• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.347-362
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• 2005

The input energy to a base-isolated (BI) building during an earthquake is considered and formulated in the frequency domain. The frequency-domain approach for input energy computation has some notable advantages over the conventional time-domain approach. Sensitivities of the input energy to the BI building are derived with respect to uncertain parameters in the base-isolation system. It is demonstrated that the input energy can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum of acceleration) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for deriving the sensitivities of the input energy to the BI building with respect to uncertain parameters. The sensitivity expressions provide us with information on the most unfavorable combination of the uncertain parameters which leads to the maximum energy input.

• Earthquakes and Structures
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• v.16 no.4
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• pp.487-499
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• 2019

Energy-based seismic design of structures has gradually become prominent in today's structural engineering investigations because of being more rational and reliable when it is compared to traditional force-based and displacement-based methods. Energy-based approaches have widely taken place in many previous studies and investigations and undoubtedly, they are going to play more important role in future seismic design codes, too. This paper aims to compute the maximum earthquake energy input to elastic single-degree-of-freedom (SDOF) systems for selected real ground motion records. A data set containing 100 real ground motion records which have the same site soil profiles has been selected from Pacific Earthquake Research (PEER) database. Response time history (RTH) analyses have been conducted for elastic SDOF systems having a constant damping ratio and natural periods of 0.1 s to 3.0 s. Totally 3000 RTH analyses have been performed and the maximum mass normalized earthquake input energy values for all records have been computed. Previous researchers' approaches have been compared to the results of RTH analyses and an approach which considers the pseudo-spectral velocity with Arias Intensity has been proposed. Graphs of the maximum earthquake input energy versus the maximum pseudo-spectral velocity have been obtained. The results show that there is a good agreement between the maximum input energy demands of RTH analysis and the other approaches and the maximum earthquake input energy is a relatively stable response parameter to be used for further seismic design and evaluations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.243-249
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• 2003

The characteristics of harmonic phase angles and phase angle differences contained in earthquake ground motions such as El Centre 1530 NS, Taftl 1952 NS, Hachinohe 1968 NS and Mexico 1985 are figured, which have been mostly overlooked in contrast with the importance placed on harmonic amplitudes. And, energy input spectrum of structures excited by such an earthquake motion is expressed with smoothed Fourier amplitude spectrum. In dynamic response analysis, there must be earthquake ground accelerations which contain the phase angle, the phase angle difference and energy input spectrum characteristics of the zone considered to be constructed building structures. To make clear the importance of phase angle differences, 4-earthquake ground motions are normalized by 200 gal and energy input spectrum characteristics of normalized 4-earthquake ground motions are compared.

• Earthquakes and Structures
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• v.9 no.6
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• pp.1133-1152
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• 2015

A frequency-domain method is developed for evaluating the earthquake input energy to two building structures connected by viscous dampers. It is shown that the earthquake input energies to respective building structures and viscous connecting dampers can be defined as works done by the boundary forces between the subsystems on their corresponding displacements. It is demonstrated that the proposed energy transfer function is very useful for clear understanding of dependence of energy consumption ratios in respective buildings and connecting viscous dampers on their properties. It can be shown that the area of the energy transfer function for the total system is constant regardless of natural period and damping ratio because the constant Fourier amplitude of the input acceleration, relating directly the area of the energy transfer function to the input energy, indicates the Dirac delta function and only an initial velocity (kinetic energy) is given in this case. Owing to the constant area property of the energy transfer functions, the total input energy to the overall system including both buildings and connecting viscous dampers is approximately constant regardless of the quantity of connecting viscous dampers. This property leads to an advantageous feature that, if the energy consumption in the connecting viscous dampers increases, the input energies to the buildings can be reduced drastically. For the worst case analysis, critical excitation problems with respect to the impulse interval for double impulse (simplification of pulse-type impulsive ground motion) and multiple impulses (simplification of long-duration ground motion) are considered and their solutions are provided.

• Earthquakes and Structures
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• v.2 no.2
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• pp.171-187
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• 2011

Rational scaling of design earthquake ground motions for tall buildings is essential for safer, risk-based design of tall buildings. This paper provides the structural designers with an insight for more rational scaling based on drift and input energy demands. Since a resonant sinusoidal motion can be an approximate critical excitation to elastic and inelastic structures under the constraint of acceleration or velocity power, a resonant sinusoidal motion with variable period and duration is used as an input wave of the near-field and far-field ground motions. This enables one to understand clearly the relation of the intensity normalization index of ground motion (maximum acceleration, maximum velocity, acceleration power, velocity power) with the response performance (peak interstory drift, total input energy). It is proved that, when the maximum ground velocity is adopted as the normalization index, the maximum interstory drift exhibits a stable property irrespective of the number of stories. It is further shown that, when the velocity power is adopted as the normalization index, the total input energy exhibits a stable property irrespective of the number of stories. It is finally concluded that the former property on peak drift can hold for the practical design response spectrum-compatible ground motions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.121-128
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• 2005

In this study the influences of ground motion characteristics and structural properties on energy demands were evaluated using 100 earthquake ground motions recorded in different soil conditions, and the results were compared with those of previous works. Results show that ductility ratios and the site conditions have significant influence on input energy. The ratio of hysteretic to input energy is considerably influenced by the ductility ratio and damping ratio, while site condition has minor effects.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.1
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• pp.9-19
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• 2016

Permanent deformation plays a key role in performance based earthquake resistant design. In order to estimate permanent deformation after earthquake, it is essential to secure reliable response history analysis(RHA) as well as earthquake scenario. This study focuses on permanent deformation of an inverted T-type wall under earthquake. The study is composed of two separate parts. The first one is on the verification of RHA and the second one is on an effect of input earthquake motion. The former is discussed in companion paper and the latter in this paper. In order to investigate the effect of an input earthquake motion on the permanent deformation, three bins of spectral matched real earthquake records with different magnitude, regions, epicentral distance are constructed. Parametric study was performed using the verified RHA through the companion paper for each earthquake records in the bins. The most influential parameter affecting permanent displacement is magnitude. The other parameters describing earthquake motion are not significant enough to increase permanent displacement of the inverted T-type wall except for energy related parameters(AI, CI, SEI).

• Earthquakes and Structures
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• v.26 no.3
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• pp.219-228
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• 2024

This study examines damping modification factors (DMFs) of elastic input energy spectra corresponding to a set of 116 earthquake ground motions. Mean input energy per mass spectra and mean DMFs are presented for both considered ground motion components. Damping ratios of 3%, 5%, 10%, 20%, and 30% are used and the 5% damping ratio is considered the benchmark for DMF computations. The geometric mean DMFs of the two horizontal components of each ground motion are computed and coefficients of variation are presented graphically. The results show that the input energy spectra-based DMFs exhibit a dependence on the damping ratio at very short periods and they tend to be nearly constant for larger periods. In addition, mean DMF variation is obtained graphically for also the damping ratio, and mathematical functions are fitted as a result of statistical analyses. A strong correlation between the computed DMFs and the ones from predicted equations is observed.

• Steel and Composite Structures
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• v.6 no.6
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• pp.479-491
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• 2006

Structures in seismic regions are designed to dissipate seismic energy input through inelastic deformations. Structural or component failure occurs when the hysteretic energy demand for a structure or component subject to an earthquake ground motion (EQGM) exceeds its hysteretic energy dissipation capacity. This paper presents a study on identifying the hysteretic energy demand and distribution throughout the height of regular steel moment resisting frames (SMRFs) subject to severe EQGMs. For this purpose, non-linear dynamic time history (NDTH) analyses were carried out on regular low-, medium-, and high-rise steel SMRFs. An ensemble of ninety EQGMs recorded on different soil types was used in the study. The results show that the hysteretic energy demand decreases from the bottom stories to the upper stories and for high-rise structures, most of the hysteretic energy is dissipated by the bottom stories. The decrease is quite significant, especially, for medium- and high-rise structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.399-408
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• 2000

IN analyzing earthquake response of structures important focus is on their diaplacements and shear forces. However seismic technology of passive energy dissipation makes focus on the seismic energy distribution of structures. The passive dampers enhance the capability of energy dissipation by their hysteretic behavior thus preventing the structural plastic deformation. In this paper the building structure with an active controller is analyzed with the view of earthquake energy distribution under elastic and plastic behaviors. The active control makes an effect of increasing damping capability which absorbs most of the earthquake input energy. Finally the different active gains resulting from the plastic deformation are applied to the active analysis and control forces and earthquake energy response are compared.