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Masonry Structures

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INTRODUCTION

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 thevulnerability 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:

HISTORICAL PERSPECTIVE

The Kachchh region has two distinct eras of development. Early construction took placeunder royal families that lived in the region over the past ve centuries. More recent and more

signicant 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

2,600acres; the Port of Kandla received an adjoining 4,320acres.

By 1958, SRC completed a major part of the construction in two locations, which are todays

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 signicant 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 inux of people into the region. Though relatively little


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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

early 1980s.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 offatalities 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 signicant 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 ofconstruction in the Kachchh region.

Damage Level*

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, ofcial site of

Government of Gujarat (September 2001)


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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, signicantly 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 theregion (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 throughthe 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).

Figure 11-1. Epicentral region of the 2001 Bhuj earthquake showing villagesdiscussed in this report.


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TYPES OF CONSTRUCTION

Masonry dwellings in the Kachchh region include many types of load-bearingconstruction.

In older construction, walls were made from rammed earthand 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 ownerscould 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

roof.1

Clay brick masonry in mud mortar with tile roof.

Semi-dressed/dressed stone masonry (coursed) in mud/cement mortar with reinforced

concrete.

Random rubble stone masonry (uncoursed) in mud/cement mortar with reinforced concrete

slab roof.

Burnt clay brick masonry in mud/cement mortar with clay tile1/reinforced concrete slab

roof.

Solid/hollow cement block masonry in cement mortar with clay tile1/reinforced concrete

slab roof.

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 rst 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 oors and roof. Suchhybrid 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

to collapse.

Figure 11-8. Lack of through-stones causedseparation of wythes.

Figure 11-9. Separation of wythes causedcollapsed of wall and roof.

1 Clay tiles are used as covering material and supported on a wooden truss-purlin system or on a

framework of wooden joists.


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Figure 11-12. Clay brick masonry in mud mortarwith tile roof.

Figure 11-13. Coursed stone masonry in cementmortarwith RC slab roof.

Figure 11-14. Random rubble stone masonry incement mortarwith RC slab roof.

Figure 11-15. Clay brick masonry in cementmortar with RC slab roof.

Figure 11-10. Random rubble stone masonry inmud mortar with tile roof.

Figure 11-11. Stone masonry in cement mortarwith tile roof.


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Figure 11-16. Cement block masonry in cementmortar with RC slab roof.

Figure 11-17. Improper connection betweenwalls (Samakhyali village).

Figure 11-18. Poor shear strength of stonemasonry in the lower story of structure with lintel

bands (Bhuj).

Figure 11-19. Loosely formed roof withMangalore tiles (Bhuj) led to serious damage/collapse of structures.

Figure 11-20. This 3-story load-bearingconstruction (Gandhidham) had exterior walls ofstone masonry and interior walls of hollow cement

blocks. Lintel and plinth bands were provided.This structure performed well, while its adjoining5-story reinforced concrete frame buildingssustained serious damages and collapses.

Figure 11-21. The rst story of this masonrystructure in Anjar, constructed of randomrubble stone masonry in lime mortar, collapsedcompletely. The second story, of brick masonrywith cement mortar, experienced minimaldamage.


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LINTEL BANDS

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 joinedby 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 faade

is plastered to imitate a lintel band.

Figure 11-23. Improvisation ofloft slabs as lintel band.

Figure 11-22. Reinforcedconcrete band at lintel level.


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IRREGULARITIES

Masonry construction in the region was often built incrementally, and hence the nal structural

conguration 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

conguration. 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 conguration irregularities,

torsional response was generated, and they performed poorly as they failed to resist the increased

torsional shear stresses.

FOUNDATIONS

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 murrumsoil (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 widetrench 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 rst 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 requiredby the government specications.

In the rural setting, the above procedure of foundation construction is severely simplied

(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 rst 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 lled 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 ush 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


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Figure 11-24. Typical foundation specications for masonry construction in the Kachchh region:a. Formal version adopted in better construction, andb. Basic version adopted in poor quality construction.

a b

Figure 11-26. Large uncoursed granite blocksplaced from both sides; a central weak plane isformed.

Figure 11-25. Shallow trenching.

Figure 11-27. Inside foundation surface pointed,outside surface left unnished.

Figure 11-28. Masonry in large-block sandstoneunder construction. A plinth band is provided.


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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 residentialunit, 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 unnished (Figure 11-27).

In government construction, and in construction by qualied 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 difcult. 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 lightsandstone.

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-neededinterlocking 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 600mm 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 signicant portion of the large-block masonry above, jeopardizing the safety and stability of


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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

signicant 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 suitablefor 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 signicantly over the years. Around

Figure 11-29. Stone blockunits used in masonry

construction in the Kachchhregion. The tape is held outto 30 cm.


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the same time, major government agencies like Indian Railways, the Kandla Port Trust, and theMilitary 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 nishes.

Currently, the hollow blocks construction is waning due to lack of quality in manufacturing. Thecompressive 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 y ash, has led to the growth

Figure 11-30. Solidcement blocks.

Figures 11-31, 11-32, and 11-33. Three types of hollow cement blocks.

Figure 11-31 Figure 11-32 Figure 11-33


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of cement-based masonry units (Figure 11-34). The y 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 11-2presents an overall comparison of the various masonry units in use in the Kachchh

region.

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). Specialblocks are also available for introducing the anchors and fasteners for the window and door frames

(Figure 11-39).

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 rst, 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 signicant

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

Figure 11-34. Fly ash bricks have begun togain popularity as a building material.


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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

380280120 at Anjar; and very poor bond is achieved.

400230200 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

(390200190) 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 withmortar 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

(23010075) 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


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Figure 11-35. Special channel bricks facilitateplacement of reinforcement bar.

Figure 11-36. Cement channel bricks.

Figure 11-37. Plinth band reinforcement. Figure 11-38. Corner reinforcement.

Figure 11-39. Special concreteblocks are used to anchor door andwindow jambs.


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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 roong 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

11-43).

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 roong systems indicates the former to be more efcient.

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 imposea dead load of about 1kN/m2. Both Mangalore and slit-tube roong systems require specially

shaped coping element to cover the ridgeline of the pitched roofs.

Other roong 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 areoften not completed there is no bottom chord in these trusses. There are two basic forms of theroofs adopted. a.) Roof with heavy rafters and b.) Roof with heavy intermediate purlins. Roof tiles aresupported by battens and purlins of small cross-sections laid over these main rafters or purlins.

a b


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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 soft of the slab. The performance of these

roong 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 STANDARDSThe 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 species materials to be used, maximum permissible stresses, and methods of design.

However, selection of materials and special features of design and construction of earthquake-

resistantmasonry buildings are given in another Indian Standard (IS:4326-1976).

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 weighs0.3-0.4 kg.


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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-resistantdesign 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, concreteblocks, 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 specications were not followed in structures in the affected area, a region

in Seismic Zone V.

Based on their nominal mix proportions, the masonry code classies 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 requirementsgiven 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 specications on the mortar and masonry units are not enforced.

The code species 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/torl/t), where h and lare 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.


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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. Trussedroofs 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 10tor 64t2/h, where tis 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 specied 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

also. 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 red 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 recommendedfor 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 claries 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 classies buildings in Seismic Zones III, IV, and V into ve 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 specic recommendations on the structural conguration and special earthquake-resistant

features to be built into them. For example, the limitation on the building height is specied as


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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 identied. Brick masonry construction shall be made

with bricks of compressive strength not less than 3.5MPa. Strength of bricks and wall thicknessare 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 at 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 exible 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 eld 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 AREAThe publicationVernacular 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 eld 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-strengthmasonry, as specied in IS:13828-1993.

Building Category

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

Flat roof

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


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structural integrity and conguration. It identies deciencies in masonry structures and suggests

measures to overcome those deciencies. The detailed review of stone masonry houses in the

Bhuj region identied 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

Dos and Donts for Protection against the earthquake problem. The booklet was published in

two languagesin 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 roong 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

fullling 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 makethe 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,


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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 signicant way to counter seismic forces.

Older construction used a large amount of wood in the post and lintel system, thereby providingsome 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 ne shear cracks in stiff walls. Pink sandstones cut to 450 mmlargest

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(collapsed) structure is being used to rebuild thisunreinforced masonry house.

Figure 11-46. Pink sandstone of up to 600 mmin size was used in construction of these two-story housing units.

Figure 11-47. Mud mortar is sometimes as thickas 8 cm. The tape is held out by 30 cm.

Figure 11-48. Walls built with large stonesand no through-stones separated into wythesimpairing the vertical load-carrying capacity.


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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 discontinuouslintel bands, performed very poorly. Construction with lintel bands performed well. Unconned

masonry piers sustained damage.

The rst 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. Ofces, 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

(Figure 11-54).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 (Figures11-55through11-57). 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.

Figure 11-49. Older construction used a largeamount of wood in the post and lintel system,thereby providing some lateral resistance to theinherently weak stone (granite) masonry in mudmortar.

Figure 11-50. This construction, underway inBhuj at the time of the earthquake, provides a

plinth band, but not a lintel band.


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Due to falling quality control in the manufacture of hollow block units, their low compressive

strength, and the increasing popularity of y 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 createa poor bond with the cement mortar. Solid cement blocks tend to have at 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

more aggravated.

TRADITIONAL CONSTRUCTION IN KACHCHH REGION

BHONGAS

Traditional houses, orbhongas, 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

mmare used by the Indian Railways in theconstruction of single and twin residential unitsin Gandhidham. This construction incorporates

plinth and lintel bands. The walls are pointed onthe outside with cement mortar. These single-story houses performed very well. Nominalcracking was seen at the interface between theroof and the walls, and at the plinth beam level.

Figure 11-52. Traditional racking in hollow

cement block shear walls and failure ofMangalore tile roof was observed at theCommerce College Building in Adipur.There isno lintel band and no plinth band, but a damp-

proof course is provided at the plinth level.


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Figure 11-53. Single-storyrow housing in the Kandla

Port Trust residential colonyperformed well.

Figure 11-54. Hollow cement block constructionwithout plinth and lintel bands performed poorlyand sustained severe cracked walls.

Figure 11-55. Innovation in concrete blocktechnology led to the manufacture of special

blocks for making columns and encouragedbuilders to construct multi-story frame structuresusing concrete blocks.

Figure 11-56. Beams and slabs were of in-situconcrete.

Figure 11-57. Special elements were also madefor sill and lintel bands so that reinforcementcould pass through them.


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Figure 11-58. Hollow cement block wallseparated into two wythes. Figure 11-59. Roof collapse of two-story buildingof solid cement blocks. The building was underconstruction at the time of the earthquake.

Figure 11-60. Warehouse of solid cement blockshad no lintel band.

Figure 11-61. Out-of-plane collapse of cementblock wall.

Figure 11-62. Thecantilever projectionof masonry work thatdenes the staircasesustained severe distress.In this case, the tank wasresting on the slab (not inthe picture), and not onthe stair tower.


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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 thecollapse 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 bhongaswere 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 11-65. Heavy Mangaloreroof tile has recently begun replacinglight thatch roof.

Figure 11-63. Traditional construction of ruralhouses consisted of circular mud walls andthatch roong.

Figure 11-64. Large local stresses are generatedin the circular walls at locations where thehorizontal post of the roof system rests.


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Figure 11-67. Pols, historicstructures in the region, have

highly redundant wood frameinlled with clay brick masonrywith lime mortar.

Figure 11-69. Spalled plasterand frame inll separation inthis Pol.

Figure 11-68. Decorativebracing on historic Pol.


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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 ve 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 prevalentat that time.

The development of new Anjar took place mostly in the last decade. Construction in new

Anjar had similar congurations 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.

Figure 11-70. Anjar is divided into 12 wards, the most central of which sustained the most damage.

DAMAGE IN ANJAR


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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 ineffect 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 deciencies:

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 oor 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 Anjarwas the area of town that sustained collapsesduring the 1956 Anjar earthquake and was thenrebuilt with the rubble.

Figure 11-72. Re-use of the rubble from the1956 earthquake, the extensive use of weaklime mortar, and highly irregular dwelling units,coupled with the lack of basic earthquake-resistant features, contributed to this total collapsein the older section of Anjar.


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Figure 11-73. The thick wallswith small size rubble and no

through-stones led to splittingof walls into two wythes and in

many cases impaired the gravityload carrying capacity.

Figure 11-74. Reducing heightof unsupported masonry panels

in the tall gable walls may bean important contribution in the

reconstruction effort.

Figure 11-75. In old Anjar,where almost all structures

collapsed, this building withlintel and post system survived.


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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. Roong elements, namely the tiles, are themselves not integrally connected, and consequentlythe 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 deciencies, 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 deciency 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 mattermay 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.

CONCLUSIONS

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 alwayssupervise 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

inuence 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.


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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 ofanother 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.

ACKNOWLEDGMENTS

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 nancial support from the Department of

Science and Technology, Government of India for partial support towards the studies on the Bhuj

earthquake.

REFERENCESIAEE, 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. Programto 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 MasonryCode of Practice. Bureau of Indian

Standards, New Delhi, Third Edition.

IS:13827-1993. Indian StandardImproving Earthquake Resistance of Earthen BuildingsGuidelines. Bureau

of Indian Standards, New Delhi.

IS:13827-1999. Indian StandardImproving Earthquake Resistance of Earthen BuildingsGuidelines.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: Dos and Donts for Protection. Rajiv Gandhi Foundation, New Delhi,

Hindi Edition.

RGF, 1994b.Earthquake Problem: Dos and Donts for Protection. Rajiv Gandhi Foundation, New Delhi,

English Edition.

RGF, 1994c.Earthquake Resistant House. Rajiv Gandhi Foundation, New Delhi, (in Hindi).

LVS, 1995. Earthquake Resistant House ConstructionInstruction Booklet, Lok Vigyan Sansthan, Dehra

Dun, July 1995, (in Hindi).


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CHAPTER CONTRIBUTORS

Principal Author

C.V.R. Murty, M.EERI, Indian Institute of Technology Kanpur, Kanpur, India

Contributing Authors

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

Figure Credits

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

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