CHAPTER No.2 LITERATURE REVIEW

With the interest in development of composite materials, and need of searching alternative cost effective materials, scientists and engineers have tried to utilize as a structural material. The information related to bamboo collected from various publications, books, etc; and through internet, is shortlisted and briefly presented in following heads. 1. Bamboo: The Natural Resource and its Importance. 2. Physical and Mechanical Properties of Bamboo. 3. Structural Properties of Bamboo. 4. Uses of Bamboo. 5. Bamboo Joints

2.1 Bamboo: The Natural Resource and its Importance

Bamboo has a legacy that spans space, time, and culture. A poet has aptly said, 'When the first people on earth came To make the first village, The bamboo was there!' The largest of the grasses, there are over 1600 species of bamboo, 64 percent of which are native to Southeast Asia. Thirty-three percent grow in Latin America, and the rest in Africa and Oceania.

The bamboo has adopted itself world-wide to diverse ecological conditions. The bamboo belt runs through tropical, subtropical and temperate climates around the globe up to 45 degree north and south latitude and upto 3500 m altitude.

Fig.No.4 Area of distribution of bamboo

15 are distributed both in the hills and plains in the tropical as well as subtropical regions of South and Southeast Asia. Over 75 genera and 1250 species of bamboos are reported to occur in the world. About 130 species belonging to 24 genera of bamboos have been reported from India. Out of these, 20 are indigenous and four are of exotic origin. India is the second richest country in bamboo generic resources after China. These two countries together hold more than half the total bamboo wealth distributed all over the world. Bamboo forests are distributed in the States of Andhra Pradesh, Arunachal Pradesh, Assam, Bihar, Himachal Pradesh, Madhya Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura, hills of and West Bengal. These also occur in the Andaman and Nicobar Islands, Orissa, the Western and Eastern Ghats. Very few species occur in the North western Himalayas. Ram Prasad 57 has stated that the total forest area covered by bamboos in the country is about 9.6 million hectares. This is about 12.8 percent of the total forest area of the country. In Madhya Pradesh (M.P.), the bamboos cover more than 1.8 million hectares of area. The major species are Bambusa arundinacea, Cephalostachyum pergracile, Dendrocalamus Strictus and Oxytenanthera nigrociliata. Of these, only D. strictus is exploited on a commercial basis as the other species are found only in small patches. In Madhya Pradesh, bamboo forests are managed on scientific and systematic lines for the supply of raw material to the paper mills and to meet the requirements of the rural population. The felling cycle has been fixed at four years throughout the State. The bamboo forests have been categorised as under: Type I - Good quality bamboos with high density (Hoshangabad, Betul and Chhindwara district) Type II - Bamboo forests of inferior quality and of low density (Bastar, Chhindwara, Seoni and North Raipur districts) Type HI - Good quality bamboos on slopes (Bastar and Kanker districts) Type IV - Bamboos with high density but in scattered patches (Bastar district).

H. S. Thapa, et al has suggested a participatory approach for conservation of plant and species and utilization of resources for socio-economic development of local inhabitant. Bamboo also contributes a good amount of revenue to the state exchequer by regularly supplying a raw material to the paper mill owned by Hindustan Paper Corporation, Silchar. The paper presents the list of species of bamboo found in Mizoram. K.Ravindran39 has detailed main functions of "Bamboo Information Centre (BIC) (India)" which has been set up at the Kerala Forest Research Institute (KFRI) with IDRC funding for disseminating information on bamboo. In China, the results from the recent research activities have already led to significantly improved cultivation, management and processing practices with an increased production of bamboo culms. An improvement in the quality of bamboo

16 products has also been achieved. However, in countries with rich bamboo resources, adequate attention is not paid to the cost calculation of bamboo production. There are regions in the world with a similarly long tradition of bamboo utilization such as Japan and Taiwan. Nevertheless, a distinct decline in bamboo utilization and processing can be observed. The cultivation area and the yield of bamboo harvested have decreased substantially, mainly due to the pressure on land. The general economic and technical development requires costly machinery and, in turn, higher wages, which do not favour the use of a relatively cheap natural material like bamboo for construction when compared with timber or plastic for the manufacture of furniture and other commodities.

The first IDRC workshop on Bamboo Research in Asia was held in Singapore. It can be regarded as a pathbreaking event as numerous conferences and activities have followed since then, such as the IUFRO World Congress in 1981 in Kyoto, Japan; the American Bamboo Society meeting in 1983 at Mayagues, Puerto Rico; the Second International Bamboo Workshop by IDRC and the Ministry of Forestry, China in Hangzhou in 1985; IUFRO World Congress in 1986 in Ljubljana, Yugoslavia; the founding of a European Bamboo Society in 1987; the Second International Bamboo Conference in 1988 in France, and finally Third IDRC supported International Bamboo Workshop organized by the Kerala Forest Research Institute, India. Thus an impressive enthusiasm and activity for bamboo have developed worldwide due to the input by national organizations and international assistance. The World Bamboo Congress87 is a forum to bring together experts from various facets of the bamboo sector, to facilitate exchange of information and knowledge, and promote greater international cooperation contributing substantially to the development of the sector throughout the world. Jointly, these experts represent a collective talent and wisdom that exist in the bamboo sector. The VII World Bamboo Congress was held in New Delhi, India, from 27 February to 4 March 2004. The theme of the Congress was 'Bamboo for Integrated Development'. The previous six International Bamboo Workshops /Congress were held in Singapore (1980); Hangzhou, China (1985); Cochin, India (1988); Chiangmai, Thailand (1991); Bali, (1985); and San Jose, Costa Rica (1998). In his evocative inaugural address, Hon'ble Prime Minister of India, Mr. Atal Bihari Vajpayee, christened bamboo as the 'green gold', replete with potential and promises for ecological and livelihood support to the vast global population. Quipping that bamboo is an 'ordinary' plant with 'extraordinary' qualities, he called it a 'Symbol of strength, flexibility, tenacity, and endurance', which has been 'integral to the daily life of people throughout Asia' for centuries. Beyond its 'over 1500

17 documented uses, from the cradle to the coffin", the bamboo is already creating a new generation of global products to enrich our lives. 'Power generation, pharmaceuticals, water purifiers and filters, innovative industrial and construction applications render it a dependable substitute. 'The VII World Bamboo Congress concluded with recommendations in different areas such as Plantation, Technology, Research and Development, Standards and Codes, Policy issues, Education and training, Machines and tools, Marketing, Networking. Details are available in the reference .

An International Policy Workshop on " Bamboo in Fisheries" was organized by Centre for Indian Bamboo Resources and Technology ( CIBART) India at National Institute of Oceaneography , Goa on 30th Sept- 1st Oct ; 2004. The present author presented a technical paper related to Innovative bamboo products for fisheries sector and coastal areas. In this workshop recommendations related to fisheries gear, packging water transportation and local bamboo resource utilization in fisheries sector have been done.The need of demonstration and improvement in the applications of bamboo for raft

and packaging as suggested in the paper, is recommended in the workshop. %

Limitations in the use of Bamboo10

Many researchers, in all continents, now work on bamboo and are trying to explore its wider application and utilization. Not everyone has sufficient knowledge and experience to appreciate the limitations of bamboo as for any other natural raw material. Some important biological aspects that need to be kept in mind are given below.

1. An increasing demand often leads to premature felling of the culms. This reduces the biological productivity of the remaining culms for new shoots. In addition, the prematurely harvested culms are more liable to splitting and biological attack.

2. Unlike some wood, bamboo does not have any toxic substances to make it resistant. Consequently, bamboo culms remain liable to biological degradation whenever the environmental conditions are suitable for fungi or beetles.

3. Unlike wood, bamboo does not possess anatomical pathways which enable a radial penetration of preservatives. Even worse, its outer skin is highly refractory towards penetration, and any uptake from the inside is also limited

18 4. Many people now realize the great potential of bamboo in the context of declining timber resources. For this purpose, scientists are trying to find ways of improving the growth, management and utilization of bamboo. In addition to knowing about the achievements and positive results, there is also need to be educated about the failures and difficulties in order to avoid them in the future. In recent years many achievements have been obtained through research. These results need to be applied on a larger scale. The research activities so far have mainly been directed towards biological questions and to a lesser degree to the equally important field of utilization. The limited research on the utilization aspects of bamboo is mostly properties oriented and not product oriented. There is almost complete lack of knowledge in the field of marketing research. It must be known, for example, which properties are necessary for the products people want to have. Otherwise they will buy in due course, baskets and other articles made of plastic, which are colourful, durable, and even cheaper than those made from bamboo.

5. Above all, we have to be aware of the limited social acceptance of bamboo by the rural people. If our efforts should lead to a wider utilization of bamboo, we have to consider this social context carefully. If we do not balance our efforts with the market behaviour of the people with their freedom to choose what to buy, we may fail in the application of our work.

2.2 Physical and Mechanical Properties of Bamboo

Fastest growing and highest yielding natural resource (growth rate 70 mm per day and can be as much 300 to 400 mm per day) is typical property of bamboo. The culms complete their growth within period of four to six months. Once maximum height is atta\Yvfid lignification of culm takes place during two to three years. Culm reaches maturity (brownish yellow colour) after fifth or sixth year or more depending on species. The Figure No.5 shows details of typical bamboo culm. Fibre constitutes 60 to 70 % by total weight. Fibre content is greater in periphery than inside. Fibre distribution is highest in the internodes situated at one fourth to one half the total height of culm from the bottom end. Mechanical properties depend on many factors such as species, soil and climate conditions, age, moisture content, extent of seasoning, time of cutting and maturity. Bamboo achieves greatest strength after three years, when it assumes brownish color. In dry state, strength of bamboo is maximum. On average, node is weaker than internode due to number of soft proliferative cells in the growth zone. The culm is tubular and stiffened at intervals by nodes which prevents bucking and collapse.

19 Figure No. 5 Typical bamboo Culm

Important extracts from the references related to physical properties of bamboo:

F.O. Tesoro and Z.B. Espiloy19 has studied Anatomical Properties and chemical properties of bamboos in the Phillippines. They have stated that the fibre length of 13 species ranged from 1.36 to 3.78 mm. It is reported that the length and percentage composition of fibres varied in the horizontal and vertical directions within the internodes as well as from the base, middle to top portions of the culm. Bamboos contain more ash and silica than . It is found that the Philippine bamboos had higher ash and silica content than those of Asian bamboos, but lower lignin content than the Indian species. The silica content increases in a linear fashion from internode 2 of the butt portion (1.6%) to internode 30 (9.9%), in B blumeana. Specifc gravity increased from internode 2 to Hand then remained more or less constant up to internode 30. Results of studies showed a general increase in strength properties towards the top portion of the culm. This trend could be attributed to the corresponding increase in specific gravity and fibrovascular bundle frequency. Li, Xiaobo44, in his Master's thesis has investigated the chemical, physical, and mechanical properties of the bamboo species Phyllostachys pubescens and its utilization potential to manufacture medium density fiberboard (MDF). The result showed holocellulose and alpha-cellulose content increased from the base to the top portion. There was no significant variation in Klason lignin content or ash content from the base to the top portion of the bamboo. Specific gravity (SG) and bending properties of bamboo was varied with age and vertical height location as well as horizontal layer. All mechanical properties increased from one year old to five year old bamboo. The outer layer had significantly higher SG and bending properties than the inner layer. The SG varies along the culm

20 height. The top portions had consistently higher SG than the base. Bending strength had a strong positive correlation with SG. In order to industrially use bamboo strips efficiently, it is advisable to remove minimal surface material to produce high strength bamboo composites. Compression properties parallel to the longitudinal direction were significantly higher than perpendicular to the longitudinal direction.. Fiberboard made with five year old bamboo at 8% resin level had the highest internal bond strength.

Satish Kumar and P.B. Dobriyal 64have carried out works in the Forest Research Institute, Dehradun, on bamboos in relation to their structural use. Different methods available for treating green and dry bamboo with preservative chemicals are described. The density of bamboo varies between 500 and 800 kg/m depending mainly on the anatomical structure, such as the quantity and distribution of fibres around the vascular bundles. Accordingly, it increases from the central (inner most layers) to the peripheral parts of the culm and this variation could be 20-25 percent in thick-walled bamboos like Dendrocalamus strictus. In thin walled bamboos, the differences in density are much less. Bamboos possess a very high moisture content which varies from the bottom to the top and from the innermost layers to the periphery. Green bamboo may have 100 percent moisture (ovendry weight basis) and the variation reported is 155 percent for the innermost layers to 70 percent for the peripheral layers. The variation from the top (82%) to the bottom (110%) is comparatively less. The fibre saturation point of bamboo is around 20-22 percent. Bamboo possesses excellent strength properties, especially tensile strength. Most of the properties depend upon the species and the climatic conditions under which they grow. An increase in tensile and compressive strength up to six years and bending strength up to eight years is known to occur. Strength properties are reported to decrease in older culms. They also increase from the central to the outer part and from the bottom to the top. Although several studies on strength properties have been conducted, the information on strength behaviour and its correlation with various factors such as moisture, anatomical structure, growth characteristics, drying and preservative methods is still wanting. Even methods for evaluating strength properties have not been standardized and the available results are based on inadequate data obtained under different methods of testing and with widely varying dimensions. The limited data show that bamboo is as strong as timber and that some species exceed in strength over the strongest timbers like sal. Variation in moisture content, density and strength along the wall thickness of bamboo is probably responsible for the adverse behaviour of bamboo in use. Green bamboo experiences irreversible and excessive shrinkage well above the fibre saturation point with only partial

21 recovery at the intermediate stages. This behaviour is linked to collapse. Below the fibre saturation point the behaviour is similar to wood. Bamboos dry best under air dry conditions. Rapid drying in kiln may lead to surface cracking and splitting due to excessive shrinkage.

Jules J.A. Janssen 30in his paper has outlined the state of the art on durability, mechanical properties, housing, larger industrial and social buildings, bridges, roads, bamboo-reinforced concrete, woven bamboo and split bamboo for ceilings and walls, bambooboards, and piles and rafts. A comparative study was conducted by Soenardi Prawirohatmodjo69 on the strength properties of six species of green and airdry bamboo of Indonesia. The results show that like in wood, there is a general increase in strength when bamboo is dried from the green to the airdry condition. An exception is Bambusa vulgaris, in which all the strength parameters tested decreased from the green to the airdry condition. This seemed to be caused by an early attack on this species by the powder post beetle, which weakened its strength. The increase in strength from the green to airdry condition of bamboo was much lower than that of wood. For this reason there is not much risk in using green bamboo for construction purposes Us far as strength is concerned.For bamboo, data on the mass per volume have not been recorded as precisely as for wood. It is clear, however, that a common value for bamboo is at least 700 kg/m , and values as high as 800 or even 900 occur quite often (all values are for conditioned bamboo with 12 percent M.C.) Moisture content was determined by Soenardi Prawirohatmodjo69 by oven dry method on two sizes of the samples unsplit round specimens of 2.5 cm length x diameter x thickness of the bamboo culm and split specimens of 10 x 5 cm x thickness of the culm. Analysis of variance of the data showed that the species, position of the specimen in the culm and dimension of the specimen, all have a highly significant effect on the moisture content of the bamboo The variation in airdry moisture content between species, however, is small. In comparison, the airdry moisture content does not vary greatly from the bottom to the top of the culm. Variation in moisture content is also seen between round and split green specimens 49.3 and 57.1 percent, respectively. In the airdry condition, the split specimens tend to have lower moisture content.

2.3 The Structural Properties of Bamboo

Cassandra Adams10 has stated that, Bamboo is unique in that it is strong in both tension and compression. While tensile strength remains the same throughout the age of the bamboo plant, compressive strength increases as it gets older. There is some

22 controversy in determining proper testing protocols, as it is important to test bamboo which is at least three years old, and that the test should occur on a piece of bamboo with an entire internode and two intact nodes. Some testing research has not used these criteria, and thus the results are not as useful.

Bending Strength (Modulus of Rupture)

Soenardi Prawirohatmodjo69 has tested specimens of bamboo in round and split forms. The length for round specimens was 76 cm if with nodes and 30 cm if without nodes. For split specimens, the size was 30 cm x 2 cm x culm thickness, with or without nodes. Tests were carried out using the Baldwin Universal Testing Machine with a span of 70 cm and 28 cm for specimens of 76 cm and 30 cm length, respectively. Analysis of variance shows that moisture content (green orairdry) and species have a highly significant effect on the bending strength of bamboos whereas the presence of nodes does not significantly affect bending strength. In general, there is an increase in bending strength from the green to the airdry condition. However, this general trend does not hold good for all the species. Exceptions are Bambusa vulgaris and Gigantochloa apus. Assuming that the fibre saturation point of bamboo is 20 percent (Liese, 1980), the increase in bending strength from green to airdry condition is 0.05 percent per one percent decrease in moisture content. This value is lower than that of wood which is approximately four percent per one percent decrease in moisture content. Jules J.A. Janssen30 has stated that, in case of bending, the deformation is usually more important than the strength, and the Young's modulus should be discussed. For dry bamboo the Young's modulus values can be as high as 20 000 N/mm . Referring to creep in bending, this is of no importance. The author has found that creep in bending is only 10 percent of the immediate deformation, and the remaining deformation after unloading is about 3 percent (M.C. 12%, initial strain level 2%, duration up to 14 months)

Compression Parallel to Grain (Maximum Crushing Strength)

Compression parallel to grain tests has been conducted by Soenardi Prawirohatmodjo69 on two specimens; 10 cm length for the unsplit round bamboo with and without nodes and 3 cm x 1 cm x culm thickness for split specimens. Analysis of the data shows that moisture content (green and airdry) and species have a marked effect on the maximum crushing stress and the presence of nodes does not significantly affect it. It can be seen that there is an increase in maximum crushing stress from the green to the airdry

23 condition with the exception of B. vulgaris. By assuming that the fibre saturation point of bamboo is 20 percent (Liese, 1980), the increase in crushing strength from green to airdry condition is 4.9 percent per one percent decrease in moisture content. This value is lower than that of wood which is approximately six percent per one percent decrease in moisture content. Jules J.A. Janssen30 has suggested correlation of ultimate compression strength with mass density. The ratio between the ultimate compression and the mass per volume has been studied by several authors, both for wood and bamboo. The ratios are: for dry bamboo (moisture content 12%): CT = 0.094p for green bamboo (moisture content 60% or more): CT = 0.075 p , in which: CT = ultimate compression stress in N/mm andp = mass per volume in kg/m The ratio gives dry bamboo slightly higher compression strength of 0.094 as compared with 0.084 for dry wood. This might be caused by the higher cellulosic content of 55 percent in bamboo compared with 50 percent in wood. This comparison is a rough one since bamboo and wood consist of a number of different varieties, and this comparison deals only with mean values. However, such a comparison will make clear in which cases bamboo might be a good alternative, or even a better one, and in which cases the use of bamboo should be rejected.

Tensile Strength

Tensile strength parallel to grain was determined by Soenardi Prawirohatmodjo69 using specimens of size 30 cm x 4 cm x thickness of the culm. The shape and size of the specimens prepared were such that they were narrowed at the center to a width of 1 .0 cm. A special grip designed for this test was used in the UTM. Analysis of variance of the data on maximum tensile stress shows that moisture content and species do not have any significant effect on the tensile strength of bamboo. There is an increase in tensile strength of bamboo from an overall mean of 29776.1 N/cm2 when green, to 31530.5 N/cm when airdry. An exception is, however, found in B. vulgaris. By assuming that the fibre saturation point of bamboo is 20 percent (Liese, 1980), the increase in tensile strength from green to airdry condition is 1.3 percent per one percent decrease in moisture content.

Shear Strength

Shear strength (parallel to grain) was determined by Soenardi Prawirohatmodjo69 on two different specimens of size 8 cm x diameter x culm thickness for

24 round unsplit bamboo and 4 cm x 5 cm x culm thickness for split specimens. A special jig was used to carry out the tests. An analysis of the data shows that there is significant difference among species and the presence of nodes does not have a significant effect on shear strength. It can be seen that there is an increase in shear strength from an overall mean of 800.5 N/cm when green, to 824.0 N/cm\ when airdry. An exception is found in B. vulgaris in which shear strength decreases when airdry. By assuming that the fiber saturation point of bamboo is 20 percent (Liese, 1980), the increase in crushing strength from green to airdry condition is 0.65 percent per one percent decrease in moisture content. Jules J.A. Janssen30 has stated that, according to a common belief, bamboo should be weak in shear. This is simply not true. The shear strength of wood and bamboo correlates positively with the thickness of the cell walls and negatively with the percentage of rays. One can derive the following formula for wood: z = 0.027p- 0.22 R in which, z = ultimate shear stress in N/mm2, p = mass per volume in kg/m3 and R = percentage of rays (see Janssen, 1981). Data for p and R can be taken from several handbooks. For bamboo, this formula becomes: z = 0.021 p instead of 0.027 p. Taking into account the standard deviations, 0.0044 for the mean value 0.021, and 0.0067 for the mean value 0.027, these mean values do not differ significantly. In spite of this factor 0.021, which is lower than 0.027 for wood, bamboo appears to be strong in shear, not only due to the absence of rays, but also due to the high mass per volume. However, in practice, shear in bamboo is a problem. We can understand this discrepancy if we compare a beam of bamboo with one of wood. For example, say bamboo has an outer diameter of 100 mm and a wall thickness of 6 mm. In order to have the same moment of inertia, the wooden beam has to be 41 x 82 mm. Consequently, the crosssectional wW-iin the neutral axis is 2 x 6 = 12 mm only in bamboo, and 41 mm in the wooden beam. This difference in size causes difficulties in shear in bamboo. In summary, therefore, bamboo is stronger in shear than wood, but its hollow form causes more problems in shear than in the case of wood.

Table No.5 and 6 gives ultimate tensile and compressive strength of bamboo alongwith modulus of elasticity. One main problem is that no agreed standard exists for test. Therefore comparison of results is very difficult. From tables, it is seen that compressive strength of bamboo is nearly 50% of ultimate tensile strength. Bamboo is very weak in shear. Shear strength of bamboo is nearly 8 to 10 % of compressive strength. In case of bending, failure occurs not because of shortage of tensile strength in fibre, but because of incohesiveness between the parallel fibres in which shear plays a very important role.

25 Table - 5 Ultimate Tensile Strength and Modulus of Elasticity of Bamboo

Location Species Ultimate tensile Modulus of elasticity strength N/mm2 N/mm2 Egypt Arundinaria gigantean Green 115.0 11257.0 Seasoned 188.0 18612.0 India Batamana 106.4 14420.7 Chiwli 202.8 24623.1 Perai 151.6 14911.2 Farasmana 115.3 17658.0 Dendrocalamus strictus 102.5 13300.0 d. strictus 89.9 16600.0 Bambusa balcoa 96.5 16548.0 Indonesia d. giganteus 180.1 12013.7 d. asper 200.1 11975.4 Gigantochloa 173.3 9061.2 b. vulgaris var. striata 117.3 5950.0 g. apus 198.7 5666.2 g. otter 259.5 12794.7 g. pseudoarundinacea 230.0 11550.0 b. arundinacea 112.0 5053.3 Malaysia b. vulgaris var. striata 295.4 — d. asper 440.6 — b. blumena 372.8 — d. giganteus 319.4 ~ Thailand Thyrosostachys oliveri gamble 257.9 19788.7 Philippines b. spinosa 138.0 13859.0 Table - 6 Compressive Strength and Modulus of Elasticity of Bamboo

Location Species Comp. Strength Modulus of N/mm2 elasticity N/mm2 Egypt Arundinaria gigantean Green 29.0 4600.0 Seasoned 87.3 6700.0 Indonesia Dendrocalamus giganteus 59.1 — d. asper 55.5 — Gigantochloa robusta 50.0 — Bambusa v. var. striata 40.9 — g. apus 37.3 — g. atter 68.6 — g. pseudoarundinaacea 61.8 -- b. arundinacea 28.4 — Malaysia b. vulgaris var. striata 50.5 — d. asper 64.7 ~ b. blumena 56.2 ~ d. giganteus 44.7 — Thailand Thyrosostachys oliveri gamble 55.3 19350.0 seasoned Philippines b. spinosa 35.0 — b. spinosa 45.0 9350.0 Reference for Table 5 & 6 : Natural Fibre Reinforced Cement and Concrete by Blackie, edited by R. M. Swamy.

26 U.C. Jindal89'90 has carried out research work on bamboo fibre reinforced plastic. Jindal ( 1984) studied the mechanical properties of Dendrocalamus strictus (see Table No. 7) and found that the specific ultimate tensile strength of bamboo specimens is nearly six times that of mild steel. This led to the use of bamboo fibres for reinforced plastic composites (Jindal, 1986). In these composites, the bamboo fibres were all aligned only in one direction. Though the maximum ultimate tensile strength achieved was 425 N/mm ', these composites had useful strength only in one direction. In his work, multilayered bamboo fibre reinforced plastic (BFRP) composites with different stacking sequences have been successfully developed using a simple casting technique. These possess very high tensile strength but low ductility. At the same time, the density of these BFRP composites is much less: it is only about 50 percent of the density of the most commonly used glass fibrereinforced plastic composites. The ultimate tensile strength of BFRP composites varies from 264 to 386 N/mm2 depending upon their stacking sequence. BFRP composites with different stacking sequences possess very high tensile strength ranging from 263.9 to 386.1 N/mm2. The multilayered composite with stacking sequence I (fibres in layers inclined at 0°, 22.5°, 45°, 67.5°, 90°, -67.5°, -45°, -22.5°, 0° to the direction of loading) possesses the maximum ultimate tensile strength, with a mean value equal to 386.1 N/mm2. The mechanical behaviour of multilayered BFRP composites with different stacking sequences is brittle but strong. The BFRP composites can be used for variety of structural applications where strength and lightness are the important considerations.

Table - 7 Ultimate Tensile Strength of Bamboo Specimens (Dendrocalamus Strictus)

Specimen No. Remarks Section Ultimate tensile dimension strength N/mm2 mm xmm 1. — 11x3 235.45 2. ... 11 x3 269.69 3. Soaked in Araldite with 8 % hardener 11 x3 222.72 4. Soaked in Araldite with 8 % hardener 11x2.8 190.90 5. Soaked in Araldite with 10 % hardener 11 x3 273.33 Reference for Table 7 - Recent Trends in the Development of the Composite Materials - T' National Symposium organized by Indian Society for Composite Materials at Govt. College of Engg., Pune, held on 5 Dec. 1983.

2.4 Uses of Bamboo in Construction

Cassandra Adams10 has stated various uses of bamboo.Bamboo is useful for different things at different ages. Less than 30 days, it is good as food for eating 6 to 9 months, for baskets

27 2 to 3 years, for bamboo boards or laminations 3 to 6 years, for construction After 6 years, bamboo gradually loses strength up to 12 years of age. Height can be determined in species over 5 cm in diameter by multiplying the base circumference by 58.2. If culms are found to have a ratio of less than 58.2 the bamboo is of lesser quality. History of Bamboo Construction Bamboo also has a long history of use in buildings, being common to the vernacular architecture of China, Southeast Asia and Central and South America. The Chinese could span up to ten meters with their corbelling technology, and bamboo has been used extensively all over Indonesia, especially in the Celebes Islands. In Hong Kong, all for highways construction is built of bamboo, and tied with bamboo strips only 1 mm thick. Although they have a great history of building with bamboo, today the Japanese use it only for their traditional tea . Uses of bamboo in construction can be categorized as stated below. Bamboo Use in Building Bamboo has been used traditionally since ancient period for the construction of houses in rural area. Recent advancement in method of construction of bamboo houses available in the literature, reflects the efforts towards better utilization of mechanical properties of bamboo.

Fig. No.6.0 Traditional Use of Bamboo for Construction of Houses/ huts

Harendra Nath Mishra has stated that bamboos have great potential for making housecomponents such as trusses, purlins, roof grids, wallings etc. Intuitional me of bamboos has proved to be unsatisfactory with a service life not exceeding tuv to three years

28 during which occasional repair or replacement is also warranted. In comparison a scientific use of bamboo can ensure a long troublefree life. In his paper, the utilization aspects of structural bamboos are illustrated based on techniques developed in the Forest Research Institute and Colleges, Deharadun.

Fig. No. 6.1 Bamboo as Purlin and Rafter The design of this structure emphasizes on maximizing the length of the individual elements, but at the same time keeping their effective length short. This is achieved with supports of four Guadua canes each and braces between them. The crossing poles are connected together with a bolt: The bolt divides the effective length, reduces slenderness ratio and, consequently, increases load capacity. Ref: www. conbam.de

Purlins-Purlins are important components of a rooting system which act like beams, support the roof grid and transfer the roof load to the trusses below. Long, straight and comparatively small diameter culms having thick walls are selected as purlins. These are fixed over the nodal points of the trusses by wiring them with the top chord encompassing some prefixed bamboo pins there. Roof Grid-The roof grid is made by bamboo reeds or half or quartersplit bamboo culms. The individual pieces are first fixed over the purlins 25 cm apart like rafters running from eave to ridge. These are then properly wired or caned with the purlins.Similar members are wired over these perpendicularly with similar spacings to constitute a grid system to contain the roof covering materials. Roof Covering-Corrugated galvanised iron sheets or coconut or palm leaves, grass etc. can be used as roof cover. Some Common Bamboos for Structural Use Bamboos with a greater wall thickness having close nodes and which grow on ridges and warmer areas are often considered good for structural use, particularly for use in columns, beams, roof, rafters, purlins and trusses. Depending on the availability and cost, the species given in Table No.8 may be selected for construction.

Jules J.A. Janssen 30-31 has detailed the state of the art on durability, mechanical properties, housing, larger industrial and social buildings, bridges, roads, bamboo-reinforced concrete, woven bamboo and split bamboo for ceilings and walls, bambooboards, and piles and rafts.

29 Table No. 8 Some Common Bamboos for Structural Use

Name of Species Commonly available Suitability for (Local Name) Culm Length Diameter in in m cm Derdrocalamus strictus (Hindi 5 to 15 m 2.5 to 5 cm Structural use. bans,Kaban, norbans) available in deciduous forests and cultivated through out Indian plains Bambusa tulda (Hindi Peka) Strong 6-20 m 5-10 cm construction of roofing culm and scaffolding Bambusa arundinacea (Hindi Bans) 20-30 m 10-20 cm rafters, houseposts, tent Thorny bamboo poles, etc. Bambusa polymorpha (Bengal and 15-24 m 7-15 cm walls, floors and roofs of Assam Betua) available in eastern houses India Bambusa vulgaris (Bengal Basini 20 m 5 to 10 cm roofing and scaffolding bans) found all over the tropical region

Bamboo for roof Cassandra Adams10 : A number of cultures have used bamboo for roofing materials. The Chinese used bamboo for roofs with the ends covered with round tiles. In the Philippines, roofs of interlocking split bamboo are created with the part receiving the water being the soft inner surface of the bamboo. Unfortunately, this technique encourages mold, fungus and splits from ultraviolet exposure, and roofs made in this fashion rarely last more than a year. These roofs can be made to last longer if the upper pieces, where the denser exterior of the bamboo is exposed, are laid close together, protecting the more vulnerable pieces underneath. These roofs are perhaps most appropriate as temporary roofing solutions. It is imperative that bamboo roofs are treated to extend their longevity. A boric acid/ borax solution is used to preclude fungus and insect infestation. Roofs can also be treated with lime to protect them. Long lasting tiles made with bamboo utilize a bamboo strip reinforced fiber-cement laminate where the bamboo strips are weaved into a web for additional strength. A variety of techniques have been developed to create roof support systems. These include a prefabricated triangular truss system comprising of units eight meters long. These trusses can be carried by only four people, and only deflect 2 1/2 centimeters along their entire length. These frames are then covered with bamboo boards, lath and plaster to create a waterproof roof. Additional systems include A-frame and space-frame roof structures. An excellent system utilizes bamboo rafters with bamboo boards. This is plastered on both sides, and fired clay tiles are used to waterproof. Besides structures built of whole bamboo, truss systems have been developed using flat bamboo strips which are connected with bolts .

30 Fig.No. 6.2 Bamboo for supporting Roof.

The supports consist of four pairs of Guadua poles each which are clamped into the foundation to be bending resistant. The curved shape of the posts is inspired by the natural growth form of Guadua culms. The projecting roof provides protection from weather.

Ref: www. conbam.de. A roof for a kiosk( open -fronted booth selling newspaper, food etc) made by "uneducated" Ecuadorian Indians is an umbrella-like system with a tension ring surrounding it at the level of the eaves. A different radial roof concept with numerous peaks and valleys is held up by tension cables which connect across the structure where the valleys end. Geodesic domes can easily be made with bamboo, as can emergency temporary housing for homeless in the case of earthquake, flood, etc. These roofs are simple bamboo framing with bamboo strips between the main structural members. The roofs described above can last up to 15 years with periodic maintenance.

KIOSK

Fig. No. 6.3 Bamboo as Pavillion for Garden and Kiosk. Jdrg Stamm built 16 buildings of this type, it is used for very different purposes: as a sport place, as storeroom, pavillion in a garden, shelter and so on.

Ref: www. conbam.de .

Due to the hollow body structure of bamboo, the connection possibilities of conventional lumber can be only partially applied. By injecting concrete into the internodes and adding steel reinforcement it is possible to produce very stiff connections.

31 Fig. No. 6.4 Bamboo for Stage Canopy

This stage with a canopy from Guadua is situated in the 'Parque de La Vida' in Armenia. Armenia is known as the center of the Guaduas, this is why there can be found many Guadua constructions.

Many meeting-places and sports places have a roof because of the high precipitations and sun radiation in the tropics. Furthermore the climate demands open as well as semi-open buildings to provide good air ventilation inside.

Ref: www. conbam.de.

Fig. 6.5 Use of Bamboo for Church

Church

Simon Velez built this church in the center of Pereira. The roof is supported by bent Guadua culms, which give a gothic and organic impression at the same time. The visitor experiences a wonderful light interior, that is lively as well as devout.

Exterior view

The supports consist of five Guadua poles each, that run from the ground to the roof. This extreme slendemess is made possible with stiffening braces that prevent buckling

Ref: www. conbam.de.

Interior view

32 Fig. No. 6.6 Typical Bamboo Support

Clamped support with four or more members

At least four posts of a support can be clamped to a foundation with cemented connection irons of. The result is a flexurally rigid connection.

Ref: www. conbam.de.

Fig. No. 6.7 Typical Bamboo Dome

Bamboo is a fascinating building material; examples of bamboo-architecture possess a natural aura, which is not reached using other materials. In doing so bamboo unites almost all positive properties: It is good value for money, non-polluting, enormously sturdy and also earthguake-proof! Bamboo provides a wide range of possibilities which is not fully used so far. So production, processing and use of bamboo gives an opportunity to people, who recognize, estimate and know to use its potential • Ref : WWW. conbam.de. Bamboo Dome, Christoph Tonges

G.N. Boughton and R. Chavez Jr.21 have examined the performance of a number of low cost houses in cyclones in the Philippines and established the areas in which it could be improved. Many of the houses incorporated bamboo in the structure though few relied on it exclusively. In most cases the bamboo had adequate strength to carry the wind loads but the connections of the bamboo members could not sustain the loads for the duration of the typhoon. They concluded that nailed connections will not hold all species of bamboo during typhoon loads, as the bamboo has a tendency to split, allowing it to pull over nail heads. In securing split bamboo minor members in roof structures, a combination of nailing and tying with a single turn of nylon fishing line at every crossing point appears to be very successful.^'all bracing must be used with bamboo wall cladding materials to prevent excessive cracking. Wall braces must be securely tied both at the top and bottom to function effectively. To that end, members built into walls are most efficient, because the lateral support offered by the wall allows them to carry loads under compression as well as tension.

33 Bamboo as Concrete Reinforcement Cassandra Adams10 has stated that many studies have been done to determine the feasibility of using bamboo to reinforce concrete. The problem is, however, that bamboo soaks up the water in the concrete, causing the bamboo to swell and then shrink, the process of which can break the concrete. In addition, adhesion between the bamboo and the concrete is poor. Feasible uses of bamboo with concrete include making stirrups with 9 month old bamboo. Also tanks can be made by applying cement plaster to bamboo baskets. These can be used for toilets, water storage of boats. Waffle slabs of concrete can be formed utilizing bamboo baskets to create the void spaces. Woven bamboo mesh at 6" on center can be used to reinforce a 5" concrete slab. All-in-all, it is not recommend the use of bamboo with concrete in house construction, with the exception of it being used as reinforcing for slabs on grade. F.O. Tesoro and Z.B. Espiloy19 stated that Concrete members reinforced with well dried bamboo splints treated with a thin coat of asphalt emulsion withstood loads better than members with untreated splints. Laminated bamboo sheets, panels, boards, flitches and other forms of construction material for structural and decorative parts of houses, boats and furniture have been developed by FPRDI and were granted Utility Model Patent No. 43 by the Philippine Patent Office. Dommalapati Krishnamurthy13 has carried out research on bamboo-reinforced cement concrete building components by employing new techniques to solve the shrinkage- bond problem. Three different techniques have been tried to improve the bond characteristics of bamboo. The technique, in which, bitumen treated coir rope is wound round bitumen dipped bamboo to obtain a ribbed surface, proved to be the best. Strain measurements revealed that these beams behaved similar to conventional beams in bending and that the theory of reinforced concrete could be applied in the design of these members. Load deflection curves showed that the deflection is greater than that found with conventional beams and is around 1/175 of the span. All the beams with three to four percent of bamboo reinforcement failed by developing flexural crasks.Some of the beams in which one to two percent of bamboo reinforcement was used failed in diagonal cracking and the bamboo strips broke at failure revealing the perfect bond that could be achieved through the new technique developed in this investigation. The designs of two basic bamboo-reinforced concrete elements which can be used to delvelop a system to mass- produce small housing units to suit the rural poor are also included. Building with bamboo can be a plausible solution for housing the millions of homeless poor. The magnitude of strain noted in the tests at the level of bamboo reinforcement is of the order of 0.003 at the

34 first crack load and thus for design purposes this value may be limited to 0.002 for the limit state method of analysis and design. The ultimate moment of resistance measured from tests and the theoretical values computed are found to be close with a partial factor of safety of two for bamboo reinforcement. This factor is, therefore, suggested for design. P. Ratish Kumar51 has described cost effective bamboo reinforced waste aggregate concrete roof. A prefabricated roofing system is investigated by using waste aggregate concrete and treated split bamboo in place of steel reinforcement. This consists of joists and panels. The normal concrete joists using bamboo reinforcement are cast with Ml 5 grade concrete. Triangular hooks using 6 mm diameter mild steel bars are spaced at 150 mm for resisting shear. The joists are cast on level ground are cured for 14 days either by ponding or spraying water. The concrete panels are cast using waste aggregate and bamboo reinforcement. The wooden moulds are used for manufacture of the panels of size of 450 x 950 x 100 mm. Four splint bamboo strips are provided in the shorter direction. The panels are cured for 14 days and are used with cast finished topside as bottom in the structure and thereby plastering for roof is eliminated. The prefabricated components are thus designed and manufactured indigenously to make them suitable for both rural and urban population. N. Chitharangan 46have given the detailed cost estimate of model house of 3 m x 4 m constructed using various low cost technologies. In his work, bamboo reinforced waste aggregate concrete panels of size 450 mm x 930mm x 75 mm using four bamboo strips in longer direction & fine strips in shorter direction were used. Bamboo reinforced normal concrete joist were considered. The concepts of method of design of RCC elements such as beam, slab & column by working stress method or limit state method can be predicted to find moment resistance capacities of such members with modification. H.Y.Fang24 have demonstrated the study of sulphur sand treated bamboo in concrete environment. The effect of water absorption on bond strength is given. Bamboo Walls Harendra Nath Mishra25has described details of 25 cm thick mud wall reinforced with half/quarter split bamboo culms properly treated with hot bitumen. Lighter Bamboo Walls -Lighter bamboo walls are common in rural housing. They are easy and cheap to make and can last long provided some preservative is applied and maintenance taken care of. Flattened bamboo-culms devoid (free from) of the nodal diaphragm or halfsplit culms are arranged vertically or at a 45" angle to make bamboo boards, which are duly battened and nailed to form the wall. Mats made with skins from the outside of the bamboo are generally used for the exterior wall after applying a coat of coal

35 tar on the outer surface for affording protection against rain. The inner walls are given a paint coating of suitable colour. T.S. Ramanatha Iyer, et. al x8 have carried out experimental work on model retaining wall using bamboo grids. In his study, bamboo strips were used as reinforcing element with and without braided coir rope interface. Ferro cement panels were used as facing elements tied to the reinforcing elements for a model retaining wall with a backfill of sea sand. The reinforcement strips were placed 35 cm apart vertically and the horizontal spacing were varied. The wall was loaded by dead weight of sand bags well distributed to provide uniform surcharge. The lateral movement and vertical settlement of the top of the wall were much less than the coir fabric- reinforced wall used earlier. The construction of these walls is very simple. Bamboo strips of 19 mm width and 12 mm thickness were used as reinforcing strips. The type of bamboo used is locally known as yellow bamboo. The length of strip was 2 m and hence sufficient anchorage length was available. In addition, braided rope of 2.8 kN/ m3 and 14 mm x 7 mm ( averrage size and linear density 1.3 N/m length was fixed on either side of the bamboo strips using fevicol to increase interface friction. The modulus of elasticity of bamboo pasted with braided rope on either side was 11.6 x 10 3N/ mm based on the cross section of bamboo alone. Typical stress strain curve in tension for bamboo strip is given.The study shows that bamboo strips with interface can be used for retaining walls up to 2 m height. More studies are required for their suitability for larger height. Facing units made up of ferro-cement panels and asbestos sheets are suitable for stability of the retaining wall and they can be designed as non load bearing units and they are easy to assemble. Asbestos cement sheets are relatively brittle though cheap but can not stand impact. The high modulus of bamboo and frictional characteristics of braided rope can be best made use of in such constructions. The deformations are much less as compared to coir geo textile walls. The soil retentivity of such facings is also found satisfactory. The durability of bamboo strips and grid can be increased using proper seasoning method like boric- borax treatment or smoking. Bamboo strips subjected to boric-borax treatment give a higher modulus of elasticity in addition to the increased durability. Long term studies are however required to evaluate this aspect. V. Ramana Murthy, G.V.R. Prasad Raju91 have carried out experimental work on pull- out resistance of various reinforcing materials in different Jill materials. The paper presents the suitability and adaptability of some alternative cost effective reinforcing material whose performance is compared with conventional geo- synthetic materials. Murrum, sand and flyash are used as different fill materials and the pull out resistance of various reinforcing strips embedded in these fills is compared with each other. Bitumen

36 coated chicken mesh and bamboo have shown higher pullout stresses than woven and non woven geotextiles. Hence they can be tried for field applications to understand the long term performance. This study revealed that the alternative materials like bitumen coated chicken mesh and bamboo could be tried in place of costly geosynthetic materials in reinforced earth technique. Bamboo in Bridge Construction10 Bamboo's tensile strength has been essential in the development of bridges. The Chinese invented suspension bridges using bamboo to cross rivers. Using only the exterior part of the bamboo, which is four times as strong as the interior, they created tension cables up to 120 meters long. Bamboo bridges were also constructed in India, and by the Incas in South America. In both cases, the structural cable was strung above the walking surface, which hung from it. And in Columbia, tension bridges were created using this amazingly strong material, with tensile strengths of up to 3,200 kg/cm2 for the species Guadua. Similar building techniques have also been used to create gabions to dam, rivers and streams, where a long basket of bamboo is filled with stones with each end secured to the banks. It has been crucial to the development of many inventions. Bamboo has been used to build boats and zeppelins. Jules J.A. Janssen 30' , stated that, Referring to bamboo bridges, we should limit this subject to bridges for pedestrians only. (However, in 1937, the U.S. army in the Philippines, built and tested a bridge with a free span of 1.5 m, which was designed for a load of 16 kN.) Discussing bamboo bridges, researchers again meet the problem concerning bamboo joints. In view of the fact that quite a number of bridges for pedestrian traffic are required in developing countries, research on joints is needed, as well as a method to transfer the technology from the laboratories to the users in the field. K. Ghavami : Bamboos of Brazil have been experimentally used as a substitute for steel in normal and lightweight concrete beams and slabs. Several curing methods and water repellent materials have been considered for reducing their water absorption and improving their bonding ability with concrete. To verify the performance of bamboos as reinforcement in concrete beams and slabs, 11 tests with normal concrete and three beam tests with lightweight concrete were carried out. Some studies have also been carried out in developing new joints for the use of bamboos in space structures. To cover a large space without using many columns, steel truss space structures are usually used. The resistance and form of bamboo are very suitable for such structures. In the construction of structures, the most difficult part is the formation of joints. Several types of joints besides the conventional method of using rope or wire were developed (Ghavami et al, 1984).

37 Fig. No. 6.8 Bamboo Bridge by Jorg Stamni

Pedestrian bridge

An actual project of Jorg Stamm is his bamboo seminar. After six years of experience in this field, Stamm decided to mediate his innovative and practice orientated knowledge. In August 2000, he arranged in cooperation with the german society for technical teamwork (GTZ) and the partnership university in Pereira a comprehensive course of bridge building for architects, engineers and workmen. Under the chairmanship of dr. Samuel Ospina (dean of faculty) and dr. Michael Tistl (GTZ representative of the environmental projects), the course developed a 40 m spanning pedestrian bridge over two lanes. According to the same construction plans a bridge in Tierradentro, Inza came into being. This 30 m long bridge spans over a river.

Bridge in Tierradentro

Ref: www.conbam.de.

38 Other Uses of Bamboo in Construction

Chan, Professor S.L1' has detailed use of bamboo scaffolding. Bamboo scaffolding has been used in building construction for centuries and despite competing steel frame scaffolding systems, is still used for this purpose in many countries, especially in Asia. Bamboo scaffolding provides temporary access, a working platform for construction workers and supervisory staff, and can prevent construction debris from falling onto passers-by. Typical usages include the highly adaptable single-layered bamboo access scaffolding (SLBAS)for light duty work such as exterior decoration, and double-layered bamboo access scaffolding (DLBAS) with working platform for heavy duty work such as masonry work, and installation of curtain walls. Even today, in the technologically advanced and highly-competitive economy of Hong Kong, bamboo scaffolding is used in over 70% of constructions, including high-rise buildings. In Hong Kong, it is one of the few traditional building systems that survive by self-improvement through practical experiences of scaffolding practitioners over the last 50 years. The major advantages of bamboo as a scaffolding material are a high strength-to-weight ratio, simple erection and easy adaptability to building forms and site conditions. Bamboo culms used for both the standards (vertical members) and the ledgers (horizontal members) in scaffolding range from 4 to 10 cm in diameter and 7 to 8 m in length, and are light enough for one person to easily handle a single culm. Due to the ease of handling, bamboo scaffolding is easily and efficiently installed and dismantled; compared to steel scaffolding, where installation and dismantling take the same amount of time, bamboo scaffolding can be dismantled in J/10th of the time it takes to install Machinery, power-driven tools and tightening equipment are not necessary, as simple hand tools and nylon or wire ties suffice to create the scaffolding. The typical height of bamboo scaffolding systems is 15m and the installation of bracket supports at regular intervals allows full coverage of building height up to 100m (30 storeys). Bamboo scaffolding is economical - bamboo culms alone can cost 10% of comparable steel members. Furthermore, it is an environmentally friendly material with many advantages in comparison to its metal competitors, including the overall energy savings and low- environmental impact as bamboo, unlike metal, does not require industrial-level processing. Laminated Bamboo10 Many of the problems associated with bamboo can be alleviated by creating laminates of bamboo strips. These are formed by simply dividing the length of the culm into

39 individual strips which are then laminated together to create a number of products. In 1942 a study was commissioned by the US government regarding the use of bamboo laminates in ski poles. Currently, bamboo laminate products include floor tiles with one type being particularly good for heavy floor traffic as only the end grain is exposed. The softer strips of bamboo from the interior of the culm can be safely used in the interior portion of very large glu-lam beams. There is really no limit to the uses of laminated bamboo. It can be used for chairs and other furniture, plates and utensils. In fact it can be used just like laminated wood, with the advantage that bamboo laminates are much lighter in weight. To create the strips used for lamination, the interior soft part of the bamboo is removed with a plane, leaving the hard exterior for the lamination strip. Bamboo Strips for Aircraft10 I ^ M ° 3 O

A study was conducted by de Leon (J 956) using bamboo- woven mat glued to wood or laminated to another bamboo mat for use as stress skin covering for light aircraft. Its fatigue strength under bending stress was found to be much higher than that of wood, and the bond strength of bamboo to bamboo was comparable to that between bamboo and wood. In aeronautical research, structural members of kites and early planes were constructed using the material as it is light and extremely strong. A plane made completely of bamboo was built in the Philippines, while the Chinese commonly used bamboo in their planes during World War II Plans for bamboo planes were even available in "Popular Mechanics" magazine. Besides Oscar, there are a number of other important bamboo architects in South America. These include recently deceased architect Carlos Vergara from Cali, who made houses entirely of bamboo. He created a multi-column system where the loads are carried by the septum of the bamboo. He also used bolts through concrete nodes to create joints. He was able to achieve spans up to 24 meters with his techniques. Jorge Arcila of Marizales did a series of "stacked houses" and is currently writing a history of bamboo in America. Simon Velez, an architect who mostly practices in Colombia, has built a number of extraordinary bamboo structures. These projects have ranged from horse stable, residences, an observation tower and a country club. His structures feature massive cantilevers and he was the first to use multi-culm beams. He uses a unique bolt and concrete system in the internodes to create extremely strong joints, which has allowed him to create cantilevers as long as 7 metres(37feet). American efforts include those of Doug La Barre, who is setting up a manufacturing facility for creating laminated lumber from imported Guadua. The Truss-Joist corporation is also doing work to create nontoxic adhesives for laminated bamboo.

40 Water harvesting In some drier regions, split bamboos have been used in the harvesting of rain water from houseroofs. In Tanzania, A. alpina has been used extensively as water pipes (Lipangile, 1984). About 100,000 people scattered in 28 villages were being supplied with water through a network of 150 km of bamboo pipelines by 1985. More people are expected to be covered by the project. T.N. Lipangile8 : For the past few years, Tanzania has successfully set up rural water supply schemes by using pipes made out of bamboo conduits. Most of the scientific and technical problems have been resolved to a satisfactory extent. This paper briefly describes the management, handling, maintenance and operation of a bamboo pipe water supply system. S. K. Nath, T.S. Rangaraju ' have presented information about bamboo panels and boards. In the light of scientific development, bamboo has been rediscovered as a potential material to substitute wood. IPIRTI has developed a series of environment friendly and cost effective technologies to manufacture panel products and laminates to substitute wood panel and solid wood. Technology for manufacture of bamboo mat board (BMB ), bamboo Mat Veneer Composite (BMVC) , Bamboo mat moulded articles, bamboo mat corrugated sheet has been developed and transferred to production units for commercialization. Details are available in the references. K.S. Low40has stated that the stiffness and relatively high tensile strength make bamboo suited for use as an earthreinforcing material. With the support of the International Development Research Centre (IDRC), the Forest Research Institute of Malaysia (FRIM) has initiated a research programme for the utilization of bamboo in reinforced earth structures such as highway/road embankments, vertical retaining walls, etc. This paper highlights the work being carried out at FRIM on this aspect. I.S. Uppal26 has stated quick and economical methods of road construction in desert areas and sandy subgrades. It is possible to make temporary tracks for pneumatic tyred vehicular traffic in sandy areas without much cost and loss of time by laying ready made bamboo trellis over the leveled sandy surface. This arrangement also offers a promising solution for compacting sandy embankment and construction of service roads and diversions in sandy and partially marshy areas. For further construction of permanent roads, the bamboo tracks, if allowed to remain there, will serve a good base with high bearing value. Details are available in the reference. Some experimental stretches of bamboo based roads were constructed following the procedure described above, on the

41 sandy sub grades of Kartarpur - Bhallath and Jallundur - Kapurthala road to Adikhni roads in Jallundur District. Deshpande A. P., Bhaskar Rao M, Lakshmana Rao C.12: Investigations have been carried out with bamboo fibres despite its high strength, biodegradability, and low cost. The overall objective of the research work was to investigate fibre extraction from bamboo and the use of these fibres as reinforcement in polymeric composites. A combination of chemical and mechanical methods was used for the extraction of bamboo fibres. Conventional methods of compression molding technique (CMT) and roller mill Technique (RMT) were explored for the mechanical separation. Fibre populationfrom both the techniques were characterized. Mechanical properties of the fibres also were evaluated. Bamboo fibres obtained from CMT and RMT were used to make unidirectional composites of polyester. High values of tensile strength were observed in all the composites. The predominant mode of failure for the composite was shown to be cracking of the fibre matrix interface. Quantitative results from this study will be useful for further and more accurate design of bamboo reinforced composite materials. V.R. Sonti92: The Wirelacing Tool developed by the Delft Centre of International Cooperation and Appropriate Technology of the Netherlands can be used in lacing round hollow bamboos for structural and nonstructural purposes. The system of lacing is simple and inexpensive and prevents any tendencies to split. A 'Geodesic Dome' of approximately 18 m diameter and 9 m height using round CCA preserved bamboos has been put together using this wirelacing tool.

2.5 Bamboo Joints Jules J. A. Janssen 30'35 has stated that "the use of bamboo in building is limited by a lack of knowledge of how to make joints in bamboo. Usually, joints in bamboo structures are complicated and labour intensive, and the structural safety is unknown. Only a few references have been published. Among the temporary structures, the scaffolding is well known. In summary, research is required on joints with an emphasis on strength, safety and simplicity. In the opinion of the author, scientific research can considerably enlarge the opportunities of traditional building methods. " Cassandra Adams10 has stated that, in standard bamboo construction, joints are difficult to make. In bamboo geodesic structures, joints are formed by creating "flaps" at the end of a culm by incising the bamboo radially. The soft inside of each "flap" is cut away, allowing them to bend easily. These flaps are then bent over a cone with a threaded rod sticking out of the tip. An additional cone is placed on the outside of the bent flap area and

42 secured with a bolt. Besides increasing structural strength, this external cone protects against insect entry. This results in an end which can easily be attached to a central hub. Harendra Nath Mishra25 has suggested that Drying and Preservative Treatment operations are mandatory to make effective use of bamboos in construction for obtaining the desired strength and durability. Truss joints etc. made with green bamboos will become loose due to shrinkage of the jointing members resulting in early weakening and collapse. Mature bamboo culms should be seasoned to about 12 percent moisture content. Bamboo Truss Though rafter-purlin construction is still in vogue, trusses are being considered as improved roofing systems for supporting roofloads and for transmitting them to the ground through columns and or walls. When the top and the bottom chords and strut members are properly jointed by suitable fastening devices, a truss can resist compressive and tensile forces conglomerately and as such act as a strong supporting component even against storms and earthquakes. On the basis of design criteria for a 4 m span nailjointed timber truss (crosssection of members about 7x4 cm), bamboo trusses of 4 m span have been designed to withstand stresses of a similar nature though of lesser intensity) and fabricated using culms having an outer diameter of 9 cm and an inner dia of 6 and 7 cm .A fullscale layout of the designed truss is drawn and painted on the floor of the workshop. Selected culms are placed in position. Jointing ends/faces are cut in such a way that the gap between any two members is the minimum. Spikes are driven in the ground at the ridge and support points to maintain the designed shape and size of the truss. Primarily the joints are tightened by 18 SWG wire passed through previously made bores near the joints of the round bamboo pieces and the final jointing is completed using any one of the following methods. Wire Bound Joints Fourteen SWG wires are tightened around the joints by binding the respective pieces together. At least two holes are made in each piece and during winding the wires are passed through them to achieve good results. Pin and Wire Bound Joints Here, bigger holes are made on the culms to accommodate bamboopins of suitable diameter. Fourteen SWG wire is tightened around the pins on both sides along with some additional winding around the culms .

43 Fig. No.6.9 Some Bamboo Joints used in Construction

Already several architects and engineers occupied themselves with the development of a useful connection of bamboo tubes and presented many different solutions, reaching from simple lashing and glueing techniques over combined solutions to complex connections, for example, injecting concrete and transferring forces through screws and steel tabs.

Oscar Antonio Arce-Villalobos, Ref: www.conbam.info. 1993

A sheet metal with a certain order of holes serves as pattern to drill holes for the screws and as a 'washer' for the screws at the same time. The large amount of screws and their regular distribution should provide an good power transmission to the bamboo cross section ie. to its hard outside skin. A connecting means (bolts, sheet metal) is put into the end of the tube and then is filled up with mortar. Prototype 1, Prototype 1 (without C. Tonges, Ref: www. conbam.info. 2002 mortar)

In summer 2002, experiments at the University Aachen (RWTH Aachen) to develop a high-perfomance connection to build bamboo space frames.

Tetrahedron by 'Construction Ref. www. conbam.info. with Bamboo' Fishplated or Gussetted Joints In this case, strong joints are made by placing 25 mm thick pieces of hard wooden planks or 12 mm thick structural plywood shaped according to the configuration of the joint, on both faces of the joint. These pieces are first assembled and kept in position by thin nails. Holes are then bored, two in each of the culms and 3.5 mm diameter nails are driven through them to unite and tighten the plates with the bamboo pieces in between. The diameter of the bores should be slightly less than the diameter of the nails. It is better and also cheaper to replace the nails by bamboo branch pins (solid) of about 8 to 10 mm diameter driven through suitable bores. Horned/Tongued Joint In case of two members meeting at right angles, two horns or tongues are made at the end of the vertical member and accordingly two grooves are cut on the horizontal member to accommodate the horns. The members are then wirebound or lashed, preferably by passing wires through small diameter holes drilled in the jointing members.Here due to cutting of grooves, the member becomes weaker and as such this type of joint is not generally favoured. After fabrication, the trusses are transported to the place of work, erected over the previously fixed wooden (eucalyptus) poles or columns, the tops of which are made suitable by trimming or by adding two wooden plates to accommodate the truss. The truss is then fitted and fixed by at least two bolts in each column . The slope, height, horizontality etc. of the roof are adjusted at this stage. Research work related to bamboo connections have been carried out at Washington State University, Wood Materials and Engineering Laboratory, College of Engineering and Architecture, under title "Design Considerations for Bamboo Connnections". The report concludes that connectors for bamboo assemblies used wood design specifications found in Technical Report 12 (TR-12), General Dowel Equations for Calculating Lateral Connection Values (AF&PA, 1999) which describe design procedures for a variety of wood and steel connections using different fasteners. The mechanics- based procedures described in TR-12 are an expansion of the National Design Specification (NDS) for Wood Construction (AF&PA, 2001) yield limit equations used for design of dowel type fasteners. Mechanics based equations for design on wood and steel connections in double shear taken from TR-12 provided conservative estimates for bamboo connections utilizing the bamboo connections provided by the manufacturer. Methodologies taken from TR-12 are considered a current and effective means for designing wood and steel

45 connections. The TR-12 design methodology under-estimated bolted bamboo connection capacity. These procedures appeared to be appropriate for design of bamboo joints. Jules J.A. Janssen , The use of bamboo in building is limited by a lack of knowledge of how to make joints in bamboo. Usually,/, joints in bamboo structures are complicated and labour intensive, and the structural safety is unknown. Only a few references have been published among the temporary structures, the scaffolding is well known. In summary, research is required on joints with an emphasis on strength, safety and simplicity. In the opinion of the author, scientific research can considerably enlarge the opportunities of traditional building methods. Research Thrusts and Recommendations by Cassandra Adams10 Bamboos are the fastestgrowing and highestyielding renewable natural resource and if managed on the sustained yield basis, can be an inexhaustible source of goods and services. Unfortunately, the extent of harvesting is more than what the bamboo forest resource can produce. As a result, reproduction cannot keep up with exploitation. A bamboo forest can be restored and made productive if exploitation is controlled and combined with natural and artificial regeneration. The lesser used species need to be examined for their structural, chemical, physical and mechanical properties. Studies on economics and on available preservatives should be made with emphasis on suitability and environmental safety. Studies on the use of bamboo in housing and construction including jointing methods, design criteria and construction systems should be vigorously pursued. Furthermore, through a systematic dissemination and promotion campaign, the results of research and development activities should reach the end users. This could be done through various means such as the print and broadcast media, technical manpower development, technical assistance, industry linkages and cooperative projects with media related organizations, and educational, research and development institutions. The ultimate aim of this mode of technology transfer is at reaching the widest audience and the largest number of end-users and consequently, having them adopt the technologies developed. In general, most of the efforts towards the utilization of bamboo as a building material or supporting material, are traditional than technical. Some recent technical investigations related to bamboo composites have been carried out. But there is lack of technical information on bamboo joint and use of bamboo as structural member for plane and space trusses.The joints for plane and space truss and use of bamboo in half splint form as a structural member as proposed in this thesis is innovative. Very often durability of bamboo is questioned,the information about durability of bamboo is separately given in Chapter 3.

46 •