FRP ACI 440.2R-17 existing substrate strain

[wayne_dwops]

Hoping to reach out to the fiber reinforced polymer guys. I am checking the work of an engineer who designed a CFRP reinforcement on a precast concrete beam. I am rolling through the documentation in ACI 440.2R and I am hung up on item 10.2.3, "existing substrate strain". I am directed to determine this strain via an elastic analysis using cracked section properties. I've done hand calcs for beam deflection using cracked section properties plenty of times but I am unsure how that translates to obtaining my strain in concrete. What elastic analysis is the code referring to?

Assuming I have calculated my effective moment of inertia correctly, I would hope it is as simple as using a variation of Mc/I to get my service level stresses and then strain through my concrete modulus of elasticity, That being said, I have only ever calculated c when my strain in concrete is known (0.003).

Thank you in advance.


Edit: I found my answer fairly quickly, at service loads the depth of the neutral axis is calculated as kd. I should have known...