Form Finding for Bowstring Beam

This is a bowstring beam model in Dlubal RFEM, the span is 14m, the height is 3m

the cross section of top chord is a pipe (D=250mm, t=25mm),
the cross section of vertical bar is a pipe (D=120mm, t=6mm),
the bottom string is a circular section with D=25mm.

The top chord has 20kN/m load, while the bottom strings are prestressed.
The equilibrem state is define by there is no (very small) vertical displacments under the above loads.

The key to the form-finding is to set the relative length of string to 100%, because there is no vertical displacement, the stressed length of the strings should be the same as that in the model.

The vertical displament of the equilibrem state is below, the max displacement is only 1.2mm


How to achieve it in Sofistik?


I think this should be possible with the optimisation workflow in CSM. You have to fix the vertical displacement and factorise the two cables (four → two due to symmetry).
Please have a look at the following TEDDY examples.

TEDDY > File > Examples > csm > english > optimize > …

The basic information about the CSM optimisation workflow can be found in the CSM manual.

SSD / TEDDY > Help > User Manuals > All Manuals… > CSM > chapter 2.10 Shape and Force Optimization

Best regards
Frederik Höller
Your SOFiSTiK Support Team

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