Transmission Tower Limit Analysis and Design by Linear Programming

A method is presented for the limit analysis of indeterminate space trusses utilizing the static equilibrium equation and linear programming techniques. Special emphasis is given to obtaining collapse loads for self-supporting lattice transmission towers. A piece-wise step-by-step linear solution employing the stiffness matrixhas been the usual way of handling this problem. The static equilibrium equation has several advantages over the stiffness matrix equation for limit analysis: a direct solution can be obtained in one step; tension onlymembers can be given zero compression capacities; and spatially unstable joints can be stabilized by assigning zero capacity members to them. A very efficient computer program was written by rewriting the linear programming equality constraints in a condensed form and exploiting its sparsity (zero terms). Example problems with the computer program are discussed to demonstrate the analysis method. Potential application of the general theory to the design problem may have substantial advantages over current methods.