Check lines - a unique feature inTekla Structural Designer - provide a practical way to automate deflection checking and reduce the possibility of errors.
Each check line defines a line along which deflection checks are required. Multiple check lines can be created and each line can have several different deflection checks performed (against either a total, instantaneous, or differential deflection limit).
Whilst the check lines have to initially be positioned using engineering judgment, once they are in place they provide an instantaneous means to evaluate revised deflections following changes to the model parameters and re-analysis.
Assessing slab deflections without check lines would be quite an arduous task, since deflection limits are of the form (span / fixed value) and the spans can vary on an irregular slab, hence the permissible limit would also vary. Furthermore, you may wish to check total or differential deflections at or between different load events. Would the critical location be obvious?
Setting up the checks in advance (via the slab deflection check catalogue)
The deflection checks to be performed for the check lines are set up in the Slab Deflection Check Catalogue before the check lines are positioned.
Each check in the catalogue is specified as a Total, Differential or Instantaneous deflection limit that is checked for a specified event, (or in the case of a Differential check between the start of an event and the end of an event).
Related task Create the deflection checks to be applied to check lines
Application of check lines
The application of check lines is an iterative activity. They should be created at all locations where you deem deflection checks to be required.
Check lines can only be created in a 2D view. If the Create command is greyed out ensure you switch to a 2D view.
When you click Create, the Properties Window automatically includes those slab deflection checks from the Slab Deflection Check Catalogue where "Use in new Check Lines" was checked. Note that a maximum of six checks can be assigned to a single check line; if you require more than six checks, then multiple check lines can be applied at the same location.
You can add further checks from the catalogue or add new checks directly from the Properties Window.
You can also edit the "Use in New Check Lines" option in the catalogue prior to running the Create command to change the default checks automatically assigned to each new check line.
Related task Create a check line
Displaying check line results
The Check Line deflection can be overlayed on the slab by using the Deflections command in the ribbon, it is perhaps easier to visualize if you switch the view to a 3D view of the slab using the 2D/3D toggle button in the bottom right of the window.
You can also right click on a check line and open the deflections check view. This displays a cut line through the slab, showing the deflected shape with the maximum and minimum deflection values. Beneath this it also draws the average slopes between maximum and minimum points and reports the average slope ratios.
The above deflection check view is controlled from the Loading Analysis ribbon which has droplists to enable you choose the Result Type (Total, Instantaneous, or Differential) and the Event(s).
The average slope ratios (for the appropriate result type/event) are checked against the deflection limits that have requested for the check line.
Doing the checks this way inherently deals with offset peak deflections (non-uniform load) and also cantilevers.
Related task Display check line results
Check line reports
A tabulated report is available for each check line which itemizes each requested deflection check along the check line.
You can generate a check line report for an individual check line by right clicking the check line and selecting Member Report.
You can also generate a Slab deflection check line report for the entire structure, selected level, planes or sub structures via the Model Report command on the Report ribbon.
Related task View slab deflection reports