Howlyn2
Structural
- Mar 10, 2020
- 26
Hello All, I have recently come across an unknown modified Whitney Stress Block formula for Over-Reinforced Concrete where "a" is modified to: rho,m - sqrt(rho,m^2+4*rho,m)/-2 * d* Beta,1 and rho,m = (Es*0.003) / (0.85 * f'c * Beta,1) * As / (b*d). The "a" value calculated above is then inserted into the traditional Whitney Stress Block moment equation. I believe that the over reinforced beam is being derated to insure the tensile reinforcement controls over concrete crushing to prevent brittle failure. I believe that the quadratic equation is being used to find the actual area of concrete in compression instead of rectangular areas as allowed by code. I am looking to better understand this reduction in moment capacity, but I am having a hard time finding the origin to fully comprehend the derivation. Has anyone ever run across this type of equation modifier before?
