A new hierarchic degenerated shell element for geometrically non-linear analysis of composite laminated square and skew plates

우광성,Jin-Hwan Park,홍종현 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.6

This paper extends the use of the hierarchic degenerated shell element to geometric non-linear analysis of composite laminated skew plates by the p-version of the finite element method. For thegeometric non-linear analysis, the total Lagrangian formulation is adopted with moderately largedisplacement and small strain being accounted for in the sense of von Karman hypothesis. The presentmodel is based on equivalent-single layer laminate theory with the first order shear deformation includinga shear correction factor of 5/6. The integrals of Legendre polynomials are used for shape functions withp-level varying from 1 to 10. A wide variety of linear and non-linear results obtained by the p-versionfinite element model are presented for the laminated skew plates as well as laminated square plates. Anumerical analysis is made to illustrate the influence of the geometric non-linear effect on the transversedeflections and the stresses with respect to width/depth ratio (a/h), skew angle (b), and stacking sequenceof layers. The present results are in good agreement with the results in literatures.

Piecewise exact solution for seismic mitigation analysis of bridges equipped with sliding-type isolators

C.S. Tsai,Yung-Chang Lin,Wen-Shin Chen,Tsu-Cheng Chiang,Bo-Jen Chen 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.2

Recently, earthquake proof technology has been widely applied to both new and existing structures and bridges. The analysis of bridge systems equipped with structural control devices, which possess large degrees of freedom and nonlinear characteristics, is a result in time-consuming task. Therefore, a piecewise exact solution is proposed in this study to simplify the seismic mitigation analysis process for bridge systems equipped with sliding-type isolators. In this study, the simplified system having two degrees of freedom, to reasonably represent the large number of degrees of freedom of a bridge, and is modeled to obtain a piecewise exact solution for system responses during earthquakes. Simultaneously, we used the nonlinear finite element computer program to analyze he bridge responses and verify the accuracy of the proposed piecewise exact solution for bridge systems equipped with sliding-type isolators. The conclusions derived by comparing the results obtained from the piecewise exact solution and nonlinear finite element analysis reveal that the proposed solution not only simplifies the calculation process but also provides highly accurate seismic responses of isolated bridges under earthquakes.

Weighted sum Pareto optimization of a three dimensional passenger vehicle suspension model using NSGA-II for ride comfort and ride safety

Bagheri, Mohammad Reza,Mosayebi, Masoud,Mahdian, Asghar,Keshavarzi, Ahmad 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.4

The present research study utilizes a multi-objective optimization method for Pareto optimization of an eight-degree of freedom full vehicle vibration model, adopting a non-dominated sorting genetic algorithm II (NSGA-II). In this research, a full set of ride comfort as well as ride safety parameters are considered as objective functions. These objective functions are divided in to two groups (ride comfort group and ride safety group) where the ones in one group are in conflict with those in the other. Also, in this research, a special optimizing technique and combinational method consisting of weighted sum method and Pareto optimization are applied to transform Pareto double-objective optimization to Pareto full-objective optimization which can simultaneously minimize all objectives. Using this technique, the full set of ride parameters of three dimensional vehicle model are minimizing simultaneously. In derived Pareto front, unique trade-off design points can selected which are non-dominated solutions of optimizing the weighted sum comfort parameters versus weighted sum safety parameters. The comparison of the obtained results with those reported in the literature, demonstrates the distinction and comprehensiveness of the results arrived in the present study.

Multi-objective optimization of double wishbone suspension of a kinestatic vehicle model for handling and stability improvement

Mohammad Reza Bagheri,Masoud Mosayebi,Asghar Mahdian,Ahmad Keshavarzi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.5

One of the important problems in the vehicle design is vehicle handling and stability. Effective parameters which should be considered in the vehicle handling and stability are roll angle, camber angle and scrub radius. In this paper, a planar vehicle model is considered that two right and left suspensions are double wishbone suspension system. For a better analysis of the suspension geometry, a kinestatic model of vehicle is considered which instantaneous kinematic and statics relations are analyzed simultaneously. In this model, suspension geometry is considered completely. In order to optimum design of double wishbones suspension system, a multi-objective genetic algorithm is applied. Three important parameters of suspension including roll angle, camber angle and scrub radius are taken into account as objective functions. Coordinates of suspension hard points are design variables of optimization which optimum values of them, corresponding to each optimum point, are obtained in the optimization process. Pareto solutions for three objective functions are derived. There are important optimum points in these Pareto solutions which each point represents an optimum status in the model. In other words, corresponding to any optimal point, a specific geometric position is determined for the suspension hard points. Each of the obtained points in the Pareto optimization can be selected for a special design purpose by designer to create an optimum condition in the vehicle handling and stability.

Optimization of the braced dome structures by using Jaya algorithm with frequency constraints

Maksym Grzywiński,Tayfun Dede,Yaprak Itır Özdemír 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.1

The aim of this paper is to present new and an efficient optimization algorithm called Jaya for the optimum mass of braced dome structures with natural frequency constraints. Design variables of the bar cross-section area and coordinates of the structure nodes were used for size and shape optimization, respectively. The effectiveness of Jaya algorithm is demonstrated through three benchmark braced domes (52-bar, 120-bar, and 600-bar). The algorithm applied is an effective tool for finding the optimum design of structures with frequency constraints. The Jaya algorithm has been programmed in MATLAB to optimize braced dome.

Study of buckling stability of cracked plates under uniaxial compression using singular FEM

Sina Saberi,Parham Memarzadeh,Tadeh Zirakian 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.4

Buckling is one of the major causes of failure in thin-walled plate members and the presence of cracks with different lengths and locations in such structures may adversely affect this phenomenon. This study focuses on the buckling stability assessment of centrally and non-centrally cracked plates with small-, intermediate-, and large-size cracks, and different aspect ratios as well as support conditions, subjected to uniaxial compression. To this end, numerical models of the cracked plates were created through singular finite element method using a computational code developed in MATLAB. Eigen-buckling analyses were also performed to study the stability behavior of the plates. The numerical results and findings of this research demonstrate the effectiveness of the crack length and location on the buckling capacity of thin plates; however, the degree of efficacy of these parameters in plates with various aspect ratios and support conditions is found to be significantly different. Overall, careful consideration of the aspect ratio, support conditions, and crack parameters in buckling analysis of plates is crucial for efficient stability design and successful application of such thin-walled members.

Nonlocal nonlinear stability of higher-order porous beams via Chebyshev-Ritz method

Ridha A. Ahmed,Nader M. Mustafa,Nadhim M. Faleh,Raad M. Fenjan 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.3

Considering inverse cotangential shear strain function, the present paper studies nonlinear stability of nonlocal higherorder refined beams made of metal foams based on Chebyshev-Ritz method. Based on inverse cotangential beam model, it is feasible to incorporate shear deformations needless of shear correction factor. Metal foam is supposed to contain different distributions of pores across the beam thickness. Also, presented Chebyshev-Ritz method can provide a unified solution for considering various boundary conditions based on simply-supported and clamped edges. Nonlinear effects have been included based upon von-karman’s assumption and nonlinear elastic foundation. The buckling curves are shown to be affected by pore distribution, geometric imperfection of the beam, nonlocal scale factor, foundation and geometrical factors.

Holder exponent analysis for discontinuity detection

A. N. Robertson,손훈,C. R. Farrar 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3-4

Free vibration of laminated composite skew plates with central cutouts

이상열,박대효 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.5

We performed a free vibration analysis of skew composite laminates with or without cutout based on the high-order shear deformation plate theory (HSDT). The effects of skew angles and ply orientations on the natural frequencies for various boundary conditions are studied using a nonlinear highorder finite element program developed for this study. The numerical results are in good agreement with those reported by other investigators for simple test cases, and the new results reported in this paper show the interactions between the skew angle, layup sequence and cutout size on the free vibration of the laminate. The findings highlight the importance of skew angles when analyzing laminated composite skew plates with cutout or without cutout.

Nonlinear time-varying analysis algorithms for modeling the behavior of complex rigid long-span steel structures during construction processes

Li-Min Tian,Ji-Ping Hao 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.5

There is a great difference in mechanical behavior between design model one-time loading and step-by-step construction process. This paper presents practical computational methods for simulating the structural behavior of long-span rigid steel structures during construction processes. It introduces the positioning principle of node rectification for installation which is especially suitable for rigid long-span steel structures. Novel improved nonlinear analytical methods, known as element birth and death of node rectification, are introduced based on several calculating methods, as well as a forward iteration of node rectification method. These methods proposed in this paper can solve the problem of element's 'floating' and can be easily incorporated in commercial finite element software. These proposed methods were eventually implemented in the computer simulation and analysis of the main stadium for the Universiade Sports Center during the construction process. The optimum construction scheme of the structure is determined by the improved algorithm and the computational results matched well with the measured values in the project, thus indicating that the novel nonlinear time-varying analysis approach is effective construction simulation of complex rigid long-span steel structures and provides useful reference for future design and construction.