Definition of spans and buckling inputs



Quick and adequate understanding of how inputs influence results is crucial for the efficiency of engineering work, especially with large, sophisticated 3D models. SCIA Engineer v18.0 features a vastly improved definition of system lengths, buckling and deflection-related inputs, offering both graphical and tabular representation and an immediate access to results.

Users switching to SCIA Engineer v18.0 will find span and buckling inputs greatly simplified and easier to define and manage. As a result of consolidating all settings into fewer dialogues, a previously cumbersome part of using the programme has now become a unique competitive advantage over other software solutions on the market.

Instead of handling each 1D member in the structure separately, SCIA Engineer offers a deal of automation in detecting how all members in the structure interact with each other. In addition, customisation is simple and efficient: the user can easily adapt and accommodate special use cases from building or infrastructure design.

Simplification and a consolidation of all span, buckling and deflection-related inputs in one place is a great improvement in terms of usability and a valuable addition to existing functionality.

The user interface is now clearer: one changes buckling coefficients while looking at the structure and he/she gets a clear indication of the members to which changes apply to.

The resulting buckling lengths and factors are immediately shown in the input dialogue. There is no need to consult elsewhere.

The user does not input system lengths and buckling settings member by member: the concept of buckling groups makes it possible to manage the settings of many members at the same time.

Why spans are important

SCIA Engineer offers a wide range of code-based checks for various structural materials and world regions. In a majority of cases, checks on 1D members depend on span length: both ULS and SLS verifications, even CDD are influenced by the assumed length between restraints.

Spans in SCIA Engineer are determined automatically. Even so, engineering judgement sometimes dictates that spans be adapted to reflect the complexity of a 3D model: geometrical irregularity or special function of some of the members in the structure may influence the level of restraint certain parts of the structure provide to other parts of it.

Buckling and most serviceability verifications are influenced by span length more than anything else. Therefore, it is important that users be able to relate span definition to buckling- and deflection-related inputs in a clear and preferably graphical way.

In previous versions

Although SCIA Engineer was quite versatile and flexible when it came to system length and similar settings, the complexity of the user interface surrounding these settings made this part of the software widely unappreciated and rarely understood. What was meant to be a powerful feature was causing confusion, and both inexperienced and experienced users found buckling data difficult to define. Settings were scattered into many dialogues and it was not immediately clear what the hierarchy was between these dialogues.

The goals we, the SCIA development team, set for ourselves when we were preparing this development was:

  • to put all relevant span, buckling and deflection settings into one dialogue,
  • to make these settings clear and simple,
  • to favour graphical and tabular input as much as possible,
  • to not lose useful functionality in the process of simplification.

User involvement during the preparation helped us understand and focus on the basic, common cases and only then accommodate the advanced design scenarios.

How we improved the workflow

The new "System lengths and buckling settings" (SLBS) in SCIA Engineer are applied on "buckling groups" of 1D members. This means that the same set of settings can be applied to many members in the structure, and that settings for many members are edited at once.

Defining buckling groups is simple:

  • The user simply selects all 1D members who should share the same settings and open the SLBS dialogue via the 1D member properties.
  • A new set of settings is automatically created and will be saved if the user confirms his changes.
  • At any time, the user can change the buckling group the member belongs to.

Favouring graphical and tabular input

Editing the buckling groups is also quite simple:

  • The SLBS dialogue contains a fully functional graphical window, where all members that share the same settings are shown together. Dedicated view settings let the user control how the structure is displayed in the dialog, and a NaviCube replica makes viewing navigation simple.
  • Because one is looking at the structure while changing settings, it is immediately clear to which span(s) the changes apply to.
  • Lateral restraint can be activated or deactivated by clicking on an indicator inside the graphical part of the dialogue. The same is valid for sway settings.
  • All inputs that may differ per span are also available in tabular form. Tabular data can be copied to and pasted from spreadsheets.
  • Commonly used settings are separated from advanced settings to make the basics more findable.
  • The arrangement of settings inside the dialogue makes it clear what pertains to e.g., flexural buckling, to torsional buckling or to lateral-torsional buckling.

  • The resulting final buckling factors and lengths are shown directly in the dialogue: there is no need to navigate to another part of the software to control the results. After making changes, the user can refresh the buckling results and get up-to-date information per 1D member.

The SLBS dialog (and logic) is available for all materials and all codes supported in SCIA Engineer.

In addition, a list of all SLBS settings is provided in all material Services of SCIA Engineer. There, common settings for all buckling groups in the structure can be edited at once (e.g. point of load application, bow imperfections, etc.).

The final result

In SCIA Engineer, users do not have to work member by member when defining system lengths and buckling settings. The programme detects sequence of members that are continuously connected to each other. Such groups of members automatically share the same general settings. Similar sequences of members can be put into a buckling group to share the same settings.

Grouping is very flexible: the user can create unlimited number of buckling groups and customise his model to reflect any design situation.

SCIA Engineer also detects the 1D and 2D members that frame into the buckling group. It adds restraints accordingly; restraints are used in the determination of e.g., buckling lengths and factors and thus in code-based checks. Restraints can be disabled if the user finds that the framing member does not provide sufficient restraint.

The span and buckling settings are defined with a help of a fully functional graphical window, where the user can adjust view settings, use a Clipping Box, changes the view using a NaviCube and access viewing history.

Buckling factors and lengths are either calculated by the software or inputted by the user manually. In the case of calculation, the software solves additional load cases in the background during FEM calculation and derives the relative stiffness between members (in the buckling groups and their supporting elements). Regardless if factors are calculated or inputted, the final buckling factors and lengths can be reviewed directly in the Results tab of the RLBS dialogue.

Automation goes a step further to support more sophisticated use cases. An example are curved and cranked beams that are modelled as polylines: even in this case, one can still consider these as a single span. Examples for the application of this are portal frame girders in double-pitched roof halls and other beams that are not straight.


SCIA Engineer v18.0 provides a scalable solution for span and buckling settings: 

  • the user can be keep the model very simple, since automation will cover the common design cases;
  • in case settings need to be customised, flexible grouping combined with graphical UI makes editing simple.

Merging everything into one dialogue showed that in the end, system lengths and buckling settings can be organised in a simple and logical way that is not overwhelming. In fact, the sheer number of settings has decreased drastically and following a hierarchy between dialogues is no longer needed. We believe that this will improve understanding and errors in using the functionality will be prevented.