Bamboo as a Construction Material

With emphasis on building elements

Presented by-Sethu Sai Krishna- 271286Nithin Shenoy T - 271299Karan Shiyal - 271302Bharath Chandra- 271317Sai Praveen - 271331Anudeep Raviteja - 271343

I N T R O D U C T I O N

Bamboo is a versatile, strong, renewable and environment friendly material.

It is exceedingly strong for its weight and can be used both structurally and as a finish material.

Bamboo is recognized as one of the most important non-timber forest resources because of the high socio-economic benefits from bamboo based products. Bamboo can be recombined into useful products and elements such as flooring, ceiling, walls, partition walls, trusses, domes, etc.

O B J E C T I V E S

1. To study important characteristics of bamboo as it significantly contributes to the structural soundness and durability of the houses.

2. To explore and study the modern construction techniques of bamboo used for the construction of building elements.

B A M B O O I N B U I L D I N G S

Bamboo has good engineering properties and it is a feasible substitute for other materials for housing and construction sector.

Bamboo has high tensile strength, very good strength to weight ratio. It can be easily worked upon by simple tools.

It can resist forces created by high velocity wind and earthquake.

Bamboo and components made of bamboo are environment friendly, energy efficient and cost effective.

SELECTION OF BAMBOO SPECIES

It should be available in large quantity from near by plantations.

Transportation should be economic.

It should have good engineering properties.

Considering these factors, Dendrocalamus Strictus is selected as it is available in abundance in the region and has good engineering properties to be used as a construction material.

B A M B O O S I Z E S Bamboo sizes are generally specified by minimum diameter, wall thickness, and length.

Column – 80-100mm dia

Wall thickness – 10-12mm dia

Bamboo strips for infill panels – 18-20mm wide, 8-10mm thick

A building system in which bamboo comprises of various elements and fulfils the main structural role. Round bamboo columns and trussed rafters act as the main load bearing element. Composite bamboo grid/cement mortar infill panels act as shear walls to resist wind and seismic forces. The system comprises of – FOUNDATION: individual column footings. COLUMNS: bamboo culms set in/on concrete footing. WALL INFILL: a grid of split bamboo covered in wire mesh and cement mortar. FLOOR: raised by 2-3 brick courses, filled with rubble and screeded. ROOF STRUCTURE: bamboo rafters or trusses supporting bamboo purlins. Corrugated bamboo mat board for roof covering. DOORS AND WINDOWS: bamboo mat board shutters.

B A M B O O : A B U I L D I N G S Y S T E M

B A M B O O P R O T E C T I O N

Bamboo is susceptible to attack by insects and fungi, and its life could be as low as one year when it is in ground contact.

PROTECTION BY DESIGN

1. Large roof overhangs prevent direct wetting of walls in heavy rains.

2. Drainage channels/gutters to discharge water at a safe distance from the building.

3. The risk of flooring can be reduced by building on a slightly sloping site and using raised masonry or concrete footings.

1. Raising bamboo columns or wall panels clear of the ground reduces risk of termite infestation.

2. Termite shield formed out of galvanized steel or aluminum sheet between footing and walls.

3. Hollow culms should be plugged.

4. Cavity walls should be avoided.

PROTECTION BY DESIGN

PROTECTION BY PRESERVATION

DIP DIFFUSION METHOD

Bamboo culms are prepared to size and submerged in Borax/Boric Acid solution which is a water soluble preservative for several days. The preservative enters the culm through ends and holes drilled in internodes.

This process is suitable for both green and dry bamboo.

The bamboo to be treated is submerged in a tank of preservative that is directly heated by fire after being maintained at a constant temperature for a period, the tank is allowed to cool.During the cooling process, the preservative is drawn into the bamboo. The hot and cold method can be used for green or dry bamboo culms with either Boron or Creosote.

HOT AND COLD METHOD

A N O V E R V I E W

STAGES

1. Treated bamboo columns are in/on steel shoes or individual concrete footings. The plinth is built up to floor level using bricks, stones.

2. Timber wall plate is fixed to the tops of the columns. Treated bamboo strips are wired to other and to steel dowels passing through the column.

3. The grid is covered in chicken mesh. Cement plaster is done on both sides of the grid to a finished thickness of 50-60mm.

FOUNDATION AND FLOOR DETAILS1. Where the column is set in the footing, it should be

(400x400x400)mm deep. Where the column is set on the footing using a cast-in steel shoe, the footing should be (400x400x400)mm deep.

2. The floor is raised by 200-400mm above the ground level, using bricks, concrete blocks/stones, to define plinth perimeter. It is filled with compacted earth, topped with half bricks and screeded with 20mm of cement mortar. COLUMNS

1. Treated bamboo culms, 80-100mm in dia, provide basic load bearing framework for the building. The columns are spaced at intervals of 1.2m.

2. Timber wall plate, 100x38mm in cross section is fixed to the columns by screwing or skew-nailing into wooden plugs.

WALL INFILL PANEL

1. The wall infill comprises a grid of split bamboo, 20x10mm, tied together at 150mm spacing using mild steel binding wire, and set between the columns.

2. Chicken mesh is fixed on the outer face of the grid.

3. Cement plaster is applied on both sides to a finished thickness of 50mm.

ROOF

1. The roof comprises bamboo trusses at 1.2m spacing, located over the columns.

2. The 3mm BMCS are laid and fixed using J-bolts and bitumen washers.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R S All structural members like columns, beams, trusses, purlins are pre-fabricated and made of bamboo. Bamboo Mat Corrugated Sheet (BMCS), Bamboo Mat Board door and window

frames and panels are the special features of this housing project. COLUMNS

After completing conventional plinth, columns are erected. For a single dwelling 6

columns are required.

Bamboo column cap and gusset plate made

out of bamboo mats

Pre-fabricated Bamboo

column with cross bracings

Column ready for erection

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R S COLUMNS

Wall section with foundation details

Column is embedded in PCC 1:2:4 up to +750mm

GL

Prefabricated bamboo columns are aligned and erected over concrete pedestal, to avoid ground contact.

Water repellent coat is applied over the part of column, which is embedded in concrete in order to minimize water absorption by bamboo from 1:2:4 concrete at the time of fixing into concrete.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E RCOLUMNS

Column details

Bamboo Brackets supporting the roof

Bamboo screwed to avoid splitting

Column consists of 4 bamboos interconnected with cross bracings. Cross bracings also reduce effective length of column and helps in increasing load carrying capacity of column.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R SBEAMS

Beam ready for erection

Column, Truss and Beam junction

Beam resting on column and supporting BMCS

For a single dwelling 4 beams are provided. Single beam consist of 4 long bamboos with cross bracings. Additional bamboos are provided to facilitate the arrangements of shelves and lofts.

4 bamboos are convenient to place column cap, fix beam and truss over cap.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R STRUSS

Truss ready for erection

Bamboo pre-fabricated truss supporting BMCS and purlins. Also seen, bamboo mats used in upper 1/4th area of wall for light and ventilation.

3 trusses are required for a single dwelling. Queen post trusses are pre-fabricated as per drawings and specifications. Fabrication of truss member is comparatively complicated. Single bamboo is sufficient as a structural member of a truss though the double member is provided considering aesthetics and convenience for joinery.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R SCOMPOSITE WALL

Plan

Composite wall consists of –

Bamboo mat as a filler.

Wire mesh fixed over mat surface.

Plaster in cement mortar 1:6 on both sides.

Brick masonry in cement mortar 1:6 is provided from plinth level up to 300mm height and composite wall starts at this

level.

Composite wall detail

Bamboo mat consists of half split bamboos placed vertically at 300mm c/c. Lower end of half split bamboo is inserted in brick masonry. Upper end is fixed to the tie beams and extended up to inner surface

of BMCS.

F A B R I C A T I O N O F S T R U C T U R A L M E M B E R SCOMPOSITE WALL

Column separate bamboo mat

Horizontal strips woven around half

split bamboo

Bamboo columns are covered with bamboo strips in such a way that junction between wall panel and columns will be free from gaps. Columns are covered separately to facilitate alteration and modifications without damaging the composite wall panel. Wire mesh is fixed over mat surface, as stretched as possible and 20mm thick cement plaster in cement mortar 1:4 is applied over mat surfaces on both sides. Total thickness of Composite wall is 75mm which provides good temperature insulation.

M E R I T S O F B A M B O O I N B U I L D I N G1. AFFORDABILITY Foundations are minimized, wall panels are non-load bearing and can be reduced in thickness, and the basic components (bamboo, wire, bolts, chicken mesh) are inexpensive.

2. SUSTAINABILITY AND ENVIRONMENTAL IMPACT Bamboo is a renewable resource with a short rotation period and can be grown on degraded land. It is treated using environment-friendly preservatives. The use of high energy embodied materials (cement, steel) is

minimized.

3. CULTURAL ACCEPTABILITY The system offers traditional materials in a modern engineering context.

4. DURABILITY AND SAFETY All bamboo components are treated with safe preservatives to give extended life, the structure is engineered to resist wind and seismic forces, and other imposed loads.

5. IMPROVED JOINTING TECHNIQUES

M E R I T S O F B A M B O O I N B U I L D I N G

Nailing is eliminated; wiring, bolting and strapping provide

positive connections.

6. MODULAR CONSTRUCTION Bamboo is suited to both prefabrication and fabrication in situ: All components are designed to be prefabricated (ex-infill grids, roof trusses) or prepared on site.

7. EASE OF ASSEMBLY Only basic carpentry, masonry tools and skills are required to

undertake construction.

D E M E R I T S O F B A M B O O I N B U I L D I N G1. Bamboo lacks natural durability which contributes to the view of

bamboo as a temporary material.

2. Bamboo is susceptible to attack by insects and fungi and its service life could be as low as one year when it is in ground contact.

3. Bamboo cannot span very large structures and high rise buildings cannot be made from it.

4. Bamboo Mat Corrugated Sheets absorbs moisture more as compared with asbestos and plastic corrugated sheets. This may influence its durability in external utilization.

R E C O M M E N D A T I O N S

Cashew nut oil should be applied over exposed bamboo regularly, to improve the life and service of bamboo members and aesthetic also.

To make proper joints, bamboo should be screwed and not nailed to avoid splitting of bamboo.

Bamboo screwed to avoid splitting

After fabrication, culms should be closed from both sides with proper infill material, to avoid insects and termites enter it.

Culms closed from both sides with

suitable material

REFERENCE

NMBA - National Mission on Bamboo Application, Delhi - The Bamboo book (Training manual) - Building with Bamboo (Training manual)http://www.bambootech.org/subsubtop.asp?subsubid=110&subid=42&sname=usage

Internet

www.villagevolunteers.org/wp-content/uploads/2011/06/Bamboo-House-Building-Manual.pdf

CIBART -Centre for Indian Bamboo Resource and Technology

INBAR –International Network for Bamboo and Rattan

Thank you