Is as access floor required to be grounded? In an office building, carpeted tiles. Power under floor in raceway. Non-stringered flooring spec'd (tiles screwed down at each corner) and ground straps at corner.
250.4 (A)(3) and (4) required that normally non-current carrying conductive material enclosing electrical conductors....be connected … ground-fault current path. Or likely to become energized also be grounded (paraphrased).
Is the intent to required access floor be grounded?
First, this is a raised floor, carpet on top, just posts and no stringers, but has ground straps? All power is in condluit and there's listed floor boxes? Article 645 for Information Technology Equipment may apply. The definition of IT equipment is anything that is not communications (also defined) and with the two definitions, could make a great debate. If 645.15 applies, and posts are metal, grounding is a requirement. What does the installation information say, especially about the ground straps? Are the floor boxes part of the system and listed?
The short answer is nothing I know of in the code requires a raised floor to be grounded but there are reasons for grounding a raised floor. Here are a couple them: Tempest with a raised floor require a low impedance equipotential grounding system. Chip manufacturing requires its raised floors to be grounded to mitigate static charges with a flat or braided conductor. Each of us has between 4000 to 35000volts of static charge in us all the time . Electronic testing facilities with raised floor requires a low impedance equipotential grounding system and grounding stations for the workers. Radio broadcasting stations, data centers and similar places require raised floor grounding. Highly explosive chemical mixing stations require equipotential grounding.
To answer, we should first know what you have there. "Access floors" isn't a term that is used in NEC [2017].
Do you mean Article 372? 374? A raised floor in an IT room?