Comparison Studies Of Dynamic Characteristics And Wind-induced Response Analysis Of Guyed Mast Structure

With the rapid development of Chinese telecommunication and electrical engineering industries, the guyed mast structures have been widely used in radio towers, communication towers and transmission towers. Due to its high flexibility, light weight and small damping,wind loading plays the main role in design for the guyed mast structures. With the improvement of engineering technology, a greater number of the higher guyed mast structures will appear and more widely used.At present, much attention and focus has been given to the studies on the wind-induced response analysis for the guyed mast structures in our country, but previous studies mainly concentrated on the analysis of the guyed mast by considering its linear model, and the frequency domain dynamic method is adopted to study the dynamic characteristics and wind-induced response, while there are few researches of the nonlinear time-history dynamic analysis of the guyed masts relatively. Therefore a 285 m height guyed mast, with 4 levels of guyed cables strained and anchored at ground, is selected as the research example in this study.Three types of finite element model are established, and then the dynamic characteristics and wind-induced response of guyed mast structure are solved by SAP2000 respectively. Results obtained from the time-history analysis method with geometrical nonlinear effect are compared with those incorporating the fluctuating wind loading in lateral wind direction and the effect of aerodynamic damping for the guyed masts respectively.The main contents of this thesis are described and listed as the followings:Firstly, the time history of fluctuating wind speed in the along and the lateral wind directions are simulated by four order auto regressive method. The power spectral density(PSD), the root mean square(RMS) and the turbulence intensity of simulated fluctuating wind speed are compared with the corresponding target values respectively. Andthe simulated values are in good agreement with the corresponding target values.The feasibility of the simulation data is therefore verified.Secondly, calculating the wind loading of the mast and guys in the along and the lateral wind directions were conducted respectively by selecting the drag factor from the Canadian design standard(CSA S37-01). The quasi-steady assumption is adopted to obtain the time-history of the fluctuating wind loading. For the mast, wind loading incorporates the mean wind loading and the fluctuating wind loading in both the along and the lateral wind directions, while only the mean wind loading is considered for the guys. Thus it provides the input data of wind loading for wind-induced response analysis of guyed mast.Thirdly, 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.Then, the theories of simplifying the mast and the guys are briefly described respectively, and the equivalent beam-column model and spring mass model are established on the basis of the three-dimensional finite element model of guyed mast in turn. The modal analysis by SAP2000 is carried out to compare the dynamic characteristics for three types of finite element models above. The feasibility of the simplified models for guyed mast is therefore verified. Thus it provides the input data for wind-induced response analysis of guyed mast.Finally, the along wind-induced responses on three types of finite element models above in two wind directions(60 degrees and 0 degrees) are obtained by nonlinear time-history analysis method. Then the fluctuating wind loading in lateral wind direction and the effect of aerodynamic damping are considered on the along wind-induced responses of the three-dimensional finite element model for guyed mast respectively. The wind-induced responses for three types of finite element models above in both the along and the lateral directions, which includes the wind-induced displacement, acceleration and bending moment,are compared respectively case by case.