Part 4 of IS 3370 (1967) delivers essential design tables critical for analyzing and designing concrete tanks intended for liquid containment. It furnishes engineers with detailed coefficients for moments, shear forces, and tensions across various tank wall and slab scenarios under multiple load conditions, enabling secure and effective structural designs. This section supplements other parts of IS 3370 by providing numerical values that facilitate the practical application of the code's design principles.
Overview
Part 4 of IS 3370 (1967) delivers essential design tables critical for analyzing and designing concrete tanks intended for liquid containment. It furnishes engineers with detailed coefficients for moments, shear forces, and tensions across various tank wall and slab scenarios under multiple load conditions, enabling secure and effective structural designs. This section supplements other parts of IS 3370 by providing numerical values that facilitate the practical application of the code's design principles.
Audience
Contents
Structure
This section outlines the applicability of design tables for rectangular and cylindrical tanks under diverse loading and support scenarios, including tanks constructed on or below ground level. It introduces fundamental formulas for moments in cylindrical walls subjected to rectangular and shear loads, referencing specific tables for coefficient values.
Details moment coefficients for rectangular tank panels with fixed vertical edges, emphasizing moment adjustments for continuity at shared edges. It includes aspect ratio considerations and provides example coefficients for walls with free tops and hinged bottoms.
Presents design tables for cylindrical tanks addressing boundary conditions such as fixed or hinged bases. Discusses load effects including ring tension, bending moments, and base shear, along with basic formulas and recommended assumptions for safer designs.
Focuses on calculating shear forces along tank wall edges and bases, detailing coefficient ranges depending on wall geometry and boundary conditions. It explains the impact of shear on axial tension in adjacent walls and its relevance in reinforcement design.
Describes methods to calculate ring tension in circular tank walls subjected to shear at the top, using coefficients from the code. It highlights important tables for tension and moment coefficients and notes conditions such as fixed or free edges.
Explains the approach to adjust moments for walls continuous with roof slabs, including the effects of roof slab deflection. References tables for moment factors and outlines formulas for moment calculations in continuous walls.
Provides moment and shear coefficients for wall panels under various edge fixity conditions, including hinged and fixed supports. Includes ranges of shear coefficients for different panel locations and loading cases.
Presents moment coefficients for rectangular and circular slabs subjected to uniform loads, detailing boundary condition effects. Includes design formulas and references tables for moment coefficients for cover and bottom slabs.
Discusses the influence of triangular and trapezoidal hydrostatic pressure profiles on tank wall design. Provides formulas and tables for calculating tension, moments, and shear under these load conditions, including considerations for underground tanks.
Summarizes moment and shear coefficients applicable for wall panels fixed on vertical edges with various top and bottom restraints. Includes tables and graphical representation for quick reference.
Details effects of shear forces applied at the base of tank walls, including displacement and reaction conditions for hinged and sliding bases. Provides formulas and coefficient ranges for shear distribution along wall height.
Describes the process for adjusting moment coefficients in rectangular tanks by accounting for rotation at shared edges using a moment distribution technique. Includes stepwise procedure and example coefficient values.
Outlines moment coefficients for circular slabs under different support and load conditions, including slabs with or without central support. Provides formulas and typical coefficient ranges.
Clarifies sign conventions for moments and shear in tank design, along with key formulas for moments and tensions under different load types such as triangular, rectangular, and trapezoidal loads.
Summarizes key features of the design tables, including moment coefficients for rectangular tanks and circular slabs, and outlines procedural flowcharts for selecting appropriate tables and designing reinforcement.
Frequently Asked
IS 3370 Part 4 offers moment coefficients for tank wall panels with vertical edges fixed but varying top and bottom edge conditions. Tables 1 to 3 cover top hinged-bottom hinged, top free-bottom hinged, and top free-bottom fixed scenarios respectively. For continuous rectangular tanks with free tops and hinged bottoms, adjusted coefficients are available in Tables 5 and 6. These ensure moments are balanced on both sides of common edges.
The standard provides shear force coefficients along vertical edges and bases of tank walls, recognizing their role in inducing axial tension in adjacent walls. Table 7 details shear coefficients for edges under various conditions, while Table 11 focuses on base shear in cylindrical tanks with hinged bases. Shear effects are combined with bending moments to design the required tensile reinforcement, considering edge fixity and load distributions.
IS 3370 Part 4 contains separate sets of design tables for rectangular tanks (Tables 1-3 for moment coefficients and Tables 7-8 for shear coefficients) and cylindrical tanks with dedicated tables for moment and shear coefficients reflecting their geometry. Rectangular tank moments require adjustments for edge rotations, whereas cylindrical tanks account for hoop and longitudinal stresses due to liquid pressure.
Triangular hydrostatic pressure, increasing linearly with depth, is addressed by tables providing ring tension, moments, and shear coefficients for tanks with fixed or hinged bases. Trapezoidal loads—combinations of triangular and uniform pressures—are handled by superimposing coefficients from relevant tables (e.g., Tables 11, 12, 13, and 14). These considerations ensure realistic modeling of internal and external pressures, including earth pressure on underground tanks.
The code advises starting with fixed end moments from Tables 1 to 3 assuming no rotation at common edges. It then treats the shared edges as artificially restrained and calculates unbalanced moments. By removing this restraint and applying a moment distribution method akin to frame analysis, induced moments are computed to balance moments on both sides of the edge. This adjustment ensures continuity and compatibility of moments along walls.
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