EXPERIMENTAL AND ANALYTICAL STUDY ON FUNICULAR CONCRETE SHELL FOUNDATION UNDER ULTIMATE LOADING

Shell foundations are economical alternatives to the conventional flat shallow foundation, regarding material-saving technique. Shell foundation comes under the category of the shallow foundation. Concrete funicular shells of square plan, double curvature with various thicknesses are analyzed for the concentrated load. Specimens of size 680 × 680 mm are prepared using cement M30 concrete grade for which the mix design is carried by IS method. Formwork is prepared by concrete above which test specimen is prepared. The specimens are prepared with various thicknesses of 40 mm, 50 mm, 60 mm. The specimens are moist cured for 28 days before testing. The concentrated load over the column is applied, and the corresponding deflections and settlement characteristics are measured within elastic range. Beyond elastic range specimens are subjected to fail, and the ultimate loads are determined. The experimental result shows that load carrying capacity for 60 mm thick specimen (8 mm ɸ bar) is more compared to 40 mm and 50 mm thick specimen. Also by increasing the area of steel of edge beam reinforcement by 40% causes the increase in ultimate load carrying capacity by 15% and it also reduces the maximum settlement by 26%. A comparative study of the flat foundation and shell foundation shows that ultimate load carrying capacity for shell foundation increases by 50%. Finite element analysis was done using SAP 2000. Using the finite element model, a parametric study was conducted to determine the changes in stress level in the funicular shell. The magnitude of concentrated load used for the FEM analysis is same as the ultimate load of experimental work.