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1.
为评估隔震和非隔震支座对桥梁地震易损性的影响,以一座3跨连续混凝土箱梁桥为分析对象,首先建立采用铅芯橡胶隔震支座与非隔震型盆式橡胶支座下桥梁的数值模型,求得不同程度地震作用下墩顶与支座的最大位移响应;再定义转角延性比损伤指标,结合支座剪应变,分析桥墩和支座的地震易损性情况;最后通过宽界限法建立全桥地震易损性曲线。研究结果表明,支座是较容易发生损坏的构件,而桥梁系统比桥墩或支座更易发生破坏,同时铅芯橡胶支座的破坏概率明显低于非隔震型盆式支座,可见采用隔震支座能有效减小桥墩墩顶在地震作用下的最大位移,此时桥墩地震易损性优于采用非隔震支座的情况。 相似文献
2.
While isolation can provide significantly enhanced performance compared to fixed‐base counter parts in design level or even maximum considered level earthquakes, there is still uncertainty over the performance of isolation systems in extreme events. Researchers have looked at component level stability of rubber bearings and on the effect of moat impact on behavior of structures isolated on general bilinear isolators. However, testing of triple friction pendulum (TFP) sliding bearings has not been done dynamically or incorporated into a building system. Here, one‐third scale laboratory tests were conducted to on a 2‐story 2‐bay TFP‐isolated structure. Input motions were increasingly scaled until failure occurred at the isolation level. As the superstructure was designed with a yield force equivalent to the force of the bearing just at their ultimate displacement capacity, there was minimal yielding. A numerical model is presented to simulate the isolated building up to and including bearing failure. Forces transferred to the superstructure in extreme motions are examined using both experimental and numerical data. Additionally, the effect of the hardening stage of the TFP bearing is evaluated using the numerical model, finding slight benefits. 相似文献
3.
The force–displacement behavior of the Friction Pendulum? (FP) bearing is a function of the coefficient of sliding friction, axial load on the bearing and effective radius of the sliding surface. The coefficient of friction varies during the course of an earthquake with sliding velocity, axial pressure and temperature at the sliding surface. The velocity and axial pressure on the bearing depend on the response of the superstructure to the earthquake shaking. The temperature at an instant in time during earthquake shaking is a function of the histories of the coefficient of friction, sliding velocity and axial pressure, and the travel path of the slider on the sliding surface. A unified framework accommodating the complex interdependence of the coefficient of friction, sliding velocity, axial pressure and temperature is presented for implementation in nonlinear response‐history analysis. Expressions to define the relationship between the coefficient of friction and sliding velocity, axial pressure, and temperature are proposed, based on available experimental data. Response‐history analyses are performed on FP bearings with a range of geometrical and liner mechanical properties and static axial pressure. Friction is described using five different models that consider the dependence of the coefficient of friction on axial pressure, sliding velocity and temperature. Frictional heating is the most important factor that influences the maximum displacement of the isolation system and floor spectral demands if the static axial pressure is high. Isolation system displacements are not significantly affected by considerations of the influence of axial pressure and velocity on the coefficient of friction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
本文对一基础隔震模型进行了软着陆保护振动台模拟地震动试验,展示了该隔震体系在发生水平向大变形条件下,在不同后备支座以及滑移面摩擦系数不同情况下,轴压力从承载支座向后备支座转移的情况。结果表明:软着陆隔震保护体系不仅保护了承载支座免遭大变形失稳破坏,同时还能提供摩擦阻尼,将隔震层位移和上部结构层间位移控制在允许范围内。文中对隔震层位移、上部结构最大层间位移及绝对加速度等进行了分析,所得理论曲线与试验拟合曲线吻合较好。具有很大的应用前景。 相似文献
5.
A procedure for the dynamic identification of the physical parameters of coupled base isolation systems is developed in the time domain. The isolation systems considered include high damping rubber bearings (HDRB) and low friction sliding bearings (LFSB). A bi‐linear hysteretic model is used alone or in parallel with a viscous damper to describe the behavior of the HDRB system, while a constant Coulomb friction device is used to model the LFSB system. After deriving the analytical dynamical solution for the coupled system under an imposed initial displacement, this is used in combination with the least‐squares method and an iterative procedure to identify the physical parameters of a given base isolation system belonging to the class described by the models considered. Performance and limitations of the proposed procedure are highlighted by numerical applications. The procedure is then applied to a real base isolation system using data from static and dynamic tests performed on a building at Solarino. The results of the proposed identification procedure have been compared to available laboratory data and the agreement is within ±10%. However, the need for improvement both in models and testing procedures also emerges from the numerical applications and results obtained. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
6.
基于动力学基本原理,建立非规则桥梁的多自由度动力简化模型,根据拉格朗日方程推导简化模型的动力方程,结合龙格—库塔方法,采用自编程序研究行波激励下非规则桥梁综合考虑支座摩擦滑移、结构碰撞等非线性因素作用时的抗震性能。结果表明,行波效应和碰撞效应的共同作用可使矮墩的弯矩需求增大;行波激励可使板式橡胶支座位移增大,地震波最后到达的桥墩其上方支座位移峰值增加最为明显;相比高墩,地震作用下矮墩上部的板式橡胶支座易发生滑动。因此非规则桥梁进行防碰撞设计时应考虑行波激励及支座摩擦,找出相邻结构的最大碰撞力,以指导设计。 相似文献
7.
For the purpose of accurately predicting the seismic response of base-isolated structures, an analytical hysteresis model for elastomeric seismic isolation bearings is proposed. An extensive series of experimental tests of four types of seismic isolation bearings—two types of high-damping rubber bearings, one type of lead-rubber bearing and one type of silicon rubber bearing—was carried out with the objective of fully identifying their mechanical characteristics. The proposed model is capable of well-predicting the mechanical properties of each type of elastomeric bearing into the large strain range. Earthquake simulator tests were also conducted after the loading tests of the individual bearings. In order to show the validity of the proposed model, non-linear dynamic analyses were conducted to simulate the earthquake simulator test results. Good agreement between the experimental and analytical results shows that the model can be an effective numerical tool to predict not only the peak response value but also the force–displacement relationship of the isolators and floor response spectra for isolated structures. © 1997 by John Wiley & Sons, Ltd. 相似文献
8.
Response of hybrid isolation system during a shake table experiment of a full‐scale isolated building 
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下载免费PDF全文 Keri L. Ryan Taichiro Okazaki Camila B. Coria Eiji Sato Tomohiro Sasaki 《地震工程与结构动力学》2018,47(11):2214-2232
A full‐scale 5‐story steel moment frame building was subjected to a series of earthquake excitations using the E‐Defense shake table in August, 2011. For one of the test configurations, the building was seismically isolated by a hybrid system of lead‐rubber bearings and low friction roller bearings known as cross‐linear bearings, and was designed for a very rare 100 000‐year return period earthquake at a Central and Eastern US soil site. The building was subject to 15 trials including sinusoidal input, recorded motions and simulated earthquakes, 2D and 3D input, and a range of intensities including some beyond the design basis level. The experimental program was one of the first system‐level full‐scale validations of seismic isolation and the first known full‐scale experiment of a hybrid isolation system incorporating lead‐rubber and low friction bearings. Stable response of the hybrid isolation system was demonstrated at displacement demands up to 550 mm and shear strain in excess of 200%. Torsional amplifications were within the new factor stipulated by the code provisions. Axial force was observed to transfer from the lead‐rubber bearings to the cross‐linear bearings at large displacements, and the force transfer at large displacements exceeded that predicted by basic calculations. The force transfer occurred primarily because of the flexural rigidity of the base diaphragm and the larger vertical stiffness of the cross‐linear bearings relative to the lead‐rubber bearings. 相似文献
9.
针对隔震改造后叠层橡胶隔震支座与地下室下支柱组成的串联隔震体系的地震稳定性问题,采用理论推导与数值模拟方法开展系统研究。将叠层橡胶支座简化为一种具有水平刚度和抗弯刚度的特殊铰支座,RC柱简化为弯曲型竖杆,建立橡胶支座和RC柱串联隔震体系的理论模型,推导地下室下支柱的临界承载力方程;通过实际案例求解出该串联隔震体系的临界承载力具体表达式,并对典型参数的影响进行分析;采用数值模拟方法建立下支柱截面尺寸不同的6种柱顶隔震模型,对下支柱柱顶、隔震支座、下支柱与隔震支座串联后整体位移响应以及上部结构层间位移角响应进行对比分析。结果表明：所推导的临界承载力表达式变化规律与柱顶隔震设计模型数值模拟相一致;下支柱截面增大对上部结构和隔震支座的动力响应影响并不明显,但是可以明显减小下支柱的位移;在既有建筑隔震改造实际工程中,增加下支柱的截面尺寸是保证下部结构的抗震能力高于上部结构既简单且行之有效的方法,但实际工程中截面增量普遍较大且偏于保守,造成了一定的浪费。 相似文献
10.
Evgueni T. Filipov Jessica R. Revell Larry A. Fahnestock James M. LaFave Jerome F. Hajjar Douglas A. Foutch Joshua S. Steelman 《地震工程与结构动力学》2013,42(9):1375-1394
Modern highway bridges in Illinois are often installed with economical elastomeric bearings that allow for thermal movement of the superstructure, and steel fixed bearings and transverse retainers that prevent excessive movement from service‐level loadings. In the event of an earthquake, the bearing system has the potential to provide a quasi‐isolated response where failure of sacrificial elements and sliding of the bearings can cause a period elongation and reduce or cap the force demands on the substructure. A computational model that has been calibrated for the expected nonlinear behaviors is used to carry out a parametric study to evaluate quasi‐isolated bridge behavior. The study investigates different superstructure types, substructure types, substructure heights, foundation types, and elastomeric bearing types. Overall, only a few bridge variants were noted to unseat for design‐level seismic input in the New Madrid Seismic Zone, indicating that most structures in Illinois would not experience severe damage during their typical design life. However, Type II bearing systems, which consist of an elastomeric bearing and a flat PTFE slider, would in some cases result in critical damage from unseating at moderate and high seismic input. The sequence of damage for many bridge cases indicates yielding of piers at low‐level seismic input. This is caused by the high strength of the fixed bearing element, which justifies further calibration of the quasi‐isolation design approach. Finally, the type of ground motion, pier height, and bearing type were noted to have significant influence on the global bridge response. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
11.
The dynamic analysis of sliding structures is complicated due to the presence of friction. Synchronization of the kinematics of all the isolation bearings is often granted to simplify the task. This, however, may lead to inaccurate prediction of the structural responses under certain circumstances. Stepped structures or continuous bridges with seismic isolation are notable examples where unsynchronized bearing motions are expected. In this paper, a logically simple and numerically efficient procedure is proposed to solve the dynamic problem of sliding systems with unsynchronized support motions. The motion equations for the sliding and non‐sliding modes of the isolated structure are unified into a single equation that is represented as a difference equation in a discrete‐time state‐space form and the base shear forces between the sliding interfaces can be determined through simple matrix algebraic analysis. The responses of the sliding structure can be obtained recursively from the discrete‐time version of the motion equation with constant integration time step even during the transitions between the non‐sliding and sliding phases. Therefore, both accuracy and efficiency in the dynamic analysis of the highly non‐linear system can be enhanced to a large extent. Rigorous assessment of seismic structures with unsynchronized support motions has been carried out for both a stepped structure and a continuous bridge. Effectiveness of friction pendulum bearings for earthquake protection of such structures has been verified. Moreover, evident unsynchronized sliding motions of the friction bearings have been observed, confirming the necessity to deal with each of the bearings independently in the analytical model. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
12.
This paper presents a non‐linear, kinematic model for triple friction pendulum isolation bearings. The model, which incorporates coupled plasticity and circular restraining surfaces for all sliding surfaces, is capable of capturing bi‐directional behavior and is able to explicitly track the movement of each internal component. The model is general so that no conditions regarding bearing properties, which effect the sequence of sliding stages, are required for the validity of the model. Controlled‐displacement and seismic‐input experiments were conducted using the shake table at the University of California, Berkeley to assess the fidelity of the proposed model under bi‐directional motion. Comparison of the experimental data with the corresponding results of the kinematic model shows good agreement. Additionally, experiments showed that the performance of TFP bearings is reliable over many motions, and the behavior is repeatable even when initial slider offsets are present. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
13.
The nuclear accident at Fukushima Daiichi in March 2011 has led the nuclear community to consider seismic isolation for new large light water and small modular reactors to withstand the effects of beyond design basis loadings, including extreme earthquakes. The United States Nuclear Regulatory Commission is sponsoring a research project that will quantify the response of low damping rubber (LDR) and lead rubber (LR) bearings under loadings associated with extreme earthquakes. Under design basis loadings, the response of an elastomeric bearing is not expected to deviate from well‐established numerical models, and bearings are not expected to experience net tension. However, under extended or beyond design basis shaking, elastomer shear strains may exceed 300% in regions of high seismic hazard, bearings may experience net tension, the compression and tension stiffness will be affected by isolator lateral displacement, and the properties of the lead core in LR bearings will degrade in the short‐term because of substantial energy dissipation. New mathematical models of LDR and LR bearings are presented for the analysis of base isolated structures under design and beyond design basis shaking, explicitly considering both the effects of lateral displacement and cyclic vertical and horizontal loading. These mathematical models extend the available formulations in shear and compression. Phenomenological models are presented to describe the behavior of elastomeric isolation bearings in tension, including the cavitation and post‐cavitation behavior. The elastic mechanical properties make use of the two‐spring model. Strength degradation of LR bearing under cyclic shear loading due to heating of lead core is incorporated. The bilinear area reduction method is used to include variation of critical buckling load capacity with lateral displacement. The numerical models are coded in OpenSees, and the results of numerical analysis are compared with test data. The effect of different parameters on the response is investigated through a series of analyses. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
14.
Experimental study of the effect of restraining rim design on the extreme behavior of pendulum sliding bearings 下载免费PDF全文
下载免费PDF全文 《地震工程与结构动力学》2018,47(4):906-924
While the performance of sliding isolators has been extensively validated under typical levels of ground motion, there have been very few experimental studies on the extreme behavior of sliding isolation bearings when the displacement limit is reached. However, to appropriately design isolated systems, from selecting the displacement capacity of the bearing to sizing the superstructure members, the behavior of the bearing as it reaches, and in some cases exceeds, the displacement limit should be well understood. A series of shake table tests to investigate the extreme behavior of double pendulum sliding bearings under strong ground motions were conducted at McMaster University. One major difference in sliding bearings around the world is how the motion of the bearing is restrained at the bearing's displacement capacity. Scaled bearings with four different types of restraining rim designs were included, representing typical sliding restraining rims found in Europe, Japan, and the United States. Experimental observation shows that the restraining rim has a significant influence on the extreme behavior of sliding isolation bearing. Key response parameters such as impact force and uplift are evaluated and compared between the different sliding bearing designs. While the bearing with no rim bearing imparts the lowest forces to the superstructure, it loses its functionality at a lower amplitude input than all the other rim types. For the other rim designs, the impact forces are significantly higher but they remained operational although damaged. 相似文献
15.
In this paper the seismic response of isolated structures supported on bearings with bilinear and trilinear behavior is revisited with dimensional analysis in an effort to better understand the relative significance of the various parameters that control the mechanical behavior of isolation systems. An isolation system that consists of lead rubber bearings or of single concave spherical sliding bearings exhibits bilinear behavior; whereas, when a double concave configuration is used the behavior is trilinear. For the case of bilinear behavior it is well known that the value of the normalized yield displacement is immaterial to the response of the isolated superstructure—or, in mathematical terms, that the response of the bilinear oscillator exhibits complete similarity in the dimensionless yield displacement. Similarly, for the case of trilinear behavior the paper shows that the presence of the intermediate slope is immaterial to the peak response of most isolated structures—a finding that shows the response of the trilinear oscillator exhibits a complete similarity in the difference between the coefficients of friction along the two sliding surfaces as well as in the ratio of the intermediate to the final slope. This finding implies that even when the coefficients of friction of the two sliding surfaces are different, the response of isolated structures for most practical configurations can be computed with confidence by replacing the double concave spherical bearings with single concave spherical bearings with an effective radius of curvature and an effective coefficient of friction. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
针对结构隔震装置在较大的倾覆力作用下抗拉能力不足的问题,提出了一种带有楔形分离式轨道的新型滑移支座。新支座能够承受上部结构传递的荷载以及适应较大水平位移,同时利用楔形轨道与楔形滑块之间的相互作用提供抗拉能力。采用通用有限元程序ABAQUS建立了支座的三维实体有限元模型,对其抗压、抗拉、压剪和拉剪力学性能进行数值模拟研究,同时考虑了楔形角度的改变对支座力学性能的影响。通过分析表明:在竖向新支座具有较好的抗压和抗拉能力,抗拉性能受楔形角度的影响较大,角度大于60°时,支座的抗拉能力随着角度的减小不断提升;而当角度减小到60°时,楔形滑块与上部连接部分出现薄弱点,导致支座的抗拉能力开始降低。在压剪与拉剪的作用下,支座水平向的滞回曲线比较饱满,具有较好的水平向摩擦耗能能力且能够适应较大的水平位移。 相似文献
17.
Investigation of the seismic response of high‐rise buildings supported on tension‐resistant elastomeric isolation bearings 下载免费PDF全文
下载免费PDF全文 In many applications of seismic isolation, such as in high‐rise construction, lightweight construction, and structures with large height‐to‐width aspect ratios, significant tension forces can develop in bearings, raising concerns about the possible rupture of elastomeric bearings and the uplift of sliding bearings. In this paper, a novel tension‐resistant lead plug rubber bearing (TLRB) with improved tension‐resisting capabilities is developed and experimentally and numerically assessed. This TLRB consists of a common lead plug rubber bearing (LRB) and several helical springs. After describing the theory underlying the behavior of the TLRB, the mechanical properties of reduced‐scale prototype bearings are investigated through extensive horizontal and vertical loading tests. The test results indicate that TLRBs can improve the shear stiffness and tension resistance capacity even under significant tensile loads. A series of shaking table tests on scaled models of high‐rise buildings with different aspect ratios were conducted to investigate the dynamic performance of the TLRB and the seismic responses of base‐isolated high‐rise buildings. Three different cases were considered in the shaking table tests: a fixed base condition and the use of TLRB and LRB isolation systems. The results of the shaking table test show that (a) base‐isolated systems are effective in reducing the structural responses of high‐rise buildings; (b) an isolated structure's aspect ratio is an important factor influencing its dynamic response; (c) TLRBs can endure large tensile stresses and avoid rupture on rubber bearings under strong earthquakes; and (d) the experimental and numerical results of the responses of the models show good agreement. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
以一座典型山区非规则梁桥为研究对象,建立了该桥梁多维多点激励下的多自由度动力计算模型,研究了该桥梁在多维多点激励下考虑支座摩擦滑移及结构碰撞等非线性因素时的抗震性能。研究结果表明:相比一维地震输入,多维地震可使结构的动力响应增加,桥墩底部弯矩需求增大;相比一致激励,多点激励可使得支座的位移需求增大,且地震波最后到达的桥墩上方支座位移最大;同时考虑多点激励和碰撞效应可使桥墩的弯矩需求增加;水平地震作用下,矮墩上部的支座容易滑动,且双向地震较单向地震更明显,三向地震输入较双向有所增强。因此,对山区非规则梁桥进行抗震设计时应有针对性地进行多维多点地震输入计算,找出结构的最大地震需求,以期指导设计。 相似文献
19.
Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPS) with numerous sliding interfaces.Based on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is proposed.The aim is to simulate the characteristics of sliding motions for an MFPS isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding stages.An MFPS with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the slider.The equivalent series system for the entire system is then obtained by connecting those for each subsystem in series.The equivalent series system is validated by comparing numerical results for an MFPS with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and Constantinou.Furthermore,these numerical results demonstrate that an MFPS isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms. 相似文献
20.
The accuracy of a series spring model to predict the peak displacement and displacement history of Triple Pendulum? (TP) bearings in a strongly shaken, full‐scale building is evaluated in this paper. The series spring model was implemented as a self‐contained three‐dimensional TP bearing element in OpenSees and is now available for general use. The TP bearing element contains the option for constant friction or a generalized friction model that accounts for the effect of instantaneous velocity and compression load on the friction coefficient. Comparison between numerical simulation and experimental data of a five‐story steel moment frame building shows that the peak displacement of isolation system can generally be predicted with confidence using a constant friction coefficient model. The friction coefficient model accounting for the effect of axial load and velocity leads to minor improvement over the constant friction coefficient models in some cases. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献