Learn more about using secondary moments in designing post-tensioned concrete. Read the recently published technical article in PTI Journal.
Understanding the meaning and usage of secondary moments is key in designing post-tensioned concrete, and many engineers follow a traditional approach which can result in code-compliant and safe designs. Read this article for a deeper understanding of where this traditional approach came from, take a look at why and when it works, and see how it is only one approach for designing post-tensioned members, when in fact, there may be yet another perspective to consider.
After setting the stage for post-tensioning and the clarification of using secondary effects in the introduction, following sections include a look at:
Ensuring Flexural Strength Capacity of Concrete Members
The flexural strength capacity of concrete members must be calculated to ensure that they have adequate strength to resist the applied demand loads.
Post-tensioned Flexural Strength Capacity – ACI Secondary Force Approach
Take a look at how ACI 318-19 Section 220.127.116.11 prescribes the effective method.
Post-tensioned Flexural Strength Capacity – New Equilibrium Solution
A significant portion of the strength of post-tensioned cross sections is a function of the internal compression strains and stresses generated from stressing the strands.
Recommended Secondary Force Approach
Explore a secondary force approach that is both consistent with the new equilibrium approach and the intent of ACI 318, and is therefore suitable for use in design.
Cross Sections with both Post-tensioning and Non-prestressed Reinforcement
This section provides a straightforward method to calculate secondary forces, which takes the ambiguity out of the ACI definitions for secondary forces, is consistent with the ACI definitions, and is generally applicable.
Difference between New Equilibrium and Recommended Secondary Force Approach
See how the difference between the new equilibrium behavior and the recommended secondary effects approach is simply a numerical manipulation.