Local stress fields in cylindrical space truss members having radial end tabs

Includes bibliographical references (page 199)Members of space truss systems that are efficiently designed have an allowable load that is based on a primary failure mode such as long-column buckling. Local effects at the ends of the members should not be critical.\ud A common truss member design is that of a thin-walled cylindrical tube with welded radially oriented tabs for bolted connection at the ends. In a typical truss arrangement these members are subjected to not only pure axial loading, but secondary transverse loading between\ud the tabs. Local stress concentrations occur that may not only determine the allowable load on the member but may effect its overall stiffness.\ud Using Nastran, a finite element structural analysis program, a computer model was developed to analyze such a member subjected to unit axial and transverse loads. The model was designed so as to allow for analysis of different tab orientations. Detailed plots of local stress fields and displacements show load distribution and areas of high stress concentration. Maximum stresses, stress concentration factors, and effective member stiffness considering end effects are presented for several common cylinder sizes. Published formulas, adapted to predict maximum local cylinder stresses and deflections, show reasonable agreement with model results. Allowable loads are presented which are conservatively based on initiation of yielding at local stress\ud concentrations. These allowables, which range from 30% to 45% of the tension-only allowables set forth by AISC specifications are compared with results of tests on several typical specimens