concrete models which are confined and unconfined concrete models.


Now, in this post, I am sharing with you a couple of concrete models which are confined and unconfined concrete models.

First of all why I am learning all these models? (you might be thinking)

I am working on the performance-based seismic evaluation of RC structures.

Having set an objective of carrying out Pushover analysis for evaluation of the capacity of structures, which requires defining the plastic hinge to perform the analysis.

Here the Plastic hinge characteristics are the Major role-playing element of the Pushover analysis.

Most of the time studies are carried out considering the default hinges generated in SAP2000, ETABS, or any software based on the ASCE 41/FEMA 356 criteria.

I have observed that SAP2000 uses Mander’s model for concrete.

On performing a couple of the analyses, I wasn’t able to converge the capacity of the structure that I had considered for the validation problem of my thesis.

Then I decided to go by user-defined hinges.

The user-defined hinge requires complete details of materials i.e. stress-strain graph of concrete and reinforcements, cross-sectional details with reinforcement dia., spacing of stirrups, clear cover, reinforcement grade, and all.

For user-defined hinge characteristics, the moment-curvature or moment-rotation can be calculated and can be provided as input for Pushover analysis. That is why the first and most important thing is to understand your basic material i.e. concrete and reinforcing steel.

Coming back to the point,

Here, I have attached the graph showing the comparison of concrete models as listed below.

◾IS Code (Unconfined) (IS 456:2000)

◾Hognestad (Unconfined) (1951)

◾Kent and Park (Unconfined) (1971)

◾Mander’s (Unconfined) (1988)

◾Kent and Park (Confined) (1971)

◾Modified kent and Park (Confined) (1982)

◾Mander’s (Confined) (1988)

Also, I have attached the cross-sectional detail which is considered in the preparation of the graph.

Considering the confining effects, Mander’s model shows a greater ductility and the same will be reflected in the capacity of a structure.

The unconfined strength of Mander’s model shows nearly the same strength as that of the Confined modified Kent and Park model.

I have carried out the study based on the Kent and Park model and have verified it with experimental studies for capacity evaluation.

I am looking to make a good comparison with Mander’s model, but have not come across detailed literature where the procedures can be verified.

Experts are requested to address their views and correct me.

Also, if you come across any kind of such comparative study then let me know which can be helpful to me for further process.

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