Relative Input Energy Research Articles

GMPEs for elastic input energy spectra of horizontal and vertical offshore ground motions based on the ETMC database in Japan

In this study, the characteristics of offshore ground motions related to elastic relative and absolute input energy are investigated, and ground-motion prediction equations (GMPEs) for elastic input energy of offshore ground motions are proposed. The GMPEs are developed using mixed-effects models calibrated through regression analysis of elastic responses which are derived from dynamic analyses of single-degree-of-freedom (SDOF) systems subjected to offshore ground motions. To compare the differences between offshore and onshore ground motions with regard to input energy, an onshore GMPE is derived from the onshore database. The ground motion database includes 892 offshore records and 4033 onshore records; the offshore and onshore records are collected from the same set of 273 earthquakes. To quantitatively analyze the elastic input energy of offshore ground motions, the moment magnitude, tectonic source type, focal depth, hypocentral distance and site condition are considered in the proposed equations. A comparison and analysis of the relative and absolute input energy of offshore and onshore ground motions manifest that the horizontal input energy spectra of the entire period band and the vertical input energy spectra of moderate and long period band of offshore ground motions are larger than those of onshore motions of all site classes, except that the vertical input energy of offshore motions is slightly smaller than that of onshore motions for short periods due to the combined effects of water layer and soft sediments under seafloor. The differences between the relative and absolute input energy of offshore ground motions and comparisons of the proposed GMPEs with others from the literature are also discussed in this study. The comparisons show that the proposal of the GMPE for elastic input energy of the offshore ground motion is necessary due to the offshore ground motion being considerably different from the onshore motion and the proposed onshore GMPEs. • The prediction equations for elastic input energy of offshore ground motions are proposed, providing the seismic demand for the energy-based seismic design of offshore structures. • The site condition of offshore ground motions is significantly different from those of onshore motions. • The offshore ground motions are larger than those of onshore ones for long period due to the effect of thick soft sediments.

Ranking of ground motions destructive capacity for low- and middle-rise RC frame structures based on a comprehensive intensity measure

To quantitatively evaluate the destructive capacity of ground motions for Chinese seismic design, a method to rank the ground motion based on a new comprehensive intensity measure is proposed. A total of 5535 ground motions from NGA-West2 database were used as the input ground motions for dynamic time history analysis to four typical reinforced concrete structures. By performing correlation analysis on the ground motion intensity measures (IMs) and structural response parameters, two optimal IMs, including the peak ground velocity and the relative input energy, are first selected to represent the damage capacity of ground motion. Through regression analysis, a new comprehensive IM is proposed to quantitatively describe the destructive capacity of ground motions. Then based on the proposed comprehensive intensity measure, all ground motions are ranked from first to last. Finally, the comparison with other methods proves the feasibility of the proposed ranking method in quantitatively describing the destructive capacity of ground motions.

Evaluating of Relative and Absolute Cumulative Input Energy Time History subjected to Forward Directivity Earthquakes

Evaluating of Relative and Absolute Cumulative Input Energy Time History subjected to Forward Directivity Earthquakes

Evaluation of the relative and absolute cumulative input energy time history in the near-fault earthquake with visible pulse in acceleration time history, using the relative and absolute energy reflection spectral approach

Several studies have been carried out to evaluate the impact of near-fault earthquake with fling-step motion effects. The obvious feature of such earthquakes is the existence of a pulse with a significant amplitude in the velocity accelerograms. In this article, in order to investigate the effect of pulse-type near-fault earthquakes on the elastic demands of steel moment frames, a 15stories was simulated. After verifying the modelling process, under the influence of 20 near-field and 2 far-field records were analysed. The relationship between effective cyclic energy, ECE, and the displacement, velocity and hysteretic curve of SDOF systems in near- and far-fault earthquakes was evaluated. Then, studying the energy of relative and absolute cumulative input energy with kinetic energy in one section and maximum inter-story drift for 4 different levels of nonlinear behaviours (R = 1.0, 2.0, 4.0, 6.0) in the other section, the effect of higher modes was evaluated. Studying the inter-story drift profile for two near-fault earthquakes, with and without accelerated pulses, indicates the formation of the maximum drift, IDRmax, in upper stories for low nonlinear degrees (R=1.0 and R=2.0) in Records with visible pulses that verify the participation of higher modes. However, in accelerated pulse-free records, in addition to intensifying the IDRmax in the upper stories, a large-scale demand is imposed in the lower stories. In other words, in the lower stories, the first mode is mainly involved in these records.

Procedure for Ranking Ground Motion Records Based on the Destructive Capacity Parameter

The relative input energy of a ground motion is used to quantitatively estimate the destructive capacity of ground motion to a structure, which reflects the deformation capacity and energy dissipation capacity of a structure. The destructive capacity of a ground motion on a structure is known to be relevant to the structural period. Because ranking the destructive capacity of ground motion at all periods is not practical, rationally dividing period ranges should be performed before ranking ground motions according to their destructive capacity and a new method to divide period ranges based on the relative input energy is proposed. According to the correlation coefficient of the relative input energy at adjacent structural periods, the structural periods from 0.2 s to 10 s are divided into several representational period ranges, which include a recommended period within each period range to represent the whole range. Only the ground motion ranking sequence at the recommended period is used in this period range. The rationality of the ranking sequence of ground motions based on destructive capacity is verified by a series of structural seismic response analyses. The results of this paper are compared with those of existing methods, and the results show that the relative input energy index is able to better quantitatively describe the destructive capacity of ground motion.

Quantification of Energy-Related Parameters for Near-Fault Pulse-Like Seismic Ground Motions

An energy-based approach facilitates the explicit consideration of the damage associated with both maximum displacements and cumulative plastic deformations under earthquakes. For structural systems that can undergo pulse-like seismic ground motions close to causative faults, an energy-based approach is deemed especially appropriate with respect to well-established force- or displacement-based strategies. In such a case, in fact, most of the damage is attributable to the dominant pulse-like component, which usually occurs into the velocity time history of the seismic ground motion, thus implying high energy levels imparted to a structural system. In order to enable the implementation of an energy-based approach in the analysis and design of structures under near-fault pulse-like seismic ground motions, this study presents a comprehensive numerical investigation about the influence of seismological parameters and hysteretic behavior on the spectra of the following energy-related parameters: inelastic absolute and relative input energy; input energy reduction factor; hysteretic energy dissipation demand; hysteretic energy reduction factor; dimensionless cumulative plastic deformation ratio. Closed-form approximations are proposed for these spectra, and the numerical values of the corresponding parameters have been also calibrated (with reference to both mean and standard deviation values) as functions of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level. The outcomes of this study are meant to support the derivation of design spectra for the energy-based seismic design of structures under near-fault pulse-like seismic ground motions.

Spatial Cross-Correlation Models for Absolute and Relative Spectral Input Energy Parameters Based on Geostatistical Tools

ABSTRACTIn recent years, energy-based seismic design methodology has received increasing attention because it takes into account not only the force and displacement behavior of a structure but also the cumulative damage effect caused by seismic loading. Specifically, as a fundamental parameter, input energy parameters (both absolute and relative measures) are directly related to the cumulative damage potential; therefore, they are commonly used in energy-based seismic design and seismic risk assessment. This study thus proposes new spatial cross-correlation models for absolute and relative elastic input energy parameters, using 2219 ground-motion records selected from 12 earthquake events. The normalized within-event residuals for both absolute and relative measures are first calculated. Semivariogram analysis is then conducted to quantify the spatial correlation of residuals for the input energy parameters at multiple sites and multiple periods. The linear model of coregionalization (LMC) approach is adopted to fit the empirical data; it is observed that the proposed LMC-based function performs reasonably well in capturing the spatial variability of the input energy measures. The influence of regional site conditions on the spatial cross correlation of input energy parameters is also investigated, and generic models are proposed using the averaged standardized coregionalization matrices of 12 events. The spatial cross-correlation models developed for input energy parameters can be used in regional seismic risk assessment within an energy-based framework.

Ultrahigh “Relative Energy Density” and Mass Loading of Carbon Cloth Anodes for K-Ion Batteries

Mass loading and potential plateau are the two most important issues of potassium (K)-ion batteries (KIBs), but they have long been ignored in previous studies. Herein, we report a simple and scala...

Computing input energy response of MDOF systems to actual ground motions based on modal contributions

The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.

Ground-motion prediction equations for constant-strength and constant-ductility input energy spectra

In this study, new ground motion prediction equations are proposed for both constant-ductility and constant-strength absolute and relative input energy spectra. The proposed equations are developed using mixed-effects models calibrated through empirical regressions of inelastic responses derived from nonlinear dynamic analyses on single-degree-of-freedom systems subjected to a large number of strong ground motions. Parametric analyses are carried out to show the variation on the predicted inelastic spectra produced by the level of inelastic demand in terms of constant ductility factors and strength ratios, and by the type of hysteretic model adopted to describe the nonlinear behavior of the system. It is shown that the latter has a moderate influence only on constant-strength spectra at short periods. With the increase of the inelastic demand level, the input energy decreases at long periods while increases at short periods. In general, differences between elastic and inelastic constant-strength spectra are negligible except in the very short period range. The increase in the damping ratio reduces such differences. Comparisons between the present proposals and already existing predictive equations available in the literature are finally discussed.

The Spectra of Relative Input Energy per Unit Mass of Structure for Iranian Earthquakes

Energy criterion is a simple and scalar quantity, so it has been employed by many researchers for the assessment of seismic behavior. Production and presentation of input energy spectra are effective steps for the employment of energy criterion in the seismic design of structures. Ninety-two pairs of horizontal components of Iranian earthquakes were used for this research. These records were divided into near-field and far-field, and in each field, soils categorized to types 1–3. Using nonlinear dynamic analysis, 92 inelastic spectra of relative input energy per unit mass were generated for a damping ratio of 5% and a ductility factor of 3. Then, for each category of records, a combined spectrum was produced at design level corresponding to 10% risk in 50 years. The evaluation of combined spectra led to the conclusion that the average value of combined spectrum in near-field is greater than that in far-field. In addition, the average value of combined spectrum is greater for softer soils. The corresponding period to the peak of combined spectrum in near-field is longer than that in far-field. The effect of soil type in near-field is more than that in far-field. For each field and each type of soil, a relation and its parameters have been proposed for the inelastic spectrum of relative input energy per unit mass.

An Intensity Measure for Seismic Input Energy Demand of Multi-Degree-of-Freedom Systems

Nonlinear dynamic analyses are performed to compute the maximum relative input energy per unit mass for 21 multi-degree-of-freedom systems (MDOF) with preselected target fundamental periods of vibration ranging from 0.2 to 4.0 s and 6 target inter-story ductility demands of 1, 2, 3, 4, 6, 8 subjected to 40 the earthquake ground motions. The efficiency of the several intensity measures as an index for damage potential of ground motion in MDOF systems are examined parametrically. To this end, the dispersion of normalized input energy by different intensity measures have been evaluated and compared. Results of this study show that using all intensity measures will result in a significant discrepancy in input energy spectra of MDOF systems, which are in most cases larger than 0.5 and even can take the value of 1.9 for some cases. This signifies that the evaluated intensity measures may not suitable for MDOF systems. A dimensionless intensity measure as a normalized energy index is proposed for MDOF systems subjected to far-fault earthquakes. It was demonstrated that the proposed normalized input energy values have smaller dispersion compared to those of the other indices for MDOF systems with all ranges of period and ductility ratio used.

An improved input energy spectrum verified by the shake table tests

SummaryInput energy is the principal component of the energy balance equation. It is beneficial to determine, through its components, how the recoverable and irrecoverable energies are distributed within the structural elements. Several equations and attenuation relations to define mass‐normalized input energy spectra exist in the literature. They are mainly proposed for elastic systems subjected to far‐fault EQs. There is a lack of experimental verification of these proposed spectra. In this paper, experimental assessment was performed to the existing spectra, and further improvements were accomplished. For this purpose, steel cantilever columns were tested on the shake table for two specific historical EQs coincidently having similar spectral acceleration values. Based on the experimental results, a three‐part mass‐normalized relative input energy spectrum was formulated including soil type, EQ (corner period, intensity, duration, spectral acceleration, and velocity), and structural behavioral characteristics (period and structural damping). The proposed input energy spectrum was experimentally calibrated and numerically validated for various EQs featuring near‐ and far‐field types. Analytical and experimental comparisons were made between the previously developed spectrum and the newly proposed one. The validation studies and the statistical evaluations exposed that the proposed spectrum yielded better agreement with the experimental and numerical results.

Nitric Oxide Oxidation and Its Removal in Mist by Nonthermal Plasma: Effects of Discharge Conditions

A coaxial nonthermal plasma (NTP) reactor was used for the removal of nitric oxide in mist. The effects of discharge gap, thorn number, tooth slice number as well as discharge polarity on NO oxidation and NOx removal were investigated. Decreasing the discharge gap is favorable for the NO oxidation and NOx removal. The mist is almost captured completely even under a relative low input energy. Increasing the thorn number of discharge slice or tooth slice number facilitates the energy input in the plasma reactor and thus enhances the NO oxidation and NOx removal under a fixed applied voltage. The energy efficiency for the positive DC (4.5 g NO/kWh) is three times as much as that for the negative DC (1.5 g NO/kWh), corresponding to NO oxidation efficiency of around 80%.

Energy-based design base shear for RC frames considering global failure mechanism and reduced hysteretic behavior

A nonlinear static procedure considering work-energy principle and global failure mechanism to estimate base shears of reinforced concrete (RC) frame-type structures is presented. The relative energy equation comprising of elastic vibrational energy, plastic strain energy and seismic input energy is obtained. The input energy is modified with a factor depending on damping ratio and ductility, and the energy that contributes to damage is obtained. The plastic energy is decreased with a factor to consider the reduced hysteretic behavior of RC members. Given the pre-selected failure mechanism, the modified energy balance equality is written using various approximations for modification factors of input energy and plastic energy in scientific literature. External work done by the design lateral forces distributed to story levels in accordance with Turkish Seismic Design Code is calculated considering the target plastic drift. Equating the plastic energy obtained from energy balance to external work done by the equivalent inertia forces considering, a total of 16 energy-based base shears for each frame are derived considering different combinations of modification factors. Ductility related parameters of modification factors are determined from pushover analysis. Relative input energy of multi degree of freedom (MDOF) system is approximated by using the modal-energy-decomposition approach. Energy-based design base shears are compared with those obtained from nonlinear time history (NLTH) analysis using recorded accelerograms. It is found that some of the energy-based base shears are in reasonable agreement with the mean base shear obtained from NLTH analysis.

An AutomaticP‐Phase Arrival‐Time Picker

Presented is a new approach for picking P ‐phase arrival time in single‐component acceleration or broadband velocity records without requiring detection interval or threshold settings. The algorithm P PHASE P ICKER transforms the signal into a response domain of a single‐degree‐of‐freedom (SDOF) oscillator with viscous damping and then tracks the rate of change of dissipated damping energy to pick P ‐wave phases. The SDOF oscillator has a short natural period and a correspondingly high resonant frequency, which is higher than most frequencies in a seismic wave. It also has a high damping ratio (60% of critical). At this damping level, the frequency response approaches the Butterworth maximally flat magnitude filter, and phase angles are preserved. The relative input energy imparted to the oscillator by the input signal is converted to elastic strain energy and then dissipated by the damping element as damping energy. The damping energy yields a smooth envelope over time; it is zero in the beginning of the signal, zero or near zero before the P ‐phase arrival, and builds up rapidly with the P wave. Because the damping energy function changes considerably at the onset of the P wave, it is used as a metric to track and pick the P ‐phase arrival time. The P PHASE P ICKER detects P ‐phase onset using the histogram method. Its performance is compared with picking techniques using short‐term‐average to long‐term‐average ratio, and a picking method that finds the first P ‐phase arrival time using the Akaike information criterion. A large set of records with various intensities and signal‐to‐noise ratios is used for testing the P PHASE P ICKER , and it is demonstrated that P PHASE P ICKER is able to more accurately pick the onset of genuine signals against the background noise and to correctly distinguish between whether the first arrival is a P wave (emergent or impulsive) or whether the signal is from a faulty sensor. Online Material: MATLAB script for P ‐phase arrival time picking.

Correlation of elastic input energy equivalent velocity spectral values

Recently, two energy-based response parameters, i.e., the absolute and the relative elastic input energy equivalent velocity, have been receiving a lot of research attention. Several studies, in fact, have demonstrated the potential of these intensity measures in the prediction of the seismic structural response. Although some ground motion prediction equations have been developed for these parameters, they only provide marginal distributions without information about the joint occurrence of the spectral values at different periods. In order to build new prediction models for the two equivalent velocities, a large set of ground motion records is used to calculate the correlation coefficients between the response spectral values corresponding to different periods and components of the ground motion. Then, functional forms adopted in models from the literature are calibrated to fit the obtained data. A new functional form is proposed to improve the predictions of the considered models from the literature. The components of the ground motion considered in this study are the two horizontal ones only. Potential uses of the proposed equations in addition to the prediction of the correlation coefficients of the equivalent velocity spectral values are shown, such as the prediction of derived intensity measures and the development of conditional mean spectra.

Wavelet analysis for the characterization of forward-directivity pulse-like ground motions on energy basis

The characterization of the prominent features of near-fault pulse-like ground motions is under scrutiny. Relationships between pulse characteristics and the performance of structures are here established. Two wavelet energy-based signal processing procedures are introduced. The aim is the construction of simplified signals containing the prominent features of the data distribution recorded from pulse-like earthquakes; signals that can be efficiently used in the design of civil engineering structures, increasing the safety and reliability of the structural design itself. The first procedure is based on the analysis of the absolute input energy. The second one considers the relative input energy. Comparisons with other wavelet-based earthquake analyses are developed.

Study on comparison between absolute and relative input energy spectra and effects of ductility factor

Based on 266 strong ground motion records, an attenuation relationship was developed for both absolute and relative input energy spectra. The comparison of the two kinds of input energy spectra constructed from the attenuation relationship was made in this paper. The results show that there is little difference between the absolute input energy spectra and relative input energy spectra at the periods of 0.5–1.0 s for elastic systems and at the period of 0.5 s for inelastic systems. The absolute input energy spectra are much larger than relative input energy spectra in very short period range but some less than relative input energy spectra in long period range. It is also found that the ductility factor has a significant effect on both absolute and relative input energy spectra. The absolute input energy spectra increase with the increasing of ductility factor in the period range of less than 0.3 s but decrease in the period range of larger than 0.3 s. The absolute input energy spectra for different ductility factor are almost equivalent at the period about 0.3 s, but for relative input energy spectra, the period is about 0.5 s. The effect of ductility on the relative input energy spectra in the short period range is much larger than that on the absolute input energy spectra, especially on the softer site class.

A measure of earthquake motion capacity to damage medium-period structures

The expression I=vgtD0.25 is proposed as an instrumental measure of earthquake ground motion capacity to damage structures with fundamental periods in the medium-period (velocity-controlled) region. Only two of the basic ground motion parameters which can be routinely predicted in the design procedure (peak ground velocity and the duration of strong shaking) are included in the formula. Expressions for determining the bounds of the medium-period region are also proposed as a function of the basic ground motion parameters. A total of 40 records having very different characteristics, including extremely short and long duration, were used in the statistical study. The new intensity parameter has been evaluated by using inelastic and elastic relative displacement and input energy spectra.