non-engineered buildings

Design and Management of Structures in Earthquake Zones – CIVE 5913M

Report on “Non-Engineered Buildings”

Course Work 2 – Student ID: 2004 40013 1

ABSTRACT:

Nature calamities are unavoidable and unpredictable. It may happen at any time anywhere in

the world. They claim millions of life and money, if suitable resistant measures are not

followed. Earthquake is one such calamity which costs unaccountable damage to men and

man-made structures. Developed countries which are prone to earthquake are very often

investing huge amount of money in building structures which are capable to resist earthquake

effects. There by they reduce the amount of damage caused to public and to the structures

built by or built for the public. Economically undeveloped countries which are prone to

earthquake are still struggling and losing their wealth very often to the hands of earthquake.

Due to lack in economy and engineering, most people of these countries are at risk from the

collapse of their own homes. These are ‘non-engineered’ buildings. Hence to protect the

population, there is an urgent need to increase the quality of the domestic construction to

reduce their vulnerability to earthquake action. In terms of guiding those reports are prepared

by many voluntary organisations on how to build low cost buildings in earthquake areas. This

is one such report which discusses the ways to built buildings in an earthquake area and

advantages and disadvantages of the materials used for construction. Photographs and

sketches are included in this report to provide clear view about earthquake effects on

buildings and on improvement measures. A case study on reducing vulnerability on buildings

in earthquake prone country (India) is done in order to provide clear understanding on this

topic.




1 INTRODUCTION:

Earthquake is a hazardous calamity which causes damage to life and money. Buildings which

are engineered to this effect stands during an earthquake and those not engineered fails.

Existing buildings which are not engineered are to be improved in order to resist the earthquake

effects. Strength of earthquake depends on the intensity, frequency, time duration and soil

conditions.

Damages on buildings also depend on these criteria along with the quality of construction,

strength and durability. From the history of the earthquakes it can be understood that many

people were killed or badly injured because of poorly constructed buildings. In earthquake

prone undeveloped countries buildings are erected without proper engineering advice with

usage of poor quality materials, construction and workmanship. More often buildings

constructed with traditional materials like stones and bricks are suffered the most. In fact non-

engineered buildings are built mostly with load bearing masonry wall, stud wall, piers in

masonry and columns in RC, steel or wood [3].

In view of the fact that in seismic zones of the world more than 90 percent of the population is

still living and working in non-engineered buildings [1]. As earthquake forces are horizontal in

nature, vertical load carrying structural elements are forced to carry horizontal load and the

shear associated with it. If the structural elements are not designed to carry this, the structure

fails. Associated causes of earthquake like ground vibration and failure, tsunami and fire are

also major disaster causing agents. From analysis of buildings in earthquake areas, it is clear

that most of the building fail due to considering strong beams and weak columns, soft storeys

and lack of transverse reinforcement [4].

As per the 1991 census of India, the country has nearly 195.0 million non-engineered dwelling

units [3]. On 26th January 2001, an earthquake rocked Gujarat, India and claimed millions of

lives. Most of the collapsed buildings are identified as non-engineered buildings. This is an

example event to point the need of earthquake resistant construction of non-engineered

buildings. Recent earthquakes in Kobe-Japan and Anatolia-Turkey triggered the importance of

skill in constructing non-engineered buildings. Countries which are extremely prone to

earthquake damages require a suitable report which will be useful to people involved in

construction of new houses or repair and strengthening of existing buildings. In this report, the

construction of earthquake safe non-engineered buildings plays a major role.




2 BUILDING IN EARTHQUAKE ZONE:

Consider a typical two storey house in earthquake prone area which is subjected to seismic

forces. The building is non-engineered one and constructed using locally available material.

The building is designed and constructed by a local artisan over a soft soil stratum without any

engineering knowledge. The materials used are locally available low quality fire burnt bricks,

reinforced concrete for roof slab, graded cement, river sand, wooden joineries and wooden

truss for sloped tile roof. Due to budget limitation form the owner, the builder decided to add

sloped wooden roof with burnt roof tiles as cover to second storey instead of reinforced

concrete slab. As this building is constructed using traditional materials, its response to seismic

forces will be large and may damage during an earthquake.

Figure 1: Typical two - storey house

2.1 Construction methods:

The walls were supported by masonry columns at the edges and at the centre. The RCC roof

slab of first storey is made to rest on walls and partially on masonry columns. The masonry

columns are continued from first storey to second storey to support wooden roof truss and roof

tiles. Walls at first storey level are urged to carry the weight of first storey roof, walls at second

storey level, partial weight from roof truss and tiles. Thus the walls act as a load-bearing one.

Roof slab is placed above the wall and on column and it is not effectively tied to it. In both the

storeys floor to roof distance is uniform. The walls are unreinforced with larger length-to-width

ratio on one side and other as simply supported masonry wall. In considering foundation for the

house, columns are provided with isolated footings. Individual column footings are not tied to

each other using plinth beam. Staircase to second storey is provided outside the building which




made of reinforced concrete and supported to lintel and column. Sufficient number of window

openings is provided. Lintel beams are not continued through the building they are provided

only above window and door openings.

Figure 2: Building plan of two-storey house

2.2 Forces acting on the building:

2.2.1 Inertia forces:

Basically seismic forces are movements which act randomly in all directions and unpredictable.

Due to self weight of the building resists the seismic forces acting on it. This resistant of the

building due to its self-weight is called as inertia force. Mostly buildings collapse due to inertia

forces only. During seismic load the building moves abruptly and inertia forces are created

throughout the building and in its contents [1]. If the weight of the building is more the inertia

force will more and vice versa.

As the building is constructed using traditional materials like bricks, RCC for roof slabs; the

weight of the building is more. For an earthquake prone area, the buildings should be built less

weight, such that the inertia forces will be less.

2.2.2 Seismic forces on whole structure:

As seismic forces are abrupt, the vertical vibrations created by that will impose an additional

vertical load effect to the walls and columns. As the walls and columns are not designed to it

failure will occur. In addition to that they have to carry horizontal bending and shearing stress.

From the construction methods of the building it is observed that the link between walls and

columns is poor. No reinforcement is provided in that link. Connection between roof slab with

wall and column is not well detailed.




Figure 3: Behaviour of two-storey house to seismic force

Seismic force acts horizontally to the building on a whole, due to inertia the building manages

itself to be in position. As deflection increases with height, second storey responds more to

seismic forces and will start to slide from its original position. Due to ineffective column this

may happen. The columns are made from masonry work without reinforcement and in this case

it had failed due to shearing. Due to improper linkage between the members of the building this

type of failure occurred. The connection between the walls and columns are not well detailed to

resist the seismic forces acting on it.

2.3 Response of first storey:

When considering first storey alone, the earthquake force is acting in plane of the wall B and

opposite to wall A. As the adhesion between the slab and wall is poor, the inertia force of the

slab will not be transferred to the walls A and B. Due to this the slab will tend to slide from its

initial position.

Figure 4: Response of first storey

Wall A is not designed to carry load in X-direction, this results in occurrence of crack near the

connection between the columns and may fail due to bending action. At the same time wall B




will act as a shear wall withstanding the force from the roof and its own inertia force. The plate

action of wall A has to be restrained by the roof at the top and by column supporting it. The

seismic forces are amplified in this case due to ineffective joint connection between the

members. In real conditions, the building on whole should act as a box; transferring forces

effectively. The diaphragm action of the roof slab is not adequate to transfer its inertia force to

the side walls [1]. If the roof slab is linked well to the walls, wall B will carry most of the inertia

force from the roof than wall A; as because wall B has more stiffness in that direction than wall

A. The relative displacement of wall will bring down the roof slab.

2.4 Response of second storey:

The masonry columns are continued from first storey to second storey. As no reinforcements

are provided in the columns, they will shear and fail. If reinforcement is provided, failure due

to shear and bending can be prevented.

Figure 5: Response of second storey

Same as first storey the seismic forces are acting in X-direction. As this storey deflect

more than first storey, they develop more crack due to shaking effects. The inertia force created

by the roof will only go to the vertical elements in which they are supported. On failure of

columns the roof will collapse. The integrity of roof is more important for earthquake

resistance. In this case the wooden truss is made to simply rest on the columns, walls and will

offer resistance to motion through friction only [1].

The walls B are gabled to receive the purlins of the end bays. During seismic force along X-

axis, the inertia force from the purlins will transmitted to trusses and from trusses to wall A.

Wall A which is supported to columns will bend on deflection and may fail, which results in

sliding of roof truss in one direction and fail. As the truss is made to support on wall A, on

failure the truss will collapse. By adding suitable horizontal bracing in the truss, it can be made

to transmit the force horizontally to wall B.




2.5 Seismic forces on individual parts:

The ability of the structure to withstand seismic force depends on the characteristics

of individual members.

2.5.1 Column:

Columns in this structure are assumed to be made of masonry without any

reinforcements in it. The main purpose of this column is to support the walls and to

carry partial loads from first storey roof slab and roof truss. As there is no cross

reinforcements in the column, it will fail easily due to bending and shear. These

columns are the one which is intended to hold the building as a single element. To

avoid failure columns are to be tied with each other particularly to the footing,

through which the load is transmitted to the ground. The roof and wall connection to

the columns are to be well detailed in order to perform like a box.

2.5.2 Roof slab and roof truss:

The roof slab is made of RCC and it is placed on the walls to transmit the inertia force

created during an earthquake. For this transmission the slab has to be joined

effectively to the walls and to columns. The diaphragm effect of the slab in essential

for it to behave as an active resistant to seismic force. The roof truss has to efficiently

fix at edges to the columns and supported to the wall. The wall supporting the truss

has to be designed to carry the inertia forces from the truss created during earthquake.

2.5.3 Walls:

As walls are designed to act as load bearing one, they have to be effectively fixed to

the supports mainly columns at sides. The earthquake is assumed to be in x-direction,

in which wall A is weak to carry that seismic force than wall B which acts as shear

wall. This is due that the seismic forces are acting in plane to wall B. From fig: 3,

performance of the wall during an earthquake in x-direction can be analysed. The

perpendicular seismic force acting on wall A makes it to bend and even to overturn, if

the top of the wall is not fixed to the roof effectively. In this the joints at the edges of

the wall with the column will fail. Apart from its own inertia force, the walls are

subjected from vertical loads from the roof slab and weight of second storey.




2.5.4 Footing:

Though the site is located on soft soil, plinth band is not used to tie all footings. This

is because the column has no reinforcement in it and connection with plinth is not

possible. The footing is assumed to be isolated, so occurrence of differential

settlement may possible. Due to bending action of the column the footing may fail at

the junction. The amount of lateral force acting during seismic force will be

enormous. To avoid failure footings are advised to be continuous.

3 LOAD PATH TO THE GROUND:

Basically seismic load is a combination of both horizontal and vertical load. The loads

acting on the structure has to be transferred to the ground for dissipation. Efficient

load path depends on durable joints between the members. Flow chart below explains

the load path of the building discussed earlier.

Figure 6: Load path of the building

Abrupt forces acting on the structure is transferred from all parts of the members to

the nearest load path and reaches the ground. Load from roof truss reaches the ground

by the help of columns and walls at second floor level supporting that. Similarly load

from first storey roof reaches the ground by columns and walls at first storey level. In

this same fashion, load acting at different elements of the structure will take their

nearest load path and reach the ground to nullify the damage effect to be caused to




them. For efficient transmission of loads the members and the joints should be durable

and strong enough to carry them without any damage to the structure.

4 FORMS OF CONSTRUCTION AND MATERIALS:

Materials, methods and shapes used for construction will vary from place to place.

These many times represent culture and tradition of individuals. In certain places

economy places a major role in selection of these. Countries prone to earthquake

effects often have dwelling spaces built using traditional construction materials,

methods and shapes. For discussion, buildings are categorised as per their materials,

methods of construction and shapes used.

4.1 Materials used for construction:

Normally non-engineered buildings are constructed using Fire burnt masonry bricks,

stone, wood and earth. These are easily available material and cost less for

constructing a building. Depending on availability of material construction of

buildings will vary.

4.1.1 Fire burnt masonry bricks:

Bricks are one of the material which as acceptable compressive strength and

unacceptable tensile strength. Its strength can be upgraded when combined with

reinforcement steel. Load carrying capacity of bricks in building is increased if bond

with mortar is good. Normally bricks are used to built buildings, where the load to be

carried is more. Bricks are used at places where clay fields are more. As a material it

resists seismic load applied on it, if proper construction method is used.

4.1.2 Rubble stone:

Buildings built of rubble stone are more in rural areas. As this is easily available

material, many are intended to use to this material. Same as brick it has very good

compressive strength. With introduction of mortar and reinforcement, the strength and

load carrying capacity can be increased. Exhibits poor strength when used with mud

mortar [1]. When considering the height of the building, it is advisable to use

reinforcement with rubble stone. Well dressed polished and unpolished stones are

available in the market. Buildings destroyed at Gujarat, India during earthquake in the

year 2001 are more of Rubble stone or cut stone type [2]. This material suffered




extensive damage and complete collapse during earthquakes. As these types of

buildings weigh more, the inertia forces created during seismic reaction will be more

and easily prone to damage.

4.1.3 Wood:

Good damping material. Buildings built with wood experienced less damage when

comparing to buildings built with other materials. Depending upon quality price of

material varies. More often used in hilly areas. In order to protect environment,

cutting of trees is banned in many countries. Decrease in forest area due to population

increase reduced wood usage in construction. Wooden buildings are constructed in

areas where availability of the material is more or in unavoidable situations only [1].

Wooden frames used in buildings may fail due to impose of high lateral load to the

frame from heavy cladding. Easily catches fire and may cause mass damage.

4.1.4 Earth:

Buildings using earth are informally constructed in many parts of the earthquake

prone countries. They often use wooden sticks as reinforcement. Due to minimal

costs, good acoustics and thermal insulation effects it is widely used in rural parts.

The performance of this material under earthquake and water is very poor [1].

Currently in India there are about 74.7 million earthen dwelling units which constitute

38% of total dwelling units [3]. These are the ones which causes the greatest loss of

life and damage during seismic events.

4.2 Methods used for construction:

Though the material is tough against seismic load, the method followed in

constructing that may lead to failure of material. Many time materials will not fail by

crushing, it will fail due to improper bonding and connection details. Majority of non

– engineered buildings are constructed under two main categories [5].

a) Load bearing masonry

b) Reinforced concrete frames




4.2.1 Load bearing masonry:

In this type of construction the entire load of the slab is concentrated on supporting

walls, which are reinforced or many times unreinforced. The supporting walls are to

carry the inertia forces from the slab. On absence on this, the structure collapses. Most

of these buildings use masonry units like burnt bricks, concrete blocks, rubble stone

and rough dressed stones. Even sun dried clay bricks are used in this type of

construction. The units are bonded with each other using available mortar variety.

Roof structure often consists of tiles laid on timber planks supported by wooden

purlins and rafter. If the number of storey exceeds normally reinforced concrete slabs

are used [5].

This type of construction is very economical and suitable for single storey buildings

with low load carrying capacity. For efficient performance, the roof has to tie to the

walls supporting it. Do well, if the sides of the walls are short. Non reinforcement

usage, usage of heavy stone blocks and roofs will make the building to vulnerable to

earthquake. Masonry units with mud mortar perform worst in this type of

construction. This type highly depends on tie between roof and walls, size and

spacing of openings.

4.2.2 Reinforced concrete frames:

In this type of construction the loads are designed to carry by members assigned in the

structure, preferably for buildings taller than three storeys. Usually the masonry infill

is built using stone block or clay brick. Frames are designed such that the inertia

forces created by the roof are carried through a load path and get dissipated at ground

level. This method is efficient for earthquake construction, if properly designed.

Poor detailing of open first storey combined with poor quality of construction will

make the frame to fail. Beam-column connections are to be designed to carry torsion

and lateral forces acting on them. Continuity of columns and beams are a major issue

in this type of construction.

4.3 Shapes of construction:

Shape and geometry of structure decides the structural response during an earthquake.

Structures with simple shape and geometry perform well during an earthquake. It is

always preferred to have simple shapes during construction such that all the members




and joints associated can be well designed. Symmetrical plans with suitable size

openings make the structure to behave as whole; where as unsymmetrical plans leads

to torsion and extreme corners are subjected to very large earthquake forces [6].

Structure should avoid projections in it. “For long narrow rectangular blocks, the

length of a block is restricted to three times its width” [1]. Structure should be a simple

one with out ornamental effects on it. On requirement it should be effectively tied to

the structure. Separate enclosed rooms perform well than the rooms without

intermediate wall.

Though symmetrical plans are suitable for earthquake construction, due to their

simple appearance they are often neglected. On using unsymmetrical plan, separation

joints have to be provided such that the torsion and corners effects are neglected.

From figure: 9, it is clear that due to inertia force, the failures at the junction; mostly

with rotation type of failure. The same plan when built with few separation joints

make the structure to work against seismic force and inertia force in it.




Symmetrical buildings are more advantageous than an unsymmetrical building. They

can easily dissipate the energy created on them, if properly designed to seismic force.

Buildings with ornamental effects are to be designed with at most care. Few

projections and unrelated members can create more effects and may lead to failure.

Cantilever projections in buildings are provide in order to accommodate more space.

But this enhances occurrence of rotation and causes failure (Figure: 8). Probable

mode of failure will be crushing failure of columns. Pendulum effects in building

plan should be avoided. As inertia increases with height, pendulum effects will easily

cause failure to the building. Many buildings which failed during 2001 earthquake in

Gujarat, India are buildings with cantilever projections, unsymmetrical plans and

uneven openings [2]. Even symmetrical sections with unequal openings will cause

failure. Effects of openings in buildings will be discussed in modes of failure. Thus

for better performance during an earthquake, buildings are to be designed for

symmetry, regularity and simplicity.

5 POTENTIAL MODES OF FAILURE:

Structural members under designed to carry seismic forces fail easily than any other

members. Though nature of seismic forces are not predictable, the modes are failure

shown by members due to seismic forces are predictable. Each and every member

exhibits their own modes of failure. Modes of failure depend on shape, material and

method of construction. For discussion purposes, modes of failure are described as per

the materials used in construction of buildings.




5.1 Masonry buildings:

Usually masonry buildings are built using fire burnt bricks, solid concrete blocks and

with hollow concrete blocks. They are built together using mortar for providing good

bond. On a whole masonry building has wall, column, beam and other essential

structural members. For load bearing constructions masonry walls are important.

Consider a masonry wall which is supported only at the base. If a seismic force acts

perpendicular to the wall, it collapses by overturning. As the load is applied opposite

to the plane direction, the wall failed. If the load is applied to the plane the wall might

not be collapsed but slightly move from its initial position. Diagonal tension cracks

can be seen on the surface of the walls if the seismic load is acting on the plane.

Occurrence of cracks on walls depends on length to width ratio.

Figure 10: Modes of Failure

Walls A and B in above figure clearly explains the modes of failure that could happen

on occurrence of seismic force. For wall B the seismic load is in plane, as the wall is

unreinforced shear cracks may develop. This is due to “to and fro motion” of seismic

forces. Occurrence of diagonal cracks indicates the effect of length and width ratio.

Possibly the ratio is moderate for wall B. Horizontal cracks in gable ends may occur if

the roof truss is not fixed properly to the supports. This is due to transmission of truss

loads directly from the end purlins to the gable ends. Bending cracks in wall B is due

to compressive action from the supports provided by masonry columns. On seismic

force, wall A shows majority of bending cracks only. As wall A is not designed to

carry loads in perpendicular directions, this would have occurred.




If the walls are not supported properly to the columns, formation of cracks at the joint

connection may occur and the wall will fail by overturning effect. Due to non-proper

fixity, during earthquake force the roof truss may move from its original position and

fail. For flat roof cases, the inertia developed by roof will be transmitted to the walls

beneath it. Majority of inertia force will be transmitted to wall B. This happened due

to larger stiffness of wall B in x-direction. This action reduces the bending and

overturning effect of wall A, if wall A is fixed clearly to its supports [1]. More often

damages start from openings provided in wall panels. They also decide the strength of

walls. For increased strength the openings provided in wall panels should be small in

size and centrally located. Diagonal cracks usually start from corner of openings and

centre of wall segments. This type of cracks even causes complete collapse of the

building [1].

Columns and beams in frame construction carry heavy loads during an earthquake.

Mostly these members fail at their junctions due to hinge formations. A framed

structure is to be designed with “weak beams and strong columns”. If this is followed

collapse of entire structure can be prevented. Hinge formation at the junction creates

easy collapse of the structure. Columns and beams are to be designed by sufficient

reinforcement with proper spacing of shear connectors. Stirrups with proper spacing

protect these members from failing from shear. Connection between roofs with

beams and columns has to be perfect such that they behave as one. If not sliding of

roof will occur and may cause severe damage.

Lack of transverse reinforcement in beam – column connections, column splice

regions and inadequate splice length combined with short column effects could cause

complete collapse of the structure [4]. In adequate load path formation may also




collapse the structure. On a whole earthquake effects occur in both the directions of

the building and creates bending and shearing effects together, such that these

possible failure modes often occur in combination. Building with unsymmetrical

plans often fails by torsion and wrapping. This mode of failure creates cracks in shear

walls. Due to failure of ground during an earthquake, foundations may fail by

differential settlement [1].

5.2 Stone buildings:

Stone buildings often use round stone boulders. Some times cut or chiselled, polished

or unpolished stones are used. They are joined together using mortar either of cement

or mud. This type of buildings is more built in rural areas than urban. Majority of

stone buildings are constructed as load bearing ones. During an earthquake stone

buildings easily fail at corners and at T-junctions. This results to wall overturning and

roof collapsing. Due to uneven stone shapes and poor mortar usage in developing a

bond this would have happened. During shaking the tensile strength of mortar and

stone exceeds the limit and make the walls (Wythes) to bulge and collapse [7].

Few stone buildings will fail if their roof slabs are not properly tied to the walls.

During seismic load the roof will be displaced and stone associated with it will cave

in. Provision of heavy slabs as roof should be avoided in this type of buildings. This

type of buildings is not recommended in the areas of high seismic influence. This type

of buildings is often provided with stone footings. Stone footings on soft soil perform

very poor during an earthquake. The 26th January 2006 earthquake in Gujarat, India

caused major damage to this type of buildings and claimed thousands of lives [2].




5.3 Wooden buildings:

As a structural material, wood offers a good amount of resistance towards seismic

load. With more absorbing capacity wood can easily dissipate the energy produce on

it. Though wood as many qualities to survive seismic load, it fails on certain aspects.

Regarding roof tiles, it had to be fixed properly to the frame. If not falling of roof tiles

during an earthquake may hurt people. Wooden buildings mostly damaged by fire due

to earthquake. Prevention of fire is most important in case of wooden buildings. Joints

connecting columns and girders frequently fail during lateral loading. Due to

structural deterioration and roof weight the restoring forces at the joints are impede to

movement. This leads to sliding after joint fracture. Even buildings with horizontal

bracings will not survive this [3].

Figure 13: Possible wooden failures

Usually in storeys more than two, lower storey suffers more damage than any other

storey. On failure lower storey falls first and other storeys remain undamaged. If

anchor bolts are not fixed properly to the foundation, sliding of entire structure may

happen [1]. If wooden buildings are built over soft soil, chance of getting damaged

during an earthquake is more. This may be due to soil settlement or soil liquefaction.

5.4 Earthen Buildings:

Earthen buildings are highly vulnerable to seismic effects and easily fail during an

earthquake. Damage is always much more severe in two storeyed when compared to

single storeyed. Mostly crushing failure occurs in this type of construction. Corner

failures and out of plane collapse of walls are common mode of failures. Failure of




roofs is common in single storeyed and complete disaster may happen in two

storeyed. Certain factors influence the damage in this type of buildings namely heavy

tile roof, lack of horizontal reinforcement, poor adobe quality, walls too high and too

long and many more [1].

As earth is weak in tension, vertical and horizontal reinforcements are needed to

overcome failure. Though reinforcement is provided earthen buildings fail due to their

nature of brittleness. Ductility of material earth is very low when compared to any

other material. Provision of openings close to corners and large door and window

openings can stimulate the failure pattern.

Figure 14: Possible earthen failures

6 IMPROVEMENT OF STRUCTURES:

Structure prone to earthquake can be improved by following certain construction

practices. Few methods should be adopted before constructing a new building and

retrofitting methods should be followed on existing building. This is to reduce the

vulnerability of the building to earthquake.

Risks of failure can be overcome by implementing simple guidelines such as:

a) Following simple geometry for the building. If not, separation joints should be

used.




b) Openings should be provided as per the guidelines.

c) Control on thickness, length and height of walls in a room.

d) Proper use of reinforcement when using traditional materials.

e) Good quality of materials and workmanship.

f) Supervision from experienced personals.

g) Retrofitting existing buildings.

h) Overall reference of guidelines specified for non-engineering constructions.

6.1 Masonry buildings:

6.1.1 Mortar:

The cement mortar should be used in the ratio of 1 parts of cement with 4 parts of

sand for category I and 1:6 for category II,III,IV [1] (Ref table:1 ) or even richer mix

can be used.

Table 1: Categories of buildings for strengthening purposes




6.1.2 Seismic bands:

A reinforced concrete flat runner through both external and internal masonry walls at

plinth level, levels of lintels of doors and windows and at the ceiling level of roofs [8].

These seismic bands are a very important feature in masonry buildings towards earth

quake resistant. These bands hold the building together and makes it to move as a

single unit during shaking [9]. The size of the band and reinforcement used depends on

length of the walls between the perpendicular cross walls. Reinforcing bars will be Fe

415 type (TOR or HYSD bars) [8].

Horizontal reinforcement helps walls to gain strength towards horizontal bending

against plate-action due to inertia load. It also helps in preventing shrinkage and

temperature cracks. The amount of reinforcing and minimum size of the band depends

upon importance of buildings, seismic coefficient, type of soil and number of storeys

[1].




6.1.3 Openings in bearing walls:

As doors and windows reduce the lateral loads resistance of the walls, they should be

located centrally and preferably small in size. The requirements of openings with

respect to good seismic performance are shown in fig: 17.




6.1.4 Vertical reinforcement:

Vertical reinforcements are to be provided at corners of walls from the foundation

concrete and should be covered with rich mortar mix. Window openings larger than

60 cm in width will also need such reinforcement [8]. The diameter of the reinforcing

bars depends on number of storeys. These vertical bars start from foundation pass thro

all seismic bands effectively tied to horizontal and lateral ties using binding wires. On

lapping of vertical reinforcement, a minimum of 50 times diameter of the bar has to

be provided [8].




Eave and gable band:

6.1.5 Dowel at corners and junctions:

As a supplement to seismic bands dowels are inserted at regular intervals of 50 cm

and taken into walls to entire length. This is to provide full bond strength. Wooden

dowels are also used successfully instead of steel dowels [3].




6.1.6 Reinforcement in Hollow and solid concrete block masonry:

All specifications for this type of construction are same as brick masonry. Hole

formation for vertical reinforcement in solid block walls is not feasible. Special

concrete blocks with one hollow are cast and used at the bar-points. In hollow blocks

holes are available and this eases the provision of vertical reinforcement.

6.2 Stone buildings:

Mortar:

Mortar can be of same type that had used for masonry construction. Clay mortar

should be avoided because of its low bonding capacity and less strength towards

earthquake.

6.2.1 Dimension control for stone masonry using cement mortar [8]:

a) Heights of buildings are restricted to one storey for category I and II and can

be two storeys for III and IV category.

b) Thickness of wall is limited to 350 mm and stones of inner and outer walls are

interlocked with each other.

c) Maximum storey height should be 3.2 m and span of walls between cross

walls has to be limited to 7 m.

d) For rooms larger than 7m, buttress wall should be provided at intervals not

more than 5m.

e) Buttress should have a top width equal to wall thickness and base thickness

equal to one sixth of the wall height.




f) Stone masonry buildings should not be taller than 2 storeys when built with

cement mortar and 1 storey when built with mud mortar [7].

6.2.2 Control of openings in bearing walls:

For perfect provision of openings, the ratio of total length of opening in wall to length

of wall in a room should not exceed 0.5 in single storeyed and 0.42 in two storeyed.

Distance of opening from inside cover should be greater than or equal to 450 mm.

And width of pier between two consecutive openings should be greater than or equal

to 600 mm [8].




6.2.3 Masonry work:

Construction lifts in stone buildings is restricted to 600 mm. Through stones or bond

stones should be used at every 600 mm height and at a maximum spacing of 1.2 m

along the length. Wooden planks, Hooked steel links and S-shaped steel ties can be

used as alternatives to through stones. This is vital in preventing the wall from

separation as Wythes [7].

Bonding elements of concrete bars 50mm x 50 mm section with 8mm dia bars placed

centrally or solid concrete blocks of 150mm x 150mm x wall thickness, can be used in

place of through stones. At wall corners and at T-junctions, long stones of 500mm-

600mm in length can be used [8].





Seismic bands are same as masonry buildings provided continuously in all internal

and external walls without any break. Requirement of reinforcing bars is RC bands is

given in table: 2. For sloping roofs, triangular gable walls are enclosed in eave level

band and a band at the top of the gable wall. The bands are to be cast directly on the

masonry and its top surface is made rough to achieve good bond with masonry. In

lintel and plinth bands, stones are projected out of the concrete by 50mm to 75 mm.

this is to done to continue that into stone walls [8]. It is important to provide at least

one band either roof or lintel band in stone construction. This provides integrity to the

building and holds the walls together to resist horizontal effects [7].

6.2.5 Vertical reinforcements:

Vertical reinforcements are provided at corners and at T-junctions at window sill level

and at jambs of doors and large windows. Vertical reinforcement is made to continue

from foundation level to roof band at the top. If the opening provided in the building

does not comply with standards they are reinforced or boxed in reinforced concrete all

– round or reinforcement bars provided in jambs through the masonry [3].

During installation of the vertical reinforcements, PVC casing pipe of 100mm

external dia of 600-750mm long is used. Around which the masonry is built and the

pipe is removed once the masonry hardens. In that place, a rod 12 mm dia of 600mm

ling is inserted and well compacted using M 20 concrete [8].




6.2.6 Dimension control for stone masonry using mud mortar [8]:

g) Heights of buildings are restricted to one storey for category I and can be two

storeys for II, III and IV category.

h) Thickness of wall is limited to 450 mm and stones of inner and outer walls are

interlocked with each other.

i) Maximum storey height should be 2.7 m and span of walls between cross

walls has to be limited to 5 m.

j) For rooms larger than 5m, buttress wall should be provided at intervals not

more than 3.5m.

k) Buttress should have a top width equal to wall thickness and base thickness

equal to one sixth of the wall height.

Masonry work is same as stone work in cement mortar. In few cases seasoned

wooden battens of size 50mm x50 mm can be used as bonding element. Seasoned

wooden battens of size 60mm x 60mm can be used as an alternative to long stones at

wall corners and T-junction.

6.2.7 Control of openings in bearing walls:

Total length of openings in a wall should be equal to 0.33 of wall length in all

categories of constructions. Distance of openings from inside corner should be greater

than or equal to 600 mm. Pier widths between consecutive openings should be greater

than or equal to 600 mm [8].


Horizontal bands made of wood are used in this type of construction. Wooden planks

of rectangular sections, effectively spliced and held by lateral members in lattice form

are used in timber available regions as horizontal bands. This is a perfect alternative

to steel reinforcing. Same as cement mortar construction the wooden bands are

provided continuously through the building [1].




6.2.9 Vertical reinforcement at corners:

Two wooden planks of size 50mm x 30mm is nailed together to form an L-section.

And this vertical member is nailed to wooden seismic bands at plinth, sill, and lintel

and eaves level. This vertical reinforcement is to be placed at all corners of the room.




6.3 Wooden buildings:

6.3.1 Building plan:

The entire plan of the building is to be divided by bearing wall lines. The maximum

spacing of the bearing wall is limited to 8m. The maximum width of openings is

limited to 4m and should be at least 50 cm away from the corner. Bearing walls of

lower storey are to be supported by continuous foundations, through sills or by

column pedestal.

Bearing lines of upper storey are made to be supported over bearing lines of lower

storey. Bearing wall types depends on type of construction. The height of building is

always limited to two storeys [1].

6.3.2 Foundations [8]:

Frame construction often starts above plinth level over masonry or concrete. The

super structure should be connected to the foundation in one of the two ways.

a) Small buildings of one storey with area less than 50 sq.m will made to rest on

a firm plane ground such that the building is free to slide laterally during

ground motion.




b) The superstructure will be fixed rigidly to the plinth masonry or concrete

foundation.

6.3.3 Joints:

Joints are high prone areas of damage during an earthquake. The joints are to be

effectively nailed or bolted together. Usage of metal straps in important joints is

highly recommended. Joints like, columns with sill and wall plates with horizontal

members are areas of most interest.

6.3.4 Frames:

In general two types of frame construction methods are followed: Stud wall

construction and Brick nogged timber frame.

General [1, 8]:

a) Sheathing boards are to be properly nailed to the timber frame, if not bracings

should be used.

b) The diagonal bracings are to be framed to the verticals or should be nailed to

the surface.

c) The sill in stud wall construction has to be connected to the foundation using

anchor bolts. Anchor bolts are provided on both sides of joints of sills.




d) The size of studs used should not be less than 40mm x 90 mm. Storey height

should not be more than 2.70m

e) All studs will be connected to the adjacent studs using horizontal blockings at

every 1.5m in height.

f) The minimum dimension of braces is 20mm x 60mm. It should be effectively

tied to the main member.

g) The vertical framing members in brick nogged should have minimum finished

size of 40mm x 100mm spaced not more than 1.5m apart.

h) Horizontal framing members in brick nogged construction shall not be spaced

more than 1m apart.

i) The corner post should consist of three timbers, two of equal in size to studs

and the third being a size to fit and as to make a rectangular section.

j) Horizontal bracing should be provided at wall corners and at T-junctions of

walls at sill, first floor and eave level.

k) The top of studs should be connected to top plates, whose dimension should

not be less than the dimension of the stud.




6.4 Earthen Buildings [1]:

This type of buildings is more prone to earthquake effects. As clay is the prime

material in this type of construction, selection of clay should be done with utmost

care. Certain tests are available to select the type of clay which is suitable for

construction.

6.4.1 Walls:

a) Height of the building should be restricted to one storey in zone I and two

storeys in Zone II,III and IV

b) Vertical buttress should be provided for walls of longer lengths.

c) The height and width of an opening of the wall is controlled. Height should

not be greater than 8 times of its thickness and width of opening should not be

more than 1.20m

d) A minimum of 1.20m distance should be maintained between the corner and

opening.

e) To increase the seismic stability of the walls, pilasters should be provided at

equal intervals at all corners and at junctions.

f) A minimum of 50cm should be maintained as bearing length of lintels on each

side of the opening.

6.4.2 Foundations:

a) In zones I and II, construction of earthen buildings in soils of type firm sub-

soil, sandy loose soils, poorly compacted clays and fill materials should be

avoided.

b) Constructing over water table is not encouraged.

c) Sufficient amount of foundation depth should be maintained as per the

guidelines available.

d) Footing should be constructed using stones or bricks with rich cement mortar.

Usage of mud mortar in construction of footing should be avoided.




e) A minimum height of 300mm from water table should be maintained while

constructing plinth level.

6.4.3 Roofs:

a) Light material should be used as roof covering. Heavy covering such as RCC

should not be used.

b) Roof should not be made to rest over the walls directly. Preferably wooden or

brick restings should be provided over the walls for this purpose.

c) Roofs should be made waterproof such that the penetration of water is

avoided.

6.4.4 Horizontal bands:

a) Two continuous bands made of wood should be used for this purpose. One at

lintel level and other at roof level. Unfinished rough cut wood should be used.

b) Horizontal bands should be effectively tied at corners and at wall junctions.

6.4.5 Vertical reinforcement:

a) Vertical reinforcements are provided in a mesh form of bamboo made or cane

or with collar beams and bands.

b) Mesh form of reinforcement is highly recommended in seismic areas. The

vertical mash should be tied effectively to horizontal bands at all level.




c) These meshes are to be started from the foundation and should be tied with

lintel and roof bands.

d) Diagonal bracings can be provided using cane members. These have to be

effectively nailed to the framing members.

6.5 Reinforced concrete buildings [1]:

6.5.1 Concrete mix:

Proportion of 1:2:4 is to be maintained while preparing the mix. The amount of water

in the concrete should be enough to make a ball out of the mix by hand. Compaction

should be achieved using vibrators or manually. After concrete cast, it has to be cured

for at least 14 days.

6.5.2 Reinforcement:

a) Minimum clear cover should be maintained in slabs, beams and column.

b) Longitudinal bars should be tied to transverse bars and stirrups.

c) Beams should be reinforced both on top and at bottom. Minimum of two bars

of 12 mm dia is used.

d) Splices should be placed within two at least two stirrups. Vertical shear

stirrups should be closely spaced.




e) In column vertical reinforcements should be provided at all faces. Its strength

can be increased by using ties with adequate anchorage and end hooks.

f) Corner columns should be effectively provided with steel and minimum

spaced lateral ties.

g) Connection between column and beam should be well anchored to obtain full

strength.







7 REAL PICTURES OF FAILURES:

a) Location: Bhuj, Gujarat, India - 26thJanuary 2001

Type of failure: Column failure in open first storey due

to hinge failure, Cantilever projection.

Improvement measures: Sufficient hoop reinforcement

should be provided in order to eliminate failure in hinge

region. Increase in size of column and reinforcement,

avoiding cantilever projection in open first storey.

b) Location: Bhuj, Gujarat, India - 26thJanuary 2001

Type of failure: Failure of load bearing masonry walls

and lintel level crack.

Improvement measures: Providing horizontal seismic

bands at all levels of the buildings and vertical

reinforcement at corners. Provision of reinforcements in

walls could even make the structure to perform well.

Effective tying of walls to floor and roof should be done.

c) Location: Bantul, Yogya, Indonesia – 27th May 2006

Type of failure: Failure due to racking shear could be

due to diagonal compression or tension.

Improvement measures: Control of opening sizes,

strengthening of masonry around openings, provision of

lintel and sill band.

d) Location: Banda Aceh, Indonesia – 26th December 2004

Type of failure: Beam-column connection failure.

Improvement measures: Provision of transverse

reinforcement in beam-column connection, column splice

regions and provision of adequate splice length in column.




e) Location: Banda Aceh, Indonesia – 26thDecember 2004

Type of Failure: Column shear failure.

Improvement measures: Provision of shear

reinforcements in columns. Effective connection between

beam and column has to be done.

f) Location: Bantul, Yogya, Indonesia – 27th May 2006

Type of failure: Brick out of wall collapse combined

with roof collapse.

Improvement measures: Provision of reinforcement in

between walls, effective reinforcement at corners.

Introducing horizontal bands in each level.

g) Location: Kachchh, Gujarat, India - 26thJanuary 2001

Type of failure: Complete collapse of masonry buildings

Improvement measures: providing good bond between

masonry, reinforcement, seismic bands, light roof, control

on openings. In overall an efficient construction practice

has to be followed.

h) Location: Maninagar, Gujarat, India - 26thJanuary 2001

Type of failure: Plastic hinging and buckling failure

Improvement measures: Provision of efficient concrete cover

and hoop reinforcement. Thickness of the column could have

been improved in order to carry the load applied.




i) Location: Jabalpur, India – 1997 earthquake

Type of failure: Typical joint failure in mud house,

shear cracks

Improvement measures: Provision of vertical cane

reinforcement and wooden horizontal bands. Control on

height of wall and opening in wall should be followed.

j) Location: Kobe, Japan -1995 earthquake

Type of failure: Typical first storey failure usually seen

in wooden buildings, crushing of column and separation

of joint members.

Improvement measures: All bearing wall line of

upper storey should be supported by bearing wall lines

of lower storey. Frame members should be effectively

nailed to each other. Bearing lines of lower storey

should be supported by continous foundation.

k) Location: Killari, Maharashtra, India-1993

Earthquake

Type of failure: Delamination of Wythes followed by

inner and outer stone wall collapse.

Improvement measures: Provision of through stones,

horizontal bands and vertical ties.

l) Location: Bantul, Yogya, Indonesia – 27th May 2006

Type of failure: Collapse of one side wall due to poor

reinforcement.

Improvement measures: reinforcement at T-junctions

and corners. Horizontal bands at all levels of the

building.




8 DOMESTIC CONSTRUCTION IN INDIA:

India though being an earthquake prone country it has nearly 195.0 million non-

engineered dwelling units. This is as per 1992 survey of India on non-engineered

buildings [3].

As a native of southern part of India-Chennai, Tamilnadu; I have personally

experienced few tremors of earthquake in the past and Tsunami on 26th December

2004. Any how we have not faced any damage by these disasters. Though my home

town is in seismic zone IV (moderate exposure to earthquakes) there are many non-

engineered dwelling units. Even my own house is a non-engineered single storey

load-bearing masonry wall type, which was constructed a decade ago with minimal

cost by locally employed persons.

Fire burnt bricks, graded cement, river sand, FE 415 steel bars are used for the

construction. Building is symmetrical and square in shape. Masonry columns are used

to support the walls over which RCC roof slab is place. Such that the inertia

transmitted by the roof will be carried by the adjoin walls. Roof to wall and column

connection is good. Horizontal seismic bands are provided through the building. But

provision of vertical reinforcements at corners and at T-junctions is absent. Openings

of windows are not controlled and distance from corner of walls is less than 100mm.

Footing is at the depth of 1.5 m from the ground level. Footings are connected to each

other using plinth beam. Horizontal reinforcements are provided in between the

bricks during wall construction. Parapet wall is provided over the roof. As parapet

wall is not connected to any member of building, it may collapse during an

earthquake.

Vulnerability of my house to earthquake action is moderate. During an earthquake

failure may occur near the corners and at near the openings. Diagonal shear cracks

can be seen. Joint failure may occur near wall and masonry column junction. In plane

failure may occur at some places. Procedures on how to built seismic resistant

masonry brick units are discussed in previous chapters. As my house is an existing

one, few retrofitting methods will help the structure to with stand an earthquake.

Retrofitting involves repair, strengthen and modification of certain structural elements

to with stand effects caused by earthquake.




8.1 Local modifications:

Local modification involves works such as closing the opening or providing

reinforcement around it. As in my house the openings do not comply with the

requirements, the openings are reinforced or boxed in reinforced concrete all – round

or reinforcement bars in jambs through the masonry [3].

8.2 FRP retrofit:

FRP composites are flexible and easy to apply. By following surface mounted

techniques the FRP strips are applied to the walls vertically and diagonally to improve

out of plane capacity in both way bending. Diagonal strip increases the in-plane shear

capacity [3].




Using near surface mounting technique, FRP rods can be placed in to the masonry

walls. For this the masonry walls are to cuttted horizontally and vertically and FRP

rods are placed in to the gaps followed by covering it a layer of specified adhesive [3].

8.3 Strengthening of existing walls:

Method of confining by more ductile material i.e. wire mesh can be used. Two steel

meshes of size 50mm x 50mm is attached to both sides of the wall and connected by

steel at 500-700mm interval. A micro concrete layer is applied on both sides and the

connected links are grouted. The brickwork in between the Ferro cement layer will

behave efficiently when subjected to lateral load [3].

8.4 Pre-stressing for wall strengthening:

Pre-stressing bars can be introduced in pairs in opposite sides of wall so that the out of

plane bending of walls can be eliminated. In single storey building the vertical steel is

anchored to the foundation [3].

8.5 Strengthening the corners:

As corners in my house are weak, they are more prone to earthquake effects. In order

to eliminate the failure the corners have to be strengthened. Plaster is removed for a

height of 400mm above 80mm of the plinth level with a length of 300mm. the

exposed joints are raked to a depth of 20mm and cleaned using wire brush. A welded

mesh of 25mm x 50mm with 8mm gauge length is taken with a width of 350mm and




placed on the wall using long nails. Then with the help of plaster 1:4 ratio the mesh is

covered up to 15mm thick and cured for 14 days [3].

8.6 Strengthening wall to wall connection:

As T and L-junctions in my house are not reinforced, they can be integrated and

anchored by effective sewing of perpendicular walls. Holes are drilled in an inclined

manner and polymer grout is injected after inserting steel reinforcement [3].




CONCLUSION:

In countries at risk from earthquake action, most people are living in non-engineered

buildings. They are at risk from collapse of their own homes. To avoid this quality

domestic construction has to be improved. It doesn’t mean that more amount of

money has to be spent for earthquake resistant construction. Even with locally

available material it can be achieved. Methods discussed in this report are more

economical and attained using local materials. Method and measures suggested may

vary from place to place. The methods can be improved better on basis of previous

earthquake intensity reports. Due to constraint only few methods are discussed here.

While building a dwelling unit, the owner or the builder may refer any other

guidelines other than this. The final motto has to be construction of earthquake

resistant buildings.




REFERENCES:

1. The Associated cement companies Limited, Mumbai, India, 2001 - “Guidelines for

earthquake resistant non-engineered construction”.

2. Gujarat Relief Engineering Advice Team (GREAT) publication, 2001 -“Repair and

strengthening guide for earthquake damaged low-rise domestic buildings in Gujarat,

India”. (www.arup.com/_assets/_download/download197.pdf -Accessed on 27/03/09)

3. Government of Tamilnadu, UNDP, India, July 2006 – “Guidelines for retrofitting of

buildings”. (www.un.org.in/untrs/reports/Retrofitting_Guidelien_16th_%20Nov_2006.pdf -

Accessed on 27/03/09)

4. Murat Saatcioglu, Ahmed Ghobarah, Ioan Nistor – ISET Journal of earthquake

Technology, Paper No.457, Vol.42, No.4, December 2005, pp.79-94 – “ Effects of the

December 26,2004 Sumatra Earthquake and Tsunami on Physical Infrastructure”.

(home.iitk.ac.in/~vinaykg/Iset457.pdf- Accessed on 27/03/09)

5. Jag Mohan Humar, David Lau, and Jean-Robert Pierre – NRC Reasearch press web,

November 23, 2001-“ Performance of buildings during the 2001 Bhuj

earthquake”.(www.caee.uottawa.ca/Publications/Lessonf%20grom%20previous%20

EQs/PDF%20Files/India.pdf- Accessed on 27/03/09)

6. Dr D.K.Paul, Professor and Head – Department of Earthquake Engineering, IIT

Rourkee,India- Lecture PPT - “Buildings Vulnerability, building types and common

problems, typical earthquake damage pattern”. ( www.quakesafedelhi.net/rollout/Paul.pdf-


7. IIT Kanpur,India-Buildings Materials and Technology Promotion Council,New

Delhi,India - IITK-BMPTC Earthquake Tips, July 2003 -“ How to make Stone Masonry

Buildings Earthquake Resistant?”.(www.iitk.ac.in/nicee/EQTips/EQTip16.pdf-Accessed on

9/04/09)

8. Prof.Anand S.Arya, National Seismic Advisor, GOI-UNDP DRM Programme, Ministry

of Home Affairs, Government of India, October 2005 – “Guidelines for earthquake

resistant reconstruction and New construction of Masonry buildings in Jammu & Kashmir

state”.( www.ndmindia.nic.in/EQProjects/Kashmir%20Final.pdf-Accessed on 9/04/09)




9. IIT Kanpur,India-Buildings Materials and Technology Promotion Council,New

Delhi,India - IITK-BMPTC Earthquake Tips, July 2003 – “ Why are horizontal bands

necessary in masonry buildings?”. (www.iitk.ac.in/nicee/EQTips/EQTip14.pdf-


FIGURES AND TABLES:

1. Figures: 11-12-13-14-24-27-19-32-33-34-35-36-37-38

Table: 1

The Associated cement companies Limited, Mumbai, India, 2001 - “Guidelines for

earthquake resistant non-engineered construction”.

2. Figure: 7

Dr D.K.Paul, Professor and Head – Department of Earthquake Engineering, IIT

Rourkee,India- Lecture PPT - “Buildings Vulnerability, building types and common

problems, typical earthquake damage pattern”. ( www.quakesafedelhi.net/rollout/Paul.pdf-


3. Figures: 15-16-18-19-20-22-23-25-26-28-30-31

Tables: 2-3

Prof.Anand S.Arya, National Seismic Advisor, GOI-UNDP DRM Programme, Ministry of

Home Affairs, Government of India, October 2005 – “Guidelines for earthquake resistant

reconstruction and New construction of Masonry buildings in Jammu & Kashmir

state”.( www.ndmindia.nic.in/EQProjects/Kashmir%20Final.pdf-Accessed on 9/04/09)

4. Figures: 17-21-39-40-41-42

Government of Tamilnadu, UNDP, India, July 2006 – “Guidelines for retrofitting of

buildings”. (www.un.org.in/untrs/reports/Retrofitting_Guidelien_16th_%20Nov_2006.pdf -





REAL PICTURES:

1. Pictures: a-b-g-h

Jag Mohan Humar, David Lau, and Jean-Robert Pierre – NRC Reasearch press web,

November 23, 2001-“ Performance of buildings during the 2001 Bhuj

earthquake”.(www.caee.uottawa.ca/Publications/Lessonf%20grom%20previous%20

EQs/PDF%20Files/India.pdf- Accessed on 27/03/09)

2. Pictures: c-f-l

Teddy Boen, Senior advisor –World Seismic Safety Initiative-“Yogya Earthquake 27 May 2006,

Structural Damage Report”. (www.eeri.org/lfe/pdf/indonesia_yogya_structural_damage.pdf-


3. Pictures: d-e

Murat Saatcioglu, Ahmed Ghobarah, Ioan Nistor – ISET Journal of earthquake

Technology, Paper No.457, Vol.42, No.4, December 2005, pp.79-94 – “ Effects of the

December 26,2004 Sumatra Earthquake and Tsunami on Physical Infrastructure”.

(home.iitk.ac.in/~vinaykg/Iset457.pdf- Accessed on 27/03/09)

4. Pictures: i-j-k

Earthquake Engineering Research Institute (EERI), International Association for

Earthquake Engineering (IAEE)-“World Housing Encyclopedia”

(http://www.world-housing.net/whereport1view.php?id=100056

http://www.world-housing.net/whereport1view.php?id=100094

http://www.world-housing.net/whereport1view.php?id=100051)

(Accessed on 10/04/09)

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non-engineered buildings