An Analytical Study On Efficiency Of Seismic Isolation For Mega-frame Structures

The mega-frame structure system is usually formed from the combination of a main-frame and serval sub-frame structural systems, which will subjected to large seismicaction in the horizontal direction during an earthquake. It is suggested that the seismicisolation system be applied in this kinds of system to alleviate its damage. In a mega-frame system with seismic isolation system，a whole structure will be clearly dividedinto the main frame system and the sub-frame system by the seismic isolation system. Itcould be noted, then that the lateral stiffness EI of the main frame, the slide radius r andthe friction coefficient μ of the contacting surface will become the controlling element forthe alleviation of its internal forces.The earthquake dynamic responses of a21floor mega-frame structure wascomputed to analysis the seismic effect of its seismic isolation system. Its numericalsolution was established with its governing equation deviated from Lagrange equation,The solution software from Runge-Kutta method,with MATLAB language, waspresented.Through the analysis of computation results, it is concluded that the seismicisolation system could significantly decrease its earthquake dynamic responses. Thedistribution of the storey drift tend to become even along the structure height. The inter-storey drift, the storey velocity and the storey acceleration could be decreasedsignificantly. A combination of slide radius2.5-3.0m and friction coefficient0.05is theoptimal one. A larger lateral stiffness of the main frame will result smaller lateral drift butlarger internal forces. If the friction coefficient is larger than0.05, the value of shearforce and its distribution along the height of main frame will tend to be stationary.