Multiple‐slider surfaces bearing for seismic retrofitting of frame structures with soft first stories

A new isolation interface is proposed in this study to retrofit existing buildings with inadequate soft stories as well as new structures to be constructed with soft first story intended for architectural or functional purposes. The seismic interface is an assembly of bearings set in parallel on the top of the first story columns: the multiple‐slider bearings and rubber bearings. The multiple‐slider bearing is a simple sliding device consisting of one horizontal and two inclined plane sliding surfaces based on polytetrafluoroethylene and highly polished stainless steel interface at both ends set in series. A numerical example of a five‐story reinforced concrete shear frame with soft first story is considered and analyzed to demonstrate the efficiency of the proposed isolation system in reducing the ductility demand and damage in the structure while maintaining the superstructure above the bearings to behave nearly in the elastic range with controlled bearing displacement. Comparative study with the conventional system as well as various isolation systems such as rubber bearing interface and resilient sliding isolation is carried out. Moreover, an optimum design procedure for the multiple‐slider bearing is proposed through the trade‐off between the maximum bearing displacement and the first story ductility demand ratio. The results of extensive numerical analysis verify the effectiveness of the multiple‐slider bearing in minimizing the damage from earthquake and protecting the soft first story from excessively large ductility demand. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of soil–structure interaction on seismic base isolation

The effects of soil–structure interaction on the performance of a nonlinear seismic base isolation system for a simple elastic structure are examined. The steady-state response of the system to harmonic excitation is obtained by use of the equivalent linearization method. Simple analytical expressions for the deformation of the base isolation system and of the superstructure at resonance are obtained in terms of an effective replacement oscillator characterized by amplitude-dependent frequency, damping ratio, and excitation. Numerical results suggest that the seismic response of a structure resting on an inelastic base isolation system may be larger when the flexibility of the soil is considered than the corresponding response obtained by ignoring the effects of soil–structure interaction. It is shown that, in the undamped case and in the absence of soil–structure interaction effects, a critical harmonic excitation exists beyond which the steady-state resonant response of the isolators and structure become unbounded.     

Passive and hybrid mitigation of potential near-fault inner pounding of a self-braking seismic isolator

A seismic isolated structure is usually a long-period structural system, which may encounter a low-frequency resonance problem when subjected to a near-fault earthquake that usually has a long-period pulse-like waveform. This long-period wave component may result in an enlargement of the base displacement and a decrease of the isolation efficiency. To overcome this problem, a rolling-based seismic isolator, referred to as roll-n-cage (RNC) isolator, has been recently proposed. The RNC isolator has a built-in buffer (braking) mechanism that limits the peak isolator displacements under severe earthquakes and prevents adjacent structural pounding. This paper addresses the problem of passive and hybrid mitigation of the potential inner pounding of the self-braking RNC isolator under near-fault earthquakes. Numerical results show that the RNC isolator can intrinsically limit the isolator displacements under near-fault earthquakes with less severe inner pounding using additional hysteretic damping and active control forces.     

橡胶座非线性弹性拉伸特性的理论和试验研究

本文系统地研究分析了橡胶隔震支座(简称橡胶座)拉伸相关的基础理论,提出了原点拉伸纵弹性模量、拉伸刚度因子、原点拉伸刚度、偏拉原点刚度等基本概念,还提出了计算橡胶座非线性段拉伸刚度的双刚度和原点拉伸刚度应力应变模型等理论。基于原点拉伸刚度和偏拉原点刚度,提出了预测橡胶座的拉伸变形量计算理论。针对新提出的基本概念和计算理论采用低弹性天然橡胶和铅芯橡胶座原型试件进行了试验研究工作,结果表明本文建立的计算理论能够较理想地定量分析橡胶座拉伸相关的刚度和变形特性。     

Tri-directional shaking table tests of vibration sensitive equipment with static dynamics interchangeable-ball pendulum system

<正>Recently,the high-tech industry has become a key industry for economic development in many countries. However,vibration sensitive equipment located in these industrial buildings is vulnerable during earthquakes,which may cause huge economic loss.In this study,an innovative isolator for safeguarding the vibration sensitive equipment,namely, the static dynamics interchangeable-ball pendulum system(SDI-BPS) is proposed and investigated to examine its protective capability for the vibration sensitive equipment during earthquakes through a series of tri-directional shaking table tests.The experimental results illustrate that the SDI-BPS isolator can provide significant damping to rolling types of base isolation systems for reducing the bearing displacement and size,and avoid the stress concentration,which can cause damage or scratches on the rolling surface of the isolator,to prolong its life span of service.The SDI-BPS isolator also provides excellent capability in protecting the vibration sensitive equipment and exhibits a stable behavior under long terms of service loadings and earthquakes.     

Optimal design of friction pendulum system properties for isolated structures considering different soil conditions

This study aims at evaluating the optimal properties of friction pendulum bearings to be employed for the seismic protection of elastic isolated structural systems under earthquake excitations with different characteristics in terms of frequency content. A two-degree-of-freedom model is considered to describe the isolated system behavior while accounting for the superstructure flexibility and a non-dimensional formulation of the governing equations of motion is employed to relate the characteristic parameters describing the isolator and structure properties to the response parameters of interest for the performance assessment. Seismic excitations are modeled as time-modulated filtered Gaussian white noise random processes of different intensity within the power spectral density method. The filter parameters control the frequency content of the random excitations and are calibrated to describe stiff, medium and soft soil conditions, respectively. Finally, multi-variate regression expressions are obtained for the optimum values of the friction coefficient that minimize the superstructure displacements relative to the base mass as a function of the structural system properties, of the seismic input intensity and of the soil condition.     

Relaxation base seismic isolator

This paper deals with the use, for seismic applications, of a Maxwell element in parallel with a low damping isolator. The study of the properties of the frequency response function shows that this isolator is capable to reduce the base displacement of isolated structures with no considerable amplification of the non‐isolated modes. This is, also, confirmed by the floor response spectra under earthquake excitations. Hence, the previously mentioned isolator does not present the drawbacks met when base displacement is reduced by increasing damping. Moreover, it seems that its performance is comparable with that of more elaborated and expensive techniques combining passive and semi‐active devices. Copyright © 2016 John Wiley & Sons, Ltd.     

具有防雷功能的风信号传送器

雷击是自动气象站采集器被损坏的主要原因之一,特别是经风杆引入雷电损坏采集器的情况极为常见。解决此问题最好的办法是在保证数据接收准确的情况下,从物理连接(包括信号线和电源线)上将风传感器和采集器断开。设计了一款具有防雷功能的气象站风信号光纤传送器,解决了风杆引雷损坏采集器的问题。传送器采用EDA技术设计电路将风信号从传感器经过光纤传送至采集器,并使用防雷电源单独为传感器供电。经测试该传送器在保护了采集器免遭雷击的同时,又保证了数据的准确性,具有很好推广应用价值。     

Nonlinear dynamic analysis of multi-base seismically isolated structures with uplift potential Ⅰ:formulation

The complexity of modern seismically isolated structures requires the analysis of the structural system and the isolation system in its entirety and the ability to capture potential discontinuous phenomena such as isolator uplift and their effects on the superstructures and the isolation hardware.In this paper,an analytical model is developed and a computational algorithm is formulated to analyze complex seismically isolated superstructures even when undergoing highly-nonlinear phenomena such as uplift.T...     

Experimental and analytical studies of structures seismically isolated with an uplift‐restraining friction pendulum system

This paper presents findings from a comprehensive analytical and experimental study on the uplift‐restraining XY‐FP sliding isolation system. To investigate the effectiveness of the XY‐FP isolator and provide a rational basis for evaluating the efficacy of the developed mathematical model, an extensive experimental program was conducted on the earthquake simulator at the University at Buffalo. The experimental program involved a slender, five‐storey, scale‐model frame seismically isolated with four XY‐FP isolators subjected to simulations of historical horizontal and vertical ground motions. The experimental response demonstrates the validity of the concept and provides evidence for the effectiveness of the XY‐FP isolator in preventing uplift. A comprehensive analytical model capable of emulating the mechanical behaviour of the XY‐FP isolator is developed and implemented in program 3D‐BASIS‐ME. The newly enhanced program is used to predict the dynamic response of the seismically‐isolated model structure. Comparison of analytical predictions with experimental results attests to the efficacy of the analytical model for simulating the response of the XY‐FP isolator. With its appealing conceptual simplicity and its proven effectiveness, the new uplift‐restraining isolator has the potential to facilitate the application of seismic isolation even under the most extreme of conditions, including but not limited to near‐fault strong ground motions and uplift‐prone structural systems. Copyright © 2005 John Wiley & Sons, Ltd.