| The large-span spatial structure is being adopted by a number of important public buildings in many cities for its advantages of meeting many special requirements of architectural functions. However, it’ll do great harm once these buildings are damaged or collapsed during an earthquake. So it’s very essential to study in-depth the seismic performance of space truss and latticed shell structures and to take the necessary measures for seismic monitoring.Using the super-elastic properties and resistance sensing characteristics of shape memory alloys (Shape Memory Alloy-SMA) materials, through theoretical analysis and model tests, this paper designed and produced two kinds of SMA seismic monitoring and control system which were tested in the shaking table test of two spatial model structures. The main research contents include:(1) Aiming at avoiding the large slip of SMA materials in the test, the method of conventional material test was improved. The super-elastic mechanical properties of a new type of SMA wire with the chemical composition of Ti-51%atNi made in china were tested, which is the austenitic state at room temperature. The influences of adding/unloading frequency, strain amplitude and adding/unloading cycles on the internal friction factor, damping energy and other properties of SMA material were studied in the test. Additionally, this paper proposed some advices to improve and enhance the mechanical properties of SMA materials.(2) Based on the super-elastic mechanical properties of SMA materials mentioned above, combined with the establishment methods of constitutive model in phase-only theory, two new kinds of super-elastic constitutive model of SMA materials are put forward, which are respectively the curve constitutive model and the improved linear constitutive model. Combined with theoretical analysis and computer simulation, the computer analysis program of two kinds of constitutive models are finished by using MATLAB7.0 programming software, and the results of simulation analysis are in good agreement with and experiment results. The proposed two kinds of constitutive models are better to reflect the super-elastic mechanical properties of SMA materials and plus/unload frequency characteristics; therefore they have the good prospects of theoretical and engineering application.(3) A set of SMA materials resistance-displacement sensor dynamic testing system is developed for the study of monitoring sensor performance of austenite SMA materials. The relationship between resistance change rates and strain of austenitic SMA material was studied in the process of static and dynamic add/unloading; the impacts of add/unloading strain amplitude, add/unloading rate, diameter change of SMA wires and add/unloading cycles on the resistance-strain sensing characteristics of the austenitic SMA materials were discussed; the linearity, hysterics, sensitivity and repeatability of relationship curve between resistance change rates and strain were evaluated through theoretical analysis. Additionally the monitoring sensor performances of SMA materials are discussed systematically, which is provided for the development of static and dynamic monitoring system of SMA.(4) Based on the results above, taking the austenitic SMA material as a core component and using its special super-elastic properties and resistance sensing characteristics, two new kinds of SMA passive seismic monitoring control system with a function of displacement amplification and self-reset were proposed and developed through theoretical analysis. The design construction methods, working principles and application conditions of the system were discussed; the corresponding composite sensor/passive control technology and maximum reuse ability were analyzed; the impact of displacement amplitude, loading frequency, loading cycles and other factors on their sensing characteristics and energy performance were studied; the stability of the system, the effectiveness of the system’s energy consumption, and the system sensor accuracy and sensitivity were examined; the corresponding mechanical analysis and computing model were established, and the integration of technology and identification methods with the main structure were studied. The system has the self-sensing performance, efficient energy consumption and self-reset features, additionally it’s easy to install and replace, which is worthy of further development and application.(5) In order to test the effectiveness of this SMA passive seismic monitoring and control system, the earthquake shaking table tests were carried on two kinds of spatial structure model, which were respectively installed and not installed the new SMA passive seismic monitoring and control system. There were 30 conditions in the test, in which EL-Centro earthquake wave was adopted with acceleration of 200gal-1200gal, and the monitor and control effects of SMA passive seismic monitoring and control system, especially the effects of passive control, were studied. At the same time, using ANSYS finite element analysis program, the displacement, acceleration and other seismic responses of the model structure with and without this new system in a various conditions were analyzed; its control mechanism and rules were discussed, and the effectiveness and applicability of passive seismic monitoring and control system were examined. Finally, using numerical analysis methods with different types of seismic waves and structures, the effects of the number, location, local control and overall control of SMA passive seismic monitoring and control system were studied; the corresponding control mechanism was analyzed and the better passive control programs were put forward.The results show that the theoretical analysis and computational model established in this paper has better applicability, which can reflect the unique physical and mechanical characteristics of SMA materials; Both the developed SMA passive seismic monitoring and control system, and the proposed passive seismic control scheme have better monitoring control effect, and the effect of damping control can be up to 30%. Therefore it can be used for the passive seismic control and displacement real-time monitoring of spatial structure. |
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