The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

Gilberto Mosqueda - One of the best experts on this subject based on the ideXlab platform.

  • coupled Horizontal vertical stability of bearings under dynamic loading
    Earthquake Engineering & Structural Dynamics, 2016
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, Gilberto Mosqueda
    Abstract:

    Summary In this study, the coupled Horizontal–vertical behavior of elastomeric bearings subjected to dynamic loading is studied in detail. Under extreme dynamic loading, elastomeric bearings exhibit unstable behavior and an instantaneous loss of Horizontal Stiffness that is recoverable. Building on an earlier study where the authors developed an analytical model for the Horizontal behavior of bearings under dynamic loads, in this study, a new analytical model for the coupled Horizontal–vertical behavior of the bearings is developed. The coupled behavior of the bearing is first studied for quasi-static loading, and later, the behavior of the bearings under dynamic loading is studied. A clear distinction is made between different types of deformation the bearing undergoes in the vertical direction. Based on experimental results, it is observed that the behavior of the bearings under dynamic loading differs markedly from that observed under static loading. A new analytical model is proposed that can account for the coupled Horizontal–vertical behavior of the bearings under dynamic loading. The proposed analytical model for predicting the post-stability vertical behavior of the bearings is verified using experimental results. The model proposed is found to successfully predict the coupled Horizontal–vertical behavior of elastomeric bearings. Copyright © 2015 John Wiley & Sons, Ltd.

  • dynamic lateral stability of elastomeric seismic isolation bearings
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, A Masroor, Gilberto Mosqueda
    Abstract:

    AbstractPredicting the response of elastomeric seismic isolation bearings when subjected to severe ground motions is challenging due to the highly nonlinear behavior associated with the bearings under a combination of large displacements and axial loads. In particular, the Horizontal Stiffness of the bearings is a function of both Horizontal displacement as well as axial load that varies due to overturning moments. Previous analytical models or formulations to model these bearings were mainly developed to estimate critical loads at the stability limit. Only few of these models are capable of estimating the correct nonlinear behavior of bearings observed at Horizontal displacements in excess of the bearing width. In this study, a nonlinear analytical model is presented that is capable of modeling the dynamic response of bearings more accurately at all displacement ranges, especially beyond the stability limit and is verified with experimental data from an earlier experimental study. It was observed in the ...

Raphaël F. Garcia - One of the best experts on this subject based on the ideXlab platform.

  • A Numerical Model of the SEIS Leveling System Transfer Matrix and Resonances: Application to SEIS Rotational Seismology and Dynamic Ground Interaction
    Space Science Reviews, 2018
    Co-Authors: Lucile Fayon, Brigitte Knapmeyer-endrun, Aron Kramer, Foivos Karakostas, Marco Bierwirth, Naomi Murdoch, Philippe Lognonné, Sharon Kedar, Pierre Delage, Raphaël F. Garcia
    Abstract:

    Both sensors of the SEIS instrument (VBBs and SPs) are mounted on the mechanical leveling system (LVL), which has to ensure a level placement on the Martian ground under currently unknown local conditions, and provide the mechanical coupling of the seismometers to the ground. We developed a simplified analytical model of the LVL structure in order to reproduce its mechanical behavior by predicting its resonances and transfer function. This model is implemented numerically and allows to estimate the effects of the LVL on the data recorded by the VBBs and SPs on Mars. The model is validated through comparison with the Horizontal resonances (between 35 and 50 Hz) observed in laboratory measurements. These modes prove to be highly dependent of the ground Horizontal Stiffness and torque. For this reason, an inversion study is performed and the results are compared with some experimental measurements of the LVL feet’s penetration in a martian regolith analog. This comparison shows that the analytical model can be used to estimate the elastic ground properties of the InSight landing site. Another application consists in modeling the 6 sensors on the LVL at their real positions, also considering their sensitivity axes, to study the performances of the global SEIS instrument in translation and rotation. It is found that the high frequency ground rotation can be measured by SEIS and, when compared to the ground acceleration, can provide ways to estimate the phase velocity of the seismic surface waves at shallow depths. Finally, synthetic data from the active seismic experiment made during the HP3 penetration and SEIS rotation noise are compared and used for an inversion of the Rayleigh phase velocity. This confirms the perspectives for rotational seismology with SEIS which will be developed with the SEIS data acquired during the commissioning phase after landing.

Satish Nagarajaiah - One of the best experts on this subject based on the ideXlab platform.

  • coupled Horizontal vertical stability of bearings under dynamic loading
    Earthquake Engineering & Structural Dynamics, 2016
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, Gilberto Mosqueda
    Abstract:

    Summary In this study, the coupled Horizontal–vertical behavior of elastomeric bearings subjected to dynamic loading is studied in detail. Under extreme dynamic loading, elastomeric bearings exhibit unstable behavior and an instantaneous loss of Horizontal Stiffness that is recoverable. Building on an earlier study where the authors developed an analytical model for the Horizontal behavior of bearings under dynamic loads, in this study, a new analytical model for the coupled Horizontal–vertical behavior of the bearings is developed. The coupled behavior of the bearing is first studied for quasi-static loading, and later, the behavior of the bearings under dynamic loading is studied. A clear distinction is made between different types of deformation the bearing undergoes in the vertical direction. Based on experimental results, it is observed that the behavior of the bearings under dynamic loading differs markedly from that observed under static loading. A new analytical model is proposed that can account for the coupled Horizontal–vertical behavior of the bearings under dynamic loading. The proposed analytical model for predicting the post-stability vertical behavior of the bearings is verified using experimental results. The model proposed is found to successfully predict the coupled Horizontal–vertical behavior of elastomeric bearings. Copyright © 2015 John Wiley & Sons, Ltd.

  • dynamic lateral stability of elastomeric seismic isolation bearings
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, A Masroor, Gilberto Mosqueda
    Abstract:

    AbstractPredicting the response of elastomeric seismic isolation bearings when subjected to severe ground motions is challenging due to the highly nonlinear behavior associated with the bearings under a combination of large displacements and axial loads. In particular, the Horizontal Stiffness of the bearings is a function of both Horizontal displacement as well as axial load that varies due to overturning moments. Previous analytical models or formulations to model these bearings were mainly developed to estimate critical loads at the stability limit. Only few of these models are capable of estimating the correct nonlinear behavior of bearings observed at Horizontal displacements in excess of the bearing width. In this study, a nonlinear analytical model is presented that is capable of modeling the dynamic response of bearings more accurately at all displacement ranges, especially beyond the stability limit and is verified with experimental data from an earlier experimental study. It was observed in the ...

  • stability of elastomeric seismic isolation bearings
    Journal of Structural Engineering-asce, 1999
    Co-Authors: Satish Nagarajaiah, Keith Ferrell
    Abstract:

    Elastomeric seismic isolation bearings are subjected to large axial loads and lateral displacements during strong earthquakes. The existing Koh-Kelly model (1986, 1988, 1989) for elastomeric bearings accounts for axial load effects on Horizontal Stiffness. This linear model is based on small displacements and rotations and predicts stable postcritical behavior or increasing critical load with increasing Horizontal displacement; however, unstable postcritical behavior is observed in the bearing test results presented in this study. The analytical model developed in this study, based on the Koh-Kelly model, includes large displacements, large rotations, and nonlinearity of rubber, and it predicts unstable postcritical behavior. The formulation of the analytical model, calibration, and verification using experimental results are presented. It is shown that the critical load reduces with increasing Horizontal displacement and that the Horizontal Stiffness reduces with increasing Horizontal displacement and axial load. It is also shown that the critical load capacity at a Horizontal displacement equal to the width of the bearing is not equal to zero, as predicted by the approximate procedure used in design, but higher.

Venkata Srivishnu M Vemuru - One of the best experts on this subject based on the ideXlab platform.

  • coupled Horizontal vertical stability of bearings under dynamic loading
    Earthquake Engineering & Structural Dynamics, 2016
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, Gilberto Mosqueda
    Abstract:

    Summary In this study, the coupled Horizontal–vertical behavior of elastomeric bearings subjected to dynamic loading is studied in detail. Under extreme dynamic loading, elastomeric bearings exhibit unstable behavior and an instantaneous loss of Horizontal Stiffness that is recoverable. Building on an earlier study where the authors developed an analytical model for the Horizontal behavior of bearings under dynamic loads, in this study, a new analytical model for the coupled Horizontal–vertical behavior of the bearings is developed. The coupled behavior of the bearing is first studied for quasi-static loading, and later, the behavior of the bearings under dynamic loading is studied. A clear distinction is made between different types of deformation the bearing undergoes in the vertical direction. Based on experimental results, it is observed that the behavior of the bearings under dynamic loading differs markedly from that observed under static loading. A new analytical model is proposed that can account for the coupled Horizontal–vertical behavior of the bearings under dynamic loading. The proposed analytical model for predicting the post-stability vertical behavior of the bearings is verified using experimental results. The model proposed is found to successfully predict the coupled Horizontal–vertical behavior of elastomeric bearings. Copyright © 2015 John Wiley & Sons, Ltd.

  • dynamic lateral stability of elastomeric seismic isolation bearings
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Venkata Srivishnu M Vemuru, Satish Nagarajaiah, A Masroor, Gilberto Mosqueda
    Abstract:

    AbstractPredicting the response of elastomeric seismic isolation bearings when subjected to severe ground motions is challenging due to the highly nonlinear behavior associated with the bearings under a combination of large displacements and axial loads. In particular, the Horizontal Stiffness of the bearings is a function of both Horizontal displacement as well as axial load that varies due to overturning moments. Previous analytical models or formulations to model these bearings were mainly developed to estimate critical loads at the stability limit. Only few of these models are capable of estimating the correct nonlinear behavior of bearings observed at Horizontal displacements in excess of the bearing width. In this study, a nonlinear analytical model is presented that is capable of modeling the dynamic response of bearings more accurately at all displacement ranges, especially beyond the stability limit and is verified with experimental data from an earlier experimental study. It was observed in the ...

Lucile Fayon - One of the best experts on this subject based on the ideXlab platform.

  • A Numerical Model of the SEIS Leveling System Transfer Matrix and Resonances: Application to SEIS Rotational Seismology and Dynamic Ground Interaction
    Space Science Reviews, 2018
    Co-Authors: Lucile Fayon, Brigitte Knapmeyer-endrun, Aron Kramer, Foivos Karakostas, Marco Bierwirth, Naomi Murdoch, Philippe Lognonné, Sharon Kedar, Pierre Delage, Raphaël F. Garcia
    Abstract:

    Both sensors of the SEIS instrument (VBBs and SPs) are mounted on the mechanical leveling system (LVL), which has to ensure a level placement on the Martian ground under currently unknown local conditions, and provide the mechanical coupling of the seismometers to the ground. We developed a simplified analytical model of the LVL structure in order to reproduce its mechanical behavior by predicting its resonances and transfer function. This model is implemented numerically and allows to estimate the effects of the LVL on the data recorded by the VBBs and SPs on Mars. The model is validated through comparison with the Horizontal resonances (between 35 and 50 Hz) observed in laboratory measurements. These modes prove to be highly dependent of the ground Horizontal Stiffness and torque. For this reason, an inversion study is performed and the results are compared with some experimental measurements of the LVL feet’s penetration in a martian regolith analog. This comparison shows that the analytical model can be used to estimate the elastic ground properties of the InSight landing site. Another application consists in modeling the 6 sensors on the LVL at their real positions, also considering their sensitivity axes, to study the performances of the global SEIS instrument in translation and rotation. It is found that the high frequency ground rotation can be measured by SEIS and, when compared to the ground acceleration, can provide ways to estimate the phase velocity of the seismic surface waves at shallow depths. Finally, synthetic data from the active seismic experiment made during the HP3 penetration and SEIS rotation noise are compared and used for an inversion of the Rayleigh phase velocity. This confirms the perspectives for rotational seismology with SEIS which will be developed with the SEIS data acquired during the commissioning phase after landing.