The 2009 edition of IS 3370 Part 2 outlines comprehensive guidelines for the design and fabrication of reinforced concrete structures intended for liquid storage, focusing primarily on water retention. This standard elaborates on reinforced concrete design criteria, allowable stresses, reinforcement detailing, provision of movement joints, and crack mitigation strategies, thereby ensuring the safety and functional performance of liquid-retaining concrete constructions.
Overview
The 2009 edition of IS 3370 Part 2 outlines comprehensive guidelines for the design and fabrication of reinforced concrete structures intended for liquid storage, focusing primarily on water retention. This standard elaborates on reinforced concrete design criteria, allowable stresses, reinforcement detailing, provision of movement joints, and crack mitigation strategies, thereby ensuring the safety and functional performance of liquid-retaining concrete constructions.
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Contents
Structure
This section clarifies the boundaries of the code's application, excluding structures intended for hot liquids, low-viscosity volatile liquids such as petrol and diesel, dams, pipelines, lined structures, and certain chemical storage scenarios. It applies primarily to reinforced concrete structures for the storage of aqueous liquids at ambient temperatures, including sewage tanks with protective measures. Reference standards include IS 456:2000, IS 1786:2008, IS 3370 Part 1:2009, and IS 3370 Part 4:1967. Design and construction should follow IS 3370 Part 1 and IS 456 unless otherwise stated.
Focuses on ensuring structural safety and serviceability by verifying all relevant limit states. The ultimate limit state follows IS 456 guidelines for strength and stability, while serviceability limit states control deflections and cracking, with deflection limits typically ranging from span/250 to span/500. Crack width on exposed surfaces must not exceed 0.2 mm, with concrete cover specified according to exposure conditions to manage crack control.
Describes two primary design methods: the Working Stress Method and the Limit State Method. The design must account for hydrostatic pressures, thermal stresses, soil pressures (when applicable), and other imposed forces such as wind and seismic loads. Design tables from IS 3370 Part 4 provide pre-calculated thickness and reinforcement details aiding preliminary design. The fundamental hydrostatic pressure formula p = ρgh is highlighted.
Elaborates on the principles of limit state design where plane sections remain plane after bending, and materials are assumed elastic within limits. Tensile stresses in concrete are controlled to specified limits for crack resistance, while concrete tensile strength is disregarded for strength calculations. Key formulas for modular ratio, stress limits, and moment capacity are provided, along with permissible tensile stress values depending on exposure conditions.
Specifies permissible direct tension and bending tension stresses for various concrete grades, along with shear stress considerations per IS 456. Crack spacing and maximum crack width formulas are discussed, incorporating factors like bar diameter, bond strength, steel ratio, shrinkage, and thermal strains. Steel stress limits for crack control are provided separately for plain and deformed bars.
Outlines design principles for floors exposed to liquids, recommending limit state design for thin slabs and considering moments at floor-wall junctions. The choice of design method follows clauses 4.4 or 4.5, with materials and reinforcement detailed per exposure conditions. Typical bending moment and shear force calculations are summarized, supported by design tables from IS 3370 Part 4.
Describes structural behavior of walls subjected to liquid pressures, including vertical and horizontal bending moments and direct horizontal tension. Walls of rectangular and polygonal tanks act as two-way slabs with specified boundary conditions. Cylindrical tank walls are treated with fixed-base assumptions and ring tension moment coefficients. Permissible tensile stresses for direct and bending tension in concrete are provided.
Covers roof design for tanks as water-retaining elements, using either limit state or working stress design methods. Roof slabs, whether flat or domed, must resist hydrostatic, dead, live, and wind loads. Minimum concrete grades and cover thicknesses are specified, along with formulas for ultimate bending moments and reinforcement calculations. Recommended minimum slab thicknesses for various spans are included.
Provides requirements for bar sizes, spacing, laps, and bends per IS 456, considering concrete member depth. Minimum reinforcement ratios ensure crack distribution, with formulas for critical steel ratio and maximum crack spacing. Thermal and shrinkage strains are accounted for in crack width estimation. For thick sections, surface zones and reinforcement requirements are discussed.
Presents formulas to calculate maximum crack spacing and crack width considering concrete tensile strength, bond characteristics, bar diameter, steel ratio, shrinkage strain, and thermal contraction. Thermal contraction strain accounts for temperature drops from peak hydration and seasonal variations. Specific considerations for immature concrete and thick sections are included.
Details formulas for maximum crack spacing and crack width in mature concrete, factoring in tensile strength, bond strength, reinforcement layout, and thermal shrinkage strains. Thermal contraction strain is calculated based on concrete expansion coefficients and temperature variations. A table lists permissible tensile stresses for various concrete grades for crack resistance.
Lists the experts and representatives involved in drafting IS 3370 Part 2:2009, including chairperson, member secretary, and members from governmental bodies, research institutes, cement manufacturers, and engineering institutions. This multidisciplinary group ensures comprehensive coverage of reinforced concrete liquid storage standards.
Summarizes design principles based on working stress methods with emphasis on durability and watertightness. Highlights permissible stresses in concrete and steel, modular ratio application, and references design tables from IS 3370 Part 4 for reinforcement ratios and thicknesses. Encourages alternative design approaches for special cases verified by analysis or testing.
Frequently Asked
According to IS 3370 Part 2 (2009), permissible stresses for reinforced concrete liquid storage structures are mainly governed by IS 456:2000 and IS 3370 Part 1, supplemented with specific provisions. Concrete compressive stresses are generally limited to 0.45 times the characteristic compressive strength (f_ck), while tensile stresses in concrete are typically neglected, with tension resisted by steel reinforcement. Steel stresses for mild steel bars are limited to 0.87 times the yield strength (f_y), commonly 415 MPa for Fe 415 bars, and similarly for high-strength deformed bars as per IS 1786. These limits ensure compliance with durability, crack control, and leakage prevention requirements.
IS 3370 Part 2 addresses crack control by specifying maximum crack spacing and crack width formulas that consider concrete tensile strength, bond properties, bar diameter, steel ratio, shrinkage, and thermal strains. Minimum reinforcement is defined based on critical steel ratios that ensure crack distribution, with permissible tensile stresses for concrete provided for various grades. Reinforcement detailing follows IS 456 standards, and special considerations apply for thick sections and movement joint spacing to mitigate thermal cracking effects.
The standard recommends movement joints in compliance with IS 3370 Part 1 provisions, primarily contraction joints (partial or full) to control shrinkage and temperature stresses, supplemented with expansion joints to accommodate thermal expansion. Reinforcement must meet minimum criteria, and sliding layers beneath the tanks may be used to permit movement. For tanks storing water near ambient temperatures without drying, separate moisture or temperature stress calculations are unnecessary if these provisions are followed.
Walls and floors in liquid retaining structures must be designed considering hydrostatic pressure from the stored liquid and earth pressure if buried or backfilled, following IS 3370 Part 1 for earth pressure coefficients. Either limit state or working stress design methods can be employed. Structural elements exposed to moisture must adhere to IS 3370 provisions, while others follow IS 456. Reinforcement design must address bending, shear, and crack control to ensure structural integrity under combined liquid and soil pressures.
Yes, IS 3370 Part 2 permits the use of both Limit State Design (LSD) and Working Stress Design (WSD) methods for water retaining concrete structures. Designers may select either approach based on project requirements and preferences. LSD is a modern method that accounts for ultimate and serviceability limits, while WSD is a traditional approach based on allowable stresses. Structural elements exposed to water or moisture must be designed per IS 3370 Part 2, while those not exposed can follow IS 456.
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