Seismic Peak Research Articles

PEAK RESPONSE EVALUATION METHOD FOR SLIP-HYSTERETIC STRUCTURE ADDED WITH VISCO-ELASTIC DAMPER

This paper proposes a seismic peak response evaluation method for slip-hysteretic structure having a viscous or viscoelastic damper. Formulations to estimate equivalent vibration period and equivalent damping ratio of the slip-hysteretic structure subjected to random excitation are presented. The peak response evaluation method is based on equivalent linearization as well as spectrum modification and reduction, reflecting increase in equivalent vibration period and equivalent damping ratio. Accuracy of the evaluation method is validated through numerous time history analyses, over a wide range of viscous damping ratio, elastic vibration period, post-yield stiffness, slip strength ratio, ductility ratio, and earthquake type.

SEISMIC RESPONSE PREDICTION FOR STEEL BUILDINGS WITH VISCOUS DAMPERS DEPENDENT ON FRACTIONAL POWER OF VELOCITY BASED ON EQUIVALENT LINEARIZATION TECHNIQUE

This paper proposes a general method based on equivalent linearization technique using results of static pushover analysis with three dimensional frame model to predict seismic peak responses of steel structures with viscous dampers dependent on fractional power of velocity subjected to earthquakes. In this method, the equivalent damping coefficient at a given displacement is obtained by averaging damping coefficients of stationary vibration at displacement amplitude up to that displacement level. Time history response analyses were conducted to ensure accuracy of this method.

SEISMIC RESPONSE PREDICTION FOR STEEL BUILDINGS WITH HISTERETIC DAMPERS BASED ON EQUIVALENT LINEARIZATION TECHNIQUE

This paper proposes a general method based on equivalent linearization technique using results of static pushover analysis with three dimensional frame model to predict seismic peak responses of steel structures with hysteretic dampers subjected to earthquakes. In this method, the equivalent damping coefficient at a given displacement is obtained by averaging damping coefficients of stationary vibration at displacement amplitude up to that displacement level. Time history response analyses were conducted to ensure accuracy of this method.

PASSIVE CONTROL DESIGN METHOD BASED ON TUNING OF EQUIVALENT STIFFNESS OF BILINEAR OIL DAMPER

Simplified theories are proposed for seismic peak response evaluation and preliminary design of buildings with bilinear oil dampers. They are based on the single-degree-of-freedom (SDOF) idealization of multistory building, and produce the so-called “control performance curve” expressing the peak responses as a function of stiffnesses of all components, based on spectral characteristics of the earthquake. Against the target peak response required, the curve clearly shows necessary stiffness balance between damper and other elements. A rule to convert the SDOF design to multistory design, with a consideration to distribute damper stiffness over the building height, is also presented. Accuracy of the design approach is demonstrated via numerous time history simulations of a wide range of multiple-degrees-of-freedom (MDOF) models.

Quantifying subaqueous slope stability during seismic shaking: Lake Lucerne as model for ocean margins

Lakes can be used as model basins to investigate subaqueous slope stability under static and dynamic loading conditions. This study combines geophysical, sedimentological and in situ geotechnical methods with limit equilibrium calculations in order to discuss (i) the geological and sedimentological processes acting on submerged non-deltaic lateral slopes in perialpine, fjord-type Lake Lucerne (Central Switzerland); (ii) their control on physical and geotechnical properties that eventually affect the subaqueous stability conditions and slope failure initiation, and (iii) the quantitative assessment of subaqueous slope stability. Three detailed case studies are presented to describe and quantitatively reconstruct stability conditions of slopes that failed during a well-documented historic earthquake in 1601 A.D. and during a prehistoric Late Holocene earthquake around 2220 cal yr BP (both M w > 6). Glacio-lacustrine sedimentation dominated by suspension settling from meltwater plumes and slight overconsolidation from ice-grounding during small readvances of a generally retreating glacier lead to a peculiar glacial-to-postglacial lithologic slope succession that eventually was buried by the Holocene sediment drape. During past earthquake shaking, the slopes that were stable under static loading conditions (factor of safety of 1.5–2) failed along planar sliding surfaces that developed at the lithological boundary between fine-grained, thinly-laminated, slightly underconsolidated cyclic plume deposits with low undrained shear strength values above and overconsolidated, glacially-deformed, glacio-lacustrine deposits with excessive formation pore pressure below. Measured in situ shear strength characteristics and sediment geometries were implemented into limit equilibrium models that allow for quantitative reconstruction of critical ground accelerations of past earthquakes in Central Switzerland. Results reveal seismic peak ground acceleration (PGA) of ∼ 0.08 g and ∼ 0.14 g for the historic 1601 A.D. M w ∼ 6.2 earthquake and the prehistoric, ∼ 2220 cal yr B.P. earthquake, respectively. Additionally, results reveal that stability conditions change over relative short geological time scales because the postglacial sedimentation rate, which mainly controls the static weight of the slope sediment acting on the critical lithological boundary, turns out to be a key parameter in “charging” slopes susceptible to sliding.

非線形粘性ダンパーの等価剛性調節による制振構造の応答制御手法

Simplified theories are proposed for seismic peak response evaluation and preliminary design of buildings with bilinear oil dampers. They are based on the single-degree-of-freedom (SDOF) idealization of multistory building, and produce the so-called “control performance curve” expressing the peak responses as a function of stiffnesses of all components, based on spectral characteristics of the earthquake. Against the target peak response required, the curve clearly shows necessary stiffness balance between damper and other elements. A rule to convert the SDOF design to multistory design, with a consideration to distribute damper stiffness over the building height, is also presented. Accuracy of the design approach is demonstrated via numerous time history simulations of a wide range of multiple-degrees-of-freedom (MDOF) models.

Design stability and safety margins of the ETRR-2 core cooling system regarding seismic loads

Abstract The seismic design of a nuclear power plant includes two levels of design earthquake, the safe shutdown earthquake (SSE) and the operating basis earthquake (OBE). The OBE and SSE are considered in the nuclear power plant design as required by the IAEA safety regulations. A typical piping model for the ETRR-2 core cooling system includes ASME-class 1, 2 and 3 piping and was analyzed with regard to both IAEA safety regimes. A load combination, as stated by the IAEA Safety Guide 50-SG-S2, has been considered. The safety guide requires that the OBE should equal to at least one half SSE and that the plant should be shut down if exposed to earthquake intensity greater than the OBE. The results reflect the requirement for the precise design of a supporting system to accommodate for higher seismic peaks more than 0.2 g and the system needs to be more flexible.

Seismic constraints on mechanisms of deep earthquake rupture

Observations of the depth distribution of seismicity suggest that several mechanisms cause deep earthquakes. Cold subducting slabs exhibit a broad peak in seismicity between 300 and 530 km depth that is best explained by transformational faulting of metastable olivine. Cumulative seismic moment release increases sharply at ∼530 km depth in both cold and warm slabs, implying that events deeper than this are controlled by an equilibrium rather than a metastable phase change, which would be temperature‐dependent. This, together with the observation that deep seismicity predominates near the garnet‐rich upper boundary of the subducting plate (former oceanic crust), suggests that the transformation of garnet to perovskite, which may release considerable water, is integral in the cause of earthquakes deeper than 530 km, where most deep earthquakes occur.

Seismic Hazard for Selected Sites in Greece: A Bayesian Estimate of Seismic Peak Ground Acceleration

A procedure for estimating maximum values of seismic peak ground accelerationat the examined site and quantiles of its probabilistic distribution in a future timeinterval of a given length is considered. The input information for the method areseismic catalog and regression relation between peak seismic acceleration at a givenpoint and magnitude and distance from the site to epicenter (seismic attenuation law).The method is based on Bayesian approach, which simply accounts for influenceof uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sitesin Greece.

Comparison Between Recorded and Derived Seismic Peak Horizontal Ground Acceleration Data in Jordan

The isoseismal map for the earthquake that occurred in the Jordan Valley on 11 July 1927 was analyzed and used to develop peak ground acceleration (PGA) Attenuation relation for Jordan needed for use in relevant seismic hazard evaluation procedures. Strong motion data of earthquakes that occurred in Jordan and Israel during the last fifteen years were summarized. A comparison was made between recorded PGA9s and those calculated using the derived Attenuation relation and that developed by Esteva (1974) that is commonly used by experts in the region. The comparison showed that the derived relation is appropriate for estimating PGA values on alluvium foundations. The derived relation gave results close to those obtained using the Esteva (1974) relation.

The use of a multipole expansion technique to analyse large scale fracture processes and seismic recurrence effects in deep level mines

An efficient solution technique for the analysis of multiple interacting displacement discontinuities is described together with the implementation of a viscoplastic relaxation model for the simulation of observed time dependent seismic activity in deep level gold mines. The method is illustrated in relation to the mining of a parallel sided panel with attendant mobilization of fractures in the surrounding rock. A comparison is made between the case where mining is advanced continually by a constant increment every day and the case where mining is interrupted every seventh day corresponding to a weekend break. Some possible methods of analysing the seismic recurrence cycles that are induced by the mining are presented. For the simple cases studied it is found that there is no apparent correlation between successive seismic energy release peaks. It appears that slightly more seismic energy is released in the continuous mining cycle than in the case where the mining is interrupted every seventh day.

Conversion between seismic intensity and peak ground shaking

In this paper, the relationships between seismic intensity and peak ground shaking are studied under no specific condition, separately or simultaneously considering the number of building storey and site category, based on data of mean peak values of horizontal ground motion recorded during strong earthquakes. Then, according to the statistical results, the variation of mean peak value with intensity rating is discussed, and schemes of peak ground velocity, peak ground acceleration or response spectrum of an designed earthquake converted from intensity rating are recommended. Finally, a methodology of converting seismic intensity from response spectrum of design earthquake is also discussed, and the conversion scheme is recommended.

Improved method of generation of artificial time‐histories, rich in all frequencies, from floor spectra

AbstractA method to generate artificial time‐histories from given floor response spectra is presented in this paper. The original method proposed by Levy and Wilkinson1 is modified. New iterative equations are developed, based on extensive computational experimentation, to speed up and stabilize the convergence process. The present approach, when applied to spectra with peaks in the high frequency range (40 to 100 Hz) along with seismic peaks, converges very closely to the target spectra within eight iterations regardless of damping values. The original computer program for synthetic time‐history generation was developed on the UNIVAC 1100 series computer. This program was converted to work on the IBM PC. The PC based program ‘MICRO‐SEIM’ saves the response spectra generated at each iteration and the final synthetic time‐history on the PC diskette. The post processing program reads those saved data from the diskette and plots the spectra and time‐history.

Analysis of seismic peak amplitudes from underground nuclear explosions

abstract Ground-motion data recorded from 99 underground nuclear event ranging in yield from about 1 to 1200 kilotons are analyzed. The data were measured at more than 500 different stations with the source-to-station distance ranging from less than 1 to approximately 600 kilometers. More than 2,900 acceleration, displacement and velocity peak resultant vector data points are included in the analysis. A comparison of the results of the statistical analysis with expected results using cube-root of yield scaling concepts, shows that the peak amplitude of displacement cube-root scales whereas peak acceleration and velocity do not cube-root scale. Relative differences in the yield and distance exponents, n and m, obtained from the statistical analysis, are explained in terms of differences in the frequency content of recorded ground motions. The observed peak amplitude measurements from the events Boxcar and Benham are compared with predictions based on the statistical analyses.