According to IS 800 : 1984 the geometrical properties of the gross and effective cross section of a member shall be calculated.
Area of Cross-section and Member Thickness
According to IS 800 : 1984 the geometrical properties of the gross and effective cross section of a member shall be calculated on the following basis :
(a) The properties of the gross section shall be calculated from the specified size of the members;
(b) The properties of the effective cross section shall be calculated by deducting from the gross section area the following :
(i) The sectional areas of all holes in the section except that for parts in compression; and
(ii) If the projection of a plate or flange beyond its connection to a web or other support line exceeds the values, the excess flange area shall be neglected.
(i) Stiffened flanges shall include flanges composed of channels or I-section or of plates with continuously stiffened edges.
(ii) T1 denotes the thickness of flange or plate in compression.
(iii) Width of the outstand of members referred above shall be taken as follows :
(c) Where a plate is connected to other parts of a built-up member along lines generally parallel to its longitudinal axis, the width between any two adjacent lines of connections or supports shall not exceed the following :
For Plate in Uniform Compression
shall be assumed to be located centrally and its cross-sectional area shall be neglected.
For Plates in Uniform Tension (100 T1)
However, where the width exceeds 60 T1 the excess width shall be assumed to be located centrally and its cross-sectional area neglected.
(Here, T1 is taken to be the web/flange plate thickness of the member.)