How to setup a steel SLS check?
In order to perform a steel SLS check, the following data needs to be specified:
- The span of the elements to be checked
- The deflection limits of the elements to be checked
- The camber attributed to the elements (optional)
The span, deflection limits and camber values can be all input via the buckling setting dialogue, which can be accessed via the properties dialogue of an element (figure 1).
HOW TO SET THE ELEMENTS SPAN?
The spans of 1D elements (beams, columns) can be set (independently for local Z and Y directions) via the buckling setting dialogue as highlighted in figure 2:
To set the span independently for the local Y and Z directions, one needs to select defz=defz and defy=defy.
However, the dialogue also allows you to specify that the deflection in one direction is based on another deflection/buckling setup already entered. For instance, when selecting defz=yy, it means that the setup for the deflection in the Z direction will be the same as the setup for the yy buckling. If, on the other hand, you select defz=defy then the setup for the deflection in the Z direction will be the same as the setup for the deflection in the Y direction (defy).
If you select for instance defz=defz, deflection supports can be enabled/disabled (dotted triangle means a disabled support) by clicking on the red triangles in the graphical window (figure 2, green arrow). The same result can be achieved by ticking/unticking the check boxes in the “Active buckling constraint” section of the dialogue (figure 2). The deflection supports can be set (enabled/disabled) only in elements’ nodes.
HOW TO SET THE DEFLECTION LIMITS?
The deflection limits can be set in the “span settings” part of the dialogue, figure 3. The deflection limits can be set independently for the local Y and Z directions (based on the active deflection option, defy or defz, see paragraph above), and independently for total loads and variable loads.
Three options are available:
- For all spans: the same deflection limits will apply to all the spans of the selected element(s), figure 4
- Per span: different deflection limits will apply to different spans, figure 5
- From setup: the deflection limits specified in the steel setup will apply to all the spans, figure 6
Note that a span is defined as the distance between two active deflection supports (solid line triangles, figure 4). If you want to define a continuous span for a selected element, then all the intermediate deflection supports must be disabled, see for instance figure 11.
HOW TO SET THE CAMBER?
The camber can be set independently for the local Z and Y direction (based on the active deflection option, defy or defz, see paragraph about the span setup) via the combo box highlighted in green in figure 7:
Four options are available:
- No camber: no camber will be applied
- Input camber (absolute): the camber value will be input, span by span, in absolute dimensions (length units), figure 8
- Input camber (relative): the camber value will be input, span by span, as a relative coordinate (1/length units)
- From setup: the camber values specified in the steel setup will be applied to all spans (figure 9).
NOTE: The camber is defined with respect to the local z axis. If the local z axis is directed downward, you have to input a negative value in order to have an upward camber.
COMING SOON: Starting from SCIA 19.1 also a camber AutoDesign option will be available!
HOW TO VISUALIZE THE DEFINED CAMBER?
The specified camber can be visualized via the SLS check menu. Figure 10 shows the camber input as shown on figure 11. Note that one continuous span has been defined for the selected beam (solid line triangles only at the element ends).
HOW TO CORRECTLY SET THE SPAN FOR A CANTILEVER BEAM?
In order to obtain correct results, cantilever condition should be specified in the buckling settings by disabling all span supports except the support at one of the beam ends. For instance, the results given in figure 12 are obtained for the setup given in figure 13. Note how the cantilever condition is correctly specified using the span definition (one support enabled, solid triangle). If such a setup is not respected, for instance span supports are kept active at both ends (figure 14), the deflection is not correctly computed for the cantilever element (figure 15).