The 1985 edition of IS 11682 outlines detailed guidelines for designing reinforced cement concrete (RCC) staging that supports overhead water tanks. It includes principles for structural design, load assessment such as seismic and wind forces, reinforcement detailing, and configurations suitable for different tank sizes and shapes. This standard is vital for engineers engaged in creating robust, code-compliant elevated water storage structures in India.
Overview
The 1985 edition of IS 11682 outlines detailed guidelines for designing reinforced cement concrete (RCC) staging that supports overhead water tanks. It includes principles for structural design, load assessment such as seismic and wind forces, reinforcement detailing, and configurations suitable for different tank sizes and shapes. This standard is vital for engineers engaged in creating robust, code-compliant elevated water storage structures in India.
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Frequently Asked
According to IS 11682, the design must account for various load combinations including dead loads (self-weight of the tank and staging), live loads, wind loads, and water loads as specified in IS 875. Water weight is treated as dead load for staging but considered live load when directly acting on water-containing members. Both tank-full and tank-empty scenarios must be evaluated, including wave action effects where applicable. Load combinations adhere to IS 456 and IS 875 standards to ensure safe and serviceable staging designs.
IS 11682 requires that seismic forces be calculated based on IS 1893 guidelines, considering both full and empty tank conditions. The code mandates inclusion of hydrodynamic surge effects caused by water movement during seismic events. The RCC staging must be designed to withstand lateral seismic loads, ensuring structural stability and safety under earthquake conditions.
For circular shaft staging, IS 11682 specifies a minimum concrete shell thickness of 150 mm for shafts with internal diameter up to 6 meters. For larger diameters, thickness increases according to the formula: Thickness = 150 + (D - 6000)/120 mm, where D is internal diameter in millimeters. Vertical reinforcement must constitute at least 0.25% of the concrete cross-sectional area, arranged in two layers near each face using deformed bars of minimum 10 mm diameter. Maximum spacing should not exceed twice the shell thickness or 400 mm, whichever is smaller.
IS 11682 recommends that tall staging structures, particularly in seismic zones with coefficients above 0.05, incorporate twin diagonal vertical bracing made from steel or RCC to enhance lateral stability. Vertical bracing should include gusset and stiffener plates to handle load transfer effectively, with minimum steel insert plate thickness of 12 mm. Horizontal bracing must resist bending moments and shear forces from vertical and horizontal loads, ensuring overall structural stability under worst-case load combinations.
For column staging in seismic areas with seismic coefficients exceeding 0.05, IS 11682 advises foundations such as individual footings designed per IS 456, combined footings (with or without tie beams), raft foundations as per IS 2950, continuous strip, annular strip, or mat foundations. The design must include tying all columns together above and below ground level using braces or ring beams to improve seismic resilience and load distribution.
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