It is possible to calculate the effect of the vortex shedding on the column according to Clause 22.10 of EN13445-3. In NextGen, for vertical items, the user can find the properties related to vortex shedding under the "Wind" tab of the "Item properties" window. The structural analysis must be abilitated in order for the user to be able to perform the vortex shedding calculations.
"Wind" tab of the "Item Properties" window
Clause 22.10.2 describes a screening procedure necessary for determining whether the vortex shedding calculation is requested. The user can activate this calculation by clicking on "Perform vortex shedding screening". This procedure is performed for every load combination in which wind is present.
Clause 22.10.3 and clause 22.10.4 describe the calculation procedure necessary for determining the shear force and the bending moment generated by the vortex shedding at a given height. The user can activate this calculation by clicking on "Perform vortex shedding calculation (if required)". This calculation will be performed only for load combinations where this procedure is necessary, i.e where the screening procedure determined that the vortex shedding calculation is necessary.
The "averaged outside diameter of the upper third of the column including insulation" and the "equivalent mass per unit length over the upper third of the height of the column" are automatically calculated by the sofware for all load combinations and are used both on the screening procedure and on the calculation procedure. The user can overwrite these values on an item level (i.e. for all load combinations) by clicking on the padlock icon.
The final output of both procedures will be printed on the report as subsections of the "Wind Profile calculation".
From the "Validation results" table in the "Vortex shedding screening" section the user can see for which load combinations a calculation is necessary:
Screening validation results
The user can see the calculation performed for load combinations where the screening procedure determined the calculation is necessary under "Vortex shedding calculation". For instance, for load combination LC2:
Vortex shedding calculation for load combination "LC2"
The final result of the calculation is a table containing shear force and bending moment values generated by the vortex shedding at the lowest point of each component. The user can use these values to perform the fatigue analysis requested by Clause 22.10.5 (according to Clause 18).