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Three columns A, B, C, are collinear, 500 mm in diameter and spaced at 2.0 m center to center. They would carry vertical downward load of 1000, 550, and 700 kN respectively and are supported on a single 1.0 m deep rectangular combined footing. The soil beneath this proposed footing has the following properties: t = 19.5 kN/m3, c' = 10 kPa, and d' =31o. The ground water table is at a depth of 25 m below ground surface.
a. Determine the minimum footing length L, and the placement of the columns on the footing that will place the resultant load at the centroid of the footing. The footing must extend at least 500 mm beyond the edges of columns A and C.
b. Using the results from part a, determine the minimum footing width B that will maintain a factor of safety of 2.5 against bearing capacity failure. Show the final design in a sketch.
Hint: Assume a value of B, compute the allowable bearing capacity, then solve for B. Show at least 1 iteration with whatever assumed width irrespective of whether or not you get the desired Factor of safety.