DESIGN OF ELEVATED WATER TANK AND TOWER STRUCTURES

This project focused on the structural design of a 100 m³ elevated reinforced concrete (RC) water tank supported by a 20-meter-high tower. The objective was to ensure the structural safety, stability, and serviceability of all components including the raft foundation, tank base slab, beams, columns, and tank walls under combined actions of dead load, live load, hydrostatic pressure, wind, and seismic forces in compliance with BS 8110 and Eurocode 2 standards. The methodology involved manual structural design calculations for preliminary sizing and load estimation, followed by detailed structural analysis and modelling using ProtaStructure software. The structure consists of 300 mm × 300 mm reinforced concrete columns, 300 mm × 450 mm reinforced concrete beams, a 150 mm reinforced concrete raft foundation at ground level, and a 300 mm reinforced concrete tank base slab positioned at the top of the stanchions to safely support the water tank. The tank walls, which serve as the primary water-retaining elements, were designed as 250 mm thick reinforced concrete walls reinforced with high-yield steel bars (Grade 500) using 12 mm diameter bars spaced at 250 mm centres in both vertical and horizontal directions (H12-250) on both faces of the wall. The tank base slab was reinforced in orthogonal directions to resist bending moments and shear forces caused by hydrostatic pressure, self-weight, and wind effects. Beams supporting the platform and tank were subjected to maximum moments of 230.6 kN·m and axial loads of 191.1 kN, and were reinforced using T20 and T25 longitudinal bars together with T10 shear links. Columns carried maximum axial loads of 1443.6 kN and were reinforced with up to 4Y25 bars. The structural analysis revealed that the maximum lateral displacement of the structure was 9.87 mm at the top storey, which is within the allowable serviceability limit of H/500 according to Eurocode EN 1991-1-4 for a 20 m high structure. The slab deflections, beam moments, shear forces, and column forces were all within codespecified limits, indicating an efficient and stable structural system. The Bill of Engineering Measurement and Evaluation (BEME) estimated the total construction cost of the proposed elevated water tank and tower structure at approximately ₦19,114,573. The project concludes that the elevated reinforced concrete water tank and supporting tower satisfy all structural and serviceability requirements and that the integration of manual calculations with software analysis produced a safe, durable, and economical water storage structure suitable for practical implementation.