Secondary Moments in Post-Tensioned Concrete Design Technical Article Featured

For further knowledge on utilizing secondary moments in the design of post-tensioned concrete one can read a recent technical article in the PTI Journal by Jonathan Hirsch, Software Development Manager at Bentley Systems.

Initially, understanding the meaning and usage of secondary moments is a fundamental aspect of designing post-tensioned concrete and is considered a rite of passage for engineers in this field. There is an abundance of information available on how to calculate and apply secondary moments. However, many engineers use a traditional approach to design post-tensioned members, which is code-compliant, accurate and safe. This article aims to provide a comprehensive understanding of the origin, effectiveness, and limitations of this approach emphasizing on alternative approaches for designing post-tensioned members.

The introduction section establishes the use of secondary effects in post-tensioning. The subsequent sections cover several aspects, including the following six. A short description is presented and the respective section titles are acknowledged:   

1. Calculation of the flexural strength capacity of concrete members, which is crucial to ensure adequate resistance to demand loads. (Section title: Ensuring Flexural Strength Capacity of Concrete Members)
2. Examination of the ACI 318-19 Section 22.2.1.3 prescribed method for determining the post-tensioned flexural strength capacity through secondary forces. (Section title: Post-tensioned Flexural Strength Capacity – ACI Secondary Force Approach)
3. Consideration of the new equilibrium solution that highlights the significance of internal compression strains and stresses generated from tendon stressing in post-tensioned cross sections. (Section title: Post-tensioned Flexural Strength Capacity – New Equilibrium Solution)
4. Exploration of a recommended secondary force approach that aligns with the ACI 318's intent and the new equilibrium approach, suitable for use in design. (Section title: Recommended Secondary Force Approach)
5. Introduction of a straightforward method to compute secondary forces for cross-sections with both post-tensioning and non-prestressed reinforcement. This method eliminates ambiguity in the ACI definitions for secondary forces and maintains consistency with the ACI definitions. (Section title: Cross Sections with both Post-tensioning and Non-prestressed Reinforcement)
6. Comparison between the numerical manipulation of the new equilibrium behavior and the recommended secondary effects approach. (Section title: Difference between New Equilibrium and Recommended Secondary Force Approach) 

Here is the link for access to the PTI Journal article courtesy of Post-Tensioning Institute.

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