Question
How can I apply different yield effective stiffness to some elements?
Answer
To apply a different yield effective stiffness to columns or specific elements, you need to define additional sections.
The Seismic Perform > Demand > Generate Section Effective Stiff. function applies yield effective stiffness uniformly to all elements with defined sections when calculating the Moment-Curvature Curve.
To help you understand, let's take a look at an easy example.
The example model is a three-span bridge, as shown in the image below, with piers P1 and P2 having the same columns cross-section but different lengths.
Since it is an asymmetrical bridge, even if the column sections are the same, the yield effective stiffness will be different due to the difference in axial forces on each column. However, if seismic performance evaluation is not considered, there may be cases where the same section is applied to columns P1 and P2 for modeling convenience.
In this case, the Generate Section Effective Stiff. function is applied on a section basis as described earlier, so one yield effective stiffness is applied to both columns at once.
To perform accurate seismic performance evaluation, the yield effective stiffness obtained from each column must be applied, and to apply different yield effective stiffnesses, you need to define and assign sections to each column as shown in the image below.
The applied yield effective stiffness can be viewed in Properties > Section > Stiffness > Section Manager.
| Before Applying Yield Effective Stiffness | After Applying Yield Effective Stiffness |
If you want to define the yield effective stiffness for some specific elements, you can likewise define separate Sections and assign them to the required elements, calculate the yield effective stiffness using the Moment Curvature Curve, and apply the yield effective stiffness in bulk using the Generate Section Effective Stiffness function.