Question

A 9 m tall atrium is to be constructed in a commercial development. You are required to check the ability of a Grade 300 310UC96.8 to be used as one of the corner columns. The factored ultimate axial load, N* , is 1100 kN. This load includes the factored self-weight of the member. The column is pinned at both ends about the major and minor axes such that the buckling length is 9,000 mm (9 m). The column is also subjected to a factored moment about the x axis, M*x of 50 kN.m. Finally, the ultimate moment about the minor axis, M*y is 15 kN.m. All moments are applied at the top of the column. The bending moment at the base of the column is zero. Use the following steps to check the suitability of this section to carry this combination of loads. Data for the 310UC96.8 are given below. (a) Determine the nominal section capacities for compression, φNs and φNc. Compare these capacities to N*. (b) Assuming that the column subject to major axis bending is laterally unrestrained, find the nominal bending capacity φMb about the x axis of the section. The supports provide full lateral restraint. Check the 310UC96.8 section against the combination of axial load and moment about the x axis for both in-plane and out of plane behaviour. (b) Considering the minor axis ultimate moment of 15 kN.m at the top of the member about the y axis, check if the 310UC96.8 member is capable of supporting this biaxial bending and axial load combination. Comment on your answer. Hint: Use clause 8.4.5.1 or some other suitable method. Section data for 310UC96.8, using the usual notation: d = 308 mm, bf = 305 mm, tf = 15.4 mm, tw = 9.9 mm, d1 = 277.2 mm, d1/tw = 28.0, (bf-tw)/2tf = 9.58, Ag = 12400 mm2 , Ix = 223x106 mm4 , rx = 134 mm, Zx = 1450x103 mm3 , Sx = 1600x103 mm3 , Iy = 72.9x106 mm4 , Zy = 478x103 mm3 , Sy = 725x103 mm3 , ry = 76.7 mm, J = 928x103 mm4 , Iw = 1560x109 mm6