Period Of Ground Motion Research Articles

Dynamic behavior and applicability of lead alloy absorber

The paper describes the damping effect of lead alloy absorber (LAA) by shake table test and finite element method of a kind of high-voltage electrical equipment, LW11-252/Q SF6 Circuit Breaker (LSCB). The strain reduction of the porcelain bushing of LSCB is defined as the damping effect of LAA in the paper based on the damage pattern of test equipment under earthquake. The test results show that LAA has reduced the acceleration response and strain response of the LSCB, at the same time, it does not increase the displacement response of the LSCB. There is a reduction of 30% in the strain of porcelain pipe. Moreover, the stronger the input ground motion is, the larger the reduction will be. The finite element method also indicates the damping effect of LAA, especially under ground motions with significant long period contents and ground motions with velocity pulse. Combined with the test results and calculation results, the paper gives the applicability of LAA finally.

Engineering assessment of seismic hazard and long period ground motions at the Bolu Viaduct Site following the November 1999 earthquake

The Mw 7.1 earthquake of November 12, 1999 severely damageda 2.5 km long viaduct on a stretch under construction of theIstanbul-Ankara motorway, 18 km W of Bolu. The fault rupture crossedthe viaduct with an observed offset close to 1.5 m; the viaduct decksuffered large permanent displacements but did not collapse.Seismic hazard at the site appears to be governed by characteristicearthquakes occurring every few hundred years both on the Duzce faultand on the main stretch of North Anatolian fault (NAF). Smaller activefaults near the site also contribute to the hazard.We investigate how a reliable design response spectrum of displacement canbe constructed for the viaduct site using both probabilistic and deterministictools. After checking the applicability of known attenuation relations againstrecorded data, we illustrate a hazard analysis that incorporates acharacteristic earthquake model for the relevant faults, and accounts forstatistical directivity effects on the Duzce fault. Constant-risk responsespectra up to 3 s are thus obtained for different return periods. Syntheticmotions at the site are generated next, using a known source model, inorder to explore the features of the displacement response spectrum atvibration periods in the range between 1s and 6 s, in which the dominantresponse of the viaduct deck, uncoupled from the piers, occurs. Adiscussion of results follows.

ランダム応答理論に基づく短周期地震動の統計的評価法 : 震源断層のランダムな不均質性が地震動の共分散応答に及ぼす影響

ランダム応答理論に基づく短周期地震動の統計的評価法 : 震源断層のランダムな不均質性が地震動の共分散応答に及ぼす影響

BRACED FRAMES WITH HYSTERETIC DISSIPATIVE DEVICES: SEISMIC RESPONSE AND DESIGN CRITERIA

The seismic behaviour of elastic braced frames with hysteretic dissipative devices is investigated. The analysis is carried out using a simplified single degree of freedom model that is deduced on the basis of an equivalence criterion between one-storey and multi-storey braced frames. The criterion allows one to characterise the structure by means of a few global parameters, such as the fundamental period of vibration, the ratio between the fundamental period and that of the correspondent unbraced frame, and the behaviour factor. The combined effect of design values of structural parameters and the energy frequency content of the input is stressed by evaluating the power spectral density of the stationary phase of the response. Consistent energy, displacement and strength response spectra are shown. The results elucidate the different behaviour of short and medium period structures with respect to the predominant period of ground motion. For each of the two classes, design criteria and guidelines for choosing the optimal values of the structural parameters are summarised. Four design examples are presented in order to demonstrate the effectiveness of the proposed criteria.

Characterizing Crustal Earthquake Slip Models for the Prediction of Strong Ground Motion

INTRODUCTION A large amount of work has been done in recent years to estimate the distribution of slip on the fault surface during earthquakes. Generally, these slip models are derived from longer period ground motions: strong-motion velocity and displacement, and teleseismic velocity seismograms. At these longer periods, ground motions are predominantly deterministic and their waveforms can in general be accurately modeled using simple descriptions of the source and crustal structure. The opposite situation exists for the prediction of high-frequency strong ground motions. Ground motions at high frequencies are predominantly stochastic, and their waveforms in general cannot be accurately modeled using simple descriptions of the source and crustal structure. However, preliminary evidence ( e.g. , Hartzell et al. , 1996; Kamae and Irikura, 1998; Somerville, 1993; Somerville et al ., 1996; Wald et al. , 1988) suggests that variable slip models derived from longer-period ground-motion recordings are relevant for the prediction of higher-frequency ground motions. For...

New building code requirements for the seismic design of tall buildings near active faults

The seismic provisions in the new 1997 edition of the Uniform Building Code (UBC) contain significant changes affecting the seismic resistant design of buildings. For buildings in California, the most significant change is related to the amplification of forces in areas near major active faults. This is done through the introduction of a near-source factor. This factor affects the design of buildings throughout the spectral range, but particularly affects mid-rise and high-rise buildings owing to their response to long period ground motions for which the near source effect is most pronounced. This paper provides an overview of the code change, a detailed discussion of ground motion mapping in the near field, and a discussion of the effect of the code change on tall buildings. Preliminary near-source maps are developed for the Los Angeles Basin. Studies are presented, comparing base shear values calculated based on the 1994 and 1997 editions of the Uniform Building Code. © 1997 John Wiley & Sons, Ltd.

New building code requirements for the seismic design of tall buildings near active faults

The seismic provisions in the new 1997 edition of the Uniform Building Code (UBC) contain significant changes affecting the seismic resistant design of buildings. For buildings in California, the most significant change is related to the amplification of forces in areas near major active faults. This is done through the introduction of a near-source factor. This factor affects the design of buildings throughout the spectral range, but particularly affects mid-rise and high-rise buildings owing to their response to long period ground motions for which the near source effect is most pronounced. This paper provides an overview of the code change, a detailed discussion of ground motion mapping in the near field, and a discussion of the effect of the code change on tall buildings. Preliminary near-source maps are developed for the Los Angeles Basin. Studies are presented, comparing base shear values calculated based on the 1994 and 1997 editions of the Uniform Building Code. © 1997 John Wiley & Sons, Ltd.

Conditions that give rise to unusually large long period ground motions

AbstractSeveral ground motion conditions that are of little concern for conventional structures can be quite important for structures having natural periods longer than 1 s. Firstly, a large long‐period pulse of motion, due to the effect of rupture propagation (directivity), is observed in the direction normal to the fault at strong motion stations located close to the fault. The fault‐normal motions are about twice as large as the fault‐parallel motions for periods longer than about 1 s. The importance of this effect, especially in strike‐slip earthquakes, has probably been underestimated in existing ground motion attenuation relations because until very recently most of the near‐fault strong motion data from large earthquakes have come from thrust earthquakes, for which directivity effects are usually less pronounced. Near‐fault recordings of the 1971 San Fernando, 1979 Imperial Valley, 1989 Loma Prieta, and 1992 Landers, California, earthquakes show large directivity effects. We describe the systematic characteristics of the directivity effect derived from empirical analysis of recorded data and from synthetic seismogram modeling of these data. Secondly, the trapping and amplification of long period waves by sedimentary basins can generate amplitudes that are significantly larger than those calculated from simple ID models of site resonance. Using a ID model with a plane wave incident from below, it is not possible to trap energy in the near‐surface sediment layers. However, for 2D and 3D basin models, waves become trapped as they enter the thickening edge of a basin, and partially escape as they reach the thinning edge of the basin. We show evidence from both recorded data and synthetic seismogram modeling of the San Fernando and Loma Prieta earthquakes that the surface waves are confined to the basin and are not recorded at rock sites adjacent to the basin. This implies that the long period ground motion response at sites within these basins is not adequately represented by the conventional approach of vertically propagating an adjacent rock recording through a ID soil column.

新潟県南部の浅発地震によるやや長周期地震動の解析

新潟県南部の浅発地震によるやや長周期地震動の解析

気象庁一倍強震計の変位波形を用いた速度応答値の推定

A method for estimation of maximum velocity response to ground motions as a function of peak displacement and period of ground motion and some amount of information from seismograms is proposed and applied to some records. In this method, a displacement record is replaced by a harmonic motion and the velocity response is calculated from it. The way to get appropriate numbers of cycles of records is obtained. Studies on the number of cycles about the correlation with the site amplification characteristics and the frequency distribution are carried out. An attenuation relation for velocity response is obtained using a peak displacement attenuation function.

ESTIMATION OF LONG PERIOD RESPONSE SPECTRA WITH NONLINEAR SLOSHING ANALYSIS OF CYLINDRICAL TANKS

In this study, the effect of nonlinear boundary conditions at liquid surface on sloshing height of cylindrical tank under vertical and horizontal ground motions is discussed in comparison to linear analysis. It is found that this effect mainly depends on both dimensionless sloshing height and dimensionless liquid depth as far as smaller sloshing height is concerned, and simple formula estimating this effect is proposed. On the level of observed large sloshing height due to the 1983 Nihonkai-chubu earthquake, sloshing height calculated under nonlinear conditions are estimated about 10-25% larger than those under linear conditions. Taking into account this effect, response spectra of long period ground motions deduced from observed sloshing height are found nearly equal to two-dimensional response spectra calculated from strong motion seismograms.

Evaluation of Earthquake-Induced Sliding in Rockfill Dams

The relation between the factor of safety obtained from dynamic response analyses on arbitrary potential sliding surface of a rockfill dam and the one obtained from conventional method such as slice method has been made clear by introducing a concept of equivalent instantaneous seismic coefficient. Throughout many numerical experiments of dynamic response analyses conducted on a typical rockfill dam section with sinusoidal ground motions of various kinds of accelerations and periods, a simple expression for the sliding permanent displacements has been obtained as a function of maximum equivalent instantaneous seismic coefficient and duration of sliding which is independent of the scale and location of sliding surface, the period of ground motion and the amplitude of ground acceleration. This formula has been applied to the simplified evaluation for the sliding permanent displacements in the cases with the ground motions of recorded accelerograms. Acceleration response spectra of many recorded accelerograms have been calculated and the ratio of each maximum value to peak ground acceleration has been plotted against corresponding predominant period. With this diagram the amplitude of equivalent sinusoidal ground acceleration has been specified as 0. 5 to 0. 6 of peak ground acceleration in conservative side. Combining above formula with the magnification factors of the equivalent instantaneous seismic coefficients in the potential sliding circles near crest, an expression for the relationship between the amplitude of above equivalent sinusoidal ground acceleration and the earthquake-induced sliding displacement at near crest has been derived. Giving certain amount of allowable permanent displacement, an earthquake-resistant design diagram for rockfill dams concerning with the equivalent sinusoidal ground acceleration has been proposed.