Impact Response Of Long-span Transmission Tower Built In Rivers And Its Design Method Of Model Tests

For the transmission towers built in rivers and seas, the impact force of ship striking was one of the most important designing loads. Nevertheless, the researches about the impact-dynamic response and model test of the transmission towers had not been carried out. It was necessary to study the impact-dynamic response of long-span transmission towers considering high-pile cap. Besides, reflect of different parameters and the designing method of model test should also be studied.This article will include the study about simulation analysis of the progress of long-span transmission towers collided by mass and the dynamic characteristics of the tower considering elevated pile cap. Based the comparison of the dynamic responses of different stiffness of foundation, initial velocities and qualities of mass, the effect law of these parameters can be found. At last, the similar relationship for model test would be deducted using the method of dimension analysis, the accuracy of the similar relationship can be validated by simulation analysis result.The main contents of this paper are as follows:(1) The dynamic characteristic of long-span transmission tower structureThe application of ANSYS/LS-DYNA software to establish the finite element model of long span transmission tower with high pile cap foundation interaction, so as to carry out the study of modal analysis of structure. Based on the contrast of free vibration characteristics of the single tower, elevated pile cap and long-span tower considering elevated pile cap & the free vibration characteristic changes with the change of the foundation stiffness, the conclusion can be seen as:the self-vibration period of the tower considering elevated pile cap is larger the single tower; as the decrease of foundation stiffness, torsion deformation tends to be region which caused by the torsion of high pile cap, the self-vibration period of the tower considering elevated pile cap will change suddenly.(2) The analysis of influence factors of impact-dynamic responseThe model of long-span transmission tower bashed by the mass was established with the application of finite element software, in order to analysis the impact force and the energy transformation during after the impact; the deformation in the X-Y plane and Z-direction, the period and the amplitude of self-vibration; the period and the amplitude of self-vibration at different initial velocities, the quality of mass and stiffness of foundation. The results of analysis show that with the decrease of the stiffness of foundation, the amplitude of self-vibration increased; the amplitude of self-vibration, the impact force and the initial velocity were of positive linear correlation; with the increase of the quality of mass, the impact fore and the amplitude increased, the amplitude and the 0.5 party quality of the mass were of positive linear correlation.(3) The design method of model test for long-span transmission tower structureThe dynamic similarity and impact-dynamic similarity conditions has been derived with the application of dimensional analysis. Besides, analysis of the vibration characteristics and the impact response of two kinds of similar models were carried out. According to contrast of the analysis results of two similar models, the dynamic similarity model was similar to theoretical results of prototype model in terms of the vibration period and vibration amplitude, for taking into account the impact load conditions to ensure similar. The result shows that the impact-dynamic model is the appropriate design method for impact model test.