Site-specific Response 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.

Seismic hazard assessment and site-specific response spectrum at bed rock level for Ongole city, India: a deterministic framework

Seismic hazard assessment and site-specific response spectrum at bed rock level for Ongole city, India: a deterministic framework

Multipath Transfer-Function Correction Method to Predict Site-Specific Amplification at City Scale

Abstract The site-specific amplification of seismic waves is an essential component of local seismic hazard assessment. It can be evaluated from empirical data, but measurements are feasible just in a limited number of locations. Hence, at the city scale, there is a need for the theoretical prediction and interpolation of the amplification. In this article, we introduce a physics-based method to predict the site-specific amplification and duration in a broad frequency range. The method is based on a novel energy-based concept of the multipath propagation of waves in viscoelastic media with random heterogeneities. The amplification is expressed by the surface-outcrop transfer function of the multipath wave propagation, which is defined by expected values of the energy spectral ratio. The method is applied to the near-surface 2D velocity model in the city of Zürich in Switzerland. The predicted amplification is validated by empirical data at a nearby seismic station, and it is compared with the soil class and other site-condition proxies. Finally, the method performance is demonstrated by the prediction of site-specific seismic waveforms and response spectra for the 2022 ML 4.7 Mulhouse earthquake.

Response Spectrum Design Based on Site Class and Site-Specific Analysis in the Transition Zone

The building structure design needs to pay attention to the seismic code and all its consequences. Building A which will be built in Sleman, Special Region of Yogyakarta is 12.20 km from the Opak Fault causing the Bantul Earthquake of Mw 6.3 in 2006, needs seismic analysis properly using SNI 1726:2019. Based on the site near fault criteria on seismic code, Building A does not belong to the site near fault category, so it used the Probabilistic Seismic Hazard Analysis method. However, considering its distance and magnitude, the value is in the range of the requirements limit. Hence, it is still relevant when compared to the Deterministic Seismic Hazard Analysis method for designing the response spectrum. Based on the site classification in the seismic code, a site that is vulnerable to liquefaction belongs to the site class F and therefore requires site-specific analysis. The site-specific surface response spectrum is taken from the equivalent-linear and non-linear site response analysis using Deepsoil v7.0 software. The response spectrum is also calculated based on site class according to the shear wave velocity (v s) and N-SPT criteria. The site-specific spectral acceleration results are compared to 80% of the site class E spectral acceleration, as required. The site belongs to site class D using v s criteria and belongs to site class E using the N-SPT criteria. Only the equivalent-linear site response spectrum in the modified maximum horizontal direction spectrum is eligible when compared to requirements. Most of the non-linear site response spectrum results or the geometric mean response spectrum of the equivalent-linear site response results can satisfy the requirements compared to 80% of the site class D spectral acceleration because the site response analysis uses the v s parameter. The non-linear site response spectral acceleration is smaller than the equivalent-linear site response spectral acceleration.

Generation of Site-Specific Accelerograms and Response Spectra Involving Sampling Information from Borehole Records

This paper is aimed at serving the needs of structural engineering designers of an important structure (or a group of structures located on the same site) who is seeking guidance on how to obtain accelerograms and/or derive response spectra that accurately represent the site subsoil conditions as informed by the borelogs. The presented site-specific seismic action model may be used to replace the default seismic action model stipulated for the designated site class. Presented in this article is a procedure for generating soil surface motions in an earthquake, and their associated site-specific response spectra, taking into account details of the soil layers. Dynamic site response analyses are involved. The conditional mean spectrum methodology is employed for selecting and scaling accelerograms for obtaining input motion on bedrock. The selection depends on the natural period of both the site and the structure. Multiple borelogs taken from within the same site are analysed to identify the critical soil column models without having to conduct site response analysis on every borelog. The technique for simplifying the soil layers utilising the shear strain profile is introduced to further cut down on the time of analyses. The procedures described in this article have been written into a web-based program that is freely accessible to engineering practitioners.

Mitigation of high-speed train-induced environmental ground vibrations considering open trenches in the soft soil conditions by in-situ tests

This study focuses on the use of open trench wave barriers to prevent undesired high-speed train-induced ground vibrations. A series of full-scale passive isolation tests are performed in the most unfavorable geotechnical conditions at the highest speed passage of the actual moving load on the elevated embankment in resonance case. For this purpose, Sakarya-Pamukova has been considered the target test area of the Istanbul-Ankara HST line in North-Western Turkey. Site-specific acceleration time-histories, both response and frequency spectra in all directions were obtained from the ground motions recorded simultaneously in the far free-field conditions with and without passive isolation applications. In particular, the variation of the surface vibrations perpendicular to the railway line with the trench effect was observed according to the insertion loss in decibels. Results indicated that the peak values of measured velocity time-histories and spectral velocity response at ground surface decrease remarkable in the transversal vibration direction with passive isolation method, even in superficial depth of the open trench. The data measured at the most unfavorable geo-dynamic conditions will contribute to the development of more cost-effective, environmentally friendly and efficient vibration isolation barriers for researchers.

Site-Specific Response Spectra and Accelerograms on Bedrock and Soil Surface

This paper is aimed at serving the needs of structural engineering researchers who are seeking accelerograms that realistically represent the time histories of earthquake ground in support of their own investigations. Every record is identified with a specific earthquake scenario defined by the magnitude–distance combination and site conditions; the intensity of the presented records is consistent with ultimate limit state design requirements for important structures in an intraplate region. Presented in this article are accelerograms that were generated on the soil surface of two example class Ce sites and two example class De sites based on site response analyses of the respective soil column models utilizing bedrock excitations as derived from the conditional mean spectrum (CMS) methodology. The CMS that were developed on rock sites were based on matching with the code spectrum model stipulated by the Australian standard for seismic actions for class Be sites at reference periods of 0.2, 0.5, 1 and 2 s for return periods ranging from 500 to 2500 years. The reference to Australian regulatory documents does not preclude the adoption of the presented materials for engineering applications outside Australia. To reduce modeling uncertainties, the simulation of the soil surface ground motion is specific to the site of interest and is based on information provided by the borelogs. The site-specific simulation of the strong motion is separate to the CMS-based accelerogram selection–scaling for obtaining the bedrock accelerograms (utilizing strong motion data provided by the PEER). The decoupling of the two processes is a departure from the use of the code site response spectrum models and has the merit of reducing modeling uncertainties and achieving more realistic representation of the seismic actions.

Site-Specific Seismic Analysis of Buildings Supported by Lightly Reinforced Precast Concrete Walls

This paper aims to show the application of site-specific response spectra in the analysis of buildings that are supported by lightly reinforced precast concrete walls. Previous surveys on load-bearing precast reinforced concrete walls in multi-storey buildings in low-to-moderate seismic regions have found that many existing precast walls are lightly reinforced with a connection reinforcement ratio less than the wall reinforcement ratio. When these precast walls are subjected to reversed cyclic loads, the lateral response is typically controlled by rocking and the ultimate performance is governed by the ruptures of connection dowels. This paper uses moment–curvature analyses in combination with plastic hinge analyses to evaluate the force–displacement capacity of planar lightly reinforced load-bearing precast walls. The seismic performance of a building supported by these lightly reinforced precast walls can then be assessed by superimposing the capacity curve and the inelastic site-specific response spectra developed for the building site. The proposed analytical approach is illustrated through a case study building. By comparing a lightly reinforced precast wall with a comparable limited ductile reinforced concrete wall, it is also found that, although these two walls exhibit similar force capacities, the ultimate displacement capacity of the lightly reinforced precast wall is significantly lower. This finding highlights the potential seismic vulnerability of lightly reinforced precast walls in some existing buildings.

Dynamic Modal Analyses of Building Structures Employing Site-Specific Response Spectra Versus Code Response Spectrum Models

This paper is aimed at giving structural designers guidance on how to make use of elastic site-specific response spectra for the dynamic modal analysis of a structure in support of its structural design. The use of response spectra in support of the pushover analysis of an RC building forming part of the non-linear static analysis procedure (that can be used to predict seismic demand without relying on the code-stipulated default R factor) is also presented. Seismic analysis of structures based on the use of site-specific response spectra can help to achieve a more optimised, and cost-effective, structural design compared to the conventional approach employing a response spectrum model stipulated by the code for different site classes. Currently, the methodology is only adopted in major projects in which enough resources are available to engage experts who are skilled in operating the procedure; thus, the use of site-specific response spectra in structural engineering practice is still limited despite the merits of the procedure. Deriving a site-specific response spectrum requires a database of representative ground motion records to be developed. Extra analytical tasks to be undertaken include the processing of bore log data, site response analyses, and selection/scaling of bedrock accelerograms for input into site response analyses. Guidelines for implementing this design methodology are currently lacking. To promote the wide adoption of site-specific seismic design, this article presents the procedure for developing the required site-specific design spectra, as well as guidelines for applying these spectra for seismic design based on analyses of linear, or nonlinear, models of the building. Non-linear analysis can be accomplished by dealing with macroscopic models as illustrated in a case study.

Seismic Response of Monolithic and Precast RC Building for Site-Specific Conditions

This paper investigates the seismic response of a rigid and flexible RC building by performing nonlinear time history analysis (NLTHA). In the present study, the numerical model of a 5-storey monolithic RC (MRC) and 5-storey precast RC (PRC) buildings are developed in SAP2000. The buildings are assumed to be situated in Assam and a real Silchar site from Assam is considered. For the NLTHA, six spectrum compatible time histories (SCTH) are considered. The first set comprises of 3 SCTH matched to the Indian seismic code design spectra (ISCDS) and the second set comprises of 3 SCTH matched to the site-specific elastic response spectra (SSERS). The NLTHA results show that the roof displacement of the MRC building is less as compared to the PRC building for all the considered cases. However, the response for both the structures for SSERS compatible time histories is more significant as compared to the ISCDS compatible time histories. It is interesting to note that when the energy dissipation in the structure is evaluated for ISCDS compatible time histories, the damage in PRC building is negligible as compared to MRC building. Moreover, for SSERS compatible time histories, the damage in both the buildings are comparable. The results show the importance of site-specific study and its response on the structure behavior.

Nonlinear stochastic seismic dynamic response analysis of submerged floating tunnel subjected to non-stationary ground motion

Owing to the randomness of seismic excitations, the submerged floating tunnel (SFT), which is a new structure subjected to the combined action of self-weight, buoyancy, and anchorage under seismic excitation, is a nonlinear stochastic dynamic system and the evaluation of its dynamic performance is an issue that must be addressed. In this study, the nonlinear dynamic differential equation of an SFT subjected to seismic dynamic action was systematically derived by considering the wave–structure dynamic coupling interaction, and its numerical solution was obtained based on the Newmark-β integration algorithm. Furthermore, based on the theoretical framework of nonlinear stochastic dynamics and the stochastic seismic model reflecting the characteristics of the site-specific response spectrum, the probability density function (PDF) of the nonlinear seismic dynamic response of the SFT was analyzed, and its seismic dynamic performance was evaluated based on dynamic reliability. Thus, it was found that the randomness of ground motion propagates, fluctuates, evolves, and dissipates in the SFT, and finally reaches the nonlinear seismic dynamic response of the SFT. Additionally, the nonlinear dynamic response of the underwater suspension tunnel is highly sensitive to earthquake excitations. The proposed evaluation framework is an effective tool for evaluating the seismic performance of underwater tunnels.

Engineering site response analysis of Anchorage, Alaska, using site amplifications and random vibration theory

Earthquake records collected at dense arrays of strong-motion stations are often utilized in microzonation studies to evaluate the changes in site response due to variability in site conditions across a region. These studies typically begin with calculating Fourier spectral amplification(s) and then transition to performing engineering site response analyses. It has proven difficult to utilize Fourier spectral amplification(s) to define the appropriate elastic response spectr(um)/(a) for a site or sites. This is because, first, the ground motions recorded at these strong-motion stations have lower intensity and hence do not show the nonlinear site effects observed during higher-intensity earthquakes and, second, Fourier and response spectral amplitudes measure different aspects of ground motions. The strong-motion stations in Anchorage, Alaska, have been recording earthquakes in the region for the last three decades. This study utilizes a database of 95 events from 2004 to 2019 to calculate Fourier spectral amplifications at 35 stations using the generalized inversion technique (GIT). Estimated response spectra have been evaluated at each site by applying those Fourier spectral amplifications to a response spectrum of a reference station through random vibration theory (RVT). Correction factors are also applied within the approach to account for nonlinear site effects. This RVT-based approach is tested using ground motions recorded during the MW7.1 2018 Anchorage Earthquake, and close matches between measured and predicted response spectra are found. The method is then compared with site response analyses using a calibrated 1D equivalent linear (EQL) model of the Delaney Park Downhole Array site. Estimated spectra using the RVT-based approach are, finally, compared with those using Next Generation Attenuation Subduction (NGA-Sub) and NGA-West2 ground-motion models. The proposed method provides a coherent and straightforward way to use GIT-derived Fourier spectral amplifications to directly estimate site-specific response spectra, accounting for nonlinear site effects and without requiring engineering characterization of subsurface soil conditions.

Site-Specific Response Spectra: Guidelines for Engineering Practice

Code response spectrum models, which are used widely in the earthquake-resistant design of buildings, are simple to apply but they do not necessarily represent the real behavior of an earthquake. A code response spectrum model typically incorporates ground motion behavior in a diversity of earthquake scenarios affecting the site and does not represent any specific earthquake scenario. The soil amplification phenomenon is also poorly represented, as the current site classification scheme contains little information over the potential dynamic response behavior of the soil sediments. Site-specific response spectra have the merit of much more accurately representing real behavior. The improvement in accuracy can be translated into significant potential cost savings. Despite all the potential merits of adopting site-specific response spectra, few design engineers make use of these code provisions that have been around for a long time. This lack of uptake of the procedure by structural designers is related to the absence of a coherent set of detailed guidelines to facilitate practical applications. To fill in this knowledge gap, this paper aims at explaining the procedure in detail for generating site-specific response spectra for the seismic design or assessment of buildings. Surface ground motion accelerograms generated from the procedure can also be employed for nonlinear time-history analyses where necessary. A case study is presented to illustrate the procedure in a step-by-step manner.

Seismic performance assessment of NPP concrete containments considering recent ground motions in South Korea

Seismic fragility analysis, a part of seismic probabilistic risk assessment (SPRA), is commonly used to establish the relationship between a representative property of earthquakes and the failure probability of a structure, component, or system. Current guidelines on the SPRA of nuclear power plants (NPPs) used worldwide mainly reflect the earthquake characteristics of the western United States. However, different earthquake characteristics may have a significant impact on the seismic fragility of a structure. Given the concern, this study aimed to investigate the effects of earthquake characteristics on the seismic fragility of concrete containments housing the OPR-1000 reactor. Earthquake time histories were created from 30 ground motions (including those of the 2016 Gyeongju earthquake) by spectral matching to the site-specific response spectrum of Hanbit nuclear power plants in South Korea. Fragility curves of the containment structure were determined under the linear response history analysis using a lumped-mass stick model and 30 ground motions, and were compared in terms of earthquake characteristics. The results showed that the median capacity and high confidence of low probability of failure (HCLPF) tended to highly depend on the sustained maximum acceleration (SMA), and increase when using the time histories which have lower SMA compared with the others.

Preliminary spectral matching analysis of RDE site at Serpong Indonesia

In concurrent with the plan to build small experimental power reactor at Serpong site, site specific response spectra evaluation is required to ensure the reactor safety. Site response spectra involved the spectral matching analysis which incorporates the seismic characteristics of the site and the design spectra. This paper presented the preliminary spectral matching analysis of selected natural earthquake records by comparing Al Atik & Abrahamson (2006) algorithm and Hancock et. al (2010) algorithm. The natural earthquake records were selected based on their similarity of their characteristics such as magnitude, distance resulting from deagregation analysis and site-specific conditions. Two subset periods were employed in the spectral matching analysis. Fourier spectrum and wave envelope analysis showed that both algorithms have maintained the original non-stationary characteristics. PGA, PGV and PGD values resulting from spectral matching have significant changes from the original as an implication of accelerogram amplitude scaling. From the spectral matching analysis, KAU083 record resulting from Hancock et. al (2006) algorithm has yielded the best matched to the target spectra compared to other selected records.

Prediction equation for the fundamental vibration period of concrete gravity dams with impounded water

The design of dam structures requires advanced analysis techniques due to the dam body’s complicated interaction with its surroundings. Consequently, most of the time, it is a must to perform response history analysis during the design and assessment of dam structures. The target fundamental vibration period is necessary to generate ground motion histories compatible with the site-specific response spectrum. In this study, an equation was developed to predict the fundamental vibration period of concrete gravity dams based on an extensive database. First, a wide range of parameters to describe gravity dams’ three-dimensional (3D) geometry and their valleys are determined. A total of 19,440 different 3D numerical models with fluid and solid elements were formed, and the fundamental vibration period values were determined to create the necessary database. Then, multiple nonlinear regression analysis was conducted to propose an equation to predict the fundamental vibration period. The proposed equation could be used to accurately estimate the required fundamental vibration period during the preliminary design stage or the implementation of simplified procedures or during the spectrum matching operations.

ONE DIMENSIONAL SEISMIC RESPONSE ANALYSIS AT THE NON-COMMERCIAL NUCLEAR REACTOR SITE, SERPONG - INDONESIA

One dimensional seismic response analysis on the ground surface of the Non-Commercial Power Reactor (RDNK) site based on the mean uniform hazard spectrum (UHS) and disaggregation analysis has been conducted. The study’s objective was to perform an analysis on site-specific response spectra on the ground surface based on existing mean UHS and disaggregation data of the site that correspond to a 1,000 and 10,000 year return period of earthquakes in compliance with the national nuclear regulatory body requirements of Indonesia. Detailed site characterization was defined based on secondary data of a geotechnical drill-hole, seismic cross-hole, downhole data, and microtremor array data. The dynamic site characteristic analysis was presented along with strong motion selection and processing using two types of strong motion datasets. An investigation of strong motion selection, spectral matching, and scaling has been presented as an essential step in ground motion processing. One-dimensional equivalent linear analysis simulation was performed by computing the processed ground motions. A seismic design spectrum and ground surface response spectra from the two datasets of strong motion, both corresponding to a 10,000 and 1,000 year return period, are presented at the end of this study. This study has shown that in order to establish the appropriate seismic response design spectrum, site-specific data and seismic hazard analysis must be immensely considered.

Site-Specific Response Spectra: 2nd District of Cagayan de Oro City, Philippines

Site-Specific Response Spectra: 2nd District of Cagayan de Oro City, Philippines

Repeatable process for seismic microzonation using 1-D site-specific response spectra assessment approaches. Application to the city of Nice, France

We are testing three different approaches to assess the site effects based on 1D soil column data. The first method follows the Eurocodes 8 (EC8) approach based on the determination of Vs30 soil classes, the second one is based on an empirical relationship between Vs30 and the fundamental resonance frequency of the site (f0) with a response spectra amplification function proposed by Cadet et al. (2013) and the last one is the application of a 1-D equivalent linear simulation. Then, we propose a repeatable methodology to define the zonation and the associated surface response spectrum from individual results. This methodology uses a shape recognition algorithm to build homogeneous response spectra zones and the definition of a specific EC8-like response spectrum adjusted to the distribution of the response spectra in each zone. This has been applied to downtown Nice, a city located on the French Riviera that faces the highest seismic hazard in the French mainland area. The city is built on two different sedimentary valleys that are prone to lithological site effects. The ground acceleration around 1.8 Hz can be 20 times higher in the valleys than the one recorded on the surrounding Jurassic rock outcrop. We defined a 3D geotechnical model, composed of 9 homogenous soil layers. The surface elastic response spectra in pseudo-acceleration obtained with the three methods are compared on the whole city. The results indicate that the amplification functions methodology proposed by Cadet et al. (2012b) provides results closer to the numerical simulations compared to EC8. In addition, in five sites of the French Permanent Accelerometric Network (RAP/RESIF) located in the valley of Nice, the site to reference response spectra ratio from the numerical simulations and the spectra amplification function proposed by Cadet et al. (2012b) were compared to earthquake recordings data. Although the spectra amplification functions are closer to the observations, both evaluations underestimate the amplification as they could not capture complex site geometry. Using the repeatable zonation process on the response spectra from the amplification function, three different zones are defined. The associated specific response spectra are significantly different from the recommended EC8 response spectra.

Seismic Performance Assessment of Istanbul Airport Viaduct According to Turkish Building Seismic Code 2007 by Pushover Analysis

The goal of this study is to examine and evaluate the structural system and seismic performance of the viaduct which is located the west side of the Istanbul Airport. For this purpose, a three-dimensional structural system of the viaduct is modeled by using SAP2000 (Structural Analysis Program) software. The piers of the viaduct consist of two columns. It connects the terminal building and the parking building to each other, twelve spans and designed according to AASHTO (2002). Earthquake effects are considered in the transverse and longitudinal directions by taking into account the site-specific response spectra. The pre-stressed and precast girders which is used in the deck of the viaduct is designed under bending moment and shear force effects considering service loads, such as self-weight and traffic loads. The pre-stress losses and deflection checks are carried out to satisfy the serviceability conditions of the viaduct deck. The elements of the viaduct, such as pier cap, piers and foundation were designed by considering the vertical and lateral loads, so required cross-sections and reinforcement area are determined. In the present paper earthquake performance evaluation of the viaduct is accomplished according to the Turkish Building Seismic Code 2007 (TBSC 2007). Performance evaluation of the viaduct is carried out by applying static pushover analysis, one of the non-linear analysis methods, is applied to the pier located at the middle axis of the viaduct. Under lateral loading, the plastic hinges are developed at the bottom ends of the piers, as anticipated. In the performance evaluation of viaduct piers, the earthquake effect with 10% probability of exceedance over 50 years is considered adopting the parameters given TBSC 2007, whereas the parameters which define the spectrum compared to the Seismic Code of DLH (2007) code. Numerical results are given in tables and figures, comparatively.