Combinations

The structural stability must be analysed using load combinations. The "Combinations" option allows you to define the combinations you wish to analyse.

As with non-linear analysis, load combinations are defined based on the loadcases specified in the "General data" section for the structure.

Clicking on the option opens the "Buckling combinations" window.

The program allows you to define the combinations to be analysed in three ways:

Entering combinations manually

Load combinations for buckling analysis can be added manually to the list on the left-hand side using the options on the top toolbar.

Each combination is defined as follows:

• The "Reference" is generated automatically based on the loadcases and combination factors defined below
• You can indicate whether the combination is '"Acting" or not by ticking the box in the next column
• and the number of "Load steps", the "Tolerance" value, the number of "Iterations" used in the analysis, and the number of "Reattempts" are defined.

Next, on the right-hand side, for each combination entered in the list, the "Combination factors" are defined by entering the value of the "Factor" for each "Loadcase" of the model selected from the drop-down menu.

Generating combinations based on the loadcases defined in the project

It is possible to define combinations for the buckling analysis by automatically generating all possible combinations based on the conditions defined in the project.

To do this, click the "Generate combinations for the different project situations" button at the top of the list of combinations. In the pop-up window, select the project loadcases from which you wish to retrieve the information, which include the following:

• Resistance (optional)
• Cracking (optional)
• Cracking under long-term loads (optional)
• Displacements (optional)
• Equilibrium of the foundation elements (optional)
• Bearing pressures in the soil (optional)

To apply the settings, click "Accept". The program will generate all combinations of the selected loadcases, automatically adding the necessary entries to the list and the corresponding combination factors.

Generating combinations based on the results of the linear analysis

If the structure has been analysed, you can use the "Generate combinations from the results of the linear analysis" option at the top of the combination list. This option automatically adds to the list those combinations in which the largest axial compression forces occur in the structural bars, depending on the conditions defined by the user in the pop-up window.

The program will therefore filter the structural combinations and add to the list those that contain compressed bars with axial forces greater than the "Percentage with respect to the maximum compressive axial force" found in other combinations, and with a "Minimum value of the compressive axial force" expressed in the defined units of force.

To apply the settings, click "Accept". Of all the combinations generated based on the defined loadcases, the program will retain those that meet these requirements, adding the entries to the list along with the corresponding combination factors for each loadcase.