Study On Seismic Responses Of Free-Standing Equipments And Numercial Simulation

The situation and scientific research outcome of the research were analyzed by studying a large numbers of literatures. The seismic sliding theories of free-standing equipments were deeply researched. And the seismic responses of free-standing equipments were carried out by the method of numerical simulation.1. Combined with some relative regulations, the aseismic design principle of free-standing equipments and the measurement method of static friction coefficient and kinetic friction coefficient were analyzed. This work provided a basis for the selection of friction coefficient in numerical simulation.2. The paper deeply researched the seismic sliding theories of free-standing equipments and the model of friction. As long as there was motion, the magnitude of friction force was constant and its direction was opposite to that of the sliding velocity. As a result, whenever the sliding velocity crossed zero, the friction force made a sudden change in direction. This sudden change in the direction of the friction force made the system extremely non-linear and the solution process highly complicated. So a sequential friction model was replaced of coulomb friction. Then a program for time-history analysis of seismic responses was written using Runge-Kutta method. When verified the reliability of the program, we analyzed calculating results and expressed the response of sliding rigid structure to base excitation. The effect of parameters were analyzed which contained the friction coefficient(μ), the vertical acceleration coefficient(k) and horizontal peak base accelerations(HPBA). And then Formula for restrained free-standing equipments was deduced, and the calculating results were compared with the results of unrestrained free-standing equipments.It was suggested that the seismic response of free-standing equipments were very sensitive to the change of parameters. If we did not consider the effect of the vertical acceleration in practical design process, we would not get an accurate result. The influences of the vertical acceleration to system were underestimated. The displacements of restrained free-standing equipments were reduced obviously and might come back to initial position. This proved the accuracy of the program and the effectiveness of seismic reduction of restrained free-standing equipments.3. Through the research on the rock theories of free-standing equipments, this paper determined the periodic response of the equipments and the number of collisions. We could get the rock response of free-standing equipments to harmonic excitation or load of short duration and the critical condition of overturning. It was suggested that the response of overturning was nonlinear and the periodic response of the equipments depended on the initial condition. In the equation of motion, the kinetic energy and the angular velocity of the model were decided by the reduction of energy by the impact. A program was written for time-history analysis of seismic responses by the method of numerical simulation and verified the reliability of the program. And then the curves of time-history response were drawn according to the calculated results.4. The differential equations of motion of a multi-degree of freedom were established according to the response of free-standing equipments to seismic excitation. The differential equation group of motion was converted into one order non-linear differential equation group by introducing a state vector. The equation group was resolved by Runge-Kutta method. Then a program for time-history analysis of seismic responses was written.