Question

326 СНАРТER 6 BENDING EXAMPLE 6.18 The reinforced concrete beam has the cross-sectional area shown in Fig. 6-39a. If it is subjected to a bending moment of M = 60 kip ft determine the normal stress in each of the steel reinforcing rods and the maximum normal stress in the concrete. Take Est = 29(10) ksi and Econc = 3.6(103) ksi SOLUTION Since the beam is made of concrete, in the following analysis we will neglect its strength in supporting a tensile stress. 2[TT(0.5 in.)2 Section Properties. The total area of steel, Aşt = 1.571 in2, will be transformed into an equivalent area of concrete, Fig. 6-39b. Here 29(10) ksi 3.6(103) ksi 12 in. (1.571 in2) 12.65 in2 А' 3D ПА, = We require the centroid to lie on the neutral axis. Thus ỹA = 0,or 60 kip-ft 18 in. h' 12.65 in2(16 in. - h') = 0 2 12 in. (h') 1-in.-diameter bars in. h'2 +2.11h' - 33.7 = 0 (a)

Answer 1

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60X12 (16-4.04) 3.40 Ksi Conc 235 S Than the nomal stes n each Hhe hwo = n 6can 29Xlo3 3.6xlo3 る.40 21.38 Ksi 6st