A pushover analysis setting (PA) specifies the rules according to which the loading is increased and the iterative calculation of the target displacement ends. A standard analysis type is preset. You can adjust this type or create further pushover analysis settings at any time.
The "Pushover Analysis Settings" dialog box controls the settings of the analysis type selected in the "List" on the left.
Incrementally Increasing Loading
In this section, you can specify how the horizontal load is to be increased gradually.
Initial Load Factor
The value k0 represents the start factor. In general, the analysis starts with 1.0-fold lateral load. In EN 1998‑1, Eq. (B.1), for example, the initial load is described by the following relation:
| ¯Fi | Related horizontal force |
| mi | Mass of i-th story |
| Φi | Related displacement |
Load Factor Increment
The factor Δk specifies the increment by which the loading is increased during the analysis. The smaller the factor, the longer the calculation time. On the other hand, if the factor is too large, there is a risk that the target displacement is not determined with the required accuracy.
Refinement of Last Load Increment
This text box allows you to divide the critical area of the last load increment in finer load increments. Thus, you can perform a quick calculation with good result accuracy even for relatively rough factors Δk.
Maximal Number of Load Increments
The calculation ends as soon as the maximum number of load increments is reached. This way, you can prevent the analysis determining the pushover curve from running indefinitely or failing to reach converge due to oscillating effects.
Stopping Condition
In this section, you can define the target criteria of the calculation.
End of Capacity Curve
The capacity curve expresses the structure's ability to withstand lateral loads. There are two options in the list available as the target for the calculation of this curve.
- Limit deformation: The calculation ends as soon as a certain deformation is reached. You can enter this limit deformation udir manually in the text box to the right. It depends on the target displacement and thus on the seismic force (response spectrum). In many cases, you can apply 5% of the building height as a reference.
- Collapse: The horizontally acting loads are increased until a singularity occurs, thus causing the stability failure of the structure.
Automatic Selection of Highest Node
The check box is selected by default. Thus, the highest node in the building represents the control node for the limit deformation or for including the deformation in the capacity curve. By clearing the check box, you can specify another node in the model.
Options
The "Iterative procedure if difference between dm* and dt*" check box greater than ε' allows you to adjust the precision for the iterative determination of the target displacement dt*. This iterative procedure is referred to in EN 1998‑1, B.5; it corresponds to the N2 method according to [1]. Using the value ε, you can influence the allowable distance between two iterations as a break-off criterion, and thus increase the accuracy of the results.