11 Masonry Structures
Load-bearing construction in the affected area is mostly masonry, with some adobe. Masonry
buildings in the area are not designed, but merely constructed based on traditional practices
that may include some rules of thumb. Masonry construction constitutes over 95 percent of the
building stock in the affected area, which by and large did not perform well. Over 1,200,000
masonry buildings either collapsed or were severely damaged. Masonry construction is present
in both rural and urban areas.
Masonry construction in each region has special characteristics due to the bias towards locally
available material, limitations of construction skills, and constraints to construction activity. Past
earthquakes have highlighted the inherent weaknesses of this type of construction, and the lessons
from the 2001 Bhuj earthquake offer yet another vivid demonstration to the local populace of the
vulnerability of their hand-made, unengineered dwellings.
This chapter gives an account of the state of the practice of masonry construction in the
Kachchh region and a review of its performance during the 2001 Bhuj earthquake. Relevant
Indian Standards and other pertinent literature on masonry construction available in the country
are also presented.
GROWTH OF CONSTRUCTION IN THE KACHCHH REGION:
The Kachchh region has two distinct eras of development. Early construction took place
under royal families that lived in the region over the past five centuries. More recent and more
significant construction in the region was driven by the India-Pakistan partition in 1947. On the
recommendation of Mahatma Gandhi, the Government of India granted 6,070 hectares (15,000
acres) of land near the Port of Kandla for the purpose of developing a township and commissioned
the Sindhu Resettlement Corporation (SRC) Limited in 1948 with the main aim of settling and
rehabilitating the persons displaced from the Sindh province of West Pakistan, now known as
Pakistan. In 1955, after a careful review, the government revised the land available to SRC to
2,600 acres; the Port of Kandla received an adjoining 4,320 acres.
By 1958, SRC completed a major part of the construction in two locations, which are today’s
cities of Adipur and Gandhidham. However, the growth of the region during 1950-1960 was less
than expected. The slow increase in livelihood was due to marginal growth in commerce, trade,
industry, and communications. The Anjar earthquake in 1956, whose epicenter was 55 km from
Bhuj, and two wars with Pakistan in 1965 and 1971 also discouraged many settlers, and, in fact,
there was a significant exodus during 1960-1970. However, the growth of the Kandla Port Trust,
the construction of new highways during the 1970s, and the commissioning of the Broad Gauge
Railway line in the 1980s, led to an influx of people into the region. Though relatively little
Masonry Structures 188
construction took place during 1960-1995, recent trends show an upsurge in new construction.
One interesting feature of this construction is that the use of lime mortar became popular in
masonry construction due to the severe shortage of cement experienced countrywide during the
Over the past 50 years, the main organizations that have led construction activity in the Kachchh
region were the SRC Limited, the Kandla Port Trust, the Indian Railways, the Department of
Telecommunications, and the Military Engineering Service. These organizations were responsible
for improving infrastructure and introducing new construction technology. The SRC Limited
popularized the use of hollow cement block walls, lintel bands, and vertical reinforcements at wall
corners in masonry construction, and ties/stirrups with 135-degree hooks in reinforced concrete
construction. Such structures performed well during the 2001 Bhuj earthquake.
Construction in other parts of Kachchh was only as a consequence of the development in
the Gandhidham-Adipur areas. Migrant artisans from Gandhidham area carried the skill and
technology to the interiors, and implemented many private projects. Government construction
techniques stood as examples for citizen builders to emulate. For instance, lintel bands were
common in the construction of the Indian Railways. This may have inspired a few individuals to
include these in their own houses.
The excessive use of cement-based masonry and the gradual exclusion of lime from masonry
was a net outcome of the recent construction. This has resulted in widespread brittle damage in
such masonry structures.
OVERVIEW OF DAMAGE
Collapses of masonry dwellings in the Kachchh region were responsible for the majority of
fatalities during the 2001 Bhuj earthquake. The meizoseismal area and adjoining areas that sustained
intensities of shaking IX and X include many important towns and villages of the Kachchh region
(Figure 11-1), some of which are densely populated. For instance, the town of Bhuj has a population
of about 160,000, Anjar of about 55,000 and Bhachau of about 20,000. These towns lie south of the
epicenter. There are other villages and towns northwest of the epicenter, such as Manfara and Rapar,
which also suffered significant damage. Table 11-1 gives an estimate of the masonry structures and
huts damaged during the earthquake. Most of the damage to masonry structures occurred in the
Kachchh district, which lies in the most severe seismic zone (V) of the country.
Table 11-1. Damage statistics for different types of
construction in the Kachchh region.
Type of Construction Complete Partial
Pukka (well built) houses 187,122 510,419
Kachcha (poorly built) houses 167,205 387,320
Huts 16,266 34,295
Total 370,593 932,034
* From www.quakegujarat.com, official site of
Government of Gujarat (September 2001)
Masonry Structures 189
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Figure 11-1. Epicentral region of the 2001 Bhuj earthquake showing villages
discussed in this report.
Aerial photographs of damage are available for Bhachau, Anjar, Ratnal, and adjoining areas
of Gandhidham, all in the epicentral region. Figure 11-2 shows the near total destruction of the
village of Bhachau, 8 km from epicenter. The town of Ratnal and villages near Gandhidham,
44 km from the epicenter, sustained similar, near complete, devastation. In Anjar, a town where
nearly 300 school children died while marching in the Republic Day parade, building damage
was widespread. While devastation was nearly complete in some areas, others escaped with only
moderate damage. Initially, significantly different soil conditions were suspected for the contrasting
damage pattern, but it was the older construction that collapsed, while the newer construction
suffered only moderate damage.
Damage patterns showed serious lack of earthquake-resistant construction features in the
region (Figures 11-3 and 11-4). Villages reduced to rubble showed a more or less uniform choice
of construction material and techniques. The overall analysis of these damages reiterates the ills of
masonry construction. Random rubble with mud mortar is the most vulnerable type of construction.
Wall failure was the most common cause of structural collapse (Figure 11-5). In a few cases,
the roof alone collapsed, causing casualties (Figure 11-6). Failure of reinforced concrete slab
roof system was present where slab reinforcements lapped at the same location, creating a weak
link for fracture (Figure 11-7). Masonry in mud mortar has inherently very poor shear strength.
As a consequence, wall thicknesses are necessarily large, sometimes as thick as 750 mm. These
thick walls were often not made into a single wythe with interlocking stones that run through
the thickness of the wall. In most instances, these walls sustained separation of wythes, thereby
losing even the vertical load carrying capacity (Figures 11-8 and 11-9).
Masonry Structures 190
Figure 11-2. Aerial photo of near total Figure 11-3. Damage to masonry construction
devastation of village Bhachau. due to inadequate connections between the walls.
Figure 11-4. Damage to masonry construction Figure 11-5. Collapse of this masonry structure
due to inadequate connections between the walls. was due to wall failure.
Figure 11-6. In a few instances, such as this Figure 11-7. Reinforced concrete roof slab
masonry structure, the roof alone was responsible with slab reinforcements lapped at the same
for structural collapse. location failed.
Masonry Structures 191
Figure 11-8. Lack of through-stones caused Figure 11-9. Separation of wythes caused
separation of wythes. collapsed of wall and roof.
TYPES OF CONSTRUCTION
Masonry dwellings in the Kachchh region include many types of load-bearing construction.
In older construction, walls were made from rammed earth and adobe or uncut stone masonry
with mud mortar. The roof is generally wooden trusses and clay tile. With the passage of time
and the numerous changes that took place over the last 50 years, present day stone masonry uses
cut/dressed stones or burnt clay bricks, cement mortar, and reinforced concrete slabs. Dressed-to-
size or cut-stones were used in stone masonry for walls in urban areas and in cases where owners
could afford higher costs. However, random rubble stone masonry construction predominates
in the Kachchh region. Consequently, the building stock in the region has a wide spectrum of
masonry construction techniques (Figures 11-10 through 11-16). These include:
• Random rubble stone masonry (uncoursed) in mud/cement mortar with clay tile roof.1
• Semi-dressed/dressed stone masonry (coursed) in mud/cement mortar with clay tile
• Clay brick masonry in mud mortar with tile roof.
• Semi-dressed/dressed stone masonry (coursed) in mud/cement mortar with reinforced
• Random rubble stone masonry (uncoursed) in mud/cement mortar with reinforced concrete
• Burnt clay brick masonry in mud/cement mortar with clay tile1/reinforced concrete slab
• Solid/hollow cement block masonry in cement mortar with clay tile1/reinforced concrete
A large number of masonry structures are hybrid in nature (Figures 11-17 through 11-21). For
instance, in a typical two-story construction, the older first story walls may have been constructed
in random rubble stone masonry with mud mortar, but the newer extension of the upper story may
be in brick masonry laid in cement mortar with reinforced concrete slabs for floors and roof. Such
hybrid construction sustained severe damage in the weaker lower story. Sometimes, the opposite
has also been observed, where weak thin walls and poor cement mortar in the upper stories led
Clay tiles are used as covering material and supported on a wooden truss-purlin system or on a
framework of wooden joists.
Masonry Structures 192
Figure 11-10. Random rubble stone masonry in Figure 11-11. Stone masonry in cement mortar
mud mortar with tile roof. with tile roof.
Figure 11-12. Clay brick masonry in mud mortar Figure 11-13. Coursed stone masonry in cement
with tile roof. mortar with RC slab roof.
Figure 11-14. Random rubble stone masonry in Figure 11-15. Clay brick masonry in cement
cement mortar with RC slab roof. mortar with RC slab roof.
Masonry Structures 193
Figure 11-16. Cement block masonry in cement Figure 11-17. Improper connection between
mortar with RC slab roof. walls (Samakhyali village).
Figure 11-18. Poor shear strength of stone Figure 11-19. Loosely formed roof with
masonry in the lower story of structure with lintel Mangalore tiles (Bhuj) led to serious damage/
bands (Bhuj). collapse of structures.
Figure 11-20. This 3-story load-bearing Figure 11-21. The first story of this masonry
construction (Gandhidham) had exterior walls of structure in Anjar, constructed of random
stone masonry and interior walls of hollow cement rubble stone masonry in lime mortar, collapsed
blocks. Lintel and plinth bands were provided. completely. The second story, of brick masonry
This structure performed well, while its adjoining with cement mortar, experienced minimal
5-story reinforced concrete frame buildings damage.
sustained serious damages and collapses.
Masonry Structures 194
Early construction practice in earthquake-prone areas of India did include lintel bands. Indeed,
they have been used in the Kachchh region for over 50 years. Early construction spearheaded by
governmental agencies like the MES, Indian Railways and Kandla Port Trust, and subsequently joined
by the SRC Limited in the early 1950s included the practice of providing lintel bands in their masonry
construction. The lintel bands were made of wood, reinforced concrete with cement/lime mortar
(Figure 11-22), or even specially shaped hollow cement blocks for placing horizontal reinforcement.
However, with time, and as the trauma of a big earthquake in 1956 was forgotten, some of these
good practices were slowly lost, and most masonry structures were built with no lintel bands.
Over time, an interesting lintel feature was introduced in some masonry construction of the
region. Owners of houses used reinforced concrete loft slabs inside the rooms at lintel levels for
providing storage space in the house. In many cases, if the house is small, the loft is provided
throughout the house. In such instances, these relatively thin reinforced concrete slab strips act
as lintel bands (Figure 11-23). In some cases, no lintel band is provided, but the exterior façade
is plastered to imitate a lintel band.
Figure 11-22. Reinforced
concrete band at lintel level.
Figure 11-23. Improvisation of
loft slabs as lintel band.
Masonry Structures 195
Masonry construction in the region was often built incrementally, and hence the final structural
configuration is not always known at the start of the construction. Subsequent additions were
driven by functional needs, and the structural consequences of these additions were not understood.
Consequently, almost all masonry construction in the affected area is highly irregular in structural
configuration. The geometry, size, and shape are often disproportionate and vary abruptly, leading
to vertical and horizontal offsets. Loosely formed roofs, like the Mangalore (a south Indian city
on the south-west coast of India), tile roofs do not provide good diaphragm action for proper
distribution of lateral loads to walls. On the other hand, reinforced concrete slabs achieve good
diaphragm action. In buildings with reinforced concrete slabs and configuration irregularities,
torsional response was generated, and they performed poorly as they failed to resist the increased
torsional shear stresses.
Foundations in masonry construction have been constructed fairly consistently throughout the
Kachchh region. The topsoil consists of 300-400 mm thick black cotton soil/black silty soil/soft
creek soil. Underlying this layer is murrum soil (weathered rock), which may be either hard or
soft. Usually, shallow trenches are dug and strip foundations are used. After the trench is dug, a
lean cement concrete is laid over the soil. Large granite boulders are hand-broken to a size of 40
mm and less, and used as aggregates in this cement concrete. In the slab concrete, 20 mm, 12 mm
and/or 6.25 mm graded aggregates are used. Black granite stone blocks of random shape and of
largest dimension up to 450 mm are used in the random rubble plinth masonry.
In usual masonry buildings in cities and major towns, a 1.2 m-1.5 m deep 0.9 m-1.2 m wide
trench is dug (Figure 11-24a). Then, a 150 mm thick 1:5:10 cement concrete made of 40 mm
size hand-broken coarse aggregate is placed on the murrum soil. Next, the plinth masonry is
constructed over this cement concrete in two lifts each of 0.7 m height; the first lift is 600 mm
wide and the second 450 mm. Uncoursed, randomly cut black basalt/trap stones are used in the
masonry with 1:6 cement mortar. A 100-150 mm thick damp-proof course-cum-plinth band is
placed on top of the plinth masonry. The band is made in 1:2:4 nominal mix concrete with cement
and 20 mm coarse aggregates, and has 4 bars of 12 mm diameter high yield strength deformed
bars (fy=415MPa) as longitudinal steel with 6 mm diameter mild steel bars (fy=250MPa) at 150
mm centers as ties. When it is treated only as a damp-proof course, no reinforcements are required
by the government specifications.
In the rural setting, the above procedure of foundation construction is severely simplified
(Figure 11-24b). A 600 mm wide trench is cut in the ground up to a depth equal to the thickness
of the black topsoil. The trench is stopped at the first sign of the weathered rock or the soft/hard
murrum soil. Only rarely is the 150 mm thick 1:5:10 lean cement concrete layer discussed earlier
placed. Even when it is, the base material at the founding level is only random rubble broken stone
in mud/lime mortar. The trench is filled with uncoursed trap stones. Dry, hand-mixed 1:6 cement
mortar is placed over these random stones and watered to send the mortar into the voids between
the stones. The plinth masonry is stopped 150 mm above the ground level. No damp-proof course
band is provided in this type of construction.
The preparation of the plinth masonry has a few special features. After the trench is dug and
the 150 mm thick lean concrete is placed (Figure 11-25), the largest granite stones are picked
and their planar faces are made vertical and flush with outside/inside of the wall (Figure 11-26).
Then, smaller rubble stones and cement mortar are placed in the voids. The largest stones do not
always cross the full width of the foundation and usually a distinct vertical layer of small rubble
and cement mortar is present in the vertical mid-thickness of the wall. Since the surface of the
Masonry Structures 196
Figure 11-24. Typical foundation specifications for masonry construction in the Kachchh region:
a. Formal version adopted in better construction, and
b. Basic version adopted in poor quality construction.
Figure 11-25. Shallow trenching. Figure 11-26. Large uncoursed granite blocks
placed from both sides; a central weak plane is
Figure 11-27. Inside foundation surface pointed, Figure 11-28. Masonry in large-block sandstone
outside surface left unfinished. under construction. A plinth band is provided.
Masonry Structures 197
granite stone is nonporous and smooth, the cement mortar does not bond effectively with the stone.
This, coupled with the vertical mid-layer of the wall mentioned above, invites the masonry to
split into two vertical wythes. Often, the vertical surfaces of the plinth masonry are not pointed.
In most cases, only one of them is pointed. For example, if a plinth masonry is for a residential
unit, only the outside surface is pointed. When the inside surface is required for access and not
the outside, as in the case of the foundation of a weighbridge, (where trucks are weighed along
the highway), the inside surface is pointed and the outside face is left unfinished (Figure 11-27).
In government construction, and in construction by qualified engineers, a damp-proof course is
often provided at plinth level (Figure 11-28). Rarely is a plinth band also provided.
CONSTRUCTION OF MASONRY WALLS
The procedure described above for the foundation masonry is also adopted for walls with
random rubble masonry in mud or cement mortar. Unlike in the plinth masonry, these walls are
pointed on both faces. In masonry construction using cement blocks, the plinth masonry is done
in either granite stone, or in solid cement blocks.
The construction materials of the region have characteristics that have led to special construction
strategies. For instance, black granite stone is commonly available in the Kachchh region, but is
heavy. Lifting large granite blocks for masonry construction at higher elevations is difficult. In
addition, a pink variety of sandstone is locally available; it is lighter than granite, but is weaker
in compressive strength. A practice has evolved in the region wherein the plinth masonry is made
in the heavy granite and the superstructure wall masonry in the light sandstone.
Four different types of masonry units are employed for making walls in the Kachchh region,
as described below.
Random-rubble stone masonry with mud/lime/cement mortar
Walls are made with undressed granite stone of different degrees of weathering and up to a
maximum dimension of 400 mm in low rise 1-2 story buildings, and up to 600 mm in taller ones.
Some of the older construction with mud mortar has wall thickness of about 600 mm even in 1- and
2-story buildings. These thick walls are constructed with one mason working on each side of the
wall and placing stones to create even surfaces on the exterior faces. This results in walls that have
two predominant vertical layers or wythes. With maximum wall thickness of 600 mm and the largest
dimension of stones as 400 mm, no stone covers the full width of the wall and the much-needed
interlocking between the two vertical layers is absent. This problem of lack of integrity within the
wythes of walls is less severe when wall thickness is about 400 mm or less. Depending on the level
of weathering, the surface characteristics, and therefore their bond with the mortar, vary.
Small/large block semi-dressed/dressed stones in mud/lime/cement mortar
Quarried sandstone or, in some instances, locally available weathered lateritic rock is used. In
monumental structures, some private buildings, and many government buildings, semi-dressed
(i.e., without smooth polishing of the outer surface) stones are used. The normal practice across
India is to use stones with the largest dimension of about 400 mm. However, construction practice
in the Kachchh region offers a special construction style. Semi-dressed stones of size about 600
mm × 400 mm × 250 mm are employed in stone masonry (Figure 11-29). Due to this large size
of units, the thickness of the mortar usually required between the stones is as large as 80 mm.
In such construction, only a few of these large-block stones are required compared to small-
block masonry. Under strong seismic shaking, the out-of-plane dislodging of one stone due to
either out-of-plumb wall or out-of-plane seismic shaking of the wall can lead to the collapse of
a significant portion of the large-block masonry above, jeopardizing the safety and stability of
Masonry Structures 198
Figure 11-29. Stone block
units used in masonry
construction in the Kachchh
region. The tape is held out
to 30 cm.
the entire building. Small-block stones of about 400 mm × 230 mm × 150 mm are also used.
Where provided, pilasters in the long and slender compound walls seemed to have contributed
significant out-of-plane stability.
Sandstone available in the Kachchh region is of the pink variety. This stone, though lighter
than the granite/trap stone, is still heavy for use in wall masonry construction. For this reason,
another variety of yellow sandstone is brought from Junagadh in the Saurashtra region. This stone
is much lighter and can be cut nearly to brick sizes for ease of handling. The yellow stone is also
preferred for the aesthetics of its bright color.
Burnt clay bricks in mud/cement mortar
In recent times, this type of construction has become increasingly common in the Kachchh
region, particularly in urban areas. Consequently, countryside kilns have grown and are producing
burnt clay bricks of standard size 230 mm × 115 mm × 75 mm even though the soil is not suitable
for making good quality burnt clay bricks. The quality of these bricks is poor and highly variable,
even within the same batch. For this reason, bricks are often brought from Ahmedabad and other
distant locations. These burnt clay bricks have a frog on one surface, and are used with either mud
mortar or cement mortar, depending on the economic considerations of the user. Standard wall
thickness of 230 mm is very common in most buildings, even in reinforced concrete frame buildings.
However, in two and three story buildings, use of one-and-half brick walls is also observed. There
are also instances of the use of 115 mm (half-brick length thick) walls in single-story buildings.
This is a matter of serious structural concern, particularly in the severe Seismic Zone V.
Solid/hollow cement blocks in cement mortar
Both solid (Figure 11-30) and hollow cement blocks with up to three cells (Figure 11-31) of
varied sizes and shapes have been in use since 1950, when a Besser Plant was commissioned at
Adipur. Over 5,000 buildings of varied sizes and functional utility with lintel bands incorporated
into the construction were built with hollow cement blocks by the SRC Limited. Composition and
quality control of the manufacture of cement blocks have varied significantly over the years. Around
Masonry Structures 199
Figure 11-30. Solid
Figure 11-31 Figure 11-32 Figure 11-33
Figures 11-31, 11-32, and 11-33. Three types of hollow cement blocks.
the same time, major government agencies like Indian Railways, the Kandla Port Trust, and the
Military Engineering Service also extensively used plinth and/or lintel bands. The hollow blocks
permitted vertical reinforcement to be carried through the wall. In some instances, these vertical
reinforcements were not anchored into the reinforced concrete slab in order to allow for thermal
expansion/contraction of the slab. These buildings, built in the 1950s with hollow cement blocks,
performed very well during the 1956 Anjar and 2001 Bhuj earthquakes. However, local engineers
now recognize that the vertical reinforcement should be anchored into the slab to provide a positive
connection for transfer of forces and ensure against sliding of the reinforced concrete slab.
Hollow cement blocks were made of different compositions to give them different finishes.
Currently, the hollow blocks construction is waning due to lack of quality in manufacturing. The
compressive strength of these blocks largely depends on the level of compaction achieved after
placing the concrete mix in the steel molds. The older Besser machine used table vibrations and
pressure for compaction, while the locally improvised machines for cement block construction
depend on nominal table vibration and hand compaction. Some of the block-making machines
recently manufactured in India are small and portable and provide reasonable compaction using
table vibration and pressure.
In urban areas, the availability of industrial by-products, such as fly ash, has led to the growth
Masonry Structures 200
Figure 11-34. Fly ash bricks have begun to
gain popularity as a building material.
of cement-based masonry units (Figure 11-34). The fly ash brick masonry blocks are handcast by
applying a little pressure with a hand tool. Both solid and hollow units are manufactured at a price
competitive to that of the traditional burnt clay bricks. The standard units are 200 mm × 100 mm
× 75 mm. Some manufacturers make 230 mm × 100 mm × 75 mm blocks whose lengths match
the transverse dimension of the 230 mm columns commonly adopted, which is the thickness of
traditional burnt clay brick walls. These cement block units have good thermal characteristics,
and in the case of hollow blocks, also lightweight. The hollow bricks also offer the possibility of
passing vertical reinforcement through the hollows, as required in severe seismic zones.
Table 11-2 presents an overall comparison of the various masonry units in use in the Kachchh
Masonry walls of hollow block construction follow a relatively simple sequence. The plinth
masonry is prepared and the damp-proof course is laid (Figure 11-28). In cases where a plinth
band is also intended, special channel unit blocks are placed (Figures 11-35 and 11-36) to act as
the formwork for the reinforcement of the plinth band (Figure 11-37). The reinforcement cage is
placed and concrete poured in-situ. Vertical reinforcements at wall corners are also introduced
in the plinth band and passed through the hollow blocks in wall corners (Figure 11-38). Special
blocks are also available for introducing the anchors and fasteners for the window and door frames
ROOFING MATERIAL AND ROOF CONSTRUCTION
Older roof construction is mostly sloped or pitched, and has wooden truss roofs with purlins
supporting the clay tiles (Figure 11-40). Locally available wood logs of rounded cross-section are
used, often as main members without any shaping. In most instances, the trusses are not complete
with bottom tie members, and one horizontal member (of about 100-150 mm diameter) runs across
the length of a room at the ridge level. Two types of roofs are usually used in the Kachchh region.
In the first, rafters (of about 100-150 mm diameter) are used. These rafters rest on a horizontal
member at the ridge level and directly on the masonry walls at the level of the eaves. Light wood
purlins and battens (of size 25 mm × 15 mm) form a grid to place the tiles (Figure 11-40a). In
the second type of roof construction, the rafters are done away with, and purlins of significant
size (up to 75-100 mm in diameter) are placed directly on the gable wall (Figure 11-40b). One or
two intermediate purlins are provided along each of the slopes. The rafter and battens are smaller
Masonry Structures 201
Table 11-2. Comparison of various masonry units used for roof construction in the Kachchh region
Building Unit MPa) Cost Comments
Sandstone 3.0 1 Good quarries are used up; lately only soft
From Junagadh variety is available; becoming expensive;
(yellow variety; high water absorption; low mortar strength
380×280×120 at Anjar; and very poor bond is achieved.
400×230×200 at Adipur)
Locally available in Bhuj
(light pink /brown variety)
Hollow cement blocks 2.8-3.5 1.25 Quality is poor (no compaction due
to lack of vibration).
Solid cement blocks 6.5-7.5 1.50 Higher strength than bricks; no homogeneity,
more cracks in walls after seismic shaking.
Large size Block is heavy: small movements for
(390×200×190) adjusting the position breaks the initial set
of the mortar around the blocks in the lower
layers due to weak mortars currently in use;
cannot be handled in wet condition thus, not
soaked before placing. Low bonding due to
lesser surface area of blocks in contact with
mortar and lesser porosity of blocks, as
compared to that of bricks. When such walls
collapse, 95% of the blocks are recoverable due
to poor bond and higher strength of blocks; in
brick walls, only 5% of bricks are recoverable.
Small size More joints and hence more homogeneous
(230×100×75) than large blocks; higher manufacturing cost.
Burnt clay bricks 3.5-4.0 1.50 Bond better with mortar than to solid cement
blocks; better insulating property; poor quality.
Basalt/trap stone At least 1.75 Fine texture on surface, and hence low bond
50.0-100.0 leading to failure of walls in two wythes; very
heavy; used commonly in foundations and in
masonry up to plinth level only.
Fly ash bricks 6.7-7.5 1.60 Lighter than bricks and blocks; very high water
absorption (20-32%), (Permissible Absorption
Brick Class - I<15%; II<22%; III<32%); eco-
friendly; large sulfur content (since made from
lignite-based ash) implies chemical corrosion.
Notes: Compressive strength is computed over unit plan area of wall.
The cost index noted above includes only the cost of manufacture and supply of the masonry unit,
and not of the masonry.
Masonry Structures 202
Figure 11-35. Special channel bricks facilitate Figure 11-36. Cement channel bricks.
placement of reinforcement bar.
Figure 11-37. Plinth band reinforcement. Figure 11-38. Corner reinforcement.
Figure 11-39. Special concrete
blocks are used to anchor door and
Masonry Structures 203
in size (25 mm × 15 mm) and are simply nailed or tied with coir rope to the main rafters. Thus,
there is no positive anchorage of the roof to the walls, other than through bearing of the rafters
or purlins along the gable and other walls.
Roof tiles are usually of two types:
• Mangalore Tiles. Mangalore tile is 400 mm × 230 mm in plan, about 25 mm thick, and
weighs about 5 kg (Figure 11-41). Each tile overlaps with the adjacent ones by 30 mm
along the width and about 60 mm along the length. The loading from such roofs, including
the weight of battens, purlins and rafters, is about 1kN/m2. Pitched roofs with Mangalore
tiles are the most common roofing systems employed in the rural areas of Kachchh. No
trusses are used in the roof; a grid of rafters and battens are used and the tiles rest on them.
A heavy purlin runs across the length of the room at the ridge level. The cross-sections
of wooden rafters are much smaller than those of the purlins, and the battens are even
smaller. The purlins and rafters merely rest on the top surface of the walls of the room; no
positive anchorages are used (Figure 11-42). Mangalore tile roofs can be very heavy and
draw large inertial forces. Since they are loosely formed, they are easily displaced (Figure
• Slit Tube Tiles. Slit-tube tile roofs are also used in the region (Figure 11-44). These are
even more loosely formed, and also require an impervious layer of soil/sheeting to prevent
rainwater from seeping in. Unfortunately, this layer causes the sliding of the tiles easily.
Relative performance of these two roofing systems indicates the former to be more efficient.
In semi-rural or urban areas, corrugated galvanized iron/asbestos/tin sheet roofs are also used.
Slit-tube clay tile is 150 mm long, 75 mm in diameter and 6-10 mm thick. Each piece weighs about
0.3-0.4 kg. The overlap along the length at the two ends is about 30 mm. Such roofs also impose
a dead load of about 1kN/m2. Both Mangalore and slit-tube roofing systems require specially
shaped coping element to cover the ridgeline of the pitched roofs.
Other roofing materials, such as corrugated sheets made of galvanized iron/asbestos/tin and
fastened to wood or steel trusses, are common in better quality construction. Today, masonry
dwellings also have reinforced concrete slab roofs. The slab thickness varies from 75 mm to 125
mm. Reinforcement is nominal; usually 6 mm diameter mild steel (smooth) bars or 10 mm/12
Figure 11-40. Pitched roofs constructed in the Kachchh region are made of wooden trusses that are
often not completed – there is no bottom chord in these trusses. There are two basic forms of the
roofs adopted. a.) Roof with heavy rafters and b.) Roof with heavy intermediate purlins. Roof tiles are
supported by battens and purlins of small cross-sections laid over these main rafters or purlins.
Masonry Structures 204
Figure 11-41. Mangalore roof tile. Figure 11-42. Roof rests on top of walls.
Figure 11-43. Mangalore tiles slid off this roof. Figure 11-44. Slit-tube tile roof. Each tile weighs
mm diameter high-strength deformed steel bars at 150 to 250 mm centers along each principal
direction. The concrete is hand mixed based on volume batching, and usually of grade M15 (i.e.,
28-day characteristic 150 mm cube compressive strength of 15 MPa). Because of poor formwork,
the required cover to reinforcement may not be present uniformly throughout the slab. In many
instances, the reinforcement bars are seen on the soffit of the slab. The performance of these
roofing systems under seismic shaking has been well established. Lighter and stiff-in-plane roofs
performed well, while the heavy and loosely formed ones fared poorly.
GUIDELINES AND INDIAN STANDARDS
The structural design of unreinforced load bearing/non-load bearing masonry walls made of
various masonry types is governed by the masonry code (IS:1905-1987). The Indian Standard
masonry code specifies materials to be used, maximum permissible stresses, and methods of design.
However, selection of materials and special features of design and construction of earthquake-
resistant masonry buildings are given in another Indian Standard (IS:4326-1976).
Masonry Structures 205
The International Association for Earthquake Engineering (IAEE) published a manual in
English for nonengineered construction (IAEE, 1986). This publication reviews the structural
performance during strong earthquake shaking of masonry, earthen, stone and wooden buildings, and
nonengineered reinforced concrete construction. It outlines general concepts in earthquake-resistant
design of such structures. Further, it gives guidelines for repair, restoration, and strengthening of
reinforced concrete structures. This compilation of the basic rules of thumb has been reprinted in
India by the Indian Society of Earthquake Technology (ISET), and priced nominally (ISET, 1989).
However, even this document did not receive wide audience, as English is not the native language
in India, and the IAEE guidelines did not have the formal recognition of enforcing agencies.
The Bureau of Indian Standards (New Delhi) has incorporated some contents of the IAEE
manual in Indian Standard Guidelines. Two separate publications emerged, one for Earthen
Buildings (IS:13827-1993) and another for Low-Strength Masonry Buildings (IS:13828-1993),
which covered both brick and stone masonry construction. These publications gave formal
recognition to the practice of building earthquake resistance into a greater variety of dwellings.
Even though Indian Standards are generally not mandatory in India, they represent documents
of authenticated information. In 1999, the Bureau of Indian Standards published the bilingual
(English and Hindi) version of these two standards (IS:13827-1999; IS:13828-1999) to increase
their usage. The practice of earthquake-resistant construction would be enhanced if these Indian
Standards also become available in regional languages.
INDIAN STANDARD FOR UNREINFORCED MASONRY (IS:1905-1987)
The masonry code gives recommendations for the design of unreinforced load-bearing masonry
walls constructed using solid/perforated burnt clay bricks, sand-lime bricks, stones, concrete
blocks, lime based blocks, and burnt clay hollow blocks. As per this code, no special provisions
are necessary for buildings constructed in Seismic Zones I and II. However, special features are
applicable for construction of earthquake-resistant masonry buildings in Seismic Zones III, IV,
and V (IS:4326). These specifications were not followed in structures in the affected area, a region
in Seismic Zone V.
Based on their nominal mix proportions, the masonry code classifies mortars made from cement,
lime, Pozzolana and sand into six grades, namely high (H1, H2), medium (M1, M2) and low (L1,
L2). These mortars are required to satisfy the minimum compressive strength requirements for
use in masonry work. Also, the code requires masonry units to adhere to the strength requirements
given in relevant Indian Standards for brick units (burnt clay or sand lime), stones, and concrete
blocks (solid and hollow). The use of a wide range of quality of mortars and masonry units noted
in the postearthquake reconnaissance surveys indicate that material tests are usually not performed
and the above specifications on the mortar and masonry units are not enforced.
The code specifies a number of stability-related requirements to be incorporated in the planning
of the geometry of the structure and choosing the wall thickness. The code limits the slenderness
ratio (h/t or l/t), where h and l are the effective height and effective length of the wall. For walls
in cement mortar, the ratio is limited to 27, and for walls in lime mortar up to 2 stories to 20, and
for structures taller than 2 stories, the ratio is limited to 13. The standard requires that buildings of
typical story heights of 3.2 m, walls in cement mortar are at least 120 mm thick, and those in lime
mortar are at least 160 mm (in buildings up to 2 stories) or 250 mm (in buildings with more than
2 stories). These thicknesses are independent of that of plaster. Provisions for estimating effective
thickness, length and height of walls are available for various end conditions designed in practice.
These provisions seem to be valid for the single story structures built in the Kachchh district.
Masonry Structures 206
In design, the building is required to be analyzed as a whole as per accepted principles of
mechanics. The code requires that the components of the structure be made capable of resisting
the most adverse combination of loads expected. Provisions for estimating the capacity of
individual components are given in the code. The allowable stress method of design is adopted.
Permissible stresses are specified and procedures for calculation of those in compression and
shear are specified. Thus, a quantitative procedure is available for design of masonry buildings.
Unfortunately, quantitative design of masonry buildings is not performed, in general, for any
classes of structures.
INDIAN STANDARD FOR EARTHQUAKE DESIGN AND
CONSTRUCTION OF BUILDINGS (IS:4326-1993)
Indian Standard IS:4326-1993 deals with selection of materials, special features of design and
construction for earthquake-resistant buildings, including masonry construction using rectangular
masonry units, timber construction and buildings with prefabricated flooring/roofing elements.
General principles are provided to encourage the construction of buildings with low mass, integral
construction including suspended and projecting parts, simple geometric shapes, and ductility.
Attention is drawn to special features of building design and construction. For example, when
joints are unavoidable in buildings, the code specifies minimum values of separation gaps required
between adjoining buildings as given in Table 11-3.
IS:4326-1993 classifies buildings into five categories A, B, C, D and E, depending on the value
of the design seismic coefficient αh, given by the product βlα0. Here, β is the soil-foundation
system factor (1.0-1.5, depending on soil-type and foundation-type), I is the importance factor (1.5
for important structures and 1.0 for all others), and αh is the basic horizontal seismic coefficient
(0.04, 0.05 and 0.08 for Seismic Zones III, IV and V, respectively). αh can be interpreted as design
seismic base shear per unit seismic weight of the structure. Category E is the most severe with
αh ≤ 0.12 and category A, the least severe with 0.04 ≤ αh ≤ 0.05. For buildings in each category,
the code specifies the following: mortar mix, the size and position of openings, and the details
of earthquake-resistant features like bands, vertical reinforcements, and plan bracings at roof
INDIAN STANDARD FOR EARTHEN CONSTRUCTION (IS:13827-1993)
This Indian Standard covers three types of earthen construction: hand-formed layered
construction, block/adobe construction, and rammed earth construction. Each method is presented
in detail below. For seismic areas, IS:13827-1993 provides additional recommendations. The
Table 11-3. Minimum separation gap to be provided between adjoining buildings with design
horizontal seismic coefficient αh of 0.12 as specified in IS:4326-1993.
Type of Construction Minimum Separation (mm)
Box system or frames with shear walls Min (25; 15n)
Moment resisting reinforced concrete frame Min (25; 20n)
Moment resisting steel frame 30n
Note: n is the number of stories in the building.
Masonry Structures 207
Standard prohibits earthen construction in Seismic Zones IV and V, and restricts the height of
such construction to one story in Seismic Zone III. Also, this type of construction is to be avoided
in high water table sites, particularly in Seismic Zones IV and V.
Roofs are required to be light, well connected within, and adequately tied to the walls. Trussed
roofs are preferred over sloping roofs with just rafters or A-type frames. Heavy roofs consisting
of wood joists plus earth toppings are prohibited in Seismic Zones IV and V. Tiled/slate roofs are
also considered to be vulnerable and are to be avoided in Seismic Zones IV and V. The Standard
suggests that the rafters used in the roof be rested on longitudinal wooden elements along the
walls to enable a uniform distribution of forces from the roof to the walls. Roof beams or rafters
are to be avoided over openings. If these cannot be avoided, lintels over such openings shall be
reinforced with additional lumber.
The unsupported length of walls between cross walls is required to be less than the smaller
of 10t or 64t2/h, where t is the thickness of the wall and h is its height. If walls must be longer
than the above limits, they are required to be strengthened by buttresses in between. Further, the
height of the wall is required to be less than 8 times its thickness. The upper limit on the size of
the openings in walls is specified in absolute dimension as 1.2 m; at least 1.2 m away from the
corners. The amount of openings is restricted to be 33 percent of the wall length in Seismic Zone
V and 40 percent in Seismic Zones III and IV. Further, the walls are required to be strengthened
with the following features:
• In dwellings situated in Seismic Zones III, IV and V, the walls are to be tied together with
at least two bands, one at the lintel level and another at the roof level. The bands may be
made of wood. When pilasters or buttresses are provided, the bands have to pass over them
• In Seismic Zone V, walls have to be reinforced along the vertical direction with cane or
bamboo sticks. These vertical elements have to be tied together with horizontal pieces of
bamboo/cane and also anchored in the two bands at the lintel and roof levels.
The foundation of such construction is usually strip foundations running along the length of
the walls. These strips are required to be founded at least 400 mm below ground, and to have a
width of twice the wall thickness. Foundation materials are required to be stronger than those used
in the walls. For instance, foundation masonry fired bricks or stones, with lean cement concrete
of 1:5:10 or lime concrete of 1:4:8, is suggested by the Standard. It is also recommended that the
wall above the foundation up to the plinth be made in the same stronger material recommended
for the foundation. The plinth is required to be at least 300 mm above ground. The Standard also
suggests that a thick plastic sheet be used to prevent water from seeping upwards through the
walls, in addition to requiring a water drain to be built around the outside of the wall to keep the
water away from the dwelling.
INDIAN STANDARD FOR LOW-STRENGTH CONSTRUCTION (IS:13828-1993)
The provisions of this Standard are applicable for brick and random rubble stone masonry
construction in Seismic Zones III, IV, and V. For those in Seismic Zones I and II, these provisions
are not considered necessary. This Standard refers to low-strength masonry. It clarifies that buildings
constructed in accordance with these guidelines are not totally free from collapse under seismic
shaking intensities of VIII and IX. However, inclusion of the special design and construction
features of the Standard reduces the likelihood of structural collapse.
Again, this standard also classifies buildings in Seismic Zones III, IV, and V into five categories
– A, B, C, D, and E – as in IS:4326. Buildings in category E and important buildings (with ) are
prohibited from using low-strength masonry. However, for buildings in other categories, the Standard
makes specific recommendations on the structural configuration and special earthquake-resistant
features to be built into them. For example, the limitation on the building height is specified as
Masonry Structures 208
indicated in Table 11-4, with story heights not exceeding 3 m and spans of walls between cross-
walls limited to 5 m. Wall thickness is required to be restricted to within 450 mm. The maximum
size and preferred location of openings is identified. Brick masonry construction shall be made
with bricks of compressive strength not less than 3.5MPa. Strength of bricks and wall thickness
are to be chosen depending on the height of the building.
Indian Standards suggest special seismic strengthening to increase the earthquake resistance
of low-strength masonry buildings, including:
1. Through-stones or bond elements in thick walls.
2. Limitations on size and location of openings in walls.
3. Lintel band over all internal and external walls except partition walls.
4. Roof band (except when the roof is made of reinforced concrete) when roof is flat and
gable bands when roof is pitched, resting over the full width of the wall.
5. Vertical reinforcing steel at corners and junctions of walls.
6. In-plan bracing of flexible roof system.
7. Plinth band, where strip footings are made of masonry (other than reinforced concrete or
reinforced masonry) and soil is soft or of uneven properties.
IS:13828-1993 provides empirical details of each of the above seismic strengthening
arrangements for direct implementation in the field during construction. The above seismic
strengthening arrangements are required to be built into buildings depending on their category
(i.e., A, B, C, or D) and number of stories.
OTHER PUBLICATIONS AND BOOKLETS APPLICABLE TO
STRUCTURES IN THE BHUJ AREA
The publication Vernacular Housing in Seismic Zones of India reviews the seismic vulnerability
of masonry construction in India in 1984 (I-UNM 1984). The report is based on a field survey
and was published in 1984. It lists the status of various aspects of masonry structures, such as
Table 11-4. Limitations on the number of stories to be constructed in low-strength
masonry, as specified in IS:13828-1993.
Building Type A B C D
Brick Masonry Construction
Flat roof 3 3 3 2
Pitched roof (including attic) 2 2 2 1
Stone Masonry Construction
• Lime-sand or mud mortar 2 2 1 1
• Cement mortar (1:6) 3 3 2 2
Pitched roof (including attic)
• Lime-sand or mud mortar 1 1 1 1
• Cement mortar (1:6) 2 2 2 2
Masonry Structures 209
structural integrity and configuration. It identifies deficiencies in masonry structures and suggests
measures to overcome those deficiencies. The detailed review of stone masonry houses in the
Bhuj region identified the following general characteristics:
• Poor roof design: heavy, loosely formed and not properly anchored to the walls
• Weak walls: thick random rubble stone walls in mud mortar with weak strength and
connections between the adjoining walls
• Reasonable foundation design: overall geometry and balance of the structure, quality of
workmanship, and size and location of openings.
Some academic organizations and nongovernmental organizations in India have also published
useful information on earthquake-resistant masonry construction. The Rajiv Gandhi Foundation
in New Delhi, in association with the University of Roorkee, Roorkee, published a booklet on
“Do’s and Don’ts for Protection” against the earthquake problem. The booklet was published in
two languages—in Hindi (RGF 1994a) and English (RGF 1994b). The Rajiv Gandhi Foundation
published another booklet on earthquake-resistant house construction (RGF 1994c), which is a
good beginning towards taking the subject of earthquake-resistant structures directly to the common
man. Similarly, another agency, Lok Vigyan Santhan, Dehra Dun, also published a booklet in
Hindi on earthquake-resistant house construction (LVS 1995). This booklet is one in a series of
booklets prepared for use by ordinary homeowners, who may not always get an engineer to help
them decide how to construct their house. The above are but a few of the examples of efforts
to generate awareness and provide information about earthquake-resistant construction to the
broadest possible audience.
The 2001 Bhuj earthquake provides opportunity to capitalize on and push the mass education of the
people of India living in seismically active areas towards building safer and less vulnerable houses.
TYPICAL STRUCTURAL DAMAGE
The most elementary of masonry construction is random rubble stone (granite) masonry in mud
mortar. The wood used in the roofing is not formally cut and shaped. Earthquake-resistant features
are not built into this system. There are no connections between the walls, or between the walls and
roof. Housing of this type, found primarily in economically weaker sections of the society, performed
abysmally during the 2001 Bhuj earthquake. While these low-strength masonry units were high on
fulfilling functional needs, they were structurally unsuitable to resist lateral seismic loads because of
the building materials used. In this type of construction, little attention is paid to the details that make
the roof and walls act together as a single entity. For instance, three months after the earthquake
destroyed the original structure, it was being rebuilt using the same rubble in reconstruction. Again,
no lintel band is being provided, illustrating that knowledge of earthquake-resistant construction
is not being implemented consistently, even after this earthquake (Figure 11-45).
The unusually large size (up to 600 mm) pink sandstone masonry units and mud mortar (up to
75 mm thickness) used in making two-story residential buildings resulted in brittle performance
(Figure 11-46). Pink sandstone is lighter than granite, readily available, and hence very popular
in the Kachchh region. Owing to the coarse shapes of the stones, the thickness of the mud mortar
required for leveling is sometimes as large as 8 cm (Figure 11-47). Such large masonry blocks
with unusually large mortar thickness of a basically weak mortar material (mud) resulted in
very poor performance of a large number of such structures in Bhuj. Heavy purlins carrying the
weight of the roof cause stress concentration on the walls at the support points. The stone-mud
walls sustained severe cracking at these locations (Figure 11-48). Walls built with large stones
and no through-stones separated into wythes impairing the vertical load-carrying capacity. Traces
of traditional wisdom were seen in some structures that survived the shaking with little damage,
Masonry Structures 210
where lintel and post system provided lateral resistance (Figure 11-49). This practice may have
come from the construction of monumental/heritage construction in the area that used wood frame
in a significant way to counter seismic forces.
Older construction used a large amount of wood in the post and lintel system, thereby providing
some lateral resistance to the inherently weak stone (granite) masonry in mud mortar.
Semi-dressed/dressed stone masonry in cement mortar in general sustained lesser damage than
random rubble in mud mortar construction. Structures with tall gable walls faced out-of-plane
stability problems. Single story construction with semi-dressed sandstone is common. In the
majority of cases, lintel bands are not provided in the Kachchh region. These structures sustained
only minor damage, such as fine shear cracks in stiff walls. Pink sandstones cut to 450 mm largest
dimension were used in the construction of some residential units (Figure 11-50). The plinth in
such construction is usually in random rubble granite stone masonry in cement mortar. The strength
of these sandstone masonry units can be comparable to that of cement mortar sometimes. In such
cases, the shear cracks in walls ran through masonry blocks.
Figure 11-45. Random rubble from the original Figure 11-46. Pink sandstone of up to 600 mm
(collapsed) structure is being used to rebuild this in size was used in construction of these two-
unreinforced masonry house. story housing units.
Figure 11-47. Mud mortar is sometimes as thick Figure 11-48. Walls built with large stones
as 8 cm. The tape is held out by 30 cm. and no through-stones separated into wythes
impairing the vertical load-carrying capacity.
Masonry Structures 211
Figure 11-49. Older construction used a large Figure 11-50. This construction, underway in
amount of wood in the post and lintel system, Bhuj at the time of the earthquake, provides a
thereby providing some lateral resistance to the plinth band, but not a lintel band.
inherently weak stone (granite) masonry in mud
Over the years, the Indian Railways and the Kandla Port Trust have built good engineering
practices into their construction. The single-story and two-story random rubble masonry residential
units in cement mortar with reinforced concrete slab roofs at the Indian Railways residential colony
in Gandhidham have plinth and lintel bands. Pointing is done on the outside and plastering on the
inside. The reinforced concrete slab roof is simply rested on the walls. The single-story structures
performed very well. The wall-roof interface had nominal sliding and separation, and the short
walls between the plinth and lintel bands sustained shear cracks (Figure 11-51). However, the two
story residential units suffered damage such as sliding of service water tanks, collapse of parapets,
and severe damage to stair towers. Dressed sandstone masonry in cement mortar with plinth and
lintel bands was used in single-story row housing at the Kandla Port Trust campus. Only minor
cracks were seen in those structures.
A good percentage of the recent construction in the Kachchh region is burnt clay brick masonry
in cement mortar. These structures showed a full range of performances, depending on the level of
earthquake-resistant features built into them. Structures without lintel bands, or with discontinuous
lintel bands, performed very poorly. Construction with lintel bands performed well. Unconfined
masonry piers sustained damage.
The first hollow cement block manufacturing plant was established in the 1950s, and today
cement block construction is common throughout the Kachchh region. Cement blocks offer lower
lateral resistance than does burnt clay masonry. Offices, academic, and residential buildings in
the Kachchh region are built of cement block construction (Figures 11-52 and 11-53). The main
features of these buildings include lintel and plinth bands, and vertical reinforcement at wall
corners. Hollow cement block construction without plinth and lintel bands performed poorly
Collapse of hollow block masonry structures was not observed, though they did sustain shear
cracks and sliding along masonry courses. Special hollow cement blocks for construction of columns
encouraged construction of multistory buildings (Figures 11-55 through 11-57). A major problem with
the hollow cement blocks is their durability. Vertical shearing off of the hollow cement block wall
into two wythes and the partial collapse of the wall (Figure 11-58), suggests that excessive weathering
of outer layer may have led to the falling off of the outer wythe of the hollow block wall.
Masonry Structures 212
Due to falling quality control in the manufacture of hollow block units, their low compressive
strength, and the increasing popularity of fly ash-based cement blocks, solid cement blocks were
introduced over the past two decades. However, unlike their hollow counterparts, these units are
heavy and cannot be handled comfortably. They have smooth surface characteristics that create
a poor bond with the cement mortar. Solid cement blocks tend to have flat surface without the
key that is present in standard burnt clay bricks. Their use in tall walls therefore makes them
particularly vulnerable in the out-of-plane direction.
Consequently, structures with solid cement block structures did not fare too well. Collapse of
the roof of a two-story building under construction (Figure 11-59), and of a warehouse building
(Figure 11-60) is attributed to the lack of bands to hold the walls together in addition to the tall wall
heights. The out-of-plane collapse of the compound wall at the school building in Gandhidham is
owing to the large unsupported block masonry panel (Figure 11-61). When the blocks are made as
wide as the wall (usually 230 mm), the concept of header and stretcher is not adopted in masonry
construction. Long unsupported spans made of such blocks, like compound walls and parapets,
did not performed well during this earthquake.
In two-story masonry structures, irrespective of whether the masonry is in sandstone, clay brick
or cement blocks and in mud/cement mortar, stair towers performed very poorly (Figure 11-62).
Where the service water tanks are located over the slab of the stair towers, the problem was even
TRADITIONAL CONSTRUCTION IN KACHCHH REGION
Traditional houses, or bhongas, in the Kachchh region consist of a single room circular in plan,
the diameter varying from 3 m to 6 m (Figure 11-63). The walls are made of sun-dried (adobe)
bricks and are about 500 mm thick. The roof is pitched and made of bamboo sticks and thatch. A
Figure 11-51. Granite stones up to 350-400 Figure 11-52. Traditional racking in hollow
mm are used by the Indian Railways in the cement block shear walls and failure of
construction of single and twin residential units Mangalore tile roof was observed at the
in Gandhidham. This construction incorporates Commerce College Building in Adipur. There is
plinth and lintel bands. The walls are pointed on no lintel band and no plinth band, but a damp-
the outside with cement mortar. These single- proof course is provided at the plinth level.
story houses performed very well. Nominal
cracking was seen at the interface between the
roof and the walls, and at the plinth beam level.
Masonry Structures 213
Figure 11-53. Single-story
row housing in the Kandla
Port Trust residential colony
Figure 11-54. Hollow cement block construction Figure 11-55. Innovation in concrete block
without plinth and lintel bands performed poorly technology led to the manufacture of special
and sustained severe cracked walls. blocks for making columns and encouraged
builders to construct multi-story frame structures
using concrete blocks.
Figure 11-56. Beams and slabs were of in-situ Figure 11-57. Special elements were also made
concrete. for sill and lintel bands so that reinforcement
could pass through them.
Masonry Structures 214
Figure 11-58. Hollow cement block wall Figure 11-59. Roof collapse of two-story building
separated into two wythes. of solid cement blocks. The building was under
construction at the time of the earthquake.
Figure 11-60. Warehouse of solid cement blocks Figure 11-61. Out-of-plane collapse of cement
had no lintel band. block wall.
Figure 11-62. The
of masonry work that
defines the staircase
sustained severe distress.
In this case, the tank was
resting on the slab (not in
the picture), and not on
the stair tower.
Masonry Structures 215
central post (100-150 mm diameter) is propped by a wooden log (200-250 mm diameter) running
diametrically across the room and resting on the walls, supports the roof (Figure 11-64). Large
local stresses are generated in the circular walls at locations where the horizontal post of the roof
system rests. The brittle mud walls gave way under these large local stresses, resulting in the
collapse of the entire structure. There are no openings built under the point where the wooden
log is supported on the wall. No separate foundation is made for this structure. The adobe wall
is started about 1.0 m below ground, the plinth is raised about 300 mm above ground, and the
wall 2.1 m above that. The major departure from the traditional construction in new construction
is that the traditional thatch roof is replaced with a heavy Mangalore tile roof (Figure 11-65). In
recent times, some bhongas were also made in burnt clay bricks and cement mortar. Plinth and
collar bands are also included in some instances.
The bhongas had many earthquake-resistant features such as light roof, walls with small
slenderness, few openings, and low height. However, low lateral strength and the heavy log of
wood supporting the roof are negative factors. The bhongas suffered varying levels of damage.
Most of the older ones and those made in mud mortar suffered collapse; bhongas made with bricks
and cement mortar performed better.
Figure 11-63. Traditional construction of rural Figure 11-64. Large local stresses are generated
houses consisted of circular mud walls and in the circular walls at locations where the
thatch roofing. horizontal post of the roof system rests.
Figure 11-65. Heavy Mangalore
roof tile has recently begun replacing
light thatch roof.
Masonry Structures 216
Pols are three-story houses built in Historic times. These pols are examples of the earthquake-
resistant construction prevalent in the region. The Kachchh region is known to be subjected to
moderate to severe seismic shaking, and earthquake resistance was consciously built into historic
housing constructed for centuries. A wood frame with thin clay brick infill masonry in lime mortar
formed the basic structural system. Intermediate horizontal bands reduce the panel size of the
masonry (Figure 11-66). A pol consists of a highly redundant wooden frame infilled with clay
brick masonry in lime mortar (Figure 11-67). This lintel and post method of construction has a
flooring system of wooden floor planks finished with heavy stone slabs laid on broken clay brick
pieces in mud mortar. It has highly decorative woodwork surrounding the openings and vertical
posts (Figures 11-68 and 11-69).
In general, these historic structures showed no collapse. In some of these buildings, deterioration
due to aging and indiscriminate additions was significant, and some of these structures tilted out-of-
plumb after the earthquake. Many of these historic houses performed well during this earthquake.
Spalling of plaster and frame infill separation were observed (Figure 11-69).
Figure 11-66. Details of a typical Pol construction. This three-story b
house has a long plan. The large number of wood frames used in the
transverse direction (shown in black) are highlighted in b.
Masonry Structures 217
Figure 11-67. Pols, historic
structures in the region, have
highly redundant wood frame
infilled with clay brick masonry
with lime mortar.
Figure 11-68. Decorative
bracing on historic Pol.
Figure 11-69. Spalled plaster
and frame infill separation in
Masonry Structures 218
Figure 11-70. Anjar is divided into 12 wards, the most central of which sustained the most damage.
DAMAGE IN ANJAR
The town of Anjar was shaken not long ago during the 1956 Anjar earthquake (Mw 6.0). Residents
of Anjar recall the 1956 event to be of a shorter duration, with relatively lighter shaking intensity
than the 2001 event. The population of Anjar was around 30,000 during the 1956 earthquake, and
at the time of the January 26, 2001 event it was around 55,000.
The town of Anjar has an area of about 12 km2. Older structures that were either undamaged or
reconstructed after the 1956 earthquake were spread over a central area of 2.5-3 km2. The town of
Anjar is divided into wards (Figure 11-70). The old town lies in the middle of Anjar and consists
of wards 3, 4, 5, 9, and 10 (circled by a dashed line). Around this central area lies the new Anjar.
Damage was primarily restricted to the five wards of the old Anjar town. Wards 3, 4, and 10 in
old Anjar sustained near total collapse of all buildings. These wards were also damaged during the
1956 Anjar earthquake. Ward 10 is apparently reclaimed from a 300-400 year old pond. Wards 5
and 9 sustained lower levels of damages in both this earthquake and the 1956 event.
Comprehensive repair and strengthening was not undertaken after the 1956 earthquake.
Construction in the old Anjar area is random rubble sandstone masonry in lime mortar with walls
up to 750 mm thickness. Use of mud mortar is rare in this type of construction. No earthquake-
resistant features like bands were provided. Structures in wards 3, 4, and 10 were rebuilt after they
collapsed during the last earthquake from the rubble using the construction methods prevalent
at that time.
The development of new Anjar took place mostly in the last decade. Construction in new
Anjar had similar configurations to those in the old Anjar area. This new masonry construction,
however, was different in the following aspects: Structures were made of cement mortar instead of
lime/mud mortar, as was common in the old Anjar area. Lintel bands had become a more common
feature in residential construction.
Masonry Structures 219
It was expected that construction practice in this old town would take a turn for the better after
the 1956 earthquake. However, the country had neither adequate awareness of earthquake-resistant
construction at that time, nor any formal guidelines to make masonry construction earthquake-
resistant. Post-1956 Anjar earthquake construction in old Anjar was no better than practices in
effect before the earthquake. These structures again performed poorly during the 2001 Bhuj
earthquake (Figures 11-71 and 11-72). Total or near total collapses of structures in this region
suggest the following deficiencies:
• Inadequate walls. Structures with stone masonry walls in lime mortar may have weathered
over the last four decades, leading to further deterioration of their strength. The re-used
sandstone masonry blocks from the rubble of the 1956 event may have poor bond
characteristics. The large thickness of up to 750 mm, coupled with the construction of walls
in two wythes makes these structures vulnerable under strong seismic shaking (Figure 11-
73). Unsupported masonry panels in tall masonry walls performed poorly (Figure 11-74).
Even though there was total devastation in old Anjar, an occasional structure stood upright
in this area and showed that construction with lateral force resisting elements (wooden post
and lintel systems, or inclined members providing bracing) would have allowed buildings
to perform much better under seismic shaking (Figures 11-75 and 11-76).
• Inadequate roof-to-wall connection. Wood runners were placed room-wise (i.e., just for
the length of the room and not over the full length of the house spanning over the walls)
due to lack of adequate lengths (Figure 11-77). This resulted in the floor system of each
room behaving independently and pulling apart from the others during strong shaking
(Figures 11-78 and 11-79). Also, the failure of the walls into two wythes has contributed
to the collapse of the roof systems and the consequent large number of fatalities.
Lessons from Anjar highlight the vulnerability of re-used construction material and of structures
without earthquake-resistant features. It is important that these features be incorporated into
construction, particularly when massive reconstruction work in the area is about to begin.
Figure 11-71. The area most affected in Anjar Figure 11-72. Re-use of the rubble from the
was the area of town that sustained collapses 1956 earthquake, the extensive use of weak
during the 1956 Anjar earthquake and was then lime mortar, and highly irregular dwelling units,
rebuilt with the rubble. coupled with the lack of basic earthquake-
resistant features, contributed to this total collapse
in the older section of Anjar.
Masonry Structures 220
Figure 11-73. The thick walls
with small size rubble and no
through-stones led to splitting
of walls into two wythes and in
many cases impaired the gravity
load carrying capacity.
Figure 11-74. Reducing height
of unsupported masonry panels
in the tall gable walls may be
an important contribution in the
Figure 11-75. In old Anjar,
where almost all structures
collapsed, this building with
lintel and post system survived.
Masonry Structures 221
Figure 11-76. The inclined reinforced concrete Figure 11-77. Discontinuous runners over
slabs of stairs may have provided some lateral interior walls contributed to damage and/or
strength to the weak masonry system. structural failure.
Figure 11-78. Inadequate floor-to-wall Figure 11-79. Floors pulled apart in strong
connection. Flooring system is three layers of ground shaking.
closely-spaced cross runners.
The widespread damages experienced by masonry structures can be attributed to inadequacies
of the roof and walls. Owing to the difficulties in investigating below the ground, the deficiencies
in the foundations, if any, were usually not exposed. Performance of the masonry construction in
the quake-affected area suggests that the roofing systems employed in the Kachchh region had
the following deficiencies:
1. Heavy roofs with large diameter wooden logs in the roof truss.
2. Roof truss is usually an A-frame with no bottom tie member. This implies that the inverted
V-shaped roof system has a greater tendency to open up and flatten out—either because
the nailing between the two rafters at the crown is only nominal, or because the purlins
are just resting on gable walls, which are themselves tall, slender and vulnerable to out-
Masonry Structures 222
3. Rafters rest directly on the masonry walls with no connection between the roof and the
walls. This suggests that large inertial forces are not always transferred to the walls, and
implies an unstable roof system that can collapse.
4. Roofing elements, namely the tiles, are themselves not integrally connected, and consequently
the diaphragm action in the roof is absent.
5. Gable roofs do not have tie bracing in the horizontal plane, particularly at the gable walls,
and seismic forces from such roofs are not safely transferred to the walls.
Wall systems employed in the Kachchh region also showed numerous deficiencies, namely:
1. Walls are not adequately connected to each other.
2. Walls are not connected to the roof with positive mechanisms.
3. Walls are very thick (up to 400-600 mm), and often fall apart into two distinct wythes.
4. Failure of the large block masonry, long unsupported walls, tall slender walls, and the
oversized openings located at undesirable locations are often the cause of wall collapses,
and thereby of the buildings.
5. Construction practice is such that one wall is built at a time. Such a construction sequence
takes away the basic essence of making an earthquake-resistant house, which is supposedly
to act as a single unit. The presence of a clean vertical construction joint at the corners, where
the integrity of the wall system is most desired, is a major deficiency in this construction.
In limited cases, walls are properly connected through the deployment of proper bonding
courses in alternate layers.
6. The walls of buildings built with hollow cement blocks are usually left unplastered and
hence suffered extensive weathering. Instances of weathering of the hollow blocks were
noted in some places where the outer layer of the hollow blocks has fallen off. This matter
may require detailed investigation.
Owing to the above structural and constructional features, which clearly violate the requirements
of buildings in Seismic Zones IV and V as per the Indian Standard guidelines, the large number
of fatalities from building/dwelling collapses during this Mw 7.7 earthquake is no surprise.
Masonry construction in the Kachchh region is built by rules of thumb and traditions of
construction technology that are handed down from one generation to the next. No engineering
calculations are performed to assess their seismic adequacy, nor do experienced engineers always
supervise such construction. Thus, there is ample room for this type of construction to deviate
from desired construction practice. For these reasons, one cannot guarantee that no collapse will
occur in these constructions.
Damage to masonry construction in the Kachchh region were due to known ills of masonry
and the use of heavy and loosely formed roofs. These damages stand as graphic examples for the
people of the region on the vulnerability of their own construction. Similar lessons were learned
in the aftermath of two Indian earthquakes of the past decade, namely 1993 Killari earthquake
and 1999 Chamoli earthquake. The former primarily demonstrated extensive collapse of random
rubble masonry walls due to lack of integrity within them, and the latter primarily showed lack
of integrity in the heavy pitched roofs composed of tiles supported on wooden rafters and purlins.
Observations made in the aftermath of these two past earthquakes in India have had positive
influence on subsequent construction in those areas. It is hoped that the studies on seismic damages
sustained by the masonry construction of the Kachchh area will also lead to positive changes in
the construction practices of the region.
Masonry Structures 223
Information dissemination on lessons learned from seismic performance of masonry construction
during past earthquakes in India is generally absent; there are small efforts in the aftermath of an
earthquake, and that to a limited audience. Unfortunately, the only other way of educating local
people and artisans en-mass regarding the quality of their own construction is through the test of
another real earthquake. Interestingly, in India, very few masonry structures are formally designed,
even for gravity loads, despite the existence of a design code for this purpose (IS:1905-1987; IS:
4326-1993) for over three decades. Further, even the Indian Standards dealing with earthquake-
resistant masonry, low-strength masonry, and earthen construction published in 1993 (IS:13827-
1993 and IS:13828-1993) are, in general, not implemented owing to lack of knowledge of their
existence. Comprehensive long-term planning is urgently required.
The authors are grateful to the large number of engineers in both government and private
sectors of the state of Gujarat, and in particular to all the enthusiastic team of engineers of the
SRC Limited, Adipur, who provided information and showed the damaged structures in detail.
The authors from IIT Kanpur gratefully acknowledge financial support from the Department of
Science and Technology, Government of India for partial support towards the studies on the Bhuj
IAEE, 1986. Guidelines for Earthquake Resistant Masonry Construction. International Association of Earthquake
Engineering, Tokyo, Japan.
I-UNM 1984. Vernacular Housing in Seismic Zones of India, A report prepared under Joint Indo-U.S. Program
to Improve Low-Strength Masonry Housing. INTERTECT and University of New Mexico for U.S. Foreign
Disaster Assistance, Agency for International Development, Washington, D.C.
ISET, 1989. A Manual of Earthquake Resistant Masonry Construction. Indian Society of Earthquake Technology
University of Roorkee, Roorkee.
IS:1905-1987. Indian Standard Structural Use of Unreinforced Masonry—Code of Practice. Bureau of Indian
Standards, New Delhi, Third Edition.
IS:13827-1993. Indian Standard Improving Earthquake Resistance of Earthen Buildings—Guidelines. Bureau
of Indian Standards, New Delhi.
IS:13827-1999. Indian Standard Improving Earthquake Resistance of Earthen Buildings—Guidelines. Bilingual
Edition, Bureau of Indian Standards, New Delhi.
IS:13828-1993. Indian Standard Improving Earthquake Resistance of Low Strength Masonry Buildings—
Guidelines. Bureau of Indian Standards, New Delhi.
IS:13828-1999. Indian Standard Improving Earthquake Resistance of Low Strength Masonry Buildings—
Guidelines. Bilingual Edition, Bureau of Indian Standards, New Delhi.
RGF, 1994a. Earthquake Problem: Do’s and Don’ts for Protection. Rajiv Gandhi Foundation, New Delhi,
RGF, 1994b. Earthquake Problem: Do’s and Don’ts for Protection. Rajiv Gandhi Foundation, New Delhi,
RGF, 1994c. Earthquake Resistant House. Rajiv Gandhi Foundation, New Delhi, (in Hindi).
LVS, 1995. Earthquake Resistant House Construction—Instruction Booklet, Lok Vigyan Sansthan, Dehra
Dun, July 1995, (in Hindi).
Return to Table of Contents Next Chapter
Masonry Structures 224
C.V.R. Murty, M.EERI, Indian Institute of Technology Kanpur, Kanpur, India
Jaswant N. Arlekar, Indian Institute of Technology Kanpur, Kanpur, India
Durgesh C. Rai, M.EERI, Indian Institute of Technology Kanpur, Kanpur, India
H. B. Udasi, Sindhu Resettlement Corporation Limited, Adipur, India
Debashish Nayak, Ahmedabad Municipal Corporation, Ahmedabad, India
C.V.R. Murty and Jaswant N. Arelkar took all the photos in this chapter, except as noted below.
Figure 11-2 by J.P. Bardet, M.EERI, University of Southern California,
Los Angeles, California, USA
Figure 11-21 by Durgesh Rai
Figures 11-63 and 11-65 by Robin Choudhurry, M.EERI, University of Woloongong, Australia
Figure 11-64 by Kishore Jaiswal, Indian Institute of Technology Bombay, Mumbai, India
Figure 11-66 by Debashish Nayak, Ahmedabad Municipal Corporation, Ahmedabad, India