Structural Investigations on Cost Effective Roofing Technology

Development of cost effective roofing system built with precast ferrocement elements is discussed. This roofing technology is exclusively designed for innovative / affordable / rapid-built / disaster-resistant SERCular Housing Technology developed by CSIR-SERC. This type of rural house is built of a 2-roomed unit, proposed for Pradhan Mantri Awas Yojana – Garmin (PMAY-G), consisting of each room as a standard 4-meter diameter circular module. For this type of housing, the proposed roofing system is designed to cover over the 4-m. diameter (spanning across the circular walls), with the precast rectangular ferrocement joists reinforced by chicken-wire mesh plus welded mesh and 8-mm rods. The ferrocement planks are used for lateral spanning on the two parallel joists placed at 0.4m spacing. Each of the precast ferrocement elements are designed to weigh less than 200kg, for the ease of manual handling, with-out the necessity of machines / cranes. In-situ screed concrete of 40mm thickness was laid on this roofing system made of precast ferrocement joists and planks, to enable them to act monolithically and for structurally connecting different precast elements. The full-scale / prototype roofing system for 4-m. span with overhang of 0.3m on either end for a total length of 4.6m and 0.8m width, is constructed for load testing. The structural investigations are carried-out on this roofing system by flexure testing, with gradually increasing UDL in the structural testing laboratory of CSIR-SERC. The test procedure is illustrated. Test results are tabulated and the conclusions are drawn. The advantages of this type of precast ferrocement roofing system are described.