Elastic Acceleration Response Spectra Research Articles

Are the Italian microzonation level 2 abacuses applicable in the Friuli Venezia Giulia (Italy) plain? Comparison between the national abacuses and the numerically simulated amplification factors and between the derived elastic response spectra

Seismic shaking of an area is strongly affected by the local geology. The so-called local site effects must be considered for the estimation of seismic effects on structures and urban planning. Thus, the seismic microzonation is the process aimed at identifying and mapping the subsoil local response in a given area, usually at urban/municipality scale and in terms of ground shaking parameters and susceptibility to ground instabilities. In Italy, for areas that can be schematised as a 1D subsoil model (e.g. alluvial plain), a simplified approach is proposed to quantify the seismic amplification (amplification factor, AF). This approach consists of tables of correspondences, called seismic abacuses, available for the whole national area as well as for some regional territories, and derived for simplified subsoil models. In this work, the results of the comparison between the AF values retrieved from national abacuses applied in the Friuli Venezia Giulia (Italy) plain municipalities and those from 1D numerical simulations are presented. In general, the abacuses underestimate the local seismic site effects a part for sites with a shallow bedrock. No correlations/trends were identified between the AF derived from abacuses and those from numerical simulations. Moreover, considering the elastic acceleration response spectra, it emerges that in the 49.5% of the FVG analysed sites the abacuses approach, even though it underestimates the real seismic response, is a more suitable approximation compared to the soil class simplified approach proposed by the Italian regulation. Finally, what emerges is that the limit of 30 m, as indicated in the Italian regulation, to consider a deep or shallow bedrock seams underestimated, and the AFs are not correlated with the seismic bedrock depth when it is higher than 100 m.

Vertical Elastic Acceleration Response Spectra for Vrancea Intermediate-Depth Earthquakes

This study is focused on the evaluation of vertical elastic acceleration response spectra for Vrancea intermediate-depth earthquakes in Romania in the context of the ongoing update of the national seismic design code. The ground motion database employed in this research consists of about 500 ground motions recorded during moderate and large Vrancea intermediate-depth earthquakes with moment magnitudes MW ≥ 5.2. The analysis of the dataset showed that a single ground motion recording had a peak ground acceleration larger than 0.20 g. The results of the analyses showed that no significant differences between the control periods of the vertical elastic response spectra as a function of the site class could be inferred. It was also observed that the mean value of the amplification factor computed for the entire ground motion database was about 2.5, irrespective of the earthquake magnitude, site class, or level of horizontal peak ground acceleration. However, larger-magnitude earthquakes generate larger spectral amplifications in the medium- and long-period ranges. The analysis of the ground motions recorded in Bucharest area revealed a magnitude dependency of the control period for the vertical ground motion TC,v. Finally, a single spectral shape for vertical acceleration response spectra characterized by a maximum dynamic amplification factor of 2.5 and control periods TBv and TCv of 0.05 s and 0.60 s is proposed for design purposes. This aspect allows for a major update from the current version of the national seismic design code which proposes control periods of the elastic vertical response spectrum dependent on the horizontal ones. The short-period (at T = 0.2 s) and long-period (at T = 1.0 s) ratios of the vertical acceleration response spectrum to the corresponding horizontal ones are 0.50 and 0.40.

An ameliorative duration of pulse-like ground motion records for nonlinear structural analysis

The near-field pulse-like ground motion contains obvious long-period and large pulse characteristic, which makes the nonlinear response of the structure exceed the general prediction of seismic response results. In order to reserve the obvious pulse component while selecting the strong ground motion duration part of the near-field pulse-like ground motion record without causing a large loss of spectral characteristics, the paper proposes an ameliorative truncated strong ground motion duration—useful duration. It is proposed based on the elastic acceleration response spectrum. Its principle is to make the acceleration response spectrum corresponding to useful duration and that corresponding to the original ground motion record as close and consistent as possible. The research results show that from the perspective of elastic response spectrum matching, the response spectrum matching error corresponding to useful duration is smaller than that of significant duration. In addition, the five types of periods corresponding to useful duration are closer to the period of original ground motion. Ulteriorly, from the displacement ratio spectrum of the elasto-plastic single-degree-of-freedom system, it is found that the average value of the elasto-plastic displacement ratio spectrum of useful duration and the original ground motion record is 0.98, which is very close to 1.00. It shows that the truncated ground motion can be used to replace the original ground motion to fully predict the nonlinear response of typical structures. Additionally, the effectiveness is further verified in the nonlinear response of three reinforced concrete frame structures, and the nonlinear response results of the structures are calculated using the time-history of useful duration, with less discreteness.

Ground motion of the Ms7.0 Jiuzhaigou earthquake

Abstract Eighty-eight free-field strong ground motion observation datasets obtained by the National Strong Motion Observation Network System of China for the Jiuzhaigou Ms7.0 earthquake were used to study the characteristics of the strong ground motion and the site response. In this study, we calculated the VS30 of the near field station and compared the observed values of the horizontal peak acceleration and peak velocity with the CB2014 ground motion prediction models developed by Campbell et al. (2014). The results indicate that the observed values of the horizontal peak acceleration and peak velocity of the Jiuzhaigou earthquake are both smaller than the predicted values obtained from the ground motion prediction equations. By regressing the spatial variation curves of the D SR (5–95%) and D SR (5–75%) ground motion durations, and comparing them with Bommer’s (2009) ground motion duration prediction curve, it was found that the duration of the Jiuzhaigou earthquake was greater than that obtained from the global empirical prediction equation. The scope of the source duration corresponding to the D SR (5–75%) duration is 2.76–4.28 s, and the scope of the source duration corresponding to the D SR (5–95%) duration is 8.88–10.36 s, which are close to the peak time and completion time of the seismic moment release during the source rupture process. The linear elastic acceleration response spectra of 11 stations within 100 km of the fault were calculated for comparison with the design spectrum. It was concluded that the range of the predominant period of the response spectrum was 0.05–0.26 s, which is less than the natural vibration period of the local multistory building. However, the response spectrum value recorded by station 51JZZ is greater than the design spectrum of the 8° rare earthquake and the observation values of the nearby strong ground motion stations. Through analysis of the H/V spectrum ratio and the case of station 51JZZ, which is closest to the epicenter, this phenomenon was concluded to be related to the magnification effect of the near-surface soil layer and the nonlinear response of the site under the action of strong earthquakes.

Seismic design of RC frame structures based on energy-balance method

The force- and displacement-based design methodologies have been widely used in current seismic design practice. In both methodologies, inelastic behavior is determined indirectly since the seismic demands are derived from elastic acceleration response spectra. In this study, a novel energy-based design (EBD) approach is proposed in the determination of both seismic demand and dissipation capacities of reinforced concrete (RC) frame members through their inelastic behavior directly. In the case of frame-type RC structures, the distribution of demand plastic energy throughout the structure is achieved. The proposed EBD is then accomplished by comparing the demand plastic energy with the energy dissipation capacity of members while integrating performance-based design guidelines. A cantilever column and a benchmark frame, both from the literature, are analyzed in verification of the proposed methodology. Comparisons are made between force, displacement and EBD methodologies in terms of soil condition, member, system and ductility performance requirements. Member and global performance targets are found to be comparable in displacement and EBD methodologies. However, owing to lack of ductility considerations in the prior design methodologies, the proposed EBD showed more reliable result in the determination of both cross-sectional geometry and its rebar configuration. The proposed methodology provides better understanding of damage state limits of RC members by incorporating the plastic energy spectrum, which includes cyclic action, duration, and frequency content of ground motions, as well as inherent ductility in both demand and capacity determinations. The sensitivity analyses between code compliant-design and soft-story-mechanism buildings showed a distinct difference in the variations of seismic energy among the members and their corresponding damage distributions. EBD methodology provides better in depth understanding of the seismic design in terms of demand and capacity of member and overall structural system, and their corresponding performance.

An Investigation on the Effect of the Near-Fault Earthquakes on the Seismic Behavior of RC Moment Resisting Frames (MRFs) Designed Based on Iranian Seismic Code (Standard No. 2800)

Past severe earthquakes, such as Bam earthquake of 2003 and Tabas earthquake of 1978, have demonstrated that many cities in Iran are prone to be struck by near-fault earthquakes. Such earthquakes are impulsive in nature, and therefore, they are more destructive than the ordinary ground shaking. In the fourth edition of Iranian seismic code (Standard No. 2800), some changes, including a modification factor for the elastic acceleration response spectrum (EARS) have been recently recommended to reflect the effects of such probable near-fault earthquakes for the designing procedure. In this study, a numbers of 2D RC moment resisting frames (MRFs), from four to twelve story buildings, are designed linearly based on Iranian National Building Code (INBC) and Standard No. 2800 as well. Subsequently, their nonlinear models are reproduced for conducting nonlinear dynamic time history (NDTH) analysis. For this purpose, twenty impulsive ground motions are selected and scaled to be compatible with the design basis earthquake (DBE) spectrum of the abovementioned code. It is concluded that the seismic performance of the analyzed structures are not satisfactory at all; no buildings are successful to satisfy the life safety (LS) performance level posed by guidelines such as ASCE41-06 or ASCE41-13. Moreover, it is worth mentioning that even collapse prevention (CP) limit states are not also met in some cases. Therefore, the recently added modifications in the Standard No. 2800 may be inadequate to incorporate the near-fault earthquakes' effects.

Post-earthquake warning for Vrancea seismic source based on code spectral acceleration exceedance

Post-earthquake crisis management is a key capability for a country to be able to recover after a major seismic event. Instrumental seismic data transmitted and processed in a very short time can contribute to better management of the emergency and can give insights on the earthquake`s impact on a specific area. Romania is a country with a high seismic hazard, mostly due to the Vrancea intermediate-depth earthquakes. The elastic acceleration response spectrum of a seismic motion provides important information on the level of maximum acceleration the buildings were subjected to. Based on new data analysis and knowledge advancements, the acceleration elastic response spectrum for horizontal ground components recommended by the Romanian seismic codes has been evolving over the last six decades. This study aims to propose a framework for post-earthquake warning based on code spectrum exceedances. A comprehensive background analysis was undertaken using strong motion data from previous earthquakes corroborated with observational damage, to prove the method`s applicability. Moreover, a case-study for two densely populated Romanian cities (Focsani and Bucharest) is presented, using data from a 5.5 MW earthquake (October 28, 2018) and considering the evolution of the three generations of code-based spectral levels for the two cities. Data recorded in free-field and in buildings were analyzed and has confirmed that no structural damage occurred within the two cities. For future strong seismic events, this tool can provide useful information on the effect of the earthquake on structures in the most exposed areas.

Major Parameters Affect the Non-Liner Response of Structure Under Near-Fault Earthquakes

Near-fault ground motion can be identified by the presence of a predominant long duration pulse in the velocity traces mainly due to directivity effect. This pulse exposes the structure to high input energy at the beginning of the earthquake which leads to a higher response in comparison with the ordinary ground motions. This paper investigates 79 earthquake records with different properties to achieve three goals: the first aim is to compare between the linear and nonlinear response of SDOF systems under near-fault and far-fault earthquakes. While the second objective is to examine the parameters that control the characteristics of near-fault earthquakes. Two factors have been studied which is PGV/PGA ratio and pulse period. Finally, the seismic code provisions related to the near-fault earthquakes were evaluated in term of the elastic acceleration response spectrum, the evaluation is adopted for American Society of Civil Engineers code ASCE 7 and Uniform Building Code UBC. The results lead to the following conclusions: with respect to a specific PGA, the near-fault earthquake imposed higher response in comparison with far-field earthquakes. The near-fault earthquakes become severe as the PGV/PGA and pulse period increase. The interested seismic codes can cover the actual behavior based on the average response of a certain amount of data, while it may become non-conservative relative to an individual record.

Automated classification of near‐fault acceleration pulses using wavelet packets

AbstractThis study proposes a new algorithm for automatically classifying two types of velocity‐pulses that are integral of a distinct acceleration pulse (acc‐pulse) or a succession of high‐frequency one‐sided acceleration spikes (non‐acc‐pulse). For achieving this, wavelet packet transform is used to filter the high‐frequency content and to extract the coherent velocity‐pulse. Then, the pulse period is unequivocally derived through the peak point method. Following the determination of the pulse‐starting (ts) and pulse‐ending (te) time instants in the velocity time‐history, a local acceleration time‐history truncated by ts and te is obtained. The maximum relative energy of the pulse between two adjacent zero crossings is then employed as indicator for distinguishing the two types of velocity‐pulses. The criteria for identifying acc‐pulses and non‐acc‐pulses are calibrated using a training data set of manually classified ground motions from the Next Generation Attenuation West 2 project. Finally, significance of such a classification between velocity‐pulses of different characteristics is assessed through the comparison of elastic acceleration response spectra of the two categories of pulse‐like records.

Modal behavior factors for the performance-based seismic design of R/C wall-frame dual systems and infilled-MRFs

Modal behavior (strength reduction) factors q̅k for the performance-based seismic design of plane reinforced concrete wall-frame dual systems and infilled moment resisting frames are proposed. Instead of using a single and constant behavior (strength reduction) factor q (R) as all modern seismic design codes do, herein are proposed different such factors for the first few significant modes of the structure. Moreover, these q̅k are constructed as functions of period, different deformation targets and soil types and thus, they are suitable for a performance-based design in a force-based design scheme. A linear analysis in conjunction with an elastic acceleration response spectrum with its ordinates divided by q̅k provides a design base shear which is able to produce seismically designed frames which account for both strength and deformation requirements. In contrast to the code-based seismic design procedure which is accomplished in two steps, i.e., first for strength and second for deformation satisfaction, the proposed method eliminates the second step due to its deformational dependent q̅k. Moreover, these q̅k can be used to design for up to four performance levels depending on the design needs. Explicit expressions for q̅k are derived from extensive parametrical studies involving non-linear tiime-history analyses of 19 wall-frame dual systems and 19 infilled moment resisting frames under 100 far-fault historical ground motions corresponding to the four soil classes of Eurocode 8, for six deformation targets and four performance levels. The proposed method is demonstrated and validated with realistic design examples, which show its advantages over the force-based design method of Eurocode 8.

Hazard-dependent soil factors for site-specific elastic acceleration response spectra of Italian and European seismic building codes

To define the seismic input in non-liquefiable soils, current seismic standards give the possibility to treat local site effects using a simplified approach. This method is generally based on the introduction of an appropriate number of soil categories with associated soil factors that allow modifying the shape of the elastic acceleration response spectrum computed at rocky (i.e. stiff) sites. Although this approach is highly debated among researchers, it is extensively used in practice due to its easiness. As a matter of fact, for standard projects, this method represents the driving approach for the definition of the seismic input. Nevertheless, recent empirical and numerical studies have risen doubts about the reliability and safety of the simplified approach in view of the tendency of the current soil factors of Italian and European building codes to underestimate the acceleration at the free surface of the soil deposit. On the other hand, for certain soil classes, the current soil factors seem to overestimate ground amplification. Furthermore, the occurrence of soil nonlinearity, whose magnitude is linked to both soil type and level of seismic intensity, highlights the fallacy of using constant soil factors for sites with a different seismic hazard. The objective of this article is to propose a methodology for the definition of hazard-dependent soil factors and simultaneously quantify the reliability of the coefficients specified in the current versions of Eurocode 8 (CEN 2005) and Italian Building Code (NTC8 2008 and revision NTC18 2018). One of the most important outcome of this study is the quantification of the relevance of soil nonlinearity through the definition of empirical relationships between soil factors and peak ground acceleration at outcropping rock sites with flat topological surface (reference condition).

Incorporating the local faults effects in development of seismic ground-motion hazard mapping for the Peninsular Malaysia region

The probabilistic seismic ground-motion hazard maps for the Peninsular Malaysia region have been developed by the present study. Despite the earlier seismic hazard maps for this region, which were proposed only based on far-field Sumatran seismic sources, this study has attempted to present the new maps using the combination of the local faults within the region, Sumatran fault, and Sumatran subduction source zones. The composite earthquake catalogue of the study region has been extended to cover an area limited by 10°S–10°N Latitude and 90°–110°E Longitude with the period from 1900 to 2014. The seismic source zones were categorized into subduction and fault sources. Line, area, and background source models were used to model the seismic sources with variable characteristics along them. In order to consider the epistemic uncertainty, logic-tree framework was used to incorporate basic quantities such as different source modelling, maximum magnitudes, and ground-motion prediction equations (GMPEs). The hazard maps are presented over a 12.5 km grid in terms of peak ground acceleration (PGA) for 10 and 2% probabilities of exceedance in 50 years corresponding to 475 and 2475 years return periods (RP), respectively. The proposed new hazard maps give the expected ground motions based on the extended earthquake catalogue, upgraded seismic source parameters, and more compatible GMPEs than applied in the development of previous hazard maps. The estimated PGAs on rock site condition across the Peninsular Malaysia region for RP475 and 2475 years are in the range of 1.0–10.0%g and 2.0–20.0%g, respectively. The horizontal elastic acceleration response spectra on different soil site conditions have been also presented for the region of interest following the principles of Eurocode 8 through the calculated uniform hazard spectra.

A Probabilistic Methodology to Determine Elastic Acceleration Response Spectra for Pulse-Type Records through Multi-Resolution Analyses

This article focuses on the characterizations of pulse-type ground motions which are mainly caused by rupture directivity. Multi-resolution analysis is employed to decompose 53 typical pulse-type records which are selected from 12 large earthquakes into a series of ground motion components. A methodology for deriving design spectra, which could incorporate the special effects caused by pulse-type records is proposed based on the bi-normalized response spectra of ground motion components, and is named as Near-Fault Response Spectrum (NFRS). Analysis results indicate that NFRS might be a reliable candidate for the code-based design spectrum especially for structures constructed close to active fault.

Expected ground motion at the historical site of Poggio Picenze, Central Italy, with reference to current Italian building code

The amplification of the ground motion at the surface is greatly influenced by the geotechnical characteristics of the soil formations below the ground surface. Traditionally, analyses of the ground response are deterministic, which means no consideration of the aleatory nature of geotechnical parameters of soil layers like density, shear wave velocity, etc. A fully stochastic procedure for estimating the site amplification of ground motion allows taking into account the record-to-record variability in an input ground motion and the uncertainty in dynamic soil properties and in the definition of the soil model. In particular, their effect on response spectra at the ground surface can be evaluated. With this procedure, it is pretended to reduce the aleatory variability into the soil model.In this work, the soil profile below the San Felice Martire church, at Poggio Picenze (L'Aquila area, Abruzzo, Central Italy), has been studied basically on field geologic observations and drilling and geophysical tests retrieved from previous investigation campaigns. The dynamic soil properties were obtained by literature and by the test results. Amplification effects at the site under investigation have been estimated using fully 1D stochastic site response analyses and for the object motion 7 real records compatible to the Italian code-based spectrum referred to 475-year return period. The Italian building code defines the reference seismic action in terms of elastic acceleration response spectra derived from the results of a probabilistic seismic hazard study.The results in terms of accelerograms and acceleration response spectrum (with the associated dispersion) indicated a clear amplification of the input motion at the basement of San Felice Martire church due to the lithostratigraphic characteristics of the soil deposits at the site under investigation.

Erratum to: New code site classification, amplification factors and normalized response spectra based on a worldwide ground-motion database

A global dataset of more than 3,000 ground motion records from 536 sites from Greece, Italy, Turkey, USA and Japan is compiled and used to propose code-oriented elastic acceleration response spectra and soil amplification factors for a new site classification system, which, besides the classical geotechnical parameters $$N_{SPT}, S_{u}$$ and PI, uses also the fundamental period of the site, the thickness of soil deposits and the average shear wave velocity to the seismic bedrock, instead of $$V_{s,30}$$ . We propose a new classification system with the associated amplification factors and normalized response spectra for two seismicity levels, i.e. $$M_{s}\le 5.5$$ and $$M_{s}>5.5$$ . Uncertainties in the estimation of soil amplification factors are captured using a logic-tree approach, which allows the efficient use of alternative models and methods. The aim of this work is to improve the present EC8 soil classification. The effectiveness of the proposed classification system is compared to that of EC8 classification system using an error term, which represents the average dispersion of data within all categories of a given classification scheme. Error terms for the new classification system are lower than the error terms for EC8 classification system at all periods.

Significance of ground motion time step in one dimensional site response analysis

The discrete nature of the numerical methods utilized in 1D site response analysis and calculation of the response spectra (e.g., frequency domain, Duhamel integral, and Newmark β methods) introduces time-step dependence in the resulting solution. Using an input ground motion with too large of a time-step leads to under-prediction of high-frequency characteristics of the system response due to limitations in the numerical solution of single and multiple degree of freedom systems. In order to reduce potential errors, using a sampling rate at least ten times greater than the maximum considered frequency is recommended. The preferred alternative is selection of input ground motions with a sufficiently small time step to avoid introducing numerical errors. However, where such motions are not available, then the time step of the ground motion can be reduced through interpolation. This paper demonstrates that the use of Fourier transform zero-padded interpolation is the preferred approach to obtain a ground motion with an adequate time step for the calculation of the elastic acceleration response spectra, and to analyze site response using either frequency or time domain methods.

Strong Ground Motions and Damage Conditions Associated with Seismic Stations in the February 2011 Christchurch, New Zealand, Earthquake

The February 2011 Christchurch, New Zealand, earthquake was highly destructive, causing a number of buildings to collapse and killing many people. We examined the properties of strong ground motions in this earthquake using the records released by GeoNet (http://www.geonet.org.nz/). We also investigated the damage around the seismic stations to determine the relationship between structural damage and strong ground motions. The locations of the seismic stations in our study are shown in Figure 1. Accelerograms and the elastic acceleration response spectra, with a damping factor of 0.05 in the maximum horizontal direction, are shown in Figures 2 and 3, respectively. Peak ground accelerations (PGA) and peak ground velocities (PGV) are shown in Table 1. Ij and I 1–2 are also shown in Table 1. Ij is JMA (Japan Meteorological Agency) seismic intensity (Tables 2, 3 and 4). It is publicly used to describe the damaging power of seismic shaking in Japan. I 1–2 is also an index like Ij . It was defined by Sakai, Kanno, and Koketsu (2002, 2004) based on elastic responses between 1 and 2 seconds period that were closely related with heavy structural damage (the subscript 1–2 means between 1 and 2 seconds) and represents the damaging power of an earthquake much better than Ij . View this table: TABLE 1 Seismic Intensity of Strong Ground Motions and Damage Conditions around the Seismic Station. View this table: TABLE 2 Explanation of JMA seismic intensity scales (http://www.jma.go.jp/) for human perception and reaction; indoor situations and outdoor situations View this table: TABLE 3 Explanation of JMA seismic intensity scales (http://www.jma.go.jp/) for wooden houses View this table: TABLE 4 Explanation of JMA seismic intensity scales (http://www.jma.go.jp/) for reinforced-concrete buildings As shown in Figures 2 and 3, the records of stations REHS, CCCC, …

Seismic response of R/C structures subjected to simulated ground motions compatible with design spectrum

SUMMARYIn seismic response analysis of building structures, the input ground motions have considerable effect on the nonlinear seismic response characteristics of structures. The characteristics of soil and the locality of the site where those ground motions were recorded affect the contents of ground motion time histories. This study describes a generation of synthetic ground motion time histories compatible with seismic design spectrum, and also evaluates the seismic response results of multi‐story reinforced concrete structures by the simulated ground motions. The simulated ground motion time histories have identical phase angles to the recorded ground motions, and their overall response spectra are compatible with seismic design spectrum with 5% critical viscous damping. The input ground motions applied to this study have identical elastic acceleration response spectra, but have different phase angles. The purpose of this study was to investigate their validity as input ground motion for nonlinear seismic response analysis of building structures. As expected, the response quantities by simulated ground motions presented better stability than those by real recorded ground motions. It was concluded that the simulated earthquake waves generated in this paper are applicable as input ground motions for a seismic response analysis of building structures. Copyright © 2010 John Wiley & Sons, Ltd.

설계용 스펙트럼에 적합한 인공지진동을 입력한 철근콘크리트 구조물의 지진응답 특성의 고찰

건축물의 지진응답해석에서 입력지진동은 구조물의 비선형 응답에 중요한 영향을 미치는 요소이다. 지진동의 특성은 표층지반의 성질과 국부적인 지반 조건에 따른 여러 가지 인자에 의해 그 특성이 결정되기 때문에 구조물의 지진응답해석에서 일반성을 갖는 입력지진동을 선정하는 것은 매우 어려운 문제이다. 본 논문은 내진설계용 스펙트럼에 적합한 인공지진동파형을 작성한 후, 작성된 인공지진동에 의한 철근콘크리트 다층 골조구조물의 탄소성 응답특성을 분석한 것이다. 여기서 작성된 인공지진동파형은 과거 비교적 큰 규모의 지진에서 얻어진 기록지진동과 동일한 위상각을 가지며, 감쇠정수 h=5%일 때의 내진설계용 스펙트럼과 거의 일치하도록 작성하였다. 입력지진동의 탄성 가속도 응답스펙트럼이 동일한반면, 각 입력지진동띄 위상특성이 다른 인공지진동을 입력하여 다자유도 골조 구조물의 지진응답을 분석하여 건축물의 내진설계용 지진동으로서 타당성을 확인하는 것이 목적이다. 본 논문에서 작성된 인공지진동은 기록지진동에 비해 지진응답치가 안정된 값을 나타내는 것을 확인할 수 있었다. 그러므로 다층 골조구조물의 비선형 지진응답해석용 입력지진동으로 타당성이 높다고 사료되며, 비선형 지진응답해석용 입력지진동의 강도를 탄성 가속도 응답스펙트럼으로 규준화 하는 것이 합리적이라고 사료된다. In seismic response analysis of building structures, the input ground accelerations have considerable effect on the nonlinear response characteristics of structures. The characteristics of soil and the locality of the site where those ground motions were recorded affect on the contents of earthquake waves. Therefore, it is difficult to select appropriate input ground motions for seismic response analysis. This study describes a generation of artificial earthquake wave compatible with seismic design spectrum, and also evaluates the seismic response values of multistory reinforced concrete structures by the simulated earthquake motions. The artificial earthquake wave are generated according to the previously recorded earthquake waves in past major earthquake events. The artificial wave have identical phase angles to the recorded earthquake wave, and their overall response spectra are compatible with seismic design spectrum with 5% critical viscous damping. The input ground motions applied to this study have identical elastic acceleration response spectra, but have different phase angles. The purpose of this study is to investigate their validity as input ground motion for nonlinear seismic response analysis. As expected, the response quantifies by simulated earthquake waves present better stable than those by real recording of ground motion. It was concluded that the artificial earthquake waves generated in this paper are applicable as input ground motions for a seismic response analysis of building structures. It was also found that strength of input ground motions for seismic analysis are suitable to be normalize as elastic acceleration spectra.

Influence of the Sedimentary Cover in the Cologne Area on the Shape of Response Spectra

For the greater area of the city of Cologne a microzonation from an earthquake engineering perspective was introduced. The area has been divided into eight subregions with approximately uniform soil profile. For all regions the influence of the sediments on simulated earthquakes has been investigated by three well known methods: 2-layer solution, SHAKE 91, HASKELL matrix algorithm. The transfer functions and response spectra were computed and compared to the elastic acceleration response spectra of the German building code E-DIN 4149. Two different methods for the generation of synthetic accelerograms and the three wave propagation analysis procedures have been compared and a series of issues relevant to the practical application of them were discussed.