soils.
• Compactive effort: static weight
• The most common use of large
smooth wheel rollers is for proof-
rolling subgrades and compacting
asphalt pavement.
Holtz and Kovacs, 1981

61
5.1 Equipment (Cont.)
Pneumatic (or rubber-tired) roller • 80% coverage under the wheel
• Contact pressure up to 700 kPa
• Can be used for both granular and
fine-grained soils.
and kneading.
• Can be used for highway fills or
earth dam construction.

62
Sheepsfoot rollers • Has many round or rectangular
shaped protrusions or “feet”
attached to a steel drum
• 8% ~ 12 % coverage
• Contact pressure is from 1400 to
7000 kPa
• It is best suited for clayed soils.
and kneading.

63
Tamping foot roller • About 40% coverage
8400 kPa
• It is best for compacting fine-
grained soils (silt and clay).
and kneading.

64
Mesh (or grid pattern) roller • 50% coverage
6200 kPa
• It is ideally suited for compacting
rocky soils, gravels, and sands.
With high towing speed, the
material is vibrated, crushed, and
impacted.
and vibration.

65
Vibrating drum on smooth-wheel
roller
• Vertical vibrator attached to
smooth wheel rollers.
• The best explanation of why roller
vibration causes densification of
granular soils is that particle
rearrangement occurs due to cyclic
deformation of the soil produced
by the oscillations of the roller.
and vibration.
• Suitable for granular soils

66
5.1 Equipment-Summary

67
5.2 Variables-Vibratory
Compaction
•There are many variables which control the vibratory
compaction or densification of soils.
•Characteristics of the compactor:
•(1) Mass, size
•(2) Operating frequency and frequency range
•Characteristics of the soil:
•(1) Initial density
•(2) Grain size and shape
•(3) Water content
•Construction procedures:
•(1) Number of passes of the roller
•(2) Lift thickness
•(3) Frequency of operation vibrator
•(4) Towing speed Holtz and Kovacs, 1981

68
5.3 Dynamic Compaction
Dynamic compaction was first used in
Germany in the mid-1930’s.
The depth of influence D, in meters, of soil
undergoing compaction is conservatively
given by
D ≈ ½ (Wh)1/2
W = mass of falling weight in metric tons.
h = drop height in meters
From Holtz and Kovacs, 1981

69
5.4 Vibroflotation
From Das, 1998
Vibroflotation is a technique for
in situ densification of thick
layers of loose granular soil
deposits. It was developed in
Germany in the 1930s.

70
5.4 Vibroflotation-Procedures
Stage1: The jet at the bottom of the Vibroflot is turned on and lowered into the ground
Stage2: The water jet creates a quick condition in the soil. It allows the vibrating unit to
sink into the ground
Stage 3: Granular material is poured from the top of the hole. The water from the lower
jet is transferred to he jet at the top of the vibrating unit. This water carries the granular
material down the hole
Stage 4: The vibrating unit is gradually raised in about 0.3-m lifts and held vibrating for
about 30 seconds at each lift. This process compacts the soil to the desired unit weight.
From Das, 1998

71
6. Field Compaction
Control and Specifications

72
6.1 Control Parameters
• Dry density and water content correlate well with the
engineering properties, and thus they are convenient
construction control parameters.
• Since the objective of compaction is to stabilize soils and
improve their engineering behavior, it is important to keep in
mind the desired engineering properties of the fill, not just its
dry density and water content. This point is often lost in the
earthwork construction control.

73
6.2 Design-Construct Procedures
• Laboratory tests are conducted on samples of the proposed
borrow materials to define the properties required for design.
• After the earth structure is designed, the compaction
specifications are written. Field compaction control tests are
specified, and the results of these become the standard for
controlling the project.

74
6.3 Specifications
(1) End-product specifications
•This specification is used for most highways and building
foundation, as long as the contractor is able to obtain the
specified relative compaction , how he obtains it doesn’t matter,
nor does the equipment he uses.
•Care the results only !
•(2) Method specifications
•The type and weight of roller, the number of passes of that
roller, as well as the lift thickness are specified. A maximum
allowable size of material may also be specified.
•It is typically used for large compaction project.

75
6.6.1 Destructive
Methods
Methods
(a) Sand cone
(b) Balloon
(c) Oil (or water) method
Calculations
•Know Ms and Vt
•Get ρd field and w (water content)
•Compare ρd field with ρd max-lab and
calculate relative compaction R.C.
(a)
(b)
(c)

76
6.6.1 Destructive Methods (Cont.)
•Sometimes, the laboratory maximum density may not be
known exactly. It is not uncommon, especially in highway
construction, for a series of laboratory compaction tests to be
conducted on “representative” samples of the borrow materials
for the highway. If the soils at the site are highly varied, there
will be no laboratory results to be compared with. It is time
consuming and expensive to conduct a new compaction curve.
The alternative is to implement a field check point, or 1 point
Proctor test.

77
6.6.1 Destructive Methods (Cont.)
• The measuring error is mainly from the determination of
the volume of the excavated material.
• For example,
• For the sand cone method, the vibration from nearby working
equipment will increase the density of the sand in the hole, which will
gives a larger hole volume and a lower field density.
• If the compacted fill is gravel or contains large gravel particles. Any
kind of unevenness in the walls of the hole causes a significant error in
the balloon method.
• If the soil is coarse sand or gravel, none of the liquid methods works
well, unless the hole is very large and a polyethylene sheet is used to
contain the water or oil.
tsfieldd V/M=ρ −

78
6.6.2 Nondestructive
Methods
Nuclear density meter
(a) Direct transmission
(b) Backscatter
(c) Air gap
(a)
(b)
(c)
Principles
Density
The Gamma radiation is scattered by the soil
particles and the amount of scatter is
proportional to the total density of the material.
The Gamma radiation is typically provided by
the radium or a radioactive isotope of cesium.
Water content
The water content can be determined based on
the neutron scatter by hydrogen atoms. Typical
neutron sources are americium-beryllium
isotopes.

79
6.6.2 Nondestructive Methods
(Cont.)
•Calibration
•Calibration against compacted materials of known density is
necessary, and for instruments operating on the surface the
presence of an uncontrolled air gap can significantly affect the
measurements.

80
7. Estimating Performance of
Compacted Soils

81
7.1 Definition of Pavement
Systems

STORAGE TANKS
82AR-414 Earthquake Resistant Building Design Earthquake Resistant Construction Details

In general there are three kinds of water tanks-
1.Tanks resting on ground,
2.Underground tanks and
3.Elevated tanks.

From design point of view the tanks may be classified as per
their shape-
RECTANGULAR TANKS
CIRCULAR TANKS
INTZE TYPE TANKS
SPHERICAL TANKS
CONICAL BOTTOM TANKS
SUSPENDED BOTTOM TANKS.

The tanks resting on
ground like clear water
reservoirs, settling tanks,
aeration tanks etc. are
supported on the ground
directly.
• The walls of these tanks are
subjected to pressure and the
base is subjected to weight of
water and pressure of soil.
•The tanks may be covered on
top.

The tanks like purification tanks,
Imhoff tanks, septic tanks, and
gas holders are built
UNDERGROUND.
1. The walls of these tanks are
subjected to water pressure from
inside and the earth pressure
from outside.
2. The base is subjected to
weight of water and soil
pressure. These tanks may be
covered at the top.

ELEVATED
TANKS are supported on
staging which may consist of
masonry walls, R.C.C. tower
or R.C.C. columns braced
together. The walls are
subjected to water pressure.
The base has to carry the
load of water and tank load.
The staging has to carry load
of water and tank.
The staging is also designed
for wind forces.

1. Ground Supported Rectangular
Concrete Tank

2. Elevated Tank Supported on 4 Column RC
Staging

3. Elevated Intze Tank Supported on 6
Column RC Staging

DESIGN OF RCC OVERHEAD WATER TANKS -
TERMINOLOGY -
1. Capacity - Capacity of the tank shall be the volume of water it can
store between the designed full supply level and lowest supply level ( that
is, the level of the lip of the outlet pipe ). Due allowance shall be made
for plastering the tank from inside if any when calculating the capacity of
tank.
2. Height of Staging - Height of staging is the difference between the
lowest supply level of tank and the average ground level at the tank site.
3. Water Depth - Water depth in tank shall be difference of level between
lowest supply level and full supply level of the tank.

LAYOUT OF OVERHEAD TANKS
Generally the shape and size of elevated concrete tanks for
economical design depends upon the functional requirements
such as:
a) Maximum depth for water;
b) Height of staging;
c) Allowable bearing capacity of foundation strata and type of
foundation suitable;
d) Capacity of tank; and
e) Other site conditions.

Classification and Layout of Elevated Tanks -
 1. For tank up to 50 m3 capacity may be square or circular in
shape
 and supported on staging three or four columns.
 2. Tanks of capacity above 50 m3 and up to 200 m3 may be
square or circular in plan and supported on minimum four
columns.
 3. For capacity above 200 m3 and up to 800 m3 the tank may be
square, rectangular, circular or intze type tank. The number of
columns to be adopted shall be decided based on the column
spacing which normally lies between 3.6 and 4.5 m. For
circular, intze or conical tanks, a shaft supporting structures
may be provided.

Bracings
For staging of height above foundation greater than 6 m, the
column shall be rigidly connected by horizontal bracings suitably
spaced vertically at distances not exceeding 6 m.

DETAILING -

Bibliography -
• Emmitt, S. and Gorse, C. (2010) Barry’s Introduction to Construction of
Buildings. Oxford, Blackwell Publishing
• Emmitt, S. and Gorse, C. (2010) Barry’s Advanced Construction of Buildings.
Oxford, Blackwell Publishing
• IS: 11682-1985 (CRITERIA FOR DESIGN OF RCC STAGING FOR
OVERHEAD WATER TANKS).
• IITK-GSDMA GUIDELINES for SEISMIC DESIGN OF LIQUID STORAGE
TANKS.
• Google Images.

107
Thanks to one and all…..
Presented to,
Ar. Anju soni mam
on,
9th
October 2014
AR-414 Earthquake Resistant Building Design Earthquake Resistant Construction Details

Earthquake Resistant Design Techniques

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