• Geomechanics and Engineering
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• v.39 no.3
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• pp.227-240
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• 2024

This study investigates the control effect of isolation piles on ground settlement resulting from foundation pit excavation. Based on the three-stage analysis method, first, the Kerr three-parameter foundation model is introduced, and the deflection differential equation is derived to solve the horizontal displacement of the diaphragm wall. Then, based on the horizontal displacement of the diaphragm wall, the boundary element method is used to calculate the additional stress at the boundary of the foundation pit, and the horizontal additional displacement and additional stress of the soil free field at the position of the isolation pile are obtained using the Mindlin solution. Subsequently, soil free field additional stress is applied to the pile foundation, and the shielding effect of group piles is also considered. Based on the Kerr three-parameter foundation model, the deflection differential equation of the pile foundation under the influence of horizontally oriented additional stress is established to solve the horizontal displacement of the isolated piles. Finally, the boundary element method is used again to invert the additional stress caused by the horizontal displacement of the isolation pile, and the surface settlement after the isolation pile is calculated in combination with the Mindlin vertical displacement solution. The spatial finite element model is established and compared with the theoretical calculation results to prove the rationality of the theory. The influence of basic construction parameters is analyzed theoretically, and it is found that the surface settlement is reduced by 30.9% compared with no isolation pile. Of the selected parameters in this paper, the effects of the isolation pile's controlled diameter, spacing, and elastic modulus, the thickness and elastic modulus of the diaphragm wall on the surface settlement are 4.9 mm, 3.1 mm, 3.3 mm, 3 mm, 1.7 mm, respectively, which are 45.4%, 28.7%, 30.6%, 27.8%, 15.7% of the standard working conditions, respectively. This shows that optimization of the isolation pile parameters has the best effect on surface settlement, optimization of the diaphragm wall parameters has the poor effect.

• Structural Engineering and Mechanics
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• v.73 no.2
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• pp.191-207
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• 2020

This study aims at investigating the size-dependent free vibration of porous nanoplates when exposed to hygrothermal environment and rested on Kerr foundation. Based on the modified power-law model, material properties of porous functionally graded (FG) nanoplates are supposed to change continuously along the thickness direction. The generalized nonlocal strain gradient elasticity theory incorporating three scale factors (i.e. lower- and higher-order nonlocal parameters, strain gradient length scale parameter), is employed to expand the assumption of second shear deformation theory (SSDT) for considering the small size effect on plates. The governing equations are obtained based on Hamilton's principle and then the equations are solved using an analytical method. The elastic Kerr foundation, as a highly effected foundation type, is adopted to capture the foundation effects. Three different patterns of porosity (namely, even, uneven and logarithmic-uneven porosities) are also considered to fill some gaps of porosity impact. A comparative study is given by using various structural models to show the effect of material composition, porosity distribution, temperature and moisture differences, size dependency and elastic Kerr foundation on the size-dependent free vibration of porous nanoplates. Results show a significant change in higher-order frequencies due to small scale parameters, which could be due to the size effect mechanisms. Furthermore, Porosities inside of the material properties often present a stiffness softening effect on the vibration frequency of FG nanoplates.

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.809-819
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• 2020

For the first time, the influence of in-plane magnetic field on wave propagation of Graphene Nano-Platelets (GNPs) polymer composite nanoplates is investigated here. The impact of three- parameter Kerr foundation is also considered. There are two different reinforcement distribution patterns (i.e. uniformly and non-uniformly) while the material properties of the nanoplate are estimated through the Halpin-Tsai model and a rule of mixture. To consider the size-dependent behavior of the structure, Eringen Nonlocal Differential Model (ENDM) is utilized. The equations of wave motion derived based on a higher-order shear deformation refined theory through Hamilton's principle and an analytical technique depending on Taylor series utilized to find the wave frequency as well as phase velocity of the GNPs reinforced nanoplates. A parametric investigation is performed to determine the influence of essential phenomena, such as the nonlocality, GNPs conditions, Kerr foundation parameters, and wave number on the both longitudinal and flexural wave characteristics of GNPs reinforced nanoplates.

• Steel and Composite Structures
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• v.43 no.5
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• pp.581-601
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• 2022

The main objective of this research work is to investigate the free vibration behavior of annular sandwich plates resting on the Kerr foundation at thermal conditions. This sandwich configuration is composed of two FGM face sheets as coating layer and a porous GPLRC (GPL reinforced composite) core. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the core thickness direction. To model closed-cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme is used, while the Poisson's ratio and density are computed by the rule of mixtures. Besides, the material properties of two FGM face sheets change continuously through the thickness according to the power-law distribution. To capture fundamental frequencies of the annular sandwich plate resting on the Kerr foundation in a thermal environment, the analysis procedure is with the aid of Reddy's shear-deformation plate theory based high-order shear deformation plate theory (HSDT) to derive and solve the equations of motion and boundary conditions. The governing equations together with related boundary conditions are discretized using the generalized differential quadrature (GDQ) method in the spatial domain. Numerical results are compared with those published in the literature to examine the accuracy and validity of the present approach. A parametric solution for temperature variation across the thickness of the sandwich plate is employed taking into account the thermal conductivity, the inhomogeneity parameter, and the sandwich schemes. The numerical results indicate the influence of volume fraction index, GPLs volume fraction, porosity coefficient, three independent coefficients of Kerr elastic foundation, and temperature difference on the free vibration behavior of annular sandwich plate. This study provides essential information to engineers seeking innovative ways to promote composite structures in a practical way.