s funicular shell Environmental degradation witnessed today is a result of an e i perform contrary to their natural qualities. Most materials RCC has resulted in tensile structures which are made g materials. For example, a conventional beam upper region of the beam is in compression while o tensile stresses steel reinforcements are required in l capabilities. Upon inverting the structure, it is converted reduction in the amount of steel and cement. In this case, o developed in the structure. Traditionally n vaults, domes, catenaries and doubly curved been used extensively in the temples / forts. These h performance of such structures that have stood the test c The funicular shell roof is one such compression structure, which ensures e of natural resources by utilising waste materials effectively and tconservation optimising the use of expensive steel and cement. Further, the arch distributes
irresponsible use of materials. Materials are being being made to behave best in compression but the over reliance on to perform contrary to the natural qualities of the upon loading tends to bend at the centre. The the lower part is in tension, . To counter the the lower portion against its natural into a compression structure, with a considerable a nominal ring beam is capable of taking the lateral thrust compression structures in the form arches, structures also called funicular shells have structures are a standing proof of the durable of time.
FUNICULAR ROOFS-AN ALTERNATE TO RCC ROOFS
the point load in all direction equally thus, is able to withstand impact loading at any point. Diagonal g rid of funicular shell gives the illusion of a larger space. Eliminate use of high-energy steel reinforcement used in the conventional RCC roof. Allows efficient use of waste materials and provides personality, colour and texture. Minimises requirement of internal plasters. Provides roofing at a lower cost. !
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SALIENT FEATURES & ADVANTAGES
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A doubly curved structure on edge beam. Ensures optimal utilisation of steel and cement. Can be demoulded every 48 hours. A simple yet splendid roofing system using natural materials and technology as opposed to the monotonous and complex conventional system. Funicular shells can take any shape- square, rectangle, trapezium, triangular or any other shape. The knack lies in the casting of the mould. The upper half of the edge beam is required to hold the stirrups. It is cast along with the funicular shell; therefore, it can also be a triangular section. The funicular shell can carry various conduits, toilet pipes in the area above the brick bat layer. These can run along the periphery where the maximum depth is available. Funicular shell roof facilitates the installment of fixtures like- ceiling fans, light fixtures etc. A skylight can be introduced in the roof. This can be achieved by leaving a hollow while casting, using the inherent strength of a ring in compression. The edge beam can be given a slight camber or lift in the centre, about 1"-3". Thus, the beam also acts as an arch, comes under compression, further increasing its load bearing capacity. This also reduces the amount of steel and cement consumed in the beam. The funicular shell allows ample flexibility in design. Since it acts as an arch, it takes load in compression and distributes it equally in all directions. Thus, on the first floor, the wall can be placed anywhere since it will always rest on the arch.
DESIGN OF THE FUNICULAR SHELL ROOF
The entire area to be roofed is divided into a grid depending on the size of the funicular shell required or the size / shape of moulds available. The Edge beam / supporting beam is half cast. The reinforcement cage of the edge beam can either be pre welded or made in the conventional manner. The rise to span ratio is 1:6 thus; the optimal span of the shell is 3 m though it can span up to 15 m. The mould is supported between the edge beams. Timber planks are used to bridge the gap between the edge of the mould and the edge beam. A thin layer of sand is put on top of the mould with a layer of the finishing materials- brick / stone tiles / mud blocks etc. along the curvature of the mould or according to individual choice. Interesting patterns may be created by artistically mingling the chosen materials along with waste by-products e.g.- edging of marble / granite slab or broken tiles etc. Cement slurry in the ratio 1:2 is poured over the assembly and is allowed to settle. It keeps the finishing materials in position and facilitates pointing for a finished appearance. A second layer comprising broken stone / bricks is placed on edge so that it acts as a series of wedges resulting in an arch action. Removal of the mould within 48 hours strengthens the arch action. To achieve a flat surface, brickbats or
