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[GEN/Pushover]Reinforcing an Existing Building, But the Pushover Curve Shows Poor Performance


I conducted a Pushover analysis on both an existing building and a building with brace reinforcement, but it seems that the Capacity Curve is not coming out correctly, as shown in the following image. When does this happen?

[Image 1] Pushover Analysis Results of the Existing Building

[Image 2] Pushover Analysis Results of the Building with Brace Reinforcement



In the model you've inquired about, both models with and without braces are generating performance points after the structure's maximum yield force.

This is not an ideal situation. Performance points should be generated before the structure reaches its maximum yield force. In other words, they should intersect when the performance spectrum is in the rising phase with the demand spectrum.

To investigate this issue more thoroughly, it might be advisable to reduce the target displacement and increase the number of steps. Currently, there seems to be a portion with multiple members within one Y-direction brace. In such cases, the initial stiffness can be excessively large, causing the structure to reach its maximum yield force too easily.

For example, if a span is L, and it's divided into four members, setting the initial stiffness as 6EI/L (where EI is the flexural rigidity of the member) actually results in an initial stiffness of 24EI/L for each member because each member's length is L/4. Therefore, even a slight deformation can easily reach the maximum yield force of the designated members, leading to premature yielding.

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