Design a combined footing supporting one exterior and one interior column.
An exterior column, 600 mm x 450 mm, with service loads of 760 kN (dead) and 580 kN (imposed) and an interior column, 600 mm x 600 mm, with service loads of 1110 kN (dead) and 890 kN (imposed) are to be supported on a rectangular footing that cannot protrude beyond the outer face of the exterior column. The columns are spaced at 5.5 m centres and positioned as shown in Figure 7.2.
The allowable bearing pressure is 175 kN/m2, and because of site constraints, the depth of the footing is limited to 750 mm.
22.214.171.124 Base size
Column A: 1340 kN and Column B: 2000 kN Distance to centroid of loads from LH end
2000 x 5.5 3340
For uniform distribution of load under base Length of base = 2 x 3.593 say 7.2 m With 750 mm deep base, resultant bearing pressure = 175 - 0.75 x 24 = 157 kN/m2
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