Large displacement analysis of guyed towers

Abstract

A general finite element method using substructuring techniques is presented for large displacement analysis of guyed towers. The finite element model employs two-node (12 degrees of freedom) 3-D beam—column elements and two-node (six d.o.f.) 3-D truss elements to discretise the mast and the cables respectively. The solution technique essentially consists of solving guys and mast separately and alternately forcing the compatibility of displacements at the guy support points until the final equilibrium configuration is obtained. Furthermore, the given external loads are applied in one step. Two numerical examples are solved for increasing wind loads until instability is encountered. The results are compared with the available solutions where appropriate and are found to be in good agreement. The results indicate that the large displacement effects can significantly alter the load-deformation behaviour of a general guyed tower system resulting in lower critical loads. The strains in cables and mast are observed to be substantially higher than the corresponding yield strains as the external loads approach the buckling loads. When cable material is idealised to follow the more realistic trilinear stress-strain relation, the tower response is observed to be more flexible. The present solution method results in considerable savings in storage and computing time.