Example 5.3: Design Example of a Rectangular Foundation for Column This section describes the design of a rectangular foundation to support a column having dimensions of 0.4 m x 0.4 m in cross section. Other details are as follows: Dead load D= 290 kN Live load L= 110 kN Depth from the ground surface to the top of the foundation = 1.2 m Allowable gross soil-bearing capacity = 120 kN/m² Maximum width of foundation = B = 1.5 m f, = 413.7 MN/m² f=20.68 MN/m² Unit weight of soil = y = 17.27 kN/m³ Unit weight of concrete = y₁ = 22.97 kN/m³ General Considerations For this design, let us assume a foundation thickness of 0.45 m (Figure A.4a). The weight of foundation/m² = 0.45 y = (0.45) (22.97) = 10.34 kN/m², and the weight of soil above the foundation/m² = (1.2)y = (1.2) (17.27) = 20.72 kN/m² Hence, the net allowable soil- bearing capacity Iqata] =120-10.34-20.72 = 88.94 kN/m² The required area of the foundation = (D+L)/4(all) = (290 + 110)/88.94 = 4.5 m². Hence, the length of the foundation is 4.5 m²/B = 4.5/1.5 = 3 m. The factored column load = 1.2D + 1.6L = 1.2(290) + 1.6(110) = 524 kN. The factored soil-bearing capacity, 4, = factored load/foundation area = 524/4.5 = 116.44 kN/m².
Example 5.3: Design Example of a Rectangular Foundation for Column This section describes the design of a rectangular foundation to support a column having dimensions of 0.4 m x 0.4 m in cross section. Other details are as follows: Dead load D= 290 kN Live load L= 110 kN Depth from the ground surface to the top of the foundation = 1.2 m Allowable gross soil-bearing capacity = 120 kN/m² Maximum width of foundation = B = 1.5 m f, = 413.7 MN/m² f=20.68 MN/m² Unit weight of soil = y = 17.27 kN/m³ Unit weight of concrete = y₁ = 22.97 kN/m³ General Considerations For this design, let us assume a foundation thickness of 0.45 m (Figure A.4a). The weight of foundation/m² = 0.45 y = (0.45) (22.97) = 10.34 kN/m², and the weight of soil above the foundation/m² = (1.2)y = (1.2) (17.27) = 20.72 kN/m² Hence, the net allowable soil- bearing capacity Iqata] =120-10.34-20.72 = 88.94 kN/m² The required area of the foundation = (D+L)/4(all) = (290 + 110)/88.94 = 4.5 m². Hence, the length of the foundation is 4.5 m²/B = 4.5/1.5 = 3 m. The factored column load = 1.2D + 1.6L = 1.2(290) + 1.6(110) = 524 kN. The factored soil-bearing capacity, 4, = factored load/foundation area = 524/4.5 = 116.44 kN/m².
Fundamentals of Geotechnical Engineering (MindTap Course List)
5th Edition
ISBN:9781305635180
Author:Braja M. Das, Nagaratnam Sivakugan
Publisher:Braja M. Das, Nagaratnam Sivakugan
Chapter17: Settlement Of Shallow Foundations
Section: Chapter Questions
Problem 17.6P
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