Vertical reinforcing is required at 32 in. on center along an 80 ft CMU wall, with a bar at each end. Each bar length including splice projection is 15 ft. What total reinforcing length is needed?
Correct Answer
B) 465 lf
The wall length is 80 x 12 = 960 in. Spaces at 32 in. give 960/32 = 30 spaces, so 31 bars are needed with bars at both ends. Total length is 31 x 15 = 465 lf. Other choices: 450 lf counts only 30 bars, 480 lf rounds the bar count upward incorrectly, and 405 lf uses a shorter bar length.
Why This Is the Correct Answer
The wall length is 80 x 12 = 960 in. Spaces at 32 in. give 960/32 = 30 spaces, so 31 bars are needed with bars at both ends. Total length is 31 x 15 = 465 lf.
Why the Other Options Are Wrong
Option A: 450 lf
vertical reinforcement, choice b: 450 lf backs into 15 when divided by 960/32; the accepted setup gives 15.5 on that same base.
Option C: 480 lf
vertical reinforcement, choice c: 32 x 15 gives 480 lf. That calculation follows multiplies those two listed numbers.
Option D: 405 lf
vertical reinforcement, choice d: 405 lf backs into 13.06 when divided by 31; the accepted setup gives 15 on that same base.
Memory Technique
Picture a checkpoint labeled vertical reinforcement: finish every operation before accepting 465 lf.
Reference Hint
Open Principles and Practices of Commercial Construction, 11th Ed., 2024; use the index entry or section for "Masonry reinforcing quantity takeoff" to confirm that The wall length is 80 x 12 = 960 in.
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