The traditional building systems in their buildings also, are indicative of the wisdom developed over centuries totally In resonance with the natural ecosystem and environment, climatically and geologically. These systems have successfully withstood natural disasters. And it is an irony, that now these systems have been totally discarded and conventional building materials and technologies are being adopted uniformly, irrespective of their suitability to the local conditions. Mud pushed t’e-hnw’ tnWcns .—~ Ba4Ptns ~sO,’en tetween ks4~~, ‘cAved ~n Fig. 1: Wattle and daub wall Appropiate/Intermediate/Sustainable Tecnologics a • Pcvjt ‘is’ TflDITIO’(4t. &‘Ihifti U 4rIvoaet LI \Iat. Sa’ne. Bamt’,~’ Lnt~. B~’niass C&n~att ~ai _______________________ l~q Dnn TECH~0LOGICA1 \lttrn Convendc’n.~±l Cerncnt SteeL. Brick~ Glass. Alaminurn. Pla,.tic. cc,. - 1 L’TLSV’fl based \tII~R*nj, — Rs.SWJ-IOfNc’sqm Ks. 21M$’.MMkwsqm *t- tt- ~n) ‘n Increasing Cost of Construction Cic Urttan, t- ks. W(W)’.qnc Traditional Technologies for Disaster Mitigation Introduction ndia is a vast country with variable climatic and geological I conditions across the regions with a history that dates back to one of the earliest civilisations. Its cultures and traditions are completely linked up with the climatic conditions of the region and the soil. Over the years the people of the region have developed living styles and food habits which are in conformity to what is available locally. The housing cluster in coastal areas of orissa and Andhra Pradesh, the circular plan for houses and sloping roofs clearly discern the strength in the construction system to take care of the cyclonic aerodynamical behavior. Hence it is very important that these traditional systems be understood, learnt and improved so that they fulfil the present day requirements of safety and architecture without compromising on the basic intuitive wisdom of ecological balance. Some of the traditional systems of building and water management need to be studied thoroughly appreciated and adopted with little or no innovation. Examples in the following pages have been critically analysed with a viewpoint of seismic strength and a system that kept people safe from floods and drought. There have been isolated cases of revival of the systems in watershed management ie.g. Aravari in Rajasthan, SukhomaJrl in Haryana) and in the building systems, which have been improved upon and have withstood natural calamities, recurrentand frequent in these areas. There is a need to combine traditional knowledge to present day innovations and draw a balance that results into cost- effective systems. V Suresh Chairman and Managing Director HUDCO Rinki Saxena Trainee officer (Projects) HSMI (HLJDCO) Some examples of these systems are analysed here. ACCRAJEKRA WALLS Accra Walls are the simplest and cheapest forms of wall construction. In conditions of typhoon or earthquake risk the mixture of earth and framing can be very successful. The structure of the wall is provided by a framework of vertical posts set in the ground or on a stone or concret base. Branches, split stems, reeds or bamboo (depend.inç on what is available) are woven horizontally between the posts to form a lattice. The inf ill and plastering material is applied to the framework on both the inside and outside, at a sufficiently damp consistency to be squeezed between the lattice. Irefer figure ii The walls are usually thin, 100—150mm. Soils with a higher clay content can be used because the framework largely reduces the effect of shrinkage in the soil. Mud is applied In layers and the cracks that develop can be subsequently filled in. Alternatively, mud can also be mixed with twists or rolls of straw, applied onto or pushed between a less dense lattice. The inner wall can be finished with plaster, which car. be mud-based and can contain a high straw or fibre content In case of damp countries, mud can be replaced with mud/sand/lime plaster, which produces more resistant results. Buildings using this system have lightweight roofs, such as thatch, tiles or corrugated sheeting. The thinness of the wall means that they do not have the same thermal mass normally associated with earth wall construction. However, the use of straw orother fibre additives increases insulation values. Also bamboo 5tfl~ttures uehasie well in storms and eartrclijake& however, constraints are that they have iow natural durab lIlt1’ and neec to be preserved lire Is a great risk and sbndardizaUon is not possible due to variation In sl2et I~ramewCwk with adequate anchorage and tie- ups provkffis resistance to earthquaKes ana typhoons it the w()cid is of sound quality. The tinlber skeletal structuczl system witn me accra wail as cladding dearly brings out me flexIble and not the rigid type nature of tne building unit. The M911t cladding of the accra wall aflo adds to the substantial reduction in mass wflld’l is what the modern earthquake engineering code reccimnnenc& Bamboo a~ a Construction Material Stiffness is of great importance In case of mof! floor structures, wtucfl have toraice nigh coe~ without themselves being heaw, so as to keep the Walis an Advantages of This system fli.~cn tflings e. S~JtL Vt: I It is a thean method Wtfle framework Is simple 2- Moderate s~[Ii are required and Work can be done sirtQbe• hanciecJhi 3. cmiii amounts Of earth are needed as compared to other eafThs~t&ns 4 Framework can be made o~kt of 5nhiM D~ces WIlICIl can certainly be available from trie idlcirirtv However some areas require Spec al attention- 1, The tranlework must he protected from deterioration from fungi and termites Separation ot the frame from direct contact with the ground is an Important precautlorL 2- it is important to introduce (igw?ity in the framework WI Lii bracing (or wlth5tarttflnig disasters Endia is said to possess the iargp~ Rarnboo resenjes in tne worici across the continent in (Its tropical 3fld the stth-tro~IcaL ~ It 15 found aLmost ewrywllerS LP1 tite Country except the extreme øry areas Of Rajastrian and the extreme coid areas Of Kashmir. Other factors in rts favour as a roof Ffl~ materIal ate, that of ow energy costs and Its comparable sdifness to weight ratio. Unlike the conventIonal materials isreei, cen~entetc~ It requires very little energy to form matetLa~ Of apc’roprlate cross- sectional profiles ano then faLrItatlon into cleQred structural form. Its ct~ffnesWwsJgnt ratio ~s 0 017 ]S compared to steel {0.O2~ and wood (0,013). aamboo construction requires little infrastructure and skills in Aamboo can be olcked up easily bY raw hanth in comparison to wood it is mucn faster growing than wood, Is agreeable to riarvestlnq practice and being a hollow cylinder In cross-Sectdofl. it needs ~eflr slmpi~ tools for extraCtion UnlikE 5~srlriQ &Id iOglalflQ rPt case or Wood Bamboo ~as been used as an important constituent rn roof ing $1rtce unrecorded history but its use has now become quite iimIte~ It can also be used for walls, floors, doors etc I-n cae of floor construction joists are laid on the beams and joined WIth lashings Crefer figure 21 Sccmetimes hardwood pins are used A Wilt bamboo may also be put tnrough the Joists and iasflec? to tne beani A Iloor cover islaicJ on top 0? the jOrsts made out of flattened bamboo, woven bamboo, spur bamboo orsmaii bamboos. grefer figure 31 Joists LW, b~ii A. wPtii En,ings U with pun C. with spilt aaiflboo b. JoHtSa woonn pin ag z e VIoer Covering ~. Joists. 4~rnri~ oeiiter-oncentecb Fl~tteri4d bJmbiho e Wcv~n bamboo ii. SpIrE aambacs e. Tlniber ~rh. to ~acilltale F small bamb~c’L joists at greate iiafflng di~Lar~cp Fig S In roofmg. thatch covered ligh welghtroofsgo excellently with Darnfloo, where the natural length of this structural vwe worn best. It provides a resilient and frrm base to which tht straw or isaf bundle; can oe securely tied by lOCaifr made ropei in roofs like slate and terracotta tiles, bamboo is mostly used in conJurctlon with timber, playing a contemporary roit It works werl fl a deco ratfve/ protecthde mat widenfa’r and battens for la’1lng/flxingtles. One kind Of Jo] ri ring system 1,35 been explained in figure 4 (the lashes and verticals are omittedL it k based on two horns’ a - at the end of tue diagonal, b which enter two holed. d - in the upper member. c - the Joint Is Fasitect with rope- l-lonn like these are a very traaitional method of Joining bamboos, out they cia not appear to have been tested for strength until now but has been Invariably useci since time inirnernorlal. A disadvantage ot thlsjoint Is mat är .e&. iOu- a. horns b. diagonal Fig 4 c upper member d. holes L~—~II1 r1tm’ ~.M3’ t’UiL-PiW~ -f*CtiOjj. £ ~satotauLuro r~ff~ r11A%#~ k. a ‘*‘- t~ ~a it -rrnc~a- t~fli-~c the diagonal has to fit exactly at both ends on the upper and lower members of the truss. This requires craftsmanship and time, and disallows prefabrication The upper and lower members should have nodes as close as possible to the joint The vertical simply fits in between and is lashed. Horns are not necessary because the forces in a vertical are smaller than in a diagonal House at Himachal Hills in the traditional two-storey mud houses at Kangra valley IRefer figure 5) the foundations consist of cutfrandom stone with mud or mud/lime mortar, 60cm wide x 50cm deep below ground level and 25-40 cm height above ground forming piinth infilled with rubble and packed earth. Wails are approx. 40cm wide, made of mud brick in mud mortar and plastered with mud and dung mixture They are typically 4.5 m high with 6-8cm thick wood lintels and a continuous 10cm wood ring beam Floor joists and ground floor rafters are embedded in the walls for support. The roof is hipped, with shed roofs on additions and verandahs. It is typically framed with wood rafters at 1 metre on center or bamboo rafters at 30 cms on center; intermediate rafter ties are used at 2-3 m on center The roofing material is either slate shingle or thatch. Wood framing is usually used with slate shingles. The roof pitch is approximately 8.12 to 12 12. From tne seismic point of view tnese houses nave oeen well designed as far as balance of structure, door and window locations and their sizes are concerned They are adequately sited with appropriate distance between two buildings. However, foundation de- sign, shape of the plan, roof design, foundation to wall connection and quality Of workmanship there is scope for improvement Also rigidity of the walls, the proje- ctions and over-hangs, wall to wail connections and wall to roof connections must certainiy be replaced ________________ through more flexible lointing and removal of overhangs in roofs in seismic zones. The addition of the ring beam, the high strength of the mortar and the building material and the reduction in the wails can increase earthquake resistance. certain improvements that can be incorporated at a very low cost can be, to use cement mortar in tne foundations, using light- weight roofing and independent framing at verandah, using conti- nuous ring beam anchored - to wails with corner ~,g S bracing, reinforcing wall- to-wall connections with angle braces and ensuring that the floor joists penetrate the walls. These will add ‘1 per cent to 18 per cent to the total construction cost and shall require I to 4 mandays extra. In fact using light weight roofing can cut down on construction cost. Average total cost Of such a house is estimated around Rs. 25,000 to 30,000. House at Upper Ganges Valley, Uttar Pradesh in the traditional two storey stone houses in UP hills (refer figure Si, the foundation is 60 cms wide x 50 cms deep, consisting of cut stone ii mud mortar and forming a 45 cms wide x 25 cms high piinth infilled with rubble and packed earth The walls are 45 cms wide x 420 cms high of slate with minimum clay mortar and a mud and dung plaster inside and outside. The second-level floor joists penetrate the wails. Either slate, cut stone or 3 cms thick wood lintels are used over openings in UP, longitudinal timber beams spanning 300 cms at 50— 60 cnis on center support wood slat sheathing From the seismic point of view these houses have been adjudged strong In structural balance, door and window locations and sizes and the strength of the building material The siting of the houses, their foundation design and theirshape of the pian and quality of workmanship can be, however, im- proved upon. The separa- tion between the buildings neeas to tie increased, trie center of gravity brought down, rigidity of walls to be checked and roof design and projections and overhangs to be re- designed. The connections ___________ between the foundations, the walls and the roof need to be strengthened. Absence of a ring beam and low strength of mortar can also cause heavy damage during seismic shaking- Recommendations for improvements include constructing houses with crush joints between buildings and reducing or eliminating projections at no extra cost, use of cement mortar in foundations can reduce costs and construction time. Also use of stepped foundations, installing a ring beam at the top of the wall, using cement mortar in wails, x braces in truss construction, lightweight roof mats, extending floor joists through the walls, using timber plates over the gable walls and steel pins in the corners would go a long way in improving seismic stability instiMUon of the rout Sue The mouL’ied F,hapealsre en-*~ with a tO cm ocertffp Locking s~eton to prevent Siding and for a it; ,iharia on Pie khapra ovdriafplng 0518 another t’uu~9lN6’ oe2~tCM Fig. 6 flF’ICAL WAL-L- et~~TlOH These changes would add Ito 30 per cent of construction cost and ‘ito 6 extra mandays depending on which options are incorporated. Average total cost of such a house has been estimated to be Rs 20,000. Country Roofing Tiles The use of half round country roofing tiles with some variation goes back many centuries in several parts of India. Handmade burnt country tiles are commonly used in the rural areas of Gujarat and Maharashtra. However some government and non-government organizations have rejected country roofing tiles as breakable and destructive to the timber substructure or supports. But in many villages in Gujarat every household makes its own tiles for annual replacement as well as for building new houses or for making additions to old ones. They know which mud to select without the aid of a laboratory. The tiles are made in uniform size, colour and strength and are waterproof. The tiles made to cover the ridge are larger in size. The flatter, moulded knaprel are also used in some areas as roofing tiles. (Refer figure 7 They are installed with a 10 cms overlap and are made with a locking system to prevent sliding and for a close fit. Handmade khapre! are tapered but may fit into each other haphazardly as they are all uneven widths. These tiles are 100 per cent labour intensive and no machine or factory product need be involved. Fuel (grass, rice husk, cow dung etc.) used for baking is no threat to forests. For the substructure, no well-cut wooden battens are needed to support the country tiles. The uneven level can be corrected by inserting a tile over the batten at a right angie to the direction of the tile. Two mandays are required to cover 100 sq-ft. of roof area. These roofing tiles also do not have a high maintenance cost, in case of Micro concrete Roofing tiles with two nibs, for use in high wind coastal areas, have proven to be cyclone resistant. Inundation Canals The inundation canal system was the ancient systemofflood loverflowi irrigation in Bengal and some parts of Orissa. it was best suited to the region and the needs of the people. Bengal with its heavy monsoon between dune and October was marked for rice cultivation. The monsoons never failed in Bengal but they could end early and then the crops would become short of water during October, However, traditionally the farmers used the rainwater alongwith t~e flood- water in the early months of the monsoon when the river water was rich and full of mud, Fig.? and later the crops would be fortified enough to resist the hard conditions of a rainless October that followed. For this, during the rains, the floodwater was allowed to flow into the paddy fields through inundation/overflow canals carrying waters rich in silt and fish. (Refer figureS) The high mineral content of the water would manure the fields and the fish would eat on the larvae of mosquitoes that would be breeding in the stagnant waters. The embankments along the rivers were built in earth that enabled making brea- ches (also called kanwas in some areas) as and when required. The engineers would make the breaches. The water was then handed over to the local boards. These boards, working through the peasantry, ensured that the water reached every field. These breaches would then be closed up after the floods. Some features of the canals were: I. The canals were made broad and shallow, carrying the crest of the waters of the river floods, rich In clay and free from coarse sand. (refer figure Si THE FLOOD IRRIGATION SYSTEM OF BENGAL EmbsrEneQ Embanked riverRiver wM’ breathS embankment ft~ — CarS Cul StarrSnkn&nt jcr .rtb~:: a ‘Efi —~ 1 Source - Cg -or~~ I4~sdom FStiq~ and twa Sill — CnUkwppSf L~ R~WI~ Ji~I ?ç~ ~ ••P••• ..J~ COpSflI$fld : ~ ~ 2. Thecanaiswere lonQ and cOnt{tiiiOusandapathy OP the inGIan government fairLy paraller to eacn other ~OflQWlth iinttfficlent public arId at a right distanc~€ irom tflibabve In irrigabon led each other for the pi~rposes to the breakdown of thIs tradIUonaI of Irr~gat~ori system. This culminated in the complete C~generitlon of 3~ Canals flad to be c’eared per1odlC~Irythe agncumturaP economy of anG tI’R embankments srrerlQthened,the area leaching to the famous However, th~ çIearir~ of the fam~ne or BengaL WeqeneralAon canals ware flegI&teG DV the of the systems with Innovation communities over a rseriod and improvement could bring of time. AsttiesiKed canal5 tarriedtF~e situation back to normal lesser amount oP water, this re~v red in flood mc of tne main river causing damane clown the track. And then the authonties began to think that the banks Referencea were Just finac Coritror rnietp-tousI fltiiiding wtth Earth A H]ndbcsk ann neecea to be hIgher and s!roriger..by John Norton Second EiJIPOn. Ad*eci to Uiis came the aoathy t,~ndan irrtermedi.ite TaflaoFci~ Df the government, lnsuf-nciefit Pubiicaton~, public inltlatkve in Wrlg]tlon t997 and unwise railway constructIon that flnahly ted to the 2. ovin; W~sdErni~ A Ceiflre breakdown of th is system and fat Science and EJWIrOPW9eM PLItIIIZaOOn culminated in tie complete deQeneration of me agrlcWturai ecorlomyoFthis 3 vemacuiar HrMJSmO ii’ seismic sectIOn Zotles Of lnoii. A Jtint lnac’-u5 Prowam to lrraove tow-Sfrefl~Ch Masonry HC,uSlfln. Deeemoer 19B4. Gradually the governa rice during me Briush Rule replacedthese eartflen bunds bypucca bunGsari~cl dams. And later.