• Structural Engineering and Mechanics
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• 제81권6호
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• pp.705-714
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• 2022

The aim of this paper is to investigate nonlinear dynamic responses of functionally graded composite beam resting on the nonlinear viscoelastic foundation subjected to moving mass with temperature rising. The non-linear strain-displacement relationship is considered in the finite strain theory and the governing nonlinear dynamic equation is obtained by using the Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then the governing equation is solved by using of multiple time scale method. The influences of temperature rising, material distribution parameter, nonlinear viscoelastic foundation parameters, magnitude and velocity of the moving mass on the nonlinear dynamic responses are investigated. Also, the buckling temperatures of the functionally graded beams based on the finite strain theory are obtained.

• Structural Engineering and Mechanics
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• 제53권4호
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• pp.661-679
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• 2015

In this article, nonlinear finite element solutions of bending responses of functionally graded spherical panels are presented. The material properties of functionally graded material are graded in thickness direction according to a power-law distribution of volume fractions. A general nonlinear mathematical shallow shell model has been developed based on higher order shear deformation theory by taking the geometric nonlinearity in Green-Lagrange sense. The model is discretised using finite element steps and the governing equations are obtained through variational principle. The nonlinear responses are evaluated through a direct iterative method. The model is validated by comparing the responses with the available published literatures. The efficacy of present model has also been established by demonstrating a simulation based nonlinear model developed in ANSYS environment. The effects of power-law indices, support conditions and different geometrical parameters on bending behaviour of functionally graded shells are obtained and discussed in detail.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.409-421
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• 2019

Investigation of hydroelastic responses of high-speed vessels in irregular sea state is of major interest in naval applications. A three dimensional nonlinear time-domain hydroelastic method in oblique irregular waves is developed, in which the nonlinear hydrostatic restoring force caused by instantaneous wetted surface and slamming force are considered. In order to solve the two technical problems caused by irregular sea state, the time-domain retardation function and Proportional, Integral and Derivative (PID) autopilot model are applied respectively. Besides, segmented model tests of a high-speed trimaran in oblique waves are performed. An oblique wave testing system for trimarans is designed and assembled. The measured results of main hull and cross-decks are analyzed, and the differences in distribution of load responses between trimarans and monohull ships are discussed. Finally, from the comparisons, it is confirmed that the present concept for dealing with nonlinear hydroelastic responses of ships in oblique irregular waves is reliable and accurate.

• Smart Structures and Systems
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• 제15권2호
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• pp.409-424
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• 2015

Structural nonlinearity is a common phenomenon encountered in engineering structures under severe dynamic loading. It is necessary to localize and identify structural nonlinearities using structural dynamic measurements for damage detection and performance evaluation of structures. However, identification of nonlinear structural systems is a difficult task, especially when proper mathematical models for structural nonlinear behaviors are not available. In prior studies on nonparametric identification of nonlinear structures, the locations of structural nonlinearities are usually assumed known and all structural responses are measured. In this paper, an identification algorithm is proposed for locating and identifying model-free structural nonlinearities and systems using incomplete measurements of structural responses. First, equivalent linear structural systems are established and identified by the extended Kalman filter (EKF). The locations of structural nonlinearities are identified. Then, the model-free structural nonlinear restoring forces are approximated by power series polynomial models. The unscented Kalman filter (UKF) is utilized to identify structural nonlinear restoring forces and structural systems. Both numerical simulation examples and experimental test of a multi-story shear building with a MR damper are used to validate the proposed algorithm.

• Structural Engineering and Mechanics
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• 제30권1호
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• pp.37-66
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• 2008

This paper focuses on the nonlinear vibrations of stay cables and evaluates the dynamic characteristics of stay cables by using the nonlinear enhanced MECS approach and the approximate approach. The nonlinear enhanced MECS approach is that both the girder-tower vibrations and the cable vibrations including parametric cable vibrations are simultaneously considered in the numerical analysis of cable-stayed bridges. Cable finite element method is used to simulate the responses including the parametric vibrations of stay cables. The approximate approach is based on the assumption that cable vibrations have a small effect on girder-tower vibrations, and analyzes the local cable vibrations after obtaining the girder-tower responses. Under the periodic excitations or the moderate ground motion, the differences of the responses of stay cables between these two approaches are evaluated in detail. The effect of cable vibrations on the girder and towers are also discussed. As a result, the dynamic characteristics of the parametric vibrations in stay cables can be evaluated by using the approximate approach or the nonlinear enhanced MECS approach. Since the different axial force fluctuant of stay cables in both ends of one girder causes the difference response values between two approach, it had better use the nonlinear enhanced MECS approach to perform the dynamic analyses of cable-stayed bridges.

• Smart Structures and Systems
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• 제16권1호
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• pp.195-211
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• 2015

This paper presents nonlinear analysis of a functionally graded square plate integrated with two functionally graded piezoelectric layers resting on the Winkler-Pasternak foundation. Geometric nonlinearity was considered in the strain-displacement relation based on the Von-Karman assumption. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness of the plate based on a power function. Electric potential was assumed as a quadratic function along the thickness direction and trigonometric function along the planar coordinate. The effect of non homogeneous index was investigated on the responses of the system. Furthermore, a comprehensive investigation has been performed for studying the effect of two parameters of assumed foundation on the mechanical and electrical components. A comparison between linear and nonlinear responses of the system presents necessity of this study.

• Earthquakes and Structures
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• 제18권6호
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• pp.667-675
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• 2020

The current study compares the effect of structure-soil-structure interaction (SSSI) on the dynamic responses of adjacent buildings and isolated structures including soil-structure interaction (SSI) with the responses of fixed-base structures. Structural responses such as the relative acceleration, displacement, drift and shear force were considered under earthquake ground motion excitation. For this purpose, 5-, 10- and 15-story structures with 2-bay moment resisting frames resting on shallow foundations were modeled as a group of buildings in soft soil media. Viscous lateral boundaries and interface elements were applied to the soil model to simulate semi-infinite soil media, frictional contact and probable slip under seismic excitation. The direct method was employed for fully nonlinear time-history dynamic analysis in OpenSees using 3D finite element soil-structure models with different building positions. The results showed that the responses of the grouped structures were strongly influenced by the adjacent structures. The responses were as much as 4 times greater for drift and 2.3 times greater for shear force than the responses of fixed-base models.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.313-320
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• 2003

The responses of a 1:5 scale 3-story masonry-infilled RC frame which was designed only for gravity loads were simulated by using a nonlinear analysis program, DRAIN-2DX. The objective of this study is to verify the correlation between the experimental and analytical responses of a masonry-infilled RC frame. It is concluded from this comparison that the strength and stiffness of the whole structure can be predicted with quite high reliability using compressive strut (compression link element, Type 09).

• 한국전산구조공학회논문집
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• 제29권4호
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• pp.317-325
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• 2016

이 연구에서는 3축 방향 지반운동이 작용하는 지반-구조물 상호작용계의 비선형 지진응답 해석을 수행한다. 비선형 거동이 예상되는 구조물과 지반의 근역은 비선형 유한요소에 의해 모형을 구성한다. 기하학적 형상과 재료 성질이 균일하고 선형 거동을 가정하는 원역지반은 무한 영역으로의 에너지 방사를 정확히 고려할 수 있는 3차원 perfectly matched discrete layer에 의해 수치 모형을 구성한다. 이와 같은 지반-구조물 상호작용계의 수치모형을 사용하여 3축 방향 지반운동이 작용하는 비선형 지진-구조물 상호작용계의 지진응답해석을 수행한다. 3축 방향 지반운동이 작용하는 경우에는 입력 지반운동의 특성에 따라 시스템의 응답이 우세하게 발현되는 방향이 존재하고 그 수준 또한 정밀한 지진응답해석을 통해 산정하여야 한다. 이 연구의 해석기법은 구조물과 지반의 재료 비선형 거동, 기초와 지반 경계면에서의 경계 비선형 거동 등 다양한 비선형 지반-구조물 상호작용 해석에 확장 적용할 수 있을 것이다.

• 한국해양공학회지
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• 제20권5호
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• pp.30-35
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• 2006

In tire presence of incident waves with different frequencies, there are second order sum and difference frequency wave exciting forces due to the nonlinearity of tire incident waves. Although the magnitude of these nonlinear wave forces are small, they act on TLPs at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency waveexciting forces occurring close to tire natural frequencies of TLPs often give greater contributions to high and law frequency resonant responses. Nonlinear motion responses and tension variations in the time domain are analyzed by solving the motion equations with nonlinear wave exciting forces using tire numerical analysismethod. The numerical results of time domain analysis for the nonlinear wave exciting forces on the ISSC TLP in regular waves are compared with the numerical and experimental ones of frequency domain analysis. The results of this comparison confirmed tire validity of the proposed approach.