Tiêu đề PSAD 40 - RCD - Footings.pdf ✅

PSAD 40: RCD - Footings Video Transcript Problem 1. A 350 mm thick footing is to support a 300 mm thick wall carrying a service DL of 145 kN/m and service LL of 180 kN/m. The base of the footing is 1.5 m below the ground surface. Unit weight of soil = 18.9 kN/m3, Unit weight of concrete = 24 kN/m3. fc ′ =21 MPa, fy = 420 MPa. The allowable soil bearing pressure is 240 kPa. 1. What is the required width of the footing? 2. What is the required spacing (mm) of 16-mm bars to be used as flexural reinforcement? Solution: A footing supporting a wall, or any longitudinal member is a continuous or strip footing. These types are designed by considering a 1-m strip section. The dimensions of a footing are based on the allowable bearing pressure of the soil, qall = qeff + γshs + γchc + qs For the effective soil pressure, 240 = qeff + 18.9(1.15) + 24(0.35) + 0 qeff = 209.865 kPa For the dimension of the footing, qeff = Pservice Afooting 209.865 = (⏞145 + 180 ) kN/m (⏞1) m B (⏞1) m B = 1.549 m, say 1. 55 m When the thickness of a footing is yet to be designed, the dimension of the footing cannot be concluded until it satisfies both allowable soil pressure and the shear strength of concrete. However, since the thickness is already given as 350 mm in the problem, the footing width is set to be 1.55 m.