• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1646-1652
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• 2006

A model of mechanical behavior of microcantilever due to intrinsic strain during deposition of MEMS structures is derived. A linear ordinary differential equation is derived for the beam deflection as a function of the thickness of the deposited layer. Closed-form solutions are not possible, but numerical solutions are plotted for various dimensionless ratios of the beam stiffness, the intrinsic strain, and the elastic moduli of the substrate and deposited layer. This model predicts the deflection of the cantilever as a function of the deposited layer thickness and the residual stress distribution during deposition. The usefulness of these equations is that they are indicative of the real time behavior of the structures, i.e. it predicts the deflection of the beam continuously during deposition process.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.283-289
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• 2000

The panel shear and bearing strengths determining the seismic resistance of reinforced concrete column-to-steel beam connections are predicted by various methods for four previously tested exterior beam-column joints. The analytical approach to model the joint deformation is also examined. Several analyses incorporating the deformations of panel shear and bearing in the joint are demonstrated using a analyses incorporating the deformations of panel shear and bearing in the joint are demonstrated using a fairly simple connection model in the commercial packages such as Drain2dx and IDARC. The strength prediction results indicated that the ASCE method with the modifcation of the comprssion strut contribution is th most accurate. It is also considered that the analytical model presented including the joint deformation can be used for the overall analysis

• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.51-60
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• 2004

본 논문에서는 냉간성형 ㄷ 형강보에 대해 국부좌굴을 고려한 휨해석을 하였다. 유한요소법을 이용하여 주어진 하중 상태에서의 응력을 구한후 국부좌굴 효과를 고려하기 위해규준에서 주어진 유효폭 개념을 이용하여 유효 단면적을 결정하였으며, 결정된 유효 단면적으로부터 응력을 계산 하였다. x축에 대한 휨응력 뿐 아니라 y축에 대한 휨응력과 뒤틀림 응력값을 고려하였으며, 이를 하중이 전단중심에 작용하는 경우와 도심에 작용하는 두가지의 경우에 대하여 연구를 수행하였다. 연구 결과는 하중-처짐 곡선으로 나타내었다.

• Structural Engineering and Mechanics
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• 제37권1호
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• pp.79-93
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• 2011

A simple mechanical model is proposed to demonstrate qualitatively the pancake progressive collapse of multi-storey structures. The impact between two collapsed storeys is simulated using a simple algorithm that builds on virtual mass-spring-damper system. To analyze various collapse modes, columns and beams are considered separately. Parametric studies show that the process of progressive collapse involves a large number of complex mechanisms. However, the proposed model provides a simple numerical tool to assess the overall behavior of collapse arising from a few initiating causes. Unique features, such as beam-to-beam connection failure criterion, and beam-to-column connection failure criterion are incorporated into the program. Besides, the criterion of local failure of structural members can also be easily incorporated into the proposed model.

• Advances in materials Research
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• 제11권1호
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• pp.41-57
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• 2022

This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

• Advances in nano research
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• 제17권1호
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• pp.9-18
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• 2024

This paper presents the development of an educational management model for analyzing the dynamic instability of nanocomposite sandwich beams. The model aims to provide a comprehensive framework for understanding the behavior of sandwich micro beams with foam cores, featuring top and bottom layers made of smart and porous functionally graded materials (FGM) nanocomposites. The bottom layer is influenced by an external electric field, and the entire beam is supported by a visco-Pasternak foundation, accounting for spring, shear, and damping constants. Using the Kelvin-Voigt theory to model structural damping and incorporating size effects based on strain gradient theory, the model employs the parabolic shear deformation beam theory (PSDBT) to derive motion equations through Hamilton's principle. The differential quadrature method (DQM) is applied to solve these equations, accurately identifying the improvement in student understanding (ISU) of the beams. The impact of various parameters, including FGM properties, external voltage, geometric constants, and structural damping, on the DIR is thoroughly examined. The educational model is validated by comparing its outcomes with existing studies, highlighting the increase in ISU with the application of negative external voltage to the smart layer. This model serves as a valuable educational tool for engineering students and researchers studying the dynamic stability of advanced nanocomposite structures.

• Structural Engineering and Mechanics
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• 제17권5호
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• pp.691-706
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• 2004

The paper presents shear lag parameters for beam-to-column connections in steel box piers. Previous researches have analyzed beam-to-column connections in steel piers using a shear lag parameter ${\eta}_o$ obtained from a simple beam model, which is not based on a reasonable design assumption. Instead, the current paper proposes a cantilever beam model and has proved the effectiveness through theoretical and experimental studies. The paper examines the inaccuracy of the previous researches by estimating the effective width, the width-span length ratio L/b, and the sectional area ratio S of a cantilever beam. Two different shear lag parameters are defined using the cantilever model and the results are compared each other. The first type of shear lag parameter ${\eta}_c$ of a cantilever beam is derived using additional moments from various stress distribution functions while the other shear lag parameter ${\eta}_{eff}$ of a cantilever beam is defined based on the concept of the effective width. An evaluation method for shear lag stresses has been investigated by comparing analytical stresses with test results. Through the study, it could be observed that the shear lag parameter ${\eta}_{eff}$ agrees with ${\eta}_c$ obtained from the $2^{nd}$ order stress distribution function. Also, it could be observed that the shear lag parameter ${\eta}_c$ using the $4^{th}$ order stress distribution function almost converges to the upper bound of test results.

• Structural Engineering and Mechanics
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• 제27권5호
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• pp.555-574
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• 2007

Static response of an elastic beam on a two-parameter tensionless foundation is investigated by assuming that the beam is symmetrically subjected to a uniformly distributed load and concentrated edge loads. Governing equations of the problem are obtained and solved by pointing out that a concentrated edge foundation reaction in addition to a continuous foundation reaction along the beam axis in the case of complete contact and a discontinuity in the foundation reactions in the case of partial contact come into being as a direct result of the two-parameter foundation model. The numerical solution of the complete contact problem is straightforward. However, it is shown that the problem displays a highly non-linear character when the beam lifts off from the foundation. Numerical treatment of the governing equations is accomplished by adopting an iterative process to establish the contact length. Results are presented in figures to demonstrate the linear and non-linear behavior of the beam-foundation system for various values of the parameters of the problem comparatively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.695-700
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• 2000

The dynamic stability of spinning beam with free boundary conditions for both edges subjected to a tip follower force $P_0+P_1cos{\Omega}t$ is analyzed. It is studied that the beam has a concentrated mass. and then the effects of the axial locations of the mass are studied. The beam is modelled with the Timoshenko type shear deformations. The Hamilton's principle is used to derive the equations of motion, and the critical spinning speed of a beam subjected to a follower force with various non-dimensional parameters is investigated. The finite elements are used with $C^0$ continuity to analyze the spinning beam model, and the method of multiple scales is tried to investigate the dynamic instability regions. The governing equations of motion involve periodic coefficients, which are not in the form of standard Mathieu-Hill equations. The result shows that the concentrated mass increases the dynamic stability of the spinning free-free beam subjected to a thrust.

• Smart Structures and Systems
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• 제1권3호
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• pp.283-308
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• 2005

This paper features about the modeling and design of a fast output sampling feedback controller for a smart Timoshenko beam system for a SISO case by considering the first 3 vibratory modes. The beam structure is modeled in state space form using FEM technique and the Timoshenko beam theory by dividing the beam into 4 finite elements and placing the piezoelectric sensor/actuator at one location as a collocated pair, i.e., as surface mounted sensor/actuator, say, at FE position 2. State space models are developed for various aspect ratios by considering the shear effects and the axial displacements. The effects of changing the aspect ratio on the master structure is observed and the performance of the designed FOS controller on the beam system is evaluated for vibration control.