Question

A six-storey office building consists of a basement, ground floor (1t floor), five upper floor levels (levels 2 through 6), and a roof. The typical layout of the floor system is shown below, in which each floor girder spans 6 m and floor joists span 4 m. The total plan area of the building is therefore 12 m x 8 m. The roofsystem is similar to the floor system. All of the floors support a uniformly distributed dead load of 2.1 kPa and live load for an office area according to the NBCC 2015. The basement level is a slab-on-grade and is not supported by the structure. The roof supports a dead load of 2.1 kPa and uniformly distributed snow load of 1.5 kPa. Calculate the factored axial force carried by the column in the centre of the building at the foundation level, considering an appropriate load case and live reduction factor. Neglect the self-weight of the column. load Column Floor slab Floor 6 m 6 m Page 2 of 2

Answer 1

ROOF LOADS Dead Load D = 2.1 kPa Live Load L_0 = 1.5 kPa Slope of roof F = 0 inches of rise per feet Method of Design: LRFD CALCULATIONS tributary area of structural member A_t = 6 times 4 = 24 m^2 reduction factor R_I = 0.936 As per ASCE7, R_1 = 1 for A_t < = 18.58 m^2 2 - 0.011A for 18.58 m^2 < At < 55.74 m^2 0.6 for A-t > = 55.74 m^2 R_2 = 1 As per ASCE7, R_2 = 1 for F < = 4 1.2 - 0.05F for 4 < F < 12 0.6 for F > = 12 reduced roof live load L_r = L_0 R_1 R where 0.58 < = Lr < = 0.96 = 1.404 kPa Axial load on column = 1.2 D + 1.6 Lr times A-t = 114.4 kN FLOOR LOADS Dead Load D = 2.1 kPa Live Load L_0 = 2 kPa