Case Study IV: Inspiration Office in Cochin, by Jaygopals.

Presentation

The office covering an area of 2750 Sft was built in 2002 and is probably the first and largest of its kind in India: Inspiration’s office complex is built almost entirely with engineered bamboo, be it the floor and roof slabs and the walls
Bamboo is used as a composite along with optimized RCC members, ferro-cement and limited quantity of reinforced plaster, so as to arrive at an attractive, functional and cost effective technology.

The climate in Cochin is warm and humid. The building planning concept is woven around openness in plan that keeps the communication flowing yet maintains privacy. The orientation of the building is such that the north east morning winds blowing over the pond get cooled and flow into office areas. Passages act as buffer zones stopping the rain and harsh light from entering workspaces. The use of natural lighting and cross ventilation for all spaces thus minimizes fans artificial lights installations.

Structure

Considering the presence of poor soil and high ground water, the two storied building is founded on a system of footings and raised columns to support the bamboo reinforced floor slab.
The structure stands on stilts, which reduces the chances of dampness seeping in as well as the attack on the bamboo by wood by rodents and insects. All bamboo used has been given preservative treatment. Depending on the function, three different types of preservative treatment have been tried out: hot dip treatment, cold dip treatment and pressure treatment. Almost a third of the bamboo used in the building has been taken from the site itself.
The building is a framed structure designed for a loading condition of approx. 400 kg/m² live load and to withstand wind speeds of up to 200 km per hour. Walls and slabs within the shell are made up with bamboo sticks where gaps in between -due to its irregularity - are filled with cement mortar. Chicken mesh is then rolled out to ensure strength of the structure before laying the concrete slabs or plastering the walls.

Bamboo being a light material, the entire dead weight of the building has been reduced to almost 1/3 rd of a similar building done with conventional RCC slabs and masonry walls bringing down the cement and steel consumption by almost 70%. The other advantages are the thermal insulation provided by the hollow cavity of bamboo and additional carpet area because of reduced wall thickness.

This relatively low self weight of the bamboo reinforced floor and roof slab permitted the use of pre-cast optimized RCC columns and beams. The cracking of cover concrete for the slender RCC members was prevented by employing steel micro fibre reinforcement. The monitoring of column and beam members have not shown any evidence of cracking of cover concrete thereby eliminating hazard of corrosion of the main reinforcement.

In addition to exploiting the properties of bamboo, other ecologically sensitive and cost saving practices that have been incorporated are:
 An anaerobic treatment plant (DEWATS) treats the sewage and waste water from the office. The system consists of an anaerobic baffled reactor, planted gravel filters and a polishing pond. The treated water is recycled for gardening.
 Rain water harvesting is done to collect the rain water in a pond which serves as a beautiful landscape element. Water proofing in the pond is done in the following way: local clay is used as a liner for seepage control. The clay liner is protected by a PE membrane and locally available stone to prevent cracking and mechanical damage of the clay liner.

Achievements

•It is noteworthy that almost 25% of the bamboo used in the building was obtained from the neighbouring bamboo plantation. All the bamboo used for this building was treated with preservative treatment to meet functional requirement. A total of 2500 full bamboo of length 3m and average diameter 90mm has been used in the building.

•The temperature difference from the exterior to the interior averages 4-5 °C on a hot summer day providing the thermal comfort as well as saving of energy of air conditioning.

•This construction has been able to reduce the use of 70 to 80% cement and steel, by the use of bamboo compared with a building of same design built with conventional materials.

Conclusion

The most significant achievement by doing this building could said to be that Inspirations’ architects have now field tested the engineered bamboo composite technology based on preservative treated bamboo tension reinforcement and are able to overcome all the difficulties related to dimensional instability and durability thereby enhancing the bamboo performance.

The self weight of the building reduces by around 50%, which can be very advantageous while used for multi-storeyed buildings as the structural frame members can be optimized to reduce the consumption of steel and concrete.

Inspirations’ architects have after this building, built 5 other buildings where bamboo has been similarly used as structural floor slab, roof slab and walls. Another 10 buildings are under way.