Study On Anti-collapse Mechanism And Application Of Bamboo-inspired Thin-walled Cylindrical Shell Steel Tower

In recent years,with the development trend of large-scale and complexity of thin-walled cylindrical shell steel tower structures,they are easy to be damaged under earthquake and wind load.As a novel type of structure,bamboo-inspired thinwalled cylindrical shell steel tower has a wide application prospect in improving structural performance.In the thesis,according to the characteristics of a bambooinspired thin-walled cylindrical shell steel tower,starting from the component,system,and measure levels in turn,researches are carried out on hysteretic performance,buckling stability,design method,performance evaluation,and vibration reduction measures,etc.The main work and results are as follows:(1)Through low-cycle reciprocating load tests and numerical simulation methods,the hysteretic behavior of cylindrical shells with different ratios of diameter-to-thickness are studied.The diameter-to-thickness ratio will affect the failure mode of the cylindrical shell.As the diameter-to-thickness ratio increases,the failure mode changes from bottom elephant foot buckling to fold buckling failure.The larger the diameter-to-thickness ratio,the earlier the occurrence of local buckling,which leads to the inconsistent development of section plasticity.The full plastic bending moment is not reached when the section is broken.At this time,the full plastic bending moment is used as the M-? curve bifold line model.The inflection point will be higher than the actual carrying capacity.By introducing the full plastic bending moment correction coefficient,the theoretical formula of full plastic bending moment based on the section characteristics is improved,and the calculation method of the cylindrical shell double line Moment-Curvature model considering the influence of the diameter-to-thickness ratio is proposed.(2)Using the method of linear eigenvalue and nonlinear buckling analysis,the buckling performance of the transition section of the bamboo-inspired cylindrical shell steel towers is studied.The finite element model of the transition section with different reducing angles is established.The influence of the changing angle on the buckling mode and bearing capacity of the transition section is analyzed.The reasonable reducing angle and reinforcement method of the transition section is put forward.The recommended angle of the transition section is 45° to 60°.The twoway stiffener can effectively improve the buckling mode of the transition section.The bending capacity is greatly improved.The reducing angle and reinforcement method directly provide a reference for engineering design.(3)Based on the analysis of the relationship between the macrostructure characteristics of bamboo and its mechanical properties,a bamboo-inspired design method of thin-walled cylindrical shell structure is proposed,i.e.,the equivalent change of stiffness is achieved by changing the wall thickness and setting the stiffeners.Through the Pushover method,the difference of collapse resistance between bamboo-inspired and ordinary cylindrical shell structures with equal mass is analyzed.The ductility and bearing capacity of the bamboo-inspired structure is greatly improved,especially after entering the yield stage.Bamboo-inspired design can be used to improve the collapse resistance of structures under large deformation or extreme load conditions.Therefore,the seismic performance target of bambooinspired design is put forward.(4)Taking the thin-walled cylindrical shell desulfurization tower of a thermal power plant as the research object,a case study of the bamboo-inspired design was carried out,and a scaled model shaking table test was designed.The dynamic response and failure mechanism of the bamboo-inspired cylindrical steel tower under earthquake action have been studied.For cylindrical steel towers with equipment on top,the structural dynamic response does not increase linearly with the increase of top counterweight but increases exponentially,and the displacement response is most significantly affected by the top counterweight.In the early structural seismic design,the change of equipment quality in the later stage should also be considered to ensure a certain safety factor redundancy.The bambooinspired cylindrical shell steel tower is in an elastic state without damage under the action of rare earthquakes with 7 and 8 degrees.After a rare earthquake with 9 degrees,the structure was slightly bent locally,but it has not collapsed,which meets the seismic performance target requirements of the bamboo-inspired design.(5)Based on the theory of fluid-structure interaction,the structural field and wind field models are established.The wind-induced response of the bambooinspired cylindrical shell steel tower is successfully calculated by the numerical wind tunnel method.The correctness of the numerical model is verified by on-site wind vibration monitoring.For the wind-resistant design of this kind of high-rise steel tower with variable cross-section,the stress control is mainly used at the bottom and transition section,and the displacement control is mainly used at the top.Combined with the wind-induced response law and overturning failure characteristics of high-rise thin-walled steel towers with variable cross-sections,the evaluation method of wind-induced response performance is proposed.Specific performance status and control indicators are given.(6)Aiming at the wind-induced vibration sensitivity of the bamboo-inspired cylindrical shell steel tower,a suspended tuned mass damper is proposed.Combined with the natural vibration characteristics of a bamboo-inspired cylindrical shell steel tower,the parameters of TMD have been optimized.The finite element model of the TMD is established by the multi-element combination modeling method,which greatly improves the modeling efficiency.The motion mode of the damper is simulated effectively.A numerical wind tunnel is used to calculate the vibration reduction effect of the TMD under different return periods of fluctuating wind speed.The numerical wind tunnel calculation results show that TMD can effectively reduce the dynamic response amplitude of the tower,the root means a square rate of acceleration and displacement is more than 70%,and the root means a square rate of stress is more than 50%,the maximum displacement stroke meets the installation conditions.The feasibility of TMD damping scheme is verified.