Why does the effective width of composite beams not calculate automatically when the decking is parallel?
Environment
British Standard
Eurocode
Example Issue
Take the example below, where the beams are parallel to each other but have different beam lengths. What effective width should be taken in the area where the width of the slab tapers?
Image
Tekla Structural Designer is able to calculate the effective width, provided the beams are parallel, or thereabouts, and of similar lengths.
You can control this tolerance on rectilinearity via the Design ribbon tab > Options > Composite Beams.
The default value is 15 degrees (90-67.34 in the example above) and if this is exceeded, the program will not calculate the effective width automatically.
Image
Since it is outside the limits, no suggestion will be offered and the Calculate button will not calculate a value.
A tooltip is not provided since the maximum value is unknown. This is because the span/8 or half the width to the next beam each side will vary along the length of the beam. The effective width must therefore be controlled by yourself.
Image
If the tolerance falls within the value set via the Design ribbon tab > Options > Composite Beams, then the Calculate button will work.
In instances where the width cannot be automatically calculated, you can manually calculate the desired width and input it via the Properties dialog box.
Below is a screenshot of the procedure for a single beam.
Image
The same procedure will work for multiple beams selected at once.
This can also be achieved by Right-clicking on the beam member > Edit > Floor Construction > Effective Width for a single beam only.