Site-specific Ground Response Analysis Research Articles

Site Specific Non-Linear Ground Response Analysis and Soil Structure Interaction Study of Newly Constructed Dharahara Tower

This study investigates the seismic performance of the recently reconstructed Dharahara tower, a historically significant monument in Nepal that has experienced damage in past earthquakes and was completely destroyed in the recent Gorkha earthquake. Ground Response Analysis (GRA) and Soil-Structure Interaction (SSI) investigations are conducted to assess its structural behavior. GRA includes free field and structure-influenced analyses, with subsequent comparative assessment. Additionally, 3D non-linear finite element analysis is employed to derive equivalent spring constants representing soil and foundation characteristics, which are incorporated into the SSI analysis. These computed spring constants are used to model support conditions, allowing for an evaluation of the super-structural response. The study also employs non-linear dynamic analysis to compare structural responses between fix-based and spring-based models. The results indicate that the presence of the structure significantly influences surface wave motion amplification in GRA, resulting in peak ground accelerations (PGAs) that exhibit de-amplification in the free field and amplification in the presence of the structure. Furthermore, the introduction of an equivalent spring system in the soil-structure model changes the system's vibration period and damping characteristics, leading to enhanced dynamic response compared to the fixed-base model.

A Study on Site Specific Ground Response Analysis in Bihar

The influence of local soil conditions on earthquake earthquakes is assessed using seismic site response analysis. Earthquakes are natural phenomena that have claimed the lives and property of millions of people over the centuries. As a result, classifying these strong ground motions, predicting their damage potential, and suggesting mitigation measures become critical. The present study area is Kanti (Muzaffarpur), which is located in north Bihar and covers a geographical area of 3,132 square kilometres and lies between North Latitude 250 54’00”-260 23’00” and East Longitude 84053’00”- 85045’00” which falls in seismic zone IV of IS 1893: 2016. The geotechnical characterization of the site has been investigated using borehole data collected from various locations. The bedrock depth could not be determined due to a lack of deep boreholes, but traces of rock found in the collected data suggest rock outcrops in this region. According to geotechnical characterization, the soil profile in the region is dominated by silty sands, clayey silts, and poorly graded soils. DEEPSOIL software was used to estimate peak ground acceleration. Peak ground acceleration has been estimated using equivalent linear analysis with soil layer depth, bulk density, shear wave velocities, and damping as inputs.

A site-specific earthquake ground response analysis using a fault-based approach and nonlinear modeling: The Case Pente site (Sulmona, Italy)

In this paper we present the ground response analyses (GRA) of a site where an industrial facility is planned. Due to its location on an active normal fault system known as a relevant seismic gap, the Mt. Morrone Fault system (MMF), and at the edge of a basin filled with slow velocity continental deposits, a inter-disciplinary and non-standard approach has been applied to assess the seismic input of the dynamic numerical analyses. It includes geological, seismological, geotechnical and engineering contributions. Two fault scenarios, MMF1 and MMF2, were considered and scenario-based (SSHA) and probabilistic (time-dependent, TD, and time-independent, TI) seismic hazard (PSHA) analyses were implemented. Comparison among the spectra corresponding to the 90th percentile of the SSHA statistical distribution and the PSHA average ones shows that the SSHA MMF2 has values similar to the PSHA TD model. The SSHA 90th percentile distribution was selected as target spectra to retrieve the seismic input for GRA. Nonlinear numerical simulations of seismic wave propagation were implemented to derive surface ground motion parameters. GRA acceleration response spectra and their PGA are notably higher, and thus on the side of safety, than those obtained following the Italian code approach for seismic resistant buildings. These results confirm that a scenario-based methodology can better capture the shaking effect in near-field conditions, avoiding possibly unconservative underestimations of the seismic actions and in view of a more robust performance-based approach used by engineers for either new design and/or assessment/retrofit purposes of the built environment.

One-dimensional Site Response Analysis and Liquefaction Evaluation of Can Tho City, Vietnam

Can Tho is the biggest city in the Mekong River Delta, one of the five national central cities in Vietnam. However, it has not been studied regarding seismic hazard estimation. For this purpose, one-dimensional nonlinear site response analysis of this city was performed in this paper. The measured in-situ profiles and corresponding geotechnical site investigation and laboratory test data were utilized to develop the site model for site-specific ground response analysis. A suite of earthquake records compatible with the Vietnam rock design spectrum (TCVN 9386:2012) was used as input ground motions at the bedrock. The results show that Peak Ground Acceleration (PGA) increases from the bedrock to the surface. Maximum PGA is 0.083g for O Mon district (P1) and 0.073g for Cai Rang district (P2). The maximum shear strain is reported to be 0.35% for P1 and 0.45% for P2. The recommended amplification factors are 1.7 for P1 and 1.9 for P2. Even though Can Tho city is composed of soft layers, liquefaction is unlikely to occur.

Statistical calibration of two-dimensional seismic aggravation effects for homogeneous basins

Two-dimensional basin effects often play a relevant role in defining earthquake ground motion at sites with deep morphologies. The quantitative estimation of two-dimensional effects requires a numerical approach which is typically complex and computationally demanding. Due to modelling complexities, basin effects are not routinely accounted for and have not received significant attention in seismic design codes. One-dimensional seismic response can be modeled with greater ease but does not allow their confident investigation. The use of simplified approaches which allow the estimation of two-dimensional effects from one-dimensional analyses is thus warranted. Past studies have defined and investigated aggravation factors, which can be applied as multiplicative coefficients to one-dimensional ground response outputs to account for two-dimensional basin effects. This paper proposes a novel framework for estimating basin effects by assigning aggravation factors for a vast range of symmetric basins overlain by a single-layer, homogeneous soil deposit and for varying basin sizes, dynamic geotechnical properties, and seismic inputs. In the study, aggravation factors are defined with reference to pseudo-acceleration response spectrum (5% of critical damping) and are calibrated statistically using a large set of dimensionless parameters from the outputs of an extensive set of one-dimensional and two-dimensional numerical analyses. The calibration process is described along with notable observations regarding the spatial variability of the magnitude of two-dimensional aggravation along the surface of the deposit. The proposed method is amenable to current design code formats involving tabulated partial factors. In principle, aggravation factors obtained in this study can be applied to 1D response spectra developed either from the provisions of the design codes themselves or from site-specific ground response analyses. A discussion focusing on the validation of the proposed approach using experimental and empirical measurements is provided. An example application attests to the simplicity of use of the method.

Vs30-based site classification and assessment of site-specific ground response analysis for densely populated urban areas of Trabzon (NE Turkey)

Vs30-based site classification and assessment of site-specific ground response analysis for densely populated urban areas of Trabzon (NE Turkey)

Evaluation of Seismic Site Amplification Using 1D Site Response Analyses at Ba Dinh Square Area, Vietnam

This study presents a case study on ground response analysis of one of the important cultural heritages in Hanoi, Vietnam. One-dimensional nonlinear and equivalent linear site response analyses which are commonly applied to solve the problem of seismic stress wave propagation are performed at the Ba Dinh square area. A measured in-situ shear wave velocity profile and corresponding geotechnical site investigation and laboratory test data are utilized to develop the site model for site-specific ground response analysis. A suite of earthquake records compatible with Vietnamese Design Code TCVN 9386: 2012 rock design spectrum is used as input ground motions at the bedrock. A few concerns associated with site-specific ground response evaluation are analyzed for both nonlinear and equivalent linear procedures, including shear strains, mobilized shear strength, and peak ground acceleration along with the depth. The results show that the mean maximum shear strains at any soil layer are less than 0.2% in the study area. A deamplification portion within the soil profile is observed at the layer interface with shear wave velocity reversal. The maximum peak ground acceleration (PGA) at the surface is about 0.2 g for equivalent linear analysis and 0.16 g for nonlinear analysis. The ground motions are amplified near the site natural period 0.72 s. The soil factors calculated in this study are 1.95 and 2.07 for nonlinear and equivalent linear analyses, respectively. These values are much different from the current value of 1.15 for site class C in TCVN 9386: 2012. A comparison of calculated response spectra and amplification factors with the local standard code of practice revealed significant discrepancies. It is demonstrated that the TCVN 9386: 2012 soil design spectrum is unable to capture the calculated site amplification in the study area.

Site-Specific Ground Response Analysis of Some Typical Sites in Amaravati Region, Andhra Pradesh, India

Site-Specific Ground Response Analysis of Some Typical Sites in Amaravati Region, Andhra Pradesh, India

Application of empirical and simulation-based site amplification models for Central and Eastern North America to selected sites

The Next Generation Attenuation Relationships for Central & Eastern North-America (NGA-East) Geotechnical Working Group (GWG) has presented models for site amplification in Central and Eastern North America that represent a significant change from past practice, which was based on models developed for active tectonic regions. The GWG models are ergodic in their formulation, meaning that they produce an average level of amplification conditional on VS30 and other the site parameters. We illustrate the application of these models to four sites in Texas, South Carolina, Mississippi, and New York City, and compare results with site-specific ground response analyses. The results indicate that substantial advantage is possible when ergodic models conditioned only on VS30 are supplemented with a modular term that produces a peak at one or more site natural periods ( Tnat). The article demonstrates features and limitations of the GWG models for sites in Central and Eastern North America and provides useful recommendations for coupling ergodic and non-ergodic (site-specific) modeling as part of seismic hazard studies.

Effect of Silt Content on Liquefaction Susceptibility of Fine Saturated River Bed Sands

The effect of silt intrusion on the liquefaction susceptibility of fine saturated sand has been studied here using a series of strain-controlled cyclic triaxial tests on isotropically consolidated soil specimens. The fine sands used in this study were collected from the Ganga and Sone river bed. The samples were prepared with 100% non-plastic silt, 100% sand and different percentage (5%, 10%, 20%, and 30%) of non-plastic silt mixed with fine sand to study the effect of intruded silt on liquefaction susceptibility of sand. It has been found that at the same relative density range (10–25%) and the same percentage of intruded non-plastic silt, the Ganga sand is having higher liquefaction susceptibility than the Sone sand. The outcome of the study also showed that the rate of generation of excess pore water pressure (EPWP) for all three soil specimens was more or less same at higher strain levels (0.66–1.31%). However, the liquefaction potential continues to increase with the increase in silt content at a lower strain rate of 0.13%. A graphical relationship has been proposed for the EPWP development model parameter as a function of non-plastic silt content. This modification in the EPWP model parameter is one of the novel aspects presented here, which can be used for site-specific nonlinear ground response analysis.

Modeling nonlinear site effects in physics-based ground motion simulations of the 2010–2011 Canterbury earthquake sequence

This study examines the performance of nonlinear total stress one-dimensional (1D) wave propagation site response analysis for modeling site effects in physics-based ground motion simulations of the 2010–2011 Canterbury, New Zealand earthquake sequence. This approach explicitly models three-dimensional (3D) ground motion phenomena at the regional scale, and detailed site effects at the local scale. The approach is compared with a more commonly used empirical VS30-based method of computing site amplification for simulated ground motions, as well as prediction via an empirical ground motion model. Site-specific ground response analysis is performed at 20 strong motion stations in Christchurch for 11 earthquakes with 4.7≤ MW≤7.1. When compared with the VS30-based approach, the wave propagation analysis reduces both overall model bias and uncertainty in site-to-site residuals at the fundamental period, and significantly reduces systematic residuals for soft or “atypical” sites that exhibit strong site amplification. The comparable performance in ground motion prediction between the physics-based simulation method and empirical ground motion models suggests the former is a viable approach for generating site-specific ground motions for geotechnical and structural response history analyses.

Estimated Empirical Correlations Between Shear Wave Velocity and SPT-N Value for Indore City Using NLR and ANN

In this paper, an attempt has been made to propose a generalized correlation between shear wave velocity (Vs) and SPT-N values for all soil types for generalized depth using the concepts of regression. Around 40 correlations have been compiled and applied for estimating the shear wave velocity (Vs) correlation for the region and also to address the uncertainty issue. The generated correlation is then used for the computation of Vs for one-dimensional (1D) ground response analysis at two different site locations in Indore region. 1D ground response analysis is performed using DEEPSOILv6.1. Soil profiles at site taken as input for analysis were collected from 245 boreholes at 26 different locations in the Madhya Pradesh region (one of the central states in India), and it can be concluded that Vs–N correlations estimated after reducing the errors applying the multilinear perceptron and generalized regression neural network models using MATLAB coding gave better results over the linear regression analysis applied for the site-specific ground response analysis.

Equivalent Linear and Nonlinear Site-Specific Ground Response Analysis of Pashto Cultural Museum Peshawar, Pakistan

Site-specific ground response analysis is needed for seismic hazard estimation, and its mitigation is required for seismically active regions of Pakistan. The work presented in the following includes response analysis of a specific site at Peshawar Khyber Pakhtunkhwa using equivalent linear (EL) and also nonlinear (NL) analyses. The site model was developed using the geotechnical investigation data from field investigation and subsequent laboratory tests on representative soil samples. The earthquake records compatible to the seismic activities in the target area are selected and matched to the target response spectra in order to obtain input excitation force for the base ground model. Several issues that are related to site-specific ground response analysis, i.e., shear strain, mobilized shear strength and ground acceleration along depth of soil model, are studied and compared for both EL and NL analyses. The analysis results are also further studied and compared for ground response spectra and amplification factor using both EL and NL analyses.

Site-specific ground response analysis at a site in the affected area of the 2016 Pidie Jaya earthquake

Analytical models have demonstrated that they are able to simulate reasonably well the seismic motions at the ground level. The most widely used model is the equivalent linear approach. This equivalent linear model was used to compute the free-field response of Meureudu-Pidie Jaya, Aceh Indonesia’s soft soils during the 2016 Pidie Jaya earthquake. The model computes the ground response of horizontally layered soil deposits subjected to transient and vertically propagating shear waves through the one-dimensional soil column. Each soil layer is assumed to be homogeneous, visco-elastic and infinite in the horizontal extent. The equivalent linear estimation of soil properties is taken to express the nonlinearity of the soil’s shear modulus and damping values. These values are assumed to be a function of shear strain amplitude and determined by an iterative process that must be consistent with the level of the effective strain induced in each sub-layer. Starting with the highest shear modulus and a low damping value, the shear modulus and the damping ratio of each sub-layer are modified. The modification is based on the applicable relationship between both properties and the shear strain. The calculation is repeated until strain-compatible modulus and damping values converge within a tolerance of 1%. This research reveals the ground motions of Pidie Jaya’s soils. The results of the analysis are presented.

Site Response Analysis of Deep Sedimentary Deposits Using Electrical Resistivity Logging; Case Study: Guilan Province, Iran

Local geology of site and its properties can influence the input seismic wave specifications dramatically such as frequency content and duration while passing through soil stratums, making it inevitable to perform site-specific ground response analysis. For such analysis, soil’s dynamic properties including shear wave velocity (Vs) and shear modulus (G) are required, which are usually obtained using laboratory or field tests, commonly too expensive and time consuming for regions having deep sedimentary deposits. Electrical resistance of ground can be put into practice as a cost-effective alternative in assessing soils dynamic properties in order to be utilized in site response analysis, since the subsurface materials such as soil and rock have unique electrical properties. In this study, the feasibility of site response analysis using electrical logging has been evaluated using field data measurements of electrical resistivity and borehole logging through Guilan province, which is located on the southern shoreline of the Caspian Sea and in a region with high seismicity having deep sedimentary deposits. Nonlinear site response analysis as well as equivalent linear one is carried out in order to obtain the spectral response of the region, separately for the eight data points of the study. The acceleration time histories were synthesized using spectral matching technique integrating with probabilistic seismic hazard analysis. According to the results, the NL and EQL response and design spectrums, which are obtained in this study, show decent agreement with Iran’s 2800 seismic design spectrum, indicating acceptable performance of site response analysis using electrical resistivity logging.

Dynamic characterization of fine-grained soils in Central Italy by laboratory testing

The investigation of soil response to dynamic loads is necessary to predict site-specific seismic hazard. This paper presents the results of cyclic and dynamic laboratory tests carried out after the 2016–2017 Central Italy Earthquake sequence, within the framework of the seismic microzonation studies of the most damaged municipalities in the area. The database consists of 79 samples investigated by means of dynamic resonant column tests, cyclic torsional shear tests or cyclic direct simple shear tests. Results are firstly analysed in terms of field and laboratory values of small-strain shear wave velocity, highlighting the influence of the sample disturbance and of the mean effective consolidation pressure. The cyclic threshold shear strains as a function of plasticity index are then compared with findings from the published literature and the outliers are analysed. Subsequently, the dynamic soil behaviour is investigated with reference to the small-strain damping ratio. Differences between results from different tests are analysed in the light of the loading frequencies. Finally, the database is used to develop a predictive model for soil nonlinear curves according to plasticity index, mean effective confining stress, and loading frequency. The model represents a useful tool to predict the nonlinear stress–strain behaviour of Central Italy soils, necessary to perform site-specific ground response analyses.

Site-specific ground response analysis of a proposed bridge site over Barak River along Silchar Bypass Road, India

It is well known that the local soil condition is an important factor in changing the ground motion parameters during earthquake. Therefore, it becomes important to carry out site-specific earthquake risk study for the designing of earthquake-resistant structures due to future hazard. In the present study, a ground response analysis of a proposed bridge site over Barak River along Silchar Bypass Road is carried out to evaluate the local site effect with the real recorded earthquake ground motions available in this study area. Detailed soil investigation report in terms of SPT bore log profile is collected from the Government Agencies (Public Works Department, Govt. of Assam). In the absence of in situ shear wave velocity profile data, the Vs profiles are estimated from the known SPT-N value by proposing new empirical equations correlating Vs and SPT-N. After evaluation of the Vs 30 profiles, the site is then classified according to the provisions of National Earthquake Hazards Reduction Program (NEHRP). The input ground motions used for the analyses are in the form of acceleration time histories obtained from two recorded earthquakes such as Ms 7.2 (India–Burma Border earthquake, 1988) and Mw 6.4 (India–Burma Border earthquake, 1995). The modulus reduction and damping ratio curves are obtained from the different research works published considering the characteristics of subsurface profiles. The ground response analyses have resulted in the calculation of the ground motion parameters as well as the amplification factor, and response spectra at the ground surface for the site. The results have revealed that the ground motion at bed rock level has been highly amplified by the soil layers at three different frequency ranges from 2 to 8 Hz for both the earthquakes with a maximum amplification factor up to 4.6. The average surface level peak ground acceleration for the bridge site is found to be 0.25 and 0.18 g for the Ms = 7.2 and Mw = 6.4 earthquakes, respectively. Further, the averaged response spectrum of both the earthquakes for the bridge site is compared with the response spectrum of the Indian Standard (IS) 1893:2002. The design response spectrum for the bridge site is also developed considering NEHRP provisions. Therefore, the results would be very much useful for the designer, planner and the Govt. of Assam for the safety of such important bridge for earthquake-resistant design to mitigate seismic hazard.

Site Specific Ground Response Analysis for Quantifying Site Amplification at A Regolith Site

DOI: 10.17014/ijog.4.3.159-167A numerical model has demonstrated that it can simulate reasonably well earthquake motions at the ground level during a seismic event. The most widely used model is an equivalent linear approach. The equivalent linear model was used to compute the free-field response of Adelaide regolith during the 1997 Burra earthquake. The aim of this study is to quantify the amplification at the investigated site. The model computed the ground response of horizontally layered soil deposits subjected to transient and vertically propagating shear waves through a one-dimensional-soil column. Each soil layer was assumed to be homogeneous, visco-elastic, and infinite in the horizontal extent. The results of this study were compared to other studies and forward computation of the geotechnical dynamic parameters of the investigated site. The amplification triggered by the 1997 Burra seismic event was deduced. This study reveals the amplification factor up to 3.6 at the studied site.

서울 지역 건축 문화재를 위한 지반 공학 관점에서 본 지진 재해 위험도 평가

Earthquake could cause severe damage to the architectural heritage which should be conserved. The ground shaking by earthquake generates the dynamic loading to the structure on the surface and this dynamic loading can cause damage (such as collapse) to the structure. The magnitude of this dynamic loading is proportional to that of ground shaking. Therefore, seismic hazard can be determined through the evaluation of ground shaking. In this study, seismic hazard of architectural heritages in Seoul is evaluated by site investigation using surface wave method and site-specific ground response analysis.

Site-specific ground response analysis and liquefaction assessment of Vijayawada city (India)

Safety against earthquake hazards can be achieved by considering site safety against geotechnical problems and structural safety against dynamic forces. Geotechnical problems such as amplification, landsliding and soil liquefaction are dangerous in regard to the scale of damage. Assessment of risk against such problems is a part of seismic microzonation process. Seismic risk is highly affected by risk factors due to geological environment and geotechnical properties of soils. In this study, it is attempted to identify and develop hazard maps against seismic hazard for Vijayawada city, India, where the subsoil consists of thick alluvial formations along the river. In particular, the study aims at the evaluation of site effects using the available geotechnical data and carrying out microtremor testing in the study area. The geotechnical zonation of the subsoil of the city suggests a high vulnerability of the physical environment in addition to site amplification of the ground motion phenomena. The ground response analysis at the surface was conducted by 1D equivalent linear method and by microtremor testing. From the ground response analysis, peak acceleration, frequency and amplification parameters were assessed and the city was divided into different zones corresponding to each value. Liquefaction hazard was quantified using SPT-based method in combination with the dynamic analysis. These findings supply an indispensible tool for the seismic retrofitting of the buildings and for the mitigation of the seismic risk for small to medium earthquakes in the city.