Wind Load Identification And Wind-induced Vibration Analysis Of High-rise Lattice Tower Structure

With the rapid development of the national economy,tall lattice structure have been widely used in all kinds of lifeline engineering.Due to its characteristics in light-weighted,high flexibility and small damping,wind loading has become the main control load for its structural analysis and design.As the mechanism of wind loading on the lattice tower structure is verycomplex,the fundamental theory of wind engineering and the experimental results from the high frequency force balance and aeroelastic wind tunnel test are ultilized in this dissertation to investigate the wind-induced vibration response of lattice tower structures by consdidering the the mode shape correction factor and wind loading identification technique.The main contents of this dissertation are as follows1.Based on the High Frequency Force Balance(HFFB)wind tunnel test results of an idealized high-rise lattice TV Tower,the measured base moments were first modified by considering the inherent semi-rigid HFFB scaled model in the wind tunnel test.Meanwhile the modification effect of coupled three-dimension and nonlinear modal shapes and aerodynamic wind loading coupling to the wind-induced response of the high-rise TV tower was investigated by the proposed six different alternative methods respectively.Under the load cases of five wind azimuths,the wind-induced displacements in along-wind and across-wind direction by considering the modal shape and aerodynamic wind loading coupling modification effect were then compared with those corresponding results evaluated by the assumption of idealized one-dimension straight line modal shape in each direction along the major axes of the investigated high-rise structure.2.Ultilizing the High Frequency Force Balance(HFFB)wind tunnel test results of an idealized high-rise lattice communication Tower,the base shear force and base bending moments in the two directions along the main axis of the lattice tower were obtained by thedimensionless form.The corresponding dimensioless treatment on the base shear force and bending moments and were also conducted for the corresponding prototype structure by the proposed method from ESDU documents.The modification factors for the drag and lift force coefficients in the five wind azimuths were introduced,and their optimized results were obtained by minimizing the difference in the no-dimensional shear force and bending moments coefficients between the wind tunel tests and ESDU specification.Through the identified results for the wind loading acting on the lattice towers,the wind-induced displacement and acceleration response for the investigated communicatio tower were numerically evaluated by the random vibration analysis method in frenquency domain.3.Taking a 285 m height guyed mast with 4 levels for guyed cables as the research example in this study,the drag and lift force coefficients for this tower in the 30 degree wind direction were obtained from ESDU specification.The nonlinear time history dynamics analysis of the guyed mast was conducted by SAP2000 software with the Open Application Programming Interface(OAPI)interface for the MATLAB enviorment.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.The wind-induced responses in two exposure types(in both open country and over water exposures)are obtained from both time-history analysis method.The wind-induced responses from the numerical analayzed method(including the wind-induced displacement and bending moment distributed along the mast height)are compared with those corresponding experimental test results from the aeroelastic wind tunnel test on the same guyed mast.