| Transmission towers are important components of lifeline engineering.Their damage after strong earthquake will not only bring huge economic losses to the country,but cause some secondary disaster such as fire,water shortage,power off,which will create difficulty to earthquake relief and reconstruction.However,because of the complexity of strong earthquake and the particularity of transmission tower structure,those designed by the newest standard still suffered from serious damage on some recent earthquake,which lead to paralysis of the whole lifeline engineering.This forced researchers to find some new way about aseismic design theory or damping method to ensure the safety of these structures.This paper using shape memory alloy(SMA)and piezoelectric stacks as core parts,designed a kind of SMA passive and piezoelectric stacks semi-active friction hybrid control damping system,and applied it to the analysis and tests for passive and semi-active hybrid control of high voltage transmission tower seismic response,obtained some new results and suggestion.The main research contents are as follows:1.According to the main feature of seismic response and the earthquake damage survey results of transmission towers,using the special physical and mechanical properties of SMA and piezoelectric stacks,designed a kind of integrated SMA passive and piezoelectric stacks semi-active friction hybrid control damping system,which is tiny and easy to install with transmission towers.The working principle is when the structure has low seismic response,SMA passive damping as the main way;when the structure has high seismic response,piezoelectric stacks semi-active friction device plays a greater role,and SMA is responsible for reset after earthquake.Thus,the work performance reliability of the damping system can be ensure,and passive or hybrid damping control can be adjusted by structural seismic response.The damping control ability of the system can be increased obviously.2.Based on the above integrated SMA passive and piezoelectric stacks semi-active friction hybrid control damping system,considering the regional specificity of transmission towers,the damping control performance test for hybrid damping system was carried out,with a independent photovoltaic power device providing power.The influences of SMA initial state,working condition of piezoelectric stacks,excitation voltage on control effect of the damping system were researched.The general law of control effect was summarized.The results showed that the designed damping system is tiny and easy to fit with transmission tower.The hybrid control ability is excellent,especially when piezoelectric stacks semi-active device works.The relationship between the damper absolute maximum control force and voltage is linear increase.When the displacement amplitude was 12 mm,in the meantime voltage was 120 v,the energy dissipation ability could be increased to 138.31%,the equivalent damping ratio could be increased to 92.45%.3.On the basis of the performance tests data of SMA wires and the damping system,we built corresponding BP neural network forecast constitutive model with different kinds of nerve cell import way.Meanwhile we optimized the initial weight and threshold value of neural network models of the SMA wires and the damping system by genetic algorithm.Two kinds of the optimized BP neural predicted constitutive model were built.The results showed that using displacement,speed symbol and voltage as the nerve cell imports is simple and easy to application.Especially though genetic algorithm optimized BP network constitutive model is more precise and stable,can apply to optimization and design of the damping system.4.Aim at the disadvantage of the general immune colon selection algorithm(ICSA),a modified ICSA according to bring in the antibody concentration and the adaptive mutation was proposed.Setting model control level as the performance index of optimal configuration,taking prototype of a typical transmission tower,the optimization of number and position of the damping system in the structure model were analyzed by the modified ICSA.The optimized control effect was researched.The results showed the modified ICSA has rich population diversity,powerful optimization ability and rapid rate of convergence,it can acquire high performance index and well damping effect.Generally,compared to arbitrary assignment scheme,damping control effect of configuration optimization scheme could increase about 20%.5.Combing with fuzzy control and neural network,a fuzzy neural network calculation model applied to the hybrid damping control of transmission towers structure was designed.And using the optimal allocation strategy from above modified ICSA,integrating the damping system on the above typical transmission tower model,seismic response numerical simulation of hybrid damping control of transmission tower was analyzed.The results showed that the fuzzy neural network semi-active control system can obvious weaken seismic response of the transmission tower structure,the control effect generally reach 50%.6.Taking one typical transmission tower as a prototype,a scale model structure with a similar ratio of 1/15 was made,deployed with the above damping system according to the modified ICSA.Using fuzzy neural network control algorithm,shaking table tests for the scale model structure with and without the damping system were conducted,dynamic response of the scale model structure and damping effect of the model structure with damping system were analyzed.The results indicated that the designed damping system can enhance whole performance of scale model structures and reduce seismic response of it.When input peak acceleration was 220 gal,the best damping effect of structure displacement could reach 50.8%.When input peak acceleration was 400 gal,the best damping effect of structure acceleration could reach 42.4%.Therefore,the damping control system and fuzzy neural network control algorithm have obvious damping effect,worth further research and promotion. |
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