Hybrid Water Tanks: A Novel Design Approach Integrating Ferrocement Lining with Reinforced Cement Concrete for Enhanced Structural Performance and Cost Efficiency

In this research, a novel approach is employed to design Intze water tanks, integrating reinforced cement concrete (RCC) with a specifically engineered ferrocement lining. In this groundbreaking design, RCC is engineered to carry all the external forces coming on the structure, with ferrocement lining specially designed to impart impermeability to the tank body. These pioneering tanks are referred to as hybrid water tanks. The design of the RCC tank follows the Limit State design method, adhering to IS 456:2000 (Reaffirmed in 2021) standards. Strain compatibility criteria are used for ferrocement lining design following the American Concrete Institute standards. This study endeavors to present a comprehensive methodology, detailed design, equations used, technicalities, and guiding principles for the design of Hybrid tanks. The study also presents the analysis of three hybrid Intze water tanks with capacities of 200 kL (Low), 600 kL (Medium), and 1,000 kL (High capacity). Subsequently, a comparative evaluation with designed Standard RCC tanks is also conducted. Criterion I of IS 3370:2021 is chosen for the design of Standard RCC tanks restricting the steel stresses to a maximum limit of 130 N/mm2. Dedicated modules within self-developed software programs, developed using the C++ language, are tailored for the design and cost calculation of both hybrid and standard RCC tanks. These programs incorporate limit state design, the continuity analysis approach, and heuristic optimization. The research findings highlight that hybrid tanks offer substantial cost savings, ranging from 28% to 38%, coupled with enhanced structural performance. Moreover, they demonstrate crack width reductions (48%–54%), reduced concrete (35%–40%) and steel (11%–46%) usage, minimized foundation area (10%–15%), and lower seismic shear (7%–15% when full, 14%–21% when empty condition) and lower deflection (11%–12% in full, 32%–43% in empty condition), making them a promising option for water supply.