Experimental study on retrofitting of 500 kV transmission tower against ice load

In order to develop an effective retrofitting scheme for increasing the load-carrying capacity of transmission tower against ice load, two pairs of subassemblages for power transmission tower were established based on a typical 500 kV transmission tower which was severely damaged during the ice disaster. Each pair was designed with current code; while an additional diaphragm was added to its counterpart as a measure of retrofitting. The comparative tests on mechanical behavior, failure pattern and ice load-carrying capacity of the structures were conducted. The favorable effect of adding diaphragm in terms of improving structural performance of tower subassemblages was investigated. FEM software ANSYS was employed to analyze the behavior of the subassemblages by using shell elements. The study revealed that after adding diaphragm the out-of-plane deformation in the joints of cross-bracings was reduced significantly. Buckling mode of the main member was transited from torsional-flexural buckling to flexural buckling. And for one-panel and two-panel tower subassemblages, the ultimate strength was increased by 18.3% and 17.6% respectively. The diaphragm comprehensively improved the mechanical performance of transmission tower structures by decreasing the unfavorable influence of torsion of main member, and together with inhibiting the out-of-plane deformation of diagonal braces. Adding diaphragm is an effective and practical retrofitting method for enhancing the ice load-carrying capacity of transmission tower structures. © 2011 Chin. Soc. for Elec. Eng.