Figure 3 - uploaded by Nicos Makris
Content may be subject to copyright.
Source publication
This paper presents experimental and analytical results on the seismic response of a rigid structure supported on isolation systems that consist of either lead rubber or sliding bearings. Shake table tests are conducted with various levels of isolation damping that is provided from the bearings and supplemental viscous fluid dampers. The table moti...
Contexts in source publication
Context 1
... the rigid bridge conÿgu- ration, two models and several isolation bearings and viscous damping devices were tested. Figure 3 shows the simplest among the two bridge conÿgurations tested-that is a rigid block with weight, mg = 293 kN (65:87 kips) resting on four isolation bearings. This isolated block model can be also equipped with uid dampers (as shown in Figure 3). ...
Context 2
... 3 shows the simplest among the two bridge conÿgurations tested-that is a rigid block with weight, mg = 293 kN (65:87 kips) resting on four isolation bearings. This isolated block model can be also equipped with uid dampers (as shown in Figure 3). The entire system is mounted on the UC-Berkeley shaking table for testing. ...
Context 3
... diierent sizes of uid dampers were used to achieve diierent levels of supple- mental damping. The small damper shown on the left of Figure 3 has a stroke limitation of ±4:0cm (±1:6in). This stroke limitation restricted the shear strains in the elastomeric bearings below the 100 per cent level as is indicated in Figure 2. Experimental data and analytical studies on the response of the isolated structure where the elastomeric bearings experienced large strains can be found in References [13; 18], while details on the instrumentation of the model can be found in References [13; 19]. ...
Context 4
... comprehensive experimental programme on the response of seismically protected bridges was conducted at the University of California, Berkeley [13]. For the rigid bridge conÿguration, two models and several isolation bearings and viscous damping devices were tested. Figure 3 shows the simplest among the two bridge conÿgurations tested—that is a rigid block with weight, mg = 293 kN (65 : 87 kips) resting on four isolation bearings. This isolated block model can be also equipped with uid dampers (as shown in Figure 3). The entire system is mounted on the UC-Berkeley shaking table for testing. The study reported herein concentrates on the response of isolated structures supported on hybrid isolation systems that consist of isolation bearings and supplemental dampers. The supplemental dampers used in this study are viscous uid dampers with force proportional to ...
Context 5
... comprehensive experimental programme on the response of seismically protected bridges was conducted at the University of California, Berkeley [13]. For the rigid bridge conÿguration, two models and several isolation bearings and viscous damping devices were tested. Figure 3 shows the simplest among the two bridge conÿgurations tested—that is a rigid block with weight, mg = 293 kN (65 : 87 kips) resting on four isolation bearings. This isolated block model can be also equipped with uid dampers (as shown in Figure 3). The entire system is mounted on the UC-Berkeley shaking table for testing. The study reported herein concentrates on the response of isolated structures supported on hybrid isolation systems that consist of isolation bearings and supplemental dampers. The supplemental dampers used in this study are viscous uid dampers with force proportional to ...
Context 6
... Two di erent sizes of uid dampers were used to achieve di erent levels of supplemental damping. The small damper shown on the left of Figure 3 has a stroke limitation of ± 4 : 0 cm ( ± 1 : 6 in ). This stroke limitation restricted the shear strains in the elastomeric bearings below the 100 per cent level as is indicated in Figure 2. Experimental data and analytical studies on the response of the isolated structure where the elastomeric bearings experienced large strains can be found in References [13 ; 18], while details on the instrumentation of the model can be found in References [13 ; 19]. During the earthquake simulation tests, the table motions had a compressed duration compared to the original ground motions so that the time scale is consistent with the reduced scale of the model structure. In all experiments, accelerations and stresses were kept at full scale so that 1 m = sec 2 and 1 Pa in the real world remains the same in the laboratory. Two length scales, S L = 6 ; 9, were adopted. Table I summarizes the scale transformations for selected observable quantities where acceleration and stresses are invariants. The relevance of the physical characteristics of the experimental model that we used in this study can be illustrated by considering as an example the physical characteristics of the 91 = 5 overcrossing currently under construction in Orange County, California [20]. Its deck has an approximate weight of 5300 kips and each of its eight dampers (four dampers at each end) has a stroke of ± 8 : 0 in. With a length scale, S L = 9, this bridge corresponds to a laboratory mass of 5300 kips = 81 = 65 : 43 kips, which is approximately the weight of the model used (mg = 65 : 87 kips). Now this weight when is associated with a length scale S L = 6, it corresponds to a real-world weight of 65 : 87 kips × 36 = 2371 kips, which is approximately the superstructure weight of a typical four-lane freeway ...
Similar publications
Performance-based earthquake engineering (PBEE) is based on the premise that the performance of engineered facilities can be predicted and evaluated with sufficient degree of confidence. However, prediction of system response greatly depends on the analyst’s experience and modeling skills. Therefore, the uncertainty with which the engineering commu...
Seismic isolation systems for buildings are generally selected to achieve higher seismic performance objectives, such as continued operation or immediate occupancy following a design earthquake event. However, recent large scale tests have suggested that these objectives may be compromised if the shaking includes large vertical acceleration compone...
![Fig. 2. Recommended configurations [10].](profile/Reza-Karami-Mohammadi/publication/233925265/figure/fig11/AS:668560342921230@1536408615530/Recommended-configurations-10_Q320.jpg)
Typical electrical substation equipment items are usually
connected to each other through flexible conductors. If the connections
are not flexible enough, they may cause intense dynamic
interaction between the equipment during an earthquake. This research
is to analytically study the performance of different flexible
conductor configurations used m...
![Figure 2. Force displacement loops for bilinear isolators[4,5,6].](profile/Sali-Hadigheh/publication/262807802/figure/fig1/AS:427293068795904@1478886014165/Force-displacement-loops-for-bilinear-isolators4-5-6_Q320.jpg)
Base isolation technique has been adapted as an engineering method to strengthen and reduce loads applied to the structures. When a structure is subjected to strong seismic loads, it experiences excessive displacements. According to the characteristics of near-fault excitations, such ground motions apply strong loads which make isolated structures...
![Figure 1. A typical viscoelastic damper [7]](profile/Seyed-Mehdi-Zahrai/publication/286221112/figure/fig7/AS:668309766828047@1536348873561/A-typical-viscoelastic-damper-7_Q320.jpg)
Near-field earthquakes are characterized by short duration pulses of long periods with large peak ground velocities and accelerations. Recent studies have shown that the performance of passive energy dissipation systems depends significantly on the characteristics of near-field ground motion pulses. This paper is focused on the viscoelastic (VE) da...
Citations
... In recent years, structural engineering has focused on developing and implementing techniques to reduce seismic vulnerability in structural systems, while encouraging resilient designs that prioritize occupant safety [1][2][3]. Structural control systems have been extensively investigated and implemented in response to these performance requirements, improving the seismic response of civil structures using external devices [4], such as passive control systems [5][6][7][8][9][10][11][12][13][14][15][16][17], active control systems [18][19][20][21][22], semiactive control systems [23][24][25][26][27], and more commonly hybrid control systems [28][29][30][31][32][33][34][35][36]. Passive control devices have been the most widely adopted in buildings because of their lower installation and maintenance costs, lack of energy requirements, and low capacity to cause structural damage. ...
Te dynamic performance of base isolation systems provides an effective means to reduce the seismic vulnerability of buildings. However, large displacements in the base isolation during seismic events pose a major challenge for this control system. Recently, novel control systems have been implemented to control and reduce the excessive displacements. This study presents an evaluation of the seismic performance of unconnected-fiber-reinforced elastomeric isolators (U-FREI) and variable orifice damper (VOD) devices used together as a hybrid control system for a low-degree-of-freedom reference structure by employing real-time hybrid simulation (RTHS) testing technique. This physical cybernetic testing methodology allows a dynamic system of interest to be substructured into two components: numerical and experimental. In this study, the numerical substructure corresponds to a 2-degree of freedom model, representing a reference structure, and an experimental substructure was formed using the hybrid control system described. To develop an interface between the two substructures, a horizontal transfer system (HTS) was implemented and coupled with a vertical transfer system (VTS). Using RTHS, the performance of the reference structure and the hybrid control system was evaluated under six seismic events: CAM, CAT, El Centro, Loma Prieta, Pizarro, and Chihuahua, at a maximum acceleration of 0.10 g (0.981 m·s −2). Te experimental behavior of the hybrid control system allows the reference structure to reduce its maximum drift by more than 24% compared to the fixed structure. Finally, the performance and accuracy of the RTHS tests were calculated.
... Moreover, the multipulse signals may cause more severe damage than the single-pulse ones based on the tests using simple artificial signals, like triangle waves, square waves, and harmonic waves. 2,28,37 Though multipulse ground motions are significant, the effects of recorded multipulse ground motions on structures are still unclear. To address this challenge, an identification method and an analysis procedure are formulated, where the identification method is utilized to detect the non-, single-, and multipulse ground motions from seismic databases, and the analysis procedure combines the finite element method and quantitative evaluation parameters to assess the seismic damage. ...
Near‐fault pulse‐like ground motion is a significant class of seismic records since it tends to cause more severe damage to structures than ordinary ground motions. However, previous researches mainly focus on single‐pulse ground motions. The multipulse ground motions that exist in records receive rare attention. In this study, an analysis procedure is proposed to investigate the effect of multipulse ground motions on structures by integrating finite element analysis and an identification method that features each pulse in the multipulse ground motion satisfying the same evaluation criteria. First, the Arias intensity, wavelet‐based cumulative energy distribution, and response spectra of identified non‐, single‐, and multipulse ground motions are compared. Then, the seismic damage on frame structures, a soil slope, and a concrete dam under non‐, single‐, and multipulse ground motions are analyzed. Results show that the spectral velocity of multipulse ground motions is significantly greater than those of non‐ and single‐pulse ground motions and potentially contains multiple peaks in the long‐period range. Seismic damage evaluation indicates that the maximum interstory drift of frame structures with high fundamental periods under multipulse ground motions is about twice that of nonpulse ground motions. Similar characteristics also exist in the soil slope and the concrete dam. Therefore, multipulse ground motions potentially cause more severe damage to structures compared to non‐ and single‐pulse ground motions. The findings of this study facilitate the recognition of the increased seismic demand imposed by the multipulse ground motion in engineering practices, provide new possibilities for ground motion selection in seismic design validation, and shed new light on seismic hazard and risk analysis in near‐fault regions.
... However, studies conducted by Maleki and Ziyaeifar [163] have shown that the baffles were less effective in reducing the sloshing height in tanks with a lower aspect ratio. In recent years, several hybrid systems [159,[164][165][166][167], wherein friction-based isolators or elastomers are combined with energy dissipating devices such as viscous fluid dampers or friction dampers, have been proposed and their effect on the reduction of sloshing has been investigated. These systems have been found to be effective in solving the sloshing resonance problem in isolated storage tanks. ...
... Three mass system to model liquid-tank system with hybrid isolation system. -Seismic Linear [165][166][167] Ground supported Flexible, rigid × ...
Globally, tanks play a major part in the provision of access to clean drinking water to the human population. Beyond aiding in the supply of fresh water, tanks are also essential for ensuring good sanitary conditions for people and for livestock. Many countries have realized that a robust water supply and a robust sanitation infrastructure are necessary for sustainable growth. Therefore, there is large demand for the construction of storage tanks. Further, liquid storage tanks are crucial structures which must continue to be operational even after a catastrophic natural event, such as an earthquake, to support rehabilitation efforts. From an engineering point of view, the various forces acting on the tanks and the behaviour of the tanks under various loads are important issues which need to be addressed for a safe design. Analyses of the tanks are challenging due to the interaction between the fluid and tank wall. Thus, researchers have conducted several investigations to understand the performance of storage tanks subjected to earthquakes by considering this interaction. This paper discusses the historical development of various modelling techniques of storage tanks. The interaction with the soil also influences the behaviour of the tanks, and hence, in this paper, various modelling approaches for soil structure interaction are also reviewed. Further, a brief history of various systems of base isolation and modelling approaches of base-isolated structures are also discussed in this article.
... However, previous studies mainly focused on single-pulse ground motions. The multi-pulse ground motion is rarely considered even though it exists in records and is verified to potentially cause severer damage to structures than single-pulse ground motions by artificial simple signals, like triangle wave, square wave, and harmonic wave [7][8][9]. Hence, this study attempts to propose a multipulse ground motion identification method to facilitate wider studies on multi-pulse records. A generalized continuous wavelet transform (GCWT) method by combining convolution analysis with evaluation parameters is proposed, which requires each pulse in the multi-pulse ground motion to satisfy the same criteria. ...
... After the convolution analysis, the energy ratio between the recorded pulse parts and the original ground motion in different pulse periods are calculated using Eq. (7). Then, the threshold of energy ratio is applied to exclude the scaled pulse model that cannot meet the requirement of energy. ...
The near-fault pulse-like ground motion is of practical importance since it tends to cause severer damage to structures than ordinary ground motion in engineering and helps characterize the seismic source and the kinematic characteristics of the geological fault in seismology. However, previous investigations mainly focus on single-pulse ground motion. As one of the particular seismic records in the near-fault earthquake, the multi-pulse ground motion is rarely considered caused by the absence of an effective identification method. Hence, a generalized continuous wavelet transform (GCWT) method is proposed by combining convolution analysis with evaluation parameters to facilitate wider studies on multi-pulse ground motion. In identification, the proposed method requires each pulse in the multi-pulse ground motion to satisfy the same criteria and excludes the effects of attenuation component. In methodology, the proposed method overcomes the limitations of the classical CWT method that requires a wavelet basis and provides a workable and flexible framework for pulse-like ground motion identification. Based on the method, single- and multi-pulse ground motions from two typical near-fault earthquakes on the PEER NGA-West2 database were identified. The effects of the pulse model and ground motion orientation on identification are discussed. Besides, the 5\% damped spectral velocity of multi-pulse ground motions potentially contain multiple peaks in the high-period range. This phenomenon implies that the risk would be underestimated for the response spectrum-based seismic hazards and risk analysis if the multi-pulse features are not, or are insufficiently taken into account.
... The study indicates that, with a suitable viscous energy dissipation mechanism, it is possible to reduce large displacements without a further increase in base shear and accelerations. Chang et al. [116] carried out studies by considering viscous and friction damping in base-isolated structures. A friction pendulum bearing has been considered for the study with additional fluid dampers. ...
Base isolation techniques have emerged as the most effective seismic damage mitigation strategies. Several types of aseismic devices for base isolation have been invented, studied, and used. Out of several isolation systems, sliding isolation systems are popular due to their operational simplicity and ease of manufacturing. This article discusses the historical development of passive sliding isolation systems, such as pure friction systems, friction pendulum systems, and isolators with other sliding surface geometries. Moreover, multiple surface isolation systems and their behavior as well as the effectiveness of using complementary devices with standalone passive isolation devices are examined. Furthermore, the article explored the various modeling techniques adopted for base-isolated single and multi-degree freedom building structures. Special attention has been given to the techniques available for modeling the complex phenomena of sliding and non-sliding phases of sliding bearings. The discussion is further extended to the development in the contemporary areas of seismic isolation, such as active and hybrid isolation systems. Although a significant amount of research is carried out in the area of active and hybrid isolation systems, the passive sliding isolation system still has not lost its appeal due to its ease of adaptability to the structures.
... They reported the effectiveness of the hybrid system in decreasing the base displacement. Chang et al. (2002) studied the seismic performance of hybrid base-isolation (lead rubber and sliding bearings) systems combined with a viscous fluid damper. They conducted experimental and analytical studies and reported the effectiveness of supplemental damping in mitigating the displacements of rigid structures with relatively long-period isolation (T ≤ 3 s) systems without affecting the base shear. ...
... To better understand the multi-pulse characteristics of near-fault ground motions, Alavi and Krawinkler [14] attempted to describe the acceleration history by square waves and then investigated the effect of repeated pulses on response parameters. Makris and Black [15,16] also characterized multiple inherent pulses by harmonic functions. Menun and Fu [17] represented these pulses by a composite function as well. ...
... logðPGV E Þ ¼ 1:243 þ 0:134Mw À 0:389 logðRÞðσ ¼ 0:12Þ ðReverse faultÞ (14) logðPGV E Þ ¼ 1:293 þ 0:088Mw À 0:282 logðRÞðσ ¼ 0:113Þ ðReverse À oblique faultÞ (15) logðPGV E Þ ¼ 0:504 þ 0:203Mw À 0:298 logðRÞðσ ¼ 0:166Þ ðStrike À slip faultÞ (16) where PGV E is the peak ground velocity of the main large-energy pulse (cm/s), R is the rupture distance (km), and Mw is the moment Fig. 13. Relationship between TP E and magnitudes, the models proposed in previous work, and the group of models proposed in this paper according to fault-type. ...
Multi-pulse characteristics of near-fault ground motions, such as the number of inherent pulses, pulse periods, and amplitudes, have notable influences on the response of structures. To investigate these important parameters, an automatic detection procedure, which is conducted on the rough pulse signal that is extracted by the HHT method, is proposed in this work. This procedure can localize all inherent pulses in the time domain independently and discontinuously. Important parameters can be automatically obtained at the same time. Then, statistical relationships between these multi-pulse parameters and earthquake parameters, including moment magnitudes, site conditions (Vs30), rupture distances and types of faults, are investigated comprehensively. With an increasing number of pulses, the multi-pulse ground motions are more likely to be recorded in relatively limited areas. All pulse periods in a velocity record are similar to each other and can be represented by the period of the pulse with the largest energy (TPE). TPEs are almost identical to periods of the first pulse in the time domain (TP1). They are related not only to magnitudes but also to fault-types and site conditions. New empirical models are proposed in this work according to fault-types that can predict most TPEs across all magnitudes (from 5.7 to 7.6). For amplitudes, all PGVs of inherent pulses can be expressed by the PGV of the pulse with the largest energy (PGVE) in a linear attenuation relationship. PGVEs are related to rupture distances, site conditions, and fault-types. New empirical models are also developed in this work.
... To enhance the seismic capacity of buildings, isolating the seismic forces applied to buildings by applying a movable base, including foundation or column bases, to the structure is considered an effective strategy. Rubber bearings are common isolators for elongating the natural period of the structure due to the low stiffness of the bearings, and the response can be reduced by applying additional damping (Bakhshi et al. 1998, Chang et al. 2002, Tiong et al. 2014, and Mostaghel et al. 1987. Sliding-type bearings, such as friction pendulum systems, for use as core elements of base-isolated structures, have been developed to minimize the friction coefficients of sliding interfaces (Constantinou et al. 2007, Fakhouri et al. 2013, Mokha et al. 1990, 1991, Tsopelas et al. 1996, Zayas et al. 1990, Amiri et al. 2017). ...
An experimental study was conducted to evaluate the dynamic behavior of a free-standing frame equipped with a movable base system using cast iron and mortar as the bearing materials. The preliminary friction test indicated that a graphite layer developed on the interface and exhibited stable friction behavior. The friction coefficient ranged from 0.33 to 0.36 when the applied normal compression stress ranged from 2.6 to 5.2 MPa. The effect of the variation of normal compression stress would be small. Shaking table tests on the free-standing frame showed that rock, slide, and rock-slide responses occurred. The
cumulative slide distance reached 381 mm under JMA Kobe wave excitation; however, only a few cyclic slides occurred at the same locations along the moving track. Most surfaces sustained single slides. Similar results can be observed in other shaking
conditions. The insufficient cyclic sliding and significant rocking resulted in a few graphite layers on the mortar surfaces. Friction coefficients were generally similar to those obtained in the preliminary friction tests; however, the values fluctuated when the rocking became significant. The collisions due to rocking caused strong horizontal acceleration responses and resulted in high friction coefficient. In addition, the strong horizontal acceleration responses caused by the collisions made the freestanding
specimen unable to reduce the input horizontal acceleration notably, even when slippage occurred. Compared with the counterpart fixed-base specimen, the specimen equipped with the iron-mortar base could reduce the horizontal acceleration amplification response and the structural deformation, whereas the vertical acceleration response was doubled due to collisions from rocking.
... 12 Automatic code generation from such visual programming tools makes the process of developing hard real-time applications straightforward as shown for a two-pier reinforced concrete bridge tested at the Experimental Laboratory of EUCENTRE, Pavia, Italy, with two alternative isolation schemes. 13,14 These are the issues that the numerical/experimental activities conducted at the EUCENTRE explore, and main findings are reported hereinafter. More precisely, the method and implementation of the partitioned time integration casted in state-space form are presented in Section 2. Section 3 discusses the verification case study, which consists of a three-bay reinforced concrete bridge provided with two alternative isolation devices. ...
Hybrid simulation reproduces the experimental response of large‐ or even full‐scale structures subjected to a realistic excitation with reduced costs compared with shake table testing. A real‐time control system emulates the interaction between numerical substructures, which replace subparts having well‐established computational models, and physical substructures tested in the laboratory. In this context, state‐space modeling, which is quite popular in the community of automatic control, offers a computationally cheaper alternative to the finite‐element method for implementing nonlinear numerical substructures for fast‐time hybrid simulation, that is, with testing timescale close to one. This standpoint motivated the development of a computational framework based on partitioned time integration, which is well suited for hard real‐time implementations. Partitioned time integration, which relies on a dual assembly of substructures, enables coupling of state‐space equations discretized with heterogeneous time step sizes. In order to avoid actuators stopping at each simulation step, the physical substructure response is integrated with the same rate of control system, whereas a larger time step size is allowed on the numerical substructure compatibly with available computational resources. Fast‐time hybrid simulations of a two‐pier reinforced concrete bridge tested at the EUCENTRE Experimental Laboratory of Pavia, Italy, are presented as verification example.
... A hybrid friction-controllable sliding system for seismic response control of buildings was introduced [7]. Experimental and analytical results for the seismic response of a rigid structure supported on hybrid isolation systems were presented by Chang et al. [8]. A constrained optimization procedure for the dynamic analysis of hybrid base isolation systems under earthquake excitation was present by Oliveto et al. [9]. ...
A typical megaframe structure has a high lateral stiffness and is excellent for high-rise structures. However, this high stiffness can lead to poor seismic response of a structure. Seismic isolation technology is a mature and cheap vibration control method that is used for vibration reduction in megaframes. This paper introduces a megaframe structure based on substructure combined isolation. The structure consists of two parts. The main body is a megaframe, and the substructure is the subframe with the combined isolation layer arranged at the bottom of the subframe. The seismic performance of this structure system was evaluated by performing shaking table tests of two megaframe model structures. The responses of the deformation, acceleration, and shear of the structure were measured. The dynamic behaviors of the structure with or without the combined isolation layer when exposed to single and bidirectional near-fault and far-fault ground motions with different peak values were investigated. The results showed that the combined isolation layer can reduce the bidirectional seismic response of the main frame and subframe. The acceleration, base shear, and displacement responses had similar vibration reduction trends for the two model structures, and the structural responses under bidirectional earthquake were generally greater than that under a single directional earthquake. The near-fault pulse effect increased the seismic response of the structure. The increase of the predominant period of ground motion also increased the seismic response of the structure.
