Pub Date : 2023-10-19DOI: 10.1177/87552930231203989
Nathan Girmay, Alan Poulos, Eduardo Miranda
Until recently, the orientation of maximum horizontal spectral response was generally believed to not have a predominant orientation at rupture distances greater than 5 km. However, a recent study found that the orientation of maximum spectral response for strike-slip earthquakes in the NGA-West2 database tends to occur close to the epicentral transverse orientation, that is, an orientation perpendicular to a line connecting the epicenter to the station. This article investigates directionality in the 6 February 2023 Türkiye doublet earthquakes ( M w 7.8 and 7.5) with strike-slip faulting. The orientation of the maximum response of 5%-damped linear elastic oscillators was studied. The spatial distribution of the level of polarization, which in this article refers to the amount of directionality, and intensities at specific orientations were also studied. The maximum spectral response was found to occur systematically close to the epicentral transverse orientation, consistent with previous observations for other strike-slip earthquakes. For the M w 7.8 event where the location of maximum slip was relatively far from the epicenter, it was found that the orientation of maximum spectral response is, on average, closer to the maximum slip transverse orientation (i.e. perpendicular to a line connecting the station to the surface projection of the point of maximum slip) when compared to the epicentral transverse orientation over most period ranges. This suggests that the maximum slip transverse orientation may be a better estimator for determining the orientation of maximum spectral response in large-magnitude strike-slip earthquakes, although further study using more events is warranted. Polarized motions were observed over large geographical areas, and the orientation of maximum spectral response was found to be close to the epicentral or maximum slip transverse for Joyner–Boore distances up to the farthest studied (400 km). These findings further support the case for the development of orientation-dependent ground motion models for strike-slip earthquakes.
{"title":"Directionality and polarization of response spectral ordinates in the 2023 Kahramanmaras, Türkiye earthquake doublet","authors":"Nathan Girmay, Alan Poulos, Eduardo Miranda","doi":"10.1177/87552930231203989","DOIUrl":"https://doi.org/10.1177/87552930231203989","url":null,"abstract":"Until recently, the orientation of maximum horizontal spectral response was generally believed to not have a predominant orientation at rupture distances greater than 5 km. However, a recent study found that the orientation of maximum spectral response for strike-slip earthquakes in the NGA-West2 database tends to occur close to the epicentral transverse orientation, that is, an orientation perpendicular to a line connecting the epicenter to the station. This article investigates directionality in the 6 February 2023 Türkiye doublet earthquakes ( M w 7.8 and 7.5) with strike-slip faulting. The orientation of the maximum response of 5%-damped linear elastic oscillators was studied. The spatial distribution of the level of polarization, which in this article refers to the amount of directionality, and intensities at specific orientations were also studied. The maximum spectral response was found to occur systematically close to the epicentral transverse orientation, consistent with previous observations for other strike-slip earthquakes. For the M w 7.8 event where the location of maximum slip was relatively far from the epicenter, it was found that the orientation of maximum spectral response is, on average, closer to the maximum slip transverse orientation (i.e. perpendicular to a line connecting the station to the surface projection of the point of maximum slip) when compared to the epicentral transverse orientation over most period ranges. This suggests that the maximum slip transverse orientation may be a better estimator for determining the orientation of maximum spectral response in large-magnitude strike-slip earthquakes, although further study using more events is warranted. Polarized motions were observed over large geographical areas, and the orientation of maximum spectral response was found to be close to the epicentral or maximum slip transverse for Joyner–Boore distances up to the farthest studied (400 km). These findings further support the case for the development of orientation-dependent ground motion models for strike-slip earthquakes.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135730542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-17DOI: 10.1177/87552930231194550
Alexander Chansky, Laurie Gaskins Baise, Babak Moaveni
Liquefaction can be a significant contributor to loss due to earthquakes as observed during the Canterbury earthquake sequence or the 1995 Kobe earthquake. Geospatial liquefaction models can be used to estimate liquefaction extent after an earthquake but do not estimate liquefaction damage or impact. This article presents a liquefaction loss database for the United States and event-level fragility functions (EFFs) using aggregate liquefaction hazard measures (LHMs) derived from geospatial liquefaction models. The liquefaction loss database for the United States is developed by sampling earthquakes with Magnitude > 5.0 between the years of 1964 and 2019 in the continental United States and Alaska. Within this sample of 42 earthquakes, 11 resulted in liquefaction loss. Estimates were characterized by the type of infrastructure (e.g. transportation, utilities, and buildings) and the subcategory (e.g. for buildings: residential, commercial, and public), and then loss was estimated using the 2018-equivalent US dollar amount. When possible, loss estimates were obtained directly from the literature. Within this sample of 42 earthquakes, 6 events resulted in estimated monetary losses from liquefaction damage greater than 1% of the total event loss, including one with liquefaction damage greater than 10%. Using estimates for aggregate liquefaction hazard and population exposure derived from geospatial liquefaction models as LHMs, EFFs are presented using cost-based damage state (DS) thresholds in the United States. The fragility functions also include confidence intervals representing the uncertainty in probabilities of exceeding DS thresholds. Aggregate liquefaction hazard was found to be a preferred LHM for liquefaction loss, especially when evaluating transportation and building loss. Aggregate population exposure was found to be a better LHM for utilities. In addition, a second set of EFFs is presented using an expanded international dataset and DSs which are assigned relative to overall earthquake damage rather than cost-based DSs.
{"title":"National liquefaction loss database and event-level fragility functions","authors":"Alexander Chansky, Laurie Gaskins Baise, Babak Moaveni","doi":"10.1177/87552930231194550","DOIUrl":"https://doi.org/10.1177/87552930231194550","url":null,"abstract":"Liquefaction can be a significant contributor to loss due to earthquakes as observed during the Canterbury earthquake sequence or the 1995 Kobe earthquake. Geospatial liquefaction models can be used to estimate liquefaction extent after an earthquake but do not estimate liquefaction damage or impact. This article presents a liquefaction loss database for the United States and event-level fragility functions (EFFs) using aggregate liquefaction hazard measures (LHMs) derived from geospatial liquefaction models. The liquefaction loss database for the United States is developed by sampling earthquakes with Magnitude > 5.0 between the years of 1964 and 2019 in the continental United States and Alaska. Within this sample of 42 earthquakes, 11 resulted in liquefaction loss. Estimates were characterized by the type of infrastructure (e.g. transportation, utilities, and buildings) and the subcategory (e.g. for buildings: residential, commercial, and public), and then loss was estimated using the 2018-equivalent US dollar amount. When possible, loss estimates were obtained directly from the literature. Within this sample of 42 earthquakes, 6 events resulted in estimated monetary losses from liquefaction damage greater than 1% of the total event loss, including one with liquefaction damage greater than 10%. Using estimates for aggregate liquefaction hazard and population exposure derived from geospatial liquefaction models as LHMs, EFFs are presented using cost-based damage state (DS) thresholds in the United States. The fragility functions also include confidence intervals representing the uncertainty in probabilities of exceeding DS thresholds. Aggregate liquefaction hazard was found to be a preferred LHM for liquefaction loss, especially when evaluating transportation and building loss. Aggregate population exposure was found to be a better LHM for utilities. In addition, a second set of EFFs is presented using an expanded international dataset and DSs which are assigned relative to overall earthquake damage rather than cost-based DSs.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135995900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-04DOI: 10.1177/87552930231202449
Henry V Burton, Sebastian Galicia Madero, Awa Kologo, Laxman Dahal, Sahar Derakhshan
Disparities in seismic risk mitigation programs can lead to uneven impacts during an earthquake and an increased burden on socially vulnerable and underserved communities. This article examines the extent to which the distribution of cripple wall retrofits in residential buildings (primarily one- and two-family units) located within the City of Los Angeles (LA), varies based on the sociodemographics of the affected populations. Utilizing multiple data sources including the LA Department of Building and Safety (LADBS) and LA Open Data Portal (LAOPD), a combination of spatial and statistical approaches are implemented at the regional, neighborhood, and census-tract scales. At each scale, the number of retrofitted buildings normalized by the total number of pre-1980 one- and two-family residential buildings (or retrofit rate) is the primary dependent variable. The effect of the Earthquake Brace and Bolt (EBB) program on the disparities in the retrofit rate distribution is also assessed. Despite having relatively older one- and two-family residential buildings, those neighborhoods with the highest representation of Black and Hispanic households are generally associated with lower retrofit rates. We also found that the neighborhoods with the lowest median income have retrofit rates that are less than the average for the entire City of LA. The rate among Black, Hispanic, and low-income households was found to increase significantly after the EBB program was instituted in 2013, suggesting that the initiative may have served as a mechanism to reduce the demographic and economic disparities in the cripple wall retrofits. However, to date, the average retrofit rate in the ten neighborhoods with the highest representation of Hispanic households is roughly one-third that of the rest of LA City.
{"title":"Sociodemographic analysis of unbraced unbolted cripple wall retrofits in the City of Los Angeles","authors":"Henry V Burton, Sebastian Galicia Madero, Awa Kologo, Laxman Dahal, Sahar Derakhshan","doi":"10.1177/87552930231202449","DOIUrl":"https://doi.org/10.1177/87552930231202449","url":null,"abstract":"Disparities in seismic risk mitigation programs can lead to uneven impacts during an earthquake and an increased burden on socially vulnerable and underserved communities. This article examines the extent to which the distribution of cripple wall retrofits in residential buildings (primarily one- and two-family units) located within the City of Los Angeles (LA), varies based on the sociodemographics of the affected populations. Utilizing multiple data sources including the LA Department of Building and Safety (LADBS) and LA Open Data Portal (LAOPD), a combination of spatial and statistical approaches are implemented at the regional, neighborhood, and census-tract scales. At each scale, the number of retrofitted buildings normalized by the total number of pre-1980 one- and two-family residential buildings (or retrofit rate) is the primary dependent variable. The effect of the Earthquake Brace and Bolt (EBB) program on the disparities in the retrofit rate distribution is also assessed. Despite having relatively older one- and two-family residential buildings, those neighborhoods with the highest representation of Black and Hispanic households are generally associated with lower retrofit rates. We also found that the neighborhoods with the lowest median income have retrofit rates that are less than the average for the entire City of LA. The rate among Black, Hispanic, and low-income households was found to increase significantly after the EBB program was instituted in 2013, suggesting that the initiative may have served as a mechanism to reduce the demographic and economic disparities in the cripple wall retrofits. However, to date, the average retrofit rate in the ten neighborhoods with the highest representation of Hispanic households is roughly one-third that of the rest of LA City.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135591650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-03DOI: 10.1177/87552930231197376
Alireza Javanbakht, Sheri Molnar, Abouzar Sadrekarimi, Hadi Ghofrani
Paleo-liquefaction features of sand dykes and sand blows were identified in the 1990s at multiple host sediments in the Fraser River delta in southern British Columbia all younger than 3500 BP. These paleo-liquefaction sites could be linked to Cascadia subduction earthquakes. Empirical magnitude-bound relationships are often used to estimate paleo-earthquake magnitudes. To determine the lower bound magnitude of Cascadia interface earthquakes that could have generated the paleo-liquefaction features, we use ground motion prediction equations for interface earthquakes from the sixth Canadian seismic hazard model of the 2020 National Building Code of Canada. We estimate the minimum M and its peak ground acceleration ( a max ) of an interface earthquake required to initiate paleo-liquefaction in the study region. Starting with three full-rupture deterministic scenarios of varying source-to-site distance, we determine the minimum M required from Cascadia subduction zone interface mega-thrust earthquakes to induce liquefaction in the Fraser River delta spans 8.0–8.9 with a corresponding a max range of 0.09–0.13 g. We also perform a back-calculation paleo-liquefaction analysis in a probabilistic framework to incorporate aleatory uncertainties (cone penetration resistance, groundwater table, and a max ) and epistemic uncertainties (liquefaction simplified model) via the Monte Carlo simulation. The developed probabilistic methodology is also applicable to a forward liquefaction assessment and other liquefaction sites globally. The median M from this probabilistic paleo-liquefaction for the four investigated sites lies between 8.8 and 9.0. Our probabilistic results also reveal that Cascadia interface earthquakes with M > 8.9 lead to a 31%–57% probability of liquefaction triggering in the Fraser River delta. In addition, we developed deterministic and probabilistic magnitude-bound curves specific to Cascadia interface earthquakes and representative site class E conditions. These curves provide more accurate magnitude estimations for predicting seismic-induced liquefaction from Cascadia interface earthquakes for sites in the Pacific Northwest than empirical bound curves.
{"title":"Estimation of historical earthquake-induced liquefaction in Fraser River delta using NBCC 2020 GMPEs in deterministic and probabilistic frameworks","authors":"Alireza Javanbakht, Sheri Molnar, Abouzar Sadrekarimi, Hadi Ghofrani","doi":"10.1177/87552930231197376","DOIUrl":"https://doi.org/10.1177/87552930231197376","url":null,"abstract":"Paleo-liquefaction features of sand dykes and sand blows were identified in the 1990s at multiple host sediments in the Fraser River delta in southern British Columbia all younger than 3500 BP. These paleo-liquefaction sites could be linked to Cascadia subduction earthquakes. Empirical magnitude-bound relationships are often used to estimate paleo-earthquake magnitudes. To determine the lower bound magnitude of Cascadia interface earthquakes that could have generated the paleo-liquefaction features, we use ground motion prediction equations for interface earthquakes from the sixth Canadian seismic hazard model of the 2020 National Building Code of Canada. We estimate the minimum M and its peak ground acceleration ( a max ) of an interface earthquake required to initiate paleo-liquefaction in the study region. Starting with three full-rupture deterministic scenarios of varying source-to-site distance, we determine the minimum M required from Cascadia subduction zone interface mega-thrust earthquakes to induce liquefaction in the Fraser River delta spans 8.0–8.9 with a corresponding a max range of 0.09–0.13 g. We also perform a back-calculation paleo-liquefaction analysis in a probabilistic framework to incorporate aleatory uncertainties (cone penetration resistance, groundwater table, and a max ) and epistemic uncertainties (liquefaction simplified model) via the Monte Carlo simulation. The developed probabilistic methodology is also applicable to a forward liquefaction assessment and other liquefaction sites globally. The median M from this probabilistic paleo-liquefaction for the four investigated sites lies between 8.8 and 9.0. Our probabilistic results also reveal that Cascadia interface earthquakes with M > 8.9 lead to a 31%–57% probability of liquefaction triggering in the Fraser River delta. In addition, we developed deterministic and probabilistic magnitude-bound curves specific to Cascadia interface earthquakes and representative site class E conditions. These curves provide more accurate magnitude estimations for predicting seismic-induced liquefaction from Cascadia interface earthquakes for sites in the Pacific Northwest than empirical bound curves.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135743621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-28DOI: 10.1177/87552930231195113
Michael Dupuis, Claudio Schill, Robin Lee, Brendon Bradley
High-quality earthquake ground-motion records are required for various applications in engineering and seismology; however, quality assessment of ground-motion records is time-consuming if done manually and poorly handled by automation with conventional mathematical functions. Machine learning is well suited to this problem, and a supervised deep-learning-based model was developed to estimate the quality of all types of ground-motion records through training on 1096 example records from earthquakes in New Zealand, which is an active tectonic environment with crustal and subduction earthquakes. The model estimates a quality and minimum usable frequency for each record component and can handle one-, two-, or three-component records. The estimations were found to match manually labeled test data well, and the model was able to accurately replicate manual quality classifications from other published studies based on the requirements of three different engineering applications. The component-level quality and minimum usable frequency estimations provide flexibility to assess record quality based on diverse requirements and make the model useful for a range of potential applications. We apply the model to enable automated record classification for 43,398 ground motions from GeoNet as part of the development of a new curated ground-motion database for New Zealand.
{"title":"A deep-learning-based model for quality assessment of earthquake-induced ground-motion records","authors":"Michael Dupuis, Claudio Schill, Robin Lee, Brendon Bradley","doi":"10.1177/87552930231195113","DOIUrl":"https://doi.org/10.1177/87552930231195113","url":null,"abstract":"High-quality earthquake ground-motion records are required for various applications in engineering and seismology; however, quality assessment of ground-motion records is time-consuming if done manually and poorly handled by automation with conventional mathematical functions. Machine learning is well suited to this problem, and a supervised deep-learning-based model was developed to estimate the quality of all types of ground-motion records through training on 1096 example records from earthquakes in New Zealand, which is an active tectonic environment with crustal and subduction earthquakes. The model estimates a quality and minimum usable frequency for each record component and can handle one-, two-, or three-component records. The estimations were found to match manually labeled test data well, and the model was able to accurately replicate manual quality classifications from other published studies based on the requirements of three different engineering applications. The component-level quality and minimum usable frequency estimations provide flexibility to assess record quality based on diverse requirements and make the model useful for a range of potential applications. We apply the model to enable automated record classification for 43,398 ground motions from GeoNet as part of the development of a new curated ground-motion database for New Zealand.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135425006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-27DOI: 10.1177/87552930231190902
Jean-Robert Pierre
On 12 January 2010, the M7.0 Haiti earthquake caused infrastructure damage induced by extensive soil liquefaction and foundation failure in the Port-au-Prince International Seaport and Léogâne Plain. This study re-examines the soil liquefaction effects of the main shock and aftershock events by exploring the existing studies on calcareous sands, reviewing the phenomenon of liquefaction in the Caribbean Islands, and associating them within the seismic history of the Greater and Lesser Antilles. Due to the geomorphology of the Islands, urban development has typically been concentrated along the coast, in locations vulnerable to soil liquefaction. This study demonstrates that the liquefaction that occurred at sites in the M7.0 Haiti event was triggered by the main shock even at low peak ground accelerations (PGAs), the first aftershock effects were significant, and soil liquefaction was not rare in the Antilles. It identifies the elements that characterize historical cases of soil liquefaction caused by earthquakes in the Caribbean Islands. In addition, it points out the characteristics and findings of paleoliquefaction and paleoseismicity investigations conducted in the Caribbean region. Investigations and studies on the calcareous sand liquefaction and paleoseismology are essential to improve the seismic hazard and risk assessment of the Caribbean Islands. The existence of a large number of studies making reference to this topic highlights its significance.
{"title":"A review of soil liquefaction in the Caribbean Greater and Lesser Antilles in reconsidering the ground motion effect of the M7.0 2010 Haiti earthquake in the Port-au-Prince Seaport and Léogâne Plain","authors":"Jean-Robert Pierre","doi":"10.1177/87552930231190902","DOIUrl":"https://doi.org/10.1177/87552930231190902","url":null,"abstract":"On 12 January 2010, the M7.0 Haiti earthquake caused infrastructure damage induced by extensive soil liquefaction and foundation failure in the Port-au-Prince International Seaport and Léogâne Plain. This study re-examines the soil liquefaction effects of the main shock and aftershock events by exploring the existing studies on calcareous sands, reviewing the phenomenon of liquefaction in the Caribbean Islands, and associating them within the seismic history of the Greater and Lesser Antilles. Due to the geomorphology of the Islands, urban development has typically been concentrated along the coast, in locations vulnerable to soil liquefaction. This study demonstrates that the liquefaction that occurred at sites in the M7.0 Haiti event was triggered by the main shock even at low peak ground accelerations (PGAs), the first aftershock effects were significant, and soil liquefaction was not rare in the Antilles. It identifies the elements that characterize historical cases of soil liquefaction caused by earthquakes in the Caribbean Islands. In addition, it points out the characteristics and findings of paleoliquefaction and paleoseismicity investigations conducted in the Caribbean region. Investigations and studies on the calcareous sand liquefaction and paleoseismology are essential to improve the seismic hazard and risk assessment of the Caribbean Islands. The existence of a large number of studies making reference to this topic highlights its significance.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135579514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-26DOI: 10.1177/87552930231200031
Ozan Cem Celik, Erhan Budak, Halûk Sucuoğlu
A 253 m tall office building in Istanbul with a parallelogram footprint, which has 62 stories in total, 54 tower stories above and 8 podium stories below grade, was monitored using 92 channels of accelerometers deployed on 20 different floors for about 4 days. The structural system of the building consists of reinforced concrete (RC) core shear walls with peripheral composite columns and two-story tall RC outriggers between floors 29 and 31. First 12 natural vibration periods and mode shapes of the building together with the modal directions for the translational modes were identified from the ambient vibration records. These dynamic properties were reproduced with the three-dimensional finite element model developed using gross section properties for all structural members without a need for model updating. The fundamental period of the building at the time of testing, 5.3 s, is expected to lengthen to 5.9 s and 7.8 s upon cracking in structural members for the prescribed service-level and design-level evaluations, respectively, in line with the recent performance-based design guidelines for tall buildings. Damping ratios for the first six vibration modes, with median values of 0.6% and coefficients of variation in the order of 0.3–0.4, were identified through statistical analysis using the random decrement technique. The simulated peak floor accelerations, when the building was subjected to the 2019 M w 5.8 Marmara Sea earthquake ground motions recorded in the vicinity of the building, showed that ASCE 7-16 in-structure floor acceleration amplifications are exceeded at the lower floors but not reached at the upper floors.
伊斯坦布尔一座253米高的平行四边形办公大楼，总共有62层，上面有54层塔楼，下面有8层裙楼，使用部署在20个不同楼层的92个加速度计通道进行了大约4天的监测。该建筑的结构体系由钢筋混凝土(RC)核心剪力墙和外围组合柱以及29层和31层之间的两层高的RC伸出体组成。从环境振动记录中确定了建筑物的前12个自振周期、振型和平移模态方向。这些动态特性是用三维有限元模型再现的，该模型使用所有结构成员的总截面特性而无需更新模型。在测试时，建筑物的基本寿命为5.3秒，预计在规定的服务水平和设计水平评估中，结构构件开裂后，建筑物的基本寿命将分别延长至5.9秒和7.8秒，以符合最近的高层建筑基于性能的设计指南。采用随机减量法进行统计分析，确定了前6种振型的阻尼比，中位数为0.6%，变异系数为0.3 ~ 0.4。当建筑物受到建筑物附近记录的2019年M w 5.8马尔马拉海地震地面运动时，模拟的峰值楼层加速度表明，较低楼层超过了ASCE 7-16结构内楼层加速度放大，但上层没有达到。
{"title":"Vibration-based temporary monitoring of a 253 m tall skew-plan building in Istanbul","authors":"Ozan Cem Celik, Erhan Budak, Halûk Sucuoğlu","doi":"10.1177/87552930231200031","DOIUrl":"https://doi.org/10.1177/87552930231200031","url":null,"abstract":"A 253 m tall office building in Istanbul with a parallelogram footprint, which has 62 stories in total, 54 tower stories above and 8 podium stories below grade, was monitored using 92 channels of accelerometers deployed on 20 different floors for about 4 days. The structural system of the building consists of reinforced concrete (RC) core shear walls with peripheral composite columns and two-story tall RC outriggers between floors 29 and 31. First 12 natural vibration periods and mode shapes of the building together with the modal directions for the translational modes were identified from the ambient vibration records. These dynamic properties were reproduced with the three-dimensional finite element model developed using gross section properties for all structural members without a need for model updating. The fundamental period of the building at the time of testing, 5.3 s, is expected to lengthen to 5.9 s and 7.8 s upon cracking in structural members for the prescribed service-level and design-level evaluations, respectively, in line with the recent performance-based design guidelines for tall buildings. Damping ratios for the first six vibration modes, with median values of 0.6% and coefficients of variation in the order of 0.3–0.4, were identified through statistical analysis using the random decrement technique. The simulated peak floor accelerations, when the building was subjected to the 2019 M w 5.8 Marmara Sea earthquake ground motions recorded in the vicinity of the building, showed that ASCE 7-16 in-structure floor acceleration amplifications are exceeded at the lower floors but not reached at the upper floors.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134961109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.1177/87552930231182164
Maha Kenawy, David McCallen, Arben Pitarka
Earthquake-induced ground shaking near rupturing faults is highly sensitive to the rupture characteristics, seismic wave propagation patterns and site conditions, and field recordings of near-fault shaking are relatively sparse. These challenges complicate the assessment of the seismic performance of near-fault structures. A common approach to representing near-fault ground motion in engineering analysis is to explicitly consider and select records with strong directivity pulses (pulse records). We use three-dimensional high-resolution physics-based earthquake simulations to test this approach in the context of scenario-based ground motion record selection, and to study the important characteristics of near-fault ground shaking. We highlight the deficiencies associated with classifying near-fault simulated records as “pulse” or “non-pulse,” based on the presence of a single dominating pulse in the velocity time history. We show that this approach is inadequate for characterizing near-fault shaking on soft soils which can be dominated by both forward rupture directivity and basin amplification effects. We conduct ground motion selection experiments for the analysis of near-fault structures with and without explicit classification of the pulse features in the records, and evaluate the bias in the predicted structural demands. We find that the maximum interstory drift demands on building structures imposed by unscaled site-specific simulated ground motion records selected based on relevant spectral shape features are not sensitive to the classification of records as pulse/non-pulse. Therefore, with regard to predicting the maximum interstory drifts in near-fault buildings, we do not find justification for the binary pulse classification of near-fault records.
{"title":"Characteristics and selection of near-fault simulated earthquake ground motions for nonlinear analysis of buildings","authors":"Maha Kenawy, David McCallen, Arben Pitarka","doi":"10.1177/87552930231182164","DOIUrl":"https://doi.org/10.1177/87552930231182164","url":null,"abstract":"Earthquake-induced ground shaking near rupturing faults is highly sensitive to the rupture characteristics, seismic wave propagation patterns and site conditions, and field recordings of near-fault shaking are relatively sparse. These challenges complicate the assessment of the seismic performance of near-fault structures. A common approach to representing near-fault ground motion in engineering analysis is to explicitly consider and select records with strong directivity pulses (pulse records). We use three-dimensional high-resolution physics-based earthquake simulations to test this approach in the context of scenario-based ground motion record selection, and to study the important characteristics of near-fault ground shaking. We highlight the deficiencies associated with classifying near-fault simulated records as “pulse” or “non-pulse,” based on the presence of a single dominating pulse in the velocity time history. We show that this approach is inadequate for characterizing near-fault shaking on soft soils which can be dominated by both forward rupture directivity and basin amplification effects. We conduct ground motion selection experiments for the analysis of near-fault structures with and without explicit classification of the pulse features in the records, and evaluate the bias in the predicted structural demands. We find that the maximum interstory drift demands on building structures imposed by unscaled site-specific simulated ground motion records selected based on relevant spectral shape features are not sensitive to the classification of records as pulse/non-pulse. Therefore, with regard to predicting the maximum interstory drifts in near-fault buildings, we do not find justification for the binary pulse classification of near-fault records.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135864075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.1177/87552930231197626
Pengfei Wang, Zehan Liu, Scott J Brandenberg, Paolo Zimmaro, Jonathan P Stewart
Conventional probabilistic seismic hazard analysis (PSHA) is often repeated at many locations independently to develop uniform hazard maps. However, such maps are unsuitable for assessing risk to spatially distributed infrastructure because no single event will produce uniform hazard shaking intensities across a broad region. A robust but computationally expensive approach is to analyze spatially distributed infrastructure systems separately for every event considered in the seismic source characterization model used in the PSHA. This approach may not be practical when many scenario events are considered. An alternative is to select a manageable event subset that, in aggregate, approximately matches the hazard for single or multiple ground motion intensity measures across the spatially distributed system preserving contributions of different magnitudes and distances to the PSHA. We present a flexible and efficient regression-based method that meets these requirements using point-based PSHA results as inputs. The approach is illustrated with a case study of distributed infrastructure in southern California. We demonstrate the efficiency of the method by comparing it to a mixed-integer linear optimization method from the literature.
{"title":"Regression-based scenario earthquake selection for regional hazard-consistent risk assessments","authors":"Pengfei Wang, Zehan Liu, Scott J Brandenberg, Paolo Zimmaro, Jonathan P Stewart","doi":"10.1177/87552930231197626","DOIUrl":"https://doi.org/10.1177/87552930231197626","url":null,"abstract":"Conventional probabilistic seismic hazard analysis (PSHA) is often repeated at many locations independently to develop uniform hazard maps. However, such maps are unsuitable for assessing risk to spatially distributed infrastructure because no single event will produce uniform hazard shaking intensities across a broad region. A robust but computationally expensive approach is to analyze spatially distributed infrastructure systems separately for every event considered in the seismic source characterization model used in the PSHA. This approach may not be practical when many scenario events are considered. An alternative is to select a manageable event subset that, in aggregate, approximately matches the hazard for single or multiple ground motion intensity measures across the spatially distributed system preserving contributions of different magnitudes and distances to the PSHA. We present a flexible and efficient regression-based method that meets these requirements using point-based PSHA results as inputs. The approach is illustrated with a case study of distributed infrastructure in southern California. We demonstrate the efficiency of the method by comparing it to a mixed-integer linear optimization method from the literature.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-23DOI: 10.1177/87552930231197669
Negar Mohammadgholibeyki, Maria Jose Echeverria, Amir Safiey, Dustin Cook, Maria Koliou, Abbie B. Liel
Damage from past earthquakes has significantly hampered post-earthquake building function, threatening community resilience, and motivating consideration of functional recovery in building design and assessment. This study examines whether it is feasible to achieve functional recovery in retrofit of existing reinforced concrete buildings, focusing on seven buildings retrofit with various motivations and strategies. The seismic response of these buildings was nonlinearly simulated, and functional recovery was probabilistically assessed. The results show that retrofits targeting life safety may or may not achieve functional recovery goals. Achieving functional recovery depends especially on the reduction of drift demands and collapse probability. However, the acceleration increase associated with many retrofits can increase function loss due to the criticality of acceleration-sensitive nonstructural components if such components are not retrofitted. We also examine other performance metrics, that is, economic losses and immediate occupancy limits of ASCE/SEI 41, showing that these provide imprecise, and in the case of the immediate occupancy conservative, proxies for functional recovery.
{"title":"Assessing the feasibility of achieving functional recovery goals through seismic retrofit of existing reinforced concrete buildings","authors":"Negar Mohammadgholibeyki, Maria Jose Echeverria, Amir Safiey, Dustin Cook, Maria Koliou, Abbie B. Liel","doi":"10.1177/87552930231197669","DOIUrl":"https://doi.org/10.1177/87552930231197669","url":null,"abstract":"Damage from past earthquakes has significantly hampered post-earthquake building function, threatening community resilience, and motivating consideration of functional recovery in building design and assessment. This study examines whether it is feasible to achieve functional recovery in retrofit of existing reinforced concrete buildings, focusing on seven buildings retrofit with various motivations and strategies. The seismic response of these buildings was nonlinearly simulated, and functional recovery was probabilistically assessed. The results show that retrofits targeting life safety may or may not achieve functional recovery goals. Achieving functional recovery depends especially on the reduction of drift demands and collapse probability. However, the acceleration increase associated with many retrofits can increase function loss due to the criticality of acceleration-sensitive nonstructural components if such components are not retrofitted. We also examine other performance metrics, that is, economic losses and immediate occupancy limits of ASCE/SEI 41, showing that these provide imprecise, and in the case of the immediate occupancy conservative, proxies for functional recovery.","PeriodicalId":11392,"journal":{"name":"Earthquake Spectra","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135959407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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