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1.
Rolling isolation systems (RISs) protect fragile building contents from earthquake hazards by decoupling horizontal floor motions from the horizontal responses of the isolated object. The RISs in use today have displacement capacities of about 20 cm. This displacement capacity can be increased by stacking two systems. This paper presents and evaluates a complete non-linear model of the coupled dynamics of double RISs. The model is derived through the fundamental form of Lagrange׳s equation and involves the non-holonomic constraints of spheres rolling between non-parallel surfaces. The derivation requires the use of two translating and rotating reference frames. The proposed model is validated through comparisons between experimentally measured and numerically predicted time histories and peak response quantities—total acceleration and relative displacement. The effects of the initial conditions, the mass of the isolated object, and the amplitude and period of the disturbance on the system׳s performance are assessed. 相似文献
2.
虽然武汉市地震影响及地震危险性的水平较低 ,强震也不是武汉市工程地质环境的主要问题 ,但在城市生命线工程和高层超高层建筑方面必须考虑单体抗震设防。而且 ,随着武汉市城市建设的不断发展 ,地震效应影响逐渐成为武汉市工程地质环境评价的一个重要因子。文章在分析了武汉地区地震动衰减规律 ,进行了地震危险性评价 ,深入研究了各土层动力参数性质的基础上 ,指出武汉地区地震地面破坏主要存在砂土液化和软土震陷两种型式及各自可能的空间分布. 相似文献
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F. Nucera A. F. Vakakis D. M. McFarland L. A. Bergman G. Kerschen 《Nonlinear dynamics》2007,50(3):651-677
In the field of seismic protection of structures, it is crucial to be able to diminish ‘as much as possible’ and dissipate
‘as fast as possible’ the load induced by seismic (vibration-shock) energy imparted to a structure by an earthquake. In this
context, the concept of passive nonlinear energy pumping appears to be natural for application to seismic mitigation. Hence, the overall problem discussed in this paper can be formulated
as follows: Design a set of nonlinear energy sinks (NESs) that are locally attached to a main structure, with the purpose of passively
absorbing a significant part of the applied seismic energy, locally confining it and then dissipating it in the smallest possible
time. Alternatively, the overall goal will be to demonstrate that it is feasible to passively divert the applied seismic energy
from the main structure (to be protected) to a set of preferential nonlinear substructures (the set of NESs), where this energy
is locally dissipated at a time scale fast enough to be of practical use for seismic mitigation. It is the aim of this work to show that the concept of nonlinear energy pumping is feasible for seismic mitigation. We consider
a two degree-of-freedom (DOF) primary linear system (the structure to be protected) and study seismic-induced vibration control
through the use of Vibro-Impact NESs (VI NESs). Also, we account for the possibility of attaching to the primary structure additional alternative NES configurations
possessing essential but smooth nonlinearities (e.g., with no discontinuities). We study the performance of the NESs through
a set of evaluation criteria. The damped nonlinear transitions that occur during the operation of the VI NESs are then studied
by superimposing wavelet spectra of the nonlinear responses to appropriately defined frequency – energy plots (FEPs) of branches
of periodic orbits of underlying Conservative systems. 相似文献
7.
Many dynamical systems are subject to some form of non-smooth or discontinuous nonlinearity. One eminent example of such a
nonlinearity is friction. This is caused by the fact that friction always opposes the direction of movement, thus changing
sign when the sliding velocity changes sign. In this paper, a structure with friction-based seismic base isolation is regarded.
Seismic base isolation can be employed to decouple a superstructure from the potentially hazardous surrounding ground motion.
As a result, the seismic resistance of the superstructure can be improved. In this case study, the base isolation system is
composed of linear laminated rubber bearings and viscous dampers and nonlinear friction elements. The nonlinear dynamic modelling
of the base-isolated structure with the aid of constraint equations, is elaborated. Furthermore, the influence of the dynamic
characteristics of the superstructure and the nonlinear modelling of the isolation system, on the total system’s dynamic response,
is examined. Hereto, the effects of various modelling approaches are considered. Furthermore, the dynamic performance of the
system is studied in both nonlinear transient and steady-state analyses. It is shown that, next to (and in correlation with)
transient analyses, steady-state analyses can provide valuable insight in the discontinuous dynamic behaviour of the system.
This case study illustrates the importance and development of nonlinear modelling and nonlinear analysis tools for non-smooth
dynamical systems. 相似文献
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Qinghua Huang Yufeng Lin 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(3):257-264
Although seismic electric signal (SES) has been used for short-term prediction of earthquakes, selectivity of SES still remains as one of the mysterious features. As a case study, we made a numerical simulation based on a 3D finite element method (FEM) on the selectivity of SES observed in the case of the 2000 Izu earthquake swarm. Our numerical results indicated that the existence of conductive channel under Niijima island could explain the reported SES selectivity. 相似文献
10.
Alemdar Bayraktar Abdurrahman ahin D. Mehmet
zcan Faruk Yildirim 《Applied Mathematical Modelling》2010,34(1):92-121
In the present paper, the numerical damage assessment of the masonry bell tower called “Haghia Sophia” in Trabzon, Turkey is performed by nonlinear 3D finite element modeling. The behavior of bell tower is determined under several different conditions: nonlinear static analysis containing dead and wind loads and nonlinear seismic analysis. In addition to, an assessment of the tower’s stability with respect to the tilt of the tower is carried out by means of a nonlinear analysis. In the nonlinear dynamic analysis, the east–west component of 1992 Erzincan earthquake is used. Cracking and crushing of the masonry have been taken into account, as well as the influence of material nonlinearity. The numerical analysis has given a valuable picture of possible damage evolution, providing useful hints for the prosecution of structural monitoring. The displacement and stress fields, as well as the distribution of cracking have been calculated and compared to the actual distribution of fractures in the tower. It is seen from the numerical results that there is a good agreement with present damages of the bell tower. 相似文献