Field Reconnaissance of the October 23, 2011, Van, Turkey, Earthquake: Lessons from Structural...

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FIELD RECONNAISSANCE OF THE OCTOBER 23, 2011 VAN, TURKEY

EARTHQUAKE (MW=7.2): LESSONS LEARNED FROM STRUCTURAL DAMAGES

MURAT OZTURK

Dr., Selcuk University, Civil Engineering Department,42075, Konya, Turkey. +90 332 22326 48 [email protected]

At October 23, 2011, an earthquake (Mw=7.2) hit at eastern province of Turkey, Van, at local time

13.41 (GMT 10.41). According to records, after Kocaeli, Marmara earthquake at August 17, 1999,

this was the biggest earthquake and it claimed 604 lives near the epicenter and caused big

structural damages. Recorded ground accelerations were surprisingly low compared to the

structural damage observed within the region and recent Turkish earthquakes. Its peak value was

approximately 1.78 m/sn2. The objective of this article is taking a look at the reasons of damages

that exist on reinforced concrete and masonry buildings. Additionally, general characteristics of

Van Earthquake, seismo-tectonic characteristics of the region and evaluation of peak acceleration

value are presented. All factors which caused damage and collapse are presented as sections and

the observations are compared to TEC (2007) (Turkish Earthquake Code) and TBC-500 (2000)

(Turkish Building Code) terms.

Keywords: Earthquake damages, failure types, Turkish Building Code

Introduction

Turkey is a country where destructive earthquakes happen frequently and it is very seismically

active. The earthquakes are also concentrated along the North Anatolian Fault (NAF), East

Anatolian Fault (EAF), North East Anatolian Fault (NEAF) and West Anatolian Fault (WAF) as a

result of north-ward motion of the Arabian plate and African Continent (Dogangun, 2004).

Turkey’s tectonic map and movement direction of plates are shown at Figure 1. Last century, 12

earthquakes which have magnitude bigger than 7.2 according to Richter Scale occurred and at

these earthquakes there were thousands of deaths and approximately 500.000 buildings were

collapsed or highly damaged. Most significant reason of these big losses is; earthquakes in Turkey

are shallow focused. However, despite being an earthquake country, lack of adequate strength and

rigidity and weakness of control mechanism of buildings causes too many deaths and economical

loss.

The most destructive earthquake occurred in the vicinity of the Van Lake (located in Eastern

Turkey) took place in November 1976 in Caldiran, about 70 km away from Van with a magnitude

of 7.3. This seismic event and the severe weather conditions raised the death toll to 3840 and more

Journal of Performance of Constructed Facilities. Submitted June 28, 2013; accepted October 29, 2013; posted ahead of print October 31, 2013. doi:10.1061/(ASCE)CF.1943-5509.0000532

Copyright 2013 by the American Society of Civil Engineers

J. Perform. Constr. Facil.

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than 9552 buildings were damaged. 35 years later from this disaster, on October 23, 2011 at 13.41

(GMT 10.41) local time, an earthquake of 7.2 magnitude happened where epicenter was 30 km

away from Van city center. The epicenter coordinates are reported as 38.68N – 43.46E and the

depth is given as 19.02 km by the Earthquake Department of the Disaster and Emergency

Management Presidency (AFAD). Magnitude and source characteristics of the earthquake are

defined by various institutions as given in Table 1. In the table, hhypo is the depth of hypocenter of

the earthquake, ML is the local magnitude and Mw is the moment magnitude. Earthquake was felt

in 8 cities where 5 % of Turkish population live and caused death and economical loss in Van

where 1.4 % ( 1.000.000) of population lives. According to official sources 604 people died and

4152 people injured. According to first data (AFAD, 2011), 2262 buildings were collapsed, 5739

buildings were heavily damaged and 4882 buildings were damaged lightly or moderately. Damage

was concentrated in Erciş county (pop. 91.915), villages in the vicinity of Van (Gedikbulak,

Alaköy, Yaylıkaya etc.) and Van city center (pop. 381.163). As the subjective observation of

author, intensity level was IX in Erciş, VIII-IX in the villages, and VII in Van city center. A

possible spatio-temporal scenario of Van earthquake consists of two or three major sub events,

following each other towards south-west, with decreasing size and increasing origin time

(Zahradnik and Sokos,2011).Damage distribution at this vicinity justifies this assumption.

Tectonic Features of the Region

Lake Van basin, which is in the north of the Bitlis Thrust Belt where the Arabian Plate was sub

ducted beneath the Eurasian Plate, is located between Zagros Fault Zone and Karlıova Joint, where

the North Anatolian Fault (NAF) intersects with East Anatolian Fault (EAF) (Ozvan et al.,2005)

(Figure 1). The NAF extends along Karlıova (Bingöl) and Malazgirt (Muş), then passes the north

of Lake and then transforms into a several local faults in the east. The area north of Lake Van has a

complex structure including several faults (Figure 1). Historically, Van and its surroundings have

experienced several destructive earthquakes. Table 2 shows some previous earthquakes in the area

and their effects.

Seismic activity from 23.10.2011-10.11.2011

A long series of aftershocks has followed the main quake. In 72 hours, 7 events of magnitude

larger than 5 occurred and more than 570 aftershocks of magnitude larger than 3 were recorded.

As of 10.11.2011 the number of aftershocks exceeds 2500. The time dependent variation of the

aftershocks is given in Figure 2.

Evaluation of Strong Ground Motion

Van earthquake of October 23, 2011 was recorded by accelerometer stations located in different

areas of Turkey within the scope of the National Web of Observation of Strong Earth Motion of




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AFAD (Disaster and Emergency Management Presidency). Table 3 shows the properties of 6

stations closest (0–200 km) to the epicenter, which recorded the largest values. In the table Repi is

the epicentral distance from the station, RJB is the closest distance from station to the vertical

projection of the rupture plane and PGA is the peak ground acceleration.

The strong motion accelerogram having Repi = 46.63 km has the smallest epicentral distance. It

was recorded at the Muradiye station located in the Directorate of Meteorology Building. The

three accelerations (NS, EW and UD) recorded by this instrument are given in Figure 3. As seen

from the Table 3, the peak ground accelerations are 178.55 mG ( 179 cm/sn2) in the North-South

direction, 169.45 mG ( 169 cm/sn2) in the East-West direction and 79.15 mG ( 79 cm/sn2) in the

vertical direction. However, the maximum PGA values of 0.182g, 0.172g and 0.081g for NS, EW

and UD directions, respectively, are found to be surprisingly low compared to the damage

observed within the region. Therefore maximum ground motion parameters at the epicenter were

examined based on the attenuation in PGA values. Figure 4 shows some attenuation relations

suggested by researchers and the distribution of Van earthquake data given in Table 2. The curves

are observed to give results that are consistent with each other. As seen in Figure 4, the data show

that the relationships recommended for PGA attenuation during previous earthquake events are

very similar to the records for the Van earthquake of October 23, 2011. However, when the

records of nearby stations were examined, the closest relationship was found at Ulutas and Ozer

(2010). Considering this attenuation relationship, the epicentral PGA is estimated as 0.333g for

Van earthquake.

Damage of Reinforced Concrete (R/C) Structures During the October 23, 2011 Van

Earthquake

General characteristics of the buildings in the region

Buildings in Turkey are categorized as engineered and non-engineered. In parallel with the level of

economic development, while the city centers and districts contain R/C buildings, traditional forms

of masonry building are used in villages. In Van Region, city center and Erciş district consists of

R/C buildings and buildings in villages were constructed of stone, briquette and adobe material.

Throughout Turkey (and also in Van region), typical reinforced concrete frame building consists

of a regular slab, rectangular or square columns and connecting beams. The exterior enclosures as

well as interior partitioning are of non-bearing unreinforced brick masonry infill walls (Dogangun,

2004). Generally, in the main street, the height of the ground storey is greater than regular storey’s

in order to facilitate commercial purposes. As per public improvement laws, plan dimensions may

be increased after the ground storey (overhangs) and so the size of storey’s are increased. A

sample reinforced concrete frame building is shown in Figure 5.




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Structural damages and causes of failures

Eight codes about earthquake have been adopted since the foundation of The Ministry of Public

Works and Settlement, and each of these codes have been developed and amended after

earthquakes, due to their insufficiencies. Current earthquake code were developed in 1998 (TEC,

1998), and the section titled “evaluation and invigorate of the existing buildings” was updated in

2007 in order to evaluate the performance of existing buildings under the effects of earthquake

(TEC, 2007). Structures built in compliance with TEC (2007) and TBC-500 (2000) codes provide

a certain level of security; however, older structures, especially those built before the TEC (1998)

code, suffer great damage and destruction from earthquakes due to insufficient code regulation and

lack of control mechanism. Based on the results of field investigations and studies of previous

earthquakes, the basic reasons for structural damage observed in R/C buildings are briefly

explained following the Van earthquake of October 23, 2011.

Soft and weak storey

Soft storey effect is one of the main causes of damage sustained by R/C buildings during

earthquakes, both in Turkey and around the world (Dogangun, 2004; Sezen et al., 2003; Goel,

2003; Xue, 2000). An important proportion of business and residential buildings located in the

main street in Turkey involve soft storeys due to the use of ground storey for commercial

purposes. In these types of buildings, the height of the ground storey is generally higher and glass

walls are made for presentation instead of brick infill walls. Brick infill walls are known to

increase the stiffness of a building and limit storey drift. Studies show that the removal of brick

infill walls on the ground storey may reduce load-carrying capacity by 30% and increase

maximum storey drift by 10% (Arslan and Korkmaz, 2007).

The displacement in ground storey increases as a result of the removal of infill walls and the

reduced drift stiffness due to the increase in storey heights. However, deformation capacity of the

ground storey remains limited due to the absence of rigid shear wall and undetailed columns,

according to TEC (2007) provisions, and structures were shown to collapse on the ground storey

due to shear fractures. Figure 6 shows four structures in Erciş district that observed soft storey

damage. While some buildings with such damage are completely collapsed, in others even the

windows in the upper storeys were unbroken. It is remarkable that the structures shown in Figure 6

are not high-rise buildings. A previous study confirmed that the infill wall effect is more critical in

low rise buildings made up of weak elements (Inel et al., 2008). The same study also reported that

soft storey behavior due to the absence of infill walls is far more dangerous than soft storey failure

due to high storey heights. These two undesired conditions exist in many buildings in the region

and contributed to increasing the level of damage and destruction caused.




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Soft storey damage can be prevented by providing sufficient shear walls in these kinds of

buildings. TEC (2007) requires sufficient shear walls to be used in load bearing systems that do

not provide high ductility located in 1st and 2nd degree earthquake regions (peak ground

acceleration 0.4g and 0.3g, respectively). However, the ductility provisions of load bearing

systems have not been ensured in Van (the majority of which is located in 1st, remaining parts in

2nd degree earthquake region) and shear walls are not present, resulting in a great deal of damage.

Inadequate detailing of structural components

Structures can remain standing after earthquakes if their structural components have sufficient

ability to withstand dynamic energy, which depends on adequate rotation capacity; in other words,

the ductility behavior of end zones between structural elements where internal forces are highest

and therefore plastic hinges might occur. Therefore, TEC (2007) envisages special detailing in

column, beam, and beam-column joints. Figure 7.a shows the detailing generally observed in

column, beam, and joint areas in typical structures in the Van region, and Figure 7.b shows TEC

(2007) provisions.

Columns

The main damage to R/C structures in the Van earthquake of October 23, 2011 was observed in

columns. The main reasons for such damage are inadequate transverse reinforcement, inadequate

cross-section dimensions, the placement of splice regions in the lower ends of columns, inadequate

length of lap splices, the use of smooth rebar, and the use of hook-in longitudinal rebars.

TEC-2007 envisages the design of special confinement zones in at least 500 mm long where

transverse reinforcements are frequently placed in the lower and upper edges of columns (Figure

7). In addition, both edges of transverse reinforcements should have hooks bent at 135o.

According to the observations of the author within the earthquake region, collapsed buildings

lacked the additional transverse reinforcement required to ensure confinement zones in the

columns (Figure 7). The longitudinal rebar ratio ranges between 1% and 2%; 12–16 mm diameter

rebar are generally used. Transverse reinforcement’s are generally smooth rebar of 6–10 mm

diameter. The spacing of transverse reinforcement’s is typically 250-300 mm uniform along the

clear height of the column. Transverse reinforcement’s were placed very irregularly and the hooks

at the ends were bent at 90o instead of 135o, resulting in rebar’s loosened under earthquakes

effects. This situation accelerated the disintegration of concrete, which already had low strength,

by preventing lateral compression to concrete. Figure 8 shows observed column damage in some

buildings in Iskele Street in Van City Center and Zeylan Street in Erciş District.




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One of the main mistakes observed in damaged members is the use of inadequate lap splices. Lap

splices in columns of a moment frame are generally made in the lower edges of columns. In other

words, lap splices were built in the plastic hinge area. In older buildings the lap splice regions

which were formed at the story level with inadequate lap length may result in heavy damage

majorly at these zones. TEC (2007) recommends making lap splices in central zone of columns

(Figure 7). The splice length required in this state can be equal to the development length ℓb given

for tension bars in TBC-500 (2000). However, if more than 50% of lap splices were made in the

lower edge of a column, the splice length should be 1.5 times that of ℓb (TEC, 2007). Equation 1

shows development length (ℓb). However, equation 1 is valid for deformed rebars, whereas,

double this value should be used for smooth rebars (TBC-500, 2000). The author’s observations

suggest that the use of smooth rebar is very common in the region. Therefore, the splices made in

smooth rebar’s in the lower edges of columns were inadequate and could not provide adequate

anchorage. Figure 8.a. shows an example of column where smooth rebar was used as longitudinal

rebar and lap splices were made in the lower edge.

0.12 . 20ydb

ctd

f

fb 0 120.120 120.120 12 (1)

One of the reasons for damage to columns is the placement of hooks in longitudinal rebars. The

hooks in column rebars under the effects of compression increased the buckling tendency and

damaged the concrete cover. Figure 9 shows the hooks in longitudinal rebars of columns in

Gedikbudak Elementary School and in buildings in Zeylan Street in Erciş, respectively.

Beams

According to TEC-2007, beams are categorized as confinement zone and central zone, according

to transverse reinforcement (Figure 7). Beams were damaged in October 23, 2011 Van earthquake

because confinement zones were not created, transverse reinforcement’s hooks were 90o and

adequate anchorage length could not be provided. Bent-up longitudinal rebars were used in order

to help moment carrying capacity of supports and shear capacity of the beams (Figure 7). On the

other hand these bent-up bars cannot resist cylic shear forces (Arslan and Korkmaz, 2007). Figure

10.a. shows beam damage in Erciş bus terminal. As seen, a confinement zone was not created.

Figure 10.b. shows a building located in Erciş, in which a beam split from a column under tension

forces as a result of inadequate anchorage length in the lower rebar of the beam. Similar damage

was observed in beams during the Kocaeli Earthquake of August 17, 1999 (Sezen et al.,2003).

TEC (2007) specifies that, in cases where beams framing into columns are not extended to the

other side of columns, bottom and top beam reinforcement shall be extended up to the face of the

other side of the confined core of the column and then shall be bent 90o from inside the hoops. In

this situation, total length of horizontal part of longitudinal rebar inside column and its vertical part




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bent at 90o should not be less than the development length (ℓb) given in Equation 1. In addition, the

horizontal part (a) should not be less than 0.4ℓb and vertical part (b) than 12 (Figure 10).

Beam-column joints

Significant damage was observed in beam-column joints following the October 23, 2011 Van

earthquake as result of insufficient transverse reinforcement at the joint regions. TEC (2007)

categorizes column-beam joints as confined and unconfined in frame systems comprised of

columns and beams of high ductility level. In the case where beams frame into all four sides of a

column and where the width of each beam is not less than 3 / 4 of the adjoining column width,

such a beam-column joint shall be defined as a confined joint (TEC, 2007). Transverse

reinforcement spacing should not exceed 150 mm in confined joints and 100 mm in unconfined

joints. However, in beam-column joints within the earthquake region, confinement reinforcement

did not exist and beam longitudinal rebars anchorage in the joint is inadequate.

Strong beam-weak column effect

The first plastic hinge under earthquake effects is desired to occur in beams with better ductility,

due to their low axial load level, rather than in columns in order to ensure high energy absorption.

To that end, according to TEC (2007), in structural systems comprised of frames only or of

combination of frames and shear walls, sum of ultimate moment resistances of columns framing

into a beam-column joint shall be at least 20% more than the sum of ultimate moment resistances

of beams framing into the same joint. However, buildings which did not fulfill this provision and

in which deep beams were used together with flexible columns, suffered great damage in previous

earthquakes, leading to the loss of many lives (Adalier and Aydingun,2001; Wang,2008;

Dogangun,2004).

Figure 12 shows damage to 4 buildings following the October 23, 2011 Van earthquake as a result

of this mistake. In Figures 12.b. and 12.c., it can be clearly seen that the moment capacity of

beams are higher than those of columns. As a result, columns failed in the direction of weakest

flexural strength, as in Figure 12.a., some buildings collapsed like playing cards.

Pounding effect

Pounding between closely spaced building structures can be a serious hazard in seismically active

areas (Sharma,2008; Kasai and Maison,1997; Dogangun,2004; Xue,2000). During the earthquake

due to differences in dynamic properties of the adjacent buildings, structures hit to each other. If

the floors are not at the same elevation, floor of the one building damaged to the others columns.

This is known as pounding effect and during the October 23, 2011 Van earthquake lots of damage

occurred due to this undesirable incident (Figure 13). According to TEC (2007), the minimum gap




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between each building should be 30 mm for buildings up to 6 m and should be increased at least

10 mm for each 3 m height after 6 m. However if the value obtained by multiplying the sum of

absolute value of average floor displacement with coefficient α is higher than the value obtained

by the number of abovementioned floors, the greater spacing value should be used (TEC, 2007). If

all floor levels of adjacent buildings are the same then α = R/4, if any of the floor levels of

buildings are not the same then α is equal to R/2. In the equation, R represents structural behavior

coefficient, ranging between 3 and 8 depending on the ductility level of the system (high or

nominal).

Poor concrete quality

Although many causes of structural damage are discussed above, individually, none of them will

cause a building to totally collapse. Thus, the fact that some buildings with the same inadequacies

survived the earthquake with damage while others collapsed can be explained by poor material

quality. According to personal observation of the author in the region, concrete compressive

strength was observed to be much lower than 20 MPa value, the minimum value demanded by

TEC (2007). This assumption was verified by the results of strengths of concretes measured in

buildings that had completely collapsed. The concrete compressive strength of the examined

buildings ranged between 4.7 MPa and 15.6 MPa and the average strength was found 9 MPa

(Turkish Chamber of Civil Engineers, 2011). Similarly, according to studies in various regions of

Turkey, average concrete compressive strength was approximately 10 MPa (Arslan and Korkmaz,

2007; Inel et al., 2008). This low concrete strength exacerbated shear damage in columns and,

combined with factors such as the use of smooth rebar and inadequate development length, led to

adherence decomposition. Figure 14.a. shows the wreckage of a building that collapsed in Van city

center, killing 13 people. The wreckage resembles a sand pile, highlighting the poor concrete

quality. Other important factors include ignorance of aggregate gradation, using unwashed river

sand, and using aggregates sizes that are too large. Figure 14.b. shows an aggregate of 13 cm

diameter used in a building in Erciş. The observations from building rubble showed that most

rebars had corroded due to the use of river material and due to corrosion, thereby reducing the

efficiency of longitudinal rebar area and anchorage.

Architectural Factors

One of the reasons for the damage caused by the Van earthquake of October 23, 2011 is the short

column effect, which previous studies suggest is one of the most critical factors affecting the

seismic performance of buildings (Inel et al.,2008). In cases where infill walls or other non-

structural elements are constructed shorter than columns, the effective heights of columns

decreases and, in parallel with this situation, drift stiffness increases. Therefore, the column is

subjected to a shear force higher than that envisaged in the design stage. This is known as short




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column behavior and similar damage was observed in the October 23, 2011 Van earthquake

(Figure 15). TEC (2007), prohibits the creation of central zone in columns where short column

behavior might occur and requires the column to be surrounded by dense transverse reinforcement.

As stated in Part 4.1, one of the common implementations in Turkey is extending the plans with

overhangs above the ground storey for commercial purposes (as shown in Figure 5 and Figure 16).

Studies show that heavy overhangs negatively affect the seismic performance of buildings (Inel et

al.,2008). Concordantly, heavy cantilevers, which were not constructed appropriately, were

damaged in the Van earthquake of October 23, 2011 (Figure 16).

Unreinforced and unconfined gable walls

One common type of damage observed following the October 23, 2011 Van earthquake is out-of

plane collapses of gable walls under the roofs (Figure 17). The falling of the gable wall caused the

loss of life of a person in Van city center. In order to prevent damage to gable walls, the wall

should be surrounded by vertical and inclined bond beams over a certain height (Kamanli and

Balik, 2010). The masonry construction section of TEC (2007) specifies the use of vertical and

inclined bond beams where the height of a roof gable wall, which is set on the horizontal beam of

the top storey, is higher than 2.0 m. However, disregard of this construction regulation resulted in

damage during the Van earthquake, as in previous earthquake events (Dogangun, 2004).

Damage of Masonry Buildings During the October 23, 2011 Van Earthquake

General characteristics of the masonry buildings in the region

Buildings in rural areas of Turkey are generally of low-rise, non-engineered masonry building. It is

known that there are more than 4 millions masonry buildings throughout Turkey (Korkmaz et al.,

2010). Buildings of stone, briquette and adobe masonry, are commonly found in the Van region,

including in villages that suffered great damage and caused 66 people to die. In addition, mixed

type structures can be found, in which all materials are used together (Figure 18.b.).

Structural damages and causes of failures

Adobe masonry buildings

Observations made in the region showed that adobe buildings were damaged most among masonry

buildings. One of the main amendments to the previous TEC (1998) guidance (revised TEC

(2007)) in Turkey was the exclusion of adobe construction from earthquake code. The provisions

in the TEC (1998) code were removed because it is difficult to consider adobe buildings as




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engineered structures. Adobe structures can be considered as a special type (rural) of masonry

buildings. TEC (2007) is accepted to be valid for adobe buildings as long as they are provided with

necessary data for masonry structures section, which was revised comprehensively and which

includes dimension control and stress controls (Sucuoglu, 2006). The elements of adobe masonry

building are generally produced by drying the combination of clay mud and chaff, which are

poured into moulds of 30x20x10 cm sizes.

The walls of the building are built by bonding these adobe elements with clay mud; the bodies of

poplar trees growing in the region are placed onto these walls, the structure is covered with a soil

layer 30–40 cm thick and finished with a heavy roof (Celebi et al.,2011). Main factors causing

damage to such buildings include weather conditions, which reducing the strength of already weak

materials over time; heavy roof; lack of proper bonding between longitudinal and cross walls; and

poor workmanship. In addition, the roof shows non-rigid diaphragm characteristics due to its

inelasticity, which increased the out-of plane collapse of walls. Figure 19 shows damage to adobe

structures in Gedikbulak Village caused by such factors.

Briquette masonry buildings

It is clear that briquettes are commonly used in the earthquake region and these types of buildings

were also damaged. Cement-sand-lime mixture was used in the briquette elements and clay and

sand is commonly used as adhesive mixture in briquette buildings in rural areas (Celebi et

al.,2011). The damage was caused by reduced bonding over time due to weather conditions and

the absence of joints between walls. Additionally in Turkey, it is very common to use round

wooden logs (unshaped) as roof beams. Those beams are placed on two parallel walls. As a result

other two walls become unrestrained at the top (roof level). The damage is likely to occur for those

unrestrained walls. Figure 20 shows damaged briquette structures whose walls collapsed.

Stone masonry buildings

In eastern part of Turkey (and also Van region), one of the common masonry building type is

stone masonry. Especially random rubble stone is used and many structures incorporated timber

reinforcement and had timber roofs. As a mortar, mud is commonly used. After the mud

weakened, the only force that can withstand shear forces is the friction between stone blocks

(Korkmaz et al.,2010). This is the main reason for stone masonry building damages in Van

region (Figure 21). The load carrying timber most widely used in the roof was poplar. In some

stone buildings wooden roof beams are supported by vertical wooden logs (Figure 22). The

connections of column logs with roof beams are not adequate. The beams were supported on

columns which were flat topped or in a few cases hollowed out to form a saddle bearing surface.

In no case a rigid fixing mechanism between the columns and beams was observed.




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Damages due to liquefaction and lateral expansion

Another reason leading to damages in rural areas is liquefaction and associated lateral expansion

(ITU, 2011). Liquefaction was one of the causes heavy damages and loss of life in the Kocaeli

earthquake of August 17, 1999. A ground acceleration of 0.2g can begin liquefaction (Arslan and

Korkmaz, 2007). Therefore, as explained in Part 3, liquefaction potential was examined in the

regions where peak ground acceleration was predicted to exceed 0.2g. Settlement areas of Van are

known to have high liquefaction risk and liquefaction risk is known to increase in the nearby areas

of Lake Van (Ozvan et al., 2005). Damage related to liquefaction was not observed in Van city

center and Erciş district. However, sand piles and lateral expansion about 300 m was observed in

Çelebibağı village of Erciş, which is located in 3.0 km from Lake Van (Şekil 23). Single storey

houses constructed of adobe and briquette, and roads within the liquefaction area suffered great

damage (Şekil 21). In addition, liquefaction and lateral expansions were observed in villages and

fields surroundings these villages in Van plain (ITU, 2011).

Masonry minarets

Masonry minaret damages were also commonly seen in the earthquake region. Minarets are thin

and delicately constructed parts of mosques that are generally taller than the mosque with heights

of 15-40 m used to call people to prayer. Minarets have been constructed generally by workmen

without any project. Thus, most of them have been illegally constructed. Department of Religious

Affairs of Turkey explained report results for 1176 mosques under construction in Turkey after

August 17, 1999 Kocaeli earthquake that 80.9% of mosques did not have building license

(Dogangun et al.,2006). Most of the minarets damaged in the Van region have been constructed

using cut stone. It has been observed that the damages are more frequent at planes where the cross-

section weakens on the balcony parts of the minarets named as “şerefe” (Figure 24). Constructing

the minarets using reinforced concrete and limiting their heights so that they are not higher than

the closest building distance may be preventive measures to decrease the level of damage. TEC

(2007) does not include any section on minaret construction.

Results and Conclusions

Records for the earthquake (Mw=7.2) in Van, Turkey on October 23, 2011 show that 604 people

were died, 4152 people were injured, 2262 buildings collapsed and 4152 buildings were heavily

damaged. The reasons for structural damage and loss of life are poor material quality, insufficient

control mechanism, and pre-modern earthquake code, which was not effective in the period when

most of the buildings were constructed. The mistakes causing damage to R/C structures can be

listed as follows:




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The use of poor quality concrete with low compressive strength:

Producing concrete on the site by workers,

Use of high water/cement ratios for workability,

The use of inappropriate grain size and the use of only river gravel in the production

of concrete.

Insufficient vibration and curing of concrete

Design and detailing not in pursuant to ductility requirements and TEC (2007):

Inadequate transverse reinforcement in column, beam, and joint regions,

Design of beams that were stronger than columns,

Making 90o hooks in transverse reinforcements instead of 135o,

Making hooks in longitudinal rebars used in columns,

Architectural design mistakes:

Adjacent buildings and the absence of adequate gaps,

Soft and weak storey effect,

Short column effect,

Heavy and unqualified overhangs,

The absence of connections between roof gable walls and structure

The mistakes causing damage to masonry structures can be listed as follows::

Weakening of materials use in masonry structures over time due to weather conditions,

Constructing masonry structures in traditional style without complying with construction

techniques and rules,

Heavy roofs,

Lack of proper bonding between longitudinal and cross walls.

While existing structures that comply with current Turkish earthquake codes provide a certain

level of security, each earthquake causes great losses of lives and property due to the large

numbers of structures built pursuant to previous codes. The existing building stock should be

quickly evaluated, and structures with inadequate seismic performance should be strengthened and

new and secure settlement areas should be established with government support in regions that are

at high risk of earthquakes. In addition, construction control mechanism should be increased in

rural areas and masonry structures should be built according to the provisions of the code rather

than traditional styles.




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Acknowledgements

The author thanks Özkan Atan for their help during examinations in the earthquake area.

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List of Figures

Figure 1 General tectonic setting of Turkey (Adapted from Karagoz,2008)

Figure 2 Distribution of aftershocks in Van and its surroundings as of 10 November

2011 (EMSC, 2011)

Figure 3 Ground motion acceleration components obtained at Muradiye Station

Figure 4 Various attenuation relations and the calculated values of PGA for the seismic

activity

Figure 5 Typical R/C frame building in Van region

Figure 6 Collapsed ground storey in Erciş (soft storey mechanism)

Figure 7 Beam, column and joint details

Figure 8 Columns failure with buckled longitudinal rebars and opened ties

Figure 9 Views of hooks used at compression rebar

Figure 10 Damaged beams

Figure 11 Failure of beam-column joints

Figure 12 Strong beam-weak column failures

Figure 13 Pounding effect for adjacent building

Figure 14 Building wreckage resembling a sand pile and an aggregate sample used in

concrete

Figure 15 Short column failure due to infill wall

Figure 16 Heavy and statically unsuitable overhangs

Figure 17 Falling down of gable walls during October 23, 2011 Van Earthquake

Figure 18 Masonry buildings in Van region (a) Adobe masonry building (b) Mixed

type stone-adobe building

Figure 19 Typical damages of adobe masonry buildings

Figure 20 Briquette masonry building damages




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Figure 21 Collapse of stone masonry building in Erciş

Figure 22 Wooden frame of stone building in eastern Anatolia (Hughes, 2000)

Figure 23 Observed lateral expansions in Çelebibağı village and associated damages

Figure 24 Masonry minarets in Van




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Accepted Manuscript Not Copyedited




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Table 1. October 23, 2011 Van Earthquake characteristics

Agency Epicenter Latitude

Epicenter Longitude

hhypo

(km) Mw ML

AFADa 38.689 43.465 19.02 - 6.7KOERIb 38.758 43.360 5.00 7.2 6.6USGSc 38.691 43.497 16.00 7.1 -EMSCd 38.86 43.48 10.00 7.2 -

a Turkish Prime Ministry-Disaster and Emergency Management Agency. b Kandilli Observatory and Earthquake Research Institute. c United States Geological Survey. d European-Mediterranean Seismological Centre.





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Table 2. Previous earthquakes in and around Van (Adapted from Imamoglu and Cetin,2007)

Date Latitude Longitude Location and affected area Magnitude Intensity

1245 38.74 42.50 Ahlat, Van, Muş - VIII 1276 38.90 42.90 Ahlat,Erciş,Van - VIII 1363 38.70 41.50 Mus and its vicinity - VIII 1441 38.35 42.10 Van,Bitlis,Muş - VIII 1582 38.35 42.10 Bitlis and its vicinity - VIII

02.04.1647 39.15 44.00 Van,Bitlis,Muş - IX 1715 38.70 43.50 Van, Ercis - VIII 1869 38.40 42.10 Bitlis and its vicinity - VI

05.03.1871 38.50 43.40 Van and its vicinity 5.5 VII 30.05.1881 38.50 43.40 Van,Bitlis,Muş 7.3 IX 10.02.1884 37.80 42.60 Pervari,Siirt 6.1 VIII 28.04.1903 38.70 41.50 Malazgirt,Muş 6.7 IX 06.05.1930 - - Hakkari 7.2 X 10.09.1941 38.70 43.50 Erciş,Van 5.9 VIII 29.07.1945 38.50 43.40 Van and its vicinity 5.8 VIII 16.07.1972 38.50 43.40 Van 5.2 VII 24.11.1976 39.10 44.00 Çaldıran, Van 7.2 IX





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Table 3. Important properties of the processed records (Adapted from METU and AFAD,2011)

Station Information Repi

(km) RJB

(km)

PGA (cm/sn2) Name Latitude

(N) Longitude

(E) NS EW UD

Van-Muradiye Station 38.990 43.768 46.63 19.51 178.55 169.45 79.15 Muş-Malazgirt Station 39.143 42.530 93.26 74.25 44.30 55.75 25.52 Bitlis-Center Station 38.474 42.159 111.75 82.82 89.66 102.22 35.50 Ağrı- Center Station 39.719 43.015 121.83 114.01 18.33 14.89 7.15 Siirt- Center Station 37.931 41.935 153.36 124.48 9.67 9.12 6.94 Muş- Center Station 38.761 41.503 166.54 138.22 10.32 7.08 4.66





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Field Reconnaissance of the October 23, 2011, Van, Turkey, Earthquake: Lessons from Structural...

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