If W is total load per unit area on a panel, D is the diameter of the column head, L is the span in two directions, then the sum of the maximum positive bending moment and average of the negative bending moment for the design of the span of a square flat slab, should not be less than A. $$\frac{{{\text{WL}}}}{{12}}{\left( {{\text{L}} – \frac{{2{\text{D}}}}{3}} \right)^2}$$ B. $$\frac{{{\text{WL}}}}{{10}}{\left( {{\text{L}} + \frac{{2{\text{D}}}}{3}} \right)^2}$$ C. $$\frac{{{\text{WL}}}}{{10}}{\left( {{\text{L}} – \frac{{2{\text{D}}}}{3}} \right)^2}$$ D. $$\frac{{{\text{WL}}}}{{12}}{\left( {{\text{L}} – \frac{{\text{D}}}{3}} \right)^2}$$

The correct answer is: $$\frac{{{\text{WL}}}}{{12}}{\left( {{\text{L}} – \frac{{2{\text{D}}}}{3}} \right)^2}$$

The maximum positive bending moment and average of the negative bending moment for the design of the span of a square flat slab can be calculated using the following formula:

$$M = \frac{{{\text{WL}}}}{{12}}{\left( {{\text{L}} – \frac{{2{\text{D}}}}{3}} \right)^2}$$

where:

• $M$ is the bending moment
• $W$ is the total load per unit area on a panel
• $D$ is the diameter of the column head
• $L$ is the span in two directions

The formula takes into account the following factors:

• The total load per unit area on the panel
• The diameter of the column head
• The span in two directions

The formula ensures that the slab is designed to withstand the maximum bending moment that it is likely to experience.

Option A is incorrect because it does not take into account the diameter of the column head.

Option B is incorrect because it does not take into account the span in two directions.

Option C is incorrect because it does not take into account the maximum bending moment.