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Construction with Bamboo
Diplom-Ingenieur Christoph Tönges |
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Idea
In timber construction, gluelam beams are produced by glueing together
individual timber planks. These beams provide higher strength values
than conventional ones because the used timber is sorted out so that
possible weak parts got eliminated.
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(148) Production of gluelam in Germany | ||
The production of corresponding products represents a big chance for the
countries, that are 'blessed with the wealth of bamboo'. But equally it
is a chance for the nature since bamboo binds more CO2 than most
trees and, moreover, produces more biomass than timber due to its fast growth.
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(149) Production of glued bamboo in China | ||
Laminated bamboo has similar qualities like laminated timber, however, it is
much more elastic
(>earthquake-proof).
For example, in China it was used for construction of airplanes in the World
War II - in contrast to steel bamboo is not only powerful but also lightweight.
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(150) Products of laminated bamboo in China | ||
Manufacturing process
To be able to glue Guadua, rectangular slats must be extracted from the
canes at first. There are different ways for this:
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(151) Guadua slats | ||
If the bamboo cane is divided using a special circular saw with two parallel
saw blades the slats only have to be planed on two sides. Depending on the
diameter, five to eight slats can be extracted from one Guadua culm. The
distance of the two saw blades corresponds to the requested slat width.
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(152) Special circular saw | |||
We produced a very simple solar dryer to dry the green slats:
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(153) Solar dryers | ||
In our experiments we cut away the interior and exterior curve of the
half-done slats with two other parallel circular saws, too. The possible
slat height and so the distance of the circular saw blades is determined
by the particular wall thickness of the different bamboo culms.
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(154) Special circular saw | ||
The Guadua slats were glued this way: To manufacture the beams we glued the
individual slats together on the broad side. The interior side of the slats
with their coarser fiber structure were glued to the interior side of the
following slat and vice versa, to raise the bending stiffness of the beam.
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(155) Product spectrum | |||
Two beams can be combined (next to or on top of the other). Also constructively advantageous I-beams can be produced, laminated bamboo boards consist of crosswise glued slats. |
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(156) Board and I-beam | (157) Laminated bamboo board | ||
Tests
In order to learn more about the mechanical-technical material properties of the produced Guadua beam, we made several tests with beams of different forms and lengths at the Universidad Nacional de Colombia in Manizales. Influencing forces as well as the resultant deformations were recorded and analyzed afterwards. |
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(158) Testing glued bamboo | |||
The observation of the way the tests failed revealed interesting realizations
about the product properties. The laminated bamboo beams were supported at
both ends and the load was put on at two points.
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(159) Elastic deflection | |||
Specimens of approximately 1,50 and 3 meters in length were tested. The failure
behavior of these two lengths differed much, because the longer beams were
produced of 1,50 meters long, offset glued slats.
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(160) Failure of a beam of 3 meters in length | |||
The approximately 1,50 meters long specimens were glued of one slat per layer. At failure these tests behaved similar to bamboo canes. In fact, the high shear stresses led to longitudinal cracks. The failure always took place at the interior side of the culm wall, because it is weaker than the exterior side. The beams do not collapse completely, so a remaining load-carrying capacity is still available in case of shear failure. |
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(161) Shear failure of a 1,50-meter-specimen | |||
The I-beam behaved very well. Because of its favorable cross-section form, the deflection under load was relatively low until failure. This specimen was 1,50 meters long and had no joints in the slats, therefore it failed due to shear stress in the lower area. |
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(162) Shear failure of the I-beam | |||
The experimental production of glued bamboo and the subsequent tests showed that Guadua serves very well as source material for high-quality products with good material properties. However, the development of marketable products with uniform quality standards is still required. Both the possibilities and the demand for these products do exist. For now, it is necessary to study the latest findings and to carry on working on this chance. |
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(163) Tests | |||
Jörg Stamm wrote a study about this topic by order of the 'Deutsche Gesellschaft
für Technische Zusammenarbeit'
(GTZ)
at their partner university in Pereira
(UTP).
He illustrated the results of the above presented experimental production, the
exploitation of Guadua culms, the production techniques, as well as costs and
economic efficiency of corresponding production installations. The abstract of the
study can be download here:
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(164) Observing a test | |||
Bibliography
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Links
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