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Sachan Ajanta - One of the best experts on this subject based on the ideXlab platform.
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Matric suction, swelling and collapsible characteristics of unsaturated expansive soils
2018Co-Authors: Pandya Saloni, Sachan AjantaAbstract:Unsaturated expansive soils are recognized as one of the most problematic soils owing to its swelling-shrinkage characteristics. The presence of such soils in highway/railway embankments, slopes and earthen dam sites manifests various critical issues during and after the construction of structures. The current research aims on the evaluation of the suction, swelling and collapsible characteristics of four expansive soils possessing different expansiveness and mineralogical composition. A series of constant volume swell pressure, double-oedometer and incontact filter paper tests were performed on four different expansive soils to acquire swelling pressure, Collapse Potential and matric suction at different degree of saturation. Swelling pressure, Collapse Potential and matric suction of all expansive soils degraded substantially with increment in the degree of saturation. The results revealed significant impact of magnitude of matric suction on volumetric deformation (swell and Collapse) behavior of expansive soils. Swelling and Collapse Potential were observed to be higher for the expansive soils with larger matric suction. Higher matric suction governed the water intake within interlayer spacing of the Montmorillonite mineral present in expansive soil, which contributed to higher crystalline swelling response. Larger Collapse Potential indicated development of larger localized deformations within the soil mass owing to higher matric suction.by Saloni Pandya and Ajanta Sacha
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Variation of Collapse Potential and stiffness degradation with matric suction of compacted unsaturated cohesive soil
Taylor & Francis, 2017Co-Authors: Pandya Saloni, Sachan AjantaAbstract:Collapse of soil skeleton due to variation in its loading and boundary conditions impacts the strength and stability of soil in its unsaturated state. The present study is focused on the influence of matric suction on collapsible behaviour and stiffness degradation of compacted unsaturated cohesive soil. Collapse characteristic of unsaturated soil is assessed under sudden inundation and varying vertical stress application. A series of dynamic triaxial, double oedometer and filter paper tests were conducted on unsaturated Ahmedabad cohesive soil under as-compacted conditions at varying dry density and water content to determine cyclic degradation index (?), Collapse Potential and matric suction (ua uw), respectively. Significant influence of matric suction was observed on Collapse Potential and stiffness degradation of unsaturated cohesive soil. Larger Collapse Potential at higher matric suction clarified the meta-stable state of compacted unsaturated cohesive soil under dry conditions. Cyclic degradation index (?) with number of loading cycles was found to be decreasing with increase in matric suction representing brittle nature of soil possessing higher matric suction signifying soil skeleton to be highly volatile and unsafe under dynamic loading conditions.by Saloni Pandya and Ajanta Sacha
Ajanta Sachan - One of the best experts on this subject based on the ideXlab platform.
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variation of Collapse Potential and stiffness degradation with matric suction of compacted unsaturated cohesive soil
International Journal of Geotechnical Engineering, 2020Co-Authors: Saloni Pandya, Ajanta SachanAbstract:Collapse of soil skeleton due to variation in its loading and boundary conditions impacts the strength and stability of soil in its unsaturated state. The present study is focused on the influence ...
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Relationship of Collapse Potential and Swell Pressure with Suction of Unsaturated Expansive Soil
Proceedings of GeoShanghai 2018 International Conference: Multi-physics Processes in Soil Mechanics and Advances in Geotechnical Testing, 2018Co-Authors: Saloni Pandya, Narendra Sarswat, Ajanta SachanAbstract:Expansive soils in unsaturated state cause problems to several civil engineering structures due to its transient volume change behavior. Present study is focused on evaluation of swelling and collapsible characteristics of unsaturated compacted expansive soil specimens and their relationship with suction. A series of volume change swell pressure tests and double oedometer tests were conducted at varying degree of saturation to evaluate swelling pressure and Collapse Potential of Bharuch expansive soil respectively. Suction measurements of soil were conducted by employing WP4C Dew point Potentiameter at different water content. Presence of higher negative pore pressure induced higher swelling pressure, which was observed to vary exponentially with total suction. Results indicated significant influence of soil suction on soil fabric arrangement, which substantially affected Collapse behaviour of expansive soil. Collapse Potential of Bharuch expansive soil was observed to decrease with increase in water content due to reduction in suction of soil indicating metastable state of soil at lower degree of saturation.
Pandya Saloni - One of the best experts on this subject based on the ideXlab platform.
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Matric suction, swelling and collapsible characteristics of unsaturated expansive soils
2018Co-Authors: Pandya Saloni, Sachan AjantaAbstract:Unsaturated expansive soils are recognized as one of the most problematic soils owing to its swelling-shrinkage characteristics. The presence of such soils in highway/railway embankments, slopes and earthen dam sites manifests various critical issues during and after the construction of structures. The current research aims on the evaluation of the suction, swelling and collapsible characteristics of four expansive soils possessing different expansiveness and mineralogical composition. A series of constant volume swell pressure, double-oedometer and incontact filter paper tests were performed on four different expansive soils to acquire swelling pressure, Collapse Potential and matric suction at different degree of saturation. Swelling pressure, Collapse Potential and matric suction of all expansive soils degraded substantially with increment in the degree of saturation. The results revealed significant impact of magnitude of matric suction on volumetric deformation (swell and Collapse) behavior of expansive soils. Swelling and Collapse Potential were observed to be higher for the expansive soils with larger matric suction. Higher matric suction governed the water intake within interlayer spacing of the Montmorillonite mineral present in expansive soil, which contributed to higher crystalline swelling response. Larger Collapse Potential indicated development of larger localized deformations within the soil mass owing to higher matric suction.by Saloni Pandya and Ajanta Sacha
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Variation of Collapse Potential and stiffness degradation with matric suction of compacted unsaturated cohesive soil
Taylor & Francis, 2017Co-Authors: Pandya Saloni, Sachan AjantaAbstract:Collapse of soil skeleton due to variation in its loading and boundary conditions impacts the strength and stability of soil in its unsaturated state. The present study is focused on the influence of matric suction on collapsible behaviour and stiffness degradation of compacted unsaturated cohesive soil. Collapse characteristic of unsaturated soil is assessed under sudden inundation and varying vertical stress application. A series of dynamic triaxial, double oedometer and filter paper tests were conducted on unsaturated Ahmedabad cohesive soil under as-compacted conditions at varying dry density and water content to determine cyclic degradation index (?), Collapse Potential and matric suction (ua uw), respectively. Significant influence of matric suction was observed on Collapse Potential and stiffness degradation of unsaturated cohesive soil. Larger Collapse Potential at higher matric suction clarified the meta-stable state of compacted unsaturated cohesive soil under dry conditions. Cyclic degradation index (?) with number of loading cycles was found to be decreasing with increase in matric suction representing brittle nature of soil possessing higher matric suction signifying soil skeleton to be highly volatile and unsafe under dynamic loading conditions.by Saloni Pandya and Ajanta Sacha
Saloni Pandya - One of the best experts on this subject based on the ideXlab platform.
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variation of Collapse Potential and stiffness degradation with matric suction of compacted unsaturated cohesive soil
International Journal of Geotechnical Engineering, 2020Co-Authors: Saloni Pandya, Ajanta SachanAbstract:Collapse of soil skeleton due to variation in its loading and boundary conditions impacts the strength and stability of soil in its unsaturated state. The present study is focused on the influence ...
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Relationship of Collapse Potential and Swell Pressure with Suction of Unsaturated Expansive Soil
Proceedings of GeoShanghai 2018 International Conference: Multi-physics Processes in Soil Mechanics and Advances in Geotechnical Testing, 2018Co-Authors: Saloni Pandya, Narendra Sarswat, Ajanta SachanAbstract:Expansive soils in unsaturated state cause problems to several civil engineering structures due to its transient volume change behavior. Present study is focused on evaluation of swelling and collapsible characteristics of unsaturated compacted expansive soil specimens and their relationship with suction. A series of volume change swell pressure tests and double oedometer tests were conducted at varying degree of saturation to evaluate swelling pressure and Collapse Potential of Bharuch expansive soil respectively. Suction measurements of soil were conducted by employing WP4C Dew point Potentiameter at different water content. Presence of higher negative pore pressure induced higher swelling pressure, which was observed to vary exponentially with total suction. Results indicated significant influence of soil suction on soil fabric arrangement, which substantially affected Collapse behaviour of expansive soil. Collapse Potential of Bharuch expansive soil was observed to decrease with increase in water content due to reduction in suction of soil indicating metastable state of soil at lower degree of saturation.
Helmut Krawinkler - One of the best experts on this subject based on the ideXlab platform.
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Significance of Modeling Deterioration in Structural Components for Predicting the Collapse Potential of Structures Under Earthquake Excitations
Advances in Performance-Based Earthquake Engineering, 2010Co-Authors: Helmut Krawinkler, Farzin Zareian, Dimitrios Lignos, Luis IbarraAbstract:The paper presents a summary of the state of knowledge in structural component and system modeling for predicting the Collapse Potential of buildings structural systems. In this context, Collapse implies dynamic instability in a sidesway mode, usually triggered by large story drifts that are amplified by structure P-Δ effects and deterioration in strength and stiffness of the components of the system. The Collapse capacity of a building is defined as the maximum ground motion intensity (often represented by the spectral acceleration at the first mode period) at which the structural system still maintains dynamic stability. A Collapse fragility curve that incorporates aleatory uncertainty due to record-to-record (RTR) variability is obtained by ordering the Collapse capacities for a representative set of ground motions. Realistic modeling of deterioration is found to be the most essential aspect of Collapse prediction through nonlinear dynamic analysis.
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Structural System Parameter Selection Based on Collapse Potential of Buildings in Earthquakes
Journal of Structural Engineering, 2010Co-Authors: Farzin Zareian, Helmut KrawinklerAbstract:This paper attempts to provide insight into the sensitivity of the Collapse capacity of moment-resisting frame and shear wall structures to variation in basic structural parameters, and the choice of an appropriate ground motion intensity measure, based on probabilistic estimation of the Collapse capacity of a structural system. The effects of fundamental period and base shear strength and of deformation and deterioration properties of structural components on the Collapse capacity of frame and wall structures are quantified. It is shown that the Collapse Potential of moment-resisting frames is highly sensitive to the ratio of column to beam strength; increasing this parameter from 1.2 to 2.4 will increase the median of Collapse capacity by up to 90%. Using a scalar ground motion intensity measure for estimating the Collapse capacity can lead to underestimation of median Collapse capacity by up to 50%, compared to using a vector-valued intensity measure. The provided information can be used to assist in the selection of a suitable structural system and associated parameters in design for Collapse safety. Closed-form solutions are formulated using a database of Collapse fragility curves developed for the sensitivity study. Application of these closed-form solutions for design decision making is illustrated through a comprehensive example.
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How to Predict the Probability of Collapse of Non-Ductile Building Structures
Seismic Risk Assessment and Retrofitting, 2009Co-Authors: Helmut Krawinkler, Dimitrios LignosAbstract:This chapter attempts to cover the range from rigorous probabilistic Collapse prediction of short period low-ductility buildings to simplified assessment of the Collapse Potential. The rigorous Collapse predictions are based on modeling the deteriorating properties of structural elements with low ductility and predicting the Collapse capacity for a given structural configuration and ground motion through incremental dynamic analysis. Consideration is given to the variation in Collapse capacity due to randomness of the ground motion. A parameter study is summarized in which the effects of strength and deformation capacity on the Collapse Potential of frames with infill walls is evaluated. It is found that shear strength has the largest effect on the Collapse capacity, and that deformation capacity and residual strength are of less importance.
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assessment of probability of Collapse and design for Collapse safety
Earthquake Engineering & Structural Dynamics, 2007Co-Authors: Farzin Zareian, Helmut KrawinklerAbstract:This paper illustrates a probabilistic-based methodology for quantifying the Collapse Potential of structural systems, which can provide us with more accurate estimates of losses induced by earthquakes. Applications of this methodology for assessment of Collapse Potential of existing buildings and design for Collapse safety are demonstrated by equations and example. The Collapse Potential is represented by the probability of Collapse at discrete hazard levels and on an annualized basis (mean annual frequency). The basic ingredient of the proposed methodology is a ‘Collapse fragility curve’ which expresses the probability of Collapse as a function of the selected ground motion intensity measure. The process for estimating the Collapse fragility using scalar and vector-valued ground motion intensity measure is demonstrated. The proposed assessment and design processes do incorporate the effect of aleatory and epistemic uncertainties. It was shown by example that the uncertainties, both aleatory and epistemic, have a significant effect on the outcome of the conceptual design for Collapse safety. Copyright © 2007 John Wiley & Sons, Ltd.
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Sensitivity of Collapse Potential of Buildings to Variations in Structural Systems and Structural Parameters
Structural Engineering Research Frontiers, 2007Co-Authors: Farzin Zareian, Helmut KrawinklerAbstract:This paper discusses the sensitivity of Collapse Potential of buildings to variation of structural parameters in different structural systems. In this study, Collapse capacity of a building subjected to a single ground motion is defined as the scalar ground motion intensity measure at which the building will become dynamically unstable. The process for obtaining the Collapse capacity using Incremental Dynamic Analysis is illustrated. For a given building, Collapse capacities of a number of ground motions are used to estimate the Collapse fragility curve for the building. Two types of structural systems are considered in this study, moment-resisting frames, and shear walls. Simple mathematical models denoted as “generic structures” are devised to model moment-resisting frames and shear walls. A comprehensive database of Collapse fragility curves (assuming a lognormal distribution for building Collapse capacity) for a wide-range of combination in structural parameters of generic moment-resisting frames and generic shear walls are developed. Using this database, closed-form equations for median and dispersion of building Collapse capacity curves are developed. Such equations not only facilitate the design and assessment processes, but also help in understanding the major trends and importance of certain parameters in changing the Collapse Potential of a structural system. Comparison between estimates of median Collapse capacity using the close-form equations and data show that the presented equations are in good agreement with the data. It is concluded that the primary causes of Collapse are severe cyclic deterioration and small plastic hinge rotation capacity of structural components. Furthermore, it is shown that P-Delta effect is the major cause of Collapse especially in moment-resisting frames with a small yield base shear coefficient. Another parameter that greatly affects the Collapse Potential of moment-resisting frames is the ratio of column to beam strength. It is shown that increasing this parameter from 1.2 (ACI suggestion) to 2.4 could increase the median of Collapse capacity by up to 90%. In this study, effect of incorporating a vector-valued ground motion intensity measure for estimating the Collapse capacity is investigated. It is shown that using the scalar ground motion intensity measure for defining the Collapse capacity can lead to underestimation of median Collapse capacity by 50%, compared to using a vector-valued intensity measure for this purpose. At the end, a brief discussion of the methods for design for Collapse safety is presented.