Conventional and ferrocement-based hybrid design of RCC tanks: a comparative study

Abstract

The design of reinforced cement concrete (R.C.C) water tanks follow the standards prescribed for Concrete structures retaining aqueous liquids. For Tightness Class I structures, the standard mandates a crack width not exceeding 0.2 mm. This can be achieved by maintaining steel stresses below 130 N/mm2, eliminating the need for crack width calculations, referred to as Type I tanks, or else by increasing the steel stresses up to the ultimate stress limit, including crack width calculations, referred to as Type II tanks. Type II tanks are chosen for this comparative study due to their cost-effectiveness, attributed to significant steel savings as compared to Type I. Despite steel savings, Type II tanks underutilize materials (both steel and concrete) and are bulky due to stringent minimum dimensions norms, limiting material stresses and crack width criteria. Additionally, post-construction leakage persists in Conventional Tanks. To address both leakage and cost concerns, this study introduces Hybrid tanks, integrating a ferrocement lining for impermeability, designed for strain compatibility, with an R.C.C. tank body adhering to Indian standards for R.C.C. structure design. Hybrid and Conventional Intze water tanks, with capacities of 200, 600, and 1000 kiloliters, undergo meticulous design using an in-house developed C++software program for the comparative study. This software program incorporates heuristic optimization, continuity-based analysis, and the limit state design method. Comparatively, Hybrid tanks offer significant cost savings (20% to 28%), enhanced structural performance, and notable reductions in crack width (46–52%), concrete usage (30–36%), and steel consumption (11–20%). These tanks exhibit reduced deflection (10–16% in full, 38–46% in empty tanks), minimized raft area (10–35%), and lower base shear (4–6% in full tank, 16–23% in empty tank), establishing them as efficient alternatives for water storage. © Springer Nature Switzerland AG 2024.