Engineering Transactions, 61, 2, pp. 137–150, 2013

Elastic Stresses in Thin-Walled Torsional Structures Designed with SADSF Method

Ireneusz MARKIEWICZ
Kielce University of Technology

The paper presents general conclusions arising from FEM analyses of elastic properties
of thin-walled structures designed with the application version of the statically admissible
discontinuous stress fields (SADSF) method. The analyses have been carried out as a part
of a large-scale research program, whose main objective is conclusive verification of practical
usefulness of the SADSF method in design. The present state of development of the method’s
application software is so advanced that it allows one to design even very complicated thin-
walled structures composed of plane elements. This is a particular class of structures to which
the Saint Venant’s principle is not applicable [3, 4], and the methods based on consecutive
iterative improvements should be applied with due caution. In the SADSF method one does
not use iterations, and the method can be applied already at the stage when only boundary
conditions are known [3, 4]. Unfortunately, the method is an approximate one and does not
apply to the elastic range of stress that usually exists in exploitation conditions.
On the basis of analyses carried out for several dozen cases of thin-walled structures de-
signed with the SADSF method we can state, among other things, that in these structures there
are dominating membrane states, deformations remain small, equivalent stress fields are well
equalized also along free borders, stress concentrations are relatively low, and maximal levels
of equivalent stresses are approximately the same in all component elements. It has also been
proven that the structures designed with the SADSF method may have strength properties
even several dozen times better that those of structures designed traditionally. The obtained
conclusions are presented on the basis of three selected examples of original, which in this case
have open-section structures (see e.g. [11]) designed to carry torsional load [3, 4].
Keywords: design, thin-walled structures, limit load capacity, FEM analysis.
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