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1.
The implementation of viscous dampers to microelectronics factories has been previously proved not to affect the micro‐vibration of the factories in operation so that the vibration‐sensitive manufacturing process will not be interfered. Therefore, a seismic retrofit strategy which employs the viscous dampers installed in between the exterior and interior structures of the ‘fab’ structure is proposed in the study. The design formulas corresponding to the proposed retrofit method are derived using the non‐proportional damping theory. Based on the study, it is found that the added damping ratio to the fab structure depends greatly on the frequency ratio of the two structures in addition to the damping coefficients of the added dampers. Outside the bandwidth of the frequency ratio in which the added damping ratio is very sensitive to the variation of the frequency ratio, the added damping ratio can be well captured using the classical damping theory. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
Damage investigation of small to medium-span highway bridges in Wenchuan earthquake revealed that typical damage of these bridges included: sliding between laminated-rubber bearings and bridge girders, concrete shear keys failure, excessive girder displacements and even span collapse. However, the bearing sliding could actually act as a seismic isolation for piers, and hence, damage to piers for these bridges was minor during the earthquake. Based on this concept, an innovative solation system for highway bridges with laminated-rubber bearings is developed. The system is comprised of typical laminated-rubber bearings and steel dampers. Bearing sliding is allowed during an earthquake to limit the seismic forces transmitting to piers, and steel dampers are applied to restrict the bearing displacements through hysteretic energy dissipation. As a major part of this research, a quarter-scale, two-span bridge model was constructed and tested on the shake tables to evaluate the performance of this isolation system. The bridge model was subjected to a Northridge and an artificial ground motion in transverse direction. Moreover, numerical analyses were conducted to investigate the seismic performance of the bridge model. Besides the test bridge model, a benchmark model with the superstructure fixed to the substructure in transverse direction was also included in the numerical analyses. Both the experimental and the numerical results showed high effectiveness of this proposed isolation system in the bridge model. The system was found to effectively control the pier-girder relative displacements, and simultaneously, protect the piers from severe damage. Numerical analyses also validated that the existing finite element methods are adequate to estimate the seismic response of bridges with this isolation system. 相似文献
3.
大跨斜拉桥的近断层地震响应及减震控制 总被引：2，自引：0，他引：2
近断层地震长周期成分丰富,存在速度大脉冲效应;而大跨度斜拉桥一般采用半漂浮体系或漂浮体系,所以固有频率较低。为了研究大跨度斜拉桥在近断层地震作用下的反应规律及减震措施,利用ANSYS软件分析了某半漂浮体系的大跨斜拉桥在近断层地震作用下的时程响应,并对其减震控制方法进行了探讨。研究表明,大跨度斜拉桥的近断层地震响应随着PGV/PGA值的增大而增大,且增大幅度较大,近场脉冲效应较为显著;对于近断层地震作用,不建议采用塔梁弹性连接装置作为主梁纵漂的减震措施,而采用参数适宜的铅挤压阻尼器和粘滞阻尼器则均能获得很好的减震效果;由于大跨度斜拉桥的近断层地震反应较大,应提高其支座的设计允许位移。 相似文献
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5.
Passive supplemental damping in a seismically isolated structure provides the necessary energy dissipation to limit the isolation system displacement. However, damper forces can become quite large as the passive damping level is increased, resulting in the requirement to transfer large forces at the damper connections to the structure which may be particularly difficult to accommodate in retrofit applications. One method to limit the level of damping force while simultaneously controlling the isolation system displacement is to utilize an intelligent hybrid isolation system containing semi-active dampers in which the damping coeffic ient can be modulated. The effectiveness of such a hybrid seismic isolation system for earthquake hazard mitigation is investigated in this paper. The system is examined through an analytical and computational study of the seismic response of a bridge structure containing a hybrid isolation system consisting of elastomeric bearings and semi-active dampers. Control algorithms for operation of the semi-active dampers are developed based on fuzzy logic control theory. Practical limits on the response of the isolation system are considered and utilized in the evaluation of the control algorithms. The results of the study show that both passive and semi-active hybrid seismic isolation systems consisting of combined base isolation bearings and supplemental energy dissipation devices can be beneficial in reducing the seismic response of structures. These hybrid systems may prevent or significantly reduce structural damage during a seismic event. Furthermore, it is shown that intelligent semi-active seismic isolation systems are capable of controlling the peak deck displacement of bridges, and thus reducing the required length of expansion joints, while simultaneously limiting peak damper forces. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
6.
Many highway bridges were severely damaged or completely collapsed during the 2008 Wenchuan earthquake.A field investigation was carried out in the strongly affected areas and over 320 bridges were examined. Damage to some representative highway bridges is briefly described and a preliminary analysis of the probable causes of the damage is presented in this paper. The most common damage included shear-flexural failure of the pier columns, expansion joint failure, shear key failure, and girder sliding in the transversal or longitudinal directions due to weak connections between girder and bearings. Lessons learned from this earthquake are described and recommendations related to the design of curved and skewed bridges, design of bearings and devices to prevent girder collapse, and ductility of bridge piers are presented.Suggestions for future seismic design and retrofitting techniques for bridges in moderate to severe earthquake areas are also proposed. 相似文献
7.
斜拉桥结构减震设计优化研究 总被引：3，自引：0，他引：3
位于中强以上地震烈度区的大跨斜拉桥结构,如果采用传统的抗震设计方法,通常很难满足结构的抗震设计要求,因此采取一定的减震措施显得非常必要。本文以某一总长为2 088m的大跨双塔双索面斜拉桥为分析算例,对斜拉桥结构的减震设计进行了研究。合理的减震结构体系是取得良好减震效果的前提,通过分析对比,该大跨斜拉桥横向采用局部减震体系最为合理,即只在近塔辅助墩处设置横向粘滞阻尼器,其它塔、墩处采用常规的横向约束方案。为使减震结构得到更好的减震效果,还应对减震装置参数进行优化设计。由于采取了合理的减震结构体系、较优的减震装置参数,使该大跨斜拉桥取得了很好的减震设计效果。 相似文献
8.
A simplified design procedure (SDP) for preliminary seismic design of frame buildings with structural dampers is presented. The SDP uses elastic‐static analysis and is applicable to structural dampers made from viscoelastic (VE) or high‐damping elastomeric materials. The behaviour of typical VE materials and high‐damping elastomeric materials is often non‐linear, and the SDP idealizes these materials as linear VE materials. With this idealization, structures with VE or high‐damping elastomeric dampers can be designed and analysed using methods based on linear VE theory. As an example, a retrofit design for a typical non‐ductile reinforced concrete (RC) frame building using high‐damping elastomeric dampers is developed using the SDP. To validate the SDP, results from non‐linear dynamic time history analyses (NDTHA) are presented. Results from NDTHA demonstrate that the SDP estimates the seismic response with sufficient accuracy for design. It is shown that a non‐ductile RC frame building can be retrofit with high‐damping elastomeric dampers to remain essentially elastic under the design basis earthquake (DBE). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
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
10.
高烈度地震对铁路桥梁安全造成巨大隐患,且次生灾害将引起较大经济损失。该大跨连续梁桥所处地震带正进入活跃期,未来有发生较大规模强烈地震的可能,但桥梁自身不具备高烈度抗震能力,需利用粘滞阻尼器对其进行减震处理。采用斜向设置阻尼器并配合双曲面球型支座,来控制可能发生的纵向和横向地震。通过数值模拟进行阻尼器参数敏感性分析以及减震效果讨论,进而确定其最优设置方案。选取相关参数作为评价指标,对比加设阻尼器前后易损部位的地震响应,确定其在高烈度地震荷载激励下的减震效果。研究结果表明:在液体粘滞阻尼器的作用下,使得各墩协同受力,大大增加了结构的整体性,同时能很好弥补减隔震支座不能很好的控制上部结构位移的缺点,同时能降低罕遇地震力对桥墩的冲击损伤。因此,在高烈度区大跨度桥梁中更有必要设置阻尼器来抗震。 相似文献
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为研究不同设计参数对曲线梁桥地震响应的影响以指导结构抗震设计,对不同支承约束曲线梁桥地震响应及地震需求敏感性进行分析。采用增量动力分析（IDA）方法对比分析了不同支承约束曲线梁桥的结构地震响应变化趋势;采用Tornado图形法对不同结构参数影响程度进行了排序,找出了对结构地震需求影响显著的参数。结果表明:采用板式橡胶支座桥梁因支座易发生滑移而导致上部结构位移较大,但降低了下部结构响应,设置固定墩后,下部结构损伤显著增加;对于采用板式橡胶支座和铅芯橡胶支座的曲线梁桥,墩高及跨径对墩底曲率需求影响较大,而对于固定墩为墩梁固结形式和采用盆式橡胶支座的曲线梁桥,跨径及跨数对墩底曲率需求影响较大;对于采用不同支承约束的曲线梁桥,墩高和曲率半径对桥台位移需求影响较大,仅次于地震动参数PGA。 相似文献
12.
结构附加粘滞阻尼器的抗震设计 总被引：2，自引：0，他引：2
本文结合抗震设计规范反应谱,给出了一个附加非线性流体粘滞阻尼器结构的抗震设计方法。研究了非线性阻尼器的力学特性,引入了非线性流体阻尼器的等效线性阻尼比,给出了计算最大加速度时刻附加非线性流体阻尼器结构反应的荷载组合系数,提出了按阻尼力的水平力分量与楼层剪力成正比的原则分配阻尼器阻尼系数的方法。同时给出了基于抗震规范设计反应谱附加非线性阻尼器结构的设计流程,通过一个算例说明了使用该方法设计附加非线性粘滞阻尼器结构的全过程。算例分析表明,这种设计方法适合于手算,便于设计人员掌握,在初步设计阶段可以快速、有效地设计满足给定性能水平的附加非线性流体阻尼器体系。 相似文献
13.
A simplified seismic design procedure for steel portal frame piers installed with hysteretic dampers is proposed, which falls into the scope of performance‐based design philosophy. The fundamental goal of this approach is to design a suite of hysteretic damping devices for existing and new bridge piers, which will assure a pre‐defined target performance against future severe earthquakes. The proposed procedure is applicable to multi‐degree‐of‐freedom systems, utilizing an equivalent single‐degree‐of‐freedom methodology with nonlinear response spectra (referred to as strength‐demanded spectra) and a set of formulae of close‐form expressions for the distribution of strength and stiffness produced in the structure by the designed hysteretic damping devices. As an illustrative example, the proposed procedure is applied to a design of a simple steel bridge pier of portal frame type with buckling‐restrained braces (one of several types of hysteretic dampers). For the steel portal frame piers, an attempt is made to utilize not only the displacement‐based index but also the strain‐based index as pre‐determined target performance at the beginning of design. To validate this procedure, dynamic inelastic time‐history analyses are performed using the general‐purpose finite element program ABAQUS. The results confirm that the proposed simplified design procedure attains the expected performance level as specified by both displacement‐based and strain‐based indices with sufficient accuracy. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
14.
在大震或特大震下,黏滞阻尼器可能因某个极限状态的出现而发生破坏。现有在斜拉桥上设置黏滞阻尼器的研究多集中在阻尼器的参数优化上,很少考虑到阻尼器失效对斜拉桥抗震性能的影响。针对这一问题,以某三塔斜拉桥为背景,利用OpenSees平台建立斜拉桥有限元模型和可以考虑承载力及行程极限的黏滞阻尼器模型;分析黏滞阻尼器的阻尼系数和阻尼指数对斜拉桥地震响应的影响,确定阻尼器参数的取值;对不安装阻尼器、安装不考虑极限状态及考虑极限状态阻尼器等多种工况的斜拉桥进行非线性时程分析,对比各工况斜拉桥的地震响应。分析结果表明,在大震下,考虑极限状态阻尼器的耗能能力及减震效果将显著降低;不考虑阻尼器达到极限状态后失效的情况将高估耗能减震设计斜拉桥的抗震能力。 相似文献
15.
本文通过Maxwell模型模拟的黏滞阻尼器连接的2种不同相邻结构的地震反应分析,对阻尼器设置的位置和阻尼参数进行了同时优化。在El Centro波、Tianjin波和Taft波3种较典型的地震动作用下,分别对不同质量比和不同刚度比的主、子结构在无阻尼和有阻尼情况下进行了地震反应分析,并以主结构的顶层最大相对位移最小作为优化目标,寻求出最优的阻尼器摆放位置以及对应的最优阻尼系数。结果显示,当阻尼器选择合适的安放位置和合理的阻尼参数时,主、子结构的地震反应都会有一定程度的降低,从而收到较好的减震效果。 相似文献
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为研究适用于大跨铁路钢桁连续梁桥的减隔震方案及合理优化参数,以一座全长504 m的三跨铁路钢桁连续梁特大桥为工程背景,使用非线性结构分析软件SAP2000建立有限元模型,采用快速非线性分析方法分析对比摩擦摆、阻尼器、速度锁定器等减隔震方案在各种装置参数下的减震效率。研究表明:由于大跨铁路钢桁连续梁桥墩身自振导致的地震力较大,摩擦摆方案内力减震效率一般,同时墩底内力对滑动面半径变化并不敏感,在选取滑动半径时应更多地考虑行车平顺性和梁端位移值的限制。速度锁定器会极大地增加此类桥梁地震输入能量,不适用于此类桥型。阻尼器方案对活动墩内力减震效果明显,但不能有效降低固定墩内力。摩擦摆支座附加阻尼器组合减震方案能有效控制此类桥梁的内力和位移响应。研究结论可为大跨度钢桁连续梁桥减隔震设计提供参考。 相似文献
17.
针对地震作用下公路桥梁的碰撞问题,采用接触单元法模拟桥梁之间的碰撞作用,并在此基础上研究了采用磁流变阻尼器的公路桥梁碰撞的半主动控制方法。通过对某公路桥梁的数值模拟发现,地震作用下桥梁之间的相互碰撞,将大幅增加桥梁的绝对加速度响应。采用磁流变阻尼器的半主动控制系统能够较好地降低结构的地震响应和消除地震作用下的碰撞。 相似文献
18.
斜交桥梁由于其不规则的结构形式使其受力规律与规则桥梁相比具有特殊性和复杂性,在地震作用下梁体的平动与转动存在弯扭耦合效应,导致结构动力响应分析复杂。针对斜交桥梁的结构特点,建立包含桩土相互作用的三维有限元模型,在考虑水平双向地震作用下,采用反应谱法及时程分析法对京包高速公路某互通式斜交桥梁进行地震反应分析。结果表明:互通式简支斜交桥梁的地震响应受地震动输入方向的影响较大,在考虑碰撞效应后,碰撞涉及结构部位的地震位移显著增加,地震内力也出现较大差异,即说明在斜交桥梁抗震设计时有必要适当考虑地震动输入方向和梁端与墩台及相邻梁端的碰撞效应。 相似文献
19.
Seismic performance and probabilistic collapse resistance assessment of steel moment resisting frames with fluid viscous dampers 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Choung‐Yeol Seo Theodore L. Karavasilis James M. Ricles Richard Sause 《地震工程与结构动力学》2014,43(14):2135-2154
This paper evaluates the seismic resistance of steel moment resisting frames (MRFs) with supplemental fluid viscous dampers against collapse. A simplified design procedure is used to design four different steel MRFs with fluid viscous dampers where the strength of the steel MRF and supplemental damping are varied. The combined systems are designed to achieve performance that is similar to or higher than that of conventional steel MRFs designed according to current seismic design codes. Based on the results of nonlinear time history analyses and incremental dynamic analyses, statistics of structural and non‐structural response as well as probabilities of collapse of the steel MRFs with dampers are determined and compared with those of conventional steel MRFs. The analytical frame models used in this study are reliably capable to simulate global frame collapse by considering full geometric nonlinearities as well as the cyclic strength and stiffness deterioration in the plastic hinge regions of structural steel members. The results show that, with the aid of supplemental damping, the performance of a steel MRF with reduced design base shear can be improved and become similar to that of a conventional steel MRF with full design base shear. Incremental dynamic analyses show that supplemental damping reduces the probability of collapse of a steel MRF with a given strength. However, the paper highlights that a design base shear equal to 75% of the minimum design base shear along with supplemental damping to control story drift at 2% (i.e., design drift of a conventional steel MRF) would not guarantee a higher collapse resistance than that of a conventional MRF. At 75% design base shear, a tighter design drift (e.g., 1.5% as shown in this study) is needed to guarantee a higher collapse resistance than that of a conventional MRF. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
20.
This paper examines the eigenvalues of multi‐span seismically isolated bridges in which the transverse displacement of the deck at the end abutments is restricted. With this constraint the deck is fully isolated along the longitudinal direction, whereas along the transverse direction the deck is a simple‐supported beam at the end abutments which enjoys concentrated restoring forces from the isolation bearings at the center piers. For moderate long bridges, the first natural period of the bridge is the first longitudinal period, while the first transverse period is the second period, given that the flexural rigidity of the deck along the transverse direction shortens the isolation period offered by the bearings in that direction. This paper shows that for isolated bridges longer than a certain critical length, the first transverse period becomes longer than the first longitudinal period despite the presence of the flexural rigidity of the deck. This critical length depends on whether the bridge is isolated on elastomeric bearings or on spherical sliding bearings. This result is also predicted with established commercially available numerical codes only when several additional nodes are added along the beam elements which are modeling the deck in‐between the bridge piers. On the other hand, this result cannot be captured with the limiting idealization of a beam on continuous distributed springs (beam on Wrinkler foundation)—a finding that has practical significance in design and system identification studies. Finally, the paper shows that the normalized transverse eigenperiods of any finite‐span deck are self‐similar solutions that can be represented by a single master curve and are independent of the longitudinal isolation period or on whether the deck is supported on elastomeric or spherical sliding bearings. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献