Answer: A. 0.0035(1-d'/xu)
For a rectangular section having effective cover to compression steel as d' and neutral axis depth from compression face as xu, the strain at the level of compression steel is given by- 0.0035(1-d'/xu).
Using a representation of the strain distribution in doubly reinforced beams,
Strain at the level of compression steel is given by Εsc.
0.0035/xu = Εsc/(xu- d')
Εsc =0.0035/xu (xu-d')
The distance of compression steel from the extreme compression fibre of concrete is given by d’.
Concrete's outermost fiber's maximum compressive strain is estimated to be 0.0035.
At the ultimate limit state, the maximum strain in tension reinforcement at the level of the reinforcement steel's centroid shall not be less than Εst= 0.87fy/Es+0.002.
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