Question

Question 1: Determine the tensile straight development length required for the 20 mm uncoated bottom bars shown below: a. assume Ktr 0 b. Use computed value of Kur Use fe 20 MPa, fy 420 MPa. Consider side and bottom concrete cover 40 mm and diameter of stirrups 10 mm. ф10@250mm 300 mm

Answer 1

dia = 20 mm uncoated a) k_tr = 0 b) Computed value of k_tr cover = 40 mm, dia of stings = 10 mm For clear distance 6/n bas. 300 - (2 times 40 + 2 times 10) = 200 mm 200 - (4 times 20) = 120 mm Therefore Clea distance = 120/3 = 40 mm l_2 = f_y/1.1 timed d times squareroot fc times psi_E psi_e psi_s times ds/(C_b + ktr/d_b) squareroot E = 1, psi_e = 1, psi_s = 0.9, lambda = 1 ACI 318 m = 11 12.2.3 12.2.4 lambda_d = 420/1.1 times squareroot 20 times 0.9/(C_b + k_tr)/d_b times d_b = 76.64 d_b/((b + k_tr)/d_b C_b (i) 40 mm (ii) 50 mm (iii) 60/2 = 30 mm Minimum C_b = 30 mm. a) For K_tr = 0 L_d = (76.84/30 times 20) times d_b = 51.23 mm times 20 L_d = 1024.533 mm b) K_tr = 40 times 2 times pi/4 times 10^2/4 times 250 = 0 .628 C_b + K_tr/d_b =