2. Key Structural Updates in ACI 318-19 Covered by PCA Notes
The design of post-tensioned and mild-reinforced two-way flat plates is extensively treated. The PCA Notes compare the Direct Design Method (DDM) and the Equivalent Frame Method (EFM). Crucially, the notes incorporate the updated ACI 318-19 provisions for punching shear calculations around column capitals, including the impact of eccentric moment transfer ( γfgamma sub f γvgamma sub v Serviceability and Deflection
The size effect factor for beams without shear reinforcement has been refined. The PCA Notes offer a side-by-side comparison of shear strength ( Vc ) calculations for members with and without axial load, including a new design flowchart to avoid common mistakes. pca notes on aci 31819
The PCA Notes provide clear threshold charts and design matrices. They show engineers exactly when the size effect factor applies and provide a comparative analysis of how much additional stirrup reinforcement is required compared to older code editions. 2. One-Way and Two-Way Slabs (Chapters 7, 8, & 22)
Because the code itself is written in legal language meant for adoption into local building regulations, it can be dense and difficult to interpret in daily engineering practice. The PCA Notes bridge this gap by translating complex code provisions into clear, practical design procedures, complete with explanations of the background logic and worked-out design examples. Key Changes Covered in the PCA Notes Crucially, the notes incorporate the updated ACI 318-19
) analysis. The PCA Notes provide extensive interaction diagrams that accommodate both standard steel grades and the newly approved Grade 100 reinforcement. Two-Way Slabs
| Code Feature | Key Changes in ACI 318-19 | | :--- | :--- | | | Introduction of provisions for high-strength reinforcement (e.g., Grade 690 (100 ksi) rebar) with new limitations for moment and axial force resistance from gravity and wind loads. Integration of minimum reinforcement requirements for different types and grades of rebar into a unified provision. | | Design & Analysis | Introduction of a new definition for the net tensile strain (εt) for non-prestressed members, enabling a more precise evaluation of safety and performance. This directly impacts the classification of sections as "tension-controlled," "compression-controlled," or "transition". | | Shear | Significant updates and consolidation of one-way shear and two-way shear (punching shear) equations into a single framework for greater consistency and simplicity. The new provisions aim to enhance member design efficiency, with some analyses suggesting increases in calculated concrete shear strength by up to 10%. | | Seismic Design | Updated and stricter seismic provisions for special and intermediate moment frames. This includes revised limits for longitudinal reinforcement ratios and hoop spacings, which are now determined by the rebar grade (e.g., smaller hoop spacing for Grade 550 rebar). | | Serviceability | A new equation for the effective moment of inertia (Ie) for cracked sections, aligning more closely with international standards like the Eurocode for more precise deflection calculations. | | Detailing | Introduction of new, specific provisions for hanger reinforcement to improve structural stability in special design conditions. Modifications to development length and splice provisions including new variables and factors for more detailed evaluation. | They show engineers exactly when the size effect
To see how these code changes affect a design, here is a simplified example calculation for minimum reinforcement in a beam, comparing ACI 318-14 with ACI 318-19.
Explanations of the intent behind new and revised code provisions.