Pub Date : 2014-01-01DOI: 10.4018/IJGEE.2014010105
C. Ramanna, G. Dodagoudar
The present work is intended to study the effect of variation of seismic area source zone on hazard value for Chennai, India. In the conventional Cornell-McGuire approach to probabilistic seismic hazard analysis, the seismic activity rate for an area source is most often determined using the Gutenberg-Richter (G-R) recurrence law. The seismic area is delineated using geology, geography and/or seismotectonic characteristics of the region. However if the area lies in a distributed seismicity region, the delineation into different area zones introduces subjectivity. The impact of the areal extent of seismic area zone on the final hazard value is studied using two approaches - the conventional Cornell-McGuire and zone-free approaches. It is observed that in the conventional Cornell-McGuire approach, the peak ground acceleration decreases when the area source zone is increased while maintaining all other seismicity parameters same. In the kernel method, the PGA remained unchanged though the seismic source area is increased. This is due to the fact that in the kernel method, the seismic activity rate is a spatially varying parameter unlike the seismic activity rate determined from the G-R recurrence law, which assumes a homogeneous distribution of the activity rate for each of the area source zones. The uniform hazard spectra are obtained for various return periods by both the approaches. It is observed that in the Cornell-McGuire approach, the variation in the extent of seismic source area has little effect on longer return periods as compared to the smaller return periods.
{"title":"Impact Analysis of Seismic Source Area Extent on Hazard Estimate for Chennai City","authors":"C. Ramanna, G. Dodagoudar","doi":"10.4018/IJGEE.2014010105","DOIUrl":"https://doi.org/10.4018/IJGEE.2014010105","url":null,"abstract":"The present work is intended to study the effect of variation of seismic area source zone on hazard value for Chennai, India. In the conventional Cornell-McGuire approach to probabilistic seismic hazard analysis, the seismic activity rate for an area source is most often determined using the Gutenberg-Richter (G-R) recurrence law. The seismic area is delineated using geology, geography and/or seismotectonic characteristics of the region. However if the area lies in a distributed seismicity region, the delineation into different area zones introduces subjectivity. The impact of the areal extent of seismic area zone on the final hazard value is studied using two approaches - the conventional Cornell-McGuire and zone-free approaches. It is observed that in the conventional Cornell-McGuire approach, the peak ground acceleration decreases when the area source zone is increased while maintaining all other seismicity parameters same. In the kernel method, the PGA remained unchanged though the seismic source area is increased. This is due to the fact that in the kernel method, the seismic activity rate is a spatially varying parameter unlike the seismic activity rate determined from the G-R recurrence law, which assumes a homogeneous distribution of the activity rate for each of the area source zones. The uniform hazard spectra are obtained for various return periods by both the approaches. It is observed that in the Cornell-McGuire approach, the variation in the extent of seismic source area has little effect on longer return periods as compared to the smaller return periods.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78238351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.4018/IJGEE.2014010101
A. Shiuly, R. Sahu, S. Mandal
This paper presents the ground motion amplification factors at different time period bands and fundamental time period of soft sedimentary deposit in densely populated Kolkata city for seismic microzonation. 1D seismic wave propagation technique SHAKE2000 is used for ground motion amplifications at different locations of Kolkata city. Fundamental time period (), amplification at fundamental time period, average amplification and amplification at different frequency band for soil columns are computed and corresponding contours are plotted for variety of end users. The study reveals that Kolkata may suffer severe damage even due to moderate earthquake.
{"title":"Effect of Soil on Ground Motion Amplification of Kolkata City","authors":"A. Shiuly, R. Sahu, S. Mandal","doi":"10.4018/IJGEE.2014010101","DOIUrl":"https://doi.org/10.4018/IJGEE.2014010101","url":null,"abstract":"This paper presents the ground motion amplification factors at different time period bands and fundamental time period of soft sedimentary deposit in densely populated Kolkata city for seismic microzonation. 1D seismic wave propagation technique SHAKE2000 is used for ground motion amplifications at different locations of Kolkata city. Fundamental time period (), amplification at fundamental time period, average amplification and amplification at different frequency band for soil columns are computed and corresponding contours are plotted for variety of end users. The study reveals that Kolkata may suffer severe damage even due to moderate earthquake.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83261368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.4018/IJGEE.2014010102
C. Ramanna, G. Dodagoudar
The most important parameter in the kernel density estimator is the bandwidth or spread or window width. The bandwidth of the kernel density estimator, which follows the power law, is determined using the nearest neighborhood technique for the earthquake catalog which is divided into bins. For reliable hazard estimates, the magnitude bins used in developing the power law and estimating the spatial activity rate density function should be the same. It is important that consistency be maintained between the earthquake epicenters used in determining the bandwidth and the epicenters to which the bandwidth is applied subsequently. In this paper, the effect of epicenter data inconsistency on hazard estimates for various return periods for Chennai is evaluated. Two methods of binning are used, one in which the epicenters used in deriving the bandwidth is in line with the epicenters used in arriving at the spatial activity rate and the other where the epicenters used in deriving the bandwidth are just grouped by dividing the catalogue into equal bins. Seismic hazard estimations are compared using these two approaches of forming the magnitude bins for Chennai, Tamil Nadu, India. The peak ground acceleration (PGA) values obtained from Binning Methods 1 and 2 for 475 years return period are 0.0955g and 0.0802g respectively. The difference in PGA and peak spectral acceleration (PSA) from the two binning methods ranges from 20 to 10% with respect to Binning Method 1 for the return periods of 72 to 2475 years.
{"title":"Effect of Epicenter Data Inconsistency in Determining Bandwidth and its Subsequent Use in Hazard Analysis for Chennai Using Kernel Smoothing Approach","authors":"C. Ramanna, G. Dodagoudar","doi":"10.4018/IJGEE.2014010102","DOIUrl":"https://doi.org/10.4018/IJGEE.2014010102","url":null,"abstract":"The most important parameter in the kernel density estimator is the bandwidth or spread or window width. The bandwidth of the kernel density estimator, which follows the power law, is determined using the nearest neighborhood technique for the earthquake catalog which is divided into bins. For reliable hazard estimates, the magnitude bins used in developing the power law and estimating the spatial activity rate density function should be the same. It is important that consistency be maintained between the earthquake epicenters used in determining the bandwidth and the epicenters to which the bandwidth is applied subsequently. In this paper, the effect of epicenter data inconsistency on hazard estimates for various return periods for Chennai is evaluated. Two methods of binning are used, one in which the epicenters used in deriving the bandwidth is in line with the epicenters used in arriving at the spatial activity rate and the other where the epicenters used in deriving the bandwidth are just grouped by dividing the catalogue into equal bins. Seismic hazard estimations are compared using these two approaches of forming the magnitude bins for Chennai, Tamil Nadu, India. The peak ground acceleration (PGA) values obtained from Binning Methods 1 and 2 for 475 years return period are 0.0955g and 0.0802g respectively. The difference in PGA and peak spectral acceleration (PSA) from the two binning methods ranges from 20 to 10% with respect to Binning Method 1 for the return periods of 72 to 2475 years.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72385407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.4018/IJGEE.2014010104
S. Venkatesan, A. Rajabifard, N. Lam, E. Gad, H. Goldsworthy, Ged Griffin
Disaster management is widely recognised as a complex task. Despite well-established techniques, each disaster continues to frustrate the government and the community. A number of issues and challenges have been reported in the literature following a disaster. These include: a lack of awareness, authoritative support and direction, preparation and planning; ineffective response, ineffective communications and miscommunications, inadequate recovery and policy vacuum besides many other factors. Developing effective disaster management strategies to combat the known issues should also consider emerging drivers of change such as globalisation, climate change, and technological development, social construct of communities, global finance and education. In addition, fundamental hazard modelling techniques and real time modelling of a disaster cannot be ignored as they are central to the accuracy of information required during pre and post disasters. In recent times spatial information has been considered as the fourth element of decision making. Further the need to develop adaptive capacities and empower communities is also well stated. Despite the recognition of such complex issues, requirements, and increased knowledge, the pace of development seems to be inadequate. This is mainly due to the lack of an approach that can integrate the myriad of issues with the roles and responsibilities of stakeholders such as governments, practitioners and the community. Recognising the need to develop an informed decision making process, this paper reviews the challenges and issues based on current practice. A review of relevant new knowledge that can improve current practice is also undertaken. Based on these reviews it is identified that a spatially enabled platform can be developed to overcome the aforementioned issues related to disaster management. A preliminary roadmap in which the `stakeholder position' is considered as the vital point of integration is presented. It is anticipated that the roadmap will provide governments with the direction needed for future planning, policy development, implementation and control. Future developmental needs of the platform are also presented.
{"title":"A syncretic approach towards a meta-integrative platform for effective disaster management","authors":"S. Venkatesan, A. Rajabifard, N. Lam, E. Gad, H. Goldsworthy, Ged Griffin","doi":"10.4018/IJGEE.2014010104","DOIUrl":"https://doi.org/10.4018/IJGEE.2014010104","url":null,"abstract":"Disaster management is widely recognised as a complex task. Despite well-established techniques, each disaster continues to frustrate the government and the community. A number of issues and challenges have been reported in the literature following a disaster. These include: a lack of awareness, authoritative support and direction, preparation and planning; ineffective response, ineffective communications and miscommunications, inadequate recovery and policy vacuum besides many other factors. Developing effective disaster management strategies to combat the known issues should also consider emerging drivers of change such as globalisation, climate change, and technological development, social construct of communities, global finance and education. In addition, fundamental hazard modelling techniques and real time modelling of a disaster cannot be ignored as they are central to the accuracy of information required during pre and post disasters. In recent times spatial information has been considered as the fourth element of decision making. Further the need to develop adaptive capacities and empower communities is also well stated. Despite the recognition of such complex issues, requirements, and increased knowledge, the pace of development seems to be inadequate. This is mainly due to the lack of an approach that can integrate the myriad of issues with the roles and responsibilities of stakeholders such as governments, practitioners and the community. Recognising the need to develop an informed decision making process, this paper reviews the challenges and issues based on current practice. A review of relevant new knowledge that can improve current practice is also undertaken. Based on these reviews it is identified that a spatially enabled platform can be developed to overcome the aforementioned issues related to disaster management. A preliminary roadmap in which the `stakeholder position' is considered as the vital point of integration is presented. It is anticipated that the roadmap will provide governments with the direction needed for future planning, policy development, implementation and control. Future developmental needs of the platform are also presented.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76831209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.4018/IJGEE.2014010103
Sima Ghosh, Arijit Saha
In the present analysis, using the horizontal slice method and D'Alembert's principle, a methodology is suggested to calculate the pseudo-dynamic active earth pressure on battered face retaining wall supporting cohesive-frictional backfill. Results are presented in tabular form. The analysis provides a curvilinear rupture surface depending on the wall-backfill parameters. Effects of a wide range of variation of parameters like wall inclination angle (a), wall friction angle (d), soil friction angle (F), shear wave velocity (Vs), primary wave velocity (Vp), horizontal and vertical seismic accelerations (kh, kv) along with horizontal shear and vertical loads and non-linear wedge angle on the seismic active earth pressure coefficient have been studied.
{"title":"Pseudo-Dynamic Active Earth Pressure on Battered Face Retaining Wall Supporting c-Φ Backfill Considering Curvilinear Rupture Surface","authors":"Sima Ghosh, Arijit Saha","doi":"10.4018/IJGEE.2014010103","DOIUrl":"https://doi.org/10.4018/IJGEE.2014010103","url":null,"abstract":"In the present analysis, using the horizontal slice method and D'Alembert's principle, a methodology is suggested to calculate the pseudo-dynamic active earth pressure on battered face retaining wall supporting cohesive-frictional backfill. Results are presented in tabular form. The analysis provides a curvilinear rupture surface depending on the wall-backfill parameters. Effects of a wide range of variation of parameters like wall inclination angle (a), wall friction angle (d), soil friction angle (F), shear wave velocity (Vs), primary wave velocity (Vp), horizontal and vertical seismic accelerations (kh, kv) along with horizontal shear and vertical loads and non-linear wedge angle on the seismic active earth pressure coefficient have been studied.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74035890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-07-01DOI: 10.4018/IJGEE.2013070102
R. Jakka, A. Shiuly, R. Das
This paper presents the liquefaction potential of densely populated Kolkata city, which is situated on the world's largest delta island with very soft and thick alluvial soil deposits. Due to presence of soft alluvium deposits at shallow depths, soil resistance against liquefaction is expected to be less. Additionally, large thickness of soil layers may amplify the ground shaking resulting in high seismic demand on the soil. Here in this study, variation of factor of safety against liquefaction is evaluated with depth at different locations in Kolkota city. The study founds striking results that the Kolkata city soils are less prone to liquefaction even though there is significant ground amplification due to presence of thick soil deposits.
{"title":"Liquefaction Potential for Kolkata City","authors":"R. Jakka, A. Shiuly, R. Das","doi":"10.4018/IJGEE.2013070102","DOIUrl":"https://doi.org/10.4018/IJGEE.2013070102","url":null,"abstract":"This paper presents the liquefaction potential of densely populated Kolkata city, which is situated on the world's largest delta island with very soft and thick alluvial soil deposits. Due to presence of soft alluvium deposits at shallow depths, soil resistance against liquefaction is expected to be less. Additionally, large thickness of soil layers may amplify the ground shaking resulting in high seismic demand on the soil. Here in this study, variation of factor of safety against liquefaction is evaluated with depth at different locations in Kolkota city. The study founds striking results that the Kolkata city soils are less prone to liquefaction even though there is significant ground amplification due to presence of thick soil deposits.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80560836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-07-01DOI: 10.4018/IJGEE.2013070104
Arjun Sil, T. Sitharam
In this paper, the study addressed how the local geology and soil condition influences on incoming ground motion. Subsurface Geotechnical (SPT) and geophysical (MASW) data in 27 locations at Agartala city have been obtained and used to estimate the surface level response. The vulnerable seismic source (Sylhet fault) has been identified based on deterministic seismic hazard analysis (DSHA). The stochastic point source seismological model has been used to generate synthetic ground motion at 27 locations where MASW tests were conducted. The site response analyses have been performed using SHAKE2000.The results are presented in the form of contour maps in terms of PGA, amplification factor (AF) and spectral accelerations of periods (0.20sec, 1.0sec). The highest amplifications (2 to 3) were observed in the intermediate periods between 0.20 to 1.0sec ranges. However, the mean response spectrum has also been developed for both the rock and ground surface that has mean PGA 0.285g at rock and 0.35g at the surface. Further, the IS code and NEHRP provisions were compared with the mean surface level response spectrum. The IS code provision overestimates the mean response spectrum for all the periods except the periods from 0.26-0.42 sec. Based on the present study, the average shear wave velocity (Vs30=236±52 m/s) of Agartala actually falls a site class-D category (180 m/s
{"title":"Site Response Evaluation of Agartala City Using Geophysical and Geotechnical Data","authors":"Arjun Sil, T. Sitharam","doi":"10.4018/IJGEE.2013070104","DOIUrl":"https://doi.org/10.4018/IJGEE.2013070104","url":null,"abstract":"In this paper, the study addressed how the local geology and soil condition influences on incoming ground motion. Subsurface Geotechnical (SPT) and geophysical (MASW) data in 27 locations at Agartala city have been obtained and used to estimate the surface level response. The vulnerable seismic source (Sylhet fault) has been identified based on deterministic seismic hazard analysis (DSHA). The stochastic point source seismological model has been used to generate synthetic ground motion at 27 locations where MASW tests were conducted. The site response analyses have been performed using SHAKE2000.The results are presented in the form of contour maps in terms of PGA, amplification factor (AF) and spectral accelerations of periods (0.20sec, 1.0sec). The highest amplifications (2 to 3) were observed in the intermediate periods between 0.20 to 1.0sec ranges. However, the mean response spectrum has also been developed for both the rock and ground surface that has mean PGA 0.285g at rock and 0.35g at the surface. Further, the IS code and NEHRP provisions were compared with the mean surface level response spectrum. The IS code provision overestimates the mean response spectrum for all the periods except the periods from 0.26-0.42 sec. Based on the present study, the average shear wave velocity (Vs30=236±52 m/s) of Agartala actually falls a site class-D category (180 m/s","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79048455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-07-01DOI: 10.4018/IJGEE.2013070103
Abdelwahab Mourad Khellafi, Z. Harichane, H. Afra, Amina Sadouki
On May 21st, 2003, the north Algeria was stricken by a 6.8 magnitude earthquake which was felt over a distance of 250 km from the epicenter, which is localized in Mediterranean Sea at 10 km from the coast. During this event, several ground accelerations were recorded by the instrumentation network of the National Center of Applied Research in Earthquake Engineering (CGS). The records analysis revealed an important difference in peak ground acceleration (PGA) between two close stations (0.58g and 0.33g, respectively, in East-West direction) at about 20 km from the earthquake epicenter. Also, two other record stations, located in the Mitidja basin, at about 29 km and 86 km from the earthquake epicenter, respectively, showed a high level of acceleration: PGAs of 0.54g and 0.16g. So, the authors attempt in this paper to analyze these records through the characteristics of strong ground motions, the effects of different parameters such as damping ratios, soil conditions and epicentral distance on normalized response spectra. Also, the quantification of site effects during this earthquake is analyzed. Then, the authors compare the near-field mean response spectra obtained during this earthquake with the Algerian seismic design spectra (RPA99 – 2003 version) and with two other well-known design spectra: Eurocode 8 and UBC97 in order to contribute to the future revision of RPA99.
{"title":"A Case Study of Accelerometric Records Analysis of May 21st, 2003, Boumerdes (Algeria) Earthquake","authors":"Abdelwahab Mourad Khellafi, Z. Harichane, H. Afra, Amina Sadouki","doi":"10.4018/IJGEE.2013070103","DOIUrl":"https://doi.org/10.4018/IJGEE.2013070103","url":null,"abstract":"On May 21st, 2003, the north Algeria was stricken by a 6.8 magnitude earthquake which was felt over a distance of 250 km from the epicenter, which is localized in Mediterranean Sea at 10 km from the coast. During this event, several ground accelerations were recorded by the instrumentation network of the National Center of Applied Research in Earthquake Engineering (CGS). The records analysis revealed an important difference in peak ground acceleration (PGA) between two close stations (0.58g and 0.33g, respectively, in East-West direction) at about 20 km from the earthquake epicenter. Also, two other record stations, located in the Mitidja basin, at about 29 km and 86 km from the earthquake epicenter, respectively, showed a high level of acceleration: PGAs of 0.54g and 0.16g. So, the authors attempt in this paper to analyze these records through the characteristics of strong ground motions, the effects of different parameters such as damping ratios, soil conditions and epicentral distance on normalized response spectra. Also, the quantification of site effects during this earthquake is analyzed. Then, the authors compare the near-field mean response spectra obtained during this earthquake with the Algerian seismic design spectra (RPA99 – 2003 version) and with two other well-known design spectra: Eurocode 8 and UBC97 in order to contribute to the future revision of RPA99.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81627434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-07-01DOI: 10.4018/IJGEE.2013070101
A. Brennan, A. Klar, S. Madabhushi
Earthquake accelerations cause many problems for structures on the ground surface. Ground improvement may be carried out to reduce or otherwise modify shear waves before they reach the structures, which can be more cost-effective than structural strengthening. This paper investigates the response of a simple structure whose foundation has been completely enclosed by a layer of soft material. Physical and numerical models of this are presented. Based on these, it is seen that not only is linear acceleration significantly attenuated by such a system, but the foundation-structure system is able to rock in antiphase to the translational motion to further reduce acceleration. A simple two degree of freedom spring model is presented that can match the behaviour of the more sophisticated models. Recorded strong motion data applied to this simple model suggests that improvement can be achieved provided caisson modes and structural modes occur at different frequencies.
{"title":"Mitigation of Seismic Accelerations by Soft Caissons","authors":"A. Brennan, A. Klar, S. Madabhushi","doi":"10.4018/IJGEE.2013070101","DOIUrl":"https://doi.org/10.4018/IJGEE.2013070101","url":null,"abstract":"Earthquake accelerations cause many problems for structures on the ground surface. Ground improvement may be carried out to reduce or otherwise modify shear waves before they reach the structures, which can be more cost-effective than structural strengthening. This paper investigates the response of a simple structure whose foundation has been completely enclosed by a layer of soft material. Physical and numerical models of this are presented. Based on these, it is seen that not only is linear acceleration significantly attenuated by such a system, but the foundation-structure system is able to rock in antiphase to the translational motion to further reduce acceleration. A simple two degree of freedom spring model is presented that can match the behaviour of the more sophisticated models. Recorded strong motion data applied to this simple model suggests that improvement can be achieved provided caisson modes and structural modes occur at different frequencies.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2013-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77416202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, one dimensional equivalent–linear ground response analyses were performed for some typical sites in the Guwahati city, India. Six bore locations covering about 250 km2 area of the city were considered for the analyses. As the strong motion significantly influences the ground response, seven different recorded ground motions, varying in magnitude (6.1 to 8.1) and other ground motion parameters, were adopted. Seismic site analyses were carried out for all layers of borelogs using all the seven earthquakes. Results are presented in terms of surface acceleration histories, strain and shear stress ratio variation, response spectrum, Fourier amplitude ratio versus frequency. The results indicate that accelerations were amplified the most at the surface level. The range of peak ground acceleration (PGA) values obtained at the ground surface is about 0.2 g to 0.79 for a range of PGA considered at bedrock level (rigid half space at bottom of borelog) of 0.1 g to 0.34 g. The Fourier amplifications of ground motion at surface are in the range of 4.14 – 8.99 for a frequency band of 1.75 Hz to 3.13 Hz. The maximum spectral acceleration at six locations varies in the range of 1.0 g – 4.71 g for all the seven earthquakes. The study clearly demonstrated the role for site effect and the type of ground motion on the ground response. For a given earthquake motion, amplification factors at surface level change by almost about 20% to 70% depending on local site conditions.
{"title":"Seismic Ground Response Analysis of Some Typical Sites of Guwahati City","authors":"S. Kumar, A. Krishna","doi":"10.4018/JGEE.2013010106","DOIUrl":"https://doi.org/10.4018/JGEE.2013010106","url":null,"abstract":"In this study, one dimensional equivalent–linear ground response analyses were performed for some typical sites in the Guwahati city, India. Six bore locations covering about 250 km2 area of the city were considered for the analyses. As the strong motion significantly influences the ground response, seven different recorded ground motions, varying in magnitude (6.1 to 8.1) and other ground motion parameters, were adopted. Seismic site analyses were carried out for all layers of borelogs using all the seven earthquakes. Results are presented in terms of surface acceleration histories, strain and shear stress ratio variation, response spectrum, Fourier amplitude ratio versus frequency. The results indicate that accelerations were amplified the most at the surface level. The range of peak ground acceleration (PGA) values obtained at the ground surface is about 0.2 g to 0.79 for a range of PGA considered at bedrock level (rigid half space at bottom of borelog) of 0.1 g to 0.34 g. The Fourier amplifications of ground motion at surface are in the range of 4.14 – 8.99 for a frequency band of 1.75 Hz to 3.13 Hz. The maximum spectral acceleration at six locations varies in the range of 1.0 g – 4.71 g for all the seven earthquakes. The study clearly demonstrated the role for site effect and the type of ground motion on the ground response. For a given earthquake motion, amplification factors at surface level change by almost about 20% to 70% depending on local site conditions.","PeriodicalId":42473,"journal":{"name":"International Journal of Geotechnical Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2013-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77066480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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