This study aims to perform earthquake response analysis of towers carrying tip mass using the finite element method (FEM) based on beam elements and shell elements, respectively. Firstly, a tower carrying tip mass is modeled using shell elements with a fine meshing. 3-D finite element analysis (FEA) is performed to obtain free vibration properties and earthquake responses of tower modeled with shell elements. Then, the tower is modeled using beam elements and the results of dynamic analysis are compared to the results those obtained from model based on shell elements. The mode shapes are presented for both models. It is observed that relative errors between beam based and shell based finite element models are less than 3% for the first three natural frequencies of the tower carrying tip mass. Finally, the dynamic responses of the tower subjected to a strong ground motion using beam element based model are presented in comparison with the results of shell element based FEA where a very good agreement is observed. Overall, the results show that FEA using beam elements which is very simple and needs a very limited time for computation when compared to FEA based on shell elements, provides accurate results for linear elastic seismic response of towers carrying tip mass.
Anahtar Kelimeler: Beam, Earthquake, Finite element, Free vibration, Shell, Tower, Tip mass