Wind Resistance Analysis of Transmission Tower Considering Interaction Between Tower and Crane Structure

Wind-resistance performance of super high transmission tower during construction has been studied by wind tunnel tests and finite element methods(FEM). The effectiveness of measures against strong wind for the tower and crane has been analyzed and validated. Wind tunnel tests for the 385 m height tower and its construction facility had been conducted. Wind force coefficients of the crane structure were obtained by sectional model tests for the standard crane structure and high-frequency force balance tests for the scaled crane model, and compared with the code values of Load Code for the Design of Building Structures(GB 50009-2012). Two FEM models were established respectively for the crane structure with soft connection to the tower and the tower-crane coupled system to investigate the different wind-resistant performance between two models. FEM analysis had been performed to calculate the maximum crane displacement and the maximum tension of main cables for different cases of balance or unbalance lifting with varying wind angles, and the unfavorable factors in the process of crane construction were analysed. In strong wind conditions, detail evaluations of the proposed wind-resistance measures, i.e., free rotations of double flat arms and lowering the cantilever height of crane, were carried out, which could provide a reference for super high transmission tower during construction.
It was found there exist noticeable difference between wind tunnel results and the code values for wind force coefficients of the crane structure. While the code values may underestimate wind force, wind tunnel tests yield the maximum x or y directional wind force coefficients up to 2.40 and 2.51, respectively. The unfavorable conditions of unbalance lifting and the critical wind angle of 45° have been identified and should be avoided during the construction if possible. The maximum displacement from the tower-crane coupled model is greater than that of a single crane model. On the other hand, the maximum tension of main cables of the coupled model is smaller than the single crane model. The analysis result of the coupled model shows the decreasing of tower lateral stiffness to support the crane due to the smaller tower section at a high altitude during the later stage of tower construction. Correspondingly, a sharp increase of the maximum cable tension was observed from the coupled model at a lower position. In strong wind conditions, the maximum tension of the main cable could be reduced by 30%~40% by free rotations of flat double arms. Therefore, it is suggested to take effective wind-resistance measures, i.e., free rotations of double flat arms or lowering the cantilever height of crane structure to ensure the construction safety of the super high transmission tower under strong wind conditions.