Answer Happy

Problem 1. The column cross section shown in Fig. 1 is cast with fé = 4,000 ps and reinforced with steel of fx = 60,000 psl. The total amount of reinforcement, As = 11.32 in?, comprised of 2 No. 11 + 2 No. 10 at each end of the section. The reinforcement ratio, Ast/A, = 0.03 or p = 0.03. h = 20" Th= 15" AI - 4 No. 11 + 4 No. 10 b = 18" OOOO 3 No. 4 tie Bending axis
E-4-60-0.75 40 76 - 4 ksi yh elh 0.1 1/2 = 50 ks 3.5 P0.05 y 0.75 : leih 0.2 Epg-0.04 3.0 Po 0,03 0.3 2.5 Pg 0.02 ksi Pe -0.01 Tel. 051 15 0.51 10 Comp. Cont. Limit Tons. Cont. umit- 0.5 0 0.2 0.4 0.6 12 14 1.6 0.8 CM ksi bh? Fig. A-60 Noodimensional interaction diagram for rectangular tied columns with bars in two faces fa 4000 psi and YH075 clearer version of the interaction diagram, refer to fin
Problem 1 (cont'd). Determine the following for the column cross section: (a) (10 points) What is nearly the maximum tie spacing (in.) allowed for No. 4 ties, per AC1318. Shear does not govern. (b) (10 points) Determine the maximum allowed service moments for dead and live (i.e., M, and M) of the column, if the following axial forces are present: Po = 152 k P2 = 228 k Mo = ?? k-ft M=?? k-ft Note that the live-to-dead load ratio of 1.5 is to be maintained (e.g., Pa/Po = 1.5) (c) (10 points) Determine the maximum required axial force (P) and moment (M.) that can be carried by the column if an eccentricity of 7-in is present. (d) (10 points) Check the adequacy of the column under P. = 750 k and M. = 288 k-ft. (e) (10 points) If the column is subjected to concentric loads, determine the maximum required axial force (P.) and moment (M) that it can be carried. (f) (10 points) If the column acts like a beam (.e., pure bending condition), determine the maximum required axial force (P) and moment (M) that it can be carried. (8) (10 points) Explain/define/describe the balanced"condition in the context of reinforced concrete. Determine the maximum required axial force (P.) and moment (M.) that can be carried by the column under the "balanced condition. (h) (10 points) Re-do or re-calculate P, and M, for part (e) for the column, however, instead of being reinforced with 4 No. 11+4 No. 10, the column is being reinforced with a total amount of 6 No. 11 + 6 No. 5 rebars (or 3 No. 11 + 3 No. 5, each end).