Introduction Bamboo Materials
Bamboo which does belong to the grass family – has been associated with various names such as
“poor man’s timber”(low-class material, because people tend to choose brick, concrete and steel as structural and construction materials for modern buildings)
“Cradle to Coffin”
Due to its utilization in the industrial sector, food products, construction & structural application, wood substitutes & composites, and handicraft& cottage industry.
The bamboo building materials have been used abundantly in traditional houses is because it grows abundantly in eastern parts of India and some of the southern parts of India. The use of bamboo was obsolete after the commencement of the industrial era as it is cheap and non–permanent material.
After the hot issues of global warming and sustainability, bamboo is being used as a substitute in place of high–quality woods for construction (to reduce deforestation as the wood takes time to regrow and use as construction material) because bamboo can be harvested in a short time of 3-5 years.
Bamboo construction material has become a sustainable building material as it releases oxygen into the air, an ability that cannot be performed by industrial materials like steel, plastic, and concrete.
Bamboo Growing Areas in India
Property of Bamboo as Construction Material
Bamboo is a family of bambusoideae, and bamboo’s growth character is divided into types: monopodial and sympodial bamboo. Monopodial bamboo roots spread horizontally in shallow depths of soil where the new shoots are produced at a relatively long distance from the parents’ plant.
Sympodial bamboo roots grow very close to parents’ plant, forming a clump of many stems or canes, majority of bamboos found in India are sympodial rhizomes.
Bamboo rods are round, segmented, jointed, and hollow. Bamboo culm consists of 50% parenchyma, 40% fiber, and 10% conducting tissue which indicates that as a construction material, bamboo has a very strong fiber.
- The compressive strength of bamboo is at least twice of concrete.
- Tensile strength of bamboo (28KN/sq.in) is close to steel (23KN/sq.in).
- Shear stress of bamboo fibre is higher than wood, even wider span than wood.
- Curving bamboo is possible without breaking or damage.
- The high elasticity of bamboo makes it useful as a building material in areas of high risk of earthquakes.
- Anisotropic property of bamboo, i.e., possesses cellulose fibre in the longitudinal direction making it strong and stiff while lignin in the transverse direction makes it soft and brittle.
- The fire resistance of bamboo is good, can withstand a temperature of 400°C
Besides the advantageous property of bamboo, bamboo is vulnerable to termites and fungal attacks. So, it is preserved using borax boric acid solution through several techniques, such as immersion, gravitational or vertical soak diffusion, and injection using a compressor machine. Moreover, borax acid is capable to extend the life span of bamboo. Apart from this,
- Bamboo shrinks by 10-16% in cross–section and has a wall thickness of 15-17% that is more than wood when loses water. Measures are taken to prevent water loss when used as a building material.
- Prone to rapidly catch fire by the friction among the culms during wind(in the forest).
- Jointing- although many jointing techniques exist, their structural efficiency is low.
- Untreated bamboo structures can hardly survive with an expected life of a maximum of 5 years.
“Organic form forms that have been generated or created or inspired by natural forms in nature, whose adaption generates irregular geometrics.”
Purpose of Bamboo at Different Age
|2-3 years||Bamboo Boards or Laminations|
|6-12 years||Gradually loses strength|
Uses of Bamboo In Building Construction
The organic form of bamboo has been used in almost all parts of house construction except for the fireplace and the chimneys. The different Use of bamboo in construction are given below,
Timber in contact with damp ground gets deteriorate and decay, so for foundation purpose preservative measures are essential. Different types of bamboo foundations identified are:
Bamboo In Direct Ground Contact
In this type, bamboo is placed either on the surface or buried. Strength and stability are assured either by using large–diameter and thick-walled sections of bamboo with closely spaced nodes or where such bamboos are not available – smaller sections can be tied together.
In addition, preservative treatment is recommended as it can decay within 6 months to 2 years.
Bamboo On Rock Or Preformed Concrete Footings
Here, in this foundation, the bamboo is being used for bearings after placing the largest and stiffest section of bamboo is placed out of ground contact on footings of either rock or preformed concrete.
Composite Bamboo-Concrete Columns
Here, in this foundation, the durability of the foundation is enhanced by providing a concrete extension to a bamboo post using a plastic tube of the same diameter.
To stabilize sift soils and reduce building settlement – treated split bamboo piles were filled with coconut coir strands wrapped with jute and these sections were then tied with wire. Finally, after the installation of the piles, the area was covered with sandy material.
The floor is raised above the ground creating a stilt type of construction that provides a covered storage area below the floor. The surface of the earth floor can stabilize by paving it with crude bamboo boards made by opening and flattening whole culms. The various types of bamboo used are:
Small Bamboo Column
These are directly tied and nailed together
Split Bamboo Column
Culms are along their length into strips
Here the green bamboo culms are split by removing the diaphragms, then rolling and flattening them. As a result of this, the board is laid across the joists and fixed by nailing or trying which is finally screened with cement mortar as they are uneven and difficult to clean.
Thin strips of bamboo of size 5-6mm or 10-15mm with a thickness of 0.6-1.2mm are woven into mats of different sizes based on the availability of hot-press plates and users’ demands. When the mats are dried to 6-10% moisture content, sufficient glue is applied to ensure enough bonding between the overlapped areas.
Bamboo Plastic Composites
Here the bamboo fiber is compounded with plastic as the core material of the flooring which adds higher resistance to water, and more dimensional stability than those of normal flooring.
Bamboo is extensively used in walls and partitions where the posts and beams are the structural frameworks, that carry the self-weight of building and moving loads.
An infill between framing members not only completes the wall but also serves the purpose of protecting against rain, wind, and animals, to offer privacy and stability of overall structure to compete against horizontal forces.
4. Doors and Windows
Bamboo frames can be substituted in place of timber frames of the appropriate function. Reed boards are the reeds pressed flat at high temperatures, usually used in the elements like flooring, walls, ceiling and roofing, partitions, doors, windows.
For doors, by hinging the bamboo mat shutters fixed to the bamboo frame – to the wall or a panel of bamboo board fixed to the frame – to the wall. For windows, small frames of bamboo can be hinged to the top of the wall.
The bamboo structure of a roof comprises purlins, rafters & trusses because it is strong, resilient & light–weighted.
Bamboo purlin and beams supported on perimeter posts are the simplest forms. The first layer of halved culms is laid on a convex side down, edge-to–edge, spanning from the ridge to eaves. The second layer, opposite to that is laid convex side up, to cover the joints.
Corrugated sheets made of bamboo have been used as a roof covering where, bamboos are generally dipped in resin, dried, and heated under pressure in a platen to enhance the property of bamboo, for instance, strong, reliable, and lightweight sheets( assuring good insulation properties).
A layer of bitumen sandwiched between two mats of bamboo forming a semi-rigid panel, fixed at an interval of 200-250mm, followed by finishing of bituminous or rubberized weatherproof coating.
6. Plaster Bamboo
A cement plaster, with or without organic fiber is applied to bamboo roofs, to get the strong roof covering. Trusses of bamboo culms of diameter 40mm-100mm are also adopted(usually king post trusses).
Due to the excellent load-bearing capacity and weight of bamboo, it is used in the construction of scaffoldings even for tall buildings where only lashed joints are used.
The cane extension has been carried out by lashing the cane ends together with several ties in such a way that forces act vertically downwards wedges the nodes in the lashing. Soft lashing is exclusively used to join the vertical and horizontal canes.
The benefit of such a technique is that the joints can be re–tensioned to the right degree without difficulty and can also be quickly released again.
Bamboo Construction Details
The construction from bamboo lasts only if the joints are strong. The following are bamboo construction details that make it strong:
Construction Techniques of Bamboo for Organic Shaped Buildings
Organic shape buildings usually use arch, spline, or another curvature shape by curving the bamboo. According to Dulkenberg, there are two methods of bamboo bending:
- Hot bending method
- Cold bending method
Hot Bending Method
It can be done by immersing in the lukewarm water until the fibres become soft enough to curve using the clamp, or by heating the bamboo section to the desired heat of more than 150°, which cause bamboo fibres to become soft and easy to bend.
Cold Bending Method
It can be done by splitting the bamboo into planks then tying it into a bundle, or slashing the rods of bamboo. Depending on the method of bending, the bamboo can be smoothly or segmentally curved as well as the strength of bamboo can be increased or decreased.
The bamboo split method is flexible and easy to construct which can be used to create a smooth curve even spline shape. But there is a drawback of this method, that it can decrease the strength of bamboo and may lead to structural deformation and deflection.
To prevent it, sufficient dimension proportion to the span is needed.In addition to these methods, the advantage of natural curve bamboo shall be taken, which depends on species, soil condition, and environment. Natural curve bamboo joined in a row gives the series of continuous curve shapes. This method can be used to create arches or spline roof ridges.
Joinery is usually done by inserting smaller bamboo into the culm, or by inserting other materials, such as resins. Besides natural curved bamboo, curved shapes, especially arches, can be created by bending and bundling smaller bamboos.
What Are The Property of Bamboo as Building Construction Material?
What Are The Method of Bamboo Bending?
The Following Two Methods of Bamboo Bending,
Hot bending method
Cold bending method
What is The Hot Bamboo Bending?
It can be done by immersing in the lukewarm water until the fibers. become soft enough to curve using the clamp, or by heating the bamboo-section to the desired heat of more than 150°, which causes bamboo fibers to become soft and easy to bend.
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