Page 502 - Aircraft Stuctures for Engineering Student

11.5 Constraint of open section beams 483

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B t---l

(a) 100rnrn
Fig. 11.41 Column of Example 11.3.

Example 11.3
The column shown in Fig. 11.41(a) carries a vertical load of 100kN. Calculate the
angle of twist at the top of the column and the distribution of direct stress at its
base. E = 200 000 N/mm2 and GIE = 0.36.

The centre of twist R of the column cross-section coincides with its shear centre at
the mid-point of the web 23. The distribution of 2AR is obtained by the method
detailed in Example 11.2 and is shown in Fig. 11.42. The torsion bending constant
rR is given by Eq. (ii) of Example 11.2 and has the value 2.08 x 10'omm6. The
St. Venant torsion constant J = Cst3/3 = 0.17 x 105mm4 so that d m (= ,LL
in Eq. (iii) of Example 11.2) = 0.54 x Since no torque is applied to the

Fig. 11.42 Distribution of area 2AR in the column of Example 11.3.