As of version 2024.d, users can carry out the linear buckling analysis. The linear buckling analysis allows the critical load factors and the buckling deformations of the structure to be determined for each analysed combination by solving an eigenvalue problem.
In order to carry out this analysis, the user's license must have the necessary permission for this module and for the "OpenSees analysis engine".
Before solving this problem, a static analysis of the defined combinations is carried out. The result of this analysis allows users to determine both the axial compression forces of each bar and the behaviour of the non-linear elements for each combination.
Once the buckling analysis has been carried out, a participation analysis is performed to determine the influence of a buckling mode on the bars in the structure. To obtain it, a participation percentage of 100% is assigned to the bar that absorbs the greatest deformation energy in that mode and, for the rest of the bars, it is calculated as the quotient between their deformation energy and that of the previously mentioned bar.
The options related to this new feature can be found in the new "Buckling analysis" menu.
Combinations for the buckling analysis
The stability of the structure must be analysed by load combinations. Just as for the non-linear analysis, the load combinations are defined based on the loadcases defined in the job data.
The program allows users to define the combinations to be analysed in three ways:
- By manually entering each combination.
- By automatically generating all possible combinations from the situations defined in the project.
- By analysing the results obtained from a linear analysis. In this case, the combinations in which the highest axial compression is produced are added to the bars of the structure depending on user-defined conditions.
Analysis
For the buckling analysis, users can define the number of buckling modes to be analysed and filter them by the maximum eigenvalue. The number of discretisation spans of the bars or the maximum length of each span can also be set.
For steel bars, users may indicate the minimum percentage of axial compression force below which a bar will not be included in the buckling analysis.
Assigning buckling coefficients
The program automatically analyses the buckling coefficients for each bar considered in the analysis. These coefficients can be assigned immediately after the buckling analysis, or by means of the "Assign buckling coefficients" option.
From the factors of both the critical load and the acting axial force, the program assigns the buckling coefficients. The participation analysis allows the buckling modes affecting each bar to be determined in order to analyse and assign the buckling coefficients.
Viewing the results
The buckling analysis results can be checked for each combination and buckling mode through the "Buckling modes" option. The program allows users to visualise both the deformation and the participation coefficient of each bar.
Buckling in bars
When defining the buckling data of a bar, users can indicate whether or not it will participate in the buckling analysis and, in case of updating the coefficients from the analysis results, which buckling coefficients will be updated.
Reports
The program allows the following reports to be generated:
- Buckling modes by analysis combination.
- Extended report of buckling modes for each bar.
- Summary report of the most influential buckling modes for each bar.
