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[GEN/Pushover]Pause Analysis(THE YIELDING OCCURRED IN THE INELASTIC HINGE BY INITIAL LOADING)

Question

After auto-designing the rebar with Concrete Design and checking OK for all members, the pushover analysis was performed.
At this point, the following warning message was displayed: "THE YIELDING OCCURRED IN THE INELASTIC HINGE BY INITIAL LOADING".

If all member designs are OK, it means that they have been designed considering all load combinations. Can yielding occur due to initial loading? Initial Loading is set as 1.0DL+0.25LL. Can it yield against gravity loads?

 

Answer

In a reinforced concrete member, there are two yields, Crack and Yield, when the Pushover Hinge Property type is used as Trilinear. In this case, the caution message above will be displayed when the Crack moment is exceeded.

If the initial design is done correctly, there should be no problem with the analysis. Since the message does not distinguish between yielding due to Crack and Yield, to determine the cause of yielding, you need to check the Crack moment of the specific member.

[Image-1] Characteristics of plastic hinge using Multi-Linear Hinge Type

You should also check whether the message you mentioned is only displayed for certain members or if it is widely displayed for major members. If it is displayed extensively for major members, you need to examine the overall trend of yielding using the Hinge Status in post-processing.

The model you mentioned is a super high-rise building with over 70 floors, and P-Delta effects are considered in the Pushover analysis. In super high-rise buildings, when considering P-Delta effects, lower-level columns can experience excessive compression, leading to abnormal stiffness of those members.

This is because the final stiffness of a member is the sum of its intrinsic stiffness and geometric stiffness (Final Stiffness = Intrinsic Stiffness + Geometric Stiffness), and geometric stiffness reduces the overall stiffness when the member experiences compressive forces.

If you performed Pushover analysis without considering P-Delta effects and obtained normal results, the cause can be attributed to P-Delta effects.

 

Question

During Pushover analysis, the message "THE YIELDING OCCURRED IN THE INELASTIC HINGE BY INITIAL LOADING" appears, and the Pushover analysis stops.

 

Answer

There can be various reasons why Pushover analysis is not performed, and corresponding solutions

If the yield moment set in the hinge dialog is smaller than the moment due to the initial load, the member may yield under initial loading. If many such yielding members exist in your model, Pushover analysis may not be meaningful. In such cases, it's advisable to start by determining NG/O.K for members in elastic analysis.

[Image-2] Properties

[Image-3] Forces

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