NCERT Textbook - Safe Construction Practices - Class 10 PDF Download

 Page 1


33
Safe Construction Practices
A powerful earthquake measuring 6.6 at the Richter scale struck SOUTHEASTERN IRAN on 26th
December, 2003 at 5:26:52 AM (local time) and caused enormous loss of life, and near total
destruction of physical assets, killing 30,000 people and injured another 30,000. The health and
education infrastructure was severely damaged and over 85% houses collapsed.
A super cyclone slammed the state of Orissa on October 29, 1999
with a wind speed of 270-300 kmph, accompanied by torrential rains
ranging from 400 mm to 867 mm continuously for three days. Over 7 lakh
buildings were completely damaged and 13 lakh buildings were partially
damaged.
In Class VIII and Class IX textbooks we have studied about causes, effects and mitigation strategies of
natural and manmade hazards. In this chapter we will discuss about some of the important factors to
be considered to construct a building resistant to four natural hazards: earthquake, landslide, cyclone
and flood. The cost of natural disasters to lives, property, livelihood and infrastructure have skyrocketed
in last few decades, as the world’s population has grown and people have started residing in areas that
are vulnerable to natural hazards. The most successful way to mitigate loss of life and property, is to
construct buildings that are disaster resistant. This chapter outlines some of the structural safety
measures that need to be taken up for constructing desaster resistant buildings.
Safe Construction Practices
5.
Page 2


33
Safe Construction Practices
A powerful earthquake measuring 6.6 at the Richter scale struck SOUTHEASTERN IRAN on 26th
December, 2003 at 5:26:52 AM (local time) and caused enormous loss of life, and near total
destruction of physical assets, killing 30,000 people and injured another 30,000. The health and
education infrastructure was severely damaged and over 85% houses collapsed.
A super cyclone slammed the state of Orissa on October 29, 1999
with a wind speed of 270-300 kmph, accompanied by torrential rains
ranging from 400 mm to 867 mm continuously for three days. Over 7 lakh
buildings were completely damaged and 13 lakh buildings were partially
damaged.
In Class VIII and Class IX textbooks we have studied about causes, effects and mitigation strategies of
natural and manmade hazards. In this chapter we will discuss about some of the important factors to
be considered to construct a building resistant to four natural hazards: earthquake, landslide, cyclone
and flood. The cost of natural disasters to lives, property, livelihood and infrastructure have skyrocketed
in last few decades, as the world’s population has grown and people have started residing in areas that
are vulnerable to natural hazards. The most successful way to mitigate loss of life and property, is to
construct buildings that are disaster resistant. This chapter outlines some of the structural safety
measures that need to be taken up for constructing desaster resistant buildings.
Safe Construction Practices
5.
34
Earthquakes
Earthquakes
On December 23, 1972, a series of earthquakes shook the
Central American nation of Nicaragua. The largest
earthquake registered 6.2 on the Richter scale. The
earthquake’s epicenter was located precisely at the capital
city of Managua. The earthquake resulted in the destruction
of the heavily populated central zone and damage to a total
area of about 27 square kilometers (10 square miles).
Subsequent fires blazed throughout the city, compounding
the damages. In the wake of the disaster, at least 8,000 of
Managua’s total population of 430,000 had died, 20,000 were
injured, over 260,000 had fled the city, 50 percent of the
employed were jobless, and 70 percent were left temporarily
homeless. At least 10 percent of the nation’s industrial
capacity, 50 percent of commercial property, and 70 percent
of government facilities were rendered inoperative. Overall,
the damage estimated in US dollars was $845 million.
GROUND MOVEMENTS
The ground movements caused by earthquakes can have
several types of damaging effects. Some of the major
effects are:
1. Ground shaking, i.e. back-and-forth motion of the
ground, caused by the passing vibratory waves through
the ground.
2. Soil failures, such as liquefaction and landslides, caused by shaking;
3. Surface fault ruptures, such as cracks, vertical shifts,  etc.
4. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that can cause major
damage to shoreline areas.
EFFECT ON BUILDINGS
As the vibrations and waves continue to move through the
earth, buildings on the earth’s surface are set in motion.
Each building responds differently, depending on its
construction. When the waves strike, the earth begins to
move backward and forward along the same line. The
lower part of a building on the earth’s surface
immediately moves with the earth. The upper
portion, however, initially remains at rest; thus
the building is stretched out of shape.
Gradually the upper portion tries to
catch up with the bottom, but as
it does so, the earth moves in the other direction, causing a “whiplash”
effect. The vibration can cause structural failure in the building itself,
Shaking of short and tall building due to
ground acceleration
The building has tilted as a result of column
failure & has partly damaged the nearby building
(Taiwan 1999). (By Bachmann H., Sesimic
Conceptual Design of Buildings)
House
Page 3


33
Safe Construction Practices
A powerful earthquake measuring 6.6 at the Richter scale struck SOUTHEASTERN IRAN on 26th
December, 2003 at 5:26:52 AM (local time) and caused enormous loss of life, and near total
destruction of physical assets, killing 30,000 people and injured another 30,000. The health and
education infrastructure was severely damaged and over 85% houses collapsed.
A super cyclone slammed the state of Orissa on October 29, 1999
with a wind speed of 270-300 kmph, accompanied by torrential rains
ranging from 400 mm to 867 mm continuously for three days. Over 7 lakh
buildings were completely damaged and 13 lakh buildings were partially
damaged.
In Class VIII and Class IX textbooks we have studied about causes, effects and mitigation strategies of
natural and manmade hazards. In this chapter we will discuss about some of the important factors to
be considered to construct a building resistant to four natural hazards: earthquake, landslide, cyclone
and flood. The cost of natural disasters to lives, property, livelihood and infrastructure have skyrocketed
in last few decades, as the world’s population has grown and people have started residing in areas that
are vulnerable to natural hazards. The most successful way to mitigate loss of life and property, is to
construct buildings that are disaster resistant. This chapter outlines some of the structural safety
measures that need to be taken up for constructing desaster resistant buildings.
Safe Construction Practices
5.
34
Earthquakes
Earthquakes
On December 23, 1972, a series of earthquakes shook the
Central American nation of Nicaragua. The largest
earthquake registered 6.2 on the Richter scale. The
earthquake’s epicenter was located precisely at the capital
city of Managua. The earthquake resulted in the destruction
of the heavily populated central zone and damage to a total
area of about 27 square kilometers (10 square miles).
Subsequent fires blazed throughout the city, compounding
the damages. In the wake of the disaster, at least 8,000 of
Managua’s total population of 430,000 had died, 20,000 were
injured, over 260,000 had fled the city, 50 percent of the
employed were jobless, and 70 percent were left temporarily
homeless. At least 10 percent of the nation’s industrial
capacity, 50 percent of commercial property, and 70 percent
of government facilities were rendered inoperative. Overall,
the damage estimated in US dollars was $845 million.
GROUND MOVEMENTS
The ground movements caused by earthquakes can have
several types of damaging effects. Some of the major
effects are:
1. Ground shaking, i.e. back-and-forth motion of the
ground, caused by the passing vibratory waves through
the ground.
2. Soil failures, such as liquefaction and landslides, caused by shaking;
3. Surface fault ruptures, such as cracks, vertical shifts,  etc.
4. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that can cause major
damage to shoreline areas.
EFFECT ON BUILDINGS
As the vibrations and waves continue to move through the
earth, buildings on the earth’s surface are set in motion.
Each building responds differently, depending on its
construction. When the waves strike, the earth begins to
move backward and forward along the same line. The
lower part of a building on the earth’s surface
immediately moves with the earth. The upper
portion, however, initially remains at rest; thus
the building is stretched out of shape.
Gradually the upper portion tries to
catch up with the bottom, but as
it does so, the earth moves in the other direction, causing a “whiplash”
effect. The vibration can cause structural failure in the building itself,
Shaking of short and tall building due to
ground acceleration
The building has tilted as a result of column
failure & has partly damaged the nearby building
(Taiwan 1999). (By Bachmann H., Sesimic
Conceptual Design of Buildings)
House
35
Tilting of building due to liquefaction (Adapazari, Turkey 1999)
By Bachmann H., Sesimic Conceptual Design of Buildings
or to an adjacent building having different response characteristics.
Taller buildings also tend to shake longer than short buildings, which can make them relatively more
susceptible to damage.
PROTECTION MEASURES
The primary objective of earthquake resistant design is to prevent collapse during earthquakes thus
minimising the risk of death or injury to people in or around the buildings. There are certain features
which if taken into consideration at the stage of architectural planning and structural design of buildings,
their performance during earthquakes will be appreciably improved. Some of these are stated below :
Building configuration
? The building should have a simple rectangular plan.
? Long walls should be supported by Reinforced Concrete columns
as shown on the right side.
? Large buildings having plans with shapes like T , L, U and X should
preferably be separated into rectangular blocks by providing gaps
in between.
Foundation
Buildings which are structurally strong to withstand earthquakes
sometimes fail due to inadequate foundation
design. Tilting, cracking and failure of structure
may result from soil liquefaction. Soil liquefaction
refers to transformation of soil from a solid state
to a liquid state as a consequence of increased
pressure.
Use of seperation gaps
Depending on the type of soil conditions the depth of the foundation has to be decided.
Page 4


33
Safe Construction Practices
A powerful earthquake measuring 6.6 at the Richter scale struck SOUTHEASTERN IRAN on 26th
December, 2003 at 5:26:52 AM (local time) and caused enormous loss of life, and near total
destruction of physical assets, killing 30,000 people and injured another 30,000. The health and
education infrastructure was severely damaged and over 85% houses collapsed.
A super cyclone slammed the state of Orissa on October 29, 1999
with a wind speed of 270-300 kmph, accompanied by torrential rains
ranging from 400 mm to 867 mm continuously for three days. Over 7 lakh
buildings were completely damaged and 13 lakh buildings were partially
damaged.
In Class VIII and Class IX textbooks we have studied about causes, effects and mitigation strategies of
natural and manmade hazards. In this chapter we will discuss about some of the important factors to
be considered to construct a building resistant to four natural hazards: earthquake, landslide, cyclone
and flood. The cost of natural disasters to lives, property, livelihood and infrastructure have skyrocketed
in last few decades, as the world’s population has grown and people have started residing in areas that
are vulnerable to natural hazards. The most successful way to mitigate loss of life and property, is to
construct buildings that are disaster resistant. This chapter outlines some of the structural safety
measures that need to be taken up for constructing desaster resistant buildings.
Safe Construction Practices
5.
34
Earthquakes
Earthquakes
On December 23, 1972, a series of earthquakes shook the
Central American nation of Nicaragua. The largest
earthquake registered 6.2 on the Richter scale. The
earthquake’s epicenter was located precisely at the capital
city of Managua. The earthquake resulted in the destruction
of the heavily populated central zone and damage to a total
area of about 27 square kilometers (10 square miles).
Subsequent fires blazed throughout the city, compounding
the damages. In the wake of the disaster, at least 8,000 of
Managua’s total population of 430,000 had died, 20,000 were
injured, over 260,000 had fled the city, 50 percent of the
employed were jobless, and 70 percent were left temporarily
homeless. At least 10 percent of the nation’s industrial
capacity, 50 percent of commercial property, and 70 percent
of government facilities were rendered inoperative. Overall,
the damage estimated in US dollars was $845 million.
GROUND MOVEMENTS
The ground movements caused by earthquakes can have
several types of damaging effects. Some of the major
effects are:
1. Ground shaking, i.e. back-and-forth motion of the
ground, caused by the passing vibratory waves through
the ground.
2. Soil failures, such as liquefaction and landslides, caused by shaking;
3. Surface fault ruptures, such as cracks, vertical shifts,  etc.
4. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that can cause major
damage to shoreline areas.
EFFECT ON BUILDINGS
As the vibrations and waves continue to move through the
earth, buildings on the earth’s surface are set in motion.
Each building responds differently, depending on its
construction. When the waves strike, the earth begins to
move backward and forward along the same line. The
lower part of a building on the earth’s surface
immediately moves with the earth. The upper
portion, however, initially remains at rest; thus
the building is stretched out of shape.
Gradually the upper portion tries to
catch up with the bottom, but as
it does so, the earth moves in the other direction, causing a “whiplash”
effect. The vibration can cause structural failure in the building itself,
Shaking of short and tall building due to
ground acceleration
The building has tilted as a result of column
failure & has partly damaged the nearby building
(Taiwan 1999). (By Bachmann H., Sesimic
Conceptual Design of Buildings)
House
35
Tilting of building due to liquefaction (Adapazari, Turkey 1999)
By Bachmann H., Sesimic Conceptual Design of Buildings
or to an adjacent building having different response characteristics.
Taller buildings also tend to shake longer than short buildings, which can make them relatively more
susceptible to damage.
PROTECTION MEASURES
The primary objective of earthquake resistant design is to prevent collapse during earthquakes thus
minimising the risk of death or injury to people in or around the buildings. There are certain features
which if taken into consideration at the stage of architectural planning and structural design of buildings,
their performance during earthquakes will be appreciably improved. Some of these are stated below :
Building configuration
? The building should have a simple rectangular plan.
? Long walls should be supported by Reinforced Concrete columns
as shown on the right side.
? Large buildings having plans with shapes like T , L, U and X should
preferably be separated into rectangular blocks by providing gaps
in between.
Foundation
Buildings which are structurally strong to withstand earthquakes
sometimes fail due to inadequate foundation
design. Tilting, cracking and failure of structure
may result from soil liquefaction. Soil liquefaction
refers to transformation of soil from a solid state
to a liquid state as a consequence of increased
pressure.
Use of seperation gaps
Depending on the type of soil conditions the depth of the foundation has to be decided.
36
Control on openings in walls
Door and window openings in walls should preferably be small and more
centrally located. T oo many or large openings will make the wall vulnerable
to collapse during earthquakes. The location of openings should not be
too close to the edge of the wall.
RIGHT: Damage to columns due
to long openings & windows
located at the edge of the
column (Northridge, California
1994)
LEFT: Long window opening
caused additional shear stress
& column failure (Izmit, Turkey
1999) By Bachmann H., Sesimic
Conceptual Design of Buildings
Legend
1 Lintel band
2 Eave level
(Roof) band
3 Gable band
4 Floor band
5 Plinth band
6 Vertical band
7 Rafter
8 Holding Down  bolt
9 Door
10 window
Overall arrangement of reinforcing
in masonry double storey building
having pitched roof
Reinforced concrete bands in masonry
buildings
For integrating the walls of an enclosure to
perform together like a rigid box reinforced
concrete bands are provided which run
continuously on all external and internal walls
including fixed partition walls. One or more of
the following bands may be necessary in a
building. Plinth band, lintel band, roof band, and
gable band are names used for the band
depending on the level of the building where the
band is provided.
Vertical reinforcement
Vertical reinforcement should be provided at corners and junction of
walls. It shall be passing through the lintel bands and floor slabs or
floor level bands in all storeys.
Earthquake doesn’t kill people. It is the badly designed buildings
that kill the people. So to prevent an earthquake hazard from
becoming a disaster our buildings should be properly designed
incorporating the earthquake resistant design features
into it.
Page 5


33
Safe Construction Practices
A powerful earthquake measuring 6.6 at the Richter scale struck SOUTHEASTERN IRAN on 26th
December, 2003 at 5:26:52 AM (local time) and caused enormous loss of life, and near total
destruction of physical assets, killing 30,000 people and injured another 30,000. The health and
education infrastructure was severely damaged and over 85% houses collapsed.
A super cyclone slammed the state of Orissa on October 29, 1999
with a wind speed of 270-300 kmph, accompanied by torrential rains
ranging from 400 mm to 867 mm continuously for three days. Over 7 lakh
buildings were completely damaged and 13 lakh buildings were partially
damaged.
In Class VIII and Class IX textbooks we have studied about causes, effects and mitigation strategies of
natural and manmade hazards. In this chapter we will discuss about some of the important factors to
be considered to construct a building resistant to four natural hazards: earthquake, landslide, cyclone
and flood. The cost of natural disasters to lives, property, livelihood and infrastructure have skyrocketed
in last few decades, as the world’s population has grown and people have started residing in areas that
are vulnerable to natural hazards. The most successful way to mitigate loss of life and property, is to
construct buildings that are disaster resistant. This chapter outlines some of the structural safety
measures that need to be taken up for constructing desaster resistant buildings.
Safe Construction Practices
5.
34
Earthquakes
Earthquakes
On December 23, 1972, a series of earthquakes shook the
Central American nation of Nicaragua. The largest
earthquake registered 6.2 on the Richter scale. The
earthquake’s epicenter was located precisely at the capital
city of Managua. The earthquake resulted in the destruction
of the heavily populated central zone and damage to a total
area of about 27 square kilometers (10 square miles).
Subsequent fires blazed throughout the city, compounding
the damages. In the wake of the disaster, at least 8,000 of
Managua’s total population of 430,000 had died, 20,000 were
injured, over 260,000 had fled the city, 50 percent of the
employed were jobless, and 70 percent were left temporarily
homeless. At least 10 percent of the nation’s industrial
capacity, 50 percent of commercial property, and 70 percent
of government facilities were rendered inoperative. Overall,
the damage estimated in US dollars was $845 million.
GROUND MOVEMENTS
The ground movements caused by earthquakes can have
several types of damaging effects. Some of the major
effects are:
1. Ground shaking, i.e. back-and-forth motion of the
ground, caused by the passing vibratory waves through
the ground.
2. Soil failures, such as liquefaction and landslides, caused by shaking;
3. Surface fault ruptures, such as cracks, vertical shifts,  etc.
4. Tidal waves (tsunamis), i.e. large waves on the surface of bodies of water that can cause major
damage to shoreline areas.
EFFECT ON BUILDINGS
As the vibrations and waves continue to move through the
earth, buildings on the earth’s surface are set in motion.
Each building responds differently, depending on its
construction. When the waves strike, the earth begins to
move backward and forward along the same line. The
lower part of a building on the earth’s surface
immediately moves with the earth. The upper
portion, however, initially remains at rest; thus
the building is stretched out of shape.
Gradually the upper portion tries to
catch up with the bottom, but as
it does so, the earth moves in the other direction, causing a “whiplash”
effect. The vibration can cause structural failure in the building itself,
Shaking of short and tall building due to
ground acceleration
The building has tilted as a result of column
failure & has partly damaged the nearby building
(Taiwan 1999). (By Bachmann H., Sesimic
Conceptual Design of Buildings)
House
35
Tilting of building due to liquefaction (Adapazari, Turkey 1999)
By Bachmann H., Sesimic Conceptual Design of Buildings
or to an adjacent building having different response characteristics.
Taller buildings also tend to shake longer than short buildings, which can make them relatively more
susceptible to damage.
PROTECTION MEASURES
The primary objective of earthquake resistant design is to prevent collapse during earthquakes thus
minimising the risk of death or injury to people in or around the buildings. There are certain features
which if taken into consideration at the stage of architectural planning and structural design of buildings,
their performance during earthquakes will be appreciably improved. Some of these are stated below :
Building configuration
? The building should have a simple rectangular plan.
? Long walls should be supported by Reinforced Concrete columns
as shown on the right side.
? Large buildings having plans with shapes like T , L, U and X should
preferably be separated into rectangular blocks by providing gaps
in between.
Foundation
Buildings which are structurally strong to withstand earthquakes
sometimes fail due to inadequate foundation
design. Tilting, cracking and failure of structure
may result from soil liquefaction. Soil liquefaction
refers to transformation of soil from a solid state
to a liquid state as a consequence of increased
pressure.
Use of seperation gaps
Depending on the type of soil conditions the depth of the foundation has to be decided.
36
Control on openings in walls
Door and window openings in walls should preferably be small and more
centrally located. T oo many or large openings will make the wall vulnerable
to collapse during earthquakes. The location of openings should not be
too close to the edge of the wall.
RIGHT: Damage to columns due
to long openings & windows
located at the edge of the
column (Northridge, California
1994)
LEFT: Long window opening
caused additional shear stress
& column failure (Izmit, Turkey
1999) By Bachmann H., Sesimic
Conceptual Design of Buildings
Legend
1 Lintel band
2 Eave level
(Roof) band
3 Gable band
4 Floor band
5 Plinth band
6 Vertical band
7 Rafter
8 Holding Down  bolt
9 Door
10 window
Overall arrangement of reinforcing
in masonry double storey building
having pitched roof
Reinforced concrete bands in masonry
buildings
For integrating the walls of an enclosure to
perform together like a rigid box reinforced
concrete bands are provided which run
continuously on all external and internal walls
including fixed partition walls. One or more of
the following bands may be necessary in a
building. Plinth band, lintel band, roof band, and
gable band are names used for the band
depending on the level of the building where the
band is provided.
Vertical reinforcement
Vertical reinforcement should be provided at corners and junction of
walls. It shall be passing through the lintel bands and floor slabs or
floor level bands in all storeys.
Earthquake doesn’t kill people. It is the badly designed buildings
that kill the people. So to prevent an earthquake hazard from
becoming a disaster our buildings should be properly designed
incorporating the earthquake resistant design features
into it.
37
Landslides
Normal life disrupted in the hilly terrains of
Uttaranchal
Landslides
Landslides are among the major natural disasters or calamities in the world. In hilly terrains of India,
including Himalayan mountains landslides have been a major and widely spread natural disasters that
strike life and property almost perennially and occupy a position of major concern. These landslides,
year after year, bring about untold misery to human settlements apart from causing devastating damages
to transportation and communication network.
Landslides, debris fall, debris slide, debris flow, rock toppling etc. cause destruction of slope and ground
surface, initiating the change of uncontrolled erosion in the mountain terrains.
On 21st August, 2002, heavy monsoon in eastern Nepal triggered landslides and flashfloods which killed
419 people and injuring 105 people. More than 53,152 families were affected and about 19,485 houses
were destroyed. A total of 47 districts were affected.
FACTORS THAT CAUSE LANDSLIDES
Landslides occur because of the interplay of
several factors.
Natural factors
? Intensity of rainfall
? Steep slopes
? Stiffness of slopes
? Highly weathered rock layers
? Soil layers formed under gravity
? Seismic activity
? Poor drainage
Man made factors
? Deforestation leading to soil erosion
? Non-engineered excavation
? Mining and quarrying
? Non-engineered construction
? Land use pattern
MOST VULNERABLE HOMES
Vulnerable houses are those which are situated on:
? Existing landslides area.
? Steep natural slopes.
? Areas in or at the mouths of drainages (such
as canyons).
? Houses constructed near foothills.
Large volume of sediments, rudiments of
buildings and other debris were transported
by debris flows and high flood water