• Smart Structures and Systems
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• 제24권2호
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• pp.267-292
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• 2019

The present article addresses the coupled free vibration problem of skew magneto-electro-elastic plates (SMEE) considering the temperature-moisture dependent material properties. The plate kinematics follows Reddy's higher order shear deformation theory. With the aid of finite element methods, the governing equations of motion are derived considering the Hamilton's principle and solved by adopting condensation technique. The influence of different temperature and moisture dependent empirical constants on the frequency response of SMEE plate has been assessed. In addition, the natural frequencies corresponding to various fields are evaluated and the effect of empirical constants on these coupled frequencies is determined. A detailed parametric study has been carried out to assess the individual effects of temperature and moisture dependent empirical constants along with their combined effect, aspect ratio, length-to-width ratio, stacking sequence and boundary conditions. The results reveal that the external environment as well as the geometrical skewness has a significant influence on the stiffness of the SMEE plates.

• Steel and Composite Structures
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• 제46권4호
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• pp.553-563
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• 2023

In the current research, the nonlinear free vibrations of curved pipes made of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) materials are investigated. It is assumed that the FG-CNTRC curved pipe is supported on a three-parameter nonlinear elastic foundation and is subjected to a uniform temperature rise. Properties of the curved nanocomposite pipe are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite pipe are temperature-dependent. The governing equations of the curved pipe are obtained using a higher order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the pipe. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved nanocomposite pipe. For the case of nanocomposite curved pipes which are simply supported in flexure and axially immovable, the motion equations are solved using the two-step perturbation technique. The closed-form expressions are provided to obtain the small- and large-amplitude frequencies of FG-CNTRC curved pipes rested on a nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of CNT distribution pattern, the CNT volume fraction, thermal environment, nonlinear foundation stiffness, and geometrical parameters on the fundamental linear and nonlinear frequencies of the curved nanocomposite pipe.

• Steel and Composite Structures
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• 제36권4호
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• pp.481-492
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• 2020

To study the rail mapped deformation caused by the pier settlement of simply - supported bridges with China Railway Track System III (CRTS III) slab ballastless track (SBT) system under the mode of non-longitudinal connection ballastless track slab, this study derived an analytical solution to the mapped relationships between pier settlement and rail deformation based on the interlayer interaction mechanism of rail-pier and principle of stationary potential energy. The analytical calculation results were compared with the numerical results obtained by ANSYS finite element calculation, thus verifying the accuracy of analytical method. A parameter analysis was conducted on the key factors in rail mapped deformation such as pier settlement, fastener stiffness, and self-compacting concrete (SCC) stiffness of filling layer. The results indicate that rail deformation is approximately proportional to pier settlement. The smaller the fastener stiffness, the smoother the rail deformation curve and the longer the rail deformation area is. With the increase in the stiffness of SCC filling layer, the maximum positive deformation of rail gradually decreases, and the maximum negative deformation gradually increases. The deformation of rail caused by the pier settlement of common-span bridge structures will generate low-frequency excitation on high-speed trains.

• Coupled systems mechanics
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• 제9권2호
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• pp.147-161
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• 2020

Constructive merging of "basic" systems of different behavior creates hybrid systems. In doing so, the structural elements are grouped according to the behavior in carrying the load into a geometric order that provides sufficient load and structure functionality and optimization of the material consumption. Applicable in all materializations and logical geometric forms is a transparent system suitable for the optimization of load-bearing structures. Research by individual authors gave insight into suitable system constellations from the aspect of load capacity and the approximatemethod of estimating the participation of partialstiffnesswithin the rigidity ofthe hybrid system. The obtained terms will continue to be the basisfor our own research of the influence of variable parameters on the behavior of hybrid systemsformed of glued laminated girder and cable of different geometric shapes. Previous research has shown that by applying the strut-type hybrid systems can increase the load capacity and reduce the deformability ofthe free girder.The implemented parametric analysis pointsto the basic parameterin the behavior of these systems-the rigidity ofindividual elements and the overallstiffnessofthe system.The basic idea ofpre-stressing is that, in the load system or individual load-bearing element, prior to application of the exploitation load, artificially challenge the forcesthatshould optimize the finalsystembehaviorin the overall load. Pre-stressing is possible only if the supporting system orsystem's element possesssufficientstrength orstiffness, orreaction to the imposed forces of pre-stressing. In this paper will be presented own research of the relationship of partial stiffness of strut-type hybrid systemsofdifferentgeometric forms.Conducted parametric analysisofhybridsystemswithandwithoutpre-stressing, and on the example of the glulam-steel strut-type hybrid system under realistic conditions of change in the moisture content ofthe wooden girder,resulted in accurate expressions and diagramssuitable for application in practice.

• 한국지반환경공학회 논문집
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• 제19권2호
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• pp.37-44
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• 2018

자갈궤도는 그 유연성으로 인해 전세계적으로 널리 쓰이고 있다. 그러나 소성 변형이 발생하여 궤도선형오차가 증가하므로 지속적인 유지관리가 필요하며, 최근 통과톤수, 열차중량, 속도 증가 등으로 유지보수 비용과 횟수가 증가하고 있다. 자갈궤도 강성이 거동의 중요 지표로 알려져, 소형동평판시험기(LWD)를 레일과 침목이 체결된 상태에서 실험을 하여 궤도 겉보기 강성을 측정하였다. 예비실험을 통하여 현장시험법을 결정하였고, 측정한 겉보기 강성과 TQI(Track Quality Index), 유지관리지표와의 상관성을 분석한 결과, 평균강성이 증가함에 따라 TQI와 탬핑연장이 지수함수적으로 감소함을 밝혔다. 이로부터 겉보기 강성을 궤도상태지표로써 사용가능함을 제시하였고, 향후 정량적인 유지관리지표를 개발할 수 있을 것으로 기대된다.

• 대한기계학회논문집A
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• 제24권2호
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• pp.362-369
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• 2000

Via screw theory, a vibration mode can be geometrically interpreted as a pure rotation about the vibration center in a plane and as a twisting motion on a screw in a three dimensional space. In thi s paper, applying the conditions that can be used to diagonalize the stiffness matrix by a parallel axis congruence transformation, the vibration modes and frequency response of an elastically suspended optical disc drive have been analyzed. It is first shown that the system has one plane of symmetry, which enables one to decouple the complicated vibration modes into two sets of modes independent of each other. Having obtained the analytical solutions for the axes of vibrations, the frequency response for a given applied input force has been demonstrated. Most importantly, it has been explained that this research result could be used in the synthesis process of a linear vibration system in order to improve the frequency response.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.73-84
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• 2012

This paper strongly addresses to the problem of the mechanical systems in which parameters are uncertain and bounded. Interval calculation is used to find sharp bounds of the structural parameters for infilled frame system modeled with finite element method. Infill walls are generally treated as non-structural elements considerably to improve the lateral stiffness, strength and ductility of the structure together with the frame elements. Because of their complex nature, they are often neglected in the analytical model of building structures. However, in seismic design, ignoring the effect of infill wall in a numerical model does not accurately simulate the physical behavior. In this context, there are still some uncertainties in mechanical and also geometrical properties in the analysis and design procedure of infill walls. Structural uncertainties can be studied with a finite element formulation to determine sharp bounds of the structural parameters such as wall thickness and Young's modulus. In order to accomplish this sharp solution as much as possible, interval finite element approach can be considered, too. The structural parameters can be considered as interval variables by using the interval number, thus the structural stiffness matrix may be divided into the product of two parts which correspond to the interval values and the deterministic value.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.607-612
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• 2004

Disc brake noise continues to be a major concern throughout the automotive industry despite efforts to reduce its occurrence. Eliminating vibrations during braking is an important task for both vehicle passenger comfort and reducing the overall environmental noise levels. There are several classes of disc brake noise, the major ones being squeal, judder, groan, and moan. In this study, analytical model for moan noise of rear disk brake is investigated. Modeling of the disc brake assembly to take account of the effect of different geometrical and contact parameters is studied through the use of multi-body model. The contact stiffness of the caliper and torque member plays an important role in controlling brake vibration. Therefore, a suitable material pair at the caliper/body contact has been made. An ADAMS model of a rear disc brake system was integrated with a flexible suspension trailng arm from MSC/NASTRAN. A fully non-linear dynamic simulatin of brake system behavior, containing rigid and flexible bodies, was performed for a Prescribed set of operating conditions. Simulation results were validated using data from vehicle experimental testing.

• 터널과지하공간
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• 제5권1호
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• pp.1-10
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• 1995

The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

• 국제강구조저널
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• 제18권4호
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• pp.1297-1305
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• 2018

The corrugated steel plate shear walls have recently been proposed to address the seismic issues associated with simple steel plate shear walls; however, stiffness, strength, and ductility of the corrugated shear walls are significantly affected by varying the corrugation geometry under seismic loading. The present study investigates steel shear walls' models with corrugated or simple infill plates subjected to monotonic and cyclic loads. The performance of the corrugated steel plate is evaluated and then compared to that of the simple steel plates by evaluating the damping ratios and energy dissipation capability. The effect of corrugation profile angle, the existence of an opening, and the corrugation subpanel length are numerically investigated after validation of the finite element modeling methodology. The results demonstrate that incorporating corrugated plates would lead to better seismic damping ratios, specifically in the case of opening existence inside of the infill plate. Specifically, the corrugation angle of $30^{\circ}$ decreases the ultimate strength, while increasing the initial stiffness and ductility. In addition, the subpanel length of 100 mm is found to be able to improve the overall performance of shear wall by providing each subpanel appropriate support for the adjacent subpanel, leading to a sufficient buckling resistance performance.