Amador S., Souza R.

This paper presents a non-linear dynamic analysis of a steel overhead transmission line tower crossing Guamá River, located in Eastern Amazon Region, Brazil. This tower lies in the middle of River and has approximately 75 meters of height, and are supporting the conductor cables which crosses two spans about 700 meters long. The study investigates the effects of Amazon’s wind gusts on the dynamic behavior of these kind of structures. For this purpose, a finite element model was created using frame elements based on the co-rotational formulation to model the trussed towers and the conductors. The computational model was created in OpenSees (Open System for Earthquake Engineering Simulation), such that linear and non-linear dynamic analyses were performed, considering the large displacements and rotations of the cables. In addition to the computational analysis, an experimental modal analysis was also performed using a set of low-frequency accelerometers. Since it is very difficult (if not impossible) to measure the magnitude of wind excitation, an output-only modal analysis method based on stochastic subspace identification was applyed, instead of conventional input-output modal analysis identification methods, to extract the eigenfrequencies and corresponding damping ratios and mode shapes of the tower. Afterwards, a comparison between the computational and the experimental results showed that they are in good agreement. Finally, as a result of the study, an important influence of the transmission line cables on the dynamic behavior of the tower was verified.