The document provides a detailed overview of cyclones, including their definitions, classifications, mechanisms, and the potential dangers they pose, particularly in India. It highlights the importance of cyclone naming conventions and outlines measures for cyclone disaster prevention and mitigation. Additionally, it discusses design considerations for buildings in cyclone-prone areas to minimize damage from high winds and flooding.

1. Cyclone and Fire
Shushant Tyagi
Student
Gurukul the school

2. What are Cyclones?




"Cyclone" is an intense whirl in the atmosphere
with very strong winds circulating around it in
anti-clockwise direction in the Northern
Hemisphere and in clockwise direction in the
Southern Hemisphere.
Word "Cyclone" is derived from the Greek, word
"Cyclos" meaning the coils of a snake.
To Henri Peddington, the tropical storms in the
Bay of Bengal and in the Arabian Sea appeared
like the coiled serpents of the sea and he named
these storms as "Cyclones".
known as Hurricane in the Atlantic and Eastem
Pacific, Typhoon in Western Pacific, Willy-Willies
in Australian sea, Baguis in the Philippines.

3. 
Cyclones are intense low pressure areas from the centre of which pressure
increases outwards- The amount of the
pressure drop in the centre and the rate at
which it increases outwards gives the
intensity of the cyclones and the strength
of winds.

4. Criteria followed to classify cyclones

As adopted by
Meteorological
Department of India
S.No.
Disturbance
1 knot - 1.85 km per hour
Wind Speed (Knots)
1.
Low
Less than 17.
2.
Depression
17-27(32-50 km/h)
3.
Deep Depression
28-33 (51-62 km/h)
4.
Cyclonic storm
34-47 (63-88 km/h)
48-63-(89-118 km/h)
5.
Severe cyclonic storm with
a core of Hurricane
winds

5. Mechanism of cyclones

7. Mechanism of cyclones






A full-grown cyclone is a violent whirl in the atmosphere 150 to
1000 km across, 10 to 15 km high.
The central calm region of the storm is called the "Eye". The
diameter of the eye varies between 30 and 50 km and is a region
free of clouds and has light winds.
Around this calm and clear eye, there is the "Wall Cloud Region"
of the storm about 5O km in extent, where the gale winds, thick
clouds with torrential rain, thunder and lightning prevail.
Away from the "Wall Cloud Region", the wind speed gradually
decreases.
The gales give rise to a confused sea with waves as high as 20
metres, swells that travel a thousand miles. Torrential rains,
occasional thunder and lightning flashes - join these
Through these churned chaotic sea and atmosphere, the cyclone
moves 300 to 500 km, in a day to hit or skirt along a coast,
bringing with it strome surges

8. Mechanism of cyclones





Once the cyclones reach higher latitudes they often change
their direction and move north and then north-east (south
and south east hemisphere). The process is known as
recurreature.
Before it recurves, the speed decreases and the system
remains stationary for a day or so.
When two cyclones exist near to each other, they inter-act
and move anti-clockwise with respect to each other.
In the Atlantic, tracks often execute a parabola.
In India, when cyclones recur they get broken up over the
Himalayas and their further eastward movement ceases.

9. Naming of cyclone

Cyclones derive their names through a systematic procedure laid
down by the World Meteorological Organisation (WMO) and the
United Nations Economic and Social Commission for Asia and the
Pacific (ESCAP).

naming of cyclones began in September 2004

Eight north Indian Ocean countries - Bangladesh, India, the
Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand have prepared a list of 64 names.

Since 2004, the eight countries have faced 20 cyclones.
The countries take turns in naming the cyclones. The last six
were: Nargis (Pakistan), Rashmi (Sri Lanka), Khai-Muk (Thailand),
Nisha (Bangladesh), Bijli (India) and Aila (Maldives).

10. Cyclone Map of India

11. The principal dangers of a cyclone
Gales and strong winds


damage installations, dwellings, communication
systems, trees., etc. resulting in loss of life and
property.
Torrential rain


may cause river floods
Storm surges or high tidal waves



A storm surge is an abnormal rise of sea level near
the coast caused by a severe tropical cyclone
as a result, sea water inundates low lying areas of
coastal regions drowning human beings and livestock, eroding beaches and embankments, destroying
vegetation and reducing soil fertility.

12. What is Storm Surge?

14. How high will the Storm Surge be?

Every cyclone that affects the coast produces a storm
surge. But not all storm surges rise to dangerous levels.
The height of the surge depends on:





The intensity of the cyclone - as the winds increase, the sea
water is piled higher and the waves on top of the surge are
taller.
The forward speed of the cyclone - the faster the cyclone
crosses the coast, the more quickly the surge builds up and
the more powerfully it strikes.
The angle at which the cyclone crosses the coast - local zones
of enhanced surge in areas such as narrow inlets and bays.
The shape of the sea floor - the surge builds up more strongly
if the slope of the sea bed at the coast is shallow.
Past history indicates that loss of life is significant when
surge magnitude is 3 metres or more and catastrophic
when 5 metres and above

15. Surge prone coasts of India


Vulnerability to storm surges is not uniform along Indian
coasts.
east coast of India are most vulnerable to high surges




i) North Orissa, and West Bengal coasts.
ii) Andhra Pradesh coast between Ongole and Machilipatnam.
iii) Tamil Nadu coast, south of Nagapatnam.
The West coast of India is less vulnerable to storm surges


i) Maharashtra coast, north of Harnai and adjoining south
Gujarat coast and the coastal belt around the Gulf of
Bombay.
ii) The coastal belt around the Gulf of Kutch.

16. Cyclone Accounts



The oldest and the worst cyclone on record is that of
October 1737: hit Calcutta and took a toll of 3,00,000
lives in the deltaic region. It was accompanied by a 12
metre high surge.
Midnapore Cyclone of October 1942 was accompanied by
gale wind speed of 225 kmph
Rameswaram Cyclone of 17th to 24th December 1964
wiped out Dhanuskodi in Rameswaran Island from the
map. A passenger train which left Rameswaram Road
station near about the midnight of 22nd was washed off
by the storm surges sometimes later, nearly all
passengers traveling in the train meeting water graves.

17. Cyclone Accounts


Bangla Desh Cyclone of 8-13 November 1970
which crossed Bangla Desh coast in the night of
12th was one of the worst in recent times, with
storm surges of 4 to 5 metres height at the
time of high tides, and with 25 cm of rain in the
areas, the inundation took toll of about
3,00,000 people.
Andhra Cyclone of 14-20 November 1977 that
crossed coast near Nizampatnam in the evening
of 19th, took a toll of about 10,000 lives.

18. How to avoid the catastrophe?

Effective Cyclone Disaster Prevention
and Mitigation Plan requires:




A Cyclone Forecast - and Warning Service.
Rapid dissemination of warnings to the
Government Agencies, Marine interests like the
Ports, Fisheries and Shipping and to General
Public.
Organisations to construct Cyclone Shelters in
the cyclone-prone areas and ready machinery
for evacuation of people to safer areas.
Community preparedness at all levels to meet
the exigencies.

19. Cyclone warning

"Two Stage Warning Scheme“



The first stage warning known as the "Cyclone Alert" is
issued 48 hours in advance of the expected
commencement of the adverse weather over the coastal
areas.
The second stage warning known as the "Cyclone
Warning" is issued 24 hours in advance.
Both cyclone "Alert" and "Warning" messages are
passed to the AIR stations for repeated broadcast.

20. Vulnerable Communities


vulnerability of a human settlement to a cyclone is
determined by its siting, the probability that a cyclone will
occur, and the degree to which its structures can be
damaged by it.
most vulnerable to cyclones are





Light weight structures with wood frames, especially older
buildings where wood has deteriorated and weakened the
walls
Houses made of unreinforced or poorly-constructed concrete
block
Buildings in low- lying coastal areas or river floodplains
Furthermore, the degree of exposure of land and buildings will
affect the velocity of the cyclone wind at ground level,
Certain settlement patterns may create a "funnel effect" that
increases the wind speed between buildings, leading to even
greater damage.

21. How High Winds Damage Buildings




Contrary to popular belief, few houses are blown over.
Instead, they are pulled apart by winds moving swiftly
around and over the building. This lowers the pressure on
the outside and creates suction on the walls and roof,
effectively causing the equivalent of an explosion.
Whether or not a building will be able to resist the effects
of wind is dependent not so much upon the materials that
are used but the manner in which they are used.
common belief: that heavier buildings, such as those made
of concrete block, are safer.
Truth: well-built and properly-engineered masonry house
offers a better margin of safety than other types of
buildings

22. Catastrophic Failures

Foundations


The uplift forces from
cyclone winds can
sometimes pull buildings
completely out of the
ground.
In contrast to designing
for gravity loads, the
lighter the building the
larger (or heavier) the
foundation needs to be in
cyclone resistant
design.

23. Catastrophic Failures

Steel Frames



A common misconception: the loss of cladding relieves
the loads from building frameworks.
Truth: the wind loads on the structural frame increases
substantially with the loss of cladding
Usual weakness in steel frames is in the connections.
Thus economising on minor items (bolts) has led to the
overall failure of the major items (columns, beams and
rafters)

24. Catastrophic Failures

Masonry Houses


usually regarded as being safe in cyclones.
There are countless examples where the loss
of roofs has triggered the total destruction of
un-reinforced masonry walls.

25. Catastrophic Failures

Timber Houses


The key to safe construction of timber houses
is the connection details.
The inherent vulnerability of light-weight
timber houses coupled with poor connections is
a dangerous combination which has often led
to disaster.

26. Catastrophic Failures

Reinforced Concrete Frames



The design of reinforced concrete frames is
usually controlled by the seismic hazard.
If seismic design is not done, wind analysis
must be performed
ignoring this, can lead to disaster.

27. Component Failures

Roof Sheeting


This is perhaps the
commonest area of
failure in cyclones.
The causes are usually
inadequate fastening
devices, inadequate
sheet thickness and
insufficient frequencies
of fasteners in the
known areas of greater
wind suction.

28. Catastrophic Failures

Roof Tiles

These were thought to have low vulnerability in
storms but past cyclones have exposed the
problem of unsatisfactory installation practices.

29. Catastrophic Failures

Rafters


Of particular interest in
recent cyclones was the
longitudinal splitting of
rafters with the top
halves disappearing and
leaving the bottom halves
in place.
The splitting would
propagate from holes
drilled horizontally
through the rafters to
receive holding-down
straps.

30. Catastrophic Failures

Windows and Doors




After roof sheeting, these are the components most
frequently damaged in cyclones.
Of course, glass would always be vulnerable to flying
objects.
The other area of vulnerability for windows and doors is
the hardware latches, bolts and hinges.
Walls


Cantilevered parapets are most at risk.
But so far walls braced by ring beams and columns have
remained safe.

31. Damaging Effects of Cyclone on
Houses

Due to the
high wind
pressure and
improper
connection of
the house to
the footings it
can be blown
away.

32. Damaging Effects of Cyclone on
Houses
Roofing
materials not
anchored
can be blown
away

33. Damaging Effects of Cyclone on
Houses
Light
weight
verandah
roofs are
more
susceptible
to damage
due to
high wind
speed.

34. Damaging Effects of Cyclone on
Houses

When cyclones
are accompanied
with heavy rain
for a long
duration, the
buildings can be
damaged due to
flooding also.

35. Design Wind Speed and Pressures

The basic wind speed is reduced or enchanced for
design of buildings and structures due to
following factors:



The risk level of the structure measured in terms of
adopted return period and life of structures.
Terrain roughness determined by the surrounding
buildings or trees and, height and size of the structure.
Local topography like hills, valleys, cliffs, or ridges, etc.

36. On which elements the wind pressure
effect must be considered?

It is considered on various elements
depends on




Aerodynamics of flow around buildings.
The windward vertical faces being subjected to
pressure.
The leeward and lateral faces getting suction
effects and
The sloping roofs getting pressures or suction
effects depending on the slope.

37. typical effects of openings in the walls
Wind generating
opening on the
windward side during a
cyclone will increase
the pressure on the
internal surfaces
 may be sufficient to
cause the roof to blow
off and the walls to
explode.


38. typical effects of openings in the walls
Windward face of the building
collapses under pressure of wind
force

39. typical effects of openings in the walls


During a cyclone an opening may suddenly occur
on the windward side of the house.
The internal pressure which builds up as a result
may be relieved by providing a corresponding
opening on the leeward side.

40. 
If the building is not securely tied to its
foundations, and the walls cannot resist
push/pull forces, the house tends to collapse
starting from the roof with the building leaning
in the direction of the wind.

41. 
Failure of the Wall: Wind forces on the walls of
the house may produce failure. Wind striking a
building produces pressure which pushes against
the building, on the windward side, and suction
which pulls the building on the leeward side and
the roof.

42. 
Overturning is another problem for light
structures.

This occurs when the weight of the house is insufficient
to resist the tendency the house to be blown over.

43. When choosing a site for your house,
consider the following





Though cyclonic storms always approach from the direction of the sea
towards the coast, the wind velocity and direction relative to a building
remain random due to the rotating motion of the high velocity winds.
In non-cyclonic region where the predominant strong wind direction is well
established, the area behind a mound or a hillock should be preferred
Similarly a row of trees planted upwind will act as a shield.
The influence of such a shield will be over a limited distance, only for 8 –
10 times the height of the trees.
A tree broken close to the house may damage the house also hence
distance of tree from the house may be kept 1.5 times the height of the
tree.

44. When choosing a site for your
house, consider the following
No shielding from high wind due to Shielding from high wind by
absence of barriers
permeable barriers such as strong
trees

45. When choosing a site for your
house, consider the following

In hilly regions,


construction along ridges should be avoided
since they experience an increase of wind
velocity
whereas valley experiences lower speeds in
general

46. When choosing a site for your
house, consider the following

In cyclonic regions close to the coast, a site above the
likely inundation level should be chosen. In case of non
availability of high level natural ground, construction should
be done on stilts with no masonry or cross bracings up to
maximum surge level, or on raised earthen mounds to
avoid flooding/inundation but knee bracing may be used.

47. Shape of the House






Shape is the most important single factor in determining
the performance of buildings in cyclones.
Simple, compact, symmetrical shapes are best.
The square plan is better than the rectangle since it allows
high winds to go around them.
The rectangle is better than the L-shaped plan.
This is not to say that all buildings must be square. But it is
to say that one must be aware of the implications of design
decisions and take appropriate action to counter negative
features.
The best shape to resist high winds is a square.

48. Shape of the House
If other shapes are desired, efforts should be made to strengthen the
corners.
If longer shapes are used, they must be designed to withstand the forces of
the wind.
Most houses are rectangular and the best layout is when the length is not
more than three (3) times the width.

49. 
In case of construction of group of
buildings, a cluster arrangement can be
followed in preference to row type.

50. Roofs
Lightweight flat roofs are easily blown off
in high winds.
 In order to lessen the effect of the
uplifting forces on the roof, the roof Pitch
should not be less than 22º.
 Hip roofs are best


51. Roofs

General Design Considerations



Avoid a low pitched roof, use a hip roof or a
high pitched gable roof.
Avoid overhanging roofs. If overhangs or
canopies are desired, they should be braced by
ties held to the main structures.
Avoid openings which cannot be securely
closed during a cyclone

52. Overhangs, verandahs
Avoid large overhangs as high wind force
build up under them.
 Overhangs should not be more than 18
inches at verges or eaves.
 Build verandah and patio roofs as separate
structures rather than extensions of the
main building.


53. Securing the Ridge
If the rafters are not secure, the ridge can fall apart when
strong wind passes over the roof.

54. Securing the Ridge

The ridge can be secured by using:
COLLAR TIES - Timbers connecting the rafters.
Nail them to the side of the rafters

55. Securing the Ridge

GUSSETS - Usually made of
steel/plywood. This is used at the ridge.

56. Securing the Ridge

METAL STRAPS over the top of the rafters

57. Securing the corrugated galvanized
sheets
The sheets are gauged by numbers. The
Higher the number the thinner the
material. Example 24 gauge galvanized
sheet is superior to 28 gauge.
 Failure in roofs



If the sheeting is too thin or there are too few
fittings, the nails or screws may tear through
the sheet.
If galvanized sheets are used, 24 gauge is
recommended.

58. Securing the corrugated
galvanized sheets

How to secure sheeting to the roof
structure, use


Fixings every two (2) corrugation at ridges,
eaves and overhangs.
Fixings every three (3) corrugation. Maximum
spacing at all other locations

60. Fixings for sheetings

Screws




Use proper drive crews for corrugated galvanized roof
sheets.
Be sure that the screws go into the purlins at least fifty
(50) mm.
use large washers under the screw heads to prevent the
roof sheets from tearing
Nails



Nails do not hold as well as screws.
Use nails with wide heads and long enough to bend over
below the lath.
Galvanized coated nails are better than ordinary wire
nails.

61. Roof cladding


As the corners and the roof edges are zones of higher local
wind suctions and the connections of cladding/sheeting to
the truss need to be designed for the increased forces.
following precautions are recommended:

Sheeted roofs:- A reduced spacing of bolts, ¾ of that
admissible as per IS:800, recommended.
For normal connections, J bolts may be used but for cyclone
resistant connections U – bolts are recommended.

62. 
Alternatively, strap may be used at least
along edges to fix cladding with the purlins
to avoid punching through the sheet.

63. 
Clay tile roofs:- Because of lower dead
weight, these may be unable to resist the
uplifting force and thus experience heavy
damage, particularly during cyclones.


Anchoring of roof tiles in R.C. strap beams is
recommended for improved cyclone resistance.
As alternative to the bands, a cement mortar
screed, reinforced with galvanized chicken
mesh, may be laid over the high suction areas
of the tiled roof.

64. Foundations
The foundation is the part of the house
which transfers the weight of the building
to the ground. It is essential to construct a
suitable foundation for a house as the
stability of a building depends primarily on
its foundation.
 It is desirable that information about soil
type be obtained and estimates of safe
bearing capacity


65. Parameters need to be properly accounted
in the design of foundation

Effect of surge or flooding:




Invariably a cyclonic storm is accompanied by torrential rain
and tidal surge (in coastal areas) resulting into flooding of the
low lying areas.
Flooding causes saturation of soil and thus significantly affects
the safe bearing capacity of the soil.
In flood prone areas, the safe bearing capacity should be taken
as half of that for the dry ground.
Also the likelihood of any scour due to receding tidal surge
needs to be taken into account while deciding on the depth of
foundation
Buildings on stilts:

Where a building is constructed on stilts it is necessary that
stilts are properly braced in both the principal directions.
Knee bracings will be preferable to full diagonal bracing so as
not to obstruct the passage of floating debris during storm
surge.

66. main types of foundation

Slab or Raft Foundation


Used on soft soils.
Spread the weight over a wider area

67. main types of foundation

Strip Foundation



Used for areas where the soil varies.
Most common.
Supports a wall.

68. main types of foundation

Stepped Foundation


Used on sloping ground.
Is a form of strip foundation.

69. main types of foundation

Pile Foundation


deep foundations for small or large buildings.
Under reamed piles often used in expansive
clay or alluvial soils.

70. Masonry walls

71. Masonry walls

Strengthening of walls against high
wind/cyclones.

Reinforce the walls by means of reinforced
concrete bands and vertical reinforcing bars as
for earthquake resistance.

72. Wall Openings


general areas of weakness and stress
concentration, but needed essentially for light
and ventilation.
The following are recommended in respect of
openings.



Openings in load bearing walls should not be within a
distance of h/6 from inner corner for the purpose of
providing lateral support to cross walls, where ‘h’ is the
storey height upto eave level.
Openings just below roof level be avoided
Since the failure of any door or window on the windward side may lead to adverse uplift pressures under
roof, the openings should have strong holdfasts as well
as closing/locking arrangement.

73. Wall Openings

74. Glass Panes




Glass windows and doors are, of course, very
vulnerable to flying objects
Use thicker glass panes.
reduce the panel size to smaller dimensions.
Also glass panes can be strengthened by pasting
thin film or paper strips

75. CYCLONES - Do's & Dont's

Before the Cyclone season:





Check the house; secure loose tiles, carry out repair
works for doors and windows
Remove dead woods or dying trees close to the house;
anchor removable objects like lumber piles, loose tin
sheds, loose bricks, garbage cans, sign-boards etc.
which can fly in strong winds
Keep some wooden boards ready so that glass windows
can be boarded if needed
Demolish condemned buildings
Keep some dry non-perishable food always ready for
emergency use

76. CYCLONES - Do's & Dont's

When the Cyclone starts










Listen to the radio about weather warnings
Pass on the information to others. Believe in the official
information
Remember that a cyclone alert means that the danger is within 24
hours. Stay alert.
If your house is securely built on high ground take shelter in the
safer part of the house. However, if asked to evacuate do not
hesitate to leave the place.
Provide strong suitable support for outside doors.
Keep torches handy
Be sure that a window and door can be opened only on the side
opposite to the one facing the wind.
If the centre of the cyclone is passing directly over your house
there will be a lull in the wind and rain lasting for half and hour or
so. During this time do not go out; because immediately after that
very strong winds will blow from the opposite direction.
Switch off electrical mains in your house.
Remain calm

77. CYCLONES - Do's & Dont's

When Evacuation is instructed





Pack essentials for yourself and your family to last you a
few days, including medicines, special foods for babies
and children or elders.
Head for the proper shelter or evacuation points
indicated for your area.
Do not worry about your property
At the shelter follow instructions of the person in
charge.
Remain in the shelter until you have been informed to
leave

78. CYCLONES - Do's & Dont's

Post-cyclone measures




You should remain in the shelter until informed
that you can return to your home.
Strictly avoid any loose and dangling wires
from the lamp posts.
Clear debris from your premises immediately.
Report the correct loss to appropriate
authorities

79. Fire

80. Elements of fire protection

Include




use of non-combustible building materials,
use of fire-resistive building assemblies,
installation of automatic detection devices and
sprinklers,
development of improved fire fighting
techniques

81. Fire-resistive construction

A building construction in which the
structural members (including walls,
partitions, columns, floors, and roof) are
of noncombustible materials having fireendurance ratings at least equal to those
specified by the appropriate authorities

82. fire-resistive ratings




"fire resistance rating" is a legal term utilized by
model codes to regulate building construction.
The fire-resistive ratings of various materials and
constructions are established by laboratory tests
Specified in terms of hours a material or
assembly can be expected to withstand exposure
to fire.
For exterior walls, floors, and roof of masonry or
fire-resistive material with a fire-resistance rating
of at least 2 hours.

83. Fire-Resistive Assemblies
An assembly is a combination of materials
put together in a specific way that
achieves the fire resistance rating required
in the building code.
 For example, gypsum wallboard applied
to a steel stud.
 Fire-resistance ratings apply only to
assemblies in their entirety.
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85. Fireproofing of Construction Materials
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In construction, heavy wood timbers have a
relatively high fire resistance, because fire tends
to burn very slowly inward from the surface,
leaving enough sound timber in the center to
prevent collapse.
Wood framing can also be impregnated with
ammonium phosphate solution or covered with
special mastics.
To be classed as fire resistive, buildings must be
made of reinforced concrete or protected steel
that will stand considerable fire with minor
damage;
While steel retains its strength up to a very high
temperature, it fails rapidly at temperatures over
1,000°F (540°C).

86. Fireproofing of Construction Materials
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Structural steel may be protected in a number of ways. It can be
faced with brick, concrete, or tile; however, construction with
these materials usually adds too much weight to a building.
A protective layer of concrete over all surfaces of a beam or over
the steel bars in reinforced concrete has to be at least 2.5 in. (6.4
cm) thick to be effective;
hollow clay tile used to cover beams and girders has to be at least
4 in. (10 cm) thick.
most buildings use lightweight fireproofing such as gypsum,
perlite, and vermiculite mixed in plaster; one inch (2.5 cm) of
such materials will absorb an equivalent amount of heat as 2.5 in.
(6.4 cm) of concrete.
Some recent buildings circulate water inside each column,
protecting the structure against meltdown.
In urban areas, buildings must also provide protection against fire
in neighboring buildings through fireproof exterior walls-preferably
windowless, since windows are fire openings.

87. How to Build a Fire Resistant House
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Frame your home with metal studs. Metal studs
cannot combust in the same way that wood studs
can.
Install GFI (ground fault circuit interrupters) outlets
and circuit breakers.. It can, in just 1/30 of a second,
trip the internal circuit, effectively cutting off the
flow of electricity in the event of a possible short.
Use as much concrete as possible in the structure of
your home.
Use hard materials for flooring, doors and roofing.
Carpet is highly combustible.
Install safety features. Fire alarms

88. Thank You