In the October 2025 SEU session, Kimberly Kramer, PhD, PE, from Kansas State University, presented Navigating the ACI 318-19(22) Code: Practical Implications for Structural Engineers.  Kimberly described how ACI 318-19(22) can be used for shear design, two-way slab provisions, anchoring to concrete, and basic seismic detailing of special structural walls.  She noted the technical rationale behind the code and its broader impact on structural safety, resilience, and constructability.

During the session, Kimberly highlighted the equation for the development length of deformed bars.  As you can see in the slide below, Equation 25.4.2.4(a) includes the Reinforcement grade factor 𝝍g, which was first introduced into the code in the ACI 319-19. Research has shown that higher grades of steel reinforcement require an increased development length. Also, a minimum transverse reinforcement must be provided when the yield strength is greater than 80,000 psi and must be spaced closer than 6 inches on center.  The transverse reinforcement aims to reduce the possibility of a splitting failure due to the higher yield stresses in the longitudinal reinforcement.  

All other variables of Eq. 25.4.2.4(a) are the same as in past versions of ACI 318.  As you can see in the slide below, these variables include factors for yield strength, concrete strength and type, as well as bar size, location, and spacing factors.

The addition of the Reinforcement Grade Factor, along with the minimum transverse reinforcement for fy > 80,000 psi, aims to rectify unconservative estimates for the development length of deformed bars when using higher grades of steel.  ACI 318-19(22) has noted the results of research for higher grades of reinforcing steel, and using these new values for the reinforcement grade factor 𝝍g, the development length of bars may increase upwards of 50% or more.  Thus, engineers should be aware of the implications of using higher grades of steel and the resulting increase in the development length for deformed bars.