Bamboo Architecture

APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

CHAPTER- 1 INTRODUCTION

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

INTRUDUCTION In the present day scenario the building industry is using up non renewable natural resources to its maximum extend. This has resulted in large scale exploitation of nature and leads to unhealthy practices leading to destruction of nature. The emerging consequences are large scale deforestation, destruction of natural echo system, exploitation of river sand, destruction of paddy fields for clay for bricks etc. This has resulted in humans fighting against each other and emergence of mafia gangs like sand mafia, forest mafia etc. The building industry has a direct role in all these activities such as mafia gangs and ruthless exploitation of nature and is to be blamed for it. These activities are causing havoc to nature and mankind as such. An easy solution for preventing such haphazard exploitation of nature and threat to human kind is to look into nature for easily available renewable, cheap and replenish able material as substitute for the conventional building materials like brick, sand, cement etc. its here that the use of fast regenerating materials like bamboo comes into frame. Bamboo or bambusa is the fast growing plant in the nature. Its readily available, fast growing and is having good workability as well as strength. More over it opens up a lots of job opportunities for the rural sector.

Aim To put forward bamboo as an alternative building material in the present day construction industry there by reducing the haphazard destruction of nature.

Objective To study about bamboo, its structural properties and its availability and to find out a possible way to supplement it as an alternative building material in the present scenario of Kerala. Construction methods related to bamboo is also subjected to study.

Scope of study The replenishing ability and availability of bamboo is to be studied in detail. Bamboo is now being widely used across the world as an alternative building material. The different indigenous treatment of bamboo has increased the life span many a fold as a structural material. Study is to be made on how to implement this in the present day scenario here by reducing the exploitation of non renewable materials from nature.

Limitations As such bamboo in present day Architecture is for highly expensive ones only. Availability of bamboo has decreased to a greater extend there by resulting in bamboo being a more expensive material.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Methodology 1. To make a study on availability of bamboo. 2. The structural property of bamboo. 3. The various construction methods and techniques used in India and other parts of the world by literature study and to gain experience of building techniques implemented. 4. Consult with some of the leading exponents of bamboo in kerala. 5. To make a study on availability of bamboo. 6. The structural property of bamboo. 7. The various construction methods and techniques used in India and other parts of the world by literature study and to gain experience of building techniques implemented.

Research Design 

The properties and types of bamboo are studied in a structural context from primary sources, secondary sources, and lots of qualitative data sources that are authentic and valid such as logs, official records, reports, etc. Study the works of architects using bamboo as their major building material.

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Case studies should be done in buildings where bamboo is used for structural, decorative and protective purposes.

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Sort out and analyse the data collected from the literature study and the case study.

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Study the various techniques used in bamboo construction. Consider the possibilities of applying the construction techniques in the modern buildings and find out the problems generated.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

CHAPTER- 2 LITERATURE STUDY AND DATA COLLECTION

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

LITERATURE STUDY AND DATA COLLECTION The properties Strength properties In a cross-section of a bamboo culm it has to be distinguished between a dark outer zone (approximately 30 percent) with closely packed fibres and a white inner zone (about 70 percent),which is rather porous. With increasing culm height the share of percentage of the dense exterior fibers in relation to the crosssectional area increases and therefore slim canes are superior to thick-walled bamboo. The accumulation of the rigid fibers in the edge zone improves the edge zone improves the values of elasticity as well as tension, shear, and bending strengths. As of timber, the modulus of elasticity (MOE) of bamboo is reduced with increasing stress (5-10 percent). A MOE of 2.000 kN/cm2 can be assumed. Fig-1 Bamboo cross

The tensile strength of the outer zone is two to three times higher than that of the inner zone. The tensile strength in the nodes is only moderate because the fibers there run disorderly. Nodes reduce the tensile strength of the culm. The tensile strength decreases in culms of over 5-6 years of age. The compression strength, however, increases with the age. In a test the 6 year old culms Showed 2,5 times the compression strength than the one year old ones. Cane sections with nodes show approximately 8 percent higher compression strength values parallel to the fiber compared to sections without nodes. In tests with compression load perpendicular to the culm axis, the nodes cause strength values up to 45 percent higher than in tests with tube sections without nodes. Fig-2 Bamboo joinery section

The sea level, at which the plant grows, as well as the age of poles has a big influence on the silicification of the vessels, which leads to a considerable increase of compression strength. The shear strength of thin bamboo canes is higher than that of thick-walled tubes, caused by the ratio of the rigid fibres to the sectional area. The shear strength of node material is about 50 percent higher than that of internode material.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Fracture behavior The bamboo tubes behave well at compression load. Neither sudden buckling nor cracking of the tube wall occurs. Shear fractures are the most frequent failures in bending tests. These are favored by drying cracks parallel to the culm axis. The internodes in which high shear stresses occur should therefore be filled with concrete. In case of shear failure, there will always remain a load-carrying capacity of the two halves.

The fracture behavior of conventional timber differs from the fracture behavior of bamboo. Cracking of individual fibers does not lead to a spontaneous break of the whole cane. The appearing cracks are immediately redirected into the fiber direction and therefore affect less the stressed part. The input of energy is retarded. The reinforcement nodes (diaphragms) prevent the emerging longitudinal cracks from spreading over the entire tube length. The node material increases particularly the compression, shear, and ply bond strength. Such symptoms are called factors of increase of the fracture toughness.

Fire resistance The fire resistance is very good because of high content of silicate acid. Filled up with water, it can stand a temperature of 400 deg C.

Elasticity The enormous elasticity of bamboo makes it to a very good building material for earth- quake- endangered areas.

Differences between bamboo and wood In bamboo there are no rays and no knots (a ray is the radiating part of the tissue in a tree; a knot is a hard part in timber caused by the shooting out of a branch). This makes bamboo a far more evenly stressed throughout its length. Bamboo is a hollow tube, sometimes with thin walls, and consequently it is more difficult to join bamboos than pieces of wood. Bamboo does not contain the same chemical extracts as wood, and can therefore be glued very well. However, the outer skin of culm cannot be glued because of its high silica content. The outer skin of a culm does not have any bark; it contains a lot of silica, which dulls the edges of tools.

Advantages  Because of its hollow form, bamboo is strong and stiff, and it can be cut and split with simple tools.  The surface of bamboo is hard and clean enabling easy use for specific purposes without much processing and consequently avoiding wastage.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

 Bamboo can be grown on a village scale, or even on a family scale and can be harvested at the time of need without any additional expenditure.  It possesses good mechanical properties and a high strength-to-weight ratio.  It can thus make lighter but stronger structural components for houses at comparatively low cost.  It can be dried with a simple method of air-drying and treated with preservatives to enhance service life.  The return of capital is quicker than for wood.  Bamboo structures behave very well in storm and earthquake.  Temporary and quick construction in disaster-prone areas is possible in cases of emergency.

Disadvantages  Low natural durability: bamboo needs preservation treatment, which in many cases is more difficult than for wood.  Bamboo can hardly withstand contact with the soil however it can last a long time, if there are no termites.  Fire is a very great risk.  A bamboo culm is not completely straight: it is tapered; the nodes occur at different distances; the prominence of the nodes can be a nuisance when the material is being worked.  The hollow form makes jointing difficult Standardization is virtually impossible, because of the variation in sizes.  Only in the joints can an attempt at standardization be successful.

Construction methods There is a long-standing tradition of bamboo construction, dating back many hundreds of years. Different cultures have found in this material an economical system of building, offering sound yet light and easily replaceable forms of shelter. The methods, activities and tools are often simple, straightforward and accessible to even the young and unskilled. Bamboo can be used to make all the components of small buildings, both structural and non- structural, with the exception of fireplaces and chimneys. It is, however, often used in connection with other materials, cost and availability permitting. A typical building comprises following elements.      

Foundations Floors Walls Roof Doors and windows Water pipes

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Foundations Bamboo in direct ground contact. Bamboo on rock or preformed concrete footings. Bamboo incorporated into concrete footings. Composite bamboo/concrete columns.

Bamboo in direct ground contact Bamboo, either on the surface or buried, can decay; within six months to two years. Preservative treatment is therefore recommended. For strength and stability, large diameter thick walled sections of bamboo with closely spaced nodes should be used. Where these are not available, smaller sections can be tied together. Fig-3 Preformed concrete footings

Bamboo on rock or preformed concrete footings Ideally, where bamboo is being used for bearings it should be placed out of ground contact on footings of either rock or preformed concrete. As above, the largest and stiffest sections of bamboo should be used.

Bamboo incorporated into concrete footings The third approach is to incorporate the bamboo into a concrete footing; this can take the form of single posts or Strip footings.

Fig-4 Single post footing

Composite bamboo/ concrete columns An innovative development involves the casting of a concrete extension to bamboo post using a plastic tube of the same diameter. The result is a bamboo post with an integral foundation.

Floors

Fig-5 Strip footing

The floor of a bamboo building may be at ground level, and therefore consist only of compacted earth, with or without a covering of bamboo matting. However, the preferred solution is to raise the floor above the ground creating a stilt type of construction, This improves comfort and hygiene and can Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

provide a covered storage area below the floor. A minimum ground to floor distance of 500 mm is recommended to allow for inspection. When the floor is elevated, it becomes an integral part of the structural framework of the building. The floor will comprise:

structural bamboo elements bamboo decking

Floor structure Floors normally consist of bamboo beams fixed to strip footings or to 'foundation posts. The beams, therefore, run around the perimeter of the building. Where the beams are fixed to posts, careful attention to jointing is required. Beams and columns are generally around 100 mm fat diameter. Bamboo joists then span in the shortest direction across the perimeter beams. The joists are often laid on the beams without fixing, but some form of mechanical connection is recommended. Depending on the form of- floor decking, secondary joints, often taking the form of split culms, may be required. Joist diameters are in the order of 70 mm. Joist centers are typically 300 to 400 mm, or up to 500 mm if secondary joists are used. 1. 2. 3. 4. 5. 6.

Fig-6 Joist arrangement- primary

Fig-7 Joist arrangement- primary and secondary

Small bamboo culms Split bamboo Flattened bamboo (bamboo boards) Bamboo mats Bamboo panels Bamboo pirouettes

1. Small bamboo culms: Small diameter culms are tied or nailed directly to the joists. 2. Split bamboo: Bamboo culms are split along their length into strips several cm wide, they can be fixed directly to the joists in the case of tying or nailing, or a turner batten can be fixed to the joist beforehand to facilitate nailing. Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

3. Flattened bamboo: These are formed by splitting green bamboo culms, removing the diaphragms then unrolling and flattening them. The resulting board is laid across the joists and fixed by nailing or tying. The surface finish of these three types of floor deck is, understandably, uneven and difficult to clean. They can be screened with cement Bamboo floor mortar for reasons of hygiene and comfort. 4. Bamboo mats: These are formed by weaving thin strips of bamboo. Strips vary in size from 20x2 mm to 2x1 mm, depending on the intricacy of the pattern. Mats should not be fixed y direct nailing, but are held in place by bamboo strips or timber battens tied or nailed over the top. This is one of the easiest types of traditional floor to keep clean.

5. Bamboo panels: Layers of woven mats or strips, laid at right angles, are bonded together into boards, which are then nailed to the joists. 6. Bamboo parquette: Thin slivers or mats of bamboo are formed into multi-layered tiles laid on treated bamboo or wooden strips fixed to compacted earth or a concrete sub floor.

Walls The most extensive use of bamboo in construction is for walls and partitions. The major elements of a bamboo wall generally constitute part of the structural framework. As such they are required to carry the self-weight of the building and also loadings imposed by the occupants, the weather and, occasionally, earthquakes. To this end, efficient and adequate jointing is of primary importance. An infill between framing members is required to complete the wall. The purpose of the infill is to protect against rain, wind and animals, to offer privacy and to provide in-plane facing to ensure the overall stability of the structure when subjected to horizontal forces. The infill should also be designed to allow for light and ventilation. Not least is its architectural and aesthetic function. This infill can take many forms: 1. 2. 3. 4. 5. 6.

Whole or halved vertical or horizontal bamboo culms, with or without bamboo mats Split or flattened bamboo, with mats and/or plaster Bajareque Wattle (wattle and daub, lath and plaster, quincha) Woven bamboo, with or without plaster Bamboo panels

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

1. Whole or halved bamboo culms: The preferred orientation is vertical as this increases the shear resistance of the wall and is also better for drying after rain. Vertical members can be driven directly into the ground or fixed back to beams by tying with or without facing battens. Halved culms can be fixed in the same way, cither as a single or double ply construction, or anchored between horizontal halved culms. Woven bamboo mats can be attached to one or both faces using tied or nailed bamboo battens. Fig-8 wall of whole bamboo culms 2. Split or flattened bamboo: Split or flattened bamboo can be fixed vertically to intermediate bamboo members tied to or mortised into the posts, or fixed horizontally directly to the posts. Boards can be stretched or covered by wire mesh to provide a suitable surface for the plastering. Closely woven matting can also be applied to the board surface with or without plaster. 3. Bajareque:

Fig-9 wall of vertical halved culms

In this, bamboo strips of 4 to 5 cm are fixed horizontally, spaced at 5 to 7 cm on both sides, and the space between the strips filled with mud and straw. Final finishing is with mud and plaster. 4. Wattle (wattle and daub, lath and plaster, quincha): Common in parts of India, Peru and Chile, this comprises coarsely woven panels of bamboo strips, plastered on both sides. Unlike plastered bamboo mat wall, the wall consists of bamboo lath as a base for stabilized Fig-10 Bajareque wall construction mud plaster with organic fibres, cow dung, etc. Plaster (stucco) is applied out-side and finished with lime wash to give a typical stucco appearance. Bamboo lath consists of bamboo strips and round bamboo fixed to a load-tearing wooden frame work. Normally, the wooden frame is exposed and the wattle acts as the infill. Various designs of lath are in use: "sprung strip" and woven construction appear to be roost popular type of lath. In India, whole culms or half culms are used as lattices known as jaffri, with rather larger interstices filled with mud and straw and finished with mud plaster. Wattle walls, unlike dry wall Fig-11 Quincha wall construction construction, provides protection against weather and insulates the Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

house against fire. They have performed well against earthquakes. 5. Woven bamboo: Coarsely woven panels similar to those fot wattle but with closer wefts can be used with or without plaster. The plaster can be made from any combination of mud, clay, and sand, stabilized with lime, cow dung, cement and organic fibers. The surface can be finished with a line wash to give a typical stucco appearance. Preservatives may be added, but due attention should be Fig-12 Woven bamboo wall paid to health, safety and environmental matters. 6. Bamboo Panels: Panels have been developed specifically for use in walls and partitions and have the advantage of, imparting greater structural rigidity to the construction. Bamboo has also been used as reinforcement for stabilized or rammed mud walls. However, difficulties exist in achieving an adequate bond between the mud and bamboo to ensure composite action. The following aspects require attention for improving traditional bamboo walling systems: Structural behavior and performance of different walling systems subjected to wind and earthquake forces. Standardization and improvement of jointing techniques. Standardization of preservative treatment techniques, keeping in view environment and user-friendliness. Developing grading rules for bamboo for their use as mat, board, lath, etc. in wall construction and developing standards on traditional walling systems.

Roofs The roof of a building is arguably its most important component - this is what defines a construction as a shelter. As such, it is required to offer protection against extremes of weather including rain, sun and wind, and to provide clear, usable space beneath its canopy-. Above all, it must be strong enough to resist the considerable forces generated by wind and roof coverings. In this respect bamboo is ideal as a roofing material - it is strong, resilient and lightweight. The bamboo structure of a roof can comprise "cut" components- purlins, rafters and laths or battens, or triangulated (trussed) assemblies. Bamboo in a variety of forms is also used in roof covering and for ceilings. Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Traditional roof construction: The simplest form of roof comprises a bamboo ridge, purlin and eaves beams, supported on the perimeter posts. Halved culms are then laid convex- side down, edge to edge, spanning from the ridge to the eaves. A second layer, convex side up, is then laid to cover the joints. The maximum overall span using this method is about 3 m. A variation on this is the use of whole culms, suitably spaced to accept battens for tiles or thatch. To extend the span, a central post can be used. Beyond this, the options are almost infinite. A selection across sections, efficient jointing of components is a key consideration.

Trusses Trusses offer advantages over traditional forms of construction, including more economic and efficient use of materials, the ability to span larger distances, the use of shorter components and the use of prefabrication.

a

number

Much research and development has been carried out in this area. This work has highlighted the relative weakness of the joints and also of the bamboo in compression perpendicular to its length. In addition, much of the deflection of a loaded truss has been found to be due to deformation at the joints.

of

Fig-13 Bamboo roof

As with the roofs, configurations are many and various. The King post and Fink are the simplest, readily spanning 4 m using traditional jointing. Culm diameters typically range from 40-100 mm. An 8m span has been achieved b improved jointing. The pitch of the truss should be at least 30 degrees in areas of high rainfall, Truss spacing are consistent with the use of bamboo purlins (2-3m).

Fig-14 King post truss

Fig-15 Janssen truss configuration

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Needless to say, for both cut and trussed types of roof, the applied loads must be considered and, for trusses in particular, the design justified by test. In plane stability is another primary consideration; this is usually provided by diagonal bracing members.

Roof covering Bamboo roof coverings can form an integral part of the structure, as in the case of Overlapping halved culms. More often, they are nonstructural in function. Examples include:

    

Bamboo tiles Bamboo shingles Bamboo mats Corrugated bamboo roofing sheets Plastered bamboo

Bamboo tiles: These can take the form of halved, internodal culm sections, fixed to battens and over-lapped in a similar manner to the full length halved culms. Roofs covered in this manner tie susceptible to leakage. Fig-16 Bamboo tiles

Bamboo shingles: Shingles, measuring 30-40 mm wide x internodal length (400-600 mm) are cut from green culms, 70 mm or more in diameter and then air dried. The shingles are, hooked onto bamboo battens (maximum spacing 150 mm) by means of a tongue cut into the underside. Three laps are required to make a roof watertight, requiring some 200 shingles per square m. Nailing may need to be considered if high winds are likely. Fig-17 Bamboo shringles

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Bamboo mats: A layer of bitumen is sandwiched between two mats forming a semi-rigid panel. The mats can be fixed to rafters' at 200-250 mm centers. A bituminous or rubberized weatherproof coating is then applied to the finished roof. Corrugated bamboo roofing sheets: PF resin is applied to a bamboo mats to form a five layer set which is then hot pressed between corrugated platens. UF resin bonded sheets overlaid with PF resin impregnated paper live also been produced. These products are strong and lightweight with good insulation. Plastered bamboo:

Fig-18 Bituminised bamboo sheets

A cement plaster with or without the addition of organic fibers, is traditionally applied to bamboo roofs in South America. Other typical roof coverings include: Reed thatch Corrugated iron sheeting Plain clay tiles Clay or concrete pan tiles The weights of roof coverings vary considerably (20 kg/m2 for bamboo tiles and shingles, 42 kg/m2 for reed thatch, 13 kg/m2 for corrugated iron and 71 kg/m2 for clay tiles).

Footbridges and Bridges Footbridges and bridges are also constructed with bamboo. Since bamboo is much more elastic than solid timber, its use requires particular constructional measures which limit vibration, bending and twisting. Footbridges and bridges are structures which are exposed to weathe, if indeed they are covered. For this reasons their life span is only one third of that of house structures. Bamboo as a building material for bridges has applications ranging from a few bamboo poles placed across a ditch to the twin suspended frame truss spanning a 30-50m wide river. The following examples present a review of the possibilities with a short description.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

Footbridge without surface Tied battens hold the poles together and act as a load distributor so that the load on a single pole is transferred to its neighbor. The ends of the poles are pinned L the ground. They are secured against turning and displacing.

Footbridge with surface

Fig-19 Bamboo footbridge

The layer of pole has differing spaces. The woven battens provide rigidity and distribute the load. Pile serve intermediate supports and also as posts for the handrail.

Footbridge with tied rail In this example a bundle of five bamboo poles forms the load-bearing beam. The lashing consists of strips of bamboo bark. The posts are tied diagonally between the beams and hold these in place. Vertical posts support the ends of the handrails. In the middle of the bridge the handrails are also braced by long canes anchored in the embankment to steady the V-shape against toppling.

Bamboo bridge with intermediate posts in the riverbed When using many piles, the spans are usually kept below 2m. The piles or posts form bundle to two or three posts of which only one continues above the bridge platform to carry the handrail. Longitudinally and transversally they are stiffened by diagonal braces. The bridge floor is covered with woven battens, which are held on the floor joists by bars located in the edges. Lateral sliding of this covering is Fig-20 Bamboo bridge prevented by the bridge posts.

Department of architecture, College of Engineering Thiruvananthapuram

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APPLICATION OF BAMBOO IN BUILDING INDUSTRY

2011

soil reinforcement Bamboo can be successfully for the reinforcement of weak soil, for example, to strengthen a road. The durability is a major concern: bamboo is a natural material, and biological decay is evident if such a material is covered with soil. Under the prelatic level bamboo can live a long time, but otherwise it will decay very quickly. Chemical preservation is not appropriate because the preservatives will be leached out by the water in the soil. Termite attack is another problem. It is said; however, that bamboo as reinforcement under a road is not likely to be attacked by termites, because of the lack of oxygen and the vibrations caused by the traffic. To reinforce a road, it is advisable to use a woven mat of split bamboos at intervals of 0.3 to 0.5 m in both directions. This mat is placed about 0.5 ni under road level. To reinforce a slope, first imagine how a failure will develop. The reinforcing bamboos have to prevent the sliding movement. They are laid in layers, with about 0.5 m between the bamboos.

Joining techniques Effective jointing is fundamental to the structural integrity of a framed construction. Furthermore, the suitability of a material for use in framing is largely dependent upon the ease with which joints can be formed. Because of its round, tubular form, jointing of two or more bamboo members requires a different approach. Despite its relatively high strength, bamboo is susceptible to crushing, particularly of open ends. It is also characterized by a tendency to split; the use of nails, pegs, notches or mortises can therefore result in considerable reductions in strength. Connections must also cope with variations in diameter, wall thickness and straightness.

Traditional joints Traditional jointing methods rely principally on lashing or tying, with or without pegs or dowels. The basic joint types are:    

Spliced joints Orthogonal joints Angled joints Through joints

Department of architecture, College of Engineering Thiruvananthapuram

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Spliced joints: Two or more culms are joined in line to form longer members. Splicing is usually carried out in one of four ways Full- lapping: Full section culms are overlapped by at least one internode and tied together in two or r greater strength, bamboo or hardwood dowels can be used. One disadvantage of this is quite bulky. Half- lapping: Culms to be joined should be of similar diameter and cut longitudinally to half depth over at least one internode length. The components are fixed as for the full lap joint. Butt joint with side plates: Culms of similar diameter are laid end to end. Side plates made from quarter round culms of slightly larger diameter and two or more internodes long, are fixed over the join by tying and usually, dowelling.

Fig-21 various splice joints

Sleeves and inserts: Shorts lengths of bamboo of appropriate diameter are used either externally or internally to join two culms together.

Fig-22 full lapped splice joint

Fig-23 half lapped splice joint

Department of architecture, College of Engineering Thiruvananthapuram

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Orthogonal joints These are the commonest types of joint, where two or more members Meet or cross at right angles. The basic configurations are:

Butt joint Crossover joint Butt joint: The simplest form of butt joint comprises a horizontal member supported directly on top of a vertical member. The top of the post can be cut to form a saddle to ensure secure, seating of, the beam and good load transfer. The saddle should be close to a node to reduce the risk of splitting. A variation on the saddle involves the cutting of a long, integral tongue which is bent right over the transverse member and tied back. Other details include square notched ends, side plates and tendons. The saddle detail can also be applied to horizontal framing. Variations include the double joint and the double bent joint. For the single butt joint, improved stiffness can be achieved by the use of a hardwood tendon and key. The ends of the horizontal members can be cut to form horns or integral tendons to be located in corresponding mortises in the post. Fig-24 butt joint with side plates

Crossover joint: These are formed when two or more members cross at right angles. In the horizontal plane, the function of the joint is mainly to locate the members and to provide a degree of lateral stability. Where the crossover is in the vertical plane, the joint could be load bearing, as in the connection of floor beams to posts. Simple tying is an option, although Improved stability can be achieved by supporting the beam either on the stump of a branch at a lode or on a short length of culm tied independently to the post. The tendency to slip can be reduced by insetting the supporting piece into the post, or by dowelling. Most crossover joints are also suitable for connecting inclined members, for example purlin to rafter connections.

Department of architecture, College of Engineering Thiruvananthapuram

Fig-25 Crossover joint

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Fixing methods: Most types of joint rely mainly on tying or lashing, with or without the use of pegs or dowels. Ties can be made from split bamboo, coir rope, palm fiber rope, iron wire or tape. In the case of butt joints, the ties can be passed through a predrilled hole or round hardwood or bamboo pegs or dowels inserted into preformed holes. Pegs are driven from one side, usually at an angle to increase strength. Dowels pass right through the member, usually at right angles. Crossover joints can similarly be dowelled and tied.

Angled joints

Angled joints are formed where two or more members meet or cross other than at right angles. For butt joints, the ends of the member can be shaped to fit in much the same way as In orthogonal saddle joint. Horns might also be used but fabrication is time consuming. Examples would include web members in trusses. Angled crossovers can be dealt with in much the same way as orthogonal crossovers, for example the diagonal bracing in the plane of roof.

Through joints Members of differing diameters can be joined by passing the smaller through a hole drilled in the larger. The joint is secured by a dowel passing through both members; applications for this type of joint might include partitions, doors and window framing.

Fig-26 Angled joint

Department of architecture, College of Engineering Thiruvananthapuram

Fig-27 Through joint

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Improved traditional joints The mechanical performance of traditional bamboo joints can be improved by the adoption of the following procedures:

Form joints at or near nodes: Nodes are more resistant to splitting than internodes. It is therefore good practice to make joints as close to nodes as possible. For example, in the simple saddle joint, the saddle should be formed directly above a node.

Minimize on holes: It is generally accepted that holes, cuts and notches will reduce the ultimate strength of a bamboo culm. If a hole is made in a culm (for a peg, dowel, mortise, inset support or insert) this should be as close as possible to the node, paying particular attention to the direction of the applied force. Furthermore, whenever possible holes should be round or radiused rather than square cut as these are less likely to propagate splits.

Use seasoned culms: Seasoned rather than green bamboo should be used for two reasons. Firstly, bamboo shrinks on drying and this will generally cause joints to loosen. Secondly, drying splits can form which could further weaken the assembly.

Reinforce against splitting and crushing: Tight binding, espcially with wire, can in itself offer good resistance to splitting. In trusses, the use of quarter-round bamboo bearing plates reduces the risk of crushing of the chords by the compression webs.

Improve durability: Preservative treatment of the bamboo and protection from wetting by good detailing will increase the life of the joint. The use of wire is in many cases preferable to bamboo lashings or rope as it is not subject to insect attack.

Recent developments Building on traditional methods and exploiting the strengths and advantages of bamboo, a number of jointing techniques have been developed which offer more structurally efficient solutions to jointing problems. However, their adoption and suitability will depend to a large extent on the cost and availability of materials, equipment and skilled labor. Department of Architecture, College of Engineering, Thiruvananthapuram-16

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Gusset plates: Plywood or solid timber side plates, applied to joint assemblies in trusses for example, and fixed with either bolts or bamboo pegs, show improved stiffness and strength when compared with traditional jointing methods.

Fig-28 Gusset plated joints

ITCR joist: This is a simple joint developed by the Institute Tecnologico in Costa Rica. It comprises a plywood insert glued into slots sawn into the ends of the bamboo elements to be joined. During curing, the assembly can be readily clamped together using Jubilee clips. A disadvantage of this jointing method is that the ends of the culms remain open. It is also difficult to achieve good and consistent quality glued joints in the field.

Fig-29 ITCR joint

Arce Joint: This technique, developed by Dr. Arce of ITCR relies on the use of wooden inserts to reinforce the end of the bamboo and to form the joint. Rectangular blocks, possibly cut from plantation thinning, are turned down at one end to fit inside the culm, which can be reamed to a uniform diameter. Slots are sawn in order to accommodate slight variations in size. The blocks, when glued in place, can be connected using conventional wood fixings, perhaps in combination with steel plates. Fig-30 Arce joint

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filled joint: This is a modification of arce joint, surfaces of the culms to be joined are cleaned with a wire brush. A gap filling resin is used to bond a wooden plug inside the culms. Holes can then be then drilled and the assembly bolted together. Cement mortar can be used in place of a timber plug, in which case the bolts are placed before the mortar is poured. Either system can be used in conjunction with steel or plywood gusset plates:

Das clamp: Steel bands with integral bolt eyes are fitted around bamboo sections. The action of bolting two or more elements together tightens the clamps around the culms. Additional steel straps can be used if required. This method, designed by the Bhagaipur College of Engineering in India, would be best suited to connections in one plane, e.g. trusses. Fig-31 Das clamp

Herbert shear pin connector: In this method, developed at the UK Building Research I Establishment, bamboo elements are bolted together at sections reinforced with thin gauge steel sleeves. The sleeves art fixed using a series of small diameter pins, which act to transfer the load to the bamboo. Although strong, the joint is bulky and laterally unstable as in-plane connections are not possible, Other methods of fixing suggested include binding, rather than pinning, and the use of sleeves with integral teeth.

Gutierrez joint: This technique is interesting because it exploits the compressive and bending strength k bamboo but does not require it to transmit shear or tensile forces. This is achieved by passing a steel bar through the center of the element and welding a steel plate at both ends. The Parading ends of the steel bars can then be welded together to make a joint.

Fig-32 herbert shear pin connector

Fig-33 Gutierrez joint

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Steel or plastic insert connector: Angled joints can be formed by tightening bamboo elements with slotted ends around prefabricated tubular steel connectors using Jubilee clips, Expanding plastic inserts have been used for straight connections.

Bolts: If the expected forces are not too high, it is sufficient to screw the bamboos together. The concrete injection therefore is unnecessary. Threaded bolts and screw nuts proved themselves since they can be cut easily to the needed lengths.

Bolting with steel tabs/plates: To transfer tensile forces, steel laschen on the sides of the calm are mounted with bolts through the internodes which are filled up with concrete afterwards. So the enormous tensile strength of bamboo can be used.

Fish mouth: If the culm meets perpendicular another, a fish mouth guarantees an actuated/frictional connection. For fee manufacture both chisels as well as special drills are Suitable. With the special drill, the 'fish mouth' can be produced fast and clean, although this is the more Expensive way.

Concrete reinforcement Bamboo as a reinforcement in concrete has some advantages but more disadvantages, as will be explained shortly. These can be overcome, but quite some effort is required. This means that the structural design is basically wrong, and that the designer should look into a different method such as using arches and vaults of material like brickwork or dried soil instead of beams and floors of reinforced concrete. Despite these reservations, bamboo as a reinforcement will be dealt with now in detail.

Bamboo as a Cheap Reinforcement Bamboo as a reinforcement of concrete has an advantage over steel reinforcement in that steel is expensive and often requires foreign currency, whereas bamboo is cheap and is often a local material. In concrete, the common tensile stress in steel is 160N/mm, and in bamboo 20 N/mm2, a ratio of 8:1. The mass per unit volume is 7850 and 500 kg/m3 respectively, a ratio of 16:1. Consequently, bamboo will be cheaper because the price by Wight of bamboo will be less than half that of steel.

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Bending Moment A second point to consider is the allowable bending moment in a beam with a cross section We will compare steel and a bamboo reinforced concrete beam:

bh.

Steel reinforcement, concrete cracked, and stress in steel 160N/mm2 M = 0.9h x 0.6 bh/100 x 140 = 0.76 bh2; Bamboo reinforcement, concrete cracked, stress in bamboo 20 N/mm2. M = 0.75h x 4 bh/100 x 20 = 0.60 bh2; The allowable moment in a concrete beam with bamboo reinforcement is about 78% compared with steel reinforcement. This is not bad.

The width of the crack The stress in a steel reinforcement is 7 times that in bamboo, and the young’s modulus I of steel is 10 times that of bamboo. Consequently the strain in a beam with bamboo reinforcement is about1.5 times that with steel reinforcement. With steel, the strain is 0.67x 10.3, and with bamboo it is 1x10.3.

Deformation: For a concrete beam with steel reinforcement, the deformation is 1/1000 of the span, while for a beam with bamboo reinforcement this is between 1/1000 and 1/500.

The bond between bamboo and concrete In the case of steel reinforcement, this problem does not exist. The dimensions of steel reinforcement rods can be considered to be constant, but concrete shrinks. This shrinkage causes a kind of pre-stressing to the concrete around the steel bars and, as a result, a bond between the steel and the concrete. Department of Architecture, College of Engineering, Thiruvananthapuram-16

Fig-34 Bamboo reinforcement

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In that case of bamboo, however, the bamboo will normally shrink more than the concrete and no bond will result. Drying causes the shrinkage of bamboo. When fresh concrete is poured, its water will moisten the bamboo; then, during the next month, the concrete will harden and lose water so that the bamboo will again dry out. This drying process can result in shrinkage of the bamboo exceeding four times that of the concrete. Clearly, this drying process will completely break any bond between the bamboo and the concrete. Four possible solutions are as follow

Technique 1: Consists of melting bitumen and applying it to the bamboo strips uniformly with a brush to form a thin coat; while still hot, the bamboo is covered with coarse sand for 24 hours. The bitumen has proved an effective moisture barrier and the sand makes a very rough surface thus improving the bond. Technique 2: Uses the bitumen, as before, but 25 mm nails are driven into the bamboo Strips 75 mm apart, so that they protrude on either side of the strip. These nails will maintain the bond. Technique 3: Again uses a bitumen coat, but the bond is provided by roughly 3 mm diameter coconut fiber ropes wound around the strips at a 100 mm pitch along their length. The rope is also dipped in hot bitumen before being wound around the bamboo strips. Technique 4: Uses only the outer half of the bamboo because it has a better tensile strength and a better Young's modulus, due to its higher cellulose content. The quality of the inner half is much lower by comparison. Furthermore, the outer shrinks less than the inner part. The bamboo can be split into halves and the outer used as reinforcement while the inner half can be used for other purposes or just thrown away. The split bamboo halves are 10 mm wide, or slightly more, and 3 to 7 mm thick. Three of these split bamboos are then twisted around each other, and the resulting cable is used as a reinforcing bar. Compared with normal bamboo, the twisted bamboo has improved characteristics.

Durability The life of bamboo in concrete is rather uncertain. Concrete is very alkaline (the pH is 13), and this is too high for bamboo; more precisely, alkalinity destroys the pectin which sticks its cellulose fibers together biologically. Consequently, after a year or so, split bamboo changes into a mass of loose cellulose fibers Department of Architecture, College of Engineering, Thiruvananthapuram-16

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because cohesion is lost. Fiber cement in which there, were composite bamboo fibers of about 1 mm diameter, as opposed to split bamboo with a cross-section of around 4 x 1 0 mm, were tested.

Recommendation The practice of using melted bitumen is strongly recommended, both to increase the bond and to protect the bamboo from alkaline attack. With these precautions, a concrete beam with bamboo reinforcement can be designed using the following formula; M = 0.6 bh2 where; M =The bending moment. b = the width of the beam. h = the height of the beam. The bamboo reinforcement should be 4% of the cross-sectional area; the deformation will be then between 1/500 and 1/1000 of the span. If the height of the beam is taken as 1/10 of the span, any good concrete can absorb shear stresses so that special shear reinforcement becomes unnecessary. Regarding the recommended 4% bamboo reinforcement, it may be difficult to find sufficient room for this quantity of bamboo. Sometimes beams are used with a cross-section like an inverted T, the wide flange at the bottom allowing more room for the bamboo Enforcement. This allows 5 or 6% of bamboo reinforcement in order to obtain better strength. Practitioners have to decide for themselves which solution should be chosen: the rectangular beam, or the inverted T. The latter certainly has more space for the reinforcement, it will give problems regarding the design of the mould and pouring the concrete. Finally, do not underestimate the problems you will meet in trying to find space for 4% bamboo reinforcement! Remember the coarseness of the gravel in the concrete: this has to pass between the bamboos, usually it is good practice to use only 1 or 2% reinforcement, with M = 0.15 bh2 or 0.30 bh2 respectively. Once more, the reader should not underestimate the problems with shrinkage and the durability Remember also the recommendation to look into the possibilities of arches and vaults of brickwork or dried soil. Indigenous architecture in several countries shows good examples of this approach.

Bamboo harvesting Bamboo should be harvested during the dry season in the tropics. This reduces beetle attacks, since insects are less active during dry season. Bamboo should be harvested in autumn and winter in subtropical areas. The branches should be carefully removed from the bamboo culms so that the outer skin is not damaged. After harvesting the canes can be stored vertically or horizontally. In the latter case the Department of Architecture, College of Engineering, Thiruvananthapuram-16

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canes should be frequently supported in order to avoid bending out of shape. Canes should be protected from direct sun, soil moisture and rain. There are two ways for drying the bamboo canes. The bamboo poles can be dried for about 6-12 weeks, by allowing good air-circulation while being stored under a shed. Faster alternative is using kilns for drying the canes. In this way the bamboo canes can be dried for 2- 3 weeks. Workability of the canes is ideal when they are dry.

Bamboo preservation The aim of bamboo poles preservation is to prevent the invasion of pests, insects and fungus. If left untreated, bamboo poles may not survive more than about two years. We recommend the following methods for treating bamboo poles:

Immersion Freshly cut bamboo poles are immersed in water for period of 4-12 weeks. During this time the nourishment for insects inside the poles is removed. Streams or ponds are suitable. Ponds should allow circulation of water. Immersion in saltwater is not a suitable technique.

Impregnating coatings Preservation with borate solution is an efficient technique. This method involves the borate/borax salt solution being pressure- fed in the pole until it is seen at the other end of the pole. The culms treated in this technique should be of mature age. The treatment procedure should be applied on the day of harvesting the bamboo. This is a severe requirement.

Heating This method consists of heating the canes, for a short time in kilns to 150°C. Alternatively the canes can be placed into a large container and boiled (cooked) for 25 minutes. In Japan a method of boiling the bamboo in caustic ash solution has been used.

Checklist for obtaining construction quality bamboo poles Depending on the species, 3 to 5 year old bamboo is best for construction purposes.     

The bamboo should be harvested in dry season in order to avoid fungus attack and excess pole moisture. Use the appropriate species for the particular application. Do not expose the bamboo poles to direct sun, moisture and rain. Use only straight portions from the bamboo culms for construction poles. Should be treated against insects and fungus.

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CHAPTER- 3 LITERATURE REVIEWS

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LITERATURE REVIEWS Venu bharati- A comprehensive volume on bamboo By: - VINOO KALEY

Bamboo is perhaps one of the most under-utilised natural resources of the country. Venu Bharati -A Comprehensive Volume on Bamboo by Vinoo Kaley is a book that brings together Kaley’s vision of sustainable development, to make this grass an essential element of the industrial base, and not merely a part of the handicrafts industry. An introduction to bamboo and its usage, it provides a wealth of information on anatomy and composition, preservation, farming, applications, processing techniques and products. Vinoo Kaley was an architect turned artisan and activist. Known to social activists across the country as "the bamboo man”, Kaley was to be found working among traditional bamboo artisans, making and helping to design bamboo products that could be used even in modern urban life. Venu Bharati - A Comprehensive Volume on Bamboo is an account of Kaley's research on Venu, one of the many Sanskrit names for bamboo. Here bamboo is the central point of a larger vision for an alternative mode of development, which would make efficient and rational use of natural resources in creative ways. India is home to almost 45 per cent of the world's bamboo forests. But irrational and inefficient harvesting gives us ridiculously low yields. The uses to which the bamboo is put are also not optimal. For instance, Kaley calculated that a tonne of bamboo creates upto 350 person days of work in the artisanal sector. By contrast it creates 12 person days in a paper mill which also needs large quantities of water and electricity. Kaley's energy was focussed on expanding a “bamboo sector" which would not only boost the traditional bamboo artisans but give livelihood to millions of others. Venu Bharati is both a documentation of the various bamboo species of India and also an analysis of how and why this resource is being misused. Bamboo is also one of the world's best natural engineering materials, growing much faster than wood and needing relatively little water. Kaley explains why bamboo is a key element in maintaining the ecological balance and ensuring sustainable food and livelihood security. In the chapter regarding the history and background of bamboo, kaley has pointed out the presence of bamboo from the early years dating back to about 4800 to 5200 back in the Zejiang Hemmdu site in China. He also mentions about bamboo in India’s ancient literature. The first reference about bamboo is made in Rig veda(5000 BC). In Valmiki Ramayana also use of bamboo is mentioned. Kautilya in his famous work Artha Sastra also mentions the trade of bamboo as one of the most important source of revenue. Sukra –Neeti also mentions bamboo craft as one of the 64 principle arts placing it in Krithi Gnana (Action science) category. Kalidasa has compared Department of Architecture, College of Engineering, Thiruvananthapuram-16

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surpanakas fingers with the internodes of bamboo. The marati saint- poet Ganeswara compares a true yogi to bamboo. In Indian context bamboo reached dizzy heights when it was used by Srikrishna.

Structural adequacy of traditional bamboo housing in Latin America By: - JORGE A GUTIERREZ

As a construction material, bamboo is widely used in all parts of the world where it grows. In many places, its use is restricted almost exclusively for low-cost housing, usually built by the owners themselves. For this and other reasons, bamboo is customarily regarded as “poor man’s timber” and used as a temporary solution to be substituted assoon as improved economic conditions allow. However, there is a large region of Colombia and Ecuador in South America where bamboo, even if regarded as a second class material by some, has been extensively used in houses that are 50100 years old. Most of these houses have been built in very difficult construction sites like very steep hills, earthquake-prone regions or swampy coastal areas that are frequently inundated. This region has an authentic bamboo culture with a strong tradition of bamboo housing. The problem with traditions is that they are usually transmitted from generation to generation with hardly any changes and without any transfer outside of the region where they were developed. The consequence is that they are often at peril with the advent of new materials and technologies, and tend to gradually disappear. Hence, there is a need to study the traditional design and construction techniques that have been locally developed for bamboo housing in the bamboo culture region of South America, so that the knowledge is closely examined and recorded. For this purpose a research project was submitted to the International Network of Bamboo and Rattan (INBAR), with the following general objective: “To study the traditional design and construction techniques that have been locally developed for bamboo housing in three LatinAmerican countries, and to analyse them through the lens of existing scientific knowledge and sound engineering practice, in order to highlight their adequacies and identify their pitfalls.” The three countries originally proposed as study areas were Colombia, Ecuador and Peru. However, Peru was later excluded because the bamboo used for house construction in the northern part of the country is brought from Guayaquil, Ecuador, and there are no original construction techniques. To study the traditional bamboo houses of Colombia and Ecuador, visits were arranged to the city of Guayaquil, the largest in Ecuador (2.5 million inhabitants). The smaller Colombian cities of Manizales (500 000 people), Pereira (380 000) and Armenia (270 000) – the capitals of the Departments of Caldas, Risaralda and Quindío, respectively, and comprising what is known as “Antiguo Caldas” – were visited. The study team also found time to visit several smaller towns and their surrounding countryside in both countries.

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There are obvious limitations in studies of this kind. In the first place, the time available is always inadequate to fully grasp the complex realities and diverse housing solutions, particularly to someone who is not part of that environment: qualified local professionals do have a more complete understanding of the social and technological environment. Another difficulty arises because the study is intended for a general public and not for specialized structural or earthquake engineers: all aspects have to be viewed from a more general and less technical level. It should also be stated here that analytical theories are of little use for the types of traditional housing that this study deals with because it is practically impossible to produce a reliable mathematical model that could predict their behaviour. And, facts are more reliable than theories. The success of many of the bamboo structures has adequately proved their capacity to resist the passage of time and to survive natural calamities, such as the earthquakes that frequent the region. It is in the empirical evidence of their behavior through the years, and not in theoretical results obtained from complex analytical models, that the adequacy of bamboo structures becomes evident. The report has been organized in several sections. A conceptual framework, developed by the author as a tool to evaluate the quality of traditional or engineered structural designs, is presented first. A fragmented approach does not allow an understanding of the integral structural forms, which are much more than a collection of structural and constructional details. It is hoped that this conceptual system will become a useful methodology for similar studies in other regions where bamboo or other type of traditional houses merit similar evaluations. Second, the characteristics of Guadua, the specific bamboo exclusively used for these dwellings, are presented. The particular region of Colombia and Ecuador where it is introduction structural adequacy of traditional bamboo housing in latin America extensively used is described in terms of its environmental, cultural and socio-economic conditions. The different housing prototypes existing in the region are discussed next, in terms of their evolution and response to the specific conditions. Particularly significant is the construction technique known as bamboo bahareque, not only because of its aesthetics and widespread presence in the region, but also because of its proven durability and success against lateral forces such as earthquakes. The houses are analysed from the perspective of their structural systems and components, describing the use of materials, structural shapes, construction details and building techniques. Their performance during service conditions – daily regular loads and weathering exposure – as well as extreme conditions – severe earthquake and strong winds – are considered. The study examines, in particular, the behavior of bamboo bahareque dwellings located in the epicenter area of the Colombian earthquake on 25 January 1999 that struck the Department of Quindío. The need for adequate technology transfer procedures is stated and illustrated with a successful experience. The study concludes with a summary of the most important characteristics, those that deserve special attention because they significantly contribute to the structural soundness and durability of the houses.

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Bamboos and reeds By:- United nations centre for housing, building and planning United nations has published a study of the world’s most commonly used building materials: bamboos and reeds. The study aims at informing specialists, housing authorities and villagers about new of little known techniques for prolonging the life of bamboo and reed houses and improving their construction. It also seeks to stimulate further research into the use of bamboos and reeds. Bamboos and reeds are the oldest and chief building materials in rural areas and villages throughout the tropical and subtropical regions of the world. Today, in the drive to improve the quality and quantity of housing in developing countries, specialist are seeking more effective ways of using these age old materials. While bamboo and reed housing is easily built, easily repaired, well ventilated, sturdy and earthquake resistant, It has a number of drawbacks. These include susceptibility ti attacks by insects, fire and rot fungus. Bamboo and reed construction is popular for good reasons. The material is plentiful and cheap, the villagers can build their own houses with simple tools and there is a tradition of skills and methods required for the construction. The 95-page study, prepared by the United Nations Centre for housing, Building and Planning, details many of these traditional construction methods and discusses the results of experiments carried out in many countries in recent years to develop new techniques for building. The study is amply illustrated and appendices cover botanical and technical details. Bamboo Bamboos are perennial, grass like , woody plants and their greatest concentration and most widespread use is on the south eastern borders of Asia and on adjacent : islands – from India to china on the mainland and from Japan to Indonesia among the islands. The plants are also found in Africa, Australia, and in the Western Hemisphere, from the Southern United States to Argentina and Chile. Bamboo is divided into four families, an estimated 50 genera, and over 700 species. Each of the species has widely different characteristics affecting its usefulness as a building material. Sixtyfive species of reed are listed in the United Nations study as particularly suitable for building construction. The growth of the bamboo is rapid, about 7 cm (23/4’’) per day, and up to 40 cm (15’’) a day in ideal conditions. Large-scale bamboo plantations have been established in Japan, India, and other countries. The rapid deterioration of bamboo means that, traditionally, structures must be rebuilt

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every two or three years. With proper preservation treatment, however, the life of bamboo housing can be lengthened to 15 years or longer. The possibility of extending the life of a bamboo structure by as much as five field means that larger, better built and better equipped houses can be available to the average villager. The protective treatments, which include water leaching, whitewash and other coating, chemical spraying and dipping, are described in the study. Bamboo suitably treated, can also be used as reinforcing in concrete, pipes or scaffolding. Reeds, like bamboos, are giant grasses. While they are found in almost all countries, with the densest thickets located in the tropics, one of the largest areas of reed coverage is the southern part if the Soviet union. There, the reeds and canes are cultivated by controlling the water level in the reed thickets at different seasons. Reeds grow up to 25’ in height and 1 ¼’’ in diameter. Five varities are listed in the study as particulary useful for building. Reeds can also be preserved against rot and insect attack and treated to increase fire resistance. They have wide applications in buildings from reinforcing to use as compressed slabs.

"Grow your own house”: Bamboo as a construction material By: - ZERI foundation, Latin America The United Nations estimates that at least one hundred million (100,000,000) people in the world have no home. If those with poor quality housing are included, the number is more than one billion (1,000,000,000). (Brown, 1999). And the news only gets worse, as the total number of homeless is growing (Worldwide housing needs are expected to double over the next 50 years. In Africa alone, they are expected to grow more than threefold.) While awareness about the critical need for more affordable housing has grown, the solutions have not. The five leading modern construction materials are cement, concrete, steel, bricks and wood. In the industrialized world, these have been used to build more comfortable housing than ever before. This has contributed to changing living patterns of the middle class, but not for the poor. Steel and cement are symbols of wealth and power - but many people cannot afford them. Bamboo (Vegetable Steel) We need radical new ideas for housing. For example, one of the best structural materials available in abundance is bamboo. It has a matrix of ligno-cellulose, which provides better tensile and compression strength than iron. There are many bamboo species, growing around the world. Bamboos, such as Guadua Angustifolia, have been used extensively as construction material in poverty-stricken regions. Department of Architecture, College of Engineering, Thiruvananthapuram-16

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There are many advantages to using bamboo in construction. It is a highly functional, beautiful, earthquake-indifferent material. Bamboo occurs in many sizes, many degrees of hardness, and many grades of color and occupies a wide range of habitats. It is possible to build multiple-storey buildings with bamboo. Whereas trees must be replanted when they are harvested, bamboo roots sprout up again quickly. The Guinness Book of Records (1999) reports that some of its species constitute the world’s fastest growing plants. Some of its species grow at an incredible rate of 91 cm per day Sadly, though, bamboo is not used in construction. Its potential is lost by the perception that it is for poor people. While the poor often have no choice but to build with these vegetable steels, the rich have only recently discovered the quality of bamboo as a construction material. „Grow your own house“ Colombian architect Simon Velez has designed a two-story, 65 square-meter bamboo home. This beautiful home requires only 100 pieces of five-meter long bamboo, which can be harvested in four to five years on 500 square meters of land. You can now „Grow your own house“. The result could very well be a social housing program that offers beautiful, functional, cheap, earthquakeindifferent houses. It may seem like a dream, and many people still do not think it will work, but the concept initiated by the ZERI Foundation in Latin America has received support in Africa and is being displayed at the world EXPO in Hanover, Germany. The ZERI Pavilion To help promote bamboo as a building material ZERI decided to participate in the Expo 2000 in Hannover, Germany. The organizers of the EXPO had visited ZERI projects around the world and found that ZERI's projects and methodology epitomized the chosen theme of the EXPO 2000, "Humankind, Nature, and Technology." In 1997, the ZERI Foundation was invited to participate in EXPO 2000 with its own pavilion. The ZERI Foundation would be the only Non-Profit Organization with its own pavilion in the area reserved for nations. It was decided that the ZERI pavilion should create astonishing beauty and push new building techniques to the limits, in order to establish bamboo as an accepted building material. ZERI decided to build the pavilion out of bamboo, alizo and arboloco, all trees that are indigenous to Colombia. It would be the only Expo pavilion that could be grown. Simon Velez was enlisted as the architect to design the pavilion. Soon after the building was designed, it became clear that in order to meet the strict German building laws, a prototype of the ZERI Pavilion was needed. It was decided that the prototype should be constructed in Colombia, the heartland of the tropical construction materials to be used in the pavilion and the home of Simon Velez. The pavilion in Manizales took eight months to build in 1999. Two core-building systems, invented by Simon Velez, were used in its construction. First, in order to maximize the traction strength of the material, fine cement is injected into the inside of the bamboo and tightened with copper bolts. This invention allows large bamboo structures such

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as the ZERI pavilion, with overhangs of up to 9 meters, to be constructed at a low price. In fact, the material has better characteristics than steel and cement, while offering a stunning visual effect both inside and outside of the structure. Second, filling two nodes with cement creates joints. Iron rods fix the two bamboo joints to create a strong union. On a weight/strength basis, it outperforms the tensile strength of steel. Prof. Dr. Ing. Klaus Steffens, the director of The German Institute for Experimental Construction Engineering of the University of Bremen, did a series of tests to see if the pavilion would meet German law. The building carried up to 900 kg weight suspended from its 7-meter roof overhang. The second floor was subjected to 450 kg per square meter, and a series of 10 ton, long cable pulls. These tests simulated snow, weight, and wind. The building performed better than anyone would ever have expected. It is perhaps one of the first times in recent history that potential building materials from the tropics surprised the best European civil engineers. Preservation: Smoking the Bamboo The bamboo pavilion in Manizales led to an important rediscovery - preserving the bamboo. While bamboo has been used extensively its use as a structural material has remained limited because once harvested it is quickly infested by insects and fungi. This weakens the inner part particularly affecting the joints. However, bamboo can be preserved for at least 50 years using pyrolytic acid. Burning leftover pieces of harvested bamboo in a large oven smokes the bamboo poles. The smoking extracts the acid from inside the bamboo and evenly applies it to the surface. This is an old technique from Japan. The architect of the Emperor of Japan, Mr. Kiyoshi Yasui, took a personal interest in the transfer of process know-how to Colombia. He also offered 400- yearold piece of treated bamboo to a ZERI delegation visiting Japan from Columbia. With the agreement of the ZERI Foundation and the three developers of the preservation technique, Richard Perl and James Gollin registered the patent for smoked guadua in the USA. Why bamboo is good for social housing Land/Soil Use The problem of 100 million people living without homes could be met by planting bamboo on only 500,000 HA of land. The State of Rio de Janeiro alone, plagued by its bad image of favelas (slums), has an area sufficient for this. Bamboo, Guadua angustifolia and arboloco, Montanoa quadrangularis both grow rapidly in eroded soil, and even in contaminated brown fields, helping to recover the soil and improve its condition in a little over a decade. This provides good news for Africa and other developing regions of the world, which are abundantly endowed with many species of bamboo and other flora. Costs A two-story house constructed by carpenters in Calarca, Colombia, on a cement foundation, costs only 8 million pesos (approximately US$ 5,300 dollar). Doing it yourself drops the costs to an estimated US$ 1,700.

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Local Industry Bamboo has often been considered as a plant without value. Now, however, ZERI has helped show that it can help a local economy and development. This supports the argument that the solutions for the developing world are locally available and need do not be imported from elsewhere. The smoking preservation technique also cuts out imported chemicals. Earthquakes & Storms The bamboo houses designed by Simon Velez can withstand earthquakes. Also they can withstand wind gusts of 100 km/h, and three meters of snow on the roof. Bamboo as a Carbon Sink Too much carbon in the atmosphere causes global warming and the greenhouse effect. Although one cubic meter of mature bamboo sequesters less carbon dioxide than one meter of pinewood, it grows exceptionally quickly and requires a relatively small amount of land. One pine tree requires ten square meters of land to grow. One square meter of land can accommodate two bamboos. So, bamboo captures an estimated 40 times more carbon dioxide per hectare per year than a pine tree. A bamboo-housing program launched in Brazil to "Grow your own house", captures more carbon dioxide than is needed to build the houses. Bamboo - Housing - Where does it go from here? The ZERI Pavilion has demonstrated that bamboo meets the most stringent construction codes (Germany). It has also shown that bamboo buildings radiate a beauty that is appreciated across cultures and classes. ZERI hopes to make bamboo a standard building material in the near future. ZERI will embark on an aggressive campaign to inspire scientists to undertake extensive research on the biology and ecology of Africa’s bamboo species, including the properties of the grass and the economic benefits of various natural products. Efforts will also be made to promote sustainable farming of promising bamboo species. Finally, training programs will be developed in the construction of low-cost, affordable, bamboo houses. The Governments of Malawi and The Gambia are the first to confirm their desire to start building with bamboo. The United Nations Development Program (UNDP) has committed to provide the start-up funds. Simon Velez has a portfolio of bamboo construction projects around the world, from Australia to the Caribbean. In addition, the Vitra Design Museum in Germany has decided to build ZERI-style homes at its training center in the South of France.

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CHAPTER- 4 CASE STUDIES

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CASE STUDIES CASE STUDY 1- Inspiration Architects- Ernakulam Introduction The Inspiration Architects office premises in Eroor, Kerala, covering an area of 2750 Sft, is a first of its kind structure and an experiment where the architects themselves have attempted to develop a technology for using bamboo in floors, walls and roofs in ways that meet our contemporary needs. They have been honored with the National award by HUDCO. Basically, the building is a framed structure designed for a loading condition of approx. 400kg per sq.m live load and to withstand wind speeds of up to 200 km per hour. The basic advantage is that because bamboo is a light material, the entire dead weight of the building has been reduced to almost 1/3rd of a similar building done with conventional RCC slabs and masonry walls. This has helped in bringing down the cement and steel consumption by almost 70%. Fig-35 Inspiration office

The other advantages are the thermal insulation provided by the hollow cavity of bamboo and additional carpet area because of reduced wall thickness. The two storied building is built on column footings about 3 feet deep. The structure stands on stilts, which reduces the chances of dampness seeping in as well as the attack on the bamboo by wood by rodents and insects. All bamboo used has been given preservative treatment. Covering an area of 2750 Sft, the Inspiration office is probably the first and largest of its kind and an experiment where we have attempted to develop a technology (bamboo and reinforced plaster) for using bamboo in floors, walls and roofs in ways that meet our contemporary needs. Bamboo is used in combination with RCC (columns), ferro-cement (beams), and a limited quantity of reinforced plaster so as to arrive at an attractive functional and replicable combination of technologies. It is noteworthy that almost 25% of the bamboo used in the building was cut from the immediate premises of the building.

Department of Architecture, College of Engineering, Thiruvananthapuram-16

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Foundation 

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Considering the weak soil and the high water table the structure stands on column footings about 3 feet deep. Standing the structure on stilts helped prevent the dampness from seeping in and also safeguarded the bamboo from termite, insect and rodent attacks. The maximum load on a column is 30 KN and an isolated footing is provided for the foundation.

Floors, Walls and Roofs   

Fig-36 Foundation

The infill floor, walls and roof of the building are constructed using micro-steel reinforced mortar bamboo composite. Large glazed windows are given all along the inward looking walls which give ample protected lighting and ventilation. The temperature difference between the exterior and the interior averages 4-5 degrees on a hot summer day.

Fig-37&38 walls

Fig-40 Roof Department of Architecture, College of Engineering, Thiruvananthapuram-16

Fig-39 wall corner

Fig-41 Interiors 40

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Loading   

The dead load of the composite is 1500 N/m2 and the live load is taken as 4000 N/ m2 The building is also analyzed for wind and earthquake loads. The maximum load taken by one column is 30 KN and an isolated footing of size 1m x 1m is provided to take the load. The building was monitored for two years on a weekly basis. Observations were made in the X, Y and Z axis for displacement and no displacement was observed.

Fig-42 Plan

Fig-43 Cut away section

Preservative treatment   

All bamboo used on the building has been given preservative treatment. At the time of construction water based pressure treatment with non-toxic preservative chemicals was given. A pressure of 3.5 Kg/cm for one hour was found to be sufficient to achieve a retention of more than 8 Kg/m3 (dry salt) in split bamboo.

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Presently they are into LOSP cold dip treatment for in-situ bamboo. It is a non-hazardous trichlorophenol formulation which can be used to replace water soluble preservatives.

Details

Fig-44 Corrugated sheet- bamboo composite roof slab

Fig-45 Bamboo composite column

Achievements  

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Bamboo replaces almost 70% of structural cement and steel, without compromising on any of the qualities that make use of RCC popular. The self weight of the building is reduced by around 50% in comparison to a conventional building of the same nature, which can be very advantageous when used for a multistoried building as the basic building frame can be made much lighter. This technology can, with some more effort, be easily adapted for standardization and assembly line production of prefabricated components.

Department of Architecture, College of Engineering, Thiruvananthapuram-16

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CASE STUDY 2- Wonder grass group Rural housing for Bengal Introduction Wonder Grass is an international entrepreneurial initiative that strives to bring bamboo based building system in the mainstream of construction-industry. Wonder grass is conceived for : Scale up the operations and cater to large volumes, Provide on- call, efficient building services and ingenious building products, Achieve cost effective and competent building technology with bamboo. The idea behind this is to bridge the gap between the demand for building systems( dwelling units) and building material resource, bamboo.

Rural housing- Material analysis

Design approach   

Expandable Built-form; starting with a Living-unit 325 Sft of built-up area it can grow up-to 700 Sf to built-up area, house with 2 bedrooms. The building components are prefab, modular and assembled on site in span of -2-3 weeks, House is practically ready to occupy in 30 days. Solar-powered LED Light-points, Dry-Sanitation unit and Rain-water harvesting system(500Ltrcapacity) making it a sustainable house.

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Construction 

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Structural-system is primarily made of round-bamboo components fabricated in lattice-formation. The components are designed such that there is an apparent correlation and dimensional coordination between the components. Structural-system is primarily made of round-bamboo components fabricated in lattice-formation. Fig-46 Construction of walls The wall-panels are fixed onto the wall-grid, which is anchored inside the foundation brick-work. It allows opening of any of the wall-panel to make opening, for easy extension on any side. Wall-panels are designed in a module of 3’ X 7’. The wall acts as structural support system with wall-panels coming in and acting as fill-in surfaces. Different materials like wood, MS sheetmetal, FRP to develop an appropriate joints Fig-47 Truss formation for various junctions. Some of the joints we developed in the process and applied for building the pr ototype unit. The application of the joints has helped simplify the overall construction procedure and also helped in achieving prefabrication and assembly on site to be efficient and easy to implement. Corrugated GI sheets have been used as the roofing-material. The sheets are costeffective, lightweight and easy to install. Fig-48 Joinery details Other option is to have Mangalore Tiles with wooden rippers, which will be almost 50% expensive as compared to GI Sheets.

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Fig-49 The wonder grass house

Inferences     

The buildings are strong, durable and long lasting. The proper treating of bamboo helps to reduce the effect of borers to a great extend. The buildings are esthetically appealing. Proper treatment can make the building more beautiful. Various joinery techniques can be used for making building components. The building as such is cost effective and easily buildable.

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CHAPTER- 5 CONCLUSION

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CONCLUSION A hardy, durable product from a renewable resource, bamboo building materials are becoming more and more popular with eco-aware consumers and environmentally responsible designers. Because of other positive attributes and the sustainability of bamboo as a natural resource, it is becoming very common to see bamboo not only as part of a structure, but as the entirety of a number of structures. There are many examples of structures made completely of bamboo       

Walls Support structures Roofs Bridges Houses Flooring Room dividers

These structures are continually built because of not only the aesthetic value of bamboo, but the amazing qualities that it brings to any building. The reasons that bamboo is being used so frequently as a building material include not only the strength of the bamboo but also how it affects the environment. The attributes of bamboo that make it a great building material include: 

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Renewable - While traditional lumber sources take decades to replenish, up to seventy years, bamboo is the fastest growing plant in the world. It can be harvested and then be ready to be harvested again in just months. Strength - Bamboo has been tested to have the tensile strength of light steel. Resistance to pests - Because of a natural bio-agent called bamboo kun, bamboo is resistant to pests and pathogens. This means less rotting and loss of strength. Sturdiness - Bamboo is generally sturdier than the most popular hardwood for hardwood flooring, Maple wood. Flexibility - Because of the nature of bamboo, it is quite flexible when needed, and can be bent into shapes as necessary.

Building with bamboo seems to be the wave of the future. From consumers passionate about the environment, to designers looking for something hip and elegant, all kinds of people are getting interested in bamboo building materials. This renewable resource is slowly emerging out of ancient texts and becoming the modern ideal for building materials.

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BIBLIOGRAPHY 1 –The use of bamboo and reeds in building construction by Narayanmurty & Dinesh mohan 2 –Kerala research programme on local level development, centre for development studies, Trivandrum. 3 – Reeds management plan, Kerala forest department, Trivandrum. 4 – Bamboo: strategies for improvement, in bamboo, people and environment, vol.2, INBAR Technical report no:8 quoted in UNDP 5 – Ochlandra(Bamboo reed): A vanishing assets of forests in Kerala, by Basha, Chand. S. 6 – History of forest management in Kerala, Kerala forest research institute, Peechi. 7 - A comprehensive volume of bamboo. By Vinoo Kaley. 8 - Bamboo biomass, Working Paper, INBAR, Beijing, China. 9 - KSBC, Angamaly: Bamboo based industry in Kerala, Seminar paper. 10 - The Impact of the Working of the Kerala State Bamboo Corporation in m of the Bamboo Industry in Kerala, Ph. D. Thesis, University of Kerala. 11 - Final Report of the Study on Forest Industry commissioned by MOEF, consaltants: Chemprojects Design and Engineering Private Ltd. www.wondergrass.com www.bamboosolutions.com www.bamboobuildingessentials.com

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