28-Sheet Excel Engineering Toolkit for ACI 318-Based Strain Compatibility Analysis, Axial–Moment Interaction Curves, Reinforcement Forces, and Preliminary RC Column Section-Strength Assessment.

Explore reinforced concrete column behavior with a formula-driven Excel P–M interaction diagram generator.

This 28-sheet engineering toolkit calculates bar-by-bar reinforcement strains, steel stresses, concrete compression forces, nominal axial–moment resistance, and strength-reduced interaction curves for rectangular tied RC columns.

Includes 480 neutral-axis analysis states, 10 linked Excel charts, four uniaxial bending directions, a 12-page engineering guide, and calculation traceability.

Edition: Preliminary Engineering Prototype — for education, preliminary analysis, and independent engineering review. Not a complete or fully validated column design system.

Reinforced Concrete Column Interaction Diagram (P–M) Generator

Understand Column Strength. Explore Strain Compatibility. Visualize Axial–Moment Interaction.

Reinforced concrete columns resist combined axial forces and bending moments. Their sectional strength depends on concrete dimensions, longitudinal reinforcement, material properties, neutral-axis depth, and the distribution of compression and tension across the section.

The Reinforced Concrete Column Interaction Diagram (P–M) Generator is a formula-driven Microsoft Excel engineering toolkit designed to help civil and structural engineers study, calculate, visualize, and review rectangular tied reinforced concrete column section behavior.

Built around selected ACI 318-19(22) calculation principles, the workbook connects geometric inputs, reinforcing bar coordinates, material properties, neutral-axis analysis, concrete compression, reinforcing steel forces, and axial–moment interaction diagrams.

Unlike a static diagram or simplified chart, the workbook includes visible intermediate formulas to help users follow the underlying strain compatibility calculations.

What's Inside?

1. Dynamic RC Column Section Analysis

Define rectangular or square concrete sections and explore the effects of changing section dimensions, concrete compressive strength, reinforcing steel properties, and longitudinal reinforcement positions.

The workbook supports up to 40 individually defined longitudinal reinforcing bars, including asymmetric arrangements.

2. Four Uniaxial P–M Interaction Branches

Explore separately calculated interaction relationships for:

• Positive bending about the X-axis

• Negative bending about the X-axis

• Positive bending about the Y-axis

• Negative bending about the Y-axis

The model uses 120 neutral-axis states per compression face, providing 480 calculated states across the four bending directions.

3. Transparent Strain Compatibility Calculations

Follow engineering calculations covering:

• Neutral-axis depth and compression-block geometry

• Linear strain distribution

• Individual reinforcing bar strains

• Steel stress and yielding limits

• Concrete compressive resultant

• Displaced concrete adjustments

• Steel axial forces and moment contributions

• Nominal axial resistance and bending moment

• Strength reduction factors

• Design interaction coordinates

The calculation trace allows users to inspect individual reinforcing bar contributions at selected analysis states.

4. Excel-Based Engineering Charts

Explore 10 native, formula-linked Excel charts covering interaction relationships, reinforcement geometry, selected steel stress distributions, strain-control behavior, and preliminary reinforcement comparisons.

These charts are connected to calculation data rather than being standalone static illustrations.

5. Factored Load Screening

Enter axial forces and bending moments to explore preliminary uniaxial demand-to-capacity relationships.

Simultaneous biaxial bending is identified as requiring separate analysis. Section-strength screening does not replace slenderness, second-order analysis, stability, detailing, or complete member design.

6. Reinforcement Alternatives and Sensitivity Studies

Review 20 preliminary reinforcement alternatives and 18 sensitivity scenarios to examine selected input changes and axial compression reference results.

These comparison modules do not generate fully independent alternative P–M curves or validate optimized column designs.

7. Calculation Trace, QA and Reporting

The workbook includes engineering calculation traceability, input checks, project information, reference records, a preliminary reporting sheet, and warnings about applications outside the modeled scope.

8. Supporting Engineering Guide

A 12-page PDF explains the fundamental mechanics, key calculation assumptions, a worked metric section example, numerical reference checks, spreadsheet workflow, and major design limitations.

Package Contents

Excel Engineering Workbook (.xlsx)

28 connected worksheets with engineering inputs, visible formulas, calculation tables, interaction charts, preliminary load screening, and reporting features.

Engineering Guide (.pdf)

12-page reference document describing the calculation approach, worked example, numerical checks, and engineering limitations.

README (.md)

Quick-start instructions, units, sign conventions, model limitations, references, and usage information.

Complete ZIP Package (.zip)

All three product files in one convenient download.

Who Is This For?

• Civil and structural engineers

• Reinforced concrete designers

• Structural engineering consultants

• Structural engineering educators

• Graduate engineers working under supervision

• Advanced civil engineering students

• Engineering professionals studying interaction diagrams

• Technical reviewers examining preliminary section-strength calculations

Technical Specifications

Important Engineering Limitations

This release is a preliminary engineering calculation prototype, not a fully validated professional design application.

Its limitations include incomplete exact compression-cap boundary construction, interpolated spreadsheet pure-bending points, incomplete reinforcement detailing checks, and preliminary rather than complete alternative-section interaction analysis.

The workbook has not been independently validated as a complete production design system. ACI 318-25 calculation mode, biaxial interaction, column slenderness, second-order effects, full seismic detailing, shear, and complete column design are outside the implemented scope.

Users must verify the adopted governing code, input values, numerical results, structural analysis demands, and complete structural adequacy independently before any professional design application.

An acceptable preliminary P–M section-strength result does not establish that a column is safe, code-compliant, or approved for construction.

Publisher

Published by Sarchawa — https://sarchawa.com

Created by Mohammed A. Omer, civil and structural engineer and technical author.

Sarchawa is a publishing website operated by Mohammed A. Omer, providing professional learning resources, technical tools, and practical digital products.

Copyright © 2026 Mohammed A. Omer. Published by Sarchawa (sarchawa.com). All rights reserved.

Key Features 

• 28 INTERCONNECTED EXCEL WORKSHEETS

• 480 NEUTRAL-AXIS ANALYSIS STATES

• FOUR UNIAXIAL P–M BENDING DIRECTIONS

• 40 INDIVIDUAL REINFORCEMENT BAR INPUTS

• BAR-BY-BAR STRAIN AND STRESS CALCULATIONS

• CONCRETE COMPRESSION & STEEL FORCE ANALYSIS

• 10 DYNAMIC EXCEL CHARTS

• ACI 318-19(22)-BASED CALCULATION FRAMEWORK

• PRELIMINARY LOAD INTERACTION SCREENING

• 12-PAGE PDF ENGINEERING GUIDE

• VISIBLE ENGINEERING FORMULAS & CALCULATION TRACE

• EDUCATIONAL & PRELIMINARY SECTION-STRENGTH TOOL

Product FAQ

Q: Is this a complete reinforced concrete column design program?

No. It is a preliminary rectangular tied-column section-strength calculation prototype. Complete column design requires additional engineering checks and independent verification.

Q: Which ACI edition is used?

The implemented calculation framework uses selected ACI 318-19(22) provisions. ACI 318-25 calculation mode is not implemented.

Q: Can I modify the concrete dimensions and reinforcement?

Yes. The workbook includes editable section inputs, material properties, and individual reinforcing bar coordinate records.

Q: Does it generate positive and negative bending interaction curves?

Yes. It calculates separate positive and negative uniaxial interaction branches about the X and Y axes.

Q: Does it support biaxial column design?

No. Simultaneous biaxial loading requires a separately validated biaxial analysis.

Q: Can I use the workbook for construction design approval?

No. The current release has documented validation limitations and is not certified for construction design approval. All results require independent review by an appropriately qualified structural engineer.

Q: What software do I need?

A desktop Microsoft Excel version capable of recalculating workbook formulas is recommended. Chart and formula behavior in other spreadsheet software has not been verified.

Q: Is the engineering guide included?

Yes. The package includes a 12-page PDF guide, a README, and the XLSX workbook.

Q: Can I resell or redistribute the files?

No. The included license permits personal study and internal professional workflows, but not redistribution, resale, rebranding, or sublicensing without permission.

PERSONAL & INTERNAL PROFESSIONAL USE LICENSE

This digital product is published by Sarchawa and authored by Mohammed A. Omer.

Purchasers may use the included files for personal education, technical study, and internal professional engineering workflows.

Redistribution, resale, public sharing, rebranding, and sublicensing of the original files are not permitted without authorization.

Third-party technical standards, references, trademarks, examples, and other protected intellectual property remain the property of their respective owners. Inclusion of technical references does not imply endorsement or certification.

ENGINEERING DISCLAIMER

This product is an educational and preliminary structural engineering calculation prototype. It does not replace qualified professional engineering judgment, independently validated design software, applicable building codes, or complete structural analysis and design.

The purchaser is responsible for independent verification of input data, numerical results, governing code requirements, structural adequacy, and any project-specific application.

ABOUT SARCHAWA

Sarchawa (sarchawa.com) is the publishing website operated by Mohammed A. Omer, offering practical professional resources, technical tools, and digital products.

ABOUT THE AUTHOR

Mohammed A. Omer is a civil and structural engineer and technical author developing practical engineering education resources, calculation workflows, and professional digital tools.

Copyright © 2026 Mohammed A. Omer. Published by Sarchawa (sarchawa.com). All rights reserved.