aakash kushwaha has just completed a mini project under the

Fabrication and Elemental

Characterization of Multipurpose

Dismountable Bamboo Geodesic Dome

Submitted By

Aakash Kushwaha

2008CE10238

A report of CED 412 – Project Part 2 submitted

in partial fulfillment of the requirements of the degree of

Bachelor of Technology

Department of Civil Engineering

Indian Institute of Technology, Delhi

April, 2012

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CERTIFICATE

“I do certify that this report explains the work carried out by me in the course CED 411 – Project

Part 1 and CED 412 - Project Part 2 under the overall supervision of Dr. Suresh Bhalla. The

contents of the report including text, figures, tables, computer programs, etc. have not been

reproduced from other sources such as books, journals, reports, manuals, websites, etc. Wherever

limited reproduction from another source had been made, the source had been duly

acknowledged at that point and also listed in the References.”

Aakash Kushwaha 2008CE10238

Date: 30th April, 2012

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CERTIFICATE

“This is to certify that the report submitted by Mr. Aakash Kushwaha (2008CE10238)

describes the work carried out by him in the course CED 411 – Project Part 1 and CED 412 -

Project Part 2 under my overall supervision.”

Dr. Suresh Bhalla

Date: 30th April, 2012

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ACKNOWLEDGEMENT

I would like to express my sincere thanks & gratitude to Dr. Suresh Bhalla for his invaluable

guidance, constant supervision and continuous encouragement during the course of this project.

His knowledge, timely guidance and valuable suggestions and constant motivation at each step

of the project has been instrumental in its completion

I would like to take this opportunity to thank the entire staff at Structures Laboratory, Workshop

and the Civil Engineering Laboratory for their cooperation and assistance in the lab-work that

was required for this project.

I would also like to thank my friends Deepti Chauhan, Ankit Saxena, Akash Rathi, Anubhav

Kumar, Sudatta Mohanty and Vibhav Bisht for their help during the course of this project.

Aakash Kushwaha

2008CE10238

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ABSTRACT Bamboo is a non characterized and non validated material which is readily available in rural

areas in India and has great scope as a building material. It has excellent strength under tension

and compression and can used for construction purpose almost exclusively as well as with

reinforced concrete and has many other applications.

The objective of this part of the major project was to construct a bamboo based geodesic dome of

6 m diameter to cover with a net, to put load at the bottom joints and to obtain the joint stability

of the bamboo. The bamboo used for the fabrication of dome is from Assam. The joints are made

strong after the testing.

The tension testing and compression testing were conducted on the samples. When 2 nodes are

between the joint and the edge, the shear stress observed is greater than the case when no node is

between the joint and the edge. Also the compressive strength of the bamboo with a node is

greater than the bamboo sample without node. Thus the thickness of the bamboo and the position

of node play an important role in the construction of dome.

.

The dome can be used by the rural community for various purposes and being dismountable, it

can be carried to various places. The dome is constructed of only bamboo struts which make it

affordable to everyone.

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TABLE OF CONTENTS

PAGE CERTIFICATES…..………………………………………………………………………………1 ACKNOWLEDGMENT………………………………………………………………………..…3 ABSTRACT……………………………………………………………………………………….4 TABLE OF CONTENTS …………………………………………………………………….…...5 LIST OF FIGURES ………………………………………………………………………………7 LIST OF TABLES ………………………………………………………………………………..9 CHAPTER 1: INTRODUCTION…………………………………………………………..…10 1.1 About Bamboo………………………………….………………...………………………….11 1.2 Bamboo in India….………………………………………….………….……………………13 1.3 Properties of Bamboo………………………….……………….……………………………13

1.3.1 Shrinking and Swelling……………..…………………………………………….. 13 1.3.2 Tension parallel to grain………….………...…………………………………….. 13 1.3.3 Bending……..………………….…………………...…………………………….. 13 1.3.4 Elasticity...………………………….………………………………..…………….14 1.3.5 Fire Resistance …………………………………….………….………………….. 14

1.4 Comparison…………………………………………………………………………………. 14 1.5 Bamboo Used ……..……….……………………………………………………………….. 14 CHAPTER 2: BAMBOO APPLICATIONS ……………………………...………………… 15 2.1 Housing/Construction…………...……….……...………………………………………….. 16 2.2 Bamboo Trusses…………………………………………………...……………………….. 16 2.3 Bamboo Roof Skeleton…………………………………………………………………….. 17 2.4 Scaffoldings…………………………………………………………………………………17 CHAPTER 3: CONSTRUCTION OF GEODESIC DOME ……………………………….. 18 3.1 Geodesic Dome………………………………………………………………………………19 3.2 Engineering Consideration...………………… …………………..………………………….19 3.3 Perfect and imperfect solutions....……………… ………………………………………..….20 3.4 Strut Lengths...…………………………………………………………………………….....22 3.5 Joint ………………………………………………………………………………………….23 3.6 Connector…………………………………………………….…………..………..…………24 3.7 Net……………………………………………………………………………………….…...29 3.8 Loads at the joints………………………………………………………………….………...30 CHAPTER 4: TENSION TESTING OF JOINTS ………………………………………….. 35 4.1 Tension Testing of Joints ………………………………………..……………….……….…36

4.1.1. Tension Testing of Dome 1…..……………………………………..…………… 37 4.1.2. Tension Testing of Dome 2……………………………………………………… 38

4.2 Compression Testing .……………………………………..….………………………….… 40 CHAPTER 5 CONCLUSION AND RECOMMENDATIONS….……….………………… 43 5.1 Conclusion….………………….…………………………………………………………… 44

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5.2 Recommendations….…………..…………………………………………………………… 45 5.3 Materials required making a geodesic dome……………………………………………...…45 REFERENCES….………………………………………………...…………………………… 47 APPENDIX….………………………………………………...……..………………………… 52

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LIST OF FIGURES Page

Fig. 1.1 Assam Bamboo……………….…………………………………..………………….… 14

Fig. 2.1 Bamboo Housing……………….……………………………………………………… 16

Fig. 2.2 Bamboo Truss……………….…………………………………………………….…… 16

Fig. 2.3 Bamboo Roof Skeleton……………….……………………………………………...… 17

Fig. 2.4 Scaffolding……………….………………………………………………………..…… 17

Fig. 3.1 6V Geodesic Dome……………….………………………………………….………… 19

Fig. 3.2 Platonic Solids……………….………………………………………………………… 20

Fig. 3.3 Uniform Triangle Subdivision……………….………………………………………… 20

Fig. 3.4 3V, 4V and 5V Domes……………….……………………………………………...… 21

Fig. 3.5 2V Dome and Sphere……………….………………………………………..………… 21

Fig. 3.6 Assembly diagram……………….………………………………………………..…… 22

Fig. 3.7 Joint in Dome 1..……….……………………………………………………………… 23

Fig. 3.8 Joint in Dome 2..……….……………………………………………………………… 23

Fig. 3.9 Bamboo Strut in Dome 2..………….………………………………….…………….… 24

Fig. 3.10 Connector…………………….………...………………………………...…………… 24

Fig. 3.11 Pentagon…………………………….…………………………………...…………… 24

Fig. 3.12 4-way connector for Dome 1………….……………………………………………… 25






Fig. 3.18 Assembly of Dome …………………………..…………………………………….… 27

Fig. 3.19 Dome 1………….……………………………….…………………………………… 28

Fig. 3.20 Dome 2 ………….…………………………………………...………….…………… 28

Fig. 3.21 Parts of assembly diagram ………….………………………...……………………… 29

Fig. 3.22 Assembly diagram ………….……………………………...………………………… 29

Fig. 3.23 Clamp ………….……………………………………………..……………………… 30

Fig. 3.24 Metal Plate ………….……………………………………..………………………… 30

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Fig. 3.25 Dome with load on a joint ………….………………………...……………………… 32

Fig. 3.26 Leveled ground after keeping the load at the joint …………………….………….… 33

Fig. 3.27 Geodesic Dome 1 with Net ………….……………..………………………………… 33

Fig. 3.28 Dome 1 & Dome 2…………………….……………...…………………………….… 34

Fig. 4.1 Tension Test…………………….……………………………………...……………… 36

Fig. 4.2 Test 1 …………………….……………………………………………….…………… 37

Fig. 4.3 Test 2…………………….……………………….…………………….……………… 37

Fig. 4.4 Test 3 ……………….………………………………………………...…………..…… 37

Fig. 4.5 Test 4…………………….………………………………….……….………………… 37

Fig. 4.6 Joints of Dome 1 and Dome 2..…………………………………..…………………… 38

Fig. 4.7 Tension Testing of Dome 2…………………………………….……………………… 39

Fig. 4.8 Compression Testing Machine ……………….………………………………..……… 40

Fig. 4.9 After Compression Test….……………………………………………………….…… 41

Fig. 4.10 Load vs. Displacement ……………..…………………….……….……….………… 42

Fig. 4.11 Stress vs. Strain..……………………………………….………..…………………… 42

Fig. 4.12 Tension Testing of Dome 2…………………………………...……………………… 28

Fig. 4.13 Compression Testing Machine ……………….…..…………………………..……… 29

Fig. 5.1 Deformed joints……………….……………………..………………………………… 44

Fig. 5.2 One node between joint and the edge ……………………….………………………… 44

Fig. 5.3 L-strip ……………….……………………..………..………………………………… 44

Fig. 5.4 I-Bolt ……………….………………………………..………………………………… 46

Fig. 5.5 Nut & Bolt ……………….…………………...……..………………………………… 46

Fig. 5.6 Washer and Nut………………………………………………………………...……… 46

Fig. 5.7 Connector ……………………..……………………..………………………………… 46

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LIST OF TABLES

Page

TABLE 1.1 Various uses of bamboo ……...…………………………………………………… 12

TABLE 1.2 Comparison of Bamboo and Other Materials……...……………………………… 14

TABLE 4.1 Tension testing of Dome 1……...…………………………………….…………… 38

TABLE 4.2 Tension testing of Dome 2……...…………………………….…………………… 40

TABLE 4.3 Compression testing ……...……………………………………..………………… 41

TABLE 5.1 Materials required for making geodesic dome ………………..……………….… 47

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CHAPTER 1 INTRODUCTION

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1.1 ABOUT BAMBOO Bamboo is one of nature’s most valuable gifts to mankind. It is one of the fastest-growing plants

on Earth. It is a versatile, strong, renewable and environment-friendly material. Bamboo has

remarkable properties as a construction material, being both light weight and extremely strength

and durable. Bamboo having considerable tensile and compressive strength as a construction

material is used widely. If it is mixed with some durable material like mortar and concrete than

its durability as well as the strength taking ability will be much higher [Mahzuz et al., 2011]. It

is seen that everyday about 2.5 billion people in Asia use bamboo for their everyday work

[Scurlock et al., 2000]. There are several differences between bamboo and wood. In bamboo,

there are no rays or knots, which give bamboo a far more evenly distributed stresses throughout

its length. Bamboo is a hollow tube, sometimes with thin walls, and consequently it is more

difficult to join bamboo than pieces of wood. Bamboo does not contain the same chemical

extractives as wood, and can therefore be glued very well [Jassen 1995]. Bamboo is relished as

food in its shoots and its culms are converted into products such as household utensils, bridges,

baskets, joss-papers, joss-sticks, tooth-picks, skewers, poultry cages and handicrafts [Azmy,

1989; Wong, 1989]. To ensure adequate supply of bamboo resources in the future and to

maintain a well-balanced forest environment, systematic management principles should be made

available. With the application of systematic management principles on the natural stand

bamboos, the production of bamboo stock can be increased [Fateh Mohammad, 1931; Numata,

1979; Liese, 1985]. Construction industry is one of the most polluting industries in the world.

Production of both concrete and steel causes considerable deterioration of the environment. For

example cement requires over 1400°C by burning fossil fuel [CS Monitor, 2008; Aziz, 1995].

Most bamboo species produce mature fiber in 3 years, sooner than any tree species. Some

bamboos grow up to 1 meter a day, with many reaching culms lengths of 25 meters or more.

Bamboo can be grown quickly and easily, and sustainably harvested in 3 to 5 years cycles. It

grows on marginal and degraded land, elevated ground, along field bunds and river banks. Some

bamboo even sequester up to 12 tons of carbon dioxide from the air per hectare. Bamboo can

also lower light intensity and protects against ultraviolet rays. It adapts to most climatic

conditions and soil types, acting as a soil stabilizer, an effective carbon sink and helping to

counter the greenhouse effect [Bamboo for integrated Rural Development, 2008]. Table 1-1

provides a detailed description of diversified bamboo utilization.

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Table 1-1 Various uses of bamboo [Gielis, 2002]

Typically, species like dendrocallamus giganteus (DG) have tensile strength of about 120

MPa, compressive strength of 55 MPa and Young’s modulus of 14 GPa. Mild steel has an

ultimate strength of 410 MPa, yield strength of 250 MPa and Young’s modulus of 20 GPa.

Concrete has much lower strength than those of bamboo reported here. In addition, the low

density of bamboo, which is typically 700 kg/m3, results in much higher strength to weight ratio

as compared to steel (density = 7800 kg/m3) and concrete (density= 2400 kg/m3). Bamboo

offers competitive strength to mass ratio. It is free from corrosion and is very light. Besides,

bamboo costs just six per cent of the price of steel. The only shortcoming with raw bamboo is

susceptibility to termite attack which can be set aside by suitable chemical treatment [Bhalla et

al., 2008].

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1.2 BAMBOO IN INDIA India is blessed with very rich bamboo resources. With about 22 genera and 136 species, it is one

of the largest, next only to China with its 26 genera and 300 species. The areas particularly rich

in bamboo are the North Eastern States, the Western Ghats, Chattisgarh, M.P. and Andaman &

Nicobar Islands. The important genera are Arundinaria, Bambusa, Dendrocalamus, Dinochloa,

Gigantochloa, Melocanna, Oxytenanhthera and Pseudostachyum etc. Of the nearly 136 species,

at present only about few are being commercially exploited today [Bamboo for integrated

Rural Development, 2008].

1.3 PROPERTIES OF BAMBOO

1.3.1 SHRINKAGE AND SWELLING Bamboo, like wood, changes its dimension when it loses or gains moisture. Bamboo is a

hygroscopic material, thus the moisture content changes with the changes in the relative

humidity and temperature of the surrounding environment [Razak et al., 1995]. Dimensional

stability is very crucial in structural products because the safety and comfort in a structure

usually depends on them. Free water and bound water exists in bamboo, however the amount of

free water is small as compared to bound water. This explains why the bamboo starts to shrink as

soon as it loses moisture [Tewari, 1992].

1.3.2 TENSION PARALLEL TO GRAIN Tension tests parallel to the grain are seldom investigated for bamboo. Tensile strength values of

Bamboo cannot be utilized as such in practical work, as bamboo will fail by shear long before its

full tensile stress is developed. The tension strength value is a fundamental criterion in order to

design bamboo tension members [Limaye, 1952].

1.3.3 BENDING The bending is an important parameter, deciding the suitability of Bamboo as a construction

material. Because of this ability Bamboo can be used as a substitute for reinforcement in

construction of buildings [Hearn, 1997].

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1.3.4 ELASTICITY The enormous elasticity of bamboo makes it to a very good building material for earthquake

endangered areas. Another advantage of bamboo is its low weight. It can be transported and

worked easily, thus rendering use of cranes and other big machines unnecessary [Bamboo as a

building material, 2002].

1.3.5 FIRE RESISTANCE The fire resistance of bamboo is very good because of its high content of silicate acid. Filled up

with water, it can stand a temperature of 400° C while the water cooks inside [Acton, Q. A.,

2011].

1.4 COMPARISON The comparison between bamboo and various materials in terms of various parameters is as

appended below in the form of a chart.

TABLE 1.2 Comparisons of Bamboo and Other Materials [Janssen, J.A., 2000]

1.5 BAMBOO USED The Bamboo used for constructing the geodesic dome is “Assam Bamboo” as seen in Fig. 1.1

Fig. 1.1 Assam Bamboo

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CHAPTER 2

BAMBOO APPLICATIONS

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2.1 HOUSING/CONSTRUCTION The construction materials for building a bamboo house should be readily available and

accessible. Traditionally used construction materials are considered. The bamboo based house

has a very low weight therefore foundations can be minimized. Fig. 2.1 (a) displays a typical

bamboo house. The structure in Fig. 2.1 (b) is built in a tropical area with no end walls and using

untreated bamboo.

Fig. 2.1 (a) Fig. 2.1 (b)

Bamboo Housing [Bamboo Building and Culture, 2000]

2.2 BAMBOO TRUSSES Traditionally timber trusses or rafter-purlins have been in vogue for sloping roofs from time

immemorial. Bamboo trusses offer a good substitute for supporting roof loads and transmitting

them to the foundation through columns. Bamboo trusses are fabricated using culms having an

outer diameter of 75-100 mm. When the top and bottom chords and strut members are properly

jointed by suitable fastening devices, a truss can resist compressive and tensile forces.

Fig. 2.2 Bamboo Truss [Shyamsundar et al., 2007]

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2.3 BAMBOO ROOF SKELETON It consists of bamboo trusses or rafters over which solid bamboo purlins are laid and lashed to

the rafter or top chord of the truss by means of G.I wire, cane, grass, sutli or bamboo leaves.

Nails are not used however for fear of splits in the bamboo. A mesh or grid made of halved

bamboo is laid and lashed to the purlins and roof covered.

Fig. 2.3 Bamboo Roof Skeleton [Shyamsundar et al., 2007]

2.4 SCAFFOLDINGS Because of the favorable relationship between load-bearing capacity and weight, bamboo can be

used for the construction of safe scaffoldings even for very tall buildings. The cane extension is

carried out by lashing the cane ends together with several ties. The ties are arranged so that force

acting vertically downwards wedges the nodes in the lashing. With larger cane diameters the

friction can be increased by tightening the rope between the canes. This technique has great

advantage that the joints can be re-tensioned to the right degree without difficulty and also

quickly released again.

Fig.2.4 Scaffolding [Bamboo as a building material, 2002]

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CHAPTER 3

CONSTRUCTION OF

GEODESIC DOME

19

3.1 GEODESIC DOME A geodesic dome is a spherical or partial-spherical shell structure or lattice shell based on a

network of great circles (geodesics) lying on the surface of a sphere. The geodesics intersect to

form triangular elements that have local triangular rigidity and also distribute the stress across

the entire structure. When completed to form a complete sphere, it is known as a geodesic sphere

[Geodesic Dome, Wikipedia]. Geodesic designs can be used to form any curved, enclosed

space. Oddly-shaped designs would require calculating for and custom building of each

individual element—resulting in potentially expensive construction. Because of the expense and

complexity of design for fabrication of any geodesic dome, builders have standardized a few

basic designs [Geodesic Dome, Soulvisuals].

Fig. 3.1 6V Geodesic Dome

Figure 3.1 illustrates a fairly complex version of a dome which is composed of small triangles

that are approximately equal, and such that the vertices of the triangles all lay on the surface of a

hemisphere.

3.2 ENGINEERING CONSIDERATION A sphere is the mathematical object that contains the maximum volume compared to its surface

area, so if a structure of large volume is to be constructed for minimum cost; it makes sense to

look at structures whose shape approaches a sphere. But most construction materials come as flat

or straight pieces, so forming the curves that would be necessary to make a perfect sphere might

increase the expense considerably.

If the structure is composed of struts, there is another consideration; namely, that it

should be composed completely of triangles. If it consists of any quadrilaterals or more complex

20

polygons, they can flex if the connections at the ends are not completely rigid. If the pieces, for

example, are just connected with a bolt through a number of struts, it is almost impossible to

make the joints rigid. But if the structure is completely composed of triangles, it can be made

completely rigid, even if the individual joints are not.

One final engineering consideration is that if the triangles of which the structure is

composed are all as close to equilateral triangles as possible, then the stresses will be

approximately the same on all the struts, so there is very little wasted strength. Finally, in very

large structures, it is a bad idea to have very long unsupported struts. [Davis, T., 2011]

3.3 PERFECT AND IMPERFECT SOLUTIONS A perfect solution will be composed of triangles that are all equilateral, all the same size, and all

making equal angles with each other. Unfortunately, this can only be achieved with three

mathematical forms: the tetrahedron, the octahedron and the icosahedron.

Fig. 3.2 Platonic Solids

These so-called platonic solids are approximations to the sphere, but only the icosahedron

is very close, and to make a large structure from it would require very long struts.

Fig. 3.3 Uniform Triangle Subdivision

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One way to proceed is simply to subdivide the triangles in one of the regular platonic

solids, and this is how a geodesic dome is constructed. Any of the three solids could be used, but

there are some serious problems if this is done beginning with a tetrahedron, and less-serious

problems (but problems, nonetheless) if begun with an octahedron.

The standard construction of domes of various complexities is begun with icosahedron. It

is easy to subdivide an equilateral triangle into 4, 9, 16, or any perfect square number of sub-

triangles, as is illustrated in Fig. 3.3. But if the triangles of icosahedron are subdivided, although

the vertices of the original icosahedron will lie on the surface of a sphere, the vertices that are

needed to add to subdivide the triangles will lie in the planes of those triangles and will be

physically inside the sphere.

Fig. 3.4 3V, 4V and 5V Domes

The names, “3V”, “4V” and “5V” refer to the number of subdivisions that are made to

the original triangles in the icosahedron before they are pushed out to the surface of the sphere.

The 3V and the 5V domes are slightly larger than a half sphere because when there are an odd

number of triangles in the subdivision, there is no center line or “equator” at which to divide it,

so the version that is a little larger or a little smaller than a half sphere is picked.

Fig. 3.5 The 2V Dome and Sphere

All the domes displayed in Fig. 3.4 are fairly complicated to build; the easiest that can

reasonably be called a geodesic dome is the 2V version. Fig. 3.5 displays the 2V dome (a half-

sphere) and the corresponding 2V sphere [Davis, T., 2011].

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3.4 STRUT LENGTHS In 2V dome, each of the equivalent equilateral triangles from the icosahedron is subdivided into

4 triangles (see Fig. 3.6 (a)) and then the inner three vertices are pushed out to the surface of the

inscribing sphere. Each of the original sides of each triangle will become two equal pieces on the

surface of the 2V dome, and three additional pieces are added to form the inner triangle. The

three struts that make up the inner triangle are of equal length, as are the six struts that were

made by subdivision and pushing out of the original edges of the icosahedron. The two lengths

are different, but that all of the struts in the final dome or sphere are one of those two lengths. In

Fig. 3.6 (b), the blue colored struts ‘A’ and the red colored struts ‘B’ have been displayed.

For a 2V dome, there are only two different strut lengths required, 30 of the shorter length ‘B’

and 35 of the longer length ‘A’. The length of both types of struts can be calculated using “Dome

Calculator”.

Diameter of Dome = 6 m => Radius of Dome = 3 m

Strut Factor for strut ‘A’ = 0.618 [Davis, T., 2011]

Strut Factor for strut ‘B’ = 0.546 [Davis, T., 2011]

Length of strut ‘A’ = Radius of Dome * Strut FactorA = 3 * 0.618 = 1.85 m [Davis, T., 2011]

Length of strut ‘B’ = Radius of Dome * Strut FactorB = 3 * 0.546 = 1.64 m [Davis, T., 2011]

Fig. 3.6 (a) Fig. 3.6 (b)

Assembly diagram

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3.5 JOINT The materials required in making a joint are as follows:-

1. Bolt

2. 3 Nuts

3. I-Bolt

4. 3 Circular Strip

5. 2 L-strip

Fig. 3.7 describes the fabrication of joint in Dome 1. It consists of I-Bolt of diameter 5 mm, L-

strip of thickness 1 mm, 1 washer and 2 nuts.

Fig. 3.7 Joint in Dome 1

Fig. 3.8 describes the fabrication of joint in Dome 2. In this joint, the diameter of I-Bolt is

increased to 7 mm. The diameter of bolt is also increased to 7.5 mm. The thickness of strip is

also increased to 2 mm. The position of I-Bolt with respect to the L-strips is also changed so that

when these joints are connected with the connector, deflections would be less which will

increase the stability of dome.

Fig. 3.8 Joint in Dome 2

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Fig. 3.9 shows the Bamboo strut ‘A’ of length of 1.85 m (185 cm) with both the joints at the end.

One strut has 2 joints.

Fig. 3.9 Bamboo Strut in Dome 2

So, Total no. of bamboo struts = No. of bamboo strut ‘A’ + No. of bamboo strut ‘B’

= 35 + 30 = 65

Also, Total no. of joints = 65 * 2 = 130

3.6 CONNECTOR Fig. 3.10 shows the connector which is used to connect the bamboo struts to fabricate the dome.

Fig. 3.10 Connector

The struts are first arranged to form a pentagon as shown in Fig. 3.11. Similarly, 5 more

pentagons are made.

Fig. 3.11 Pentagon

25

The 5 pentagon structures are placed near each other in a circle and sixth pentagon is placed

above these pentagons connecting each vertex of the sixth pentagon with top vertex of the

bottom 5 pentagons. Finally, the bases of these pentagons are connected with a strut.

Thus, there are 3 types of connectors in the dome:-

1. 4-way connector – It connects the bases of the pentagon as shown in the Fig. 3.12 & Fig.

3.13. There are 5 bases to be connected, so the total no. of 4-way connector is 10.

Fig. 3.12 4-way connector for Dome 1 Fig. 3.13 4-way connector for Dome 2

2. 5-way connector – It is at the centre of each pentagon as shown in the Fig. 3.14 & Fig.

3.15. There are 6 pentagons, so the total no. of 5-way connector is 6.


3. 6-way connector – 5 connectors connects the base pentagons with each other and 5 more

connectors connect the base pentagons with the pentagon at the top as shown in the Fig.

3.16 & Fig. 3.17. So, the total no. of 6-way connector is 10.

26


Thus, the total no. of connectors is 26 (10 + 6 +10). The difference between the connections of

Dome 1 and Dome 2 can be easily seen in the above figures. The connection in Dome 2 is very

strong which increases its stability and helps to withstand against the force of the wind.

Fig. 3.18 shows the stepwise process to fabricate the dome. Fig. 3.19 and Fig. 3.20 show the

complete view of Dome 1 and Dome 2 respectively.

27

Fig. 3.18 Assembly of Dome

28

Fig. 3.19 Dome 1

Fig. 3.20 Dome 2

29

3.7 NET A Net with a porosity of 10% is used to cover the dome. To fix the net to the dome, clamps and

staple pins are used. Staple pins are pierced into the bamboo using staple guns. In the dome,

there are 2 types of triangles with different area as shown in Fig. 3.21. There are 10 Type 1

triangles and 30 Type 2 triangles in the dome as shown in Fig. 3.22.

Fig. 3.21 Parts of assembly diagram

Fig. 3.22 Assembly diagram

The calculation of area of net is as follows:-

Area of Type 1 = √3 / 4 * (A)2 = √3/4 * (1.85)2 = 1.48 m2 (1)

Area of Type 2 = A / 4 * √(4*B2 – A2)= 1.85 / 4 * √(4*1.642 – 1.852) = 1.25 m2 (2)

Area of net required = Surface Area of Dome = Area of all triangles

= 10 * Area of Type 1 + 30 * Area of Type 2

From (1) and (2)

= 10 * 1.48 + 30 * 1.25

= 52.3 m2 ~ 55 m2

30

To fix the net with the bamboo, 2 clamps have been clamped on each bamboo strut as shown in

Fig. 3.23. Therefore,

Total no. of clamps = 2 * 65 = 130

Fig. 3.23 Clamp

Also, 4 staple pins are punched on each bamboo strut. Therefore,

Total no. of staple pins = 4 * 65 = 260

3.8 LOADS AT THE JOINTS To uphold the dome and make it stable, a load using a hard metal strip is put on each joint of the

dome. The metal strip has a thickness of 5 mm and width of 3 cm as shown in Fig. 3.24.

Fig. 3.24 Metal Plate

As the no. of joints at the base of the dome is 10, so 10 metal strips are required to be connected.

Each metal strip is connected to the joint at the base of the dome using the same 4-way

connector.

31

Using IS 875 (part III), the load will be equivalent to the wind load acting in the direction normal

to the individual structural element –

F = ( Cpe – Cpi ) A pd (3)

Cpe = external pressure coefficient = 1.2

Cpi = internal pressure coefficient = 0.6

A = surface area of structural element or cladding unit, and

pd = design wind pressure.

A = 2 * π * r2 = 2 * 3.14 * 32 = 56.52 m2 (4)

pd = 0.6 Vz2 (5)

Where Vz = design wind velocity in m/s at height z.

Vz = k1 * k2 * k3 * Vb

Where k1 = probability factor (risk coefficient)

k2 = terrain, height and structure size factor

k3 = topography factor

Vz = 1.05 * 1 * 1 * 47 = 49.5 m/s (6)

Substitute (6) in (5)

Therefore, pd = 0.6 * 49.52 = 1470.15 N/m2 (7)

Safety Factor = 1.2

Substitute (4) and (7) in (3)

F = 1.2 * 1/3 * (1.2 – 0.6) * 52.15 * 1470.15 = 15333.66 N

As there are 10 joints, so load at one joint = F/10 = 1533.36 N

So, mass on one metal plate = 1533.36 / 9.8 = 156.46 kg

32

So, a pit of length 1 m, breadth 0.5 m and height 0.5 m is dug. Then the load of 165 kg is put

using 3 sandbags, each weighing 55 kg as shown in Fig. 3.25. Similarly the same load is put on

the rest of the joints.

Fig. 3.25 Dome with load on a joint

Fig 3.26 shows the leveled ground after keeping the load at the joint and Fig. 3.27 shows the

complete dome with net and the load at the joints.

33

Fig. 3.26 Leveled ground after keeping the load at the joint

Fig. 3.27 Geodesic Dome 1 with Net

Metal joint

34

Fig. 3.28. Dome 1 & Dome 2

35

CHAPTER 4

TESTING OF JOINTS

36

4.1 TENSION TESTING OF JOINTS

Fig. 4.1 Tension Test

37

4.1.1 TENSION TESTING OF DOME 1 The tension testing of Dome 1 consists of 4 samples. Sample 1 has 1 mm thick L-strip and at a

shear stress of 39.24 MPa, strip failed as shown in Fig. 4.2. So, in the sample 2 & sample 3, the

thickness of L-strips is increased to 2 mm. These samples achieved a peak stress of 58.13 MPa

and 58.86 MPa respectively and resulted in the failure of bamboo as shown in Fig. 4.2 and Fig.

4.3. In Sample 4, the position of node is kept between the joint and the edge which resulted in the

maximum shear stress of 108.25 MPa and joint failed as shown in Fig. 4.4. The summary of the

test is provided in the Table 4.1

Fig. 4.2 Test 1

Fig. 4.3 Test 2

Fig. 4.4 Test 3

Fig. 4.5 Test 4

38

Thickness of metal strip (mm)

Outer Diameter (mm)

Inner Diameter (mm)

Thickness (mm)

Diameter of Bolt (mm)

Area (mm2) Load Stress

(MPa) Result

1 1 26.5 12.5 7 5 35 2747 39.24 Failure due to strip

2 2 26 12.5 6.5 5 33.75 3924 58.13 Failure of

Bamboo due to thick strip

3 2 26.5 10.5 8 5 40 4709 58.86 Failure of

bamboo due to thick strip

4 2 27.5 13 7.25 5 36.25 7848 108.25

Failure of joint due to location of

node between the joint and the

edge Table 4.1 Tension testing of Dome 1

4.1.2 Tension testing of Dome 2

Fig. 4.6 Joints of Dome 1 and Dome 2

After the test of Dome 1, the joint is modified with the increased diameter of bolt & I-bolt and

thickness of L-strip. For the testing purposes, to avoid the strip failure or joint failure, the joint

should be welded so that the final result will be due to the failure of bamboo.

The tension testing consists of 3 parts:-

a) 3 specimens without the node in between the joint and the edge.

b) 3 specimens with only one node in between the joint and the edge.

c) 3 specimens with both the nodes in between the joint and the edge.

39

The maximum shear stress observed when the node is not between the joint and the edge is 49.4

MPa. The bamboo can be failed on either side as shown in Fig. 4.7.

When one node is between the joint and the edge, the maximum shear stress observed is 80.8

MPa. In this type of sample, the bamboo is failed at the edge where joint is without node as

shown in Fig. 4.7.

When 2 nodes are between the joint and the edge, the maximum shear stress is increased to

108.40 MPa. The bamboo can be failed on either side as shown in Fig. 4.7.

The summary of the testing can be seen in Table 4.2.

Fig. 4.7 Tension Testing of Dome 2

40

S. No.

Node between joint and edge

Outer Diameter (mm)

Inner Diameter (mm)

Thickness (mm)

Diameter of Bolt (mm)

Area (mm2)

Load (N)

Stress (MPa) Result

1 Without Node 42.4 16.9 12.8 7.5 95.6 4116.0 21.5 Bamboo

Failed


Failed


Failed

4 With one node 40.4 24.4 8.0 7.5 60.0 8428.0 70.2 Bamboo

Failed


Failed


Failed

7 With two nodes 37.5 28.5 4.5 7.5 33.8 6664.0 98.7 Bamboo

Failed


Failed


Failed

Table 4.2 Tension testing of Dome 2

4.1.3 Compression Testing

Fig. 4.8 Compression Testing Machine

41

In the compression testing we have taken 4 samples. The rate of loading is constant at 0.1

mm/sec. The loading rate for concrete is 1.4 mm/sec. As there is no prescribed loading rate, so

we conducted the experiment at 0.1 mm/sec.

Sample 1 & Sample 3 are of same bamboo strut and sample 2 & sample 4 are of different

bamboo strut. Sample 1 & Sample 2 do not have node and Sample 3 & Sample 4 have node. In

sample 1, the peak load is 59.8 kN. In sample 3, the peak load in 71 kN which is due to the

presence of the node. Similarly, in sample 2, the peak load in 75.4 kN and in sample 4, the peak

load is increased to 80 kN. The samples after the test are shown in Fig. 4.9.

Avg. Diameter = sqrt (3.14 * (Do2 – Di

2))

Where Do = Outer Diameter

Di = Inner Diameter

Sample No.

Outer Diameter (mm)

Inner Diameter (mm)

Avg. Diameter (mm)

Height (cm)

Peak Load (kN)

Without Node Sample 1 39 18 34.60 9.2 59.8 Without Node Sample 2 41 14 38.54 9.2 75.4 With Node Sample 3 39 18 34.60 10.2 71 With Node Sample 4 41 14 38.54 9.8 80

Table 4.3 Compression testing

Fig. 4.9 After Compression test

42

From the tests, the graphs of Load vs. Displacement (Fig. 4.10), Stress vs. Strain (Fig. 4.11),

Displacement vs. Time (Fig. 4.12) and Load vs. Time (Fig. 4.13) are drawn.

Fig. 4.10 Load vs. Displacement

Fig. 4.11 Stress vs. Strain

43

CHAPTER 5

CONCLUSION AND

RECOMMENDATIONS

44

5.1 CONCLUSION Geodesic Dome 1 has been constructed with net covering and metal plate has been attached to

the joints for the stability of the dome.

While testing the joints of Dome 1, when the thin strip with thickness 1mm was used, the joint

failed and the shear stress came out to be 19.62 MPa. Then the thickness of strip is increased to

2mm which resulted in the failure of bamboo with a bearing stress of 29.07 MPa & 29.43 MPa

for two joints. Also, when the node is between the joint and the edge in which, the joint failed

proved that node of the bamboo can take up large amount of loads as the bearing stress went up

to 54.12 MPa.

However some joints have been deformed either due to wind or dead load.

Fig. 5.1 Deformed joints

In the construction of Dome 2, the size of I bolt and bolt is increased from 5 mm to 7 mm and the

thickness of the strip is also increased from 1 mm to 2 mm which increase the strength of the

joint. The position of I-Bolt is set in the joint to restrict the movement of the joint which

ultimately reduced the deforming tendency of the structure.

The maximum shear stress observed when the node is not between the joint and the edge is 49.36

MPa. When one node is between the joint and the edge, the maximum shear stress observed is

80.78 MPa. When 2 nodes are between the joint and the edge, the maximum shear stress is

increased to 108.40 MPa.

The compressive strength of the bamboo with a node is greater than the bamboo sample without

node.

45

Thus, the thickness of bamboo and the position of node play an important role in the construction

of dome. In some of the bamboo struts, it is tried to put node between the joint and edge as it

would result in greater shear stress.

5.2 RECOMMENDATIONS 1. As it is not possible to find a bamboo strut with a particular length having both the nodes

between the joint and the edge, therefore only one node should be between the joint and the

edge. .

Fig. 5.2 One node between joint and the edge

2. While testing, I-Bolt should be welded with the rest of the pieces to avoid failure of joint.

3. Instead of 2 L-strips, we can use 1 U-strip.

4. The strip should have a minimum thickness of 2mm else the joint would fail.

5. The bamboo should not be too hollow which may lead to failure of bamboo in short time.

5.3 Materials required making a geodesic dome. 1. Bamboo Strut

a. Length of Strut A = 1.85m. (# 35),Outer Diameter = 4 cm, Thickness = 1.5 cm

b. Length of Strut B = 1.64 m (# 30), Outer Diameter = 4 cm, Thickness = 1.5 cm

2. L strips – 2 mm thickness (# 260),

Fig. 5.3 L-strip.

46

3. I-bolt – 7 mm diameter (#130)

Fig. 5.4 I-Bolt

4. Bolt – 7 mm diameter (#130)

5. Nut – 7 mm diameter (#130)

Fig. 5.5 Nut & Bolt

6. Washer – 7 mm diameter (#390)

Fig. 5.6 Washer and Nut

7. Connector - Diameter of 1.5 cm (#24)

Fig. 5.7 Connector

47

S. No. Material Length Diameter Thickness Number of pieces

1 Bamboo Strut

Strut A 1.85 m 4 cm (outer) 1.5 cm 35 Strut B 1.64 m 4 cm (outer) 1.5 cm 30

2 L strips 10 cm 4 cm (width) 2 mm 260 3 I‐bolt 8 cm 7 mm ‐ 130 4 Bolt 7 cm 7.5 mm ‐ 130 5 Nut ‐ 7.5 mm ‐ 130 6 Washer ‐ 7 mm (inner) ‐ 390 7 Connector 6 cm 1.5 cm ‐ 24

Table 5.1 Materials required for making geodesic dome

48

REFERENCES

49

1. Aziz, M.A. (1995),”Engineering Materials”, Z and Z Computer and Printers, Dhaka,

Bangladesh, p. 65.

2. Azmy, H.M. (1989), “Venture on the Making of Fish or Vegetable and Charcaoal Baskets”,

Forest Research Institute, Kepong, p. 8.

3. Bamboo as a building material (2002), http://bambus.rwth-aachen.de/eng/PDF-

Files/Bamboo%20as%20a%20building%20material.pdf, University of Aachen, Germany

4. BAMBOO FOR INTEGRATED RURAL DEVELOPMENT (2008),

http://www.keralaagriculture.gov.in/htmle/bankableagriprojects/fw/Bamboo.htm

5. Bhalla, S., Gupta, S., Puttaguna, S. and Suresh, R. (2008), “Bamboo as Green Alternative to

Concrete and Steel for Modern Structures”, Journal of Environmental Research and

Development, Vol. 3, No. 2, pp. 362-370.

6. Building materials (2005), http://www.staff.city.ac.uk/earthquakes/Bamboo/Bamboo.htm#

Fifth.

7. Davis, T. 2011, "Geodesic Dome", http://www.geometer.org/mathcircles/geodesic.pdf

8. DeBoer, D., Bareis, K., “Bamboo building and culture- the architecture of Simon Velez”,

architect, Bogota, Colombia.

9. Fateh, M. (1931), “The bamboo forest of Hoshiarpur District Punjab”, Indian Forester, No.

26, pp. 491-510.

10. Geodesic Dome, Soulvisuals, http://soulvisuals.com/glossary/geodesic-domes.html

11. Geodesic Dome, Wikipedia, http://en.wikipedia.org/wiki/Geodesic_dome

50

12. Gielis, J., (2002), “Future possibilities for bamboo in European agriculture - Oprins Plant

Sint-Lenaartsesteenweg”, 91 B-2310 Rijkevorsel.

.

13. Ghavami, K. (2005), “Cement and Concrete Composites”, Volume 27, Issue 6, Pages 637-

649.

14. Hearn, E.J. (1997), “Mechanics of materials - An introduction to the mechanics of elastic and

plastic deformation of solids and structural materials” (third edition). University of Warwick,

U.K. Butterworth, Heinemann.

15. IS 456

16. IS 875 (Part 3)

17. Janssen, J.A. Eindhoven University, The Netherlands

18. Janssen, J.A. (1995), “Building with bamboo (second edition)”, Intermediate Technology

Publication Limited, London. pp. 65.

19. Liese, W. (1985), “Biology – Biology, Silvics” Properties, Utilization, Eschborn

20. Liese, W., (1987), “Research on bamboo, Wood Sci. Technol.,” 21(3):189-209, ISSN: 0043-

7719 (Print) 1432-5225 (Online), DOI 10.1007/BF00351391.

21. Limaye, V.D. (1952), “Strength of bamboo (Dendrocalamus strictus)”, Indian Forest

Records. 1(1):1-17.

22. Mahzuz, H. M. A., Ahmed, M., Ashrafuzzaman M., Karim, R. and Ahmed, R. (2011),

"Performance evaluation of bamboo with mortar and concrete", Journal of Engineering and

Technology Research, Vol. 3, No 12 (Nov), pp. 342 – 350.

51

23. Monitor CS (2008). http://www.csmonitor.com/2008/0312/p14s01-stgn.html.

24. National Status Report on Forests and Forestry in India, (Survey and Utilization Division)

Ministry of Environments & Forests, Government of India, New Delhi, September 2006

25. Numata, M. (1979), “The structure and succession of bamboo vegetation”, in Numata, M.

(Ed.), Ecology of Grasslands and Bamboo Lands in the World, Kluwer, The Hague, pp. 222-

36.

26. Razak, A., Latif, M., Liese, W. and Norini., H. (1995), “Planting and utilization of bamboo

in Peninsular Malaysia”, Research Pamphlet, Forest Research Institute Malaysia.

27. Rawat, J.K., Khanduri, D.C., “THE STATUS OF BAMBOO AND RATTAN IN INDIA”

28. Scurlock, J.M.O, Dayton, D.C. and Hame, B. (2000). “Bamboo: an overlooked biomass

resource? Biomass and Bio-energy”, 19(4): 229-244.

29. Shyamasundar, K., Vengala, J. (2007), “Promotion of bamboo Housing system & Recent

Developments”, IPIRTI, INDIA

30. Tan, T., Rahbar, N., Allameh, S.M., Kwofie, S., Dissmore, D., Ghavami, K. and Soboyejo,

W.O. (2011), “Advances in Silicic Acid Research and Application”, Acton, Q. A., 2011

31. Tewari, D.N. (1992), “A monograph on bamboo. International Book Distribution”,

DehraDun (India).

32. Tommy, Y., Lo, H.Z., Cui, P.W.C., Tang, H.C. and Leung, H. (2008), “Construction and

Building Materials, Volume 22, Issue 7, Pages 1532-1535

33. Wong, K.M. (1989), “Current and potential uses of bamboo in Peninsular Malaysia”, Journal

of American Bamboo Society, Vol. 7 No. 172, pp. 1-15.

52

34. Xiao, Y., Inoue, M. and Paudel, S.K., “Modern Bamboo Structures”

35. Xuhe, C., Zheng, W., Lobovikov, M., Liang, C., and Li, G., "Preliminary study on the

manufacture of bamboo panel components for prefabricated house"

36. Zu, L., Koussios, S. and Beukers, A. (2010), “Composites Part A: Applied Science and

Manufacturing”, Volume 41, Issue 9, Pages 1312-1320.

53

APPENDIX

55

Compression Test ‐ Sample 1

Data Point

Time (Sec)

Load (kN)

Displacement (mm)

1 0 4.6 0.077

2 1 7.9 0.166 3 2 11.7 0.281 4 3 15.7 0.397 5 4 19.8 0.507 6 5 23.3 0.621 7 6 26.7 0.728 8 7 30 0.842 9 8 32.8 0.945 10 9 34.2 0.997 11 10 36.6 1.087 12 11 39.3 1.179 13 12 42.2 1.27 14 13 45.4 1.363 15 14 48.2 1.456 16 15 51 1.546 17 16 53.7 1.642 18 17 56.5 1.734 19 18 58.7 1.828 20 19 59.8 1.921 21 20 59.6 2.01 22 21 58.8 2.101 23 22 57.8 2.188 24 23 56.7 2.279 25 24 55.1 2.374 26 25 52.9 2.468 27 26 50.8 2.562 28 27 49.6 2.66 29 28 49.2 2.758 30 29 49 2.858

56

Compression Test ‐ Sample 2

Data Point

Time (Sec)

Load (kN)

Displacement (mm)

Data Point

Time (Sec)

Load (kN)

Displacement (mm)

1 0.07 0 4.1 37 1.79 36 58.9 2 0.13 1 5.7 38 1.83 37 60.2 3 0.19 2 7.6 39 1.88 38 61.2 4 0.25 3 9.3 40 1.92 39 62.6 5 0.3 4 11.3 41 1.96 40 63.5 6 0.35 5 13 42 2.01 41 64.5 7 0.4 6 15.2 43 2.06 42 65.9 8 0.44 7 17.1 44 2.1 43 66.9 9 0.49 8 19 45 2.15 44 68.2 10 0.53 9 21.1 46 2.2 45 68.9 11 0.58 10 23 47 2.25 46 69.8 12 0.63 11 25 48 2.29 47 70.6 13 0.67 12 26.8 49 2.34 48 71.3 14 0.72 13 28.8 50 2.38 49 71.9 15 0.77 14 30.4 51 2.43 50 72.5 16 0.82 15 32.1 52 2.47 51 73 17 0.87 16 33.4 53 2.52 52 73.8 18 0.91 17 34.7 54 2.57 53 74 19 0.96 18 35.9 55 2.61 54 74.4 20 1.01 19 37.1 56 2.66 55 74.6 21 1.05 20 38.3 57 2.71 56 74.9 22 1.1 21 39.5 58 2.76 57 75 23 1.15 22 40.9 59 2.81 58 75.2 24 1.19 23 42.1 60 2.85 59 75.4 25 1.24 24 43.4 61 2.9 60 75.4 26 1.29 25 44.7 62 2.94 61 75.3 27 1.33 26 46.1 63 2.99 62 75.3 28 1.38 27 47.5 64 3.04 63 75.2 29 1.42 28 48.8 65 3.09 64 75.1 30 1.47 29 50.1 66 3.13 65 74.7 31 1.52 30 51.6 67 3.18 66 74.7 32 1.56 31 53.1 68 3.23 67 74.4 33 1.61 32 54.4 69 3.25 68 74.3 34 1.66 33 55.8 70 3.3 69 74 35 1.71 34 57.2 71 3.35 70 73.6 36 1.74 35 57.7 72 3.4 71 73.1

57

Compression Test ‐ Sample 3 Compression Test ‐ Sample 4

Data Point

Time (Sec)

Load (kN)

Displacement (mm)

Data Point

Time (Sec)

Load (kN)

Displacement (mm)

1 0 4.4 0.146 1 0 3.7 0.094 2 1 5.7 0.239 2 1 5.5 0.189 3 2 7.3 0.334 3 2 7.9 0.288 4 3 9.2 0.42 4 3 10.8 0.396 5 4 11.5 0.508 5 4 14.8 0.512 6 5 14.1 0.589 6 5 19.1 0.621 7 6 17.1 0.672 7 6 23.9 0.723 8 7 20.7 0.76 8 7 28.8 0.827 9 8 24.3 0.847 9 8 33.9 0.93 10 9 28.1 0.94 10 9 39.2 1.029 11 10 31.8 1.027 11 10 44.7 1.133 12 11 35.7 1.116 12 11 50.5 1.227 13 12 40 1.204 13 12 56.3 1.328 14 13 44.7 1.294 14 13 62 1.427 15 14 49.8 1.379 15 14 67.4 1.533 16 15 55.1 1.463 16 15 72 1.645 17 16 60.1 1.545 17 16 75.3 1.758 18 17 65.2 1.633 18 17 77.3 1.877 19 18 69.1 1.726 19 18 78.1 1.985 20 19 71 1.812 20 19 78.6 2.088 21 20 70.9 1.851 21 20 79 2.187 22 21 69.8 1.946 22 21 79.4 2.281 23 22 68 2.057 23 22 79.6 2.365 24 23 66.2 2.177 24 23 79.8 2.452 25 24 64 2.298 25 24 79.9 2.547 26 25 61.2 2.419 26 25 79.9 2.64 27 26 58.7 2.531 27 26 80 2.73 28 27 56.6 2.63 28 27 79.8 2.821 29 28 55 2.731 29 28 79.9 2.913 30 29 53.9 2.837 30 29 79.8 3.001 31 30 53 2.938 31 30 79.9 3.092 32 31 51.9 3.032 32 31 79.6 3.187 33 32 50.6 3.133 33 32 79.5 3.28

34 33 79.3 3.37 35 34 78.7 3.47 36 35 78.3 3.56 37 36 77.4 3.656

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