Influence of modeling in the response of steel lattice mobile tower under wind loading

These days there is an unprecedented rise in the number of lattice towers due to an ever increasing demand in communication. Lattice towers are 3D space frames that for design are conventionally analyzed as 2D trusses. For safety and economy, these designs need to be more rigorously analyzed considering them as 3D frames. In this study, two lattice towers of heights 18m and 40 have been analyzed by modeling them by three different structural idealizations namely, as 3D frame, 3D truss and as a hybrid of the two. The wind has been taken as the primary force for the analysis and using Gust factor method, the joint displacements, member forces and maximum stresses have been compared to find out the effect of the difference in the modeling strategy on the design forces acting on a latticed communication tower. It was found that the truss model gives representative values of axial forces /stresses in all members. However, the truss models underestimate the bending stresses because only the effect of out of plane bending has been considered in it. Either of the frame model or the hybrid model may be used for estimates of combined stresses for checking the design. In this study, it was found that the combined stresses necessitated the redesign of base members.