Lateral Stability of Cable Truss

The possible lateral instability of cable trusses under vertical loading is examined for trusses that are initially symmetric about the longitudinal axis. Variational methods were used to derive the differential equation governing lateral stability of biconvex or biconcave trusses that are symmetrical about the longitudinal axis. Analytical solutions were given for the parallel chord truss (a limiting form of the biconvex or biconcave truss) and triangular chord truss under a point load and a uniformly distributed load. A simple general result was found for the buckling of a truss under a point load, where the load and apex are both at midspan. From this, specific results were derived for the parabolic cable truss. Lateral instability is an unlikely possibility in a properly designed cable-truss roof. The presence of the roofing material and cross-bracing members between adjacent trusses will add considerably to the overall stability of the structure.