Pub Date : 2024-10-04DOI: 10.1016/j.soildyn.2024.108996
Earthquakes and groundwater are pivotal factors affecting slope stability. However, the majority of previous studies have focused on these factors individually, neglecting their combined effects. Hence, this paper aims to develop a framework using the kinematic approach of limit analysis to investigate the stability of slopes in partially saturated soils under the combined effects of seismic force and pore-water pressure. The pseudo-dynamic method (PDM) was employed to capture the temporal-spatial effect of horizontal and vertical seismic waves. Variations in suction and effective unit weight profiles with moisture content under steady-state unsaturated flow were considered. External rates arising from both static pore-water pressure and earthquake-induced excess pore-water pressure were incorporated into the energy-balance equation. With the aid of gravity increase method (GIM), an explicit expression of safety factor (FS) was derived and optimized using a genetic algorithm (GA). The validity of this approach was verified through a comparison with existing solutions. Parametric analyses were conducted to explore the influence of varying groundwater level, seismic coefficients, suction, three-dimensional effects, excess pore water pressure, unsaturated flow types, and pseudo-dynamic parameters, on the FS and critical sliding surface of slopes in partially saturated slopes. This framework can provide a good reference for the safety design of reservoir slope under the combined effects of earthquakes and groundwater.
{"title":"Stability of slopes in partially saturated soils: Incorporating the combined effects of seismic forces and pore water pressure","authors":"","doi":"10.1016/j.soildyn.2024.108996","DOIUrl":"10.1016/j.soildyn.2024.108996","url":null,"abstract":"<div><div>Earthquakes and groundwater are pivotal factors affecting slope stability. However, the majority of previous studies have focused on these factors individually, neglecting their combined effects. Hence, this paper aims to develop a framework using the kinematic approach of limit analysis to investigate the stability of slopes in partially saturated soils under the combined effects of seismic force and pore-water pressure. The pseudo-dynamic method (PDM) was employed to capture the temporal-spatial effect of horizontal and vertical seismic waves. Variations in suction and effective unit weight profiles with moisture content under steady-state unsaturated flow were considered. External rates arising from both static pore-water pressure and earthquake-induced excess pore-water pressure were incorporated into the energy-balance equation. With the aid of gravity increase method (GIM), an explicit expression of safety factor (FS) was derived and optimized using a genetic algorithm (GA). The validity of this approach was verified through a comparison with existing solutions. Parametric analyses were conducted to explore the influence of varying groundwater level, seismic coefficients, suction, three-dimensional effects, excess pore water pressure, unsaturated flow types, and pseudo-dynamic parameters, on the FS and critical sliding surface of slopes in partially saturated slopes. This framework can provide a good reference for the safety design of reservoir slope under the combined effects of earthquakes and groundwater.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142420092","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 : 2024-10-03DOI: 10.1016/j.soildyn.2024.109004
In recent decades, the concept of special ductility has been commonly used to design reinforced concrete frames to resist strong earthquakes. There are numerous situations where strong earthquakes impose restricted ductility demands, e.g., structures governed by gravity loads or wind loads rather than seismic loads, and frames with geometric properties such that the dimensions prevent formation of plastic hinges at the ends of beams. To evaluate performance of such structures, this study has been conducted and emphasis is placed on intermediate reinforced concrete frames with code-conforming details. Shake table tests are conducted on a 3-story intermediate frame under a sequence of 9 incremental excitation records varying from 0.10 g to 0.60 g, representing minor to severe ground motions. A relatively satisfactory performance is observed: the maximum interstory drift ratio does not exceed 1.57 %, cracks are not localized at the ends of members but distributed along the spans of both beams and columns, and joints remain almost uncracked. To examine the effects of different parameters, a numerical model is developed and verified against the test results. Three essential parameters are considered: seismic event profile, span-to-depth ratio of the beam, and joint aspect ratio. The results show that the effects of different factors may be ranked from highest to lowest as follows: seismic event profile, aspect ratio of the beam-column joint, and span-to-depth ratio of the beam. The numerical analyses show that the frame will not exceed life safety limit under far field excitations and for joint aspect ratios larger than 0.9, but it may reach the threshold of collapse prevention limit under near fault earthquakes. Overall, the study sheds some light on seismic response of RC frames with restricted ductility and provides some indications of their feasibility as well as their limits in high seismic zones.
近几十年来，特殊延性的概念已被普遍用于设计钢筋混凝土框架以抵抗强震。在许多情况下，强震对延性的要求受到限制，例如受重力荷载或风荷载而非地震荷载作用的结构，以及具有几何特性的框架，其尺寸无法在梁端形成塑性铰。为评估此类结构的性能，本研究将重点放在具有符合规范细节的中间钢筋混凝土框架上。在 9 个从 0.10 g 到 0.60 g 的递增激励记录序列下，对一个 3 层的中间框架进行了振动台试验，这些记录代表了从轻微到严重的地面运动。观察到了相对令人满意的性能：最大层间漂移比不超过 1.57%，裂缝不是集中在构件的端部，而是沿着梁和柱的跨度分布，连接处几乎没有裂缝。为了研究不同参数的影响，开发了一个数值模型，并根据测试结果进行了验证。模型考虑了三个基本参数：地震事件剖面、梁的跨深比和连接长宽比。结果表明，不同因素的影响从大到小依次为：地震事件剖面、梁柱连接处的长宽比、梁的跨深比。数值分析表明，在远场激励下和连接长宽比大于 0.9 时，框架不会超过生命安全限值，但在近断层地震下，框架可能会达到防倒塌限值。总之，该研究对延性受限的钢筋混凝土框架的地震响应提供了一些启示，并对其在高地震区的可行性和局限性提供了一些指示。
{"title":"Experimental and numerical investigation of the seismic behavior of reinforced concrete frames with restricted ductility","authors":"","doi":"10.1016/j.soildyn.2024.109004","DOIUrl":"10.1016/j.soildyn.2024.109004","url":null,"abstract":"<div><div>In recent decades, the concept of special ductility has been commonly used to design reinforced concrete frames to resist strong earthquakes. There are numerous situations where strong earthquakes impose restricted ductility demands, e.g., structures governed by gravity loads or wind loads rather than seismic loads, and frames with geometric properties such that the dimensions prevent formation of plastic hinges at the ends of beams. To evaluate performance of such structures, this study has been conducted and emphasis is placed on intermediate reinforced concrete frames with code-conforming details. Shake table tests are conducted on a 3-story intermediate frame under a sequence of 9 incremental excitation records varying from 0.10 g to 0.60 g, representing minor to severe ground motions. A relatively satisfactory performance is observed: the maximum interstory drift ratio does not exceed 1.57 %, cracks are not localized at the ends of members but distributed along the spans of both beams and columns, and joints remain almost uncracked. To examine the effects of different parameters, a numerical model is developed and verified against the test results. Three essential parameters are considered: seismic event profile, span-to-depth ratio of the beam, and joint aspect ratio. The results show that the effects of different factors may be ranked from highest to lowest as follows: seismic event profile, aspect ratio of the beam-column joint, and span-to-depth ratio of the beam. The numerical analyses show that the frame will not exceed life safety limit under far field excitations and for joint aspect ratios larger than 0.9, but it may reach the threshold of collapse prevention limit under near fault earthquakes. Overall, the study sheds some light on seismic response of RC frames with restricted ductility and provides some indications of their feasibility as well as their limits in high seismic zones.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419889","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 : 2024-10-01DOI: 10.1016/j.soildyn.2024.108999
System restoration models are usually adopted for seismic resilience analysis of bridges. However, no analytical process can be found in the existing literature to develop the restoration models for bridges. This paper proposed a new Monte Carlo-based method to derive the generalized system restoration models for ductility highway bridges. In the proposed method, a large number of random samples for ductility bridges were generated by considering uncertainty of structural parameters. The IDA was adopted for producing the damaged bridge samples at different damage states. The repair time of each bridge sample was estimated to generate the actual restoration curve. The Monte Carlo simulations were then adopted to estimate the expected mean functionality curves, which were used to derive the generalized system restoration models by using mathematical functions. Finally, seismic resilience analysis based on the derived generalized system restoration models was conducted and compared with the traditional method to illustrate the effectiveness of the proposed method. It is concluded that the proposed Monte Carlo-based method is an efficient and reliable method for developing the restoration models for ductility highway bridges.
桥梁抗震分析通常采用系统恢复模型。然而，在现有文献中找不到建立桥梁恢复模型的分析过程。本文提出了一种基于蒙特卡罗的新方法来推导延性公路桥梁的广义系统恢复模型。在该方法中，考虑了结构参数的不确定性，生成了大量延性桥梁的随机样本。采用 IDA 方法生成不同损坏状态下的损坏桥梁样本。对每个桥梁样本的修复时间进行估算，生成实际修复曲线。然后采用蒙特卡罗模拟估算预期平均功能曲线，并利用数学函数推导出广义系统修复模型。最后，根据推导出的广义系统恢复模型进行抗震分析，并与传统方法进行比较，以说明所提方法的有效性。结论是，所提出的基于蒙特卡洛的方法是建立延性公路桥梁恢复模型的一种高效、可靠的方法。
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Pub Date : 2024-10-01DOI: 10.1016/j.soildyn.2024.109002
Seismic liquefaction is one of the most devastating natural hazards that can cause significant damage to structures and infrastructure. The liquefaction behaviour is simulated in the finite element code PLAXIS by the UBC3D-PLM constitutive model that is 3-D generalized formulation of the 2-D UBCSAND model developed at the University of British Colombia. The UBC3D-PLM model used in this work was successfully employed in many recent studies, e.g. to evaluate the liquefaction effects on the seismic soil–structure interaction, to assess the dynamic behaviour of earthen embankments built on liquefiable soil and to investigate the seismic performance of offshore foundations. Moreover, UBC3D-PLM model involves many input parameters to model the onset of the liquefaction phenomenon. Therefore, their determination becomes a crucial concern. Previous studies elaborated a specific formulation that requires the corrected Standard Penetration Test (SPT) blow counts as input. However, the Dilatometer Marchetti Test (DMT), compared to the SPT, is more sensitive to several factors that affect the liquefaction resistance such as aging, stress history, overconsolidation and horizontal earth pressure. For this reason, a new parameter selection procedure, which uses the horizontal stress index derived from DMT, was developed in this study.
The new relationships were applied for determining the initial parameters of the UBC3D-PLM model to describe the behavior of several liquefiable deposits located in eastern Sicily (Italy) that experienced destructive earthquakes in the past. For each site, the model was calibrated to the DMT-based liquefaction triggering curve, developed by combining DMT correlations with the current method based on SPT test, by the simulation of cyclic direct simple shear tests (CDSS). Finally, CDSS tests were performed by means of the CDSS device at the Soil Dynamics and Geotechnical Engineering Laboratory of the University “Kore” of Enna (Italy). This allowed to validate the applicability of the proposed procedure in simulating the liquefaction behavior of sandy soils.
{"title":"Calibration of the UBC3D-PLM soil model from Dilatometer Marchetti Test (DMT) for the liquefaction behaviour and cyclic resistance ratio (CRR) of sandy soils","authors":"","doi":"10.1016/j.soildyn.2024.109002","DOIUrl":"10.1016/j.soildyn.2024.109002","url":null,"abstract":"<div><div>Seismic liquefaction is one of the most devastating natural hazards that can cause significant damage to structures and infrastructure. The liquefaction behaviour is simulated in the finite element code PLAXIS by the UBC3D-PLM constitutive model that is 3-D generalized formulation of the 2-D UBCSAND model developed at the University of British Colombia. The UBC3D-PLM model used in this work was successfully employed in many recent studies, e.g. to evaluate the liquefaction effects on the seismic soil–structure interaction, to assess the dynamic behaviour of earthen embankments built on liquefiable soil and to investigate the seismic performance of offshore foundations. Moreover, UBC3D-PLM model involves many input parameters to model the onset of the liquefaction phenomenon. Therefore, their determination becomes a crucial concern. Previous studies elaborated a specific formulation that requires the corrected Standard Penetration Test (SPT) blow counts as input. However, the Dilatometer Marchetti Test (DMT), compared to the SPT, is more sensitive to several factors that affect the liquefaction resistance such as aging, stress history, overconsolidation and horizontal earth pressure. For this reason, a new parameter selection procedure, which uses the horizontal stress index derived from DMT, was developed in this study.</div><div>The new relationships were applied for determining the initial parameters of the UBC3D-PLM model to describe the behavior of several liquefiable deposits located in eastern Sicily (Italy) that experienced destructive earthquakes in the past. For each site, the model was calibrated to the DMT-based liquefaction triggering curve, developed by combining DMT correlations with the current method based on SPT test, by the simulation of cyclic direct simple shear tests (CDSS). Finally, CDSS tests were performed by means of the CDSS device at the Soil Dynamics and Geotechnical Engineering Laboratory of the University “Kore” of Enna (Italy). This allowed to validate the applicability of the proposed procedure in simulating the liquefaction behavior of sandy soils.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419890","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 : 2024-09-30DOI: 10.1016/j.soildyn.2024.108994
Metro tunnels often experience uneven settlement of the soil beneath them during operation, a problem that is especially pronounced in soft soil layers such as silt. This uneven settlement negatively affects the operational safety of subways, prompting engineers to use soil reinforcement techniques to mitigate ground deformation. However, there is a lack of research on the cumulative deformation of reinforced soils under cyclic train loading. In this study, dynamic triaxial tests were conducted to obtain the deformation parameters of silty reinforced soils under cyclic loading. The principal dynamic relationship was summarized, and the effect of loading frequency on soil deformation was analyzed. The results indicated that as the loading frequency increased, the cumulative deformation of the soil decreased. Using the dynamic constitutive relationship derived from the tests, the finite element method was employed to model the interaction system between the load, tunnel, and strata, as well as the dynamic modulus attenuation behavior of the reinforced soil layer. This approach was used to investigate the cumulative deformation characteristics of reinforced soils under cyclic loading. The findings indicated that the dynamic modulus of the reinforced soil decayed rapidly at the beginning of the loading period, leading to an accelerated increase in the cumulative deformation. Additionally, the cumulative deformation was measured at different train speeds, revealing that when the speeds exceeded 80 km/h, the cumulative strain of the soil increased gradually with speed.
地铁隧道在运营过程中，其下方的土壤经常会出现不均匀沉降，这一问题在淤泥等软土层中尤为明显。这种不均匀沉降对地铁的运营安全产生了负面影响，促使工程师使用土壤加固技术来减轻地面变形。然而，目前还缺乏对加固土壤在列车循环荷载作用下累积变形的研究。本研究通过动态三轴试验，获得了淤泥加筋土在循环荷载作用下的变形参数。总结了主要的动力关系，并分析了加载频率对土壤变形的影响。结果表明，随着加载频率的增加，土壤的累积变形量减少。利用试验得出的动力构成关系，采用有限元法模拟了荷载、隧道和地层之间的相互作用系统，以及加筋土层的动模量衰减行为。该方法用于研究加筋土层在循环荷载作用下的累积变形特性。研究结果表明，加筋土壤的动模量在加载期开始时迅速衰减，导致累积变形加速增加。此外，还测量了不同列车速度下的累积变形，结果表明，当列车速度超过 80 km/h 时，土壤的累积应变随速度逐渐增加。
{"title":"Cumulative effects of cyclic train loading on strains in reinforced soils around tunnels","authors":"","doi":"10.1016/j.soildyn.2024.108994","DOIUrl":"10.1016/j.soildyn.2024.108994","url":null,"abstract":"<div><div>Metro tunnels often experience uneven settlement of the soil beneath them during operation, a problem that is especially pronounced in soft soil layers such as silt. This uneven settlement negatively affects the operational safety of subways, prompting engineers to use soil reinforcement techniques to mitigate ground deformation. However, there is a lack of research on the cumulative deformation of reinforced soils under cyclic train loading. In this study, dynamic triaxial tests were conducted to obtain the deformation parameters of silty reinforced soils under cyclic loading. The principal dynamic relationship was summarized, and the effect of loading frequency on soil deformation was analyzed. The results indicated that as the loading frequency increased, the cumulative deformation of the soil decreased. Using the dynamic constitutive relationship derived from the tests, the finite element method was employed to model the interaction system between the load, tunnel, and strata, as well as the dynamic modulus attenuation behavior of the reinforced soil layer. This approach was used to investigate the cumulative deformation characteristics of reinforced soils under cyclic loading. The findings indicated that the dynamic modulus of the reinforced soil decayed rapidly at the beginning of the loading period, leading to an accelerated increase in the cumulative deformation. Additionally, the cumulative deformation was measured at different train speeds, revealing that when the speeds exceeded 80 km/h, the cumulative strain of the soil increased gradually with speed.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359594","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 : 2024-09-28DOI: 10.1016/j.soildyn.2024.108995
Seismic fragility of substation equipment is vital in risk analyses, as well as post-earthquake prediction of failure probabilities of multiple equipment for deciding the inspection order. However, the existing fragility curves of equipment are commonly generated without adequately considering intensity measures (IMs) of ground motions. During the post-earthquake use, they are deemed applicable to any earthquake occurring in the region, which is insufficiently precise. Thus, this paper employs a new method to derive more refined fragility curves for substation equipment based on ground motion classifications. It uses principal component analysis to convert IMs into a small number of principal components (PCs). Taking the PCs as indices, the selected ground motions are clearly categorized into distinct classes using the K-means clustering algorithm. Then, a simulation model of equipment is developed and the time-history dynamic analyses are performed to calculate seismic responses under different classes of ground motions. Finally, the refined fragility curves are derived via multiple stripe analysis for each ground motion class. A 500 kV power transformer is used as a case to implement the method. The results show that a small number of PCs can effectively reflect the multiple ground motion characteristics. Different ground motion classes have distinct distributions of IMs and PCs. There are notable discrepancies in the fragility curves of the power transformer when subjected to different ground motion classes. The significant disparities between the refined and original unclassified fragility curves highlight the importance of considering ground motion classifications.
变电站设备的地震脆性对于风险分析以及震后预测多个设备的故障概率以决定检查顺序至关重要。然而，现有的设备脆性曲线通常是在没有充分考虑地面运动烈度（IMs）的情况下生成的。在震后使用时，它们被认为适用于该地区发生的任何地震，不够精确。因此，本文采用了一种新方法，根据地面运动分类为变电站设备推导出更精细的脆性曲线。它使用主成分分析法将 IMs 转化为少量主成分 (PC)。将 PCs 作为指数，使用 K-means 聚类算法将选定的地面运动明确分为不同的类别。然后，建立设备的模拟模型，并进行时史动态分析，计算不同等级地面运动下的地震响应。最后，通过多条纹分析得出每个地动等级的细化脆性曲线。该方法以 500 kV 电力变压器为例进行实施。结果表明，少量 PCs 就能有效反映多种地面运动特征。不同地动等级的 IM 和 PC 分布不同。电力变压器在不同地动等级下的脆性曲线存在明显差异。改进后的脆性曲线与未分类的原始脆性曲线之间的巨大差异突出表明了考虑地动分类的重要性。
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Pub Date : 2024-09-28DOI: 10.1016/j.soildyn.2024.108993
The high-aspect ratio of structures is usually limited to a small range for base isolation (BI), due to the necessity of ensuring resistance to overturning. This limitation restricts the application of friction pendulum bearings (FPBs) in structures with large high-aspect ratios. This article aims to explore the application of hybrid base isolation and inter-storey isolation (BIISI) in structures with large high-aspect ratio. The theoretical basis of the BIISI was first analyzed in terms of overturning resistance. Subsequently, nonlinear dynamic numerical simulations were conducted on a building with a high aspect ratio to simulate its response subjected to typical pulse-type and non-pulse-type earthquakes. The overturning resistance of the structure and seismic dynamic responses were evaluated. A series of parametric studies were also conducted to investigate the effects of FPB properties, peak ground acceleration (PGA), the friction coefficient ratio and the radius of FPBs between inter-storey isolation storey and base isolation storey on the overturning resistance performance of isolated structures. It is demonstrated that superstructure is meticulously partitioned into two independent sliding structural elements through the BIISI, and it can significantly improve the overturning resistance of buildings with a large high-aspect ratio. PGA and FPB properties show significant differences, but the friction coefficient ratio and the radius of FPBs between the inter-storey isolation storey and base isolation storey show limited influences on the overturning resistance of the structure.
{"title":"Enhancing the overturning resistance capacity of high aspect ratio structure through hybrid base isolation and inter-storey isolation","authors":"","doi":"10.1016/j.soildyn.2024.108993","DOIUrl":"10.1016/j.soildyn.2024.108993","url":null,"abstract":"<div><div>The high-aspect ratio of structures is usually limited to a small range for base isolation (BI), due to the necessity of ensuring resistance to overturning. This limitation restricts the application of friction pendulum bearings (FPBs) in structures with large high-aspect ratios. This article aims to explore the application of hybrid base isolation and inter-storey isolation (BIISI) in structures with large high-aspect ratio. The theoretical basis of the BIISI was first analyzed in terms of overturning resistance. Subsequently, nonlinear dynamic numerical simulations were conducted on a building with a high aspect ratio to simulate its response subjected to typical pulse-type and non-pulse-type earthquakes. The overturning resistance of the structure and seismic dynamic responses were evaluated. A series of parametric studies were also conducted to investigate the effects of FPB properties, peak ground acceleration (PGA), the friction coefficient ratio and the radius of FPBs between inter-storey isolation storey and base isolation storey on the overturning resistance performance of isolated structures. It is demonstrated that superstructure is meticulously partitioned into two independent sliding structural elements through the BIISI, and it can significantly improve the overturning resistance of buildings with a large high-aspect ratio. PGA and FPB properties show significant differences, but the friction coefficient ratio and the radius of FPBs between the inter-storey isolation storey and base isolation storey show limited influences on the overturning resistance of the structure.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359593","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 : 2024-09-28DOI: 10.1016/j.soildyn.2024.108989
The extensive time and computational effort are primary challenges in nonlinear dynamic analysis of tunnel-form concrete systems. These challenges lead engineers to resort to simpler, pushover-based analyses, inherently based on estimating the seismic performance point of the system. Technical literature review indicates that no study has yet rigorously evaluated the accuracy of existing methods for estimating the performance point of tunnel-form systems. To eliminate potential ambiguities, in this study, the seismic performance point of the system under design basis earthquake (with a 475-year return period) has been calculated using three different methods (i.e., displacement coefficient, capacity spectrum, and displacement amplification factor), and compared with the results of accurate nonlinear time-history analysis. In the range of 5-, 7-, and 10-story models studied, the results indicate the inefficiency and insufficiency of the mentioned methods. Investigations reveal that while the capacity spectrum method provides better results, but its process is lengthy, and the displacement coefficient method significantly overestimates the performance point (with more than 80 % error). It was also evident that the displacement amplification factor underestimates the performance point and contradicts the direction of confidence. Based on observations, the use of all three methods for the tunnel-form system requires modifications. The calculated values of effective damping ratio for the tunnel-form system explicitly indicate type A behavior according to the ATC-40 classification. By presenting this parameter in a multi-level format, the shortcomings of both capacity spectrum and displacement coefficient methods are easily addressed. Referring to the results, the calculated value of the displacement amplification factor in the system exceeds the recommended value by the seismic design code, and by adjusting it, satisfactory responses can be obtained in the method based on the displacement amplification factor. Finally, introducing the “probable performance interval” parameter, recommending its use instead of the “performance point” parameter in assessments by pushover analysis is suggested. This parameter is applicable with all three mentioned methods and has been introduced in this study as a desirable factor in compensating for inherent uncertainties related to future earthquakes.
{"title":"Estimation of effective damping ratio for cast-in-place tunnel-form system and evaluation of its role in performance point prediction","authors":"","doi":"10.1016/j.soildyn.2024.108989","DOIUrl":"10.1016/j.soildyn.2024.108989","url":null,"abstract":"<div><div>The extensive time and computational effort are primary challenges in nonlinear dynamic analysis of tunnel-form concrete systems. These challenges lead engineers to resort to simpler, pushover-based analyses, inherently based on estimating the seismic performance point of the system. Technical literature review indicates that no study has yet rigorously evaluated the accuracy of existing methods for estimating the performance point of tunnel-form systems. To eliminate potential ambiguities, in this study, the seismic performance point of the system under design basis earthquake (with a 475-year return period) has been calculated using three different methods (i.e., displacement coefficient, capacity spectrum, and displacement amplification factor), and compared with the results of accurate nonlinear time-history analysis. In the range of 5-, 7-, and 10-story models studied, the results indicate the inefficiency and insufficiency of the mentioned methods. Investigations reveal that while the capacity spectrum method provides better results, but its process is lengthy, and the displacement coefficient method significantly overestimates the performance point (with more than 80 % error). It was also evident that the displacement amplification factor underestimates the performance point and contradicts the direction of confidence. Based on observations, the use of all three methods for the tunnel-form system requires modifications. The calculated values of effective damping ratio for the tunnel-form system explicitly indicate type A behavior according to the ATC-40 classification. By presenting this parameter in a multi-level format, the shortcomings of both capacity spectrum and displacement coefficient methods are easily addressed. Referring to the results, the calculated value of the displacement amplification factor in the system exceeds the recommended value by the seismic design code, and by adjusting it, satisfactory responses can be obtained in the method based on the displacement amplification factor. Finally, introducing the “probable performance interval” parameter, recommending its use instead of the “performance point” parameter in assessments by pushover analysis is suggested. This parameter is applicable with all three mentioned methods and has been introduced in this study as a desirable factor in compensating for inherent uncertainties related to future earthquakes.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-27DOI: 10.1016/j.soildyn.2024.108997
This paper presents a novel practical multiscale analysis (MSA) method for simulating local damages in large reinforced concrete (RC) structures during seismic events. Traditional techniques like the finite element (FE) method often struggle to balance computational costs with detailed simulation. The proposed method facilitates sequential local refinement from macroscopic to mesoscopic scales of RC structures, focusing strategically on critical areas prone to damage and cracking. Key features include: (1) 'Correction forces' enable integration and collaboration among models of different refinement levels, keeping models unchanged (i.e., without additions, deletions, or further refinement of elements), streamlining analysis and independent implementation across methods, scales, and platforms. (2) A smart replacement strategy ensures smooth transitions and prevents abrupt force changes between models at different refinement levels. (3) A ‘training process’ before performing the replacement and a semi-explicit method guarantee the accuracy and efficiency of the MSA method. (4) Parallel and distributed computing is seamlessly applied, significantly accelerating the analysis at each level. Implemented in the open-source software OpenSees, this method is illustrated through three examples that efficiently capture both the macroscopic mechanical responses and detailed local damage behaviors. This approach provides a valuable tool for the refined analysis of large-scale RC structures.
{"title":"A practical multiscale analysis for nonlinear RC structures using a smart substructure replacement strategy","authors":"","doi":"10.1016/j.soildyn.2024.108997","DOIUrl":"10.1016/j.soildyn.2024.108997","url":null,"abstract":"<div><div>This paper presents a novel practical multiscale analysis (MSA) method for simulating local damages in large reinforced concrete (RC) structures during seismic events. Traditional techniques like the finite element (FE) method often struggle to balance computational costs with detailed simulation. The proposed method facilitates sequential local refinement from macroscopic to mesoscopic scales of RC structures, focusing strategically on critical areas prone to damage and cracking. Key features include: (1) 'Correction forces' enable integration and collaboration among models of different refinement levels, keeping models unchanged (i.e., without additions, deletions, or further refinement of elements), streamlining analysis and independent implementation across methods, scales, and platforms. (2) A smart replacement strategy ensures smooth transitions and prevents abrupt force changes between models at different refinement levels. (3) A ‘training process’ before performing the replacement and a semi-explicit method guarantee the accuracy and efficiency of the MSA method. (4) Parallel and distributed computing is seamlessly applied, significantly accelerating the analysis at each level. Implemented in the open-source software OpenSees, this method is illustrated through three examples that efficiently capture both the macroscopic mechanical responses and detailed local damage behaviors. This approach provides a valuable tool for the refined analysis of large-scale RC structures.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328023","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 : 2024-09-26DOI: 10.1016/j.soildyn.2024.108982
The lateral natural frequency of an offshore wind turbine (OWT) is a crucial factor to consider in the design of OWT foundations. Eighty percent of currently installed OWTs are mounted on monopile foundations, which are connected to the superstructure via a transition piece (TP). To explore the differences in natural frequencies between grouted connection (GC) and TP-less designs, this study incorporates a transition piece into the calculation model of the OWT system. Based on the Timoshenko beam theory and transfer matrix method, the characteristic equations of the lateral natural frequency of the OWT are derived. The study found that the effect of the transition piece on the natural frequency is strongly influenced by the OWT type and the soil stiffness, and the influence of transition piece on different order natural frequencies is different for the same OWT. For the NREL offshore 5-MW baseline wind turbine, the TP-less model reduces the first natural frequency of the OWT by 1.31 % and elevates the second and third natural frequencies by 11.88 % and 2.72 %, respectively, compared to the GC model. The increase in soil shear wave velocity amplifies the influence of the transition piece on the first and third natural frequencies, while weakening its influence on the second natural frequency.
{"title":"Effect of the transition piece on the natural frequencies of monopile-supported offshore wind turbines","authors":"","doi":"10.1016/j.soildyn.2024.108982","DOIUrl":"10.1016/j.soildyn.2024.108982","url":null,"abstract":"<div><div>The lateral natural frequency of an offshore wind turbine (OWT) is a crucial factor to consider in the design of OWT foundations. Eighty percent of currently installed OWTs are mounted on monopile foundations, which are connected to the superstructure via a transition piece (TP). To explore the differences in natural frequencies between grouted connection (GC) and TP-less designs, this study incorporates a transition piece into the calculation model of the OWT system. Based on the Timoshenko beam theory and transfer matrix method, the characteristic equations of the lateral natural frequency of the OWT are derived. The study found that the effect of the transition piece on the natural frequency is strongly influenced by the OWT type and the soil stiffness, and the influence of transition piece on different order natural frequencies is different for the same OWT. For the NREL offshore 5-MW baseline wind turbine, the TP-less model reduces the first natural frequency of the OWT by 1.31 % and elevates the second and third natural frequencies by 11.88 % and 2.72 %, respectively, compared to the GC model. The increase in soil shear wave velocity amplifies the influence of the transition piece on the first and third natural frequencies, while weakening its influence on the second natural frequency.</div></div>","PeriodicalId":49502,"journal":{"name":"Soil Dynamics and Earthquake Engineering","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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