Valuation of Strength of Structural Steel Angle Sections, under IS Code: 800 - 1984 – A Case Study with Equal vis-a-vis Unequal Angles

Abstract

Basically the structural steel is an alloy of iron, carbon-n-little parts of manganese, chrome nickel, sulfur, phosphorous-n-copper to form its rolled steel sections like angles, tees, channels, girders-n-plates which are used as beams, truss frames, columnbases, plate-girders etc to bear loads in the module of tensile-n-compressive stresses to safe the structure in deflection-n- bending. Structural steel is weather resistant and more stress bearing than normal steel. As normal specified steel is used in utensils, toys, vehicle-frames, furniture-n-watches etc., where loads and incoming varying stresses are not of structural type. While designing the steel structure two codes are usually followed viz. IS-Code: 800-1984 and Code 800-2000 which are known as elastic method and limit state method respectively. Elastic method is simple-n-easy to design the structure, wherein stress-strain relation is considered linear till yield stress. The permissible stress is kept by dividing it by factor of safety. Factor of safety is the failure load divided by working load. But it is not true for the material. As the material can resist load after the yield appear on the fiber of steel. Hence the section becomes uneconomical. In limit state working load is taken into account by multiplying the factor 1.5 to strengthen n serviceability of structure. The limitable strength is desired to avoid the collapse of the structure n safe the life. The permissible stresses are taken much higher than working stresses. In working stress, stresses are taken like ft=150N/mm² , while ft=227 N/ mm² -n-rupture stress 295N/mm² , are taken in limit state. Though the paper theme has no concern with design differentiation, however it is seem necessary to go to narrow analogous to the stresses in respective methods of design.