Damage Potential Of Ground Motions Research Articles

Impact of ground motion duration on seismic performance of buckling restrained braced frames

Buckling restrained braced frames (BRBFs) are commonly employed as seismic lateral force resisting system due to their high stiffness and energy dissipation capacity. However, under long-duration strong earthquakes, buckling-constrained braces are susceptible to fracture due to low-cycle fatigue. Previous studies evaluating their seismic performance have not considered the impact of earthquake duration on the results. This study evaluates the impact of ground motion duration on the seismic performance of BRBFs. By employing 44 pairs of spectrally equivalent ground motions with varying durations, the impact of ground motion duration is studied independently from other effects arising from ground motion amplitude and acceleration spectral shape. Nonlinear numerical models considering low-cycle fracture of buckling restrained braces are developed for 4-, 8-, and 12-story archetypes. The effects of ground motion duration on the seismic performance of BRBFs are examined using standard performance and collapse-assessment procedures. The results indicate that under seismic excitations not exceeding the maximum considered earthquake level, ground motion duration does not significantly affect the structural maximum interstory drift, but longer duration generally results in larger cumulative plastic deformation for the buckling restrained brace. Meanwhile, ground motion duration has a significant impact on the results of collapse risk evaluation. In addition, using combined duration- and spectrum-related intensity measure can better evaluate the damage potential of ground motion.

Characteristics of earthquake ground motions governing the damage potential for Delhi and the surrounding region of India

The proximity of Delhi and the surrounding region to the active faults along with its geographical settings is a subject of discussion to comprehend the seismic resilience of the capital region of India. The region may be affected by the far-field earthquakes from the Himalayas as well as the near-field earthquakes associated with the local seismic activity. Considering the ordinary settings of this region, the present study is an insight to differentiate the damage potential of ground motion associated with near and far-field conditions to further see their consequences to understand the comprehensive seismic hazard of the region. The acceleration and velocity response analysis of recorded strong ground motions from far-field and near-field earthquakes exhibit a clear distinct behavior in the form of amplification and corresponding predominant period. The comparison of estimated normalized spectral accelerations with that of the seismic design code of the Bureau of Indian Standards (BIS), shows that the current Indian building design code is within the structural limits proposed for the seismic forces of long periods, however, exceeded amplitude of the normalized Spectral Acceleration for far-field earthquakes may be attributed towards the damage potential for the high rise buildings in the capital region of India. On the other hand, near-field earthquakes do not meet the criteria with the design code of BIS at lower periods from 0.02s to 0.09s along with the amplified Spectral acceleration. It also suggests that the structural heterogeneities within the subsurface of Delhi and the surrounding region have a strong bearing in contributing to the impact of seismic waves from near-field earthquakes producing short-period waves that may be disastrous for low-rise buildings. Based on the results, the study region affected by the distinct seismicity patterns is important to understand the shaking behavior of the different kinds of infrastructures/buildings in case of near-field and far-field earthquakes to appropriately utilize the information for constructing new buildings and strengthening the existing infrastructures in Delhi and the surrounding region of India.

Determination of damage potential of seismic ground motion to underground structures at soft sites through experimental approach

The selection of a ground motion intensity measure (IM) is an essential criterion for judging the expected intensity level of ground motion in the vulnerability analysis of underground structures, and it is also part and parcel of the resilience-based seismic design of underground structures. Most of the current studies are based on a statistical analysis of numerical simulation results to obtain a specific IM measuring the damage potential of ground motions for an underground structure, and there is a lack of mechanistic studies based on experimental ways. In view of this, a series of large-scale shaking-table tests of an underground structure in soft soils were carried out in this paper to explore the appropriate IMs for measuring the damage potential of ground motions. It is found that the response characteristics of the tested soil-structure interaction (SSI) system gradually become similar to the long-period system as the ground motion intensity increases. The transient fundamental frequency of the tested SSI system moves from the acceleration-sensitive band to the velocity-sensitive band in the ground motion response spectrum. This leads to a decrease in the correlation between the response indicators (RIs) of the system and acceleration-based IMs and an increase in the correlation between RIs and velocity-based IMs as well as displacement-based IMs. Based on the test results, the site fundamental period (Tg) and the boundary periods between the sensitive bands in the bedrock response spectrum (Tc and Td) are proposed as identification indexes for selecting the appropriate IM. One of the three measures, PBA, PBV, and PBD, or a composite measure consisting of two of the three, can be adopted as an appropriate IM for an actual underground structure in soft soils in different cases.

Analysis of the Effects of Different Factors on Damage Potential Ranking

A quantitative evaluation of the damage potential of ground motions to structures can provide a basis for the selection of input ground motions. To determine the main factors influencing the damage potential ranking of ground motions, the corresponding effect factors were analyzed. First, the structural period range from 0.05 to 10 s was divided into three types of period ranges based on an improved Newmark–Hall spectrum. The intensity measures (IMs) that can characterize the damage potential in every period range were determined. Second, the effect of yield strength coefficient (Cy), vibration period (T), and type of site on the damage potential ranking are explained. A recommended damage potential ranking is given in the same period range. Finally, to demonstrate the rationality of the recommended damage potential ranking in this paper, two representative reinforced concrete (RC) shear structure models are established for analysis. For the same type of structures, the damage potential rankings under different Cy and T conditions have high correlation with the recommended damage potential ranking, and the discreteness is very low. When considering the site factors, the corresponding correlation and dispersion change little. Based on the analysis of two typical structural models, the R2 between the recommended damage potential ranking and structural response ranking were 0.89 and 0.94, respectively. It is proven that the methods of Cy, T, and the type of site are reasonable when establishing the recommended damage potential ranking in this paper. This study provides a theoretical basis for simplifying the evaluation of ground motion damage potential and for selecting input ground motions.

The Effect of the Yield Strength Coefficient and Natural Vibration Period on the Damage Potential Ranking of Ground Motions

To analyze the effect of structural parameters on the damage potential ranking of ground motions, the effect of the yield strength coefficient (Cy) and natural vibration period (T) on the damage potential ranking of ground motions is analyzed based on the bilinear model and the modified Clough model, which are the most commonly used hysteretic models in structural dynamic analysis. The displacement response (Sd) spectrum under nonlinear conditions is taken as the damage potential intensity measure (IM) of ground motions, and the effect of the Cy and T on the Sd mean spectrum is also analyzed for comparative analysis. The results show that: (1) in the short-period range, Cy has a great effect on the displacement response ranking. On the other hand, in the medium- and long-period ranges, Cy has little effect on the Sd ranking; (2) with the change of T in medium- and long-period ranges, the variation of Sd values is obvious when the change of T is small, but the variation of Sd ranking is very small. This conclusion can provide a theoretical basis for evaluating the damage potential of ground motions and selecting input ground motions.

Regression analysis on ground motion parameters for the earthquakes (Mw≥4.0) in NE India with special emphasis on 3 Jan 2016 M6.7, Tamenglong earthquake

In the present study, ground motion parameters (GMPs) are estimated by processing 26 earthquake events containing 125 accelerogram records with 375 components that originated in NE, India, and its vicinity with special emphasis on the Jan 3, 2016, M6.7, Tamenglong Earthquake. Moreover, Ground Motion Prediction Equations were developed through multiple regression analysis on observed data of 8 GMPs namely, Peak Ground Acceleration, Peak Ground Velocity, Arias Intensity, Characteristics Intensity, Housner Intensity, Cumulative Absolute Velocity, Effective Design Acceleration, and Acceleration Spectrum Intensity. The developed equations are representative of statistics on changes in amplitudes of parameters with varying distances and magnitude in connection to Northeast India. Besides, newly developed GMPEs can be applied to 4–6.8 magnitude earthquakes and valid up to 525 km of distance. In the case of January 3, 2016, Mw = 6.7, Tamenglong earthquake, a total of 25 parameters are estimated from ground motion recordings. The highest Peak Ground Acceleration (PGA) of 0.05 (g) has been experienced by Kohima station along with Pseudo Spectral Acceleration of 0.2802 (g) at the frequency of 1.72 Hz. The peak pseudo-spectral accelerations for each recording site of the Tamenglong earthquake are perceived within the periods of 0.2s and 0.5s. These estimations help in the characterization of ground motion with varying distances and magnitude which is a prime input to rate damage potential of ground motion and seismic hazard analysis in Northeast India.

Some observations on energy demand spectra for single-degree-of-freedom systems equipped with fluid viscous dampers

The ability of structural elements to absorb input energy through inelastic deformation and supplemental damping is a primary factor in determining structural damage during earthquake excitation. This study proposes an energy methodology for the seismic evaluation of single-degree-of-freedom (SDOF) systems, considering the effect of fluid viscous dampers (FVDs). The FVD is characterized by supplemental damping ratio, [Formula: see text], and velocity power [Formula: see text]. A computer algorithm is developed for the numerical simulation of SDOF systems using nonlinear time history analysis, which is verified through a number of validation examples. This study focuses on issues related to input and hysteretic energies [Formula: see text] with particular emphasis on near-field records and their interrelationship with seismic response demand, which is defined as non-dimensional indices for SDOF systems without FVD and those equipped with FVD. The energy indices ([Formula: see text] and [Formula: see text]) are the ratios of input and hysteretic energies to maximum displacement demand, respectively. The results show that the natural period [Formula: see text], ductility level [Formula: see text], [Formula: see text], and [Formula: see text] have a significant effect in the determination of energy spectra [Formula: see text]. The non-dimensional [Formula: see text] is a more stable and reliable indicator than [Formula: see text] to quantify the damage potential of ground motion. Finally, the observations of the energy approach provided in this study indicate that it can be used as a useful tool for developing energy-based guidelines for structures incorporating FVDs.

Correlation of Performance of Reinforced Concrete Buildings with Energy-Based Parameters

Background: The intensity of ground shaking and the demand on structures during earthquakes have been generally characterized using parameters such as peak ground acceleration as well as strength-based parameters such as response spectrum ordinates (e.g., spectral acceleration), which represent the maximum amplitude of shaking for structures with specified natural period and damping values. Methods: It has long been recognized that to assess the demands on structures during earthquakes, one might employ an energy-based approach (as an alternative to the more common strength-based one), especially when there is an interest in assessing the damage potential of ground motions. The study focuses on the correlation between Ground Motion Parameters (GMPs) and structural damage indicators for reinforced concrete frames. The relationship between ground motion intensity and structural damage is of primary concern in seismic regions. Here, we consider GMPs that are strength-based (such as spectral acceleration, Sa) and energy-based (such as input energy-equivalent acceleration, Ai, and absorbed energy-equivalent acceleration, Aa), as defined in the study. In order to evaluate Ground Motion Parameters (GMPs) for efficiency, power-law format regression studies of damage measures (DM) on each GMP are utilized. Results: The general objective of this paper is to investigate if energy-based parameters can correlate well with structural damage. Thus, power-law formats in regression of damage on GMP are considered. In regression studies of this type, a lower standard deviation of the damage measure given the value of the ground motion parameter (GMP) is considered an indication of a stronger correlation between that damage measure and the corresponding ground motion parameter. Conclusion: These extensive regression studies are carried out for both low-rise and high-rise reinforced concrete buildings. Conclusions are discussed following these analyses.

Rating damage potential of ground motion records

In this study, a total of 115,246 ground motions recorded during earthquakes of Moment magnitudes ranging from Mw 5.0 to Mw 9.0 are analyzed statistically. A total of 21 ground motion parameters characterising the recorded acceleration time histories are used in the analysis. Classification of these parameters through statistical correlation is reported and a parameter called “distance from zero-amplitude axis,” or dZ-A, is formulated in the principal component space. The ability for dZ-A to rate the damage potentials of strong motion records is evaluated through correlation of dZ-A with Japan Meteorological Agency (JMA) instrumental seismic intensities. This parameter can be used to rate damage potential of any strong motion record irrespective of the magnitude and location of the earthquake. It can also be used in selecting ground motion records of appropriate damage potential in seismic design and probabilistic analysis.

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.

Methodology for selection of the most damaging ground motions for nuclear power plant structures

A methodology for selecting the most unfavorable ground motions (MUGMs) for practical dynamic analyses of nuclear power plant (NPP) systems is proposed. A series of correlation analyses are carried out to select relevant intensity measures (IMs) that best characterize structural demand parameters and consequently the damage potential of ground motions on NPP structures. Predictive demand models are developed as a function of the selected IMs using a large suite of as-recorded ground motions. A damage index is defined and the MUGMs were identified according to the estimated damage values. The reliability of the methodology is verified by comparing the identified MUGMs with the “actual MUGMs” that resulted in the peak damage values among all dynamic simulations. As an alternative to traditional spectrum-based record selection methods, the proposed methodology will ensure a very low risk of failure of NPP structures under the design level earthquake and can be utilized in seismic margin assessment.

Ground Motion Parameters for the 2011 Great Japan Tohoku Earthquake

ABSTRACTThe 2011 great Japan Tohoku earthquake is not only the most devastating but also, one of the best recorded earthquakes in the history of seismology. A thorough study of strong motion characteristics of this earthquake is conducted using 20 well established ground motion parameters (GMPs). The behaviour of these parameters with fault distance and average shear wave velocity is examined and attenuation relationships are developed using the 1172 surface level strong motion records. In addition, all GMPs are categorized on a statistical basis using principal component analysis, which is further used to rate the damage potential of ground motion records.

Conditional Hazard Maps for Secondary Intensity Measures

Abstract Vector-valued ground-motion intensity measures (IMs) have been the focus of a significant deal of research recently. Proposed measures are mainly functions of spectral ordinates, which have been shown to be useful in the assessment of structural response. This is especially appropriate in the case of structures following modern earthquake-resistant design principles, in which structural damage is mainly caused by peak displacements experienced during nonlinear dynamics. On the other hand, there may be cases in which the cumulative damage potential of the earthquake is also of concern, even if it is generally believed that integral ground-motion IMs, associated with duration, are less important with respect to peak parameters of the record. For these IMs, it seems appropriate to develop conditional hazard maps, that is, maps of percentiles of a secondary IM (e.g., duration-related) given the occurrence or exceedance of a primary parameter (e.g., peak acceleration), for which a design hazard map is often already available. In this paper, this concept is illustrated, and conditional hazard is developed for a parameter, which may account for the cumulative damage potential of ground motion, the so-called Cosenza and Manfredi index ( I D ), given peak ground acceleration (PGA). To this aim, a ground-motion prediction relationship was derived for I D first. Subsequently, the residuals of PGA and I D were tested for correlation and for joint normality. Finally, the study obtained analytical distributions of I D conditional on PGA and on the corresponding design earthquake in terms of magnitude and distance from hazard disaggregation. As shown by the application to the Campania region (southern Italy), I D maps conditional on the code design values of PGA may be useful, for example, for a more refined ground-motion record selection as an input for nonlinear dynamic analysis of structures.

Effective Cyclic Energy as a Measure of Seismic Demand

Structural damage during strong ground shaking is associated with both the seismic input energy and the ability of structural components to dissipate energy through viscous damping and inelastic cyclic response. The correlation of the damage potential of ground motions with seismic energy demand is an important element in developing energy-based design methodologies. This article proposes a new measure of the severity of ground motions by introducing the concept of effective cyclic energy (ECE) defined as the peak-to-peak energy demand (sum of hysteretic and damping energies) imposed on a structure over an effective duration that is equivalent to the time between two zero-crossings of the “effective velocity pulse.” The proposed energy measure, which is dependent on the characteristics of the ground motion, is shown to be well correlated with peak seismic demand for a range of system parameters. The development of ECE also provides a basis for defining a non dimensional response index (γ eff ) to quantify the destructive potential of ground motions. The effectiveness of the new index parameter is validated using an extensive set of near-fault accelerograms and also compared to other ground motion severity indices. Finally, ECE demand of a MDOF system is estimated through modal-energy-decomposition of elastic and inelastic SDOF systems, and the concept of ECE spectrum is proposed to estimate the modal target energy demands for performance evaluation of structures.

A new approach of selecting real input ground motions for seismic design: The most unfavourable real seismic design ground motions

AbstractThis paper presents a new way of selecting real input ground motions for seismic design and analysis of structures based on a comprehensive method for estimating the damage potential of ground motions, which takes into consideration of various ground motion parameters and structural seismic damage criteria in terms of strength, deformation, hysteretic energy and dual damage of Park & Ang damage index. The proposed comprehensive method fully involves the effects of the intensity, frequency content and duration of ground motions and the dynamic characteristics of structures. Then, the concept of the most unfavourable real seismic design ground motion is introduced. Based on the concept, the most unfavourable real seismic design ground motions for rock, stiff soil, medium soil and soft soil site conditions are selected in terms of three typical period ranges of structures. The selected real strong motion records are suitable for seismic analysis of important structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake, as they can cause the greatest damage to structures and thereby result in the highest damage potential from an extended real ground motion database for a given site. In addition, this paper also presents the real input design ground motions with medium damage potential, which can be used for the seismic analysis of structures located at the area with low and moderate seismicity. The most unfavourable real seismic design ground motions are verified by analysing the seismic response of structures. It is concluded that the most unfavourable real seismic design ground motion approach can select the real ground motions that can result in the highest damage potential for a given structure and site condition, and the real ground motions can be mainly used for structures whose failure or collapse will be avoided at a higher level of confidence during the strong earthquake. Copyright © 2007 John Wiley & Sons, Ltd.

Evaluation of Damage Potential of Ground Motions during Great Earthquakes

In order to select appropriate input ground motions for earthquake-resistant design or estimation of seismic safety of structures, their characteristics should be identified. In this paper, damage potential is defined as a spectrum of strength demand required to maintain a damage index less than or equal to a tolerable damage index value. The damage index proposed by Park and Ang (1985) and a bilinear model are used to calculate the strength demand spectrum. The damage index describes the state of the concrete structure from slight damage to severe damage or collapse. Studies of the damage potential of ground motions during the recent great earthquakes, including the 1995 Hyogoken-Nanbu earthquake in Japan and the 1999 Chi-Chi earthquake in Taiwan, show that damage potential may be greatly affected by the location of the fault, the geological structure of the site, and the fault rupture mechanism. Furthermore, an estimation of damage potential of ground motions over a large area, Kawasaki City in Japan, is described.

Seismic Hazard Analysis of Nonlinear Structures. I: Methodology

Conventional seismic hazard analysis methodology is generalized to estimate directly the annual seismic risk of exceeding a specified level of postelastic damage in real structures. The procedure makes use of empirical statistics of the nonlinear‐response‐based factor FDM that is a measure of the damage potential of ground motions to multi‐degree‐of‐freedom structures. Using a two‐dimensional model of a jacket‐type offshore platform and a large sample of observed time histories, it is confirmed that (as for single DOF systems): (1) There is no significant dependence of the average of FDM on magnitude and distance; and (2) its coefficient of variation is relatively small. These two facts make the method practical. They were confirmed for both local (member‐level) damage measures and global collapse, for variations in structure and foundation modeling, and for various durations. A companion paper presents applications to two large three‐dimensional, multi‐degree‐of‐freedom, nonlinear models of actual structures.

Statistical correlation of observed ground motion with low-rise building damage

abstract A statistical study was conducted correlating ground motion with structure damage data from the RULISON underground nuclear explosion gas stimulation experiment. The statistical study first leads to the identification of the ground-motion characterization that best represents the damage potential of ground motion; then to the development of motion-damage relationships for low-rise buildings subjected to ground motion. The motion-damage relationships are derived both for overall damage as well as for the most frequently damaged building components. The overall motion-damage relationships are given in terms of incidence of complaints (complaint ratio), incidence of damage (damage ratio), and damage cost (damage cost factor).