• Earthquakes and Structures
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• v.3 no.5
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• pp.629-647
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• 2012

Multiple acceleration sequences of earthquake ground motions have been observed in many regions of the world. Such ground motions can cause large damage to the structures due to accumulation of inelastic deformation from the repeated sequences. The dynamic analysis of inelastic structures under repeated acceleration sequences generated from simulated and recorded accelerograms without sequences has been recently studied. However, the characteristics of recorded earthquake ground motions of multiple sequences have not been studied yet. This paper investigates the gross characteristics of earthquake records of multiple sequences from an engineering perspective. The definition of the effective number of acceleration sequences of the ground shaking is introduced. The implication of the acceleration sequences on the structural response and damage of inelastic structures is also studied. A set of sixty accelerograms is used to demonstrate the general properties of repeated acceleration sequences and to investigate the associated structural inelastic response.

• Earthquakes and Structures
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• v.9 no.5
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• pp.957-981
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• 2015

Earthquakes occur as a cluster in many regions around the world where complex fault systems exist. The repeated shaking usually induces accumulative damage to affected structures. Damage accumulation in structural systems increases their level of degradation in stiffness and also reduces their strength. Many existing analytical tools of modeling RC structures lack the salient damage features that account for stiffness and strength degradation resulting from repeated earthquake loading. Therefore, these tools are inadequate to study the response of structures in regions prone to multiple earthquakes hazard. The objective of this paper is twofold: (a) develop a tool that contains appropriate damage features for the numerical analysis of RC structures subjected to more than one earthquake; and (b) conduct a parametric study that investigates the effects of multiple earthquakes on the response of RC moment resisting frame systems. For this purpose, macroscopic constitutive models of concrete and steel materials that contain the aforementioned damage features and are capable of accurately capturing materials degrading behavior, are selected and implemented into fiber-based finite element software. Furthermore, finite element models that utilize the implemented concrete and steel stress-strain hysteresis are developed. The models are then subjected to selected sets of earthquake sequences. The results presented in this study clearly indicate that the response of degrading structural systems is appreciably influenced by strong-motion sequences in a manner that cannot be predicted from simple analysis. It also confirms that the effects of multiple earthquakes on earthquake safety can be very considerable.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.147-154
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• 2002

Dynamic response analysis are conducted for a floating bridge subjected to multiple support earthquake excitation. The floating bridge used in this study is supported by discrete floating pontoons and horizontal pretension cables supported at both ends of the bridge. The bridge is modeled with finite elements and the hydrodynamic added mass and added damping due to the surrounding fluid around pontoons are obtained using boundary elements. Multiple support excitation is introduced at both ends of the bridge and the time history response is compared to that of a simultaneous excitation. The results shows that the differences between two results are not so large except for cable tension for which the multiple support excitation yields larger values. During the analysis the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.589-605
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• 2023

This paper investigates the ductility demands of steel frames equipped with self-centring fuses under near-fault earthquake motions considering multiple yielding stages. The study is commenced by verifying a trilinear self-centring hysteretic model accounting for multiple yielding stages of steel frames equipped with self-centring fuses. Then, the seismic response of single-degree-of-freedom (SDOF) systems following the validated trilinear self-centring hysteretic law is examined by a parametric study using a near-fault earthquake ground motion database composed of 200 earthquake records as input excitations. Based on a statistical investigation of more than fifty-two (52) million inelastic spectral analyses, the effect of the post-yield stiffness ratios, energy dissipation coefficient and yielding displacement ratio on the mean ductility demand of the system is examined in detail. The analysis results indicate that the increase of post-yield stiffness ratios, energy dissipation coefficient and yielding displacement ratio reduces the ductility demands of the self-centring oscillators responding in multiple yielding stages. A set of empirical expressions for quantifying the ductility demands of trilinear self-centring hysteretic oscillators are developed using nonlinear regression analysis of the analysis result database. The proposed regression model may offer a practical tool for designers to estimate the ductility demand of a low-to-medium rise self-centring steel frame equipped with self-centring fuses progressing in the ultimate stage under near-fault earthquake motions in design and evaluation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.376-383
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• 2003

For more rational and economical seismic design of long span bridges, it is essential to include in the analysis the effects of multiple input motions and structural or soil nonlinearity which are not considered in the current design practice. In this paper, the effects of these factors on the seismic behavior of long span bridges are studied. First, for the effect of multiple input motions, we take into account the differences in arrival times of seismic waves. To consider nonlinear soil properties we utilize SHAKE which is based on the equivalent linearization method. As a numerical example, a cable-stayed bridge is modelled using the analytical procedures described above. It is shown from the results that the these factors influence the seismic response of the bridge significantly and should never be neglected in design.

• Structural Monitoring and Maintenance
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• v.6 no.4
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• pp.347-364
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• 2019

Two seismic response data from the CSMIP strong motion instrumentation of Pacoima dam are selected: San Fernando earthquake (Jan 13, 2001; ML=4.3) and Newhall earthquake (Sept. 1, 2011; ML=4.2), for the identification of the dam system. To consider the spatially nonuniform input ground motion along the dam abutment, the subspace identification technique with multiple-input and multiple-output is used to extract the dynamic behavior of the dam-reservoir interaction system. It is observed that the dam-reservoir interaction is significant from the identification of San Fernando earthquake data. The influence of added mass (from the reservoir) during strong ground motion will create a tuned-mass damper phenomenon on the dam body. The fundamental frequency of the dam will be tuned to two different frequencies but with the same mode shapes. As for the small earthquake event, the dam-reservoir interaction is insignificant.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.27-33
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• 2004

Dynamic response analysis is conducted for a floating bridge subjected to multiple support earthquake excitation. The floating bridge used in this study is supported by discrete floating pontoons and horizontal pretension cables supported at both ends of the bridge. The bridge is modeled with finite elements and the hydrodynamic added mass and added damping due to the surrounding fluid around pontoons are obtained using boundary elements. During the analysis the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients. Multiple support excitation is introduced at both ends of the bridge and the time history response is compared to that of a simultaneous excitation. The results show that the multiple support excitation yields larger values in some responses. for example in cable tensions. than the sumultaneous excitation.

• Earthquakes and Structures
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• v.17 no.3
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• pp.317-327
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• 2019

High-speed railway bridge piers in seismically active area may be subjected to multiple earthquakes and then produce cumulative residual deformation. To study the cumulative residual deformation of high-speed railway bridge piers under multiple earthquakes, a nonlinear numerical analytical model with multi-DOF (MDOF) system is presented and validated against two shaking table tests in this paper. Based on the presented model, a simple supported beam bridge pier model of high-speed railway is established and used to investigate the cumulative residual deformation of high-speed railway bridge pier under mainshock-aftershock sequences and swarm type seismic sequences. The results show that the cumulative residual deformation of the bridge pier increases with earthquake number, and the increasing rates are different under different earthquake number. The residual deformation of bridge pier subjected to multiple earthquakes is accumulated and may exceed the limit of code.

• Journal of Information Processing Systems
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• v.17 no.1
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• pp.14-27
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• 2021

Strong earthquakes have caused substantial losses in recent years, and earthquake risk prevention has aroused a significant amount of attention. Earthquake risk prevention products can help improve the self and mutual-rescue abilities of people, and can create convenient conditions for earthquake relief and reconstruction work. At present, it is difficult for earthquake risk prevention information systems to meet the information requirements of multiple scenarios, as they are highly specialized. Aiming at mitigating this shortcoming, this study investigates and analyzes four user roles (government users, public users, social force users, insurance market users), and summarizes their requirements for earthquake risk prevention products in the whole disaster chain, which comprises three scenarios (pre-quake preparedness, in-quake warning, and post-quake relief). A targeted recommendation rule base is then constructed based on the case analysis method. Considering the user's location, the earthquake magnitude, and the time that has passed since the earthquake occurred, a targeted recommendation model is built. Finally, an Android APP is implemented to realize the developed model. The APP can recommend multi-form earthquake risk prevention products to users according to their requirements under the three scenarios. Taking the 2019 Lushan earthquake as an example, the APP exhibits that the model can transfer real-time information to everyone to reduce the damage caused by an earthquake.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.1
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• pp.29-36
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• 2014

In industrial facilities sites, the conventional method determining the earthquake magnitude (M) using earthquake ground-motion records is generally not applicable due to the poor quality of data. Therefore, a new methodology is proposed for determining the earthquake magnitude in real-time based on the amplitude measures of the ground-motion acceleration mostly from S-wave packets with the higher signal-to-ratios, given the Vs30 of the site. The amplitude measures include the bracketed cumulative parameters and peak ground acceleration (As). The cumulative parameter is either CAV (Cumulative Absolute Velocity) with 100 SPS (sampling per second) or BSPGA (Bracketed Summation of the PGAs) with 1 SPS. The arithmetic equations to determine the earthquake magnitude are derived from the CAV(BSPGA)-As-M relations. For the application to broad ranges of earthquake magnitude and distance, the multiple relations of CAV(BSPGA)-As-M are derived based on worldwide earthquake records and successfully used to determine the earthquake magnitude with a standard deviation of ${\pm}0.6M$.