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Sumanta Haldar - One of the best experts on this subject based on the ideXlab platform.

  • Fore-aft and the side-to-side response of monopile supported offshore wind turbine in Liquefiable Soil
    Marine Georesources & Geotechnology, 2020
    Co-Authors: Sangeet Kumar Patra, Sumanta Haldar
    Abstract:

    This study investigates the effect of combined operational and seismic loads on the dynamic fore-aft, and the side-side response of monopile supported OWT in Liquefiable Soil under operational and ...

  • failure mechanisms of pile foundations in Liquefiable Soil parametric study
    International Journal of Geomechanics, 2010
    Co-Authors: Sumanta Haldar, G Sivakumar L Babu
    Abstract:

    This paper presents the response of piles in Liquefiable Soil under seismic loads. The effects of Soil, pile, and earthquake parameters on the two potential pile failure mechanisms, bending and buckling, are examined. The analysis is conducted using a two-dimensional plain strain finite difference program considering a nonlinear constitutive model for Soil liquefaction, strength reduction, and pile-Soil interaction. The depths of liquefaction, maximum lateral displacement, and maximum pile bending moment are obtained for concrete and steel piles for different Soil relative densities, pile diameters, earthquake predominant frequencies, and peak accelerations. The potential failure mechanisms of piles identified from the parametric analysis are discussed.

  • Probabilistic Seismic Design of Pile Foundations in Non Liquefiable Soil by Response Spectrum Approach
    Journal of Earthquake Engineering, 2009
    Co-Authors: Sumanta Haldar, G. L. Sivakumar Babu
    Abstract:

    The behavior of pile foundations in non Liquefiable Soil under seismic loading is considerably influenced by the variability in the Soil and seismic design parameters. Hence, probabilistic models for the assessment of seismic pile design are necessary. Deformation of pile foundation in non Liquefiable Soil is dominated by inertial force from superstructure. The present study considers a pseudo-static approach based on code specified design response spectra. The response of the pile is determined by equivalent cantilever approach. The Soil medium is modeled as a one-dimensional random field along the depth. The variability associated with undrained shear strength, design response spectrum ordinate, and superstructure mass is taken into consideration. Monte Carlo simulation technique is adopted to determine the probability of failure and reliability indices based on pile failure modes, namely exceedance of lateral displacement limit and moment capacity. A reliability-based design approach for the free head pile under seismic force is suggested that enables a rational choice of pile design parameters.

  • Seismic response of monopile supported offshore wind turbine in Liquefiable Soil
    Structures, 1
    Co-Authors: Sangeet Kumar Patra, Sumanta Haldar
    Abstract:

    Abstract Offshore wind turbines (OWT) are now constructed in the seismically active regions due to rising energy demand. This study investigates the seismic response of the monopile supported OWT in Liquefiable sand deposits under combined operational and seismic loads. A coupled Soil-monopile-tower interaction model is developed in OpenSees. Monopile and tower are modelled as linear Euler – Bernoulli beam. Monopile-Soil interaction is modelled using nonlinear p-y spring. Free-field motion at the outer spring nodes due to seismic motion is simulated by modelling a Soil domain using a two-dimensional plane strain quadrilateral element considering a with a solid–fluid fully coupled model. Various historical strong motion records and spectrum consistent artificial strong motion data are scaled and applied on OWT structure and various operational loads on the structure. The effect of intensity, sustained maximum acceleration of earthquake, and depth of liquefaction on the dynamic response of the OWT structure is studied. A design implication is also suggested for the OWT structure in Liquefiable Soil.

Weiyun Chen - One of the best experts on this subject based on the ideXlab platform.

  • shaking table tests on a three arch type subway station structure in a Liquefiable Soil
    Bulletin of Earthquake Engineering, 2015
    Co-Authors: Guoxing Chen, Su Chen, Zhihua Wang, Weiyun Chen
    Abstract:

    A series of large-scale shaking table tests were performed to investigate the damage mechanisms of a three-arch type subway station structure in a Liquefiable Soil experiencing strong motions. Methods to measure the displacement included the vision-based displacement test and the fiber Bragg grating test to measure the strain of the galvanized steel wire. Sand boils, waterspouts, ground surface cracks and settlements, and buoyancy movement of the model structure were observed. When the peak excess pore pressure ratios dramatically increased, the Arias intensity also dramatically increased. The peak acceleration of the model Soil also almost coincided with liquefaction of the model Soil. The seismic responses of the model structure and the Soil were shown to be more sensitive to input motions with larger low-frequency components, the phenomenon of high frequency filtering and low frequency amplification effect of the liquefied Soil were observed. The peak tensile strain located at the top and bottom of the center pillars was larger than that obtained at the subarch, while the peak tensile strain at the atrium arch was the smallest. The peak strain at the primary and secondary observation sections were remarkably affected by the spatial effect. The results can provide valuable insight into the seismic investigation of these subway structures.

Elli-konstantina V. Mylona - One of the best experts on this subject based on the ideXlab platform.

  • Rotational excitation of bridges supported on pile groups in soft or Liquefiable Soil deposits
    Computers & Structures, 2015
    Co-Authors: Anastasios Sextos, George Mylonakis, Elli-konstantina V. Mylona
    Abstract:

    This paper investigates the seismic response of reinforced concrete bridges founded on pile groups in soft or Liquefiable Soil deposits under simultaneous translational and rotational earthquake excitation. The pile cap rotational excitation results from pile bending under vertically propagating seismic S-waves. The response of the pile cap (in terms of displacement and rotation) defines the Foundation Input Motion (F.I.M.) computed through kinematic interaction analysis. The resulting superstructure demand due to the coupled translational and rotational excitation is compared to the demand developed due to translational only F.I.M. The results confirm earlier observations regarding the impact of pile bending on rigid body rotations of bridges founded with cast-in-drilled hole single piles. It is also shown that the excitation mechanism of pile groups in soft Soils is non-uniform along the pile length, thus exciting higher modes of vibration and inducing out-of-phase translational and rotational response of the pile cap.

Koichi Maekawa - One of the best experts on this subject based on the ideXlab platform.

  • Seismic interaction of underground RC ducts and neighboring bridge piers in Liquefiable Soil foundation
    Acta Geotechnica, 2015
    Co-Authors: Saeed Moshirabadi, Masoud Soltani, Koichi Maekawa
    Abstract:

    A coupled system of an underground reinforced concrete (RC) duct and a neighboring bridge pier supported by group piles is numerically investigated in sandy Soil at both drained and undrained Liquefiable states under seismic ground excitations. Parametric studies are conducted to evaluate influencing factors on seismic performances of these neighboring interactive structural systems. The numerical simulations are performed with the finite element code COM3 (COncrete Model for 3D) (Maekawa, Pimanmas and Okamura in Nonlinear mechanics of reinforced concrete, 2003 ), which is capable of simulation of inelastic performance of RC structure and high nonlinearity of Soil medium, especially on the Liquefiable loose sand. It is mechanically pointed out that liquefaction-induced uplift of underground ducts is substantially influenced by the presence of on-ground bridges. Alternatively, inertial forces induced to the on-ground bridge pier are also noticeably affected by the presence of the neighboring underground RC duct. It is pointed in practice of design that these nonlinear interacting responses between these neighboring infrastructures are greatly magnified on Liquefiable Soil foundations.

Santana Phani Gopal Madabhushi - One of the best experts on this subject based on the ideXlab platform.

  • Soil deformation during monotonic and seismic pipe uplift in Liquefiable Soil
    Journal of Pipeline Engineering, 2014
    Co-Authors: Siau Chen Chian, Junkan Wang, S K Haigh, Santana Phani Gopal Madabhushi
    Abstract:

    Uplift of pipelines can take place due to either thermal upheaval buckling or floatation during 47 earthquake-induced Soil liquefaction. Despite similar global uplift failure being observed in 48 both cases, the deformation of the Soil surrounding the lifted pipe differs. The use of the 49 Particle Image Velocimetry (PIV) technique showed a wider spatial deformation mechanism 50 occurring during the seismic uplift of the buoyant pipe in liquefied Soil as compared to the 51 localised Soil movement from monotonic uplift of a pipe in full-scale and centrifuge tests. 52 This is mainly due to the difference in Soil conditions between the near and far field regions 53 of the pipe. In the former case, cyclic response of the pipe under horizontal earthquake 54 shaking exerts external stresses onto the adjacent liquefied Soil, thereby causing Soil dilation 55 to occur near the pipe. A large difference in Soil stiffness between near (less liquefied) and far 56 field (fully liquefied) regions is therefore developed which encourages the liquefied Soil at far 57 field to fill the expanding void beneath the uplifted pipe. This is unlike the more uniform 58 stiffness of Soil at drained condition in the latter case, which thereby induces displacement of 59 Soil at near field towards the invert of the pipe. 60

  • Soil liquefaction induced uplift of underground structures physical and numerical modeling
    Journal of Geotechnical and Geoenvironmental Engineering, 2014
    Co-Authors: Siau Chen Chian, Kohji Tokimatsu, Santana Phani Gopal Madabhushi
    Abstract:

    AbstractUnderground structures located in Liquefiable Soil deposits are susceptible to floatation following a major earthquake event. Such failure phenomenon generally occurs when the Soil liquefies and loses its shear resistance against the uplift force from the buoyancy of the underground structure. Numerical modeling accompanied with centrifuge experiments with shallow circular structures has been carried out to investigate the floatation failure at different buried depths of the structure. The influence of the magnitude of input sinusoidal earthquake shaking was also studied. Both numerical and experimental results showed matching uplift response of the structures and acceleration and pore-pressure measurements in the liquefied Soil deposit. A higher uplift displacement of the structure was observed for shallower buried depth, thereby indicating the influence of overlying Soil weight against floatation. Results also showed that the structures commenced floatation in the presence of high excess pore pr...

  • effect of buried depth and diameter on uplift of underground structures in liquefied Soils
    Soil Dynamics and Earthquake Engineering, 2012
    Co-Authors: Siau Chen Chian, Santana Phani Gopal Madabhushi
    Abstract:

    Abstract In an earthquake, underground structures located in Liquefiable Soil deposits are susceptible to floatation following an earthquake event due to their lower unit weight relative to the surrounding saturated Soil. The uplift displacement of an underground structure in Liquefiable Soil deposit can be affected by the buried depth and size of the structure. Dynamic centrifuge tests have been carried out to investigate the influence of these factors by measuring the uplift displacement of shallow model circular structures. Ratios for the buried depth and diameter effects of the structure are introduced to compare the uplift displacement in different Soil and earthquake conditions. With the depth effect and diameter effect ratios, the uplift displacement of a buoyant structure in Liquefiable Soil can also be estimated based on performance of similar structures in comparable Soil condition and subjected to a similar earthquake event.