Seismic response of five-story frame structure supported by lead-rubber bearings isolation system is investigated subjected to near-fault ground motions. The main structure is modeled as a simple linear multi-degrees-of-freedom vibration system with lumped masses, excited by near-fault ground motions in the horizontal direction. The variation curves of peak top floor acceleration and peak bearing displacement of isolated building are plotted under different yield shear coefficient. The objective function selected for optimality is to maximize the seismic energy dissipated by the lead-rubber bearings. The main constraint conditions selected for optimality are the minimization of both peak bearing displacement and peak top floor acceleration. Optimum parameters of lead-rubber bearing isolation system are investigated and found that optimum yield shear coefficient of lead-rubber bearings is found to be in the range of 0.10–0.14 under near-fault ground motions. Optimum yield shear coefficient decreases with the increase of second isolation period. Optimum yield shear coefficient of lead-rubber bearings with higher yield displacement is larger than that of lead-rubber bearings with low yield displacement. Optimum ratio of pre-yield stiffness to post-yield stiffness of lead-rubber bearings is found to be in the range of 16–35. Optimum stiffness ratio increases proportionally with the decrease of yield displacement. Optimum stiffness ratio increases slightly with the increase of yield shear coefficient. Excluding the effect of pre-yield stiffness, the optimum second isolation period is recommended to be in the range of 4–6 s.
A nickel‐catalyzed amination to access diarylamines has been developed through C−CN bond activation of aryl nitriles with anilines. In this developed catalytic protocol, various aromatic and heteroaromatic nitriles could be utilized as the electrophiles to couple with substituted anilines. A diversity of diarylamines were obtained in 15–95% yields.
In this paper, a new stability criterion of time-delay analysis is established for active controlled structure system. Based on an improved upper bound for the inner product of two vectors, the maximal value of time delay can be obtained by using LMI control toolbox of Matlab. According to the new method, the maximal delay varying with parameters of controlled structure system is discussed for SDOF system. The criterion is applicable to the theoretical analysis for the delay-dependent stability of SDOF vibrating system. The longer the delay is the worse the efficiency of control strategy. But the system is still asymptotically stable so long as the time-delay lies in the interval of permitted time delay.
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