ANALYSIS AND DESIGN OF FOOTINGS | Square Footings скачать в хорошем качестве

ANALYSIS AND DESIGN OF FOOTINGS | Square Footings

Sample problems for square footings: PROBLEM 1. A 3 m x 3 m x 0.4 m footing with a 0.4 m x 0.4 m column at the center is loaded as shown in the figure. The base of the footing is 1.2 m below the ground. Unit weight is 24 kN/m3 for concrete and 18 kN/m3 for the soil above the footing. Use d = 315 mm for all calculations. At ultimate condition, U = 1.2D + 1.6L a) Determine the factored shear force (kN) at critical section for one-way shear. b) Calculate the nominal shear stress in the footing (MPa) at critical section for wide-beam action. c) Calculate the factored shear force (kN) at critical section for two-way shear. d) Calculate the nominal shear stress in the footing (MPa) at critical section for two-way action. PROBLEM 2. A 2.4 m x 2.4 m square footing supports a 350 mm x 400 mm column. Given data: Thickness of footing = 0.60 m Total factored axial load = 1818 kN Materials: Concrete, f’c = 20.7 MPa Steel, fy = 280 MPa (20 mm Ø bothways) Clear bar covering = 70 mm Strength reduction factors = 0.75 for shear = 0.90 for bending a) Calculate the shear stress in the footing (MPa) at critical section for wide-beam action. b) Calculate the shear stress in the footing (MPa) at critical section for two-way action. c) Determine the number of pieces of 20 mmØ reinforcing bars required in each direction of the footing.