This standard outlines comprehensive procedures for utilizing steel tubes in general building construction. It covers essential aspects such as design methodologies, allowable stress limits, fabrication, jointing techniques, and corrosion protection measures, providing vital information to ensure structurally sound and long-lasting tubular steel frameworks.
Overview
This standard outlines comprehensive procedures for utilizing steel tubes in general building construction. It covers essential aspects such as design methodologies, allowable stress limits, fabrication, jointing techniques, and corrosion protection measures, providing vital information to ensure structurally sound and long-lasting tubular steel frameworks.
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Frequently Asked
The code endorses welding as the primary method for creating rigid joints in steel tube structures, ensuring material efficiency and strength. Riveting and bolting are also acceptable alternatives, particularly where welding is impractical. Connections should preferably be tube-to-tube without gusset plates, and tube ends may be flattened or formed to facilitate these joint types. Design should consider the actual rigidity of welded joints in accordance with relevant standards.
Permissible stresses in welded joints are determined based on the effective throat thickness and weld length, with stress calculated on this effective weld area. Allowable tensile, compressive, and shear stresses must not exceed the lower of the permissible stresses specified for YSt 25 steel tubes or the parent material. Axial permissible stresses for tension and compression follow prescribed values depending on tube grade and slenderness ratio, with adjustments made for dimensional tolerances.
Minimum thicknesses vary according to exposure conditions and protective coatings. For tubes coated with a red oxide-zinc chromate primer and maintained regularly, thicknesses of at least 4 mm are required for weather-exposed tubes, 3.2 mm for non-exposed, and 5 mm for structures difficult to access for maintenance. When using a zinc primer and paint system, minimum thicknesses of 3.2 mm (exposed) and 2.6 mm (non-exposed) apply. Compliance with IS 1161 for structural tubes is mandatory.
Steel tubes that are not galvanized must be coated with paint, oil, or other protective finishes prior to weather exposure. For tubes exposed to weather, a multi-layer coating system comprising a zinc primer followed by one coat of paint and two additional coats is recommended, with renewal every two years. Tubes painted with red oxide-zinc chromate primers require periodic maintenance, and minimum thicknesses are specified to ensure adequate corrosion resistance.
The code advises minimizing eccentricity by aligning the gravity axes of interconnected tubes to prevent bending moments from eccentric loads. When axes do not intersect, welds must conform to specified clauses ensuring the intersection curve remains within permissible bounds. Rigid welded joints should be designed accounting for their actual rigidity, with full fixity effects considered in structural analysis to maintain structural integrity.
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