
Figure 1
Coordinate system and local basis vectors for a nonprismatic thin-walled beam.
Source: Author’s contribution.

Figure 2
Description of displacements for the cross-section.
Source: Author’s contribution.

Figure 3
Cross-section at beam’s midspan .
Source: Author’s contribution.
Table 1
Critical load values when the load acts on the centre of the upper flange.
| 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | S w 1) | |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.0 | 14.77 | 15.72 | 16.76 | 17.88 | 19.10 | 20.43 | 21.90 | 23.58 | 25.50 | 1.73 |
| 14.77 | 15.72 | 16.71 | 17.73 | 18.79 | 19.90 | 21.05 | 22.24 | 23.47 | ||
| 0.1 | 15.75 | 16.72 | ||||||||
| 15.74 | 16.79 | 17.79 | 18.94 | 20.21 | 21.60 | 23.15 | 24.91 | 26.92 | 1.71 | |
| 0.2 | 16.67 | 18.73 | ||||||||
| 16.67 | 17.66 | 18.97 | 19.91 | 21.20 | 22.63 | 24.23 | 26.04 | 28.07 | 1.68 | |
| 0.3 | 17.55 | 20.78 | ||||||||
| 17.54 | 18.53 | 19.60 | 21.31 | 22.08 | 23.53 | 25.15 | 26.96 | 28.97 | 1.65 | |
| 0.4 | 18.38 | 22.86 | ||||||||
| 18.34 | 19.34 | 20.39 | 21.56 | 23.78 | 24.29 | 25.89 | 27.66 | 29.60 | 1.61 | |
| 0.5 | 19.18 | 24.93 | ||||||||
| 19.05 | 20.12 | 21.15 | 22.29 | 23.54 | 26.31 | 26.46 | 28.14 | 29.99 | 1.56 | |
| 0.6 | 20.03 | 26.91 | ||||||||
| 19.67 | 20.93 | 21.92 | 23.00 | 24.19 | 25.49 | 28.79 | 28.47 | 30.21 | 1.51 | |
| 0.7 | 20.99 | 28.94 | ||||||||
| 20.14 | 21.84 | 22.75 | 23.75 | 24.85 | 26.04 | 27.34 | 31.04 | 30.43 | 1.45 | |
| 0.8 | 22.04 | 30.72 | ||||||||
| 20.43 | 22.81 | 23.65 | 24.56 | 25.57 | 26.67 | 27.89 | 29.26 | 32.79 | 1.39 | |
| S f 2) | 1.49 | 1.45 | 1.41 | 1.37 | 1.34 | 1.31 | 1.27 | 1.24 | 1.20 | 2.08 3) |
Source: Author’s contribution.
1) 2) 3)
Table 2
Critical load values when the load acts on the centre of the web.
| 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | S w | |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.0 | 24.35 | 25.40 | 26.46 | 27.53 | 28.60 | 29.69 | 30.82 | 32.06 | 33.57 | 1.38 |
| 24.36 | 25.39 | 26.40 | 27.38 | 28.35 | 29.30 | 30.23 | 31.15 | 32.06 | ||
| 0.1 | 26.59 | 27.66 | 28.74 | 29.82 | 30.92 | 32.03 | 33.19 | 34.47 | 36.04 | 1.36 |
| 26.57 | 27.69 | |||||||||
| 0.2 | 28.66 | 29.73 | 30.80 | 31.88 | 32.98 | 34.10 | 35.27 | 36.56 | 38.12 | 1.33 |
| 28.64 | 31.00 | |||||||||
| 0.3 | 30.54 | 31.59 | 32.64 | 33.70 | 34.78 | 35.88 | 37.02 | 38.28 | 39.81 | 1.30 |
| 30.52 | 34.22 | |||||||||
| 0.4 | 32.21 | 33.21 | 34.21 | 35.22 | 36.25 | 37.29 | 38.39 | 39.59 | 41.04 | 1.27 |
| 32.18 | 37.25 | |||||||||
| 0.5 | 33.64 | 34.56 | 35.49 | 36.43 | 37.37 | 38.34 | 39.35 | 40.47 | 41.85 | 1.24 |
| 33.56 | 39.97 | |||||||||
| 0.6 | 34.87 | 35.71 | 36.55 | 37.39 | 38.23 | 39.11 | 40.02 | 41.07 | 42.36 | 1.21 |
| 34.58 | 42.21 | |||||||||
| 0.7 | 36.10 | 36.84 | 37.57 | 38.31 | 39.06 | 39.84 | 40.67 | 41.59 | 42.83 | 1.19 |
| 35.16 | 43.73 | |||||||||
| 0.8 | 37.50 | 38.15 | 38.79 | 39.43 | 40.09 | 40.78 | 41.53 | 42.41 | 43.30 | 1.15 |
| 35.16 | 44.18 | |||||||||
| S f | 1.54 | 1.50 | 1.47 | 1.43 | 1.40 | 1.37 | 1.35 | 1.32 | 1.29 | 1.78 |
Source: Author’s contribution.
Table 3
Critical load values when the load acts on the centre of the lower flange.
| 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | S w | |
|---|---|---|---|---|---|---|---|---|---|---|
| 0.0 | 33.07 | 34.29 | 35.46 | 36.58 | 37.66 | 38.68 | 39.69 | 40.74 | 42.09 | |
| 33.18 | 34.36 | 35.48 | 36.54 | 37.54 | 38.47 | 39.35 | 40.16 | 40.91 | 1.27 | |
| 0.1 | 36.87 | 38.11 | ||||||||
| 36.85 | 38.11 | 39.28 | 40.39 | 41.45 | 42.45 | 43.42 | 44.47 | 45.87 | 1.24 | |
| 0.2 | 40.42 | 42.78 | ||||||||
| 40.37 | 41.64 | 42.92 | 43.85 | 44.87 | 45.82 | 46.76 | 47.79 | 49.17 | 1.22 | |
| 0.3 | 43.69 | 46.99 | ||||||||
| 43.67 | 44.87 | 45.96 | 47.44 | 47.94 | 48.84 | 49.71 | 50.68 | 52.01 | 1.19 | |
| 0.4 | 46.66 | 50.57 | ||||||||
| 46.65 | 47.76 | 48.78 | 49.71 | 51.49 | 51.36 | 52.12 | 53.00 | 54.24 | 1.16 | |
| 0.5 | 49.24 | 53.30 | ||||||||
| 49.22 | 50.23 | 51.13 | 51.93 | 52.65 | 54.85 | 53.93 | 54.70 | 55.84 | 1.13 | |
| 0.6 | 51.42 | 55.28 | ||||||||
| 51.25 | 52.28 | 53.03 | 53.68 | 54.25 | 54.76 | 57.26 | 55.98 | 57.03 | 1.11 | |
| 0.7 | 53.34 | 56.93 | ||||||||
| 52.58 | 54.05 | 54.65 | 55.17 | 55.61 | 56.02 | 56.47 | 58.36 | 58.09 | 1.09 | |
| 0.8 | 55.21 | 58.84 | ||||||||
| 52.96 | 55.77 | 56.24 | 56.63 | 56.96 | 57.28 | 57.66 | 58.23 | 57.69 | 1.07 | |
| S f | 1.67 | 1.63 | 1.59 | 1.55 | 1.51 | 1.48 | 1.45 | 1.43 | 1.40 | 1.78 |
Source: Author’s contribution.

Figure 4
Relationship between the critical load value and taper coefficients for “admissible” systems of type W(m), F(n), W-F(k) when load acts on the (a) upper flange, (b) web centre, and (c) lower flange.
Source: Author’s contribution.

Figure 5
Relationship between the critical load value and taper coefficients for “admissible” systems Wind–Find when the load acts on the (a) upper flange, (b) web centre, and (c) lower flange. Diagrams for a set of discrete values and diagrams for discrete values continuous approximation are shown in top and bottom figures, respectively.
Source: Author’s contribution.