Vertical Stiffness of Elastomeric and Lead–Rubber Seismic Isolation Bearings

Warn, Gordon P.; Whittaker, Andrew S.; Constantinou, Michael C.

doi:10.1061/(asce)0733-9445(2007)133:9(1227)

Cited by 123 publications

(95 citation statements)

References 6 publications

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“…The axial (i.e., vertical) stiffness K v of the HDRB model is obtained from the two-spring model of Koh and Kelly (1987), which has been validated experimentally by Warn et al (2007). The coupling of horizontal and vertical behaviour is due to: (1) the variation of the shear stiffness with axial load and (2) the dependence of axial stiffness on the magnitude of the lateral displacement (Kumar et al 2014).…”

Section: High Damping Rubber Isolators Model Descriptionmentioning

confidence: 99%

“…The material, geometric and mechanical properties of the elastomeric bearings for this reference bridge configuration are reported in Table 3; calculations of properties from the primary parameters have been carried out in accordance with the formulae reported in Kumar et al (2014). Reference has been made to Kelly (1997) for the evaluation of the critical buckling load and adjusted (effective) bearing geometrical properties, and to Warn et al (2007), with reference mainly to the horizontal-vertical behaviour interaction. Figure 7 reports the time history of the deck horizontal displacement, d hd , and of the pier cap displacement, d hp , for the first record (#1) considered in this study.…”

Section: Seismic Response Of the Reference Bridge With Emphasis On Thmentioning

confidence: 99%

“…According to Gent and Lindley (1959), cavitation occurs at a negative pressure of about 2.5 G, where G is the shear modulus of the bearing, obtained experimentally from testing at moderate shear strain (between 100 and 200 %) under nominal axial loads (Kumar et al 2014). The load deformation of the isolators under pure tensile loads has been described by Constantinou et al (2007) and Warn et al (2007). Yang et al (2010) tested bearings that had a shear modulus of 0.55 MPa under pure tensile loads and identified that the bearings exhibit cavitation when the tensile strains exceeded 1.0 % (corresponding to tensile stress between 1 and 2 MPa).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

Tubaldi

Mitoulis

Ahmadi

et al. 2016

Bull Earthquake Eng

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This paper investigates the potential tensile loads and buckling effects on rubber-steel laminated bearings on bridges. These isolation bearings are typically used to support the deck on the piers and the abutments and reduce the effects of seismic loads and thermal effects on bridges. When positive means of fixing of the bearings to the deck and substructures are provided using bolts, the isolators are exposed to the possibility of tensile loads that may not meet the code limits. The uplift potential is increased when the bearings are placed eccentrically with respect to the pier axis such as in multi-span simply supported bridge decks. This particular isolator configuration may also result in excessive compressive loads, leading to bearing buckling or in the attainment of other unfavourable limit states for the bearings. In this paper, an extended computer-aided study is conducted on typical isolated bridge systems with multi-span simply-supported deck spans, showing that elastomeric bearings might undergo tensile stresses or exhibit buckling effects under certain design situations. It is shown that these unfavourable conditions can be avoided with the rational design of the bearing properties and in particular of the shape factor, which is the geometrical parameter controlling the axial bearing stiffness and capacity for a 123Bull Earthquake Eng (2016) 14:1285-1310 DOI 10.1007 given shear stiffness. Alternatively, the unfavourable conditions could be reduced by reducing the flexural stiffness of the continuity slab.

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Section: High Damping Rubber Isolators Model Descriptionmentioning

confidence: 99%

Section: Seismic Response Of the Reference Bridge With Emphasis On Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

Tubaldi

Mitoulis

Ahmadi

et al. 2016

Bull Earthquake Eng

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show abstract

“…However, according to Equation 5, this range of shape factors results in vertical stiffness that ranges from one to several thousand times greater than the horizontal stiffness. As a result, isolation systems composed of bearings detailed with high shape factors (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) typically have vertical isolation periods ranging from 0.03 to 0.15 second. Consequently, the vertical isolation frequencies can align with the dominant frequencies of the vertical spectrum, leading to significant amplification of the vertical acceleration.…”

Section: Rubber Covermentioning

confidence: 99%

“…Therefore, isolation systems composed of elastomeric bearings detailed with high shape factors, e.g., 15-30, provide only horizontal isolation. Figure 2 presents the shear force-horizontal deformation and vertical force-vertical deformation response of a low-damping natural rubber bearing [23]. While damping in natural rubber bearings is neither hysteretic nor viscous the shear force-horizontal deformation relationship is often modeled using either: (1) a linear viscous representation; or (2) a bilinear hysteretic representation.…”

Section: Rubber Covermentioning

confidence: 99%

A Review of Seismic Isolation for Buildings: Historical Development and Research Needs

2012

Self Cite

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Seismic isolation is a technique that has been used around the world to protect building structures, nonstructural components and content from the damaging effects of earthquake ground shaking. This paper summarizes current practices, describes widely used seismic isolation hardware, chronicles the history and development of modern seismic isolation through shake table testing of isolated buildings, and reviews past efforts to achieve three-dimensional seismic isolation. The review of current practices and past research are synthesized with recent developments from full-scale shake table testing to highlight areas where research is needed to achieve full seismic damage protection of buildings. The emphasis of this paper is on the application of passive seismic isolation for buildings primarily as practiced in the United States, though systems used in other countries will be discussed.

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Effects of near‐fault ground motions on the nonlinear dynamic response of base‐isolated r.c. framed buildings

Mazza

Vulcano

2011

Earthq Engng Struct Dyn

133

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SUMMARYNear-fault ground motions are characterized by long-period horizontal pulses and high values of the ratio between the peak value of the vertical acceleration, PGA V , and the analogous value of the horizontal acceleration, PGA H , which can become critical for base-isolated (BI) structures. The objective of the present work is to check the effectiveness of the base isolation of framed buildings when using HighDamping-Rubber Bearings (HDRBs), taking into consideration the combined effects of the horizontal and vertical components of near-fault ground motions. To this end, a numerical investigation is carried out with reference to BI reinforced concrete buildings designed according to the European seismic code (Eurocode 8). The design of the test structures is carried out in a high-risk region considering (besides the gravity loads) the horizontal seismic loads acting alone or in combination with the vertical ones and assuming different values of the ratio between the vertical and horizontal stiffnesses of the HDRBs. The nonlinear seismic analysis is performed using a step-by-step procedure based on a two-parameter implicit integration scheme and an initial-stress-like iterative procedure. At each step of the analysis, plastic conditions are checked at the potential critical sections of the girders (i.e. end sections of the sub-elements in which a girder is discretized) and columns (i.e. end sections), where a bilinear moment-curvature law is adopted; the effect of the axial load on the ultimate bending moment (M-N interaction) of the columns is also taken into account. The response of an HDRB is simulated by a model with variable stiffness properties in the horizontal and vertical directions, depending on the axial force and lateral deformation, and linear viscous damping.

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Vertical Stiffness of Elastomeric and Lead–Rubber Seismic Isolation Bearings

Cited by 123 publications

References 6 publications

A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

A parametric study on the axial behaviour of elastomeric isolators in multi-span bridges subjected to horizontal seismic excitations

A Review of Seismic Isolation for Buildings: Historical Development and Research Needs

Effects of near‐fault ground motions on the nonlinear dynamic response of base‐isolated r.c. framed buildings

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