Critical combined loading for flexture column

The design value of an action effect in each cross-section should not exceed the corresponding resistance and if several action effects act simultaneously, the combined effect should not exceed the resistance for that combination. The level of axial load at which a section becomes Class 2 is not required because the same section properties (the gross area and plastic modulus) are used in the resistance calculations for both Class 1 and Class 2 sections.Д¬lass 4 cross sections are not considered in this article. SCI P363 gives axial load ratios where (under increasing levels of axial load) a section becomes Class 3 and Class 4. Section classification is also given in resistance tables, such as SCI P363 (the ' Blue Book' ). The class of the cross section is determined from Table 5.2 of BS EN, where a cross section is classified according to the highest (least favourable) class of its parts subject to compression. Class 4 cross-sections are those in which local buckling will occur before the attainment of yield stress in one or more parts of the cross-section.Class 3 cross-sections are those in which the stress in the extreme compression fibre of the steel member assuming an elastic distribution of stresses can reach the yield strength, but local buckling prevents development of the plastic moment resistance.Class 2 cross-sections are those which can develop their plastic moment resistance, but which have limited rotation capacity because of local buckling.Class 1 cross-sections are those which can form a plastic hinge with the rotation capacity required for plastic analysis without reduction of the resistance.ДЇour classes of cross-sections of are defined in BS EN : The values are those given in the UK National Annex to BS EN. Resistance of cross-sections in tension to fracture: Оі M2В =В 1.10.Resistance of members to instability: Оі M1В =В 1.00 (used in buckling resistance).Resistance of cross-section: Оі M0В =В 1.00.

The partial factors Оі M that are applied to the various characteristic values of resistance in member design are: 4.3 Uniform members in bending and axial compression.4.2.2 Reduction factor for lateral torsional buckling of rolled sections.4.2.1 Lateral torsional buckling resistance.

Critical combined loading for flexture column