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Shideh Dashti

Bio: Shideh Dashti is an academic researcher from University of Colorado Boulder. The author has contributed to research in topics: Centrifuge & Liquefaction. The author has an hindex of 21, co-authored 91 publications receiving 1582 citations.


Papers
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Journal ArticleDOI
TL;DR: In this article, a series of centrifuge experiments involving buildings situated atop a layered soil deposit have been performed to identify the mechanisms involved in liquefaction-induced building settlement, including building-induced shear deformations combined with localized volumetric strains during partially drained cyclic loading are the dominant mechanisms.
Abstract: Seismically induced settlement of buildings with shallow foundations on liquefiable soils has resulted in significant damage in recent earthquakes. Engineers still largely estimate seismic building settlement using procedures developed to calculate postliquefaction reconsolidation settlement in the free-field. A series of centrifuge experiments involving buildings situated atop a layered soil deposit have been performed to identify the mechanisms involved in liquefaction-induced building settlement. Previous studies of this problem have identified important factors including shaking intensity, the liquefiable soil's relative density and thickness, and the building's weight and width. Centrifuge test results indicate that building settlement is not proportional to the thickness of the liquefiable layer and that most of this settlement occurs during earthquake strong shaking. Building-induced shear deformations combined with localized volumetric strains during partially drained cyclic loading are the dominant mechanisms. The development of high excess pore pressures, localized drainage in response to the high transient hydraulic gradients, and earthquake-induced ratcheting of the buildings into the softened soil are important effects that should be captured in design procedures that estimate liquefaction-induced building settlement.

210 citations

Journal ArticleDOI
TL;DR: In this article, the authors evaluated the relative importance of key settlement mechanisms by using mitigation techniques to minimize some of their respective contributions and found that the importance of settlement mechanisms depend on the characteristics of the earthquake motion, liquefiable soil, and building.
Abstract: The effective application of liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction. Centrifuge experiments were performed to study the dominant mechanisms of seismically induced settle- ment of buildings with rigid mat foundations on thin deposits of liquefiable sand. The relative importance of key settlement mechanisms was evaluated by using mitigation techniques to minimize some of their respective contributions. The relative importance of settlement mechanisms was shown to depend on the characteristics of the earthquake motion, liquefiable soil, and building. The initiation, rate, and amount of liquefaction-induced building settlement depended greatly on the rate of ground shaking. Engineering design procedures should incorporate this important feature of earthquake shaking, which may be represented by the time rate of Arias intensity i.e., the shaking intensity rate. In these experiments, installation of an independent, in-ground, perimetrical, stiff structural wall minimized deviatoric soil deformations under the building and reduced total building settlements by approximately 50%. Use of a flexible impermeable barrier that inhibited horizontal water flow without preventing shear deformation also reduced permanent building settlements but less significantly.

149 citations

Journal ArticleDOI
TL;DR: In this article, the results of a centrifuge experiment simulating seismic site response in a layered level liquefiable soil profile are used to evaluate and systematically compare the predictive capabilities of predictive capabilities.
Abstract: Results of a centrifuge experiment simulating seismic site response in a layered level liquefiable soil profile are used to evaluate and systematically compare the predictive capabilities o...

93 citations

Journal ArticleDOI
TL;DR: In this article, the authors make recommendations for estimating liquefaction-induced movements of buildings with shallow foundations based on these studies, and they make use of nonlinear effective stress analyses to capture the soil and building responses reasonably well and provide valuable insights.
Abstract: Liquefaction or cyclic softening from earthquake shaking have caused significant damage of buildings with shallow foundations. In recent earthquakes, buildings have punched into, tilted excessively, and slid laterally on liquefied/softened ground. The state-of-the-practice still largely involves estimating building settlement using empirical procedures developed to calculate post-liquefaction, one-dimensional, consolidation settlement in the “free-field” away from buildings. Performance-based earthquake engineering requires improved procedures, because these free-field analyses cannot possibly capture shear-induced and localized volumetric-induced deformations in the soil underneath shallow foundations. Recent physical and numerical modeling has provided useful insights into this problem. Centrifuge tests revealed that much of the building movement occurs during earthquake strong shaking, and its rate is dependent on the shaking intensity rate. Additionally, shear strains due to shaking-induced ratcheting of the buildings into the softened soil and volumetric strains due to localized drainage in response to high transient hydraulic gradients are important effects that are not captured in current procedures. Nonlinear effective stress analyses can capture the soil and building responses reasonably well and provide valuable insights. Based on these studies, recommendations for estimating liquefaction-induced movements of buildings with shallow foundations are made.

89 citations

Journal ArticleDOI
TL;DR: The iShake project serves as foundational work for further studies in seismic sensing on mobile devices by designing and fully implementing a system architecture, developing signal processing techniques unique to mobile sensing, and conducting shaking table tests to confirm the validity of the sensing platform.
Abstract: There are a variety of approaches to seismic sensing, which range from collecting sparse measurements with high-fidelity seismic stations to non-quantitative, post-earthquake surveys. The sparse nature of the high-fidelity stations and the inaccuracy of the surveys create the need for a high-density, semi-quantitative approach to seismic sensing. To fill this void, the UC Berkeley iShake project designed a mobile client-backend server architecture that uses sensor-equipped mobile devices to measure earthquake ground shaking. iShake provides the general public with a service to more easily contribute more quantitatively significant data to earthquake research by automating the data collection and reporting mechanisms via the iShake mobile application. The devices act as distributed sensors that enable measurements to be taken and transmitted with a cellular network connection. Shaking table testing was used to assess the quality of the measurements obtained from the iPhones and iPods on a benchmark of 150 ground motions. Once triggered by a shaking event, the devices transmit sensor data to a backend server for further processing. After a seismic event is verified by high-fidelity stations, filtering algorithms are used to detect falling phones, as well as device-specific responses to the event. A method was developed to determine the absolute orientation of a device to estimate the direction of first motion of a seismic event. A “virtual earthquake” pilot test was conducted on the UC Berkeley campus to verify the operation of the iShake system. By designing and fully implementing a system architecture, developing signal processing techniques unique to mobile sensing, and conducting shaking table tests to confirm the validity of the sensing platform, the iShake project serves as foundational work for further studies in seismic sensing on mobile devices.

87 citations


Cited by
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01 Jan 2016
TL;DR: The cognition in the wild is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can download it instantly.
Abstract: Thank you very much for reading cognition in the wild. Maybe you have knowledge that, people have look hundreds times for their favorite books like this cognition in the wild, but end up in malicious downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they cope with some harmful virus inside their laptop. cognition in the wild is available in our digital library an online access to it is set as public so you can download it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the cognition in the wild is universally compatible with any devices to read.

1,268 citations

Journal ArticleDOI
TL;DR: A survey on existing works in the MCS domain is presented and a detailed taxonomy is proposed to shed light on the current landscape and classify applications, methodologies, and architectures to outline potential future research directions and synergies with other research areas.
Abstract: Mobile crowdsensing (MCS) has gained significant attention in recent years and has become an appealing paradigm for urban sensing. For data collection, MCS systems rely on contribution from mobile devices of a large number of participants or a crowd. Smartphones, tablets, and wearable devices are deployed widely and already equipped with a rich set of sensors, making them an excellent source of information. Mobility and intelligence of humans guarantee higher coverage and better context awareness if compared to traditional sensor networks. At the same time, individuals may be reluctant to share data for privacy concerns. For this reason, MCS frameworks are specifically designed to include incentive mechanisms and address privacy concerns. Despite the growing interest in the research community, MCS solutions need a deeper investigation and categorization on many aspects that span from sensing and communication to system management and data storage. In this paper, we take the research on MCS a step further by presenting a survey on existing works in the domain and propose a detailed taxonomy to shed light on the current landscape and classify applications, methodologies, and architectures. Our objective is not only to analyze and consolidate past research but also to outline potential future research directions and synergies with other research areas.

320 citations

Journal ArticleDOI
TL;DR: The state‐of‐the‐art methods have been presented by conducting a detailed literature review of the recent applications of smartphones, UAVs, cameras, and robotic sensors used in acquiring and analyzing the vibration data for structural condition monitoring and maintenance.

301 citations

Journal ArticleDOI
TL;DR: One of the first case studies demonstrating the use of distributed acoustic sensing deployed on regional unlit fiber-optic telecommunication infrastructure (dark fiber) for broadband seismic monitoring of both near-surface soil properties and earthquake seismology is presented.
Abstract: We present one of the first case studies demonstrating the use of distributed acoustic sensing deployed on regional unlit fiber-optic telecommunication infrastructure (dark fiber) for broadband seismic monitoring of both near-surface soil properties and earthquake seismology. We recorded 7 months of passive seismic data on a 27 km section of dark fiber stretching from West Sacramento, CA to Woodland, CA, densely sampled at 2 m spacing. This dataset was processed to extract surface wave velocity information using ambient noise interferometry techniques; the resulting VS profiles were used to map both shallow structural profiles and groundwater depth, thus demonstrating that basin-scale variations in hydrological state could be resolved using this technique. The same array was utilized for detection of regional and teleseismic earthquakes and evaluated for long period response using records from the M8.1 Chiapas, Mexico 2017, Sep 8th event. The combination of these two sets of observations conclusively demonstrates that regionally extensive fiber-optic networks can effectively be utilized for a host of geoscience observation tasks at a combination of scale and resolution previously inaccessible.

257 citations