Mitigation of Seismic Risk in Urban Zones of Uzbekistan as Path for

Strengthening of Sustainable Development of Region

Mashrap Akhmedov

, and Rustam Abirov

Institute of Mechanics and earthquake engineering, Dormon yoli 33, Tashkent, Uzbekistan

AKFA University, 17 Kichik Xalqa Yo’li, Tashkent, Uzbekistan

Keywords: Risk, Buildings, Development of Region, Urban Zones.

Abstract: Population growth and active urbanization processes in Central Asia lead to seismic risk increasing in this

region. Uzbekistan is most populated country in Central Asia. Along with the growth of civilian and

earthquake engineering, many individual buildings remain in cities and also have trend for expansion.

Sustainable development of region cannot be provided without safety resilience operating all civilian

infrastructures. For mitigation of vulnerability of habitants during seismic event is the most important is

housing safety. Assessment of stability for individual self-made, one and two storey residential structures are

described in this issue. Measures for strengthening of such types of buildings are recommended in this issue.

1 INTRODUCTION

Territory of Uzbekistan located in seismic prone

Central Asian region. Strong earthquakes with

intensity of 8 points and more may happen in this

area. Seismic risk for water work objects (Akhmedov,

2020) has the great importance and special State

programme are developing nowadays. Measures

against landslides or mudflows find their solution also

(Sagdullayeva, 2020). Lesson from past events

(Chan, E.Y., 2008) gives path for reliable solutions.

As urban densification occurs in Central Asian

regions of high seismicity, there is a natural demand

for seismically resilient not only for tall buildings and

for residential sector also. Therefore, the great

importance to minimise of human loses at probable

seismic event with taking into account rapid

urbanisation process and increasing of demographic

growth. For sustainable development of region the

preservation housing, industrial clusters, life line

structures has importance also.

Traditional housing has cultural aspect and

ecological friendly ones also. However safety and

living standards need improving existing situation up

to more comfortable level. Vulnerability of so

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structures and areas are high and doesn’t acceptable

nowadays.

Risk of destruction and hazard level for urban

zones (Abirov, 2016) have to be estimated and

measures should be developed for mitigation of

earthquakes consequences. Below in Table 1

probable earthquakes intensity by MSK scale is

provided for different regions of Uzbekistan.

Table 1: Probable earthquakes intensity in regions.

№ Regions of the republic Earthqu

akes

intensit

Andijan 8-9

Buhara 7-8

Djizak 7

Kashkadarya 7

Navoi 6-7

Namangan 8-9

Samarkand 7-8

Syrhadarya 7

Syrdarya 7

Tashkent 8-9

Tashkent city 8-9

Ferghana 8-9

Horezm 6-7

Republic of Karakalpakistan 5-6

Akhmedov, M. and Abirov, R.

Mitigation of Seismic Risk in Urban Zones of Uzbekistan as Path for Strengthening of Sustainable Development of Region.

DOI: 10.5220/0010585400160022

In Proceedings of the International Scientiﬁc and Practical Conference on Sustainable Development of Regional Infrastructure (ISSDRI 2021), pages 16-22

ISBN: 978-989-758-519-7

2 MAIN PART

Even nowadays most of the population lives in

seismic dangerous territories of the republic in houses

of individual construction, which are usually, one-

storey buildings (two-storey if there are more than 4

rooms). The houses with dead longitudinal wall

which looks at the street and longitudinal wall with

door and window openings which makes front yard

prevail (Figure 1, 2). That defends internal side from

summer heat.

Total population of Uzbekistan now more than 35

mln. and at least third of them living in cities

Basis of the walls made from cobble, burnt brick

and monolith concrete. Walls are built without any

additional connection with corners and crosses, with

obligatory installation of niche with depth up to 50cm

which replaces installed furniture in butt-ends of

house or in remote longitudinal walls. Laying of the

walls with niches is made in one row according to the

thickness and is the weakest part of barrier.

Connection between longitudinal and cross walls is

made by external and cross walls. There are two types

of installed roofing, 1

level from loam and haulm or

with garret on wooden roof timbers, which is

covered with asbo-slate or iron. Historically there are

traditional types of individual (private) houses with

walls from local materials.

Figure 1: Longitudinal wall of house from air bricks (photo

by P. Burton).

Figure 2: Front yard of house (photo by P.Burton).

Houses with loam and brick walls (“pakhsa”)

(Figure 3).

Houses with walls from air brick (Figure 4).

Houses with wooden frame that filled with air

brick or guvala – clay lumps (“sinch”) (Figure 5).

Figure 3: Incomplete houses from loam and bricks (photo

by P. Burton).

Figure 4: Incomplete houses from air bricks (photo by P.

Burton).

Mitigation of Seismic Risk in Urban Zones of Uzbekistan as Path for Strengthening of Sustainable Development of Region

Figure 5: Incomplete houses with wooden frame filled with

air bricks or guvala (“sinch”) (photo by P. Burton).

Moreover, single buildings from burnt bricks with

wood or concrete ceiling can be met. Nowadays, the

approximate material structure of the housing in

Uzbekistan looks like, (Table 2).

As seen on Table 2 houses from air bricks and

loam continue to dominate by quantity in Uzbekistan.

Most of the houses of this category in dense populated

cities of the republic were built 50-100 years ago. Life

times of these housing up to 30 years, but

houses/buildings are still in use. As a rule they were

built without any project and adhering to any seismic

rules. Perhaps, exactly these facts were the reason of

numerous destructions of buildings during strong

earthquakes which happened in past period.

Table 2: Structure of living fund of the republic according

to theirs walls (%).

Fabric/Material of

walls

Sum Urban Rural

area

From burnt bric

17.6 27.1 11.5

From reinforced

concrete

13.2 28.0 3.8

From air

ric

26.9 23.4 29.1

From loam 42.3 21.5 55.6

For instance, according to results of analysis of

consequences of Tashkent earthquake at 1966 it was

discovered that among all damaged buildings the

individual housing, more than 67%. During Nazarbek

earthquake at 1980 this result was more than 80%.

During Chatkal earthquake at 1946 damage of the

houses of individual building were marked at 6 points

intensity by MSK scale.

The existence of intolerable amounts of salty

inclusions, soil and atmospheric humidity are among

main conditions that may lead to premature failure of

the adobe housings. The endurance of the adobe

housings is also indirectly affected by uneven base

sediment, strong seismic vibrations and construction

errors.

The adobe housings have been built for hundreds

of years without being reinforced by housetops,

plastering, foundation or socle. For example let’s

name 4-storey adobe housings the “Chodri Hovli”,

build back in XV century in Khiva (Khorezm)

(Akhmedov, 2004). The building is situated on the

8x16m area and is 17m high. The thickness of the

“pakhsa” is 80cm at the bottom and 40cm at the top

of the building.

The aftermath of Kamashi (Kashkadarya region)

earthquake of 20.04.2004 showed that “pakhsa”

houses with difference thickness at the bottom and the

top of the wall suffered less than the houses with

“pakhsa” walls of the same thickness.

The results of the Tashkent (1966) (Raskazovskiy,

1967), Gazli (1976,1984) (Djuraev, 1985), Nazarbek

(1980) (Rashidov, 1981) and other earthquakes

obviously proved that “pakhsa” houses are destroyed

faster and more intensely than others, ranking the last

position by its seismic stability (Shamsiev, 1999).

Since the mentioned types of buildings are present

in urban zones of the republic let’s estimate their

condition based on the example of individual housing

in Tashkent. The territory of the city is 32850

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hectares, from them apartments are on 15570 hectares

(47,4%). According to the diagram of balance of the

territory (Figure 6) part of individual buildings is

more than 30% of the city territory, of which 20% are

from air brick, 7 % are from burnt brick and 3% are

from “sinch”/”pakhsa”.

Figure 6: Various types of residential buildings.

We localize buildings in 7-8 and 9 point seismic

intensity zones. In Table 3 we show the quantity of

traditional 1-2 storey buildings of Shayhontour

district of Tashkent before the earthquake between

26.04.1966 and 01.01.2001.

Before 1966 only 9 % of individual houses in this

district were from burnt brick, 33,7 % of houses were

from air brick, 30,3 % - had wood ceiling with loam

and air brick. By 2001 we see a sharp increase in (4

times) houses from burnt brick and decreasing

quantity of houses from “pakhsa” and wood ceiling

as shown in 2

part of the Table 3.

Table 3: Quantity of traditional residential structures according to their walls (sum and percentage).

Period Sum One

storey

Two

storey

Burnt brick Air brick Pahsa Sinch

1966 5948

100%

5832 98.1% 114

1.9%

528

2008 33.7% 1495

25%

1801 30.3%

2001 10115 100% 7786

72%

2329

23%

37.31 35.2% 3221 31.8% 1598 15.6% 1679 16.4%

The percentage distribution by total area is:

 12 % of the whole territory built before 1948;

 18 % before 1966;

 70 % before 2000;

The Figure 7 shows graphs of allocation of

damageability level for 1-2 storey individual

buildings during the earthquake in 1966.

Figure 7: This caption has more than one line so it has to be

set to justify.

From 682 inspected 1-2 storey houses of air

bricks: 198 (28%) had fallen walls, 380 (56%) had

huge cracks and fallen components and 104 (16%)

had small cracks which were equal to 2.4 and 5 point

level of damage. Out of 1251 objects from air bricks,

the cracks were in just 19 cases (1.4%). Big cracks

and fall of components happened in 1126 objects

(90%). In 88 objects perforated cracks vertical,

horizontal and “X” shape (7.6%) were detected. The

level of damage was grouped according to the next

characteristics:

level – well visible cracks by contour of house

partition and plaster of ceilings, vertical cracks in

places of coupling of walls and in places of weakened

overlay by ventilation and smoke channels, channels

for forming electric wiring, horizontal cracks in walls

at the level of crosspiece and window-sill, cracks in

frame walls, in places frame elements, width of

cracks is 0.5mm. Horizontal and slanting cracks in

smoke pipes and under bridle prop;

level – crumbling and fall of plaster of walls

and ceilings, partial collapse of laying of house

partitions and modelled ledges, sloping and crossing

cracks in partitions, bearing wall, damaging of laying

sections of walls in places of relying beam of

partitions vertical and transparent horizontal cracks in

places of coupling of walls and from corner of

apertures, partial collapse and fulfillment of frame,

exfoliation and fall out of the parts of loam walls from

Mitigation of Seismic Risk in Urban Zones of Uzbekistan as Path for Strengthening of Sustainable Development of Region

“pakhsa”, appearance of perforating vertical cracks

with width of 2-5mm, partial collapse of pipes;

level – laying exfoliation of brick partitions,

total fall of overlay, modelled cornice and fulfillment

of frame, transparent, bended and “X” shaped cracks

up to 4-5mm. in walls, displacement and partial

collapse of under roof timbers columns and stuffed

aperture. Numerous sloping, transparent and

horizontal cracks in embrasure and upper embrasure

sections of walls with crosspiece movement and

laying, total separation of walls sections vertically,

movement of beam partition, “X” shape diagonal

cracks in remote walls, separation of external walls

from internal and movement of corner sites of walls,

total broke of pipes, width of cracks in main

constructions from 2-3 to 15-20mm;

level – total collapse of partitions, partial

collapse of carrier and external carrier walls, break of

aseismic belts, significant movement and partial

collapse of partition beams;

level – collapse of single parts and the whole

building.

Researches on these damages of one and two

storey houses showed that houses from air brick,

adobe blocks, “pakhsa” at 6 point earthquake by MSK

scale in most cases get 2

level of damage, and at 7

point earthquake completely lose their carrying

ability.

However, if historically developed building

technologies are saved and constructive arrangements

during building the foundation, these houses stand

seismic impact the intensity of 7 and sometimes 8

points (“sinch”).

In Table 4 the results of the analysis and

estimation of consequences of earthquakes according

to typical damages which range within 1–5 degrees

and the experience of building houses from local

materials in the private sector are presented.

Table 4: Vulnerability of individual houses from local

materials.

Type of

individual

houses

Level of vulnerability in intensity

of an earth

uake

7 points 8 points 9 points

I. 3-4 4-5 5

II. 2-3 4-5 5

III. 0-1 1-2 5-3

The vulnerability curve (Figure 8) based on the

data on the Table 4 (Shamsiev, 1999, Akhmedov,

2006) are provided here.

Figure 8: Vulnerability curves for residential houses from:

1 – Building of “pakhsa” type, 2 – Adobe buildings, 3 –

Building with a wooden frame of a “sinch” type.

3 DISCISSION

The principal seismic design philosophy for repair

and strengthening of structures are developed in some

works and projects for different regions an as rule for

RC buildings (Necevska-Cvetanovska, 2012),

(Apostolska, 2020), etc. Asian traditional housing

investigated widely (

Tolles, 2002), (Shrestha, 2012),

rya,

2000), (Ishiyama

2018), etc.

and proposed

different path for solving strengthening problems. But

for Central Asian traditional housing these

approaches are not applicable.

Results of investigation and visual observation of

post event situation in Uzbekistan can be described as

regional results (Razakov, 2002). In some cases these

results can be expanded for neighbouring regions.

Local material’s using and traditional housing are

reality and have to be taken into account.

Investigation of housing from different types of

traditional materials can give path for improving by

using available approaches (Akhmedov, 2005).

4 CONCLUSIONS AND

RECOMMENDATIONS

According to analysis expected the next results:

 structures from burnt bricks which were built

by using aseismic measures and building

codes, during strong earthquake will take only

inconsiderable damages. To provide for

seismic stability for houses from burnt brick the

buildings in Uzbekistan are built in compliance

with republican norms “KMK-2.01.03-96 –

Building in seismic zones”;

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 residence from “sinch” will stand at earthquake

with intensity of 8 points and will not collapse;

 houses from air bricks and “pakhsa” will

collapse (destroyed). In order to enforce

“pakhsa” houses during construction, first of all

one should consider the historical experience of

technology of clay preparation and keep the

order of erecting the walls, secondly reinforce

by laying rice straw reed stalks wooden chips

or metallic net between the layers of “pakhsa”.

These materials if correctly applied, ensure

solidity of the walls, especially at conjugation

points.

The vertical reinforcement of conjugation points

with reinforced concrete mandrils, fitments of various

classes, cement filled pipes are also used in so types

of buildings nowadays. In all cases the elements of

reinforcement at the overlaying layer are hardwired,

creating a hard disk, ensuring the solidity of the whole

construction. The idea of this method is that under

seismic impact, the significant part of the load falls

onto the reinforcement elements while the function of

the building’s deformation tends to the function of the

frame structure.

Another very efficient way of increasing the

stability of “pakhsa” houses is the method of

dispersed clay reinforcement with waste from carpet

or rubber production and other fibrous materials

which could increase the solidity of carrying

elements.

The existence of the organized drainage system

plays an important role in ensuring the solidity of the

walls. Without a proper drainage system the

precipitation affects the lower part of the walls and

leads to erosion. In order to prevent such behavior we

recommend plastering the cement solution onto the

metallic net and covering it with water resistant paints

on the plinth of the wall.

In order to reinforce the seismic stability of the air

brick houses one can use the same building rules as

for the “pakhsa” houses. Additionally we can

recommend using the burnt bricks with sand-lime or

complex solution in the most important parts of the

construction such as socle, points of wall conjugation,

overlay level, piers and jumpers, doorways etc.

During the construction of the air bricks houses it

is recommended to use light materials in overlay and

housetop elements in order to decrease the inertial

load under the earthquakes.

The cheapest way to increase the flexural stiffness

of the air brick walls is to use the pilaster-walls in the

conjugation points. The “pakhsa” houses from air

brick should not be more than one storey high. The

minimum requirement to this type of houses is

building the seismic belts at the overlay levels.

There are several special requirements to the

foundation of the individual houses:

The depth of the foundation should be minimum

0,6m;

The width of the foundation should exceed the

lower part of the brickwork by 10cm;

The part of the foundation above the ground

should be minimum 0,4m;

If built on the weak soil, using the minimum 4

fittings of A11 or A1 class and wiring them with

clamps from rod with diameter of 6mm and 0.7m

increment;

After making the ditch for the foundation the

ground requires packing in order to achieve the

desired carrying capacity;

In sites close to ground water it is necessary to do

the hydro isolation procedure of the foundation;

In sites where ground water may contain

aggressive chemical elements we recommend using

the special types of cement;

During the process of laying the foundation

consider the fitting protrusions from the foundation

which should be welded with reinforcement elements

in the body of the foundation.

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