ANALYSIS AND DESIGN OF CIRCULAR CLARIFIER TANK

This study presents the structural analysis and design of circular clarifier tanks, which are critical components in water and wastewater treatment systems.The cylindrical geometry of such tanks results in hoop tension and bending moments under hydrostatic loading, making accurate analysis essential for safety, crack control, and durability.The design was carried out in accordance with IS 3370 (Part 2): 2009 for liquid-retaining structures and IS 456:2000 for reinforced concrete.Finite element modelling was performed using STAAD.Pro with beam and plate elements to capture structural behaviour effectively.Two parametric studies were conducted: one with constant diameter (6 m) and varying heights (6 m, 7 m, and 8 m), and another with constant height (7 m) and varying diameters (5 m, 6 m, and 7 m), with the H/Dt ratio adopted as the governing parameter.A uniform wall thickness of 300 mm was maintained across all models.The study also examined boundary conditions by comparing fixed and hinged wall-to-slab connections, while soil-structure interaction was considered using settlements of 25 mm and 50 mm.Analyses were performed for both full and empty tank conditions under hydrostatic, dead, and live loads.Reinforcement design checks confirmed compliance with IS code provisions for strength and crack width, ensuring cracks remained below 0.2 mm.The results demonstrate that increasing the H/Dt ratio significantly raises internal stresses, with fixed supports generating higher bending moments and hinged supports resulting in greater hoop tension.