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1.
This paper presents selected indicative results from an extensive parametric investigation that has been performed in order to assess the effects of potential earthquake‐induced poundings on the overall dynamic response of seismically isolated buildings. In particular, a seismically isolated building and its adjacent fixed‐supported buildings are subjected to various earthquake excitations that induce structural impact among the buildings in series. The results indicate that the seismically isolated building may hit against the adjacent buildings at the upper floor levels before the occurrence of any pounding at the isolation level with the surrounding moat wall. The severity of the impact depends on the dynamic properties of the adjacent buildings, in combination with the earthquake characteristics. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
2.
For the public welfare and safety, buildings such as hospitals, industrial facilities, and technology centers need to remain
functional at all times; even during and after major earthquakes. The values of these buildings themselves may be insignificant
when compared to the cost of loss of operations and business continuity. Seismic isolation aims to protect both the integrity
and the contents of a structure. Since the tolerable acceleration levels are relatively low for continued services of vibration-sensitive
high-tech contents, a better understanding of acceleration response behaviors of seismically isolated buildings is necessary.
In an effort to shed light to this issue, following are investigated via bi-directional time history analyses of seismically
isolated benchmark buildings subject to historical earthquakes: (i) the distribution of peak floor accelerations of seismically
isolated buildings subject to seismic excitations in order to find out which floors are likely to sustain the largest accelerations;
(ii) the influence of equivalent linear modeling of isolation systems on the floor accelerations in order to find out the
range of possible errors introduced by this type of modeling; (iii) the role of superstructure damping in reducing floor accelerations
of seismically isolated buildings with flexible superstructures in order to find out whether increasing the superstructure
damping helps reducing floor accelerations notably. Influences of isolation system characteristics and superstructure flexibility
are both taken into account. 相似文献
3.
Optimized earthquake response of multi‐storey buildings with seismic isolation at various elevations
The response of multi‐storey structures can be controlled under earthquake actions by installing seismic isolators at various storey levels. By vertically distributing isolation devices at various elevations, the designer is provided with numerous options to appropriately adjust the seismic performance of a building. However, introducing seismic isolators at various storey levels is not a straightforward task, as it may lead to favourable or unfavourable structural behaviour depending on a large number of factors. As a consequence, a rather chaotic decision space of seismic isolation configurations arises, within which a favourable solution needs to be located. The search for favourable isolators' configurations is formulated in this work as a single‐objective optimization task. The aim of the optimization process is to minimize the maximum floor acceleration of the building under consideration, while constraints are specified to control the maximum interstorey drift, the maximum base displacement and the total seismic isolation cost. A genetic algorithm is implemented to perform this optimization task, which selectively introduces seismic isolators at various elevations, in order to identify the optimal configuration for the isolators satisfying the pre‐specified constraints. This way, optimized earthquake response of multi‐storey buildings can be obtained. The effectiveness of the proposed optimization procedure in the design of a seismically isolated structure is demonstrated in a numerical study using time‐history analyses of a typical six‐storey building. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
4.
Shear building representations of seismically isolated buildings 总被引：2，自引：0，他引：2
Seismic isolation, with its capability of reducing floor accelerations and interstory drifts simultaneously, is recognized
as an earthquake resistant design method that protects contents of a building along with the building itself. In research
studies, superstructures of seismically isolated buildings are commonly modeled as idealized shear buildings. Shear building
representation corresponds to an idealized structure where the beams are infinitely stiff in flexure and axially inextensible;
columns are axially inextensible; and rigid floors are supported on these columns. Although it is more convenient to model
and analyze a shear building, such an idealization may influence the seismic responses of seismically isolated buildings.
This study presents a comparison of the seismic performances of seismically isolated buildings with superstructures modeled
as shear buildings to those with full three dimensional superstructures. Both linear and nonlinear base isolation systems
with different isolation periods and superstructures with different number of stories are considered. 相似文献
5.
Effectiveness of a new semiactive independently variable stiffness (SAIVS) device in reducing seismic response of sliding base isolated buildings is evaluated analytically and experimentally. Through analytical and experimental study of force—displacement behaviour of the SAIVS device, it is shown that the device can vary stiffness continuously and smoothly between minimum and maximum stiffness. Passive sliding base isolation systems reduce interstorey drifts and superstructure accelerations, but with increased base displacements, which is undesirable, under large velocity near fault pulse type earthquakes. It is a common practice to incorporate non‐linear passive dampers into the isolation system to reduce bearing displacements. Incorporation of passive dampers, however, may result in increased superstructure accelerations and drifts; while, properly designed passive dampers can be beneficial. A viable alternative is to use semiactive variable stiffness systems, which can vary the period of the sliding base isolated buildings in real time, to simultaneously reduce bearing displacements and superstructure responses further than the passive systems, which deserves investigation. This study investigates the performance of a 1:5 scaled smart sliding base isolated building model equipped with the SAIVS device analytically and experimentally, under near fault earthquakes, by developing a new moving average non‐linear tangential stiffness control algorithm for control of the SAIVS device. The SAIVS device reduces bearing displacements further than the passive cases, while maintaining isolation level forces and superstructure responses at the same level as the passive minimum stiffness case, indicating the significant potential of the SAIVS system. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
传统的动力弹塑性分析法在研究剪力墙的抗震性能时,忽略了对剪力墙转换结构关键结点的有效分析,导致建筑抗震性研究结果存在局限性。提出剪力墙转换结构关键结点对建筑抗震性能影响的分析方法。塑造剪力墙转换结构平面布置图,确定剪力墙转换结构关键结点,分析剪力墙转换结构关键结点的层间位移与位移角和关键结点处的楼层剪力,关键结点位置上升使得最大楼层的位移减小、位移角也逐渐变小。根据关键结点处于不同楼层时层间位移、位移角以及受力作用的不同,获取建筑结构上下层刚度的波动。实验结果说明,所提方法能够高精度、高效的对建筑抗震性能进行分析。 相似文献
7.
A comprehensive parametric study on the inelastic seismic response of seismically isolated RC frame buildings, designed for gravity loads only, is presented. Four building prototypes, with 23 m × 10 m floor plan dimensions and number of storeys ranging from 2 to 8, are considered. All the buildings present internal resistant frames in one direction only, identified as the strong direction of the building. In the orthogonal weak direction, the buildings present outer resistant frames only, with infilled masonry panels. This structural configuration is typical of many existing RC buildings, realized in Italy and other European countries in the 60s and 70s. The parametric study is based on the results of extensive nonlinear response‐time history analyses of 2‐DOF systems, using a set of seven artificial and natural seismic ground motions. In the parametric study, buildings with strength ratio (Fy/W) ranging from 0.03 to 0.15 and post‐yield stiffness ratio ranging from 0% to 6% are examined. Three different types of isolation systems are considered, that is, high damping rubber bearings, lead rubber bearings and friction pendulum bearings. The isolation systems have been designed accepting the occurrence of plastic hinges in the superstructure during the design earthquake. The nonlinear response‐time history analyses results show that structures with seismic isolation experience fewer inelastic cycles compared with fixed‐base structures. As a consequence, although limited plastic deformations can be accepted, the collapse limit state of seismically isolated structures should be based on the lateral capacity of the superstructure without significant reliance on its inherent hysteretic damping or ductility capacity. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
Evaluation of a passive gap damper to control displacements in a shaking test of a seismically isolated three‐story frame 
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下载免费PDF全文 Recent studies have indicated uncertainty about the performance limit states of seismically isolated buildings in very large earthquakes, especially if the isolator displacement demands exceed the seismic gap and induce pounding. Previous research has shown the benefit of providing phased supplemental damping that does not affect the isolation system response in a design event. A phased passive control device, or gap damper, was designed, fabricated, and experimentally evaluated during shake table testing of a quarter scale base‐isolated three‐story steel frame building. Identical input motions were applied to system configurations without a gap damper and with a gap damper, to directly assess the influence of the gap damper on displacement and acceleration demands. The gap damper was observed to reduce displacement demands by up to 15% relative to the isolated system without the gap damper. Superstructure floor accelerations increased substantially because of damper activation, but were limited to a peak of about 1.18 g. The gap damper reduces displacement most effectively if the ground motion contains one or more of the following characteristics: the spectral displacement increases with increasing period near the effective period of the isolation system, the motion is dominated by a single large pulse rather than multiple cycles at a consistent intensity, and the motion has a dominant component aligned with a major axis of the structure. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
Seismic response of 20‐story base‐isolated and fixed‐base reinforced concrete structural wall buildings at a near‐fault site 下载免费PDF全文
下载免费PDF全文 This paper investigates numerically the seismic response of six seismically base‐isolated (BI) 20‐story reinforced concrete buildings and compares their response to that of a fixed‐base (FB) building with a similar structural system above ground. Located in Berkeley, California, 2 km from the Hayward fault, the buildings are designed with a core wall that provides most of the lateral force resistance above ground. For the BI buildings, the following are investigated: two isolation systems (both implemented below a three‐story basement), isolation periods equal to 4, 5, and 6 s, and two levels of flexural strength of the wall. The first isolation system combines tension‐resistant friction pendulum bearings and nonlinear fluid viscous dampers (NFVDs); the second combines low‐friction tension‐resistant crosslinear bearings, lead‐rubber bearings, and NFVDs. The designs of all buildings satisfy ASCE 7‐10 requirements, except that one component of horizontal excitation, is used in the 2D nonlinear response history analysis. Analysis is performed for a set of ground motions scaled to the design earthquake and to the maximum considered earthquake (MCE). At both the design earthquake and the MCE, the FB building develops large inelastic deformations and shear forces in the wall and large floor accelerations. At the MCE, four of the BI buildings experience nominally elastic response of the wall, with floor accelerations and shear forces being 0.25 to 0.55 times those experienced by the FB building. The response of the FB and four of the BI buildings to four unscaled historical pulse‐like near‐fault ground motions is also studied. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
James M. Kelly 《地震工程与结构动力学》1999,28(1):3-20
In the current code requirements for the design of base isolation systems for buildings located at near-fault sites, the design engineer is faced with very large design displacements for the isolators. To reduce these displacements, supplementary dampers are often prescribed. These dampers reduce displacements, but at the expense of significant increases in interstorey drifts and floor accelerations in the superstructure. An elementary analysis based on a simple model of an isolated structure is used to demonstrate this dilemma. The model is linear and is based on modal analysis, but includes the modal coupling terms caused by high levels of damping in the isolation system. The equations are solved by a method that avoids complex modal analysis. Estimates of the important response quantities are obtained by the response spectrum method. It is shown that as the damping in the isolation system increases, the contribution of the modal coupling terms due to isolator damping in response to the superstructure becomes the dominant term. The isolator displacement and structural base shear may be reduced, but the floor accelerations and interstorey drift are increased. The results show that the use of supplemental dampers in seismic isolation is a misplaced effort and alternative strategies to solve the problem are suggested. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
11.
In this study, the multi‐intensity seismic response of code‐designed conventional and base‐isolated steel frame buildings is evaluated using nonlinear response history analysis. The results of hazard and structural response analysis for three‐story braced‐frame buildings are presented in this paper. Three‐dimensional models for both buildings are created and seismic response is assessed for three scenario earthquakes. The response history analysis results indicate that the design objectives are met and the performance of the isolated building is superior to the conventional building in the design event. For the Maximum Considered Earthquake, isolation leads to reductions in story drifts and floor accelerations relative to the conventional building. However, the extremely high displacement demands of the isolation system could not be accommodated under normal circumstances, and creative approaches should be developed to control displacements in the MCE. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
Shehata E. Abdel Raheem 《Bulletin of Earthquake Engineering》2014,12(4):1705-1724
Post-earthquake damages investigation in past and recent earthquakes has illustrated that the building structures are vulnerable to severe damage and/or collapse during moderate to strong ground motion. Among the possible structural damages, seismic induced pounding has been commonly observed in several earthquakes. A parametric study on buildings pounding response as well as proper seismic hazard mitigation practice for adjacent buildings is carried out. Three categories of recorded earthquake excitation are used for input excitations. The effect of impact is studied using linear and nonlinear contact force model for different separation distances and compared with nominal model without pounding consideration. The severity of the impact depends on the dynamic characteristics of the adjacent buildings in combination with the earthquake characteristics. Pounding produces acceleration and shear forces/stresses at various story levels that are greater than those obtained from the no pounding case, while the peak drift depends on the input excitation characteristics. Also, increasing gap width is likely to be effective when the separation is sufficiently wide to eliminate contact. Furthermore, it is effective to provide a shock absorber device system for the mitigation of impact effects between adjacent buildings with relatively narrow seismic gaps, where the sudden changes of stiffness during poundings can be smoothed. This prevents, to some extent, the acceleration peaks due to impact. The pounding forces exerted on the adjacent buildings can be satisfactorily reduced. 相似文献
13.
Brendon A. Bradley Rajesh P. Dhakal Gregory A. MacRae Misko Cubrinovski 《地震工程与结构动力学》2010,39(5):501-520
The efficacy of various ground motion intensity measures (IMs) in the prediction of spatially distributed seismic demands (engineering demand parameters, (EDPs)) within a structure is investigated. This has direct implications to building‐specific seismic loss estimation, where the seismic demand on different components is dependent on the location of the component in the structure. Several common IMs are investigated in terms of their ability to predict the spatially distributed demands in a 10‐storey office building, which is measured in terms of maximum interstorey drift ratios and maximum floor accelerations. It is found that the ability of an IM to efficiently predict a specific EDP depends on the similarity between the frequency range of the ground motion that controls the IM and that of the EDP. An IMs predictability has a direct effect on the median response demands for ground motions scaled to a specified probability of exceedance from a ground motion hazard curve. All of the IMs investigated were found to be insufficient with respect to at least one of magnitude, source‐to‐site distance, or epsilon when predicting all peak interstorey drifts and peak floor accelerations in a 10‐storey reinforced concrete frame structure. Careful ground motion selection and/or seismic demand modification is therefore required to predict such a spatially distributed demands without significant bias. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
A building with a seismic isolation system, in an earthquake, is recognized as producing substantially smaller accelerations and deformations compared with a building that use other systems. This type of system is therefore expected to better protect the building's nonstructural components, equipment, and other contents that are essential for the activities conducted in the building. Unlike many available studies on building responses, only a small number of studies on a buildings' nonstructural component responses are available, and no study has directly addressed building performance with regard to nonstructural component protection. This paper therefore measures the performance of various seismically isolated buildings. Specifically, the effects of important structural parameters, namely, isolation stiffness, isolation damping ratio, and number of stories on the response of base‐isolated structures are investigated parametrically. Ground motions with 2% exceedence in 50years Maximum Considered Earthquake (MCE) are used. Performance is compared with that of fixed‐base structures in order to present data that will be useful in justifying the more costly technology. The buildings are 3, 9, and 20 stories, represented by MDOF shear‐beam models. As examples of displacement‐sensitive and acceleration‐sensitive components, partition walls and ceilings are considered, respectively. The Pacific Earthquake Engineering Research Center performance‐based earthquake engineering methodology is adopted to evaluate the failure return periods of the examples based on their available fragility curves. In addition, the curves are varied hypothetically to understand the sensitivity of the return period to the curve features. Then, the median and dispersion of fragility curves required to satisfy the components' desired failure return period are obtained. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
Multi‐storey main buildings constructed with a low‐rise podium structure possess some architectural merits but the setback features of such a building complex may lead to seismic response enlargement of the main buildings. This paper explores the possibility of using passive friction dampers to connect the podium structure to the main buildings to prevent their seismic response enlargement without violating the architectural features. A series of shaking table tests were carried out on one 3‐storey and one 12‐storey building models in fully‐separated, rigidly connected, and friction damper‐linked configurations. Four sets of seismic ground motions were selected as inputs to the shaking table. The control competence of two buildings linked with friction damper was evaluated by comparison of their responses with those from fully‐separated and rigidly connected cases. Experimental results showed that unfavourable seismic response amplification did occur in the building complex in the rigidly connected case. By contrast, friction damper showed effectiveness in reducing absolute acceleration and interstorey drift responses of both buildings if friction force level was appropriately applied. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
16.
Viscous and other damping devices are often used as elements of seismic isolation systems. Despite the widespread application of nonlinear viscous systems particularly in Japan (with fewer applications in the USA and Taiwan), the application of viscous damping devices in isolation systems in the USA progressed intentionally toward the use of supplementary linear viscous devices due to the advantages offered by these devices. This paper presents experimental results on the behavior of seismically isolated structures with low damping elastomeric (LDE) and single friction pendulum (SFP) bearings with and without linear and nonlinear viscous dampers. The isolation systems are tested within a six‐story structure configured as moment frame and then again as braced frame. Emphasis is placed both on the acquisition of data related to the structural system (drifts, story shear forces, and isolator displacements) and on non‐structural systems (floor accelerations, floor spectral accelerations, and floor velocities). Moreover, the accuracy of analytical prediction of response is investigated based on the results of a total of 227 experiments, using 14 historic ground motions of far‐fault and near‐fault characteristics, on flexible moment frame and stiff braced frame structures isolated with LDE or SFP bearings and linear or nonlinear viscous dampers. It is concluded that when damping is needed to reduce displacement demands in the isolation system, linear viscous damping results in the least detrimental effect on the isolated structure. Moreover, the study concludes that the analytical prediction of peak floor accelerations and floor response spectra may contain errors that need to be considered when designing secondary systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
Spatial seismic modeling of base‐isolated buildings pounding against moat walls: effects of ground motion directionality and mass eccentricity 下载免费PDF全文
下载免费PDF全文 Structural impact between adjacent buildings may induce local and, in some extreme cases, severe damage, especially in the case of seismically isolated buildings. This study parametrically investigates in the three‐dimensional domain the effect of pounding on the peak response of base‐isolated buildings, which are simulated as nonlinear three‐dimensional multi‐degree‐of‐freedom systems. Firstly, it is shown that considering unidirectional, instead of bidirectional, excitations may lead to underestimation of the base drift demands. Subsequently, the peak responses of seismically isolated buildings utilizing lead rubber bearings are studied while varying important parameters, such as the incidence angle of seismic excitations, the available seismic clearance, and mass eccentricities, under the action of bidirectional horizontal excitations. A large number of numerical simulations are performed using a specially developed software that implements an efficient approach to model impacts, taking into account arbitrary locations of contact points. It is found that the peak interstory drift ratio is significantly influenced by the directionality of the ground motion. Therefore, the seismic performance of structures should ideally be assessed examining the peak structural response while bidirectional ground motions are imposed at various incident angles. Furthermore, it is also observed that the interstory drift ratios increase while decreasing the available gap size, up to a certain value. Finally, the parametric analyses indicate that the effects of impact are more severe for structures with mass eccentricities, and in which case, the estimation of the critical incidence angle becomes more laborious. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
Seismic response analysis of an irregular base isolated building 总被引：3，自引：0，他引：3
This paper assesses the reliability of code-compliant linear and nonlinear dynamic analyses for irregular buildings with base
isolation system (BIS). Comprehensive analyses are carried out for a case study comprising a large reinforced concrete multi-storey
framed hospital with 327 high-damping rubber bearings. Spectral and time history (linear and nonlinear) analyses were performed
on the three-dimensional (3D) finite element model (FEM) of the structure; simplified analyses were also conducted on single-degree-of-freedom
(SDOF) systems. It is found that, at damageability limit state, the values of maximum interstorey drifts (d/h) computed with
spectral analyses on the three-dimensional FEM range between 1/6 and 1/10 of the code limit (d/h = 0.33%); thus more stringent
code limits should be required for buildings with BISs. The maximum floor acceleration is reduced by about 70% with respect
to the ground acceleration (free field site); the acceleration profile is uniform along the height of the multi-storey frame.
Threshold values of floor accelerations to assess the seismic performance of equipments in buildings with BIS are lacking.
At ultimate limit state (ULS), spectral analyses provide values of actions and deformations that are less conservative than
those derived through time history analyses. To perform reliable dynamic analyses of base isolated buildings it is crucial
to select natural earthquake ground motions compliant with the fundamental period of vibration of the structural system. Nevertheless,
it is not straightforward to select adequate natural strong motions in the catalogues available world-wide; buildings incorporating
BISs possess periods of vibration which are generally higher than 2.0 s. As a result, distant and high-magnitude earthquakes
are effective for base isolated buildings; nevertheless, such earthquakes are scarce in the seismic databases. The outcomes
of the present study also demonstrate that simplified linear analyses tend to provide estimates of the response quantities,
displacements of base isolators and base shear of the superstructure, which can be reliably employed at preliminary design
stage. Spectral analysis results of the 3D model tend to match those of the SDOF systems, even for irregular superstructure,
provided that modal mass participating ratios are greater than 85–90%. The results of spectral analyses on both SDOF and three-dimensional
FEM envelope the outcomes of linear time histories. 相似文献
19.
Several seismic design codes around the world restrict the use of theit Equivalent Lateral Force analysis method to structures satisfying structural regularity limits. These regularity limits are based on engineering judgement and lack quantitative justification. One common irregularity is that of a change in vertical stiffness over the building height. This stiffness irregularity is almost always associated with a change in vertical strength over the building height. For this reason, the effect of various realistic combinations of stiffness–strength irregularity in shear‐type buildings is evaluated to quantify regularity limits. Structures analysed had 3, 5, 9 and 15 storeys, and the floor mass at all the levels were kept the same. Both regular and irregular structures were designed in accordance with the Equivalent Lateral Force procedure to produce the same engineering demand parameter. Structural ductility factors of 1, 2, 3, 4 and 6, and target (design) interstorey drift ratios ranging between 0.5 and 3%, were used in this study. The irregular structures were created by modifying specific storey lateral stiffnesses from that of the regular structure. Strengths at these storeys were also modified to ensure realistic relationships between stiffness and strength. The modified structures were then redesigned until the target interstorey drift ratio was achieved at the critical storey. Inelastic dynamic time‐history analysis was conducted to compare the maximum interstorey drift ratio demands of the regular and irregular structures. Simple equations were developed to estimate possible variations in demand due to vertical stiffness–strength irregularity applied at critical locations in structures. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
T. Z. Yeow A. Orumiyehei T. J. Sullivan G. A. MacRae G. C. Clifton K. J. Elwood 《Bulletin of Earthquake Engineering》2018,16(12):5963-5993
This study compares seismic losses considering initial construction costs and direct-repair costs for New Zealand steel moment-resisting frame buildings with friction connections and those with extended bolted-end-plate connections. A total of 12 buildings have been designed and analysed considering both connection types, two building heights (4-storey and 12-storey), and three locations around New Zealand (Auckland, Christchurch, and Wellington). It was found that buildings with friction connections required design to a higher design ductility, yet are generally stiffer due to larger beams being required to satisfy higher connection overstrength requirements. This resulted in the frames with friction connections experiencing lower interstorey drifts on most floors but similar peak total floor accelerations, and subsequently incurring lower drift-related seismic repair losses. Frames with friction connections tended to have lower expected net-present-costs within 50 years of the building being in service for shorter buildings and/or if located in regions of high seismicity. None of the frames with friction connections in Auckland showed any benefits due to the low seismicity of the region. 相似文献