Site-specific Spectra Research Articles

Enhancing Seismic Performance: A Comprehensive Study on Masonry and Reinforced Concrete Structures Considering Soil Properties and Environmental Impact Assessment

Approximately 20,000 people are killed annually on average by building and infrastructure collapses and failures caused by seismic activities. In earlier times, seismic design codes and specifications set minimal requirements for life safety performance levels. Earthquakes can be thought of as recurring events in seismically active areas, with severity states ranging from serviceability to ultimate levels. Buildings designed in accordance with site-specific response spectra, which take into account soil properties based on ground motion amplification data, are better at withstanding such forces and serving their design purposes. This study aims to investigate the site response of reinforced and masonry buildings, considering the effect of soil properties based on the amplification of ground motion data, and to compare the life cycle assessment of the buildings under consideration based on the design and the site-specific response spectrum. In terms of soil properties and site-specific response spectra, STRATA is used to determine the site-specific response for the considered locations for a return period of 475 years for 100 realizations based on the randomization of site properties. For structural analysis, AxisVM software, which is a compatible finite element analysis, is used for building design and analysis, generating comparative results based on the design- and site-specific spectra. To determine and identify potential failures in the model, response spectra were applied to understand the difference in horizontal deflection in two different instances (for elastic design- and site-specific spectra). After building design and analysis is performed, a life cycle analysis in terms of environmental impact assesments using OpenLCA and IdematLightLCA is done. This is done to ascertain the additional expenses in terms of ecocosts and carbon footprints on some failed elements in the structure which are required to make the buildings more resilient when the site-specific response spectrum is applied and to compare the potential economic losses that may occur based on ecological costs. The study presents a comprehensive investigation into the seismic response of masonry and reinforced concrete buildings in Győr, Hungary, incorporating advanced geophysical techniques like multichannel surface wave (MASW) and structural analysis software, AxisVM. Additionally, tailored retrofitting strategies are explored to enhance structural resilience in seismic-prone regions. Significant ground amplifications in soil properties across different profiles are revealed, emphasizing the effectiveness of these strategies in reducing structural deflection and improving resilience. Highlights of the results are observed where the site-specific response spectra are higher than the EC8 design response spectrum. Furthermore, the research underscores the substantial environmental impact, considering both ecocosts and CO2 emissions associated with retrofitting measures, highlighting the importance of sustainable structural interventions in mitigating seismic risks.

Comparison of Performance Analysis Results with Developed Site-Specific Response Spectra and Turkish Seismic Design Code: A Case Study from the SW Türkiye Region

On 6 February 2023, the Kahramanmaraş earthquakes clearly showed that the elastic spectrum curves in TBEC-2018 are insufficient to represent earthquake behavior. In this study, the effect of using a site-specific spectrum curve instead of the elastic spectrum given in TBEC-2018 on the earthquake safety of a building is investigated. For this purpose, the provinces in southwest Anatolia, Türkiye, which is one of the most tectonically complex regions with frequent seismic events, were selected. In the first stage of the study, spectrum curves were obtained for earthquakes with return periods of 2475, 475, and 72 years for each of the provinces in this region. These spectrum curves were obtained using probabilistic seismic hazard studies that take into account the active faults of the provinces and earthquake activity in both historical and instrumental periods. In the second stage of the study, analytical models of a selected model RC building were created according to each province, and static pushover analyses of these building models were performed both according to the elastic spectrum given in TBEC-2018 and according to the spectrum curve created specifically for the province. The results of the analyses show that the change in the spectrum changes the target displacement level of the buildings, and as a result, the cross-sectional damage zone of the structural elements under the earthquake effect is changed. So much so that using the site-specific instead of the elastic spectrum given in TBEC-2018 changed the damage zone of 43% of the beams and 26.4% of the columns in the İzmir model. The change in the section damage zones changed the performance level of some floors of the models and the performance level of the building. The study revealed the importance of using the most realistic elastic spectrum curves in order to determine the earthquake performance of buildings that is as close as possible to their behavior in a possible earthquake.

Evaluation of the Seismic Response of Reinforced Concrete Buildings Based on Time-History Analysis considering Nonlinear Soil Effects

ABSTRACT This paper presents a practical procedure using nonlinear time-history analysis to assess the seismic demand of reinforced concrete buildings considering nonlinear soil effects. The purpose of this paper is to employ a spectral method to avoid soil-structure-interaction analysis considering nonlinear site-specific conditions. In this regard, structural models were assessed by dynamic analysis using site-specific spectra that included soil-nonlinearity. Ground motion records compatible with target spectra were scaled based on a wavelet-based algorithm. The results indicate that the structural drift and force demand increase considerably due to soil-nonlinearity. Furthermore, the soil-nonlinearity leads to larger structural responses at clayey sites than at sandy ones.

Spectrum auctions in a thin market: The Korean case

In 2010, the Korean government adopted spectrum auctions and introduced a market mechanism into spectrum management. However, the government has often been confronted with conflicts between diverse policy goals of spectrum auctions. A thin spectrum market, where only three incumbent MNOs bid for spectrum, has led to concerns that the government may fail to maximize revenues.Based on the past experiences in Korea, this paper examines the Korean government's choice of auction rules in the face of conflicting policy goals. This paper also recommends that the government implement the following regulatory reforms and consider the auction related measures to deepen its spectrum market or increase the number of bidders: (i) relaxation of foreign ownership restrictions, (ii) introduction of regional or site-specific spectrum licenses, and (iii) modification of auction formats. Spectrum markets tend to be thin in many countries, and the Korean experience may offer implications for those countries when they implement spectrum auctions.

An Overview of the Seismic Elastic Response Spectra and Their Application According to Mexican, U.S., and International Building Codes

The design of earthquake-resistant structures by applying traditional or performance-based seismic analysis methods involves two large variables: the seismic risk of the area and the physical characteristics of the structure. Before analyzing any building, it is required to determine the seismicity in the location to evaluate the accelerations that the structure must withstand by deterministic or probabilistic methods. The typical results of a seismic study are the uniform hazard spectra in the rock layer related to a specific return period and structural damping. The building codes use different methods to obtain the elastic response spectra, seeking to offer simple procedures by using parametric factors to consider the soil type; however, the procedure tends to return conservative estimates. On the other hand, site-specific spectra offer accurate and less conservative acceleration values, with the disadvantage of an extensive and costly mathematical process, justifying their application mostly to important structures. This review article gives the state of the art of seismic elastic response spectra using probabilistic seismic hazard maps as inputs, taking into account the importance of the structure and the soil type, according to Mexican, U.S., and international building codes.

Source- and Site-Specific Earthquake Ground Motions

Seismic design is the preparation for earthquake ground motions considering the seismicity and seismic amplification properties of the ground at the target site. However, the effects of source, path, and site amplification characteristics are not sufficiently anticipated in seismic codes. Regarding the source and path characteristics, earthquakes that have the strongest influence on the target site should be considered specifically, and, concerning seismic amplification, the effects of not only a shallow subsurface but also a deep subsurface should be considered. This article takes the design spectra of Japanese highway bridges as an object and compares them with the spectra produced by a ground motion prediction equation and the source- and site-specific spectra evaluated using a state-of-the-art method. The results show that the spectra differ greatly. In this way, the necessity of the application of a state-of-the-art technique in the evaluation of source, path, and site amplification characteristics is demonstrated.

Local site effect incorporation in probabilistic seismic hazard analysis – A case study from southern peninsular India, an intraplate region

The inclusion of local site effects into seismic hazard analysis is an important issue and has been attempted previously in both deterministic and probabilistic manner. The present study is an attempt to combine the local site response with the standard probabilistic seismic hazard analysis. The site response was computed by performing an equivalent linear analysis in the frequency domain. The input soil profiles for the analysis were taken from the borehole data of the North Kerala region (one of the Southerly states in India). The uncertainty in estimating the shear velocity profile (VS) has been addressed by applying multiple VS–N correlations. The variability in the choice of input motions has been reduced by selecting multiple ground motions representing distinct hazard levels (return period of 50–2000 years). The uniform hazard spectrum developed for the host reference site conditions has been adjusted to the target region and the input motions are scaled accordingly. The analyzed soil profiles were categorized into three distinct soil types namely ‘Sand’, ‘Clay’ and ‘All soil’ based on the predominant soil content. The empirical amplification equation as a function of input rock spectral acceleration (Sar) was developed for each soil type. ‘Sand’ exhibits nonlinear behavior for Sar > 0.1 g whereas ‘clay’ demonstrates sustained amplification at longer periods. The average spectral amplification observed is 3 for ‘All soil’, 5 for ‘clay’ and 3.5 for ‘sand’ in the study region. The regionally developed amplification function aids in transforming a Ground Motion Prediction Equation (GMPE) from generic to site-specific. The modified GMPE is integrated with the regional seismic source model to estimate site-specific probabilistic seismic hazard. The study produces site-specific spectrum and surface hazard maps which can be of direct use to planners and designers in creating a seismic resilient built environment.

PSHA of Van province for performance assessment using spectrally matched strong ground motion records

Within the framework of the performance based earthquake engineering, site specific earthquake spectra for Van province has been obtained. It is noteworthy that, in probabilistic seismic hazard assessment, as a first stage data from geological studies and records from the instrumental period were compiled to make a seismic source characterization for the study region. The probabilistic seismic hazard curves were developed based on selected appropriate attenuation relationships, at rock sites, with a probability of exceedance 2, 10 and 50% in 50 yrs period. The obtained results are compared with the spectral responses proposed for seismic evaluation and retrofit of building structure in Turkish Earthquake Code (2007), section 7. The acceleration response spectrums obtained from probabilistic seismic hazard analysis are matched to adjust earthquake accelerograms recorded during the 2011 Van earthquakes by using SeismoMatch v2.0 software. The aim of this procedure is to obtain a set of reasonable earthquake input motions for the seismic evaluation of existing buildings.

Seismic behavior and zoning of the sabkha soils in Jubail industrial city, Saudi Arabia

This study aimed at the micro-level seismic behavior and zoning of the saline sabkha strata in Jubail industrial area in Eastern Saudi Arabia. It encompasses the evaluation of the site-specific seismic response parameters and the liquefaction potential for various possible subsurface conditions under the probable seismic event(s). The approach to achieve the objectives of this study included the following: analysis of geologic, hydrologic, and geotechnical data of the area; performance of field and laboratory dynamic testing; and dynamic modeling and analysis of the subsurface profiles. The results of the simulation have been used to develop liquefaction potential maps and site-specific spectra of the study area, consisting of ten seismic zones under a range of probable peak horizontal ground acceleration (PHA). Results do not show significant probability of liquefaction of the loose soil layers in the study area at the maximum possible design PHA of 0.035 g; however, liquefaction is anticipated at higher PHA values. Site-specific spectral response resulted in values of S s and S 1 spectral accelerations to be different as compared to those suggested by local standards. The resulting seismic micro-zonation maps and the corresponding parameters are very useful for the stability analysis of the existing and planned structures in the Jubail area.

Site-specific probabilistic seismic hazard analysis for northern part of the Qeshm Island, Iran

This paper presents results of a site-specific probabilistic seismic hazard analysis for northern part of the Qeshm Island, one the most seismic prone areas of Iran. Seismotectonic and seismicity properties of seismic sources in the study area were characterized and used for evaluation of various strong ground motion parameters implementing the classical Cornell’s PSHA approach. The results show that peak rock accelerations for 475-year return period are 0.4 and 0.27 g, respectively, for 84th and 50th percentiles while being about 0.37 and 0.61 g for 2475-year return period. These values are slightly smaller than those read from national seismic zonation maps which can be attributed to the considered conservatism for development of such design maps. In order to incorporate local site conditions, a series of dynamic site response analyses based on the equivalent linear approach were also employed. The results indicate that the presence of soft subsurface deposits at the site significantly alters the fundamental characteristics of the response spectra. The obtained median (50th percentile) peak ground accelerations for 975-year return period range between 0.49 and 0.54 g at different locations in the study site showing minor amplifications relative to their corresponding bedrock acceleration of 0.48 g. Finally, the obtained site-specific spectrum was compared with the standard spectrum mandated by the design codes. In this regard, the agreement was found to be reasonable at period ranges shorter than about 0.5 s, while the differences were more obvious at longer periods. This reveals the need for implementation of site-specific design spectrum to avoid underestimation or overestimation of seismic forces for designing critically important structures especially when softer deposits are encountered.

A Multi-step approach to generate response-spectrum-compatible artificial earthquake accelerograms

Time history records are essential for nonlinear dynamic analysis to determine the response of structures. Considering lack of enough earthquake records, generation of artificial earthquake records and spectrum-matched records are the best method in this regard. This study is motivated by real life applications of designing new structures or evaluating the performance of current ones in Afghanistan where two structures are to be designed and built to withstand earthquakes. In this paper, design response spectrum and time history records are generated for two sites located within the city of Kabul, Afghanistan. The Probabilistic Seismic Hazard Assessment (PSHA) results are employed initially to produce the required parameters and data. Then, the generalized nonstationary Kanai-Tajimi model is applied to simulate the ground acceleration time history using the identified characteristics of the site from preliminary ARMA (Auto Regressive Moving Average) analysis and the site-specific analysis. The response spectrum is developed and iteratively compared to the ARMA model and the site-specific spectrum until a satisfactory match is achieved. Finally, the time domain description of the spectrum-compatible artificial earthquake record is developed exploiting inverse FFT of the design response spectrum. The total errors in spectral matching generated accelerograms are compared to results from a commercially available software. Results demonstrated the effectiveness and robustness of the adapted approach.

Comparative approach to seismic vulnerability of an elevated steel tank within a reinforced concrete chimney

This study provides a framework for investigating the seismicresponse of an elevated steel water tank within a reinforcedconcrete chimney, to assist optimal tank placement and analysedifferent tank geometries. Elevated tank design procedures indifferent guidelines and codes are adequate for specific cases,none of which meets the exact requirements of this case study,in which the supporting structure mass is large relative to thestorage tank. The tank is located at an elevation 63 m belowthe mid-height of the 200 m chimney, resulting in a differentbehavior than a simple cantilever. Furthermore, for certainH/R ratios, coupling effects may exist between the fundamentalperiod of the chimney and that of the sloshing wave. An equivalentmodel is examined that is simple enough yet able to accuratelyproduce the design acceleration, dynamic amplification,damping and torsional effects at the chosen tank location, andto capture site effects. An analysis of the tank at ground level isconducted according to AWWA D100-11. Then, the tank at elevation63 m is analysed within the framework of three existingmethods using code spectra and site-specific spectra. A novelfourth method is then proposed which, contrary to the existingmethods, can accurately capture the conditions of this casestudy by combining the benefits of all methods. The workflowdescribed here can be readily applied to other cases of elevatedtanks for which the standard procedures are inadequate.

Seismic fragility analysis of a pile-supported wharf using capacity spectrum method

In this study, seismic fragility curves are derived for an existing pile-supported wharf, for three levels of earthquake motions, i.e., serviceability earthquake (SE), design-based earthquake (DBE) and maximum considered earthquake (MCE). The wharf is modelled using nonlinear platform along with soil structure interaction. Pushover analysis is performed to obtain its capacity curve. Site-specific spectrum is constructed and correspondingly seismic events are selected to represent demand. Using capacity spectrum method, maximum displacements at deck level are obtained to create response matrix. Damage states are established. Based on damage states and response matrix, fragility curves of wharf are constructed. It is observed that the port site has higher ground motions than specified in Indian standard. Indian standard thus underestimates the fragility of wharf, stating it to be functional for DBE and MCE. The site-specific spectrum clearly finds the wharf deficient, requiring urgent repairs to be serviceable and to resist future seismic events.

Displacement of the Buildings According to Site-Specific Earthquake Spectra

The probabilistic seismic hazard curves were based on appropriate attenuation relationships at rock sites with a probability of exceedance of 10% in 50 years in this study. Results from the model were compared to the response spectra proposed in Section 7 of TEC ‘07 and were found to dier in both amplitude and frequency content. The impact of these dierences has been investigated with respect to building performance evaluation. Specifically, modal capacity diagrams and response spectra have been obtained for five buildings. Based on the diagrams and spectra, peak displacements have been calculated as well, revealing significant dierences in the demand displacement curves of the buildings. As a result, damage estimates and predicted building performance will deviate from site specific performance to a greater degree. Using site-specific spectra and field data will be important for future earthquake-resistant design. One of the conclusions of the study is that the Code spectra do not oer a sucient or comprehensive enough set of seismic demands and would lead to an under estimation of seismic hazard in the region of study. Therefore, site-specific design spectra for the region should be developed which reflect the characteristics of local sites.

Letter from the editor

Letter from the editor

Ultrafast electronic processes in an insulator: The Be and O sites in BeO

The short-time dynamics of amorphous beryllium oxide (a-BeO) has been investigated for electronic excitation/ionization by fast incident electrons, as well as by Ar7+, Ar15+, Xe15+, and Xe31+ ions at velocities of 6–10% the speed of light. Site specific Auger-electron spectra induced by fast heavy ions are the central point of this investigation. Electron induced Auger spectra serve as a reference and electron-energy loss (EELS) spectroscopy as well as resonant inelastic X-ray scattering (RIXS) are invoked for quantitative understanding. For the heavy-ion case, we observe strong variations in the corresponding spectral distributions of Be–K and O–K Auger lines. These are related to local changes of the electron density, of the electron temperature and even of the electronic band structure of BeO on a femtosecond time scale after the passage of highly charged heavy ions.

Non linear push over assessment of heritage buildings in Istanbul to define seismic risk

The objectives of the Istanbul Seismic Risk Mitigation and Emergency Preparedness Project are to improve Istanbul’s preparedness for a potential earthquake. Within this framework “Risk Assessment of Cultural Heritage Buildings” was designed to address the vulnerability of cultural assets, specifically buildings with global cultural heritage value. One of the components of the project was the vulnerability and risk assessment of 170 historical buildings. After a discussion of the choice of the most appropriate earthquake scenario, the methodology used for assessing the effects of local site conditions on the seismic performance of selected cultural heritage buildings is presented. The purpose is to estimate the earthquake characteristics on the ground surface based on the earthquake characteristics on the engineering bedrock outcrop obtained from the probabilistic and deterministic hazard studies. The site specific elastic design spectra for each site are then further manipulated to obtain site specific non linear displacement spectra, so that these can be directly compared with capacity curves for the buildings obtained by using plasticity based limit state analysis. The procedure for obtaining the capacity curves is described and the choice of the most appropriate level of ductility and the equivalent reduction coefficient are discussed. A procedure to evaluate performance points and to define safety factors based on lateral acceleration, drift or expected damage level, is presented. The process of arriving at a risk evaluation and hence recommendation for strengthening or otherwise, is finally highlighted with respect to two comparable case studies.

New Insight into the IR-Spectra/Structure Relationship in Amyloid Fibrils: A Theoretical Study on a Prion Peptide

Molecular-level structural information on amyloid aggregates is of great importance for the understanding of protein-misfolding-related deseases. Nevertheless, this kind of information is experimentally difficult to obtain. In this work, we used molecular dynamics (MD) simulations combined with a mixed quantum mechanics/molecular mechanics theoretical methodology, the perturbed matrix method (PMM), in order to study the amide I' IR spectrum of fibrils formed by a short peptide, the H1 peptide, derived from residues 109 through 122 of the Syrian hamster prion protein. The PMM/MD approach allows isolation of the amide I' signal arising from any desired peptide group of the polypeptide chain and quantification of the effect of the excitonic coupling on the frequency position. The calculated single-residue signals were found to be in good agreement with the experimental site-specific spectra obtained by means of isotope-labeled IR spectroscopy, providing a means for their interpretation at the molecular level. In particular, our results confirm the experimental hypothesis that residues ala117 are aligned in all strands and that the alignment gives rise to a red shift of the corresponding site-specific amide I' mode due to strong excitonic coupling among the ala117 peptide groups. In addition, our data show that a red shift of the amide I' band due to strong excitonic coupling can also occur for amino acids adjacent in sequence to the aligned ones. Thus, a red shift of the signal of a given isotope-labeled amino acid does not necessarily imply that the peptide groups under consideration are aligned in the β-sheet.

Site-specific electronic configurations of Fe 3d states by energy loss by channeled electrons

Site-specific configurations of Fe 3d electrons in a spinel ferrite were investigated by electron energy loss spectroscopy under electron channeling conditions. Site-specific spectra were extracted by applying a multivariate curve resolution (MCR) technique to the data set. An electronic difference in the Fe sites caused by ligand field splitting of trivalent Fe was probed. This demonstrated the promise of site-specific valence and spin state analysis in spintronics applications of spinel ferrites.

A Site Specific Study on Evaluation of Design Ground Motion Parameters

Design ground motions are usually developed by one of the two approaches: site-specific analyses or from provisions of building codes. Although contemporary codes do consider approximately the site effects, they provide more conservative estimates. Hence it is preferred to carry out site specific analysis which involves both the seismic hazard analysis and ground response analysis. This article presents a site specific analysis for a seismically vulnerable site near Ahmedabad, Gujarat. The seismic hazard analysis was carried out by DSHA approach considering seismicity and seismotectonics within 250km radius. The site is predominantly characterized by deep stiff sandy clay deposits. Extensive shear wave velocity measurement by cross hole test is used for site classification and ground response analysis. The ground response analysis was carried out by equivalent linear approach using SHAKE2000. It is found that the deep stiff soil site considered is found to amplify the ground motion. The site specific response spectra obtained from RRS analysis is compared with the codal provision which reveals high spectral acceleration in site specific spectra for mid period range.