Pca Notes On Aci 31819 -
PCA Notes on ACI 318-19: The Structural Engineer’s Ultimate Companion
3. Development and Splicing (Chapter 25)
The development length equations ($l_d$) were recalibrated to account for the new reinforcement grades.
- Calibration for Grade 100: The development length formulas now include terms that adequately scale for $f_y = 100,000$ psi. This prevents excessively long lap splices that would render Grade 100 bars impractical.
- Confined Sections: There is increased clarity on reduction factors for development length in confined sections (e.g., within spirally reinforced columns). The reduction factors are more conservative for high-strength bars to mitigate splitting failures.
5. Flexural Design (Reinforced & Prestressed)
- Ultimate strength: Use phi factors per limit states (flexure, shear, axial).
- Balanced vs. under-reinforced sections: Ensure tension-controlled sections for ductility unless special provisions apply.
- Development length: Provide development and splice lengths per Chapter 25; consider bar size, concrete strength, confinement, coating (epoxy reduces bond, increasing ld).
- Serviceability: Limit crack widths and deflections; satisfy service-load criteria and long-term effects (creep, shrinkage).
About the Author & Further Reading
This article synthesizes guidance from practicing structural engineers, the Portland Cement Association, and ACI Committee 318. For deeper study:
- ACI 318-19 Building Code Requirements for Structural Concrete (ACI)
- ACI 318-19 Commentary (ACI 318R-19)
- PCA Notes on ACI 318-19 – Example Problem List (available free on PCA’s website)
- CRSI Design Manual – for bar detailing and splicing
Final word: A concrete structure is only as reliable as the engineer’s interpretation of the code. The PCA Notes ensures that interpretation is accurate, efficient, and defensible. pca notes on aci 31819
3. Complete Rewrite of Shear Provisions (Chapter 22)
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.
Top 5 Most-Referenced Sections in the PCA Notes on ACI 318-19
Based on usage surveys among structural engineering firms, the following sections of the PCA Notes are opened most frequently: PCA Notes on ACI 318-19: The Structural Engineer’s
5.1 Development Length ( l_d ) (Chapter 25)
- Basic equation: [ l_d = \frac340 \fracf_y\lambda \sqrtf'c \psi_t \psi_e \psi_s \fracd_bc_b + Ktr ]
- PCA Notes provides simplified tables for ( l_d ) for common bar sizes and concrete strengths.
2. Worked Design Examples (The Goldmine)
This is where the PCA Notes shines. There are over 100 detailed examples, including:
- Reinforced concrete beam design (rectangular, T-section, doubly reinforced)
- Short and slender column interaction diagrams (using both ACI strain compatibility and approximate methods)
- Two-way slab design (direct design method vs. equivalent frame method)
- Shear friction for corbels and brackets
- Anchorage to concrete per ACI 318-19 Appendix D (now Chapter 17)
- Strut-and-tie models for deep beams and dapped ends
Each example follows a rigid four-step format: Calibration for Grade 100: The development length formulas
- Given data
- Code reference
- Design procedure (step-by-step)
- Final sketches
5. Specific Changes in ACI 318-19 vs. Older PCA Notes
If you are using older PCA Notes (e.g., ACI 318-14 or 318-11) with the new code, stop. There are significant changes in 318-19 that render older aids inaccurate.
Major updates in 318-19 reflected in the current PCA Notes:
- Shear Friction ($V_n$): The upper limit for shear friction capacity was modified. Old notes will give wrong capacities.
- Deep Beam Design: Strut-and-Tie modeling guidelines were refined.
- Anchoring to Concrete (Ch 17): breakout strength calculations for headed studs changed slightly regarding edge distances and concrete type.
- Shear in Slabs: Changes to the detailing of shear reinforcement (stirrups) in two-way slabs.
- Derating Factors: New load factors for specific loading conditions.