Question

A 12 ft cantilever beam 21 in. wide x 30 in, deep is reinforced by four # 8 bars as shown. Given fc 4000 psi and fy 60,000 psi. 3 in. is the cover to the center of the # 8 bar 21" #8 bars are spaced 5 in. center to center 33 @5 15"3" 3" 4 #8 #3 stirrups @6". O.С. Ж 27 30 #3 stirrups are 6 in. on center

1) Assuming Mcr = 125 k-ft, Ig = 47,250 in4 , Icr = 24,000 in3 , the moment of inertia for calculating a deflection corresponding to Ma = 200 k-ft, is most nearly:

A. 47,250 in4

B. 24, 000 in4

C. 30,000 in 4

D. 38,500 in 4

E. Other (specify) (g)

2) Assuming ΔD = 0.5 in.; ΔLL = 0.3 in., and ξ = 1.5, the total deflection of the beam is most nearly:

A. 0.8 in

B. 1.3 in

C. 0.95 in

D. 1.05 in

E. Insufficient information given

3) Cracking will not be a problem because:

A. # 8 bars are spaced at 5 in.

B. 3 in. cover is too large

C. 3 in. cover is too small

D. beam will not be visible to onlookers

Answer 1