Wind-induced Response Analysis Of Guyed Mast Structure With Geometrical Nonlinear Effect

With the rapid development of telecommunications industry, the guyed mast structures have been widely used in radio and television broadcasting in the middle of last century.The mast structure would play an important role in the development of telecommunications industry in modern life. As its inherent characteristic in high flexibility, light weight and small damping, the guyed mast is becoming more sensitive to the lateral wind loading. In order to ensure its healthy and safety in the construction and operating state, it is necessary to conduct some research work on the wind-induced response analysis of the guyed mast structures. At present, there are few studies on the wind-induced vibration analysis on the guyed masts in our country, especially for the cases in considering the cable pretension and geometrical nonlinear effect. Previous studies also mainly focus on the frequency-domain method. While the nonlinear time-history dynamic analysis and the aeroelastic wind tunnel test on the guyed masts are relatively lack. Therefore a 285 m height guyed mast, with 4levels for guyed cables anchored at ground level and a flexible antenna cantilevered on the top of the mast, is selected as the research example in this study. The effect of pretension force and geometrical nonlinearity of structure elements in the guyed mast is considered in the nonlinear time-history dynamic analysis method. Results obtained from the time-history analysis method with geometrical nonlinear effect are compared with those from the wind tunnel results and simplified patch load methods. The main contents of this thesis are described and listed as the followings:(1) The time history of fluctuating wind speed along the guyed mast’s height is simulated by linear filtering method for the case of two different types in surface roughness.The Root Mean Square(RMS) and the Power Spectrum Density(PSD) of simulated fluctuating wind speed are compared with the corresponding target values for simulation.The rationality and feasibility of the simulation datum is therefore verified.(2) The procedure to obtain the along-wind loading for the guyed mast is introduced.The drag factor is selected from Canadian design standard S37-01(CSA 2001) to obtain the along-wind loading coefficients. The quasi-steady assumption is adopted to obtain the time-history fluctuating along-wind loading. Thus it provides the input data for time-history dynamic analysis of guyed mast.(3) The MATLAB platform, which could be interacted with well-known structural analysis and design software SAP2000 through the Open Application Programming Interface(OAPI), is developed to establish the three-dimensional finite element model of guyed mast and obtain the finite element analyzed results from SAP2000. The effects of pretension force in cables and geometrical nonlinear effect of the structural elements are considered in the time history dynamic analysis of wind-induced response for the guyed mast by SAP2000. The procedure to obtain the along wind-induced response is described by adopting time history step-by-step Newmark?? method.(4) The experiment procedure of aeroelastic wind tunnel test for the guyed mast is briefly described in this study. The along wind-induced responses in two exposure types(in both open country and over water exposures) and in two wind directions(0oand 60o) are obtained from both time-history analysis method and wind tunnel test. The wind-induced responses from both methods(including the wind-induced displacement and bending moment distributed along the mast height) are compared separately case by case. The compared results show that general agreement could reach for two data sets in most cases.The relative error is between 10% ~ 36%. Thus the efficiency and accuracy of the time-history wind-induced dynamic analysis on the guyed mast with geometrical nonlinear effect could be verified in this study.(5) The simplified wind-induced response analysis method, which is termed as patch load method, is investigated in this study. Comparisons in wind-induced response results between this simplified method and those from nonlinear time-history dynamic analysis methods is conducted for the guyed mast. The feasibility and efficiency of the patch load method is verified through the compared results.