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After an earthquake, non‐negligible residual displacements may affect the serviceability of a base isolated structure, if the isolation system does not possess a good restoring capability. The permanent offset does not affect the performance unless the design is problematic for utilities, also considering possible concerns related to the maintenanc...
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... two sliding concave surfaces with radius R 1 and R 2 , the resulting is the DCFP bearing (Figure 2), which produces two independent pendulum response mechanisms and can be modeled as a series of two FPSs. The equivalent restoring stiffness K p is function of the equivalent radius R e of the combined FPSs and can be expressed with Equation (2) [18]. ...
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... In recent studies concerning code-conforming base-isolated RC frames buildings (Cardone et al. 2017(Cardone et al. , 2019Ponzo et al. 2017Ponzo et al. , 2021aLamarucciola 2023a, 2023b;Ragni et al. 2018), conducted within the Reluis research project (RINTC -Implicit Risk of Italian building Code), the structural reliability has been investigated by performing extensive Multi-Stripe nonlinear dynamic Analyses (MSAs) (Jalayer and Cornell 2003). A set of archetype residential RC buildings differing for construction period (50s, 60s, 70s, 80s-90s, current), design approach (Gravity Load Design GLD, Seismic Load Design SLD based on old and currently technical standards) and building location characterized by medium and high seismic hazard for Italy, was analyzed. ...
Recently, experimental studies on failure conditions of buildings equipped with curved surface sliding isolators have shown that when no displacement restraining elements are employed and the concave plates feature a flat rim, the inner slider can run on the edge of the sliding surfaces producing lateral displacement larger than the nominal isolator capacity. The over-stroke displacement capacity reduces the probability of seismic collapse of code-conforming base-isolated buildings for earthquake stronger than the design one. In order to quantify the benefit of the over-stroke displacement capacity of double concave curved surface slider (DCCSS) bearings on the seismic fragility of base isolated buildings, four case studies of six-storey reinforced concrete framed structures, consisting of new constructions and retrofit of existing structures located in high and medium hazard seismic sites, have been investigated in this paper. In all cases, two configurations of the isolation system have been considered, with end-stop displacement or with over-stroke displacement capacity. The seismic performance of the buildings has been investigated by multi-stripe nonlinear time-history analysis. The results of the nonlinear dynamic analysis at the collapse limit state have been compared with nonlinear static analysis in terms of maximum displacement and corresponding base shear. Fragility curves highlight a higher safety margin against collapse for seismic intensities beyond the design limit state of the isolation system with over-stroke capacity.
... DCFPBs have becoming increasingly popular owing to their advantages in fulfilling the demand of larger response displacements. In response to this demand, considerable experiments of DCFPBs were conducted to study the extra-stroke response of them (without restraining ring) under extreme seismic loading , the effect of restraining ring design on the extreme behavior (Bao et al. 2017), and the influence of residual displacement on the maximum displacement (Ponzo et al. 2017). It has been observed from recent studies that seismically isolated buildings with braced frames designed using ASCE have unacceptable collapse performance due to either insufficient isolator displacement capacity or excessive inelastic structural deformations (Kitayama and Constantinou 2021). ...
... The residual displacement of FPB in the last excitation induces larger maximum and residual displacement in the next loading run, which reveals the adverse effects of residual displacement as mentioned in many studies [23][24][25]. Notwithstanding, it can be concluded that the existing mechanism model (singleFPBearing) with the suggested friction model (Fig. 18) can describe the dynamic behaviors of FPB with good accuracy. The matching differences are quite prominent in the bearing displacement of the FPB in mid pier P2 since the initial damage by the shear pin cut is not considered. ...
Seismic performance of railway bridge isolated by FBP
... Fenz [32] found that there is no apparent correlation between the number of components in the excitation and the resulting components of permanent displacement of FPBs based on shaking table test results of a six-story steel moment resisting frame. Ponzo et al. 30 [34] investigated the restoring capability of a three dimensional one-storey steel isolated by DFPBs under earthquakes sequence. Based on the test results, a simplified design suggestion for the estimation of maximum expected residual displacements of DFPBs is validated. ...
... Shaking magnitude of the residual displacements depends on the restoring capability of the DFPBs. If the restoring capability is insufficient, the residual displacements after earthquake loading and its accumulation during a sequence of seismic events may affect the functionality of the building [34]. The tested DFPBs exhibited sufficient restoring capability even under MCE and VRE of Intensity IX, which ensures the protection of the superstructure. ...
The effectiveness of seismic isolation by friction pendulum bearings (FPBs) in protecting structural and non-structural components from damage was evaluated by shaking table tests. A base-isolated reinforced concrete frame model by double friction pendulum bearings (DFPBs) with 1/5 scale was considered in the experimental program. A non-isolated model was also tested for comparison. The models were subjected to ground motions with incremental earthquake intensities. This paper presents a comprehensive overview of the test results in terms of peak inter-story drifts, peak floor accelerations, floor acceleration response spectra, hysteretic behaviours, seismic responses of the DFPBs and damage mechanisms of the structures. The results demonstrated that the base-isolated system can effectively protect both structural and non-structural components even under earthquakes larger than maximum considered intensities. The residual displacements of DFPBs remained small after multiple inputs and showed no direct correlation with the maximum sliding displacement and earthquake intensities. The effect of vertical earthquake shaking on the displacement responses of DFPBs were negligible for the test model.
... Among various isolation measures, the elastomeric isolator including lead rubber bearing, high damping rubber bearing and natural rubber bearing has become the mainstream of isolation bearings, and has been extensively utilized in the building and other structures (Clark et al., 2000;Martelli and Clemente, 2014). The friction pendulum bearing (FPB) proposed by Zayas et al. (1987) as a different type of isolation bearing has also received increasing attention over the past 30 years Nagarajaiah et al., 1993;Pranesh and Sinha, 2004;Tsai et al., 2006;Fenz and Constantinou, 2008;Bao et al., 2017;Ponzo et al., 2017;Auad and Almazán, 2021). As shown in Fig. 1, the simplest FPB consists of an articulated slider, a bottom plate with spherical concave surface and a top plate. ...
Base-isolated building as one of the effective measures of improving building seismic performance may be exposed to strong winds. On this condition, the building will undergo complicated nonlinear and coupled dynamic response under synchronous three-dimensional (3D) wind loads. This study establishes an analysis framework for coupled dynamic response of tall buildings isolated with multiple friction pendulum bearings (FPBs) under 3D wind loads. A biaxial Bouc-Wen hysteresis model with a velocity-dependent friction coefficient is used to describe the coupled frictional forces of each individual bearing. The multi-correlated 3D wind loads on stories are modeled based on multiple point synchronous pressure measurement in a wind tunnel. The building top displacement and acceleration, and displacements of base slab and bearings are quantified under uniaxial (one of alongwind, crosswind and torsional), biaxial (both alongwind and crosswind), and triaxial (simultaneous alongwind, crosswind and torsional) wind loads. The distribution of friction-induced dissipation energy of the bearings is quantified. The dynamic response of corresponding fixed-base building is also evaluated for comparison. The variation of structural responses with wind direction is also investigated. The influences of stiffness eccentricity and torsional frequency of the upper structure on corner acceleration of the top floor are further discussed to reveal the torsional coupling effect. This study sheds light on 3D nonlinear response characteristics of tall buildings isolated with FPBs, and helps to understand the coupled dynamic behavior as result of biaxial friction, structural eccentricity, and spatiotemporal wind loads.
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... In order to solve the problem of a super-long structure producing excessive temperatureinduced internal forces on the frame column at the far end, the current solution is to set a vibration isolation bearing [13][14][15][16] and a friction pendulum bearing [17][18][19][20][21] at the roof-column top to connect the top with the steel structure. However, the tensile capacities of these two bearings are poor. ...
To resolve the problem of the super-long steel structures producing high-temperature stress on the lower concrete roof column section and improve the structure’s seismic performance, in this paper, we introduce a type of composite damped hinge bearing (CDHB). Firstly, this paper introduces the detailed construction of the CDHB and elaborates on its working principle. The mechanical properties of a CDHB have been tested, including the monotonic loading test on the whole bearing and the reciprocal loading test on the built-in dampers. The CDHB’s working performance, rotation performance, and energy consumption performance under tensile and compressive forces are also discussed in this paper. The study results show that: (1) Generally, the vertical deformation of the CDHB increases linearly with the increase of compressive and tensile forces, while it decreases with the increase of initial displacement. (2) Under vertical loading, the CDHB can reach a turning angle of 0.6 rad. The bearing is more likely to rotate with the increase in initial displacement. (3) The ultimate displacement, maximum damping force, damping constant, and damping coefficient of the built-in dampers are all stable.
... Specifically, negligible residual deformation will be observed in the base isolation system with the property of d max /d r > 0.5, where d max is the absolute peak displacement of the isolating systems, but d r is the maximum static residual displacement. Furthermore, Ponzo et al. 21 investigated the SC capability of the double concave friction pendulum isolation system through shaking table tests, which confirms that the isolation system has a good restoring capability when the ratio is d max /d r > 0.5. Both studies show that one of the most effective ways to reduce the residual deformation concentrated in the isolation system is to reduce the static residual displacement d r when the d max of the isolation bearing is certain. ...
This study presents a novel self‐centering (SC) base isolation system enabled by traditional lead rubber bearing (LRB) incorporating superelastic shape memory alloy (SMA) U‐shaped dampers (hereinafter referred to as SMA‐LRB). This system is particularly suitable for some important structures (e.g., hospital buildings) that require high seismic performance and rapid recovery of normal serviceability after a severe earthquake. The working mechanism of the SMA‐LRBs is first illustrated, followed by a comparative experimental study on the traditional LRB and the emerging SMA‐LRB. Test results confirm the satisfactory flag‐shaped hysteresis loops of SMA‐LRB associated with significantly reduced residual deformation under cyclic loading. Subsequently, a refined numerical modeling strategy for these bearings is developed. The seismic performances of the SMA‐LRBs are examined systematically through two comparative reinforced concrete (RC) frame buildings, namely, the traditionally isolated and the SC isolated cases under far‐ and near‐field earthquakes. Seismic fragility analyses are further carried out through incremental dynamic analysis (IDA). The seismic responses demonstrate that the SC isolated building can match or improve the behavior of the traditional isolated buildings. Compared with the considerable residual deformation of the traditional isolated system under some earthquake events, the SC isolated system exhibits negligible residual deformation that can significantly avoid normal serviceability disruption while achieving the high‐performance objectives. The SC base isolation system can provide a promising type of advanced seismic protection device for earthquake resilient design.
... The bearing fails by exceeding the displacement limit when the rigid slider (the central part of TFP) slides off from the inner concave plates. The DC isolators do not have restrainer rings, which is nowadays a common practice in applications in Europe Ponzo et al. [57]. It should be noted that the current version of the European Standard EN15129 (CEN [58]; Section 8.3.1.2.3) prohibits the use of restrainer rings while ASCE/SEI 7-16 [31] does not have such requirement. ...
This paper investigates the seismic downtime of seismically isolated buildings with steel moment or braced frames designed by the procedures of ASCE/SEI 7–16. The seismic isolation systems considered in this study are comprised of triple or double friction pendulum isolation bearings with and without moat walls. The seismic downtime is calculated from the damage to structural components and non-structural components, demolition and collapse of buildings. The downtime components (repair and inspection) are defined, and mathematical expressions are provided for the computation of downtime fragility curves, expected annual downtime, and economic losses due to the expected annual downtime. The procedure is then implemented using the results of nonlinear response history analysis from previous studies by the first author. The study demonstrates that the expected annual downtime of seismically isolated buildings is less than that of the comparable non-isolated buildings regardless of the seismic isolation systems used. Among the cases of seismically isolated buildings studied in this paper, it is found that the most effective structural system to mitigate long downtime is the seismically isolated building with seismic isolators with enhanced sizes and with braced frames that are designed to be minimally compliant with the seismic design requirements of ASCE/SEI 7–16.
... Previous studies have proposed a variety of numerical modelling and experimental tests for slider isolators (Constantinou et al., 1990;De La LLera 1998, 2011;Fenz and Constantinou 2006;Fenz and Constantinou 2008a;2008b;Becker and Mahin 2012a;2012b;Lomiento et al., 2013;Sarlis and Constantinou 2016;Ponzo et al., 2017Ponzo et al., , 2019Ponzo et al., , 2020Ponzo et al., , 2021De Domenico et al., 2018Pavese et al., 2018;Di Cesare et al., 2019Pigouni et al., 2019;Quaglini et al., 2012Quaglini et al., , 2019Furinghetti et al., 2020) that also involve geometrical compatibility and multibody kinematics formulations (Belfiore et al., 2000;Shabana 2001;Tsai et al., 2005;Popov 2010;Mazza et al., 2017;Nikravesh 2018;Bianco et al., 2020Bianco et al., , 2021. Additionally, the behaviour of single and multiple concave surface sliding bearings has been analytically characterized by Sarlis Constantinou (2013). ...
For double concave curved surface slider (DCCSS) isolators with a flat rim and lacking restrainers, such as those most commonly used in Europe, the rigid slider can exceed the geometrical capability of the housing plate during earthquakes stronger than those produced in simulations. During this over-stroke displacement, DCCSSs preserve the ability to support superstructure gravity loads and the capacity to dissipate energy. There are currently no applicable hysteresis rules or available algebraic solutions that can be used to predict over-stroke behaviour for response-history analysis. This study presents an algebraic solution to extend basic theories for estimating the actual limit displacement of DCCSS devices with over-stroke capacity. DCCSS behaviour in the over-stroke sliding regime was modelled with a focus on geometrical compatibility and kinematics. The proposed analytical formulation was calibrated on the basis of experimental controlled-displacement tests performed on single DCCSS devices. A case study of a six-storey reinforced concrete frame isolated building was modelled using a combination of non-linear elements that are currently available in several structural analysis software packages and able to correctly model over-stroke displacement behaviour for non-linear time history analyses. The DCCSS model was augmented with a friction model capable of accounting for torsional effects, axial load, and velocity variabilities. Comparison with non-linear dynamic analysis outcomes shows that the forces and displacements in the over-stroke sliding regime are predictable and therefore useful for the designer.
... [24][25][26] Moreover, base isolation and energy dissipation devices have been widely used for seismic damage mitigation in recent years. [27][28][29] The rational employment of isolation bearings goes far towards improving the seismic capacity of the structure. Although research on new bearing is emerging, 30 the traditional friction bearing is still the mainstream in current applications. ...
It is generally perceived that ground motion duration has an effect on structural seismic response and damage, despite the neglect of current seismic codes. Based on friction SDOF systems, this paper investigates the duration effect of ground motions on seismic responses and damage of sliding bearings. Ground motions are divided into long-duration (LD) and short-duration (SD) cases, taking the significant duration of 25s as the boundary. Each case consists of natural records and spectrally equivalent artificial ground motions to decouple duration from other earthquake characteristics. Results from response history analyses implicate that duration has hardly any effect on seismic responses of the system exhibiting an approximate linear elasticity. Nevertheless, for systems with distinct frictional nonlinearity, selecting LD ground motions as seismic inputs usually leads to a conservative result. By performing incremental dynamic analysis (IDA), nonlinear systems in SD cases bear 10% higher damage risk than those in LD cases without considering the influence of temperature rise. The same is true for systems with a small friction coefficient of 0.005 when earthquakes are in the low intensity range. It was also found that damage exceedance probabilities of these small friction coefficient systems are almost unaffected by the duration as the peak ground acceleration increases to more than 0.6g. When the effect of temperature rise caused by friction is considered, the damage exceedance probability in LD cases is higher than SD cases. The damage probability of friction SDOF system under LD earthquake will be underestimated without considering the influence of temperature rise.
