When can the live load be calculated by multiplying height, width and length of a pour and dividing by the deadload?

When can the live load be calculated by multiplying height, width and length of a pour and dividing by the deadload?

• A. Never
• B. Always
• C. Only for rigid slabs
• D. Only with superimposed load

Answer: (A)

Live load isn’t derived from the size of the pour. The volume of concrete poured (height × width × length) gives how much material you placed, which is related to dead load (the weight of fixed materials). But live load represents variable, occupancy- or use-dependent forces (people, furniture, equipment) specified by code and applied per unit area (psf or kPa). Dividing a poured volume by a dead-load value doesn’t produce a meaningful live-load figure, either dimensionally or physically, so there’s no situation where this method makes sense. Live load is determined by occupancy and code-referenced design values, not by geometry of the pour. That’s why the correct answer is that this method should never be used.

Live load isn’t derived from the size of the pour. The volume of concrete poured (height × width × length) gives how much material you placed, which is related to dead load (the weight of fixed materials). But live load represents variable, occupancy- or use-dependent forces (people, furniture, equipment) specified by code and applied per unit area (psf or kPa). Dividing a poured volume by a dead-load value doesn’t produce a meaningful live-load figure, either dimensionally or physically, so there’s no situation where this method makes sense. Live load is determined by occupancy and code-referenced design values, not by geometry of the pour.

That’s why the correct answer is that this method should never be used.