Bambu

Construction with Bamboo - Bamboo Connections

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Bamboo Connections

Introduction

Aspects of bamboo connections

The characteristics of bamboo induce parameters for processing
Bamboo itself has a lot of advantages using it for building houses, bridges... . It is a cheap, fast growing material with excellent statistics according to the mechanical properties. Theconnections are the difficult structures in bamboo constructions. Here are a few reasons:
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Bamboo has got a round profile. Creating connections with round profiles are leading to difficult geometric structures at the knot.

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Construction with Bamboo - Bamboo Connections

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Bamboo fibres only grow inthe longitudinal direction. Bamboo is hollow. There is no material to tighten the bamboo in the middle of the cane. The face of the cane is very slippery and hard. Bamboo is not suitable for loads in cross direction, because there are no cross fibres. Bamboo is a natural material, that varies in diametres, lenght and quality according to the climate.

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bending and impact fractures
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This report tries to show, how these problems are solved in several examples of different kind of connections.

nail splitting the bamboo

Least-Tech versus High-Tech
There seem to be two parties in modern bamboo architecture:
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those who use bamboo as an alternative material connected with industrial standard elements like steel plates, nuts and bolts and those who try to find amodern least-tech connection which can be produced very cheap and assembled by unskilled workers.

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Traditional least-tech connection

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Different aims followed by the use of bamboo lead to different connection layouts. We chose the way that powertransition is done as a criterion to seperate them from each other.

A modern steel connection by Shoei Yoh

Note: This paper is especially about connecting full bamboo canes. If you use splitted bamboo, there are of course far more possibilities.

Overview
types of connections
friction-tight rope connections
Friction-tight rope connections are the common connecting method. Traditionallynatural materials are used:
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cocos/sago palm fibre bast strips of bamboo rattan

For tight connections green bamboo strips are used, the fibres are watered before tying around the bamboo. While drying, the fibres shorten and the connection becomes stronger. Nowadays also industrial materials are used:
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iron wire (zinc coated) plastic tapes/ ropes

connection with bamboo stripsfile://D:\www.bambus\new\eng\reports\connect\index\pdf.html

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Construction with Bamboo - Bamboo Connections plugin/bolt connections

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Plugin/Bolt connections: Constructions with secondary interlocking elements are often used in context with rope connections. In this case the bolts have to transfer tractive and compressive forces. In wooden connections this isdone by different kinds of profiles. The metallnail is a perforating element. If the bamboo is not fresh at all, the bamboo is often splitted by the wedge shaped nail. There are two exceptional cases: The Guadua angustifolia and Chusquea bamboo from central and southern Amerika.

bracket interlocking stud

positive fitting connections
Wooden connections with slit and tenons, like they aretraditionaly used for carpenter-like constructions in Germany, are rare. There are three reasons:
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bamboo is round bamboo is hollow bamboo splits

positive fitting connection

But although there are these problems, positve fitting connections are used in traditional bamboo buildings. Different kinds of holes are cutted into the bamboo and make it possible to connect the round bamboo...