الفهرس 
CHAPTER (1): INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 171 |  |  |
| | | from | 171 | | |
Abstract
Lattice steel structures have been widely used for many large utilities including telecommunication and transmission towers. Due to the lightweight of these structures, wind forces are the primary concern in the design. The lattice tower members typically consist of steel or aluminum angle sections. The previous published full-scale lattice transmission tower tests gave larger deflection than their theoretical analysis (linear ideal truss analysis). In ideal truss, each member of the lattice tower is assumed pin-connection at its joints cairying only the axial load and no moment. Accurate structural analysis of towers is complicated because the structure is three-dimensional and comprised of angle section members eccentrically connected. The influence of geometric and material nonlinearities plays a very important role in determining the ultimate behavior of the structure. In the current research, finite element models are employed to simulate the nonlinear behavior of lattice transmission towers using ANSYS software package. Also in the current models, L-section beam finite elements which consider the combinations of bi-axial force, axial stretch and shearing force were used to represent the tower members. To obtain a realistic behavior achieves failure modes, the effect caused by joint eccentricity and slippage effects in bolted joint are considered. Furthermore the current research used FE models to represent the telecommunication towers. These models considered geometry and material nonlinearity, the joint eccentricity and slippage effects in bolts. The current models for the transmission towers have been evaluated with results from published full-scale tower tests and numerical models with good accuracy. Also the current models of communication have been studied theoretically.