Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanDAMAGE ANALYSIS ON BUILDINGS IN TOWNS ANDVILLAGES AROUND THE JUNCTION AREA OFSICHUAN AND GANSU IN WENCHAUN
EARTHQUAKEBo SONG1, Fuqiang QI2 and Shuai HUANG3
1Professor, Department of Civil Engineering, University of Science & Technology Beijing,
Beijing, China, songbo@ces.ustb.edu.cn
2Doctor degree candidate, Department of Civil Engineering, University of Science & Technology
Beijing,Beijing, China, safety-star@163.com
3Doctor degree candidate, Department of Civil Engineering, University of Science & Technology
Beijing,Beijing, China, huangshuai28@yahoo.cn

ABSTRACT: Based on the site investigation of building damage in towns and villagesaround the junction area of Sichuan and Gansu province caused by Wenchuan earthquake
in 2008, the damage characteristics of buildings are studied and the damage phenomena
are analyzed in the paper. Considering the construction situation of buildings in towns
and villages in China, the key issues about seismic design of building are discussed andseveral seismic fortification measures and suggestions on seismic design of buildings intowns and villages are proposed.
Key Words: Wenchuan earthquake, buildings in town and village, damage phenomena,
seismic design

Introduction
On May 12, 2008, an Ms 8.0 earthquake occurred in Wenchuan, Sichuan province, China. Until May
27, 67183 people were killed, 361822 people were injured, and all kinds of buildings, especiallybuildings in villages and towns were damaged seriously. Since the earthquake occurring in a
mountainous region of Western China, the earthquake presents many new damage characteristics ofbuildings in towns and villages, which brings many new problems to earthquake disaster prevention
and mitigation.
Since the focal depth of the earthquake is only 10 to 20 kilometers, the earthquake belongs toinland shallow earthquake. The released great energy was widely spread by seismic waves, and theearthquake was felt in most of provinces and cities of China, such as Beijing, Gansu, Guizhou,
Ningxia, Shanxi, Shanxi, Henan, Hubei, Shanghai, etc. Because Gansu province is close to theSichuan province, the earthquake disasters were very serious. In the present paper, based on site

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investigation on the buildings in towns and villages in Longnan city, which is situated in the junction
area of Sichuan and Gansu province, the damage characteristics of buildings are studied.

Fig.1 The geographic position of Longnan city
Longnan city is about 200 kilometer far away from Wenchuan, as shown in Fig.1. The seismic
fortification intensity of Longnan city is 8 degrees and the design earthquake acceleration is 0.20g,
which is equal to the intensity of Wenchuan earthquake. The typical building damages in towns andvillages in Longnan city were analyzed in the paper.
Earthquake damage investigation of buildings in Longnan, Gansu province
In the site investigation of building damages, more than hundreds of residence buildings and 99 publicbuildings were investigated. In the mountain area, most residence buildings were made of raw-soil
structure buildings, timberwork buildings, bricks timberwork buildings and masonry concrete
structures and so on. The investigated public buildings were main irregular structure buildings andlarge span structure buildings. The raw-soil structure buildings and timberwork buildings weredamaged seriously, and the heavy damaged buildings accounted for 78%. The main support walls
collapsed, wooden frames collapsed and tilt, the transverse and longitudinal joints of wooden frame
loosed, tenon structures were damaged seriously, and the span purline and tile of roofs felled down.
The masonry concrete structures without constructional column were also damaged seriously,
especially the ground floor, where the walls were shear failure, containing diagonal cracks, ‘X’ form
cracks and horizontal cracks. The masonry concrete structures of large span multi-ribbed slab frame
structure were also damaged seriously. Although obvious cracks on most of the reinforced concrete
structures can not be seen, the damages were obviously on non-structural bodies such as infilled wall.
The raw-soil structure buildings and timberwork buildings
The raw-soil structure buildings and timberwork buildings were the main types of buildings in towns
and village, which were basically built before 1970s with single layer and the beams were placed on
the walls directly. So the type of buildings were designed without considering aseismic ability anddamaged seriously during the earthquake as shown in Fig.2 and Fig.3. Because the raw-soil structurebuildings are weak in integrity, if there are not connected structures between the walls, the buildings
will be easy to crack and collapse subject to horizontal seismic forces. Though it is specified that thejunctions of outer wall and inner wall should set a layer of bamboo muscle, batten and so on, in designof raw-soil structure buildings in Code for Seismic Design of Building (GB50011-2010), the damagedbuildings were lack of connection structures, even some buildings were without foundations, the walls
were too high and the span were too large comparing with the specifications in the code on the site
investigation. So the raw-soil structure buildings collapsed because the shaking crack was too large inthe earthquake. The purline and crossbeam were set on the wall directly, and they were not subject toconcentrated loads. Because the strength of walls was insufficient, the walls always crack in using. Sowhen the earthquake occurred, the purline and crossbeam collided with walls, which caused the cracks

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The main problems of timberwork buildings were that the components corroded and decayed, thesection of timberwork weakened, the strength of components connection was insufficient, and thefloor height was too high. The important reasons of buildings in towns and villages collapsed in theearthquake were that the building were not designed according the seismic design codes and thebuilding materials did not meet the requirements. So in high seismic fortification intensity town area,
it is important to strengthen the legality of building construction and the supervision to improve thequality of buildings.

Fig.2 The collapsed timberwork buildings

Fig.3 The collapsed raw-soil structure buildings

The masonry timber buildings
Besides the raw-soil structure buildings and bricks timberwork buildings, masonry timber buildings
are also another common type of local dwellings houses. The main support wall were most brick wallswith thickness 120mm, 180mm or 240mm, and the roof were triangle wooden frame. The masonrytimber buildings were designed without seismic measures and lack of connection components, and theroof trusses were installed on the brick wall directly, so the type of the buildings were always with badintegrity. Under vertical loads, the structures usually relative stable, but subject to horizontal
earthquake, the maintenance walls were easy to incline, which leads to severe earthquake damage suchas local collapsed or overall collapse. In the earthquake, most masonry timber buildings were damaged
seriously and some buildings built relative early completely collapsed as shown in Fig.4. The masonrytimber structures have the same problems with the raw-soil structure buildings, such as the purline puton the brick wall directly. The improper constructions and connections made the masonry timber
structures loss the aseismic ability.

Fig.4 The destroyed masonry timber buildings
The masonry concrete buildings
The masonry concrete buildings were a new type of buildings adopted by local residents in recentyears, most of which were with two layers. The buildings usually set ring beams at the ground and at
top of first floor, but rarely at the top of second roof, and did not set constructional columns. In theearthquake, the damages of the type of buildings contain cracks on the walls, damage at the connectionof vertical walls and horizontal walls, damage at doors and windows, walls incline and collapse and soon. Some buildings adopted the improper force transmission structures, which caused some buildings
were damaged seriously as shown in Fig.5. It can clearly be seen that the second layer column was cutoff. The loads acting on upper layer column can not transfer to the foundation via a proper force

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transmission path, but directly acted on the lower beams, which caused big concentrated forces and‘X’ form cracks on masonry structure under the beams. The second layer bearing structures were equal
to three large bays, and the walls between windows of the three large bays were damaged with ‘X’form cracks. The irregular structures are easy to be damaged in an earthquake, so it should be avoided
in the design.

Fig.5 The building with improper force transmission path
The irregular buildings
Irregular construction was one type of the seriously damaged buildings in the earthquake. In order toget the novel appearance, many buildings adopted the irregular construction shape, such as split-levelbuilding, plane protruding building, and so on. Due to the force transmission pass abrupt change, thechange points of the structure are easy to be damaged and lead to the damage of the whole building
during an earthquake. The Fig.6 shows a meteorological agency building whose main structures are
three layers and local structures are four layers. The three layers part and four layers part wereconnected together without setting aseismic joint, which leads the top column completely fracture asshown in Fig.6. The top floor of another irregular building was also badly damaged, shown in Fig.7 (a),and the change point of a building cracked in the earthquake, as shown in Fig.7 (b). Because ofimproper design, the plastic hinges occurred at the end of the columns of irregular building structuresin the earthquake, shown as Fig.8. The building damages showed the phenomenon of ‘strong
beam-week column’, which is opposite with the design goal of ‘strong column-weak beam’.

Fig.6 the damages of Meteorological Bureau building in gansu province(a) Irregular building in planar direction (b) Irregular building in planar direction and façadeFig. 7 The damaged irregular buildings

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Fig.8 The phenomenon of ‘strong beam-week column’The school buildings with large spans
In the investigation of building damages, the large span buildings were also damaged seriously. TheLongnan middle school building was an octagonal masonry concrete structure with four floors. The
destruction features of the school building with large span showed that the vertical wall of theclassroom with cantilevered corridor in one side occurred ‘X’ form shear cracks, as shown in Fig.9.
The cross wall of large span classroom occurred diagonal cracks, which was about 45 degrees, asshown in Fig.10.

Fig.9 The ‘X’ form shear cracks of vertical wallFig.10 The diagonal cracks of cross wall

Seismic damage analysis on buildings in towns and villages
Site investigation also showed that improper location was an important reason of buildings damaged in
the earthquake. A large number of buildings were built in bad geological location, such as slope
surface area formed by landslide and debris flow as shown in Fig.11.

Fig.11 The buildings built on landslide zone
The local buildings were designed considering the proper location little, such as themeteorological agency shown in Fig.6, was built on a raised soil, which is 50 meters higher thannormal ground. The raised soil has a magnifying effect on seismic responses and the magnifying
coefficient can be 1.3-1.5. So the building was damaged seriously not only in the irregular point andbut at another side of the building which is shown in Fig.6. So the improper location will bring great
hidden dangers to buildings, and it should be avoid in building design.

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In the earthquake, some buildings were seldom damaged since the adopting of seismic measures.
The Fig.12 provided by Gansu civil engineering science research institute shows an apartmentbuilding which adopts rubber bearing shown in Fig.13. There did not present any cracks in theapartment building, and also the vase on the air conditioner did not fall. It showed that the proper
isolation measures are an effective way to improve the aseismic ability of buildings.

Fig.12 The building with rubber bearing

Fig.13 The rubber bearing

Recommendations on design of buildings in towns and villages
Because of relative lagging economy, the countryside buildings had some problems of building
materials, structural styles and traditional customs, which made the casualties and damaged building invillages more serious than that in cities. Through the survey, we found that adopting proper structural
measures in countryside buildings is an effective way to mitigate the building damage in 6 degrees and7 degrees fortification area, for reinforce concrete frame structures.
For raw-soil buildings and timberwork buildings, it is necessary to strengthen the integrity ofbuildings and the connection of components. And all of the used irons, clinchers, straws and wooden
poles only value 2%~5% of the total cost of buildings. Especially for timberwork buildings, walls andtimber structures should connect reliably, and the masonry walls should not completely surround thewood column and should be built outside of the column. (Ge, 2005, Wang, 2004, etc)
For masonry structures, the proper constructional columns and ring beams are necessary. Thequantity and position of constructional columns should be proper, and avoid the following cases, thelongitudinal bars of the constructional columns in building nooks insufficient, the anchorage length of
longitudinal bars of constructional columns and ring beams insufficient, the stirrup of constructional
columns at the position of up and down the floors not encryption, the anchorage length of steel tie bars
between constructional column and brick walls insufficient or the spacing improper.
The stairway is the part suffering earthquake seriously of the masonry structures and the aseismic
ability of stairway is week. So the stairway must be set properly. According the Code for Seismic
Design of Building (GB50011-2010), the stairway can not be set in end and nook of the building, also
can not set too large window. It should strengthen the connection of each component, and well dispose
the relation of nonstructural components and major structure. For constructional column setting,according its influence on integral structure, it can set the four corners of the building as first class, thefour corners of the stairway as second class, and the junction of inner walls and outer walls as the thirdclass. The roof house and additional structures protruding the roof should be paid more attention.
Because of the influence of ‘whipping effect’ in an earthquake, the structures protruding the roof arealways damaged more seriously than the lower major structures. So, unless special requirements andadopting reliable measures, the protruding structures should be avoided in design (Tang, 2007).
For reinforced concrete structures, adopting proper structural measures can ensure that the parts
where likely occur plastic hinges will have enough ductility, that is to say, the structures have enoughplastic rotational capacity and plastic energy dissipation capacity. For beams, we always expect thatthe plastic hinges occur at the end of beams, so we should ensure the beam end with good ductility andenergy dissipation capacity in design. Except meeting some requirements for calculation, it also needs
set a series of structural measures, such as controlling the ratio of reinforcement, the beam with acertain number of compression reinforced bars, the proper quantity and usage of stirrups and the well1899

designed sectional dimensions of beams. The structural measures of columns are basically the same as
the beams. But the columns not only bear the flexural moments and shear forces, also endure the axialforces, so there are sill requirements for ratio of axial compressive force to axial compressive ultimate
capacity of section. (Zhong, 2008, Yu, 2008, etc)
For new structural system, performance-based seismic design (PBSD) should be used.
Accompanying with development of PBSD, the building design should meet the requirements for
multistage seismic design, shown as Fig.14. The mechanical properties of large complex structures
should be determined by using time history seismic analysis and the complex structures should designby using performance-based seismic design method to control the position of the major structure
where plastic hinges occur and the precedence of plastic hinges.
P

H ○
1 ○
23○

4○

Safety standards
Hmax
0.95HmaxH(δ)
FailurehHyδmax/δy4.0 δu/δy

1.0 1.7

Residual deformation=H/300

δ

Residual deformation=1/100

Fig. 14 The multistage seismic design
Conclusions
Combining with the damage characteristics of buildings in towns and villages at the junction areas ofSichuan and Gansu in Wenchuan earthquake, the key points on aseismic ability of buildings werediscussed and the following recommendations were made.
The site selection of buildings should avoid bad geological location, such as landslide, dilapidation,
subsidence, river valley edge, ground fracturing debris flow and seismogenic zone. The foundation
should be reinforced according the bearing capacity, deformation characteristics and structuralcharacteristics of buildings to ensure that the building will not be damaged due to instable foundation.
Considering the economy, buildings in towns and villages can be constructed with different grades
and levels. In a certain period, raw-soil structure buildings can still be the main residence houses, withthe economy developing, brick buildings should be encouraged to be built. And irregular structures
also need to be avoided and set proper constructional column and ring beam to strengthen the seismic
capacity of buildings.
The construction of town buildings should be more standardized, and all of the design,construction and supervision should be paid more attention and ensure that they meet the requirementsof the related laws and regulations.
For the countryside buildings, we should analyze the characteristic of seismic damage, and adopt
some simple and effective construction measures to improve the aseismic ability of buildings
considering construction cost. It also needs to propose seismic strengthening methods suitable tocountryside buildings to mitigate the earthquake damage of old buildings.
References
Ge Xueli, Wang Yayong, Shen Shiyuan, Zhang Haiming (2005). “Seism disaster of building in ruralarea as well as measures of anti-seism and disaster a11eviation”. Construction of Towns & Villages,No. 12, 671-674.
Hu Xiaopeng, Xu Lei, et al (2008) “Wenchuan 8.0 earthquake damage of single-storey industrial plantanalysis”. Journal of Xi’an university of architecture& technology, Vol. 40, No.5, 662-666.

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Li Yingmin, Han jun, et al (2009) “Investigation and analysis of masonry building damage caused by
the 5.12 Wenchaun earthquake, Sichuan Province”. Journal of Xi’an university of architecture&technology, Vol. 41, No.5, 606-611.
Tang Qushi (2007). “Main Earthquake Damage Characters and Earthquake-resistant Design ofMasonry Structure”. Science and technology of overseas buildings materials, Vol. 28, No.6, 71-73.
Wang Yayong, Yue Maoguang, et al (2008). “Benefit analysis of RC structures designed under
different performance objectives”. China civil engineering journal, Vol. 41, No. 3, 37-44.
Wang Yihong, Jiang Jianfei, Shi Jian, Chi Jiaxiang (2004). “Earthquake-resistance Performance andProtective Measures of the Timber Structural Buildings”. Earthquake Resistant Engineering andRetrofitting, No. 5, 47-51.
Ye Lieping, Lu Xinzheng, et al (2008) “Damage analysis on buildings in Wenchuan earthquake”.
Seminar on building damage analysis and reconstruction in Wenchuan earthquake, Vol. 1, 38-49.
Yu Wen, Ge Xueli, et al (2008) “Damage analysis on buildings in towns and villages aroundDujiangyan of Wenchuan Ms 8.0 earthquake”. Earthquake resistant engineering and retrofitting,Vol. 30, No.4, 45-49.
Zhong Min, Song Bo(2008) “The experience of Sichuan earthquake on urban disaster prevention andmitigation”. Seminar on building damage analysis and reconstruction in Wenchuan earthquake,Vol. 1, 623-630.

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