Research On Vibration Control Of The High-flexible Television Transmission Tower Based On Energy Dissipating Dampers

The high-flexible television transmission tower has the structural characteristics of uneven mass and stiffness distribution.When suffered strong wind or seismic excitations,it tends to vibrate excessively,and easily causing whiplash effect,resulting in hidden danger to structural safety.Thus,it is of great significance to adopt vibration control devices to suppress dynamic response of the tower and ensure the safety of the structure.Dynamic vibration absorbers(such as TMD,TLD)and passive energy dissipation dampers were mostly used to realize the vibration control of the high-flexible television tower structure.Dynamic vibration absorbers take up structural space and can only control the tuned model response,which limited the control effect.Traditional passive dampers such as friction dampers and viscous dampers often have limited vibration control performance.Recently,with the rapid development of new material technology and intelligent manufacturing technology,some new energy dissipation devices have appeared,such as shape memory alloy(SMA)dampers,electromagnetic inertial mass dampers,particle dampers,piezoelectric friction dampers,etc.The energy dissipation principle of these new dampers differs from that of dynamic vibration absorbers and traditional passive dampers.For example,the SMA damper can use the material superelasticity to enhance the energy dissipation capacity;the electromagnetic inertial mass damper can convert the linear displacement at both ends into angular displacement,so that the damper can generate electromagnetic damping force and inertial mass force to dissipate energy;the particle damper uses the collision of particles to convert and dissipate the structural vibration energy;the piezoelectric friction damper utilizes the piezoelectric effect to realize the adjustable friction force,which can realize the semi-active control of the structural vibration.The application of these new energy dissipation dampers in civil structures has just begun,and the main objects are mainly concentrated in traditional multi-storey buildings.It is undoubtedly a new idea to apply these energy dissipation dampers to the vibration response control of the high-flexible television tower.It is a new attempt of the new energy dissipation technology in the disaster prevention and dynamic response mitigation of the tower structure.At present,there is no related research in this area.To this end,this thesis takes of a large high-flexible television tower in China as the engineering background,and uses the above-mentioned new energy-dissipating dampers to conduct seismic and wind-induced response control of the tower.A 3D finite element analytical model of the tower is constructed by using beam elements,and the calculation of dynamic characteristic of the tower is conducted.A 2D lumped mechanical model which is convenient for dynamic analysis and parametric study of nonlinear dampers is developed,and the seismic and wind-induced response characteristics of the tower are also investigated.A sleeve type SMA damper suitable for television tower structure is constructed.A new self-centering SMA damper which provides self-centering and energy dissipation capabilities by adding SMA springs is proposed.The mechanical models of two types of SMA dampers and their vibration control methods for high-flexible television tower are established.The control performance of two types of SMA dampers on the seismic and wind-induced response of the tower are investigated,and the parametric study and comparison of control performance are also conducted.The results show that the new self-centering SMA damper is a typical displacement-related damper,which makes full use of the superelastic energy dissipation of SMA material and has good energy dissipation capability.The addition of SMA springs improve the adaptability of the peak force of the damper to the service temperature.The mechanical model of piezoelectric friction damper and its control method for high-flexible television tower are established.The control performance of the piezoelectric friction is investigated by local feedback control algorithm with nonlinear Reid damping mechanism,and the control performance is compared with that of the passive friction damper.The results show that the piezoelectric semi-active friction damper is highly adaptable to external loads and is particularly suitable for the structural safety control of the tower when the load intensity is high and for the vibration comfort control when the load intensity is low.The control method of seismic and wind-induced response of the television tower by electromagnetic inertial mass damper is constructed and a detailed parametric study is carried out for the seismic response control.The results show that the electromagnetic inertial mass damper is a typical velocity-related damper,the electromagnetic damping force dominates the control force,and the inertial mass force makes the damper have negative stiffness characteristics,which enhances the energy dissipation capacity of the damper.The electromagnetic inertial mass damper has a stable control performance on seismic and wind-induced response of the tower,especially for acceleration response control,which is suitable for the vibration comfort control of the tower.The seismic and wind-induced response control of the television tower by particle dampers are constructed,and a detailed parametric study is conducted.The results show that the particle damper can effectively suppress the dynamic response of the tower.The control force generated by collision belongs to impact force,has a wide control frequency bandwidth.The damper has good control effect for different earthquake types,and not only suitable for structural safety but also suitable for vibration comfort control.An experimental study on vibration control of the high-flexible television tower is carried out.A 1:70 scaled-tower model is designed and constructed.The experimental study on the vibration control of the scaled tower with particle dampers is carried out.90 parameter conditions are designed to experimentally study the particle diameter,particle mass ratio and number of damper cavities that affect the performance of the particle damper.The experimental research results are in good agreement with the theoretical research results,and the vibration control effect of the particle damper is verified by experiments.