
Figure 1
Static scheme of considered system.

Figure 2
Coordinate system and local basis vectors for nonprismatic thin-walled beam.

Figure 3
Description of displacements for cross section.

Figure 4
Analysed beams and dimensions of their cross sections.
Table 1
Eigenfrequencies in case of clamped-clamped support (C-C) [Hz].
| Mode number | Paper dim = 10 | Paper dim = 15 | Paper dim = 20 | FEM SOFiSTiK beam element 7DOF d = 20 | FEM SOFiSTiK beam element 7DOF d = 25 | FEM SOFiSTiK beam element 7DOF d = 50 | FEM Abaqus shell elements (quad) |
|---|---|---|---|---|---|---|---|
| 1 | 10.17 | 10.15 | 10.15 | 10.17 | 10.16 | 10.15 | 10.05 |
| 2 | 18.43 | 18.39 | 18.39 | 17.93 | 17.92 | 17.89 | 18.18 |
| 3 | 26.70 | 26.68 | 26.68 | 26.83 | 26.75 | 26.64 | 26.11 |
| 4 | 48.69 | 48.70 | 48.69 | 47.62 | 47.45 | 47.20 | 46.79 (lf) |
| 5 | 52.71 | 50.72 | 50.72 | 49.49 | 49.41 | 49.31 | 48.18 |
| 6 | 53.11 | 52.92 | 52.92 | 51.86 | 51.57 | 51.17 | 49.32 |
| 7 | 90.71 | 82.42 | 82.34 | 83.58 | 82.66 | 81.43 | 67.38 (lf) |
| 8 | 96.80 | 93.59 | 93.59 | 94.05 | 93.45 | 92.64 | 85.73 (lf) |
Table 2
Eigenfrequencies in case of clamped-free support (C-F) [Hz].
| Mode number | Paper dim = 10 | Paper dim = 15 | Paper dim = 20 | FEM SOFiSTiK beam element 7DOF d = 20 | FEM SOFiSTiK beam element 7DOF d = 25 | FEM SOFiSTiK beam element 7DOF d = 50 | FEM Abaqus shell elements (quad) |
|---|---|---|---|---|---|---|---|
| 1 | 2.20 | 2.19 | 2.20 | 2.15 | 2.15 | 2.15 | 2.19 |
| 2 | 8.33 | 7.68 | 7.60 | 7.68 | 7.69 | 7.69 | 7.55 |
| 3 | 13.44 | 12.96 | 12.91 | 12.26 | 12.25 | 12.24 | 12.77 |
| 4 | 14.42 | 13.88 | 13.85 | 13.66 | 13.67 | 13.68 | 13.77 |
| 5 | 24.31 | 23.18 | 23.13 | 23.97 | 23.95 | 23.93 | 22.75 |
| 6 | 35.95 | 32.68 | 32.54 | 31.07 | 31.00 | 30.90 | 30.89 |
| 7 | 44.18 | 50.31 | 50.21 | 52.13 | 51.91 | 51.60 | 48.68 lf) |
| 8 | 61.28 | 59.55 | 59.30 | 57.68 | 57.46 | 57.17 | 52.96 (lf) |