Linear Ground Response Analysis Research Articles

2D equivalent linear ground response analysis for randomized site profiles

AbstractLocal soil conditions play a crucial role in shaping ground surface responses and impacting the intensity of ground shaking. In this study, the influence of different site profiles on computed ground motion was investigated using a 2D equivalent linear analysis approach. Four distinct site profiles: sand, clay, sand-clay-sand-clay, and clay-sand-clay-sand profiles were considered. The results were presented using multiple metrics, including surface acceleration, displacement, modulus decreasing ratio, and coherence analysis. Notably, the clay profile significantly influenced ground motion, while the sand profile exhibited relatively lower seismic activity. This suggests that softer sites significantly influence ground motion, leading to potentially high levels of shaking.

Equivalent Linear Ground Response Analysis Considering Statistical Randomization of Shear Wave Velocity

Equivalent Linear Ground Response Analysis Considering Statistical Randomization of Shear Wave Velocity

Seismic site classification of Samandag district, Hatay province, Turkey, based on the HVSR method and equivalent linear ground response analysis

Seismic site classification of Samandag district, Hatay province, Turkey, based on the HVSR method and equivalent linear ground response analysis

Site specific seismic hazard analysis of monumental site Dharahara, Kathmandu, Nepal

This study was carried out to estimate the seismic requirement for analyzing and designing the monumental structure, Dharahara, in Kathmandu, Nepal. A probabilistic seismic hazard analysis of the study region was performed to develop the elastic response spectrum for the bedrock site. The obtained spectrum was compared with the existing seismic codes, NBC 105:2020 and IS 1893:2016, to estimate the target response spectrum. One-dimensional equivalent linear (EQL) and non-linear (NL) ground response analyses were performed using DEEPSOIL v7, incorporating a suite of ground motions. The three borehole logs exhibited very soft soil in the region. Due to the presence of soft soil strata in the region under study, strength-corrected modulus reduction and damping curves were adopted in the current study to overcome the effect of larger shear strain. The average response spectra from EQL analyses predicted higher values than NL analyses. Finally, a comparison of the proposed design response spectrum with the code spectra was performed. Comparisons revealed that the mean EQL and NL outputs fall in between the design spectra of similar soil classes in NBC 105:2020 and IS 1893:2016 seismic codes.

Numeričko ispitivanje seizmičkog ponašanja željezničkog nasipa u hladnim područjima

To investigate more fully seismic behaviour of the Qinghai-Tibet railway embankment, a comprehensive discussion and a781nalysis is conducted in this paper by applying a numerical technique. Specifically, the one dimensional equivalent linear ground response analysis was conducted in permafrost regions. On this basis, the seismic response of a typical railway embankment was further studied by applying the nonlinear dynamic finite element analysis method. As a result, nonlinear behaviour of permafrost sites was determined, and the dynamic acceleration, velocity and displacement of the embankment was discussed and the quantitative assessment was approximately estimated. The results indicate that the dynamic response of the embankment has distinct nonlinear characteristics. The peak ground acceleration coefficient at the embankment shoulder is larger than the natural ground surface, marking a 73% increase compared to the coefficient on the natural ground surface. When the seismic intensity reaches a certain value, a plastic zone gradually appears in the embankment, and a continuous extension of the plastic zone can be noted with an increase in peak acceleration of the input seismic wave. The findings of this research may provide an additional insight and have significant implications for further research of cold regions.

Influence of trapped soft/stiff soil layer in seismic site response analysis

As the ground response analysis serves an integral part of site specific seismic hazard study to obtain design ground motion, a proper and accurate estimation should be of prime importance. The paper presents a study on the effect of trapped soft and stiff soil layer on equivalent linear ground response analysis implemented in computer program STRATA. For this purpose, the concept of normally stiff and inversely stiff soil profiles have been introduced. The study clearly indicates the higher impact of a trapped soft soil layer profile, i.e., inversely stiff soil profile with soft layer, in comparison with trapped stiff layer profile, i.e., inversely stiff profile with stiff layer. For low to moderate ground motions, as the depth of the trapped soft layer increases, peak amplification and peak frequency reduces, and for high intensity input ground motion, significant reduction only in the peak frequencies is observed. On the other hand, as the depth of trapped stiff soil layer increases the outcome of ground response analysis remain quite similar. Peak transfer function, peak frequency, peak spectral ratio and peak spectral acceleration are found to exhibit a COV ≤ 60 to 100% for all combinations of IS-Soft profiles, whereas, IS-Stiff profiles exhibit a maximum COV ≤ 15 to 25% for all the considered input ground motions. Computed normalized-root mean square error (Norm-RMSE) values also clearly indicate the higher deviations in the ground response analysis for different combinations of trapped soft soil profiles, from that of normally stiff profile, whereas, trapped stiff layer profiles show lower deviations in the Norm-RMSE values. The profiles with trapped soft layer exhibit a Norm-RMSE value ≤0.8, whereas, trapped stiff layer profiles exhibit a Norm-RMSE value ≤0.2, which clearly demonstrate the large deviations in the outcome of ground response analysis in case of trapped soft layer profiles.

A Comparison between Linear and Equivalent Linear Ground Response Analysis of the Sub-Soil of Ganakbari, Dhaka, Bangladesh

A Comparison between Linear and Equivalent Linear Ground Response Analysis of the Sub-Soil of Ganakbari, Dhaka, Bangladesh

Yield acceleration of reinforced soil slopes using the modified pseudo-dynamic method

This study presents the yield acceleration of reinforced soil slopes using the horizontal slice approach. Yield acceleration plays a key role in calculating the permanent seismic displacement of slopes. The modified pseudo-dynamic method, in conjunction with the equivalent linear site response analysis, is used. Unlike the pseudo-static analysis, the pseudo-dynamic method takes into account the effects of time and phase difference of waves propagation. The developed computer code is used to compute the yield acceleration. Using the planar and log-spiral slip surfaces, this code considers the distribution of reinforcement layers as uniform and variable spacing. The effect of surcharge pressure is also considered. According to the results, the modified pseudo-dynamic method using the equivalent linear ground response analysis led to more critical results than other methods.

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.

Influence of site-specific soil amplification on seismic response of piles in liquefiable soils

Kolkata city in eastern India is spread along the banks of Hooghly River in a north–south direction and having typical alluvial soil which is generally soft and thick in nature. The city is situated in seismic zones III and IV and is an implication of moderate to high seismic risk. Hence in the present study, the influence of ground response analysis and subsequent soil amplification in the design of pile foundations in liquefiable soils is thoroughly discussed. One-dimensional equivalent linear ground response analysis of Kolkata city is conducted using SHAKE2000 computer program and 1989 Loma Gilroy, 1995 Kobe, 2001 Bhuj and 2011 Sikkim motions being the chosen input ground motions. The spectral acceleration at a damping ratio of 5% is seen to be 0.41 g, while the amplification factor of maximum horizontal acceleration is found to be 2.98 when 2001 Bhuj motion is the selected earthquake motion. The high magnitudes of soil amplification are attributed to the alluvial soil in maximum parts of the city. The analysis is further extended to earthquake resistant analysis of pile foundation embedded in liquefying and non-liquefying soil strata and exposed to combined loadings. The maximum bending moment is noticed at the boundary of the liquefying and non-liquefying soil layers with the depth of liquefying soil layer being almost 65% of total pile length. The importance of deflection and bending moment of the pile foundation as important parameters in seismic analysis of deep foundations is portrayed in the current study. The present results and design charts can be used by engineers for designing pile foundations against earthquake forces.

Comparative Study of Equivalent Linear and Non-Linear Ground Response Analysis for Rapar District of Kutch, India

Comparative Study of Equivalent Linear and Non-Linear Ground Response Analysis for Rapar District of Kutch, India

Importance of Site-Specific Dynamic Soil Properties for Seismic Ground Response Studies

This article highlights the implication of site-specific properties on seismic ground response studies. One-dimensional equivalent linear ground response analysis was carried out using site-specific dynamic properties of locally available soils of Guwahati city, and the results are compared with those obtained using existing strain-dependent dynamic properties. Acceleration time histories from three strong motions were used. It was observed that an input motion having a higher peak bedrock acceleration, utilizing experimentally obtained dynamic soil properties, exhibits 38% and 24% lower peak ground acceleration and peak spectral acceleration, respectively, in comparison to the results obtained using standard VD-SI soil models. The amplification characteristics of the strong motions are observed to be significantly influenced by the degradation of damping ratio beyond 1% shear strain. The results highlight the necessity of conducting GRA of any region considering its regional dynamic soil properties to obtain more realistic outcomes.

Ground response analysis and liquefaction hazard assessment for Vishakhapatnam city

Liquefaction is a complex phenomenon where the soil is subjected to high strain levels due to dynamic loading at the time of seismic events, contributing to severe damage and collapse of the structures. The effect of liquefaction can be predicted in three stages, i.e., evaluation of susceptibility, hazard and deformations. Soil susceptibility to liquefaction can be assessed using the geotechnical properties such as grain size, age of the soil deposit, penetration resistance of the soil, whereas hazard can be assessed in terms of factor of safety estimated against liquefaction. In the present study, one-dimensional equivalent linear ground response analysis has been carried in the study area Vishakhapatnam, Andhra Pradesh (India) and the surface peak ground acceleration (PGA) has been estimated using DEEPSOIL. The surface PGA values obtained have been used in liquefaction hazard assessment using stress-based method (SBM) and energy-based method (EBM). Hazard maps were generated from the estimated values of PGA and factor of safety against liquefaction (F L). The surface PGA values obtained are in the range of 0.09–0.14 g which are higher than 0.1 g (limiting value provided by Seismic code of India (IS: 1893-2002)). It is observed that the locations in the central part of the city are prone to higher accelerations comparatively. From liquefaction potential assessment, it is evident that most of the locations in northern and central parts of the city are prone to liquefaction. As the study area has two operational ports and is highly industrialized, findings from the present study will be helpful in retrofitting, analysis and design of structures, therefore, solving practical challenges in structural and geotechnical engineering.

Assessment of liquefaction potential of Guwahati city by probabilistic approaches

This paper presents a probabilistic assessment of the liquefaction potential of Guwahati city, in the northeastern region of India, by using eight probabilistic approaches. Northeastern region of India is one of the six most seismically active regions of the world. The assessment was done for saturated cohesionless deposits. Probabilistic liquefaction assessment is done in terms of probability of liquefaction. According to many researchers, probability of liquefaction is a better index for assessment of liquefaction than factor of safety obtained by the deterministic approach. In this paper, a review of the eight probabilistic approaches has been done and a comparative study of liquefaction potential of soil sites susceptible to liquefaction has been done using the eight SPT-based probabilistic approaches. Most of the approaches are based on logistic regression analysis of field performance data to determine empirical equations for evaluating the probability of liquefaction. Departing from logistic regression approach others have used a Bayesian mapping function that relates reliability index and factor of safety to the probability of liquefaction. Standard penetration test (SPT) N values, engineering properties of the soils and depth of water table were taken from a database of 200 boreholes up to 30 m depth covering an area of 262 km2 in Guwahati city. In the absence of ground motion relation in Guwahati city, a design peak ground acceleration of 0.36 g was used since Guwahati falls in zone V, a high earthquake risk zone, according to the seismic zoning map of India. Liquefaction susceptibility from the methods is presented as maps showing zones of levels of risk of liquefaction. The SPT-based liquefaction evaluation probabilistic procedures have been found to yield significantly different predictions. Comparisons of the methods in the probabilistic approach have shown a difference in the values of probabilities in the same depth. However, on common comparison, the soil layers susceptible to liquefaction in different zones of the city have been identified. To get a further clear picture of soil layers susceptible to liquefaction, one-dimensional equivalent linear ground-response analysis was carried out to determine the peak horizontal ground surface acceleration.

Seismic Site Classification of Recording Stations in Tarai Region of Uttarakhand, from Multiple Approaches

Repeated earthquakes (EQs) are clear indication of alarming seismicity which can be witnessed across Indian subcontinent. Increase in population density with inappropriate construction practice repeatedly rise alarm that in comparison to damage scenarios experienced during previous major to great EQs in India, future catastrophes would be manifold. Performing regional seismic hazard as well as site response studies can possibly help in accurate estimation of probable future seismic scenario. Site class (SC) of EQ recording stations is an important part of both seismic hazard as well as site response analyses. In seismic hazard analysis, suitable attenuation relations are often selected based on comparison of recorded ground motion with proposed ground motion as per selected attenuation relation for the same SC. Thus, unless SC of recorded ground motions is known, suitability of selected attenuation relation cannot be validated. In addition, recent studies suggest that for same soil column, ground motion may amplify at the surface from minimal to very high depending upon input motion characteristics. Thus again, unless SC of recording station is not known, recorded ground motion cannot be considered with confidence as outcrop or base motion for region specific site response studies. In the present work, SC of eight recording stations located in Tarai region of Uttarakhand, India located adjacent to the Himalayan belt and which are part of PESMOS database, are established by three different methods namely; equivalent linear ground response analysis, generalized inversion technique and horizontal to vertical spectral ratio method. Collectively all these three methods suggest same SC for each of the eight recording stations including Roorkee, Rishikesh, Dehradun etc. Further, obtained SC based on the present study is considerably different from available SC as per PESMOS database. However, present findings are matching with recent published work. Obtained results can be very helpful in developing surface seismic hazard using regional ground motion records towards minimizing future EQ induced damages.

Seismic site effect analysis for the city of Tehran using equivalent linear ground response analysis

Equivalent linear ground response analysis is conducted to evaluate seismic site effects in Tehran, Iran. Recorded bedrock motions in acceleration stations within Tehran are scaled based on the peak bedrock acceleration distribution map for a 475-year return period. The seismic responses of sites categorised as class C, based on Building Seismic Safety Council classification system, are obtained using the equivalent linear ground response analysis and available geotechnical and geophysical data. The results of site response analysis are presented in terms of site response spectra and amplification factors, computed in period ranges of 0.1–0.5 s and 0.1–2.5 s. The estimated site response spectra are compared with the suggested spectra in the Iranian Code (Standard No. 2800) and International Building Code (IBC 2015). While the comparison reveals an acceptable agreement between the estimated response spectra and IBC 2015, a significant discrepancy is observed with respect to the Iranian Code.

On the role of stiff soil deposits on seismic ground shaking in western Liguria, Italy: Evidences from past earthquakes and site response

In this work, we analyze the macroseismic fields of the main historical earthquakes occurred in western Liguria (northwestern Italy) in order to identify possible relations between the isoseismal patterns and the local geological setting. Anomalies in the spatial distribution of macroseismic intensities are often attributed to site effects. We observed that, in the region of study, such anomalies are mainly located in areas characterized by outcropping Pliocene soil deposits, mainly made up of stiff silty and marly clays. To investigate the influence of such deposits on ground response, both horizontal-to-vertical spectral ratio measurements and numerical site response analyses were carried out. For all sites analyzed, the spectral ratio curves show marked amplification peaks between 2 and 5Hz. Following such empirical evidence, equivalent linear ground response analyses were performed in order to examine the relation between the measured resonance frequencies and the response of a set of soil columns presenting Pliocene marly-clayey deposits at their top. To this end, a database of geotechnical and geophysical properties, including >50 reference soil profiles, was compiled. This database was used to define alternative numerical models considering three different ranges of thickness of the Pliocene marly-clayey deposits (between 5 and 35m, 30 and 65m, 60 and 105m). Results show marked amplification effects in the ranges 1–3Hz, 2–5Hz, and 3–10Hz depending on the thickness of the investigated soil deposits. These frequency ranges are in agreement with those observed from the experimental measurements, which are therefore proved adequately representative of the resonance frequencies of the Pliocene marly-clayey deposits. Therefore, based on our findings, such deposits can be considered an essential factor in producing the “anomalies” observed in the isoseismal patterns of the macroseismic fields of the historical earthquakes occurred in western Liguria.

One dimensional equivalent linear ground response analysis — A case study of collapsed Margalla Tower in Islamabad during 2005 Muzaffarabad Earthquake

One dimensional equivalent linear ground response analysis was conducted in the Margalla Tower building in Islamabad, which collapsed during 2005 Muzaffarabad Earthquake. The analyses were conducted in DEEPSOIL software, without considering the effect of ground water table. The input subsoil data were selected from laboratory and field tests conducted for the site with bedrock at a depth of 21m as per site condition. The field and laboratory testing data showed that the subsoil beneath the Tower site was silty clay to lean clay according to the unified soil classification system. Four different accelerograms with PGA values of 0.17g, 0.15g, 0.22g and 0.21g, compatible with the earthquake in the target area were applied at the bedrock. The surface response spectra showed that, except the Accelerogram-1 all other three were amplified near the fundamental period of the site. The analyses showed that different PGA values (0.26g, 0.21g, 0.36g and 0.21g) were produced at the surface which can be explained due to the difference in the Fourier amplitude of input accelerograms. Furthermore, the different input accelerograms produced a different shear strain and thus mobilized different shear strengths along the soil profile depth. Finally, the calculated response spectra of accelerograms were compared with the response spectra of Islamabad. The calculated spectral acceleration values were found to be higher than reported by the Building Code of Pakistan (0.16g to 0.24g).

Influences of Local Soil Conditions for Ground Response in Kolkata City During Earthquakes

Ground motion while travelling from the bedrock to the ground surface, causing a change in amplitude and frequency of the seismic waves, and leading to amplification of ground motion have been seen in Kolkata in eastern India. One dimensional equivalent linear ground response analyses for some typical soil sites in Kolkata city of India have been implemented using SHAKE2000 for studying the effects of local soil conditions on the ground motions taking five different input motions having a wide variation in ground motion parameters. It is observed that the maximum horizontal acceleration at the ground surface is amplified by 4.1 times for 2001 Bhuj motion while the Fourier amplification factor and spectral acceleration at 5 % damping is observed to be 10.15 and 3.84 g, respectively at Rajarhat area due to 2011 Sikkim motion. The response spectrum curves obtained are useful for designers for evaluating the safety in designing infrastructures against earthquake forces in Kolkata city, especially in the absence of site specific data.

LOCAL SITE RESPONSE ON SIMULATED STRONG EARTHQUAKE MOTION AT LAEM CHABANG PORT, THAILAND

Laem Chabang port, located in Chonburi province in the upper Gulf of Thailand, is similar to many of the ports around the world. Some areas of Leam Cha bang port were layered by backfill materials which are highly suspected to soil liquefaction phenomena from the moderate to strong earthquakes. After one of the world’s largest earthquakes of December 26th, 2004 (Magnitude 9.1) occurred in the region off the west coast of northern Sumatra, various existing active faults have been reported to have more potential to generate future earthquakes. Among those active faults, Ranong and Khlong Marui fault zone, distributed around the south and the upper Gulf of Thailand, have been evidenced to have more seismic activities than December 2004. The closet distance between Leam Chabang port and the extension of Ranong fault zone to the upper Gulf of Thailand is approximately 180-200 km. Though not too close, it is still probable to generate strong earthquakes. This study, for that reason, aims to investigate the local site responses of the filled area at Laem Chabang port due to afresh seismic Ranong active fault by employing the equivalent linear ground response analysis. The complete strong earthquake motion time history from the Ranong fault would be synthetically generated and inputted as a bedrock motion underneath the site of interest. The simplified analysis of liquefaction potential assessment based on the results from local site response would be additionally adopted to evaluate the liquefaction susceptibility around this site. The simulation results indicated that some backfill soil layers which have the very low SPT N-value were significantly suspected to liquefy under strong earthquake motions.
 
 Keywords: Local site response, synthetic accelerogram, liquefaction potential, backfill, Laem Chabang port