What is the maximum allowable deflection for a scaffold plank spanning 8 feet under normal loading conditions?
Correct Answer
C) 1/60 of the span
OSHA requires scaffold planks to have a deflection not exceeding 1/60 of the span. For an 8-foot span, this equals approximately 1.6 inches maximum deflection.
Why This Is the Correct Answer
OSHA 29 CFR 1926.451(a)(1)(ii) specifically states that scaffold planks must not deflect more than 1/60 of the span under normal loading conditions. This is a critical safety requirement to ensure scaffold stability and worker safety. The 1/60 ratio is more lenient than typical structural deflection limits because scaffolds are temporary structures, but still provides adequate safety margins. For an 8-foot span, this translates to a maximum allowable deflection of 1.6 inches.
Why the Other Options Are Wrong
Option A: 1/120 of the span
1/240 of the span is extremely restrictive (0.4 inches for 8 feet) and is not required by OSHA for scaffold planks. This level of deflection control would be unnecessarily expensive and impractical for temporary scaffold construction.
Option B: 1/240 of the span
1/120 of the span is too restrictive for scaffold planks and is not the OSHA requirement. This ratio (0.8 inches for 8 feet) would be more typical for permanent structural members where deflection control is more critical for aesthetics and function.
Memory Technique
Remember 'Sixty Scaffold Safety' - the number 60 is the key denominator for scaffold plank deflection limits, and it's the smallest (most lenient) deflection ratio compared to permanent structures.
Reference Hint
OSHA 29 CFR 1926 Subpart L - Scaffolds, specifically section 1926.451(a)(1)(ii) for scaffold plank deflection requirements
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