There is beauty in bamboo
The overall design of a bamboo structure is not complex, we only need to shed ourpre-conceived notion.
When we see a great work of architecture, it is worthwhile to wonder how such unique construction, style and the building method itself evolved. Typically, we attribute it all to the new generation of qualified engineers, builders and architects. In contrast to these, we also see how the traditional knowledge transmits from generation to generation, possibly improvising the idea each time.
The new visitor facility along the sea beach of Puri town in Orissa is a case in point. A Nagaland-style structure is being built there by Naga craftsmen, with Naga bamboo. The super-structure recently got completed, showcasing how it is built, an ideal time to understand building with bamboo.
Critical thought has been given to the foundation, made in concrete to withstand beach conditions with the bamboo culms embedded into the well ring mass concrete. This also gives the necessary rigidity at the foundation level to reduce the swaying of the structure in wind.
Bamboo is used for all columns, beams, floor joints, diagonal ties, bracket supports and lintels. If single units suffice for a support or beam its fine, but the hall being large single bamboos lack the required strength and load carrying capacity. So, all structural elements are in composites, i.e. multiple bamboos tied together without touching each other, but with one bamboo space in between. Small bamboo pieces are used as spacers.
Cross members are inserted into the gap between bamboos such that column and beam start to act like a single load bearing entity. Diagonal ties are very important in bamboo buildings, which help in creating equilibrium between the horizontal and vertical members, also avoiding sideward swing. Wooden members can be joined at the same alignment, but bamboos cannot. They need to overlap each other and tied together.
Multiple bamboos in one joint is a visual delight, but care should be taken to maintain the alignments, besides proper load carrying junction between any two. Since the location of members shift, so too can the centre lines of plan grid itself. To avoid it, columns are maintained in the same position, with beam members slightly to the left or right of the column bamboos.
Traditionally, thinly split bamboo peels, reeds, jute and such others were used to tie the members, but nowadays long nuts and bolts are becoming common. These bolts need to be cut and threaded to the required length, with rust proof coatings. While drilling the hole for the bolt, bamboo should not get split. It is observed that nut and bolt system may go loose in case of vibration due to heavy footfall, widened hole size or bamboo with more sap content than prescribed. Incidentally, Naga bamboo with thicker outer shell is less vulnerable to this problem.
The overall design of a bamboo structure is not as difficult as people talk about, but are very basic in nature. We only need to shed our pre-conceived notions about bamboo.