Applied Mechanics and Materials Vols. 105-107

Abstract: To protect movable cultural relics,by shaking table tests oscillation responses of museum free-standing cultural relics under earthquakes were studied.Based on actual sizes of a museum showcase,a 1:1 scale model was built whose bottom was fixed on the shaking table.A bronze cultural relic was put in the showcase by free-standing mode.By white noise excitation frequency distributions of the showcase were obtained;By inputting 3 different types of earthquake waves (El-centro wave,Taft wave and Artificial wave of ΙΙ site classification) with different intensities (0.1g,0.2g and 0.4g of peak ground accelerations) ,seismic responses of both showcase and relic were studied, their damage types were discussed, displacement as well as acceleration response curves of typical positions were analysed as well.Results show that prominent frequency ingredients of the showcase are between 30-40Hz,which are far from those of input earthquake waves,thus the showcase is not damaged seriously;while for the relic when input earthquake intensity is low,its main damage symptom is oscillation;when earthquake intensity increases,the oscillation response becomes very serious and the relic is prone to overturn and get destroyed.

Abstract: To study the seismic failure effect of subgrade, the field investigation and analysis of seismic failure of the subgrade are conducted. six seismic failure modes of the subgrade are proposed, (1) shallow surface sliding of slope, (2) development of slip surface within the body of subgrade, (3) development of slip surface reaching the foundation, (4) overall sliding of sloping subgrade, (5) slumping, and (6) desification. Meanwhile, the investigation shows that seismic subsidence rate and wave-like deformation amplitude rise with the increase of seismic intensity, the degree of subgrade damage is closely related to the characteristics of route selection. The research has analyzed the seismic damage mechanism of the subgrade, explores a new concept of seismic design based on allowable deformation proposed by Ikuo Towhata.

Abstract: Shell stiffeners are used effectively to prevent preferential local buckling of LNG tank shell. In this paper, Finite element method (FEM) is applied to pay attention to the thermal analysis on the shell stiffeners of double steel wall LNG storage tank. The structural requirements according to British Standard 7777-2:1993 has been considered and then some dimensional adjustments of shell stiffeners are made to evaluate their influence on the thermal field of double steel wall LNG storage tank. Temperature distributions and heat flux of different dimensional shell stiffeners are presented. Though the analysis of results, it puts forward the conclusion that the dimensional design of shell stiffeners used in double steel wall LNG storage tank shall take not only the structural design requirements but also the thermal design ones into consideration in order to finally save cost in both construction and normal operation.

Abstract: Damping in double Cables suspension bridge composed of steel reinforcement beams and reinforced concrete tower is non-classical, which leads to coupled equations of motion in main coordinate system. Based on the complex damping theory, the viscous damping ratio is solved, which can be used to describe energy dissipation characteristics of non-classical damping system approximately. Seismic response of double chains suspension bridge is analyzed through an example of double chains suspension bridge, considering the geometric nonlinearity and non-classical damping. And numerical calculation is presented for seismic response subjected to independent effect or combination effect of three orthogonal components of seismic wave. Single cable suspension bridge can be taken as a special case of double cable suspension bridge, after the main cable shape coefficient is introduced. The dynamic responses of double cable suspension bridge and single cable suspension bridge are compared to reveal the characteristics of Seismic Response of double cable suspension bridge. The study of the dynamic responses characteristics of double cable suspension bridge has a positive significance on structural form selection of such type bridge during designing, dynamic performance evaluation and reinforcement design has positive significance.

Abstract: In order to get over the defects of traditional sliding base isolation structure which the reactions of traditional sliding structure has always increased during the earthquake, and obtain sliding base isolation technology application for the frame structure. Based on the research of U work performances of energy-absorbed element, the whole element model of this new kind of sliding base isolation three storey frame structure with equipment of sliding-limit was established by the SAP2000 software. According to reasonable hysteretic mode, the calculation analysis under collision responses were carried out. The calculation results showed that the rigidity of the new sliding-limit had a great influence on changes of the storey acceleration and displacement after collision. The maximum base sliding displacement of both earthquakes loading was obviously bigger than that of a single earthquake loading. With the other direction loading earthquake increasing, the maximum base sliding displacement of the structure showed signs of increasing first, and then decreasing. Effective theoretical basis of sliding base isolation technology being applied to the frame structure were provided.

Abstract: To protect free-standing object,a rectangular object is taken as example and by SIMULINK technique its oscillation response under earthquakes were studied.Based on static and dynamic balance theories,oscillation conditions as well as motion equations of the free-standing object under earthquakes were deduced;Based on SIMULINK model,simulation analysis on the object under both level and vertical earthquakes were carried out,parameters such as initial conditions,earthquake intensity and ratio of width of the object against its height (B/H) and so on were discussed.Results show that under earthquakes oscillation conditions of the object relate closely to B/H,earthquake intensity and friction coefficient between object and its base;Under earthquakes oscillation response of the object is sensitive to initial conditions,and the response becomes more serious under less B/H or larger earthquake intensity conditions.Besides, SIMULINK technique can effectively simulate oscillation response of free-standing object under earthquakes,which proves the technique useful.

Abstract: As the improvement of honing velocity, acceleration and accuracy, corresponding requirements about control technology are put forward to meet the improvement of high machining efficiency. While the honing machine spindle reciprocating reversing control is the key control link, directly affects the ability of the machine abilities and quality. Aim at the traditional honing machine reciprocating motion cannot satisfy the requirement of high speed, high acceleration and high reversing accuracy. According to the characteristics of honing machine mechanism of reciprocating movement, establish its mathematic model and the system of fuzzy and PID double control model, and then the control system was conducted by using the tool of Simulink. The simulation result showed that using fuzzy and PID double control can make overshoots reduced compared with conventional single fuzzy control and PID control, and can well satisfied the system performance index.

Abstract: Earthquake is one of the major threats towards building and non-building structure and various seismic isolation technologies have gained a good development all-round the world. Based on such a condition, a new form of seismic isolation technology is raised, which combine rolling bases and dampers to isolate floor slabs from quake wave. Analysis towards scaled model dynamic test shows that this seismic isolation technology for floor slabs can effectively reduce response acceleration of floor slabs, especially when frequency of input acceleration is high. While frequency of input acceleration is low, it has to be assured that when slab hits damper, the hitting should be soft so that the response acceleration can be controlled at a low level.

Abstract: This paper presents the stability and bifurcation of a continuum rotor with transverse electromagnetic and bearing excitations. The rotor system is modeled as continuous beam which is excited by uniformly distributed electromagnetic force and two oil-film forces. Using the Galerkin’s method, the partial differential equation of nonlinear motion is discretized as second order ordinary differential equations. The harmonic balance method is used to determine the approximate periodic solution, then the Floquet multipliers are obtained and the stability of periodic solution can be judged. The Andronov-Hopf bifurcation is presented when the leading Floquet multiplier continually changing with rotation speed passes the unit circle on the complex plane. Bifurcation diagrams of displacement with varying rotation speed are obtained using the Runge-Kutta method. Periodic motion and quasi-periodic motions appear alternately with the rotation speed showing inherent interaction between electromagnetic force and oil-film forces.

Abstract: The virtual prototype model of the coal screen is established with Pro/E and RecurDyn based on virtual prototype technology. The kinematic characteristics of different points are obtained by simulation. At the same time, the finite element analysis model of a screen box is established with ANSYS. Modal analysis and harmonic analysis have been carried out based on dynamic analysis technology. According to the results of dynamic finite element simulation, some corresponding improvements were made for the structure of screen box, which makes the stress concentration region of screen box decreased and more uniform stress distribution to meet the design requirements.