Proceedings of the Computational Structural Engineering Institute Conference (한국전산구조공학회:학술대회논문집)
Computational Structural Engineering Institute of Korea (한국전산구조공학회)
 Semi Annual
Domain
 Construction/Transportation ＞ Design/Analysis for Facilities
2002.04

A momentcurvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous momentcurvature models and the layered section approach, the unposed model takes into account the bondslip effect by using a monotonic momentcurvature relationship constructed on the basis of the bondslip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stressstrain relation of steel gives more exact numerical result. The pinching enact caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial force. The advantages of the proposed model, comparing tn layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures.. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed mood.

For the analysis of Kirchhoff plate bending problems, a new meshless method is implemented. For the satisfaction of the C¹ continuity condition in which the first derivative is treated as another primary variable, Hermite interpolation is enforced on standard reproducing kernel particle method. In order to impose essential boundary conditions on solving C¹ continuity problems, shape function modifications are adopted. Through numerical tests, the characteristics and accuracy of the HRKPM are investigated and compared with the finite element analysis. By this implementation, it is shown that high accuracy is achieved by using HRKPM fur solving Kirchhoff plate bending problems.

In this paper, the nonlinear structural analysis for the composite structure of the spent nuclear fuel disposal container and the 50cm thick bentonite buffer is carried out to predict the collapse of the container while the sudden rock movement of 10cm is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Horizontal symmetric rock movement is assumed in this structural analysis. Elastoplastic material model is adopted. DruckerPrager yield criterion is used for the material yield prediction of the bentonite buffer and vonMises yield criterion is used for the material yield prediction of the container(cast iron insert, copper outer shell and lid and bottom). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffer, the container structure still endures elastic small strains and stresses below the yield strength. Hence, the 50cm thick bentonite buffer can protect the container safely against the 10cm sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the container structure due to the shear deformation of the bentonite buffer. The elastoplastic nonlinear structural analysis for the composite structure of the container and the bentonite buffer is performed using the finite element analysis code, NISA.

In the case of reinforced concrete structures, the knowledge of load transfer in the longterm behavior analysis considering construction sequence is very important. Even though longterm behavior of concrete structures has been widely studied, the studies on the timedependent axial force variation of shore have been scarce to date. In order to investigate the shore behaviors under actual construction conditions, a threestory test frame was constructed on a construction site. The entire construction schedule for the test frame was made to follow the schedule of an actual threestory frame. To analyze the data collected from the test frame, an analysis method based on the Winkler foundation model was developed. This analysis method accurately Predicts the timedependent behavior of shore. The analysis results coincide well with those obtained by the Midas GENw program

In this paper, effective analysis of beam is studied using the RKPM in meshless methods. So, RKPM is extended for solving moderately thick and thin beam. General Timoshenko beam theory is used for formulation. Shear locking is the main difficulty in analysis of beam structures. The shear relaxation factor and corrected shear rigidity are introduced to overcome shear locking. Analysis results obtained reveal that RKPM using introduced methods Is free of locking and very effectively applicable to deeply as well as shallowly beams.

Main goal of this study is to develop MATLAB programming for exact analysis of distortional deformation of the straight box girder. For this purpose, a theory for distortional deformation theory is firstly summarized and then a BEF (Beam on Elastic Foundation) theory is presented using analogy of the corresponding variables. Finally, the governing equation of the beamcolumn element on elastic foundation is derived. An element stiffness matrix of the beam element is established via a generalized linear eigenvalue problem. In order to verify the efficiency and accuracy of the element using exact dynamic stiffness matrix, buckling loads for the continuous beam structures with elastic foundation and distortional deformations of box girders are calculated.

It has been recognized that damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the inelastic response is required. The methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. Some codes proposed the capacity spectrum method based on the nonlinear static(pushover) analysis to determine earthquakeinduced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method to evaluate seismic Performance of structure, without iterative computations, given the structural initial elastic period and yield strength from the pushover analysis, especially for multi degree of freedom structures. The purpose of this paper is to investigate accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters.

Tubular members have been applied in a wide range of frame structures including offshore structures. For the efficient load flow in tubularmember structures, the joints of tubular members are usually reinforced using internal ring stiffener for the steel tubular joint having a large diameter. The objective of this paper is to numerically assess the behavior of Xjoints with an internal ring stiffener, and to evaluate the reinforcement effect of a ring stiffener, and to establish the strength formulae. Nonlinear finite element analysis is used to compute the static strength of axially loaded tubular joints. From the numerical results, internal ring stiffener is found to be efficient in improving static strength of tubular Xjoints. Maximum strength ratios are calculated as 1.5~3.5, and the effective dimensions of ring stiffener are found. Regression analyses are performed considering practical size of ring stiffener and strength estimation formulae are proposed.

In this paper, several improved ElementFree Galerkin (EFG) methods containing singular expression in their approximation functions are compared one another through a patch test with neartip field. Intrinsic enrichments that expand the basis function partially and fully with known neartip displacement field and a local enrichment using auxiliary supports based on the partition of unity concept are examined by evaluating a relative stress norm error and the stress intensity factor. Some numerical examinations graphically show that how the size of compact support, dilation parameter and the diffraction parameter can affect the accuracy of the improved EFG methods in the error and the stress intensity factor.

Recently, adapt cases of concrete structure are increasing according to structural largeness and variety. We energetically continue to study empirical research about Steel Fiber but analytic research of Twospans Beam With Steel Fiber to model real structure is just beginning stage. This study will suggest analytic algorithm of Twospans Beam With Steel Fiber by comparing and analyzing deflection and strain of Twospans Beam With Steel Fiber after we develop Nonlinear Analysis Program considering edge stress analysis.

Prying action caused by the eccentric loads within the equipment itself and the anchors can result in a lack of adequate stiffness and strength within the equipment and in additional moment loadings on the anchors. A typical case of prying action often found in power plants is the angle type anchorage system with expansion bolt. Experimental and analytical studies were performed to investigate the relationship between the amplification factors and various geometrical and material factors. It is revealed that the value of the factor is effected by the stiffness of bolt and angle, lateral stiffness of cabinet, and geometrical parameter of anchor system.

This study presents a new method to derive the constraint coefficient from the degree of angular deformation caused by welding, as measured experimentally by varying the shape of welded joints and the magnitude of constraints and from analysis results given by the elastic FEM method. The equivalent load was then calculated with this constraint coefficient. The validity of the numerical analysis involved in this new method was confirmed by its agreement with the experimental results. As for the effects of the constraints based on the shape of the welded joints in the case of Butt welding when the constraint coefficients are not considered, the deformed quantity produced by analysis is larger that produced by experiment and consequently is largely affected by the constraints.

This paper presents an analytical investigation on the behavior of simple span integral abutment bridge. An integral abutment bridge is a simple span or multiple span continuous deck type bridge having the deck integral with the abutment wall. Although the temperature variation and earth pressure are the major attributor to the total stress in integral abutment bridge, the superstructure has been designed by modeling it as a simple or continuous beam In order to investigate the effect of temperature change and earth pressure on the superstructure of integral bridge, the simple span integral bridge is modeled as a plane frame element. Performing frame analysis, the variations of bending moment and axial force of superstructure due to the various loading combination are investigated with respect to the flexural rigidity of piles, and the bending moment and axial force obtained by frame analysis are compared with the maximum bending moment obtained by conventional design method and initial prestressing force respectively.

This paper deals with the nonlinear analysis of cantilever beams with constant volume. Numerical methods are developed for solving the elastica of cantilever ben subjected to a tip Point load and a tip couple. The linear, parabolic and sinusoidal tapers with the regular polygon crosssection are considered, whose material volume and span length are always held constant. The RungeKutta and RegulaFalsi methods, respectively, are used to integrate the governing differential equations and to compute the unknown value of the tip deflection. The numerical results obtained herein are shown in tables and figures. Also the shapes of strongest beams are determined by reading the minimum values form the deflection versus section ratio curves.

The main purpose of this paper is to determine the static optimal shapes of tapered beams with constant volume. The linear, parabolic and sinusoidal tapers with the regular polygon crosssection are considered, whose material volume and span length are always held constant. The RungeKutta method is used to integrate the differential equation and also Shooting method is used to calculate the unknown boundary condition. Then the static optimal shapes are determined by reading the minimum values of the deflection versus section ratio curves plotted by the deflection data. In numerical examples, the various tapered beams are analyzed and those numerical results of this study are shown in figures.

A general formulation for shape design sensitivity analysis over three dimensional beam structure is developed based on a variational formulation of the beam in linear elasticity. Sensitivity formula is derived based on variational equations in cartesian coordinates using the material derivative concept and adjoint variable method for the displacement and VonMises stress functionals. Shape variation is considered for the beam shape in general 3dimensional direction as well as for the orientation angle of the beam cross section. In the sensitivity expression, the end points evaluation at each beam segment is added to the integral formula, which are summed over the entire structure. The sensitivity formula can be evaluated with generality and ease even by employing piecewise linear design velocity field despite the bending model is fourth order differential equation. For the numerical implementation, commercial software ANSYS is used as analysis tool for the primal and adjoint analysis. Once the design variable set is defined using ANSYS language, shape and orientation variation vector at each node is generated by making finite difference to the shape with respect to each design parameter, and is used for the computation of sensitivity formula. Several numerical examples are taken to show the advantage of the method, in which the accuracy of the sensitivity is evaluated. The results are found excellent even by employing a simple linear function for the design velocity evaluation. Shape optimization is carried out for the geometric design of an archgrid and tilted bridge, which is to minimize maximum stress over the structure while maintaining constant weight. In conclusion, the proposed formulation is a useful and easy tool in finding optimum shape in a variety of the spatial frame structures.

This paper investigates the applicability of the modified Lanczos method using the power technique, which was developed in the field of quantum physics, to the eigenproblem in the field of engineering mechanics by introducing matrixpowered Lanczos recursion and numerically evaluating the suitable power value. The matrixpowered Lanczos method has better convergence and less operation count than the conventional Lanczos method. By analyzing four numerical examples, the effectiveness of the matrixpowered Lanczos method is verified and the appropriate matrix power is also recommended.

MR 유체 감쇠기는 구조물의 진동을 감소시키기 위한 가장 유망하고 새로운 제진 (制振) 장치 중 하나이다. 이 장치는 기계적인 단순성, 높은 동적 범위, 적은 전력 요구량, 커다란 감쇠 능력, 강인성 등의 장점을 가지고 있기 때문에, 토목 구조 시스템의 내진(耐震) 및 내풍(耐風) 성능을 향상시키는데 매우 유용하다. 많은 연구자들이 MR 유체 감쇠기의 유사정적 모델을 연구했지만 그 모델이 감쇠기의 설계를 위해서는 유용하다고 하더라도, 동적 하중에 대한 감쇠기의 거동을 모사하는 데는 충분하지 않다. 논문에서는 대용량 20톤 MR 유체 감쇠기의 동적하중에 대한 응답 해석 결과를 이용하여, BoucWen 모델을 기반으로 하는 새로운 역학적 모델을 제안하였다. 이 모델은 MR 유체의 stiction현상과 관성 및 shear thinning 효과를 잘 묘사한다. 또한, 제안된 MR 유체 감쇠기의 동적 모델이 실험 결과와 매우 잘 일치함을 보였다.

This paper examines the ASCE first generation benchmark problem for a seismically excited cablestayed bridge, and proposes a new semiactive control strategy focusing on inclusion of effects of control structure interaction. In this study, magnetorheological (MR) fluid dampers, which belong to the class of controllable fluid dampers, are proposed as the supplemental damping devices, and a clippedoptimal control algorithm, shown to perform well in previous studies involving MR fluid dampers, is employed. The dynamic model for MR fluid dampers is considered as a modified BoucWen model, which is obtained from data based on experimental results for largescale dampers. Numerical results show that the performance of the proposed semiactive control strategy using MR fluid dampers is quite effective.

The seismic excitation test results of an isolated test structure for artificial time history excitation are summarized for structural modeling of the isolated structure and isolation bearing. Based on the actual dynamic behaviors and the seismic responses of the test model, linear and bilinear models for isolators are suggested. Seismic analyses are performed and compared with those of the seismic tests. The developed bilinear model is well applicable only to large shear strain area of isolators.

Seismic bridge failure due to the combined effects of earthquake and local scour are examined in probabilistic perspectives. The seismic responses of multispan continuous bridge with deep foundations are evaluated with a simplified mechanical model. The probabilistic local scour depths around the deep foundations are estimated by using the Monte Carlo simulation. From the simulation results, it is found that seismic responses of a bridge slightly increase due to the local scour effect. The effect of local scour on the global motion of the continuous bridge is found to be significant under weak seismic intensity. In addition, the duration to regain its original foundation stiffness is critical in estimating the probability of foundation failure under earthquake. Therefore, the duration in recovering the foundation stiffness should be determined reasonably and the safely of the whole bridge system should be evaluated by considering the scour effect.

The paper presents an effective analytical method for SSI systems which can have separation or sliding at the soilstructure interface. The method is based on a hybrid approach which combines a linear SSI code KIESSI2D in frequency domain with a commercial finite element package ANSYS to obtain nonlinear dynamic responses in time domain. The method is applied to a 2D underground box structure which experiences separation and sliding at the soilstructure interface. Material nonlinearity of the concrete structure is also included in the analysis. Effects of the interface conditions are examined and some critical factors affecting the seismic performance of underground structures are identified.

In this study a 3dimensional analytical model is developed, which can analyses dynamic responses of curved bridges subject to moving vehicles. A 5axle semitrailer is modeled to simulate the actual tire forces that are redistributed by vehicle rolling effect due to the centrifugal force. The 1span curved bridge with two steel box girders is modeled using the frame elements. The dynamic response characteristics of curved box girder bridges are examined and compared for two different support conditions. One is the case that two shoes are arranged at the outer sides of box girders with larger space between the two shoes and the other is that two shoes at the center of each box girder. In the curved bridges, the dynamic effect of moving vehicles influences the reaction force much more than other responses, such as displacement or stress, especially the upward reaction of innerradius shoes. It is more advantageous for the reaction considering dynamic effect when shoes are arranged further at the outer sides of box girders than when shoes at the center of each box. The shoes for curved bridges with twobox girder system should be arranged to have larger distance.

The use of frequencydependent dynamic stiffness matrix (or spectral element matrix) in structural dynamics may provide very accurate solutions, while it reduces the number of degreesoffreedom to improve the computational efficiency and cost problems. Thus, this paper develops a spectral element model for the thin plates moving with constant speed under uniform inplane tension. The concept of Kantorovich method is used in the frequencydomain to formulate the dynamic stiffness matrix. The present spectral element model is evaluated by comparing its solutions with the exact analytical solutions. The effects of moving speed and inplane tension on the flexural wave dispersion characteristics and natural frequencies of the plate are numerically investigated.

Energy dissipation capacity and earthquake responses of steel structures installed with unbonded braces(UB) were investigated. Nonlinear dynamic time history analyses were carried out to investigate the seismic response of multistory model structures with UB having various size and strength. Various techniques were applied to determine proper storywise distribution of UB in multistory structures. The analysis results show that the maximum displacements of structures generally decrease as the stiffness of UB increases. However there are cases that the maximum displacement and accumulated damage increases as the stiffness of UB increases, which needs to be checked before deciding proper amount of UB.

Near field ground motions contain distinct, large amplitude pulses in both velocity and displacement. This paper presents an investigation on the characteristics of near filed earthquakes and their effects on seismic demands. For this purpose 20 sets of near field ground motion and 20 sets of far filed ground motion are compared with respect to Linear Elastic Response Spectrum(LERS), Response Modification Factor(R), Inelastic Response Spectrum(IRS), and performance point of Capacity Spectum Method(CSM).

This study introduces a method to generate artificial earthquakes in Korean Peninsular using historical earthquake catalogues and point source model. For this purpose, three earthquake catalogues compiled by different researchers are compared to each other. And epicenters and magnitudes of future earthquakes are generated based on those catalogues. In generating ground motion accelertation, point source model proposed by Boore and Atkinson was adopted. Parameters of the model for SouthEastern part of Korean Peninsular was proposed by Noh and kn. From the epicenters, magnitudes, and ground motion models, possible earthquakes for 50,000 years are generated. Using these generated earthquakes ground accelrations and uniform hazard response spectra (UHRS) having 2%, 5%, and 10% exceedance probability in 50 years are proposed.

Simple genetic algorithm(SGA) has been used to optimize a lot of structural optimization problems because it can optimize nonlinear problems and obtain the global solution. But, because of large evolving populations during many generations, it takes a long time to calculate fitness. Therefore this paper applied microgenetic algorithm(μ GA) to structural optimization and compared results of μ GA with results of SGA. Additionally, the Paper applied μ GA to gate optimization problem for injection molds by using simulation program CAPA.

In this paper, the effects of vehicle loads on flat slab system are investigated on the basis of the previous studies for beamgirder parking structural system. The influence surfaces of flat slab for typical design section are developed for the purpose of obtaining maximum member forces under vehicle loads. In addition, the equivalent vehicle load factors for flat slab parking structures are suggested using artificial neural network. The network responses are compared with the results by numerical analyses to verify the validation of LevenbergMarquardt algorithm adopted as training method in this paper. Many parameter studies fur the flat slab structural system show dominant vehicle load effects at the center positive moments in both column and middle strips, like the beamgirder parking structural system.

Due to many advantages such as light weight, fast installation, high durability, composite bridge deck is considered to be one of the promissing alternatives to concrete bridge deck. The paper presents procedures of finite element analysis and laminate design for composite bridge deck of triangular shape for DB24 load. After design of the section glass reinforced composite deck tube of double triangular section with 200mm profile was fabricated with pultrusion and the procedure are presented.

A new optimization procedure with approximate reanalysis module, using the staged hybrid methods with substructuring, is proposed in is study. In this procedure, displacements are calculated with two step mixed procedures. First step is to introduce the conservative approximation, which is a hybrid form of the linear and reciprocal approximation, as local approximation. In the next step, it is combined with the global approximation by reduced basis approach. The quality of reanalyzed quantities can be greatly improved through these staged hybrid approximations, specially for large changes in the design. Overall procedures are based on substructuring scheme. Several numerical examples illustrate the validity and effectiveness of the proposed methods.

This study presents a lifecycle cost (LCC) effectiveness of a concrete with lightweight aggregate. A number of researchers have made their efforts to develop a lightweight concrete, since it is difficult to apply conventional concrete using general aggregate to heavy selfweight structures such as long span bridges. In this study, an optimum design for minimizing the lifecycle cost of concrete slab bridges is performed to evaluate the life cycle cost effectiveness of the lightweight concrete relative to conventional one from the standpoint of the value engineering. The data of physical properties for new concrete can be obtained from basic experimental researches. The material properties of conventional one are acquired by various reports. This study presents a LCC effectiveness of newly developed concrete, which is made by artificial lightweight aggregate. A number of researchers have made their efforts to develop a lightweight concrete, since it is difficult to apply conventional concrete using general aggregate to heavy selfweight structures such as long span bridges. From the results of the numerical investigation, it may be positively stated that the new concrete lead to, the longer span length, the more economical slab bridges compared with structures using general concrete.

이 논문은 계측신호 분석에 의한 교량구조물의 건전성 모니터링에 관한 것으로, 2 단계 인공신경망을 사용한 구조물의 손상발견 기법에 대하여 제안하고 있다. 첫 번째 단계의 인공신경망은 구조물로부터 측정된 가속도 신호를 입력으로 사용하여 각각의 가속도계로부터 측정된 신호의 변형정도를 나타내는 신호변형지수를 출력하도록 설계되었다. 손상의 발생 여부를 나타내는 첫 번째 단계 인공신경망의 출력값은 다시 두 번째 단계 인공신경망의 입력으로 사용되어 손상의 위치와 정도를 파악하는데 쓰여진다. 모형교량을 사용한 실험으로부터 얻어진 가속도신호를 사용하여 제안된 방법의 타당성을 확인하였으며, 항후 실 교량에 대한 실험을 통하여 현장 적용의 가능성을 확인할 계획이다.

This paper presents an efficient models for reinforeced concrete structures using CARTANFIS(classification and regression treeadaptive neuro fuzzy inference system). a fuzzy decision tree parttitions the input space of a data set into mutually exclusive regions, each of which is assigned a label, a value, or an action to characterize its data points. Fuzzy decision trees used for classification problems are often called fuzzy classification trees, and each terminal node contains a label that indicates the predicted class of a given feature vector. In the same vein, decision trees used for regression problems are often called fuzzy regression trees, and the terminal node labels may be constants or equations that specify the Predicted output value of a given input vector. Note that CART can select relevant inputs and do tree partitioning of the input space, while ANFIS refines the regression and makes it everywhere continuous and smooth. Thus it can be seen that CART and ANFIS are complementary and their combination constitutes a solid approach to fuzzy modeling.

New information technology developments continue to have a significant impact on civil engineering fields. The objective of this study is to develop STEPbased database which will be able to store and manipulate the information of steel bridges over the life cycle. In this study, there are three steps to fulfil the objective to build database and develop the application module for that data model practically and effectively To begin with, STEP methodology for a development of data model has been used for modelling data structure. And then the data model for a steel bridge's shape and structural analysis information has been made up by using AP203 (configuration controlled design) and AP203 (composite and metallic structural analysis and related design) which are the international standard in STEP Lastly, the application module for an access to information of steel bridges has been developed by means of already made database. This study show efficiently the prototype of developing information system with the existing standard technology in civil engineering fields.

In this paper a new damage identification theory is developed in order to identify the locations, severities, and orientations of local damages, all together at a time, by using the frequency response functions measured from damaged plate. Finally, the effects of damage orientation on the vibration responses of a plate are numerically investigated, and the numerically simulated damage identification tests are conducted to verify the present damage identification theory.

Damage estimation methods are classified into two groups according to the dependence on the FE model : signalbased and modelbased methods. Signalbased damage estimation methods are generally appropriate for detection of damage location, whereas not effective for estimation of damage severities. Modelbased damage estimation methods are difficult to apply directly to the structures with a large number of the probable damaged members. It is difficult to obtain the exact model representing the real bridge behavior due to the modeling errors. The modeling errors even may exceed the modal sensitivity on damage. In this study, Modelbased damage detection method which can effectively consider the modeling errors is suggested. Two numerical example analyses on a simple beam and a multigirder bridge are presented to demonstrate the effectiveness of the presented method.

In this study, we developed an analysis method of plate forming by induction heating and verified the effectiveness of the present method through a series of experiments. The phenomena of the induction heating is a 3D transient problem coupled with electromagnetic, heat transfer, and elastoplastic large deformation analyses. To solve the problem, we suggest a proper model and an integrated system. Using the present analysis model, we can estimate the plate deformation in heating without experiments and simulate the plate bending process of induction heating.

A pversion finite element model based on degenerate shell element is proposed for the analysis of orthotropic laminated plates. In the nonlinear formulation of the model, the total Lagrangian formulation is adopted with large deflection and moderate rotation being accounted for in the sense of von Karman hypothesis. The material model Is based on the HuberMises yield criterion and PrandtlReuss flow rule in accordance with the theory of strain hardening yield function, which is generalized for anisotropic materials by introducing the parameters of anisotropy. The model is also based on extension of equivalentsingle layer laminate theory(ESL theory) with shear deformation, leading to continuous shear strain at the interface of two layers. The Integrals of Legendre Polynomials we used for shape functions with plevel varying from 1 to 10. GaussLobatto numerical quadrature is used to calculate the stresses at the nodal points instead of Gauss points. The validity of the proposed pversion finite element model is demonstrated through several comparative points of view in terms of ultimate load, convergence characteristics, nonlinear effect, and shape of plastic zone

The global behavior of tube structures (including tube and tube(s)intube constructions) is investigated for the behavioral characteristics of the structures and their performance in relation to the various structural parameters. The stiffness factor in terms of the axial stiffness of the columns and the bending stiffness of both columns and beams is chosen as a parameter to explain the global behavior of the structures. The shearlag phenomenon is also discussed to explain the general behavior of the structures. Three types of tube structures, with various structural parameters, are analysed for the comparative study, and the results are compared to investigate the structural response and performance of such structures. As a result of the comparison it is obtained that the axial stiffness of the columns is the most important factor governing the response of the tube structures under lateral loading

A continuumbased design sensitivity analysis (DSA) method fur nonshape problems is developed for geometrically nonlinear elastic structures. The nonshape problem is characterized by the design variables that are not associated with the domain of system like sizing, material property, loading, and so on. Total Lagrangian formulation with the GreenLagrange strain and the second PiolaKirchhoff stress is employed to describe the geometrically nonlinear structures. The spatial domain is discretized using the 4node isoparametric plane stress/strain elements. The resulting nonlinear system is solved using the NewtonRaphson iterative method. To take advantage of the derived analytical sensitivity In topology optimization, a fast and efficient design sensitivity analysis method, adjoint variable method, is employed and the material property of each element is selected as nonshape design variable. Combining the design sensitivity analysis method and a gradientbased design optimization algorithm, an automated design optimization method is developed. The comparison of the analytical sensitivity with the finite difference results shows excellent agreement. Also application to the topology design optimization problem suggests a very good insight for the layout design.

The structural stability of pressure housing of SMART CEDM forming pressure boundary must be evaluated. In this paper, the stress and thermal analyses of the upper pressure housing of CEDM are performed for design pressure, hydraulic test pressure and thermal loading. Finite element and boundary condition were generated from the model which is made by IDEAS program and the stress and thermal analyses were performed by ANSYS Program. The upper Pressure housing was analysed using 2D axisymmetric model because it is symmetry about an axis. The stress values obtained by analysis were compared with the stress intensity limit of ASME and KEPIC MNB standard.

The objective of this study is to develop a technique that analyzes the global behavior of frame structures with local cracks. The technique is based on frame analysis and uses the stiffness matrix of cracked frame element. An algorithm proposed here analyzes a frame structure with local transverseedge cracks, considering the effects of crack length and location. Stress intensity factors are employed to calculate additional local compliance due to the cracks based on linear elastic fracture mechanics theory, and then this local compliance is utilized to derive the stiffness matrix of the cracked frame element. In order to verify the accuracy and reliability of the proposed approach, numerical results are compared with those of Finite Element Method for the cracked frame element, and the effects of single crack on the behavior of truss structure are also examined.

A new remeshing algorithm based on the energy minimization is proposed for the finite element method. This utilizes the variation of mapping function between the master and global elements. The resultant equations are only the other form of the governing equations. However the equations have an important information about the relations between the elements. By assuming the solutions of the governing equations, these relations are used very usefully for the mesh optimization. The explicit formulations are presented for the relations of 1dimensional equations and some examples are solved for comparison with the other methods. In addition, 2dimensional expansion is presented for the general use.

The stochastic analysis of semiinfinite domain is presented using the weighted integral method, which is improved to include the higher order terms in expanding the displacement vector. To improve the weighted integral method, the Lagrangian remainder is taken into account in the expansion of the status variable with respect to the mean value of the random variables. In the resulting formulae only the 'proportionality coefficients' are introduced in the resulting equation, therefore no additional computation time and memory requirement is needed. The equations are applied in analyzing the semiinfinite domain. The results obtained by the improved weighted integral method are reasonable and are in good agreement with those of the Monte Carlo simulation. To model the semiinfinite domain, the Bettess's infinite element is adopted, where the theoretical decomposition of the straindisplacement matrix to calculate the deviatoric stiffness of the semiinfinite domains is introduced. The calculated value of mean and the covariance of the displacement are revealed to be larger than those given by the finite domain assumptions which is thought to be rational and should be considered in the design of structures on semiinfinite domains.

In this palter, a finite element technique is applied to both reinforced concrete and prestressed concrete containment vessels to predict the ultimate pressure capacity of the vessels subjected to internal pressure due to accident. The socalled volumecontrol technique is utilized to control the change in volume enclosed by the cylindrical containment vessels and layered shell elements equipped with a pressure node is utilizing to model the PSC vessels. The finite element analysis is carried out to obtain both global and local failure behavior of prestressed concrete nuclear containment vessels. nalytical results are verified by comparison with experimental data.

Derivation procedures of exact elastic element stiffness matrix of thinwalled curved beams are rigorously presented for the static analysis. An exact elastic element stiffness matrix is established from governing equations for a uniform curved beam element with nonsymmetric thinwalled cross section. First this numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. Thus, the displacement functions of displacement parameters are exactly derived and finally exact stiffness matrices are determined using member forcedisplacement relationships. The displacement and normal stress of the section are evaluated and compared with thinwalled straight and curved beam element or results of the analysis using shell elements for the thinwalled curved beam structure in order to demonstrate the validity of this study.

Epoxy coating and sealing used in nuclear plants for the protection of radiation degrades with aging and hazardous atmosphere. In order to evaluate the degradation of the epoxy, dependence of the acoustic impedance on the change of mechanical properties has been used. Unlike metals, the surface of the epoxy coating on a concrete liner is so wavy that the acoustic impedance is difficult to measure by using the reflectivity of the ultrasound on the interface surface because of the irregular reflection and propagation from the epoxy surface. SA(simulated annealing) algorithm is applied to calculate the acoustic impedance using a reflection wave from the rough epoxy surface. The surface waviness and acoustic impedance are taken into account and determined by SA method to evaluate the state of degradation quantitatively.

A numerical model is introduced to simulate propagation, reflection, and scattering of elastic waves in solids. The model consists of mass points and linear springs, interconnected with in a lattice structure; hence, its name, the massspring lattice model (MSLM). The MSLM has successfully been applied to the numerical simulation and visualization of various elastic wave phenomena involved in ultrasonic nondestructive testing (NDT). This method is useful to simulate, design, or analyze actual testing. Some representative examples of numerical simulation using the MSLM are presented, and future work necessary for its further development Is addressed.

The knowledge of interaction of electromagnetic waves in composite structures is important for designing the shielding structure for antenna such as radome. Recently, radomes are constructed in the form of foam core sandwich structures that have many mechanical advantages such as high strength, long fatigue life, low density and adaptability to the intended function of structure. However, the propagation of electromagnetic waves is affected by high anisotropic permeability and loss tangent of the composite skin. In this study, the analytical model to understand the propagation of electromagnetic waves in the anisotropic composites and foam core sandwich structures with composite skins was proposed. Numerical analyses of unidirectional composites and foam core sandwich structure as a function of incident angle were performed. From the results of analysis, the general tendencies of transmittance of electromagnetic wave through composites and foam core sandwich structure were obtained.

Various modeling techniques for ultrasonic wave propagation and scattering problems in finite solid media are presented. Elastodynamic boundary value problems in inhomogeneous multilayered platelike structures are set up for modal analysis of guided wave propagation and numerically solved to obtain dispersion curves which show propagation characteristics of guided waves. As a powerful modeling tool to overcome such numerical difficulties in wave scattering problems as the geometrical complexity and mode conversion, the Boundary Element Method(BEM) is introduced and is combined with the normal mode expansion technique to develop the hybrid BEM, an efficient technique for modeling multimode conversion of guided wave scattering problems.

The concept of VDD(Virtual Design & Development) based on high performance computing technology is introduced. The whole process of design and development could be carried out in cyber space through VDD technology in which highprecision simulation technology is combined with virtual reality technology. Therefore, time for design and development of a new product can be shorten and quality of product can be also improved. However, efficient simulation technology must be developed and appropriate supercomputing system must be available to realize VDD technology. In this work, several technologies for obtaining costeffective supercomputing systems for VDD technology are introduced and investigated. The detail informations about optimization technology for PC(Personal Computer) computing, clustering technology, Internet Supercomputing technology, and Piggyback technology are provided and numerical results are also presented.

Piezoelectric solids such as PZT and PLZT have been widely used as sensors or actuators for various smart structural systems. The main problem occurring in the applications is that a larger and larger actuation force is required to maximize the function of the system. This naturally leads to local concentrations of electric or stress fields near crack tips or geometric irregularities and thereby results in a nonlinear behavior of the system Hence, it becomes more important to Predict the nonlinear behavior of piezoelectric solids In this Paper we investigate the micromechanism of nonlinear behavior in piezoelectric materials and propose constitutive equations. The calculation results obtained from an associated finite element Program are shown to be qualitatively consistent with experiments.

This paper deals with a fully coupled piezoelectricmechanical assumed strain solid element that can be used for geometric and material nonlinear modeling of thin piezoelectric actuators. Since the assumed strain solid element can alleviate locking, the element is suitable for performance analysis of very thin actuators without locking. A finite element code is developed based on the finite element formulation and validated by solving typical numerical examples such as bimorph and unimorph beams. Using thecode, we have conducted performance analysis for LIPCA actuator. The estimated actuation displacement of LIPCA agrees well with experimental data under low prescribed voltage.

Possibility of passive piezoelectric damping based on a new shunting parameter estimation method is studied using finite element analysis. The adopted tuning method is based electrical impedance that is found at piezoelectric device and the optimal criterion for maximizing dissipated energy at the shunt circuit. Full three dimensional finite element model is used for piezoelectric devices with cantilever plate structure and shunt electronic circuit is taken into account in the model. Electrical impedance is calculated at the piezoelectric device, which represents the structural behavior in terms of electrical field, and equivalent electrical circuit parameters for the first mode are extracted using PRAP (Piezoelectric Resonance Analysis Program). After the shunt circuit is connected to the equivalent circuit for the first mode, the shunt parameters are optimally decided based on the maximizing dissipated energy criterion. Since this tuning method is based on electrical impedance calculated at piezoelectric device, multimode passive piezoelectric damping can be implemented for arbitrary shaped structures.

The shape memory alloys (SMAs) are often used in smart materials and structures as the active components. Their ability to provide a high recovery force and a large displacement has been used in many applications. In this paper the radial displacement of an externally pressurized elliptic composite cylinder where SMA liner or strips actuators are bonded on its inner or outer surface is investigated numerically. The elliptic composite cylinders consisting of an inlet duct system with SMAs are designed and analyzed to determine the feasibility of such a system for the removal of stiffeners from an externally pressurized duct of an aircraft inlet. The deformations caused by prestrained SMAs placed on either surface of an elliptic composite cylinder are studied when activated. The externally pressurized elliptic composite cylinders with the SMA actuators were analyzed using the 3D finite element method incorporated with 3D SMA behaviors. The results show that the role of stiffeners may be switched by the activated light SMA actuators.

The lateral buckling of a laminated composite beam is studied. A general analytical model applicable to the lateral buckling of a composite beam subjected to various types of loadings is derived. This model is based on the classical lamination theory, and accounts for the material coupling for arbitrary laminate stacking sequence configuration and various boundary conditions. The effects of the location of applied loading on the buckling capacity are also included in the analysis. A displacebased onedimensional finite element model is developed to predict critical loads and corresponding buckling modes for a thinwalled composite beam with arbitrary boundary conditions. Numerical results are obtained for thinwalled composites under central point load, uniformly distributed load, and pure bending with angleply and laminates. The effects of fiber orientation location of applied load, and types of loads on the critical buckling loads are parametrically studied.

In meshless methods, the moving least squares approximation technique is widely used to approximate a solution space because of its useful numerical characters such as nonelement approximation, easily controllable smoothness, and others. In this work, a generalized version of the moving least squares method Is introduced to enhance the approximation performance through the Information converning to the derivative of the field variable. The results of numerical tests for approximation verify the improved accuracy of the generalized meshless approximation procedure compared to the conventional moving least squares method. By using this generalized moving least squares method, meshless analysis of thin beam is carried out, and its performance is investigated.

In the present study, we visualize the linkage framework between geometric modeling and shell finite element based on Bspline representation. For the development of a consistent shell element, geometrically exact shell elements based on general curvilinear coordinates is provided. The NUBS(Non Uniform BSpline) is used to generate the general free form shell surfaces. Employment of NUBS makes shell finite element handle the arbitrary geometry of the smooth shell surfaces. The proposed shell finite element .model linked with NUBS surface representation provides efficiency for the integrated design and analysis of shell surface structures. The linkage framework can potentially provide efficient integrated approach to the shape topological design optimizations for shell structures.

본 연구에서는 임의의 형상의 다중세포 단면을 갖는 복합재료 블레이드에 대한 유한요소 구조해석을 수행하였다. 보 해석 모델은 구조연성 효과와 단면 벽의 두께, 횡 전단변형, 비틀림과 연관된 워핑 및 워핑구속효과 등을 고려하고 있다. 블레이드 힘변위 관계식은 Reissner의 반복족에너지 함수를 이용한 혼합이론을 적용하여 유도하였다. 이 관계식은 굽힘 및 전단에 대해서는 Timoshenko 보의 형태로 그리고 비틀림 변형은 Vlasov 이론으로 근사하고 있다. 결과적인 [7×7] 구조강성 행렬은 전단변형 및 전단강성계수들을 특이한 가정에 의존하지 않고도 해석적으로 기술하고 있다. 본 정식화 과정을 통해서 구한 보 이론을 이중세포로 구성된 에어포일 형상의 복합재료 블레이드에 적용하였으며, 기존의 실험 연구 및 다차원 유한요소해석 결과들과 비교 연구를 수행하여 본 해석모델의 타당성을 보이고자 하였다.