TRADITIONAL AND INNOVATIVE JOINTSIN BAMBOO CONSTRUCTION From the Faculty of Architecture of the RWTH Aachen University to obtain the academic degree of Doktor der Ingenieurwissenschaften/ Doctor of Engineering Approved Dissertation Submitted by Andry Widyowijatnoko Advisors: Univ.-Prof. Dr.-Ing. Martin Trautz (RWTH Aachen University) Univ.-Prof. Dr.-Ing. Bernd Baier (University of Duisburg-Essen) Date of the oral examination: 13.07.2012
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TRADITIONAL AND INNOVATIVE JOINTS�IN BAMBOO CONSTRUCTION
From the Faculty of Architecture
of the RWTH Aachen University
to obtain the academic degree of
Doktor der Ingenieurwissenschaften/
Doctor of Engineering
Approved Dissertation
Submitted by
Andry Widyowijatnoko
Advisors:
Univ.-Prof. Dr.-Ing. Martin Trautz (RWTH Aachen University)
Univ.-Prof. Dr.-Ing. Bernd Baier (University of Duisburg-Essen)
Date of the oral examination: 13.07.2012
TRADITIONAL AND INNOVATIVE JOINTS�IN BAMBOO CONSTRUCTION
Von der Fakultät für Architektur
der Rheinisch-Westfälischen Technischen Hochschule Aachen
Bibliografische Information der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in derDeutschen Nationalbibliografie; detaillierte bibliografische Da-ten sind im Internet über http://dnb.ddb.de abrufbar.
Satz: nach Druckvorlage des AutorsUmschlaggestaltung: Druckerei Mainz
printed in GermanyD82 (Diss. RWTH Aachen University, 2012)
Das Werk einschließlich seiner Teile ist urheberrechtlich geschützt. Jede Verwendung ist ohne dieZustimmung des Herausgebers außerhalb der engen Grenzen des Urhebergesetzes unzulässig undstrafbar. Das gilt insbesondere für Vervielfältigungen, Übersetzungen, Mikroverfilmungen und dieEinspeicherung und Verarbeitung in elektronischen Systemen.
Andry WidyowijatnokoTraditional and innovative Joints in Bamboo construction
ISBN: 978-3-86130438-41. Auflage 2012
i
Abstract
The use of bamboo as building material has been ascending recently due to the rise
in public environmental awareness. Bamboo is one of the most sustainable building
materials. It is a renewable resource that grows quickly. As a low-energy building
material in its natural form, bamboo is traditionally associated with the cultures of
Asia and South America. Its strength, enormous availability, and easy workability
have made it a dominant building material throughout much of the world, where it has
grown natively for centuries. Its use in modern, mainstream construction, however, is
rare. A few pioneering architects and engineers in South America and South East
Asia have demonstrated bamboo’s potential for high-end buildings, but they remain
the exceptions.
Despite this progress, using bamboo as a structural material remains difficult,
especially as a tension element. Although bamboo has extremely high tensile
strength, the lack of a joining system to accommodate its strength makes the
application uneasy. The characteristics of the bamboo itself generate the difficulties
in bamboo joinery. The round shape and cavities inside the bamboo are two of those
characteristics. Therefore, it is a special task to develop tension loadable joints to
expand the range of structural applications of anisotropic bamboo pole.
The main objective of this phenomenological and experimental research was to
propose new tension loadable bamboo joints. The secondary objective was to
classify bamboo constructions and bamboo joints to put the proposed bamboo joints
in a context. The development of new bamboo joints classification was based on the
classification by Janssen (2000).
Three types of tensile loadable bamboo joints were proposed: utilizing the
hollowness of bamboo; using the outer part of bamboo by enlacing a steel wire; and
employing the shear and the bearing strength of bamboo by attaching perpendicular
elements. After a comparison study, the chosen lashing-based bamboo joints were
developed in an experimental research. A loop of steel wire using a kind of lasso knot
was twined around the bamboo in such way that it will tighten by pulling the wire.
Tension force induced in the steel wire by an element inserted inside the cavity of the
ii
bamboo was converted to radial compression perpendicular to the fibers to the center
of the pole causing a circumferential stress in bamboo.
Preliminary tests were conducted to determine the radial compression strength of the
bamboo. There were two types of winding: one and three hemispherical-windings.
The result of these tests was used to calculate the load capacity of the joint under
radial compression.
After calculating the strength of the joint in each component against its corresponding
load, three samples of lashing joints with eye-bolts were tested. Two types of failures
happened: the wire sliced the bamboo after the rings slipped into the holes; and the
wire broke off. The average strength of the joints of 34.09 kN almost passed the
ultimate strength of the used steel wire.
Based on the results above, the joint was improved by replacing the eye-bolt with a
rod and some cross-dowels in such a way that similar lashing technique can be
multiplied in every joint. As a result, it spread the force over a wider surface area of
bamboo, and it was called bamboo joint with multi knots.
The tension tests on the bamboo joints with multi knots showed an expected result,
as the failures of three samples happened in the rods when they broke off. The
average tensile strength was 77.91 kN, beyond the ultimate strength of the used M16
rod. This type of failure is very important, because the user can predict the strength
of this joint more precisely. After using a bamboo with approximately similar diameter
and wall thickness, the strength of bamboo joint with multi knots can be customized.
After the rod with certain tensile strength is chosen, the number of knots in
accordance with the strength of each wire can be determined.
Developed from traditional lashing techniques, this bamboo joint with multi knots
provides a relatively cheap and easy joint, which can be made even by an unskilled
worker. Therefore, this joint can bolster the utilization of bamboo pole as a tension
element in vernacular bamboo construction. Furthermore, the capability to transfer
both tensile and compression force without eccentricity makes this joint also suitable
for space structures.
iii
Kurzzusammenfassung
Die Verwendung von Bambus als Baustoff ist in letzter Zeit mit zunehmendem
Umweltbewusstsein gestiegen. Bambus ist einer der tragfähigsten Baustoffe
überhaupt. Zudem ist er ein nachwachsender Baustoff, der schnell wächst. Bambus
als energiearmer Baustoff in seiner natürlichen Form wird traditionell mit den
asiatischen und südamerikanischen Kulturen in Zusammenhang gebracht. Durch
seine Beanspruchbarkeit, enorme Verfügbarkeit und einfache Verarbeitung wurde er
zu einem vorherrschenden Baustoff in weiten Teilen der Welt, in denen er schon seit
Jahrhunderten natürlich vorkommt. Seine Verwendung in modernen, tragenden
Konstruktionen ist jedoch selten. Einige bahnbrechende Architekten aus Südamerika
und Südostasien haben bereits das Potential von Bambus für hochwertige Gebäude
demonstriert.
Trotz dieses Fortschritts gestaltet sich die Verwendung von Bambus als Baustoff
schwierig, besonders beim Einsatz als Zugelement. Obwohl Bambus eine extrem
hohe Zugefestigkeit aufweist, erschwert das Fehlen geeigneter Verbindungssysteme,
die Anwendung. Es sind zum Teil die besonderen Eigenschaften von Bambus,
welche die Schwierigkeiten hervorrufen. Dazu gehören die runde Querschnittsform
und der innere Hohlraum. Deswegen ist es eine besondere Aufgabe
zugbeanspruchte Verbindungen zu entwickeln, um die konstruktive Anwendung von
Bambusstäben weiter auszubauen.
Das Hauptziel dieser phänomenologischen und experimentellen Forschung war es,
neue Bambusverbindungen zu erarbeiten, vor allem solche mit zugbeanspruchten
Verbindungen. Ein weiteres Ziel war die Klassifizierung von Bambuskonstruktionen
und Bambusverbindungen. Der Zweck dieser Klassifizierungen bestand darin, die
entwickelten Bambusverbindungen in einen Zusammenhang setzen zu können.
Diese neue Klassifizierung wurde weiterentwickelt aus einer früheren Klassifizierung
nach Janssen (2000).
Es wurden drei Typen von zugbeanspruchten Bambusverbindungen entwickelt: unter
Ausnutzung des Hohlraums des Bambus, der Inanspruchnahme des äußeren Teils
des Bambus durch umlaufende Stahldrähte und unter Ausnutzung der Scher- und
Tragfestigkeit des Bambus durch die Anbringung senkrechter Elemente. Nach einer
iv
vergleichenden Studie wurden die ausgewählten drahtverspannten Bambus-
verbindungen in einer experimentellen Untersuchung weiterentwickelt. Es wurde eine
Stahldrahtschlinge mit einer Art Lassoknoten so um den Bambusstab geschlungen,
dass sie sich beim Ziehen des Drahtes verengt. Die in den Stahldraht eingeleitete
Zugkraft wird so in umlaufenden Druck umgewandelt, der senkrecht zur
Faserrichtung im Inneren des Bambusstabs verläuft. Dazu wurden Vorversuche
durchgeführt, deren Ergebnisse zur Berechnung der umlaufenden Druckfestigkeit
des Bambus dienten. Dabei wurden einfache und dreifache Umwicklungen
untersucht.
Nach Berechnung der Druckfestigkeit der einzelnen Komponenten der Verbindung
abhängig von ihrer Last werden drei Exemplare von drahtverspannten Verbindungen
mit Augenbolzen untersucht. Es traten zwei Arten des Versagens der Verbindungen
auf. Der Draht schnitt in den Bambus, nachdem die Ringe in die Löcher rutschten;
oder der Draht riss. Dabei überschritt die durchschnittliche Festigkeit der Verbindung
von 34.09 kN beinahe die höchste Zugfestigkeit des verwendeten Stahldrahtes.
Ausgehend von den vorigen Versuchsergebnissen wurde die Verbindung durch
Ersetzen der Augenbolzen mit einer Gewindestande und einigen Kreuzdübeln so
verbessert, dass eine ähnliche Verspannungstechnik vervielfacht werden konnte.
Dies hatte den Effekt, dass die Kraft auf eine größere Bambusoberfläche übertragen
werden konnte. Diese Ausführungsart wird Bambusverbindung mit Mehrfachknoten
genannt.
Spannungsversuche an diesen Bambusverbindungen führten zum erwarteten
Ergebnis, als die Verbindungen jeweils durch Brechen der Gewindestangen
versagten. Die durchschnittliche Zugfestigkeit betrug 77.91 kN, was über die
Festigkeit der benutzten M16-Stange hinausging. Diese Art des Versagens ist
besonders hilfreich, da der Nutzer so die Festigkeit der Verbindung präziser
vorhersagen kann. Durch Benutzung eines Bambusstabs mit ähnlichem
Durchmesser und Wanddicke, kann die Festigkeit der Bambusverbindung mit
Mehrfachknoten angepasst werden. Zuerst wird die Gewindestange mit einer
bestimmten Zugfestigkeit ausgewählt/festgelegt, danach kann die Anzahl der
notwendigen Knoten in Abhängigkeit von der Stärke der einzelnen Drähte bestimmt
werden.
v
Entwickelt aus traditionellen Wickeltechniken, stellt diese Bambusverbindung mit
Mehrfachknoten eine sehr einfache und günstige Verbindung dar, die sogar von
unerfahrenen Arbeitern hergestellt werden kann. Somit kann diese Verbindung den
Einsatz von Bambus als Zugelement in traditionellen Bambuskonstruktionen
begünstigen. Zudem eignet sich diese Verbindung durch die Fähigkeit, sowohl Zug-
als auch Druckspannung ohne Exzentrizität zu übertragen, auch für räumliche
Tragwerke.
vi
vii
Acknowledgements
First of all I would like to thank to Allah swt by saying alhamdulillah to make all things
possible. I would like to express my gratitude to all those who gave me the possibility
to complete this dissertation. I want to thank the Government of the Republic of
Indonesia and the Institut Teknologi Bandung for giving me a scholarship and the
permission to commence this dissertation in the first instance.
I am deeply indebted to Univ.-Prof. Dr.-Ing. Martin Trautz, the owner of the Chair of
Structures and Structural Design, who supervised, helped, encouraged me in all the
time of research and also gave me the chance to conduct a Bamboo Seminar during
my doctoral study, a priceless teaching experience. I would like to express also my
gratitude to Univ.-Prof. Dr.-Ing. Bernd Baier as co-promoter with his valuable hints
and suggestions, and to all promotion commissioners: Univ.-Prof. Dr.-Ing. Christian
Raabe, Univ,-Prof. Dipl.-Ing. Anne-J. Bernhardt and Univ.-Prof. Dr.phil. Alexander
Markschies.
Of the many people who have been enormously helpful in the preparation of this
dissertation, I am especially thankful to Dr.-Ing. Hans-Willi Heyden for his enormous
help and support in the research and daily life in the chair, and also to Dr.-Ing. Evelin
Rottke who facilitated me studying here and gave me so many valuable bamboo
literatures. My former colleagues from the Chair of Structures and Structural Design
supported me in my research work. I want to thank them for all their help, support,
interest and valuable hints. Especially I am obliged to Mazen Ayoubi, Rico Klüsener,
Christoph Koj, and Arne Künstler for all their assistance on the structural design and
calculation and of course to Dr.-Ing. Rolf Gerhardt for every inspiring moment
attending his class. My deepest appreciation I address to Jochen Dahlhausen and
his team from Holzwerkstatt; Michael Staack from Metalwerkstat; and Herr Braun and
Guido Lowis from Institut für Bauforschung (IBAC) for their support in the making and
testing bamboo joints.
I would like to acknowledge and extend my heartfelt gratitude to Petra van der
Klaauw with her Berdenis van Berlekom Foundation for material and immaterial
support; to Irene Bück who made administration things much easier; to Indah, Kim
viii
and Kathy as my English proof reader; Elisa as German translator and Depoy for
bridge drawing rendering.
I dedicate this dissertation to my beloved wife, Intan, my mother, and my family for
their unconditional love and support in every way possible throughout the process of
this course, this dissertation and beyond. Last but not least, I devote it to the world of
bamboo with great hope that this research will give valuable contributions.
2� Characteristics of Bamboo as Building Material ............................................. 7�2.1� Anatomy of Bamboo Pole .......................................................................................... 7�2.2� Mechanical Properties of Bamboo ........................................................................... 12�
3� Classification of Bamboo Pole Constructions .............................................. 21�3.1� Traditional or Vernacular Bamboo Construction ...................................................... 23�3.2� Engineered Conventional Bamboo Construction ..................................................... 26�3.3� Substitutive Bamboo Constructions ......................................................................... 28�
4� Classification of Bamboo Joints ..................................................................... 31�4.1� Group 1: Transferring compression through contact to the whole section ............... 35�4.2� Group 2: Transferring force through friction on the inner surface or compression to
the diaphragm .......................................................................................................... 36�4.3� Group 3: Transferring force through friction on the outer surface ............................ 38�4.4� Group 4: Transferring force through bearing stress and shear to the bamboo wall
from perpendicular element connected from inside (4A) or outside (4B) ................. 41�4.5� Group 5: Transferring force perpendicular to the fibers ........................................... 45�4.6� Group 6: Transferring radial compression to the center of the pole through shear
and circumferential stress perpendicular to the fibers ............................................. 46�4.7� Combinations ........................................................................................................... 47�
4.7.1� Group 1 and 2 .................................................................................................. 48�4.7.2� Group 1 and 3 .................................................................................................. 51�4.7.3� Group 1, 3 and 4B ............................................................................................ 51�4.7.4� Group 1 and 4A ................................................................................................ 52�4.7.5� Group 1 and 4B ................................................................................................ 52�4.7.6� Group 1, 2 and 4 .............................................................................................. 53�4.7.7� Group 2 and 3 .................................................................................................. 55�4.7.8� Group 3 and 4B ................................................................................................ 56�4.7.9� Group 2, 3 and 4A ............................................................................................ 57�
x
5� Development of Bamboo Joints for Tension ................................................ 59�5.1� Development of Joint Using the Hollowness of Bamboo ......................................... 60�
5.2� Development of Joint with Elements Attached Perpendicular to the Fibers ............. 63�5.3� Developments of Lashing Joint Attached on the Outside ........................................ 64�
5.3.1� Lashing Configuration ...................................................................................... 66�5.3.2� Lashing Joints with Twisting as Pre-Tensioning ............................................... 70�5.3.3� Lashing Joints with Swage Stud Terminal ........................................................ 71�5.3.4� Lashing Joints with Eye-Bolt ............................................................................ 72�5.3.5� Lashing Joints with Multi Knots ........................................................................ 74�
5.4� Comparison of Proposed Bamboo Joints ................................................................. 76�
6� Tension Tests on Lashing-based Bamboo Joints ........................................ 83�6.1� Understanding the Mechanism of Force Transfer in the Joint ................................. 83�6.2� Radial Compression Tests on Bamboo Tubes ......................................................... 88�
6.3� Tension Tests on Lashing Joint with Eye-Bolt ......................................................... 98�6.3.1� Methods and Materials ..................................................................................... 98�6.3.2� Calculations .................................................................................................... 100�6.3.3� Results ........................................................................................................... 108�6.3.4� Discussions .................................................................................................... 111�
6.4� Tension Tests on Bamboo Joint with Multi Knots .................................................. 119�6.4.1� Method and Materials ..................................................................................... 119�6.4.2� Calculations .................................................................................................... 122�6.4.3� Results ........................................................................................................... 124�6.4.4� Discussions .................................................................................................... 127�
7� Applications of the Joints ............................................................................. 131�7.1� Design Considerations ........................................................................................... 131�
7.1.1� Factor of Safety .............................................................................................. 131�7.1.2� Customization of the Tensile Strength of Bamboo Joint with Multi Knots ...... 133�7.1.3� Using Joint for Bamboo with Different Properties and Different Rings ........... 136�
7.2� Applications of the Proposed Lashing Based Bamboo Joints ................................ 138�7.2.1� Bamboo Space Structure ............................................................................... 139�7.2.2� Bamboo Tensegrity Sculpture ........................................................................ 140�7.2.3� Bamboo Bridge ............................................................................................... 143�
8� Conclusions and Suggestions for Further Works ...................................... 149�8.1� Conclusions ........................................................................................................... 149�8.2� Suggestions for Further Works .............................................................................. 152�
Figure 1-1: Research Framework ............................................................................................ 4 Figure 2-1: The upright habits of many bamboo species ......................................................... 8 Figure 2-2: The curve bamboo as an effect of growing environment ...................................... 8 Figure 2-3: Curve bamboos as roof frame ............................................................................... 9 Figure 2-4: Curve bamboos as column .................................................................................... 9 Figure 2-5: The extreme difference of the diameter and wall thickness .................................. 9 Figure 2-6: Positive fitting joint in an easy made temporary bamboo structure ....................... 9 Figure 3-1: Diagram of bamboo constructions classification ................................................. 22 Figure 3-2: Fish-mouth joint with bended thin strap and lashing ........................................... 24 Figure 3-3: Fish-mouth joint with two pinned flanges ............................................................ 24 Figure 3-4: Traditional bamboo gazebo in Indonesia with positive fitting and lashing joint ... 25 Figure 3-5: Planar frame in common vernacular bamboo construction ................................. 25 Figure 3-6: One layer frame of wall construction in Colombia ............................................... 25 Figure 3-7: Eccentricity of force transfer and the effort placing the joints near to the node ... 25 Figure 3-8: The capability of bolted joint to connect three big bamboos at once ................... 27 Figure 3-9: Eccentricity of load transfer in a joint ................................................................... 27 Figure 3-10: Two-dimensional frame with many layers ......................................................... 27 Figure 3-11: Three-dimensional frame and the beauty of the rhythm of repetitive frame ...... 27 Figure 3-12: The idea of using bamboo as space structure member .................................... 28 Figure 3-13: The development of bamboo connection to avoid eccentricity .......................... 28 Figure 3-14: Bamboo space structure by architect Leiko Motomura ..................................... 30 Figure 3-15: Bamboo as compression element in combination with steel ............................. 30 Figure 3-16: German-Chinese House in Shanghai Expo 2010 ............................................. 30 Figure 4-1: Connectors mapping ........................................................................................... 33 Figure 4-2: Main categories of bamboo joints classification .................................................. 34 Figure 4-3: Simplest joint of the bamboo column on a stone ................................................. 35 Figure 4-4: Fish-mouth joint ................................................................................................... 35 Figure 4-5: Expandable joint and steel tube joint ................................................................... 36 Figure 4-6: Bamboo joints with mortar injection ..................................................................... 37 Figure 4-7: An experiment of bamboo joint by using friction on inner surface ....................... 37 Figure 4-8: Lashing joint with coco-palm fiber and using drawing stick ................................. 39 Figure 4-9: Byxistem by Waldemar Rothe ............................................................................. 39 Figure 4-10: Lashing joint in scaffolding structures in association to a wedge mechanism ... 40 Figure 4-11: Bamboo joint attached on the outside by Georg Brusnowitz ............................. 41 Figure 4-12: Bamboo joints by Shoei Yoh ............................................................................. 43 Figure 4-13: Bamboo joint with steel tube and bolts .............................................................. 43 Figure 4-14: Gusset plate joint by Mark Mortimer .................................................................. 43 Figure 4-15: Failure by bending, shear and tension of gusset joint ....................................... 43 Figure 4-16: Two joints, proposed and tested by Clavijo and Trujillo in 2000 ....................... 44 Figure 4-17: Bending stress of bamboo beam ....................................................................... 46 Figure 4-18: A model of lashing joint using three ropes in different color .............................. 47 Figure 4-19: Joint between a pole and two steel wires ......................................................... 47 Figure 4-20: Sub-categories of bamboo joints classification ................................................. 48 Figure 4-21: Bamboo joint with wooden plug and with mortar injection ................................. 49 Figure 4-22: Wooden core connection by Arce ..................................................................... 50
xii
Figure 4-23: Bamboo joint with laminated bamboo connector and split bamboo filler ........... 50 Figure 4-24: Rigid bearing connection in vernacular bamboo construction ........................... 51 Figure 4-25: Rigid bearing connection in modern bamboo construction ................................ 51 Figure 4-26: Traditional bamboo tenon and dowel joint ......................................................... 52 Figure 4-27: Common T-joint in modernized conventional bamboo construction .................. 52 Figure 4-28: Fish-mouth joint tightened with lashing and dowel ............................................ 53 Figure 4-29: Fish-mouth joint with friction on the skin of the bamboo .................................... 53 Figure 4-30: Bamboo joint developed by Morisco and Mardjono ........................................... 53 Figure 4-31: A sliced part of T-joint to show the inner part filled with mortar ......................... 53 Figure 4-32: Bamboo joint by Clavijo and Trujillo before and after testing ............................ 54 Figure 4-33: Bamboo joint using steel ring and cup with plaster ........................................... 55 Figure 4-34: Full lapped splice joint and butt joint with side plates ........................................ 56 Figure 4-35: The use of lacing wire tool and bamboo joint by Renzo Piano .......................... 57 Figure 5-1: The improvement of Arce’s joint .......................................................................... 59 Figure 5-2: Two alternatives for cam joints ............................................................................ 60 Figure 5-3: An alternative joint with element inserted inside the cavity of the pole ................ 61 Figure 5-4: Ellipse plate joint .................................................................................................. 63 Figure 5-5: Bamboo joint with nailing and mortar injection .................................................... 64 Figure 5-6: The conceptual lashing configuration .................................................................. 67 Figure 5-7: Lashing configuration to avoid severe bending of the rope ................................. 67 Figure 5-8: Lashing configuration with two pairs of holes ...................................................... 68 Figure 5-9: Another alternative for lashing configuration with two pairs of holes ................... 69 Figure 5-10: Lashing configuration using small helical dowels .............................................. 69 Figure 5-11: The idea of connecting bamboo pole to a steel plate ........................................ 70 Figure 5-12: Lasing joint with swage stud terminal ................................................................ 71 Figure 5-13: The design of bamboo joint with eye-nut plus rod or eye-bolt ........................... 72 Figure 5-14: Two other alternatives for joint with eye-nut plus rod or eye-bolt ...................... 73 Figure 5-15: Lashing joint with two knots utilizing turnbuckle ................................................ 75 Figure 5-16: Lashing joint with multi knots to increase its tensile strength ............................ 76 Figure 6-1: Distribution of forces in the joint .......................................................................... 84 Figure 6-2: Finite element model for bamboo under diametric compression ......................... 84 Figure 6-3: Distribution of force in the rings ........................................................................... 86 Figure 6-4: Tangential friction (ff,�,T) in the joint ...................................................................... 86 Figure 6-5: Setting of the test equipments ............................................................................. 89 Figure 6-6: Deformation of bamboo tube ............................................................................... 90 Figure 6-7: The similar failure of cracking in the ends of the tube in both tests ..................... 91 Figure 6-8: Radial compression test results of Test A (Sample 1, 3, 5) ................................. 92 Figure 6-9: Radial compression test results of Test B (Sample 2, 4, 6) ................................. 92 Figure 6-10: Phenomena of the effects of different number of winding ................................. 93 Figure 6-11: The effect of frictions to the radial compressions on bamboo tubes.................. 95 Figure 6-12: Quarter part of bamboo tube in Test B .............................................................. 97 Figure 6-13: Equipment setting of the tension tests ............................................................... 98 Figure 6-14: Three samples with six similar joints ................................................................. 99 Figure 6-15: Original and reformed washers as rings to protect the holes in the bamboo ..... 99 Figure 6-16: Calculations of strength of each components in the joint ................................ 101 Figure 6-17. Whole cross section of bamboo reduced by the holes .................................... 102 Figure 6-18: Distribution of force from the rod to the wire .................................................... 103 Figure 6-19: Bearing stress by the ring on every hole within bamboo ................................. 104
xiii
Figure 6-20: Ultimate-load capacity of bamboo against shear stress ................................. 105 Figure 6-21: Radial compression forces and friction between steel wire and rings ............. 107 Figure 6-22: Diagram of the load capacity of each component in the joint .......................... 108 Figure 6-23: Sequential failures in Joint 4, Sample B .......................................................... 109 Figure 6-24: Sequential failures in Joint 5, Sample C .......................................................... 109 Figure 6-25: The failure of Joint 1, Sample A ...................................................................... 110 Figure 6-26: Diagram of the load and the deformation of three samples ............................ 110 Figure 6-27: Diagram of the load and the deformation of six joints ..................................... 111 Figure 6-28: Deformation of the rings and the bamboo ....................................................... 111 Figure 6-29: The deformation of the ring after test .............................................................. 111 Figure 6-30: Comparison of the strength in each part of the joint ........................................ 113 Figure 6-31: Distribution of forces in axis xyz ...................................................................... 115 Figure 6-32: Friction force parallel to the fibers (ff,�) ............................................................. 115 Figure 6-33: Proposed ring design and model for hole protection ....................................... 115 Figure 6-34: Diagram of ultimate tensile load capacity of the joints and connectors ........... 117 Figure 6-35: Diagram of ultimate tensile load capacity of the joints using turnbuckle ......... 118 Figure 6-36: Diagram of ultimate tensile load capacity of joints with 4 knots ...................... 119 Figure 6-37: Working drawing of the samples ..................................................................... 120 Figure 6-38: Diagram of the ultimate-load capacity of bamboo, connectors and knots ....... 124 Figure 6-39: Failures in the rods and severe damages in the plastic pipe .......................... 125 Figure 6-40: Light scratches and light deformation .............................................................. 125 Figure 6-41: Diagram of load and deformation of the three samples .................................. 126 Figure 6-42: Diagram of load and deformation of the six joints ........................................... 126 Figure 6-43: Comparison of the ultimate tensile load capacities ......................................... 129 Figure 7-1: Flow chart to determine the strength of each connectors ................................. 134 Figure 7-2: A sketch of bamboo joint with multi knots using ideal rings .............................. 136 Figure 7-3: Flow chart to use multi knots joint ..................................................................... 137 Figure 7-4: The application of the joint for space structure .................................................. 139 Figure 7-5: Conceptual application of lashing based bamboo joint for space structure ...... 140 Figure 7-6: Bearing joint of tensegrity sculpture using lashing joint with eye-bolt ............... 142 Figure 7-7: Lashing joint in the middle of the bamboo ......................................................... 142 Figure 7-8: Bamboo tensegrity sculpture ‘Pagoda‘ .............................................................. 143 Figure 7-9: An example of simple bridge design with 10 meters span ................................ 144 Figure 7-10: The detail of the joints ..................................................................................... 145 Figure 7-11: The calculation of forces distibutions in the bridge design .............................. 146
xiv
xv
List of Tables
Table 2-1: Mechanical phenomena of bamboo pole in relation to loadings due to the design
of mechanical joints .............................................................................................. 13�
Table 2-2: List of reports on the tensile strength of many bamboo species .......................... 17�
Table 2-3: List of reports on the modulus of elasticity of many bamboo species .................. 19�
Table 2-4: List of reports on compression strength of many bamboo species ...................... 20�
Table 5-1: Comparison of three groups of proposed joints .................................................... 77�
Table 5-2: Comparison of each proposed joint ...................................................................... 80�
Table 5-3: Comparison of many alternatives for bamboo joint with eye-bolt ......................... 82�
Table 6-1: Dimensions of the samples .................................................................................. 90�
Table 6-2: Dimensions of the samples ................................................................................ 100�
Table 6-3: Calculatory ultimate-load capacity of bamboo in each joint ................................ 103�
Table 6-5: Ultimate-load capacity against bearing stress in every joint ............................... 105�
Table 6-4: Ultimate-load capacity against shear force in each joint .................................... 106�
Table 6-6: Dimensions of the samples of joint with multi knots with its calculatory ultimate-
load capacity of the whole section ...................................................................... 121�
Table 7-1: The combination of rod, the number of knots and diameter of steel wires ......... 136�
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xvii
List of Symbol Definitions
�� area ������������ Point A, B, C,...
����� Point A, B at the bamboo ���� cross section area of bamboo ����� longitudinal section area of bamboo
����� Point A, B at the wire ��� diameter of hole within bamboo perpendicular the fibers � � inner diameter of bamboo ��� outer diameter of bamboo ��� diameter of ring �� eccentricity; mathematical constant approximately equal to 2.72 �� modulus of elasticity of bamboo
���������� force ����������������� tension force in the wire at P1, P2,...
������������������ force in axis AB, BC, CD,... ������������� total compression forces at Point R and S in Test A, Test B
����� total compression forces at Point T in Test B ����� compression force parallel to bamboo fibers
������� diametric compression perpendicular to bamboo fibers ������� distributed radial compression perpendicular to bamboo fibers ����� friction force parallel to bamboo fibers ����� friction force perpendicular to bamboo fibers ������� tangential friction force perpendicular to bamboo fibers
���������� minimum tension force induced in the rod until the failure caused by diametric compression to the bamboo perpendicular to the fibers
���������� minimum tension force induced in the rod until the failure caused by radial compression to the bamboo perpendicular to the fibers
���� minimum tension force induced in the rod until the wire break off ������������� tension force in R0, R1,...
������� compression force by the ring parallel to bamboo fibers ��������� diametric compression force by the ring perpendicular to bamboo fibers ����� Factor of Safety ����� tension force parallel to bamboo fibers
������������������� ultimate-load capacity of Sample A, Sample B,... ��������� average ultimate-load capacity of Sample A, B, C ��������� average ultimate-load capacity of Sample D, E, F �������� ultimate-load capacity of bamboo against bearing stress parallel to the fibers�������� ultimate compression strength of bamboo parallel to the fibers
���������� ultimate diametric compression strength of bamboo ���������� ultimate-load capacity of bamboo against radial compression ���������� ultimate tangential compression strength of bamboo �������� ultimate shear strength of bamboo parallel to the fibers �������� ultimate-load capacity of bamboo against shear stress parallel to the fibers �������� ultimate tensile strength of bamboo parallel to the fibers
xviii
�������� ultimate tensile load capacity of bamboo parallel to the fibers ��� ����� ultimate-load capacity of a knot parallel to bamboo fibers ���! ����� ultimate-load capacity of 4 knots parallel to bamboo fibers
����� characteristic strength of rod ����� ultimate-load capacity of rod ����� ultimate-load capacity of turnbuckle ���� characteristic strength of wire
������� compression force by the wire parallel to bamboo fibers ������ compression force by the wire perpendicular to bamboo fibers �������� distributed radial compression force by wire perpendicular to bamboo fibers ���� tension force in the wire
����!"#� tension force in the wire directing 45º relative to the rod �������� tangential tension force in the wire perpendicular to bamboo fibers
��$����%� total forces in axis x, y �� height
&���'�� horizontal, vertical reaction force in Point A (� distance between holes and end of bamboo
)(� movement of lower table relative to the upper plank of test machine *+� natural logarithm ,� moment -� point of origin .� load; pressure;
.���.������ Point 0, Point 1,... ���� reaction force of bamboo perpendicular to the fibers � � inner radius of bamboo ��� outer radius of bamboo �/�� outer radius of bamboo after radial deformation )��� deformation of the tube in the radial direction ����� reaction force of ring perpendicular to bamboo fibers ���� resultant vector of the wire under tension �� thickness of bamboo wall 0� weight; load
$��%��1� axis 2��3��4���� angle in radians, angle
53� angle of deformation 6�� coefficient of static friction 7� mathematical constant approximately equal to 3.14
8����� bearing stress or compression stress in bamboo parallel to the fibers 8����� compression stress in bamboo perpendicular to the fibers 8������� tangential compression stress in bamboo perpendicular to the fibers 8����� tension stress in bamboo parallel to the fibers 8����� tension stress in bamboo perpendicular to the fibers 8������� tangential tension stress in bamboo perpendicular to the fibers 9���� shear stress in bamboo parallel to the fibers 9��� shear stress in bamboo perpendicular to the fibers 9����� rolling shear in bamboo perpendicular to the fibers
1
1 Introduction
1.1 Background
Bamboos are distributed worldwide in tropical and sub-tropical countries. In Asia-
Pacific bamboo reaches the 42°S in New Zealand on south; the 51°N in Middle-
Sakhalin on north; the Pacific Islands on east; and southwest of Indian Ocean on the
west. The coverage of bamboo in America is relatively smaller. It grows from 47°S of
Southern Argentina to 40°N of the Eastern United States. In Africa, it stretches
starting from 22°S of Southern Mozambique to 16°N of Eastern Sudan. Those
regions, in which bamboo grows, are also considered as regions with the highest
population growth rates.
The history of bamboo as a housing material is probably as old as human civilization
where bamboo is available. It has essential roles and is widely utilized to fulfill so
many kinds of human needs including housing. The benefits of bamboo as a
construction material do not end with its availability. Amongst the easiest materials to
work with, bamboo provides all needs to build the house, from the frames (bamboo