• Structural Engineering and Mechanics
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• v.49 no.1
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• pp.95-110
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• 2014

The study deals with physical modeling of space frame-pile foundation and soil system using finite element models. The superstructure frame is analyzed using complete three-dimensional finite element method where the component of the frame such as slab, beam and columns are descretized using 20 node isoparametric continuum elements. Initially, the frame is analyzed assuming the fixed column bases. Later the pile foundation is worked out separately wherein the simplified models of finite elements such as beam and plate element are used for pile and pile cap, respectively. The non-linear behaviour of soil mass is incorporated by idealizing the soil as non-linear springs using p-y curve along the lines similar to that by Georgiadis et al. (1992). For analysis of pile foundation, the non-linearity of soil via p-y curve approach is incorporated using the incremental approach. The interaction analysis is conducted for the parametric study. The non-linearity of soil is further incorporated using iterative approach, i.e., secant modulus approach, in the interaction analysis. The effect the various parameters of the pile foundation such as spacing in a group and configuration of the pile group is evaluated on the response of superstructure owing to non-linearity of the soil. The response included the displacement at the top of the frame and bending moment in columns. The non-linearity of soil increases the top displacement in the range of 7.8%-16.7%. However, its effect is found very marginal on the absolute maximum moment in columns. The hogging moment decreases by 0.005% while sagging moment increases by 0.02%.

• Structural Engineering and Mechanics
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• v.55 no.3
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• pp.495-510
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• 2015

Free vibration of non-uniform embedded nanoplates based on classical (Kirchhoff's) plate theory in conjunction with nonlocal elasticity theory has been studied. The nanoplate is assumed to be rested on two-parameter Winkler-Pasternak elastic foundation. Non-uniform material properties of nanoplates have been considered by taking linear as well as quadratic variations of Young's modulus and density along the space coordinates. Detailed analysis has been reported for all possible casesof such variations. Trial functions denoting transverse deflection of the plate are expressed in simple algebraic polynomial forms. Application of the present method converts the problem into generalised eigen value problem. The study aims to investigate the effects of non-uniform parameter, elastic foundation, nonlocal parameter, boundary condition, aspect ratio and length of nanoplates on the frequency parameters. Three-dimensional mode shapes for some of the boundary conditions have also been illustrated. One may note that present method is easier to handle any sets of boundary conditions at the edges.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.602-607
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• 1998

Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus (storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

• Journal of KSNVE
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• v.8 no.5
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• pp.900-907
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• 1998

Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus(storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.102-107
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• 2009

Recently, the use of barrette pile is remarkably increased specially for high-rise building and bridge foundations. However, on the contrary, very few studies have been made for analyzing barrette pile behavior considering interface behavior between pile and soils around. Therefore, in this paper, these effects are evaluated by using the 3-dimensional non-linear finite element method with the results of full-scale pile load test from the fields. In addition to that, the selection of proper stiffness modulus on the pile interface is discussed.

• Elastomers and Composites
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• v.35 no.1
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• pp.4-11
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• 2000

A rubber diaphragm is a critical element of accumulators. The material of a diaphragm is nitrile rubber so as to recover and adjust the large deformation under external pressure fluctuation. The performance of accumulators is influenced by the deformation behaviors of the diaphragm. A large deformation behavior of the diaphragm has been investigated using the commercial finite element program MARC K7.1. The several elastic moduli have been used in linear analysis and Ogden's coefficients have been used in non-linear analysis. As a result, it has been shown that the deformation behavior with a elastic modulus of $0.3 kg/mm^2$ is similar to the behavior of non-linear analysis. And, the modified diaphragm shape to reduce the stress concentration has been proposed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.6
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• pp.122-129
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• 2000

The purpose of this study is to investigate both the fundamental and some higher natural frequencies and mode shapes of compressive members resting on the linear elastic foundation. The model of compressive member is based on the classical Bernoulli-Euler beam theory. The differential equation governing free vibrations of such members subjected to an axial load is derived and solved numerically for calculating the natural frequencies and mode shapes. The Improved Euler method is used to integrate the differential equation and the Determinant Search method combined with the Regula-Falsi method to determine the natural frequencies, respectively. In numerical examples, the hinged-hinged, hinged-clamped, clamped-hinged and clamped-clamped end constraints are considered. The convergence analysis is conducted for determining the available step size in the Improved Euler method. The validation of theories developed herein is also conducted by comparing the numerical results between this study and SAP 90. The non-dimensional frequency parameters are presented as the non-dimensional system parameters: section ratio, modulus parameter and load parameter. Also typical mode shapes are presented.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.713-722
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• 2019

Micromechanics is a technique for the analysis of composites or heterogeneous materials which focuses on the components of the intended structure. Each one of the components can exhibit isotropic behavior, but the microstructure characteristics of the heterogeneous material result in the anisotropic behavior of the structure. In this research, the general mechanical properties of a 3D anisotropic and heterogeneous Representative Volume Element (RVE), have been determined by applying periodic boundary conditions (PBCs), using the Asymptotic Homogenization Theory (AHT) and strain energy. In order to use the homogenization theory and apply the periodic boundary conditions, the ABAQUS scripting interface (ASI) has been used along with the Python programming language. The results have been compared with those of the Homogeneous Boundary Conditions method, which leads to an overestimation of the effective mechanical properties. According to the results, applying homogenous boundary conditions results in a 33% and 13% increase in the shear moduli G₂₃ and G₁₂, respectively. In polymeric composites, the fibers have linear and brittle behavior, while the resin exhibits a non-linear behavior. Therefore, the nonlinear effects of resin on the mechanical properties of the composite material is studied using a user-defined subroutine in Fortran (USDFLD). The non-linear shear stress-strain behavior of unidirectional composite laminates has been obtained. Results indicate that at arbitrary constant stress as 80 MPa in-plane shear modulus, G₁₂, experienced a 47%, 41% and 31% reduction at the fiber volume fraction of 30%, 50% and 70%, compared to the linear assumption. The results of this study are in good agreement with the analytical and experimental results available in the literature.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.479-489
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• 2014

In the present study a parametric analysis is conducted to study the effect of pile dimension and soil properties on the nonlinear dynamic response of pile subjected to lateral sinusoidal load at the pile head. The study is conducted on soil-pile model of different pile diameter, pile length and soil modulus, and results are compared to get the effect. The soil-pile system is modelled using Finite element method. The programming is done in MATLAB. Time history analysis of model is done for varying non-dimensional frequency of load and the results are compared to get the non-dimensional frequency at which pile head displacement is maximum in each case. Maximum possible bending moment and soil-pile interacting forces for the dynamic excitation of the pile is also compared. When results are compared with the linear response, it is observed that non-dimensional frequency is reduced in nonlinear response on account of reduction in the soil stiffness due to yielding. Nonlinear response curve shows high amplitude as compared to linear response curve.

• Steel and Composite Structures
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• v.7 no.1
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• pp.19-34
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• 2007

This paper presents results of a non-linear finite element analysis of axially loaded slender hollow structural section (HSS) columns, strengthened using high modulus carbon-fiber reinforced polymer (CFRP) longitudinal sheets. The model was developed and verified against both experimental and other analytical models. Both geometric and material nonlinearities, which are attributed to the column's initial imperfection and plasticity of steel, respectively, are accounted for. Residual stresses have also been modeled. The axial strength in the experimental study was found to be highly dependent on the column's imperfection. Consequently, no specific correlation was established experimentally between strength gain and amount of CFRP. The model predicted the ultimate loads and failure modes quite reasonably and was used to isolate the effects of CFRP strengthening from the columns' imperfections. It was then used in a parametric study to examine columns of different slenderness ratios, imperfections, number of CFRP layers, and level of residual stresses. The study demonstrated the effectiveness of high modulus CFRP in increasing stiffness and strength of slender columns. While the columns' imperfections affect their actual strengths before and after strengthening,the percentage gain in strength is highly dependent on slenderness ratio and CFRP reinforcement ratio, rather than the value of imperfection.