emerald _ earthquake safety elements in traditional koti banal architecture of uttarakhand, india

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Disaster Prevention and Management

Article Information: Earthquake safety elements in traditional Koti Banal architectureof Uttarakhand, India

References: 9

To cite this article: Piyoosh Rautela, Girish Chandra Joshi, (2009) "Earthquakesafety elements in traditional Koti Banal architecture ofUttarakhand, India", Disaster Prevention and Management,Vol. 18 Iss: 3, pp.299 - 316

To copy this article: [email protected]

Downloads: The fulltext of this document has been downloaded 372 timessince 2009

The Authors

Piyoosh Rautela, Disaster Mitigation and Management Centre, Department of Disaster Management,Government of Uttarakhand, Uttarakhand Secretariat, Dehradun, India

Girish Chandra Joshi, Disaster Mitigation and Management Centre, Department of DisasterManagement, Government of Uttarakhand, Uttarakhand Secretariat, Dehradun, India

Acknowledgements

The authors are thankful to Shri Subash Kumar, Principal Secretary, Disaster Management, Government ofUttarakhand for support, guidance and encouragement. Dr C.M. Nautiyal of Birbal Sahni Institute ofPalaeobotny, Lucknow is thanked for radiocarbon dating of the samples. Financial support for the study fromDisaster Risk Management Programme of Ministry of Home Affairs (MHA), Government of India and UnitedNations Development Programme is gratefully acknowledged.

Abstract

Purpose Despite being located in earthquake sensitive region and often experiencing seismic tremors theState of Uttarakhand in the Indian Himalayas exhibits an elaborate tradition of constructing multistoreyedhouses. Both the local dialects of the State (Kumaoni and Garhwali) have unique words for identifying fourdifferent floors of a building. This is suggestive of a common occurrence of multistoreyed structures in theregion. This paper attempts to establish that the people inhabiting this rugged earthquake prone terrain haveevolved the art of constructing earthquake safe structures well before the evolution of the structuralengineering principles governing such a construction.

Design/methodology/approach Detailed investigations were undertaken in the area to establish theantiquity of the traditional structures, as were also earthquake safety provisions incorporated traditionally inthese. Radiocarbon dating of the wood used in the structures was used to establish the time of the

construction of these structures.

Findings Investigations suggest that the region has evolved a distinct, elaborate and magnificentearthquake-safe construction style. This construction style, designated Koti Banal architecture, attained itszenith around 880 years ago. This architectural style exhibits the existence of elaborate procedures for siteselection, preparing the platform for raising the multistoreyed structure, also for the detail of the entirestructure that was constructed on principles somewhat akin to that of framed structures of modern times.

Research limitations/implications The representative structures of this architecture are observed to bedeteriorating fast due to lack of patronage, resources and awareness. This article brings forth awarenessregarding the heritage value of these structures, enabling organized efforts for the conservation and upkeepof these structures.

Originality/value This article is the result of original research undertaken by the authors and paves theway for the conservation of the age old traditional structures.


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Article Type: Research paperKeyword(s):Earthquakes Structural engineering Architecture India.Journal: Disaster Prevention and ManagementVolume: 18Number: 3Year: 2009pp: 299-316Copyright Emerald Group Publishing LimitedISSN: 0965-3562

The hazard prone terrain

Subduction of the Indian Plate beneath the Eurasian Plate and its consequent collision with the same afterthe consumption of the intervening oceanic crust resulted in the evolution of the Himalayan mountain belt.The plate collision has rendered the terrain highly fragile and prone to mass wastage. The north-northeastward drift of the Indian Plate has not yet seized and ongoing built up of strain due to this movementis responsible for frequent seismic tremors in the region.

Entire Himalayan terrain is recognized as being highly vulnerable to earthquakes (Bilham et al., 2001 Feldland Bilham, 2006) and in the past the region has been jolted by four Great Earthquakes (Magnitude > 8 onRichter Scale) 1897 Shillong Earthquake, 1905 Kangara Earthquake, 1934 Bihar-Nepal Earthquake and 1950

Assam Earthquake apart from Kumaun Earthquake of 1720 and Garhwal Earthquake of 1803 (Thakur, 2006).Regions between the rupture zones of the Great Earthquakes are recognised as seismic gaps that areinterpreted to have accumulated potential slip for generating future Great Earthquakes. Entire State ofUttarakhand falls in the seismic gap of 1934 Bihar -Nepal Earthquake and 1905 Kangara Earthquake and iscategorized as falling in Zone IV and V of the Earthquake Risk Map of India (Vulnerability Atlas of India,1997). This region has been identified as a potential site for a future catastrophic earthquake (Bilham et al.,2001). The region has also witnessed seismic events of lesser magnitude (1991 Uttarkashi Earthquake, 1999Chamoli Earthquake) and unplanned growth, concentration of population and infrastructure, negligence ofconstruction norms, abrupt change in construction material without appropriate technical interventions andlack of awareness as also trained manpower further enhance seismic vulnerability of the region.

Earthquake safety and traditional construction practices

Human response to emerging exigencies has resulted in fine tuning of resource management practices asalso life support strategy, so as to protect the interests of the human communities. Based upon experience,experimentation, accumulated knowledge and ingenuity human populations around the globe have thusevolved innovative practices for ensuring survival against all odds and survival and supremacy of therelatively unspecialized species testifies this fact.

Communities residing in areas often affected by earthquakes were quick to grasp the fundamental premise ofearthquake safety that states structural safety to be the key to avoiding loss of human lives in aseismogenic event. This fundamental understanding led to the evolution of innovative practices forminimizing human losses emanating from structural collapse. Dhajji-dewari and Taq are the famousindigenous construction styles of Kashmir that utilize locally available stone and timber in a particular mannerto achieve desired levels of seismic safety. Quetta bond is another example of human quest to reduce

earthquake induced losses.

The State of Uttarakhand falls in seismically highly sensitive zone and has witnessed devastatingearthquakes in 1720 (Kumaun Earthquake) and 1803 (Garhwal Earthquake). Despite often experiencingearthquakes (Chalak in Kumaoni the local parlance) multistoreyed houses are common in the region and it isnot be easy for one to locate a single storeyed traditional house in the region even today, except for cattlesheds (channi in Kumaoni the local parlance). There exist unique words for identifying as many as fourdifferent floors in the two local dialects of the region Kumaoni (ground floor, goth first floor, chaak secondfloor,paan third floor, chaj) and Garhwali (ground floor, kholi first floor, manjua second floor, baund thirdfloor, baraur). Unless often required a unique term cannot be introduced in any language. This clearly pointtowards common occurrence of multistoreyed houses in the region.

The zeal to avert earthquake induced losses, by utilizing accumulated knowledge of generations and

experimenting with locally available building material, paved way for the evolution of a unique architecturalstyle that exhibits structural evolution trends whereby dry stone masonry, as also stone lime/mud/claymortar masonry was judiciously used with abundantly available wood to provide appropriate strength and
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flexibility to the structures.

In Yamuna and Bhagirathi valleys of the Garhwal region four to five storeyed traditional structures can still beobserved (identified as Chaukhat four storeyed or Panchapura five storeyed). These age old structuresmust have witnessed many earthquakes and in the absence of the elements of earthquake safety these

would have long been razed to ground.

Though not suited to the climatic conditions, cement based construction practices are fast getting popular inthe region. High social status attached to the new type of construction together with increasing difficulty inmustering traditional building material have contributed to its popularity. As has been indicated (Rautela etal., 2007) demand is forcing untrained/inadequately trained masons to take up cement based construction

works which adds to the seismic vulnerability of the region.

Survival of the traditional structures over generations in the earthquake prone terrain is suggestive ofincorporation of elements of earthquake safety in these. In depth investigation of these buildings have thepotential of unfolding hitherto unknown facts about this particular construction style and innovating upontraditional practices one can evolve a better suited construction dictum for the region.

Rajgarhi area, to the north of Barkot across river Yamuna in Uttarkahi district of Uttarakhand ( Figure 1) has alarge number of intact multistoreyed traditional structures (Plate 1) in a number of villages (Dakhiyatgaon,Guna, Koti Banal, Dharali) in close proximity. This area was therefore selected for detailed investigations. Astructured questionnaire was prepared to assess the perception of the masses towards structural safety

related aspects as also their tradition. Detailed field investigation was resorted to for assessing the structuralsafety related aspects of this construction style.

Perception of the masses

Traditional practices of resource management reflect the community's resolve to safeguard its interests andthese often draw strength for their continuation from religio-magical rites that are imbibed deep in popularbelief. Continuation of these practices over generations indicate benefits drawn by the community by actingupon these. Insight into the popular belief and practices of the masses are therefore perceived to be the toolsfor assessing the strength of their traditional knowledge base.

The respondents

In order to assess the status of traditional practices relating to earthquake risk management people wereinterrogated with the help of a structured questionnaire prepared in vernacular that was also intended to beutilized for assessing the level of awareness of the masses on disaster related issues. Every effort wasmade to have representation of every section and group of the community and 50 persons were interrogatedin detail in five villages in Rajgarhi area. As agriculture is the mainstay of the economy of the area, most ofthe interrogated persons engage in agrarian pursuits. The age of the respondents varied between 21 and 81years with a large proportion of the respondents (32 percent) falling in the age group of 40-50 years. Rampantilliteracy in the region is reflected in the low literacy levels of the respondents with 44 percent being illiterateor educated to primary level.

Earthquake safety features

Earthquake emerged as the major concern of the masses (90 percent) while landslide and flood accountedfor the rest. Half the respondents rated the level of the perceived as threat being high while 34 percent ratedthis as being severe. Most respondents were proud of the rich architectural tradition of their region that isvisually appealing and magnificent. Unlike inhabitants of the areas that have witnessed loss of traditionalhouses due to earthquakes in the recent past (Uttarkashi 1991 and Chamoli 1999) most respondentsconsider traditional houses to be safer than the modern houses constructed with cement (Rautela et al.,2007). This suggests that the popular attitude can change in short time period when their beliefs prove to be

wrong. Most persons believe earthquake safety to be a cornerstone of the traditional construction practicesbut most (92 percent) could not pinpoint particular earthquake safety related feature of the traditionalstructures. Appropriate site selection and judicious use of wood together with the stone-wood bondingtechnique used in traditional buildings were perceived to provide the required levels of strength to these

structures.

Site selection
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As has also been revealed in the studies carried out in other parts of the State (Rautela et al., 2007) the areaunder consideration exhibits an elaborate tradition of site selection and most people still believe in itsauthenticity. Selection of stable and flat land is cited as the primary criteria for site selection. Local priest isgenerally consulted for ascertaining the suitability of the site selected for construction purposes. Majority (42percent) holds that the advice is based on the observation of the soil of the proposed construction site.Inspection of the construction site (30 percent) and personal experience (20 percent) are considered to beother criterion for extending this advice. Six percent of the respondents believe the advice to be based onastronomical calculations. It seems that some persons based upon their experience and accumulatedknowledge could assess and comment upon the bearing capacity of soil by examining soil texture, moisture

content and the other related features. This technique needs to be studied, documented and propagated (withnecessary improvements where necessary). This would pave way for developing a quick and cost effectivesite selection methodology.

Foundation

The houses in the area are mostly observed to be constructed on a raised and elaborate solid platform (Plate2) that adds to the stability of the structures by keeping the centre of gravity of the entire structure near theground. This practice has perhaps resulted in the masses not paying much attention on the detailing of thefoundation which is reflected in the response of the people. Of the respondents, 60 percent said that thedepth of foundation varied between 2-3ft. Unlike in other areas, construction is resorted to even if solid rockdoes not appear at the proposed construction site. People at the same time do not maintain long time gap

between digging up of foundation and construction of the structure as is in vogue in most other areas of theState.

Seismic vulnerability and safety related aspects

Even though the area was jolted by Uttarkashi Earthquake of 1991 the masses do not seem to have any ideaof differential vulnerability and majority (56 percent) said that all the houses would suffer equally in the eventof an earthquake. All the respondents remembered there area being affected by the earthquake in the past(that caused some damage to the dwellings) but only 56 percent could recall the year rightly. This might beowed to not so severe impact of the event in the area.

Most respondents (80 percent) consider good masonry work as the cornerstone of seismic safety. The restwere divided over site selection and detailing of the foundation. Most respondents agreed that strong and wellconstructed structures would minimize the losses likely to be incurred in the event of an earthquake. Therespondents seemed to have heard of earthquake safe construction technology and they expressed

willingness for spending a bit more for warding off the threat of their dwellings crumbling due to earthquake.

Masons

Traditional masons are preferred for construction works in the region. Familiarity with these masons apartfrom trust reposed on them, their knowledge and experience together with their cheap and easy availabilityare cited as the reasons for preferring them. It is hard to believe 67 percent of the respondents who assertthat earthquake safe construction related knowledge of the masons is a consideration for entrustingconstruction work. All the respondents agreed that the masons with knowledge of earthquake resistantconstruction would be preferred and would therefore get more employment and wages.

Traditional structures

The area has tradition of erecting elaborate and magnificent multistoreyed houses that are locally identifiedas Chaukhat. This term is however used for four storeyed houses that are quite common in the region fivestoreyed being identified as Panchapura. Masses in their local parlance (Garhwali) use different words toidentify different floors of the house (ground floor, kholi first floor, manjua second floor, baund third floor,baraur). This suggests common occurrence of multistoreyed houses in the region. Corrosion of the stone and

wood used in the building is indicative of the antiquity of these structures. The respondents were howeverdivided over the time of construction of these structures.

Though majestic and visually appealing these multistoreyed houses were not spacious these mostly have

one single room on each floor towards the rear side of the structure with a small area in the front beingutilized for placing wooden log with carved footholds for providing access to the subsequent floor. The twoareas are divided by a wall. The upper two floors have external balcony and the roofs of all the floors are not
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comfortably high. The kitchen is generally located in the top floor of the structure.

The purpose of constructing these not so occupant friendly multistoreyed houses with a single entry couldnot be established together with the technique and equipment employed for transporting and lifting heavystone and wood panels. This huge structure could not certainly be built without supportive tools andimplements.

Most respondents (92 percent) maintained that these structures were constructed to provide safety fromthieves while protection from heavy snowfall was also cited as a reason. Whatever be the considerationsbehind constructing these elaborate structures, these were certainly not designed to cater to the comfort ofthe inhabitants. This is the prime reason for a large number of these multistoreyed structures being put todisuse presently. These abandoned houses are deteriorating fast due to the lack of maintenance (Plate 3)and require interventions for preserving the rich heritage of the region.

Field observations

Ornate multistoreyed houses with abundant use of wooden beams are characteristic of Rajgarhi area.Similarity in the architectural principles and structural details suggest their possible evolution under onesingle architectural school that is designated Koti Banal Architecture after the most magnificent of thesestructures at that village. Locally available building material long thick wooden logs, stones and slates are

judiciously used for the construction of these structures. The height of these structures varies between 7 and12 meters above the platform and these are mostly four (Caukhat) and five (Panchapura) storeyed.

Raised platform

The multistoreyed traditional structures are observed to be constructed on raised and elaborate stone filledsolid platform (Plate 2) that is the continuation of the filled in foundation trench above the ground. Wherepossible platform is raised directly over in siturocks. The height of the platform varies between 6 and 12ftabove the ground. Dry stone masonry is used for the construction of the platform.

Massive solid platform at the base of the structure helps in keeping the centre of gravity and centre of massin close proximity and near to the ground. This minimizes the overturning effect of the particularly tallstructure during seismic loading.

Simplicity

The structures are observed to be constructed on a simple rectangular plan (Plates 1 and 2) with the lengthand width varying between 4 and 8 meters. The ratio of the two sides of the structures varies between 1.1and 1.4 which is in keeping with the provisions of the building codes (IS:4326, 1993) that suggest that thebuilding should have a simple rectangular plan and should be symmetrical both with respect to mass andrigidity so as to minimize torsion and stress concentration.

The height of the structures above the platform is restricted to double the length of the shorter side (length orwidth). All the houses have a single small entry and relatively small openings. Strong wooden empanelmentis provided around all the openings to compensate for the loss of strength. The internal architecture is splitinto staircase section and living section.

Walls

The walls of the traditional multistoreyed structure are raised by placing double wooden logs horizontally onthe edge of the two parallel sides of the platform. The thickness of the walls is determined by the width of thelogs (70cm). The other two walls are raised with well-dressed flat stones to the surface level of the logsplaced on the other two sides. The walls are further raised to 30cm by placing heavy, flat, dressed stonesupon the wooden logs on the two sides and by placing another pair of wooden logs upon the stones on theother two opposite sides.

The four walls of the structure are thus raised using the wooden logs and dressed up flat stones alternately.The structure is further reinforced with the help of wooden beams fixed alternately that run from the middle of

the walls of one side to the other, intersecting at the center. This arrangement divides the structure into fourparts and provides for joists supporting the floorboards in each floor of the building.

On the fourth and the fifth floors a balcony is constructed with a wooden railing running around on all the four
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sides. Specially designed wooden ladders provided access to the different floors with the roof being laid with

slates.

Framed construction

Interaction with the masses brought forth some interesting points regarding the architectural intricacy of thestructure that included its being constructed on the principles akin to that of a framed structure. It is told thatthe wooden frame of the entire structure was finalized and this was then followed by filling up of theintervening voids by stone. This has resulted in a mixed structure with two types of load sharing

mechanisms:

1. vertical load being taken care of by 1.5ft thick walls running in all four directions and2. horizontal load being taken care of by interconnected wooden joists running in both directions.

On the two sides of the structure wooden beams are observed to be provided from outside (Plate 2). It is heldthat these beams inserted from above are part of a special provision to enhance structure's seismicperformance.

Summary

Salient points of the technology used in the construction of the multistoreyed traditional structures is also

observed to be commonly used in other structures of the region as well. These include:

the use of thick wooden logs running through the entire length of each of the walls alternately withheavy stones andat the corners the edges of the pair of logs on the adjacent walls are joined together by hammeringthick wooden nails through them.

This has the effect of turning the structure into a single piece construction and iii) all the windows, doorways,ventilators and floor-joists are joined to these well-secured pairs of logs and these further strengthened thestructure.

Structural safety aspects

The architecture of the structures being investigated is woven around judicious use of wood. As a structuralmaterial, wood offers distinct advantage in earthquake performance over other materials wood is strong yetlightweight, hence ground accelerations are unable to generate as much energy in wood buildings as in otherbuildings. As an added advantage, wood-frame systems flex more than other materials, thus absorbing anddissipating energy.

Koti Banal architecture: salient structural features

Inertial forces are a function of the weight of the object and therefore heavier buildings are subject to higherearthquake forces. Likewise, higher ground accelerations create more stress in the structure. The forcesacting upon a structure during an earthquake are thus a function of the weight of the structures as also themagnitude of ground acceleration. Earthquake thus affects buildings differently depending on ground motion

and building characteristics. The nature of seismic ground motion at a building site is dependent on a numberof factors that include:

distance of building from the earthquake epicentermagnitude of the earthquakedepth of the earthquake focus andsoil conditions at the building site.

Nature of building response to an earthquake depends on the size of the building and its stiffnesscharacteristics. Earthquakes that have high peak ground accelerations pose the greatest challenge to woodsupported buildings. The inertial forces generated by the ground movement of the earthquake, concentratelateral forces in the roof and floors where most mass of the building is concentrated. The forces in the roof

and floors must be resisted by walls and entire structure must be adequately connected to the foundation.Critical components of seismic safety of wooden supported buildings include:

anchorage to the foundation
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strength and ductility of the wallsstrength and continuity of the horizontal elements (like roof, floor and ceilings) andinterconnection of the all farming elements.

The traditional buildings based upon Koti Banal architecture incorporate many features that improve itsseismic performance. Structural capabilities of these buildings include:

The mass and rigidity are distributed equally and symmetrically the point of resultant earthquakeforces (during an earthquake) thus tends to coincide with the point of resultant resisting forces.Torsion of the buildings is thus avoided or significantly reduced, which helps in shock resistance.The timber beams are housed in the walls in both the directions of the structure after 20 to 30centimeter of squared rubble dry stone masonry brought to courses. The linked timber beams form agroup of space stress system. The rigidity of the beams is nearly equal on cross ways so that itsentire rigidity tends to be identity and its ability to resist deformation is coordinated.The beams used in the building are mostly rectangular in shape. The ratio of width to height of thesebeams is 2:3 which is a suitable section for a bending member. Sections of these wooden beams arelarger than needed for adequate safety. The building system thus meets the required space rigidity asalso strength requirements. This further helps in shock resistance.Wood is a elasto-plastic material with ability to absorb power of earthquake. Both housing and nailingtechniques are resorted to for joining the wooden components incorporated in these structures (Plate4). This allows for minimal angular displacement. This kind of joint in the wooden beams incorporatesadvantages of both pin joint and the rigid joint and acts as a semi- rigid joint which is an additional

advantage for shock resistance.Wood strength is high in the direction of the grain but weak across the grain. If designed and usedproperly, wood has very few structural limitations. Wood assemblies offer a high strength-to-weightratio over those built with steel and concrete. This results in low inertial forces during an earthquake.The Koti- Banal architecture utilizes a number of wooden assemblies that help in resisting earthquakeforces that are a function of the inertial force acting upon the structure.Wood-frame construction, structural walls and floors sheathed with structural wood panels employed inKoti Banal buildings are well recognized for providing superior performance against strong forcesresulting from both wind storms and earthquakes. These walls and floors maintain high stiffness andstrength in the design range, and if pushed to their ultimate capacity, tend to yield only gradually whilecontinuing to carry high loads. These assemblies have high ductility which can absorb a great deal ofenergy before failure.

Floors and roofs of wood construction are flexible diaphragms. FEMA 310 (1998)treats wooddiaphragms as flexible but demands rigidity of the vertical elements. The vertical elevation of thesebuildings consists of rigid stone masonry wall that is adequate for providing the required strongsupport in the both directions of the building.The raised pedestal on the foundation together with the wooden beams at plinth level restrictearthquake vibration effects on the superstructure. It is accepted that stiffer soils promotes effectiveisolation. The elevated, solid stone platforms help in consolidation of the soil at the foundation leveland thus help in promoting isolation.

Equivalent static lateral force analysis of the Koti Banal structure

Most lateral forces acting on a structure during an earthquake emanate from inertia (mass) of the structures.

These seismogenic forces are sudden, dynamic and can well be of immense intensity. The magnitude oflateral forces primarily depends upon the seismic zone, nature of soil or ground condition and fundamentalbuilding characteristics. The design base shear is first computed for the entire structure which issubsequently distributed along the height of the buildings based on simple formulas appropriate for buildings

with regular distribution of mass and stiffness. The design lateral force obtained at each floor level is thendistributed to individual lateral load resisting element depending upon floor diaphragm action. Methodologyput forth by IS:1893 (Part 1) (2002) has been utilized for this work.

Design seismic base shear calculation

Table I shows the detailed calculations for the Koti Banal structure.

Distribution of lateral forces

Figure 2 shows the distribution of lateral forces in box type shear wall buildings. In order to successfullytransfer the seismic forces to the ground building should necessarily have a continuous load path. The
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general load path for the Koti Banal structure is as follows earthquake forces originating in all the elementsof the building are delivered through the transverse walls of the building and it is bent between the floors. Thelateral loads are transmitted from these transverse walls to the side shear walls by horizontal floor and roofdiaphragm. The diaphragms distribute these forces to vertical resisting components such as shear walls andvertical resisting elements if any, which transfer the forces into the foundation. The diaphragm must haveadequate stiffness and strength to transmit these forces. It is observed that in Koti Banal buildings the floorsare made of 20-22mm thick wooden planks that are expected to exhibit high degree of flexibility and all the

walls are 45cm dry dressed stone that are highly rigid. The above thus satisfactorily fulfill the flexiblediaphragm conditions.

Seismic performance of Koti Banal structure

Using the equivalent static method the design base shear for the Koti Banal structure has been computed tobe of the order of 700KN that works out to be 23 percent of total seismic weight of the building. Detailedinvestigation of a number of buildings in the area clearly reveal that the age old structural systems are stillintact and even the nonstructural components have not been damaged by the seismic activities despitethese being located in the most severe zone of earthquake damage risk (Zone V) and having experiencedmany earthquakes in the past. The age of the buildings clearly suggests that these would have experiencedat least DBE ground shaking in their life span (IS:1893 (Part 1) (2002)defines DBE as the earthquake whichcan reasonably be expected to occur at least once during the design life of the structure).

Age of the structures

Time of construction of the traditional buildings is important for assessing the archeological relevance ofthese structures as also for correlating the architectural style with other contemporary styles. Radiocarbondating of the wood samples collected from the panels used in the buildings was resorted to at Birbal SahniInstitute of Palaeobotny, Lucknow. The Koti Banal structure (Plate 2) was dated to be 880 90 years beforepresent while the one at Guna (that shows introduction of aberrations into the original style) was dated to be728 60 years before present.

The detailing of the structures suggests that the ones designing the structures had fairly good idea of theforces likely to act upon the structure during an earthquake event. The radiocarbon dates bring forth animportant fact that the principles of earthquake safety had evolved in the region as early as 1,000 years ago.Seismic performance of these structures has been tested by Kumaun Earthquake of 1720 and GarhwalEarthquake of 1803 that are considered to be highly damaging and this earthquake safety conscious schoolof architecture might well have started after the earthquake of 1100AD that is believed to have devastatedlarge tracts across India.

Evolution of any tradition is a long process that includes testing of certain features and evolving the same onlines observed to be working. At the same time certain time tested features are replaced to suiteconvenience and emerging needs without seriously dwelling upon their impact. It was interesting to note thatthe multistoreyed structure at Guna though built using similar architectural style is more occupant friendly

with the roofs being sufficiently high. This structure however digresses from seismic safety norms and doesnot provide for shear walls. Koti Banal architecture did not cater for the comfort of the inhabitants and wastotally utilitarian. This might be the reason for the introduction of aberrations in the original style as early as728 60 years before present as is evident from the dating of Guna structure.

Conclusion

The study suggests that the people inhabiting the area had developed an elaborate system for constructingmultistoreyed structures in the seismically vulnerable region. Appropriate site was first selected for theproposed construction for which the services of the traditionally recognized persons were resorted to. Itseems that some persons could assess and comment upon the bearing capacity of soil by examining soiltexture, moisture content and the other related features based upon their experience and accumulatedknowledge. Elements of this age old traditional practice need to be studied, documented, innovated andpropagated (with necessary improvements where necessary) so as to evolve a readily available, easy andcost effective tool for assessing site suitability.

There existed tradition of erecting structures over an elaborate, solid and raised stone platform that reducedoverturning effect in these particularly high structures. The construction style is quite distinct and a largenumber of structures in the region are built on similar fashion that is indicative of evolution of this particularschool of architecture in the region. This is termed Koti Banal architecture after the most magnificent
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representative of this school.

The Koti Banal architecture attained its zenith around 88090 years ago as is evident from the dating of theKoti Banal masterpiece. The main constituents of Koti Banal architectural style include:

simple layout of the structureconstruction on elaborate, solid and raised platform

judicious use of locally available building materialincorporation of wooden beams all through the height of the building at regular intervalssmall openings andsheer walls.

Seismic performance of these structures has been verified by Kumaun Earthquake of 1720 and GarhwalEarthquake of 1803 and this earthquake safety conscious school of architecture might well have started afterthe earthquake of 1100AD that is believed to have devastated large tracts across India. The Koti Banalarchitecture however did not cater for the comfort of the inhabitants and was totally utilitarian. This wasperhaps the reason for the introduction of aberrations in the original style as early as 728 60 years beforepresent as is evident from the dating of Gona structure. The Koti Banal architecture needs to be studied anddocumented in much more detail. Intricacies of this age old construction style have the potential of unfoldinga new line of construction that might be better suited even in present ground realities of the region.

It is observed that many old structures of Koti Banal style are being put to disuse and are deteriorating fast

due to the lack of maintenance. People are even demolishing these old structures voluntarily so as to usethe disassembled building material for the construction of new and modern dwellings. Masses therefore needto be made aware and educated on the issue of protecting these heritage structures. This would also provideresearchers with an opportunity of studying this majestic architectural style of Uttarakhand in detail.

It is observed that the traditional masons that had mastered the art of stone wood construction are fastswitching over to cement based construction due to the lack of patronage. Since they are not propagatingintricacies of the traditional construction practices, basic elements of the traditional construction style wouldsoon be lost. It is therefore necessary to study and document the finer elements of traditional constructionpractice. Innovating on the traditional building material and practices would give a lease of life to thisconstruction style.

Figure 1 Location map of the study area


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Plate 1Photograph showing simple but majestic architecture of the traditional houses in Dharali village


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Plate 2Photograph of the five storeyed masterpiece of Koti Banal architecture constructed 88090 years ago


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Plate 3Non maintenance of the structures is observed to take toll of the cultural heritage of the region

Plate 4 Photograph showing housed and nailed joints used for fixing the wooden components in Koti Banalarchitecture


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Figure 2Figure depicting side elevation and distribution of lateral forces in different stories of the Koti Banalstructure shown in Plate 2


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Table I Detailed calculations for the Koti Banal structure

References

Bilham, R., Gaur, V.K., Molnar, P. (2001), "Himalayan seismic hazard", Science, Vol. 293 pp.1442-4.

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Feldl, N., Bilham, R. (2006), "Great Himalayan earthquakes and the Tibetan plateau", Nature, Vol. 444 No.9,pp.165-70.


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