The effective number of cycles of earthquake ground motion

Hancock, Jonathan; Bommer, Julian J.

doi:10.1002/eqe.437

Cited by 88 publications

(28 citation statements)

References 49 publications

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“…While amax was directly obtained from each accelerogram data, representative values of each ground motion were selected to determine aav, N(amax) and Ntot. In particular, a low-amplitude cut-off level was used to prevent many cycles of small amplitude from inappropriately influencing the obtained results (Hancock and Boomer 2005). According to Seed et al (1995), loading cycles having amplitudes less than about 30 % of the maximum amplitude do not have a significant contribution to the onset of liquefaction and, therefore, a cut-off level of 0.30 amax was adopted in the present study.…”

Section: Location and Magnitude Of The Singular Peakmentioning

confidence: 99%

Energy-based evaluation of liquefaction potential under non-uniform cyclic loading

Azeiteiro

Coelho

Taborda

et al. 2017

Soil Dynamics and Earthquake Engineering

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Uniform cyclic loading is commonly used in laboratory tests to evaluate soil resistance to earthquake-induced liquefaction, even if the cyclic stresses induced by earthquakes in the field are highly irregular. This paper discusses the use of stress and energy-based approaches to evaluate the liquefaction resistance of sand under irregular loading. Results of undrained cyclic triaxial tests including a large-amplitude singular peak loading cycle are presented and compared to those obtained using uniform loading. Although samples are subjected to loading patterns which would have been deemed equivalent by conventional stress-based methods, the number of cycles required to trigger liquefaction strongly depends on the amplitude and location of the peak within the loading history.Conversely, a unique relationship exists between the accumulation of dissipated energy per unit volume, computed using stress and strain measurements, and the observed residual pore water pressure build-up for all tests, throughout the entire cyclic loading application. This demonstrates that conventional laboratory tests using uniform loading conditions can be employed to determine liquefaction resistance if their interpretation is carried out based on energy principles.

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Section: Location and Magnitude Of The Singular Peakmentioning

confidence: 99%

Energy-based evaluation of liquefaction potential under non-uniform cyclic loading

Azeiteiro

Coelho

Taborda

et al. 2017

Soil Dynamics and Earthquake Engineering

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“…The importance of ground-motion duration in geotechnical engineering is universally recognized, the parameter most widely adopted for this purpose usually being the number of cycles of motion (Liu et al, 2001;Green and Terri, 2005;Hancock and Bommer, 2005). Surprisingly, the number of cycles is found to be very poorly correlated with duration .…”

Section: Introductionmentioning

confidence: 99%

Empirical Equations for the Prediction of the Significant, Bracketed, and Uniform Duration of Earthquake Ground Motion

Bommer¹,

Stafford²,

Alarcón³

2009

Bulletin of the Seismological Society of America

236

131

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The complete characterization of earthquake ground motion includes the length of the interval of strong shaking as well as the amplitude and frequency content of the time series. There are relatively few published equations available for the prediction of strong-motion duration from earthquakes, which may in part be a consequence of the fact that the duration of shaking has generally not been considered in structural engineering. Recognizing that there are many applications for which an estimate of the duration of ground motion is needed, this study presents new empirical predictive equations for a number of definitions of strong-motion duration using the records from the Next Generation of Attenuation (NGA) global database of accelerograms from shallow crustal earthquakes. The equations can be used to estimate ground-motion durations from shallow crustal earthquakes of magnitude between M w 4.8 and 7.9 at distances up to 100 km from the source.

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“…The first step of the method is to determine the equivalent effective number of cycles (N cy ) and the equivalent uniform shear strain amplitude (c dyn ) of the irregular shear strain-time histories for its transformation into the equivalent uniform ones. The equivalent number of cycles should be calculated directly from the acceleration records by using the peak-counting definitions (Malhotra 2002;Hancock and Bommer 2005), meanwhile the equivalent uniform shear strain amplitude has been confirmed as a function of the maximum shear strain amplitude, such as c dyn = 0.65 c max Annaki and Lee 1977) or c dyn = F(c max ) G where F and G are the experimental parameters (Matsuda and Hoshiyama 1992). The transformation procedure by using these methods has been developed and applied to Hyogo-ken Nanbu earthquake 1995 by Matsuda et al (2013b) and the obtained results of N cy and c dyn are shown in Table 7 for various maximum shear strain amplitudes.…”

Section: Estimation Of Post-cyclic Settlement Concerning the Effect Omentioning

confidence: 99%

A model for multi-directional cyclic shear-induced pore water pressure and settlement on clays

Nhàn

Matsuda

Sato

2017

Bull Earthquake Eng

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An estimation method for earthquake-induced pore water pressure and the postearthquake settlement of soft clay was developed by focusing on its Atterberg's limits and the direction of cyclic shearing. To clarify the fundamental characteristics of clays with different Atterberg's limits under multi-directional cyclic shear, normally consolidated specimens of Kaolinite clay, Tokyo bay clay and Kitakyushu clay were subjected to cyclic simple shear under the undrained condition with various cyclic shear directions and shear strain amplitudes, followed by the dissipation of cyclic shear-induced pore water pressure. The effects of undrained cyclic shear on the pore water pressure accumulation and postcyclic settlement were observed, and relationships with Atterberg's limits were then investigated. In conclusion, the pore water pressure accumulation and post-cyclic settlement induced by multi-directional cyclic shear increase considerably to a higher level compared with those generated by the uni-directional one and such a tendency is evident for clays with a wide range of Atterberg's limits. Comparisons of the results indicate that the soil with higher plasticity index shows the lower pore water pressure accumulation and post-cyclic settlement, irrespective of number of strain cycles and shear strain amplitude. Based on these results, a model for earthquake-induced pore water pressure and postearthquake settlement was developed by incorporating the Atterberg's limits as a function of experimental constants and the practical applicability was confirmed.

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The effective number of cycles of earthquake ground motion

Cited by 88 publications

References 49 publications

Energy-based evaluation of liquefaction potential under non-uniform cyclic loading

Energy-based evaluation of liquefaction potential under non-uniform cyclic loading

Empirical Equations for the Prediction of the Significant, Bracketed, and Uniform Duration of Earthquake Ground Motion

A model for multi-directional cyclic shear-induced pore water pressure and settlement on clays

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