Out-of-plane buckling and bracing requirement in double-angle trusses

다국어 초록 (Multilingual Abstract)

Truss members built-up with double angles back-to-back have monosymmetric cross-section

and twisting always accompanies flexion upon the onset of buckling about the axis of symmetry.

Approximate formulae for calculating the buckling capacity are presented in this paper for routine design

purpose. For a member susceptible only to flexural buckling, its optimal cross-section should consist of

slender plate elements so as to get larger radius of gyration. But, occurrence of twisting changes the situation

owing to the weakness of thin plates in resisting torsion. Criteria for limiting the leg slenderness are discussed

herein. Truss web members in compression are usually considered as hinged at both ends for out-of-plane

buckling. In case one (or both) end of member is not supported laterally by bracing member, its adjoining

members have to provide an elastic support of adequate stiffness in order not to underdesign the member. The

stiffness provided by either compression or tension chords in different cases is analyzed, and the effect of

initial crookedness of compression chord is taken into account. Formulae are presented to compute the

required stiffness of chord member and to determine the effective length factor for inadequately constrained

compressive diagonals.