The reinforced concrete section shown at right is subjected to pure bending. Calculate; 725 a) The cracking moment and curvature (Mcr, Ocr). b) The moment and curvature when the concrete strain at the top fibre is Ecc=-0.5x10-3. c) The moment and curvature when the concrete strain at the top fibre is ecc=-1.0x10-3. d) The moment and curvature when the concrete strain at the top fibre is cc=-1.5x10-3. e) The moment and curvature when the concrete strain at the top fibre is Ecc= -2.0x10-3 f) The moment and curvature when the concrete strain at the top fibre is cc= -3.0x10-3. 3 - 0 26 75 350 mm fck= 35 MPa Eco = 0.002 fetk = 2.07 MPa Ec= 35000 MPa fy = 420 MPa Es= 200000 MPa 3-0 26 As= 1590 mm Note: Use equivalent rectangular stress block for concrete. Stress block factors for parabolic stress-strain curve Ece / ECO CI 0.25 0.336 0.682 0.50 0.595 0.700 0.75 0.779 0.722 1.00 0.889 0.750 1.25 0.928 0.786 1.50 0.900 0.833 1.75 0.810 0.900 2.00 0.667 1.000 B1 The reinforced concrete section shown at right is subjected to pure bending. Calculate; 725 a) The cracking moment and curvature (Mcr, Ocr). b) The moment and curvature when the concrete strain at the top fibre is Ecc=-0.5x10-3. c) The moment and curvature when the concrete strain at the top fibre is ecc=-1.0x10-3. d) The moment and curvature when the concrete strain at the top fibre is cc=-1.5x10-3. e) The moment and curvature when the concrete strain at the top fibre is Ecc= -2.0x10-3 f) The moment and curvature when the concrete strain at the top fibre is cc= -3.0x10-3. 3 - 0 26 75 350 mm fck= 35 MPa Eco = 0.002 fetk = 2.07 MPa Ec= 35000 MPa fy = 420 MPa Es= 200000 MPa 3-0 26 As= 1590 mm Note: Use equivalent rectangular stress block for concrete. Stress block factors for parabolic stress-strain curve Ece / ECO CI 0.25 0.336 0.682 0.50 0.595 0.700 0.75 0.779 0.722 1.00 0.889 0.750 1.25 0.928 0.786 1.50 0.900 0.833 1.75 0.810 0.900 2.00 0.667 1.000 B1