ANS:B - 0.1 L from the centre edge of column

When extending top bars to the projecting parts of a combined footing of two columns L distance apart, the distance to which the bars should be extended depends on the structural requirements and design considerations. Typically, the bars are extended to ensure adequate reinforcement coverage and structural integrity. In this scenario, if we assume that the projecting parts of the combined footing are the areas outside the columns, then extending the top bars for a distance of:

• 0.1 L from the outer edge of the column would provide sufficient reinforcement coverage and structural support, ensuring that the bars adequately engage with the concrete in the projecting parts of the footing.

Extending the top bars to one-fourth or half the distance of projection might not provide enough reinforcement coverage and may compromise the structural performance of the combined footing. Therefore, the correct option is: 0.1 L from the outer edge of the column.