BEAM-LIKE BEHAVIOR OF SPACE TRUSSES.

A general approach is developed for determining the overall elastic behavior of space trusses. This is done by casting the matrix equations for pin-ended bars in a suitable algebraic form and using them to construct the finite difference equations for the truss under examination. Characteristic solutions of the homogeneous form of these equations are found in terms of simple polynomial functions. These correspond to the resultant forces and moments applied to the truss. All other modes decay toward these characteristic deflections. This means that the internal loads in the truss can be estimated from the resultant applied loading, even when the truss is not statically determinate. Also, the characteristic response yields elastic properties akin to the axial, torsional, bending, and shear stiffness of beams, although in some cases these effects are coupled. Values for a number of common space trusses are listed. It is also shown how the method may be used to give the natural frequencies of vibration of such structures.