Theoretical And Experimental Research On The Intelligent Stability Control Of Space Structure

Space steel structure is one of the most widely used architectural forms for the time being. Because the steel is of lightweight yet of high strength, and has a slender section, as a result, what causes the failure of this kind of structure is not the lack of strength, but the occurrence of a special state of instability, that is to say the buckling of the structure. Due to the sudden failure of buckling for structure or member, once the buckling develops, the structure will immediately collapse and lead to disastrous consequences. So the research on the dynamic and static stability for space steel structure becomes rather theoretically significant and of practical value.Nowadays the principal methods to prevent buckling of the structure include the increase in area of cross-section and on the control of slenderness ratio, etc, which belong to a kind of passive fortification method. For this reason, based on the thought of control over structure, this paper puts forward a new method, which utilizes the piezoelectric pivot member bar to realize intelligent stability monitoring and control over the space steel structure; meanwhile, in this paper the corresponding theoretical and experimental researches are conducted, and the main work is as following:(1) First of all, according to the basic electro-mechanical behavior of piezoelectric material, this paper deals with details of pivot element bar appropriate to control over the buckling of skeleton steel structure; the bar is laminated from slices of piezoelectric ceramic; it is mechanically tandem and electrically parallel, thus which can realize a requirement for big driving force and displacement, and at the same time reduce the requirement for too high driving voltage. Therefore, both the requirement for bearing capacity of structure can be satisfied, and test and drive of structure can be synchronously implemented.(2) Taking the piezoelectric pivot element bar addressed here as a calculation model, this paper studies the static stability of the pivot element bar, analyzes influences of such factors as different length ratios, stiffness ratios, and driving forces etc, and then obtains laws of numerical relation between them; this paper also investigates the dynamic stability of the pivot element bar, considers the dynamic stability respectively under the action of shock load, simple harmonic load, and random load of earthquake, and furthermore proposes theoretical analysis models corresponding to the control of static and dynamic stability.(3) By the use of self-compiling Matlab program, taking the simple harmonic load as an example, this paper researches behaviors of dynamic stability control in considering and neglecting the electro-mechanical coupling of the pivot element bar, through tracking its former three zones of dynamic buckling, this paper investigates the influence of such factors on behaviors of dynamic stability control as the length of piezoelectric pile, the gripping force of piezoelectric pile and the characteristic of external excitation etc., and also obtains a general law of the behavior of dynamic stability control of the piezoelectric pivot element bar.(4) This paper performs an experimental research on 122 ordinary member bars with 17 slenderness ratios, comprising two different materials, makes a theoretical derivation, thus puts forward a double-parameter criterion of stability break based on explicit responses of the structural members, yields corresponding simplified calculation formulae. Additionally, this paper still studies the optimal length and placement of piezoelectric pile in the pivot element bar, designs and fabricates two piezoelectric pivot element bars for tests; meanwhile, the corresponding tests of stability control are conducted to verify the effectiveness of its static and dynamic stability control.(5) On the basis of the electro-mechanical coupling effect of piezoelectric materials, buckling criterion and stability control equations presented in this paper, the Visual Basic program is compiled, which integrates multifunction including wave generation, data acquisition, threshold judgment and driving function etc. In the meanwhile, the special intelligent controller suitable for the monitoring of buckling and stability control for space steel structure is designed and exploited, and realizes the synchronous data acquisition and control of structure states.(6) According to the theory of optimum control, this paper explores theoretical model of optimum analysis for space structure with the piezoelectric pivot element bars set, advances the corresponding practical optimum design method, that is the method of the maximum relative displacement, discusses the calculation method of the maximum contribution rate and procedures as well as the optimal placement of the piezoelectric pivot element bars; besides, this paper designs and fabricates 2 space structure models with the piezoelectric pivot element bar.(7) Considering the electro-mechanical and non-electro-mechanical coupling effect, this paper conducts shaking table tests on 2 space structures with or without control. Respectively input El-centro earthquake wave and simple harmonic wave etc. Here, the peak acceleration of earthquake excitation is 200gal-1200gal, the magnification times of driving voltage at the excitation of simple harmonic wave is respectively 1, 10, 20 and 30 so as to investigate stability monitoring/ stability control law and effectiveness of the piezoelectric pivot element bar.(8) Based on the nonlinear finite element method, considering the electro-mechanical and the non-electro-mechanical effect of the piezoelectric pivot element bar, this paper performs a dynamic time-history analysis under the excitation of X, Y and X-Y-Z axis. The analysis results are in a good agreement with experimental results of shaking table.(9) In accordance with the results of dynamic time-history analysis for the model structures, based on B-R criterion and the double-parameter criterion advanced here, this paper discriminates the dynamic stability break of model structures respectively, obtains critical peak accelerations of model structures with and without control. The calculation results have a high precision, which demonstrates the reliability of discriminant results obtained by the use of explicit double-parameter buckling criterion and these results can provide reference for engineering application.