Computational structural engineering is the base on which most of the achievements of engineering and physics are built. Since most of the theory underlying physical phenomena is involved differential equations for which closed forms of solution are seldom possible, the numerical approximation is necessary for a quantitative solution. Some areas where progress and research on computational mechanics are currently active are discussed. In the first part of this paper the development of the improved non-conforming elements for the analysis of plates and shells is described. Recent developments in the adaptive analysis for the structural and the wind problem and meshless method are also discussed in the second part.

It is needless to say that the computer and/or computational engineering has contributed much to the development of the earthquake engineering such as seismic design of structures in providing good tools to researchers and engineers. However, it has been also pointed out that the proper selection of numerical analysis and/or computer program is very important for engineers in utilizing it in the design of structures, because a numerical analysis method is based upon its own coverage. A rigorous analysis does not always gives a correct solution in a sence of engineering or of structural safety, but, some times, it gives mathematically rigorous but unrealistic solution. Therefore, numerical analysis should be performed with engineering judgement or experiments specially in the field of earthquake engineering because this field has large uncertainties on predicting the effect of earthquake on structures. This paper is based on the presented paper at the Bertero Symposium held in January 31an4 February 1 at Berkeley, California, USA which was entitled "Needs to Evaluate Real Seismic Performance of Buildings-Lessons from 1995 Hyogoken-Nambu Earthquake-". The lessons for buildings from the damage due to the Hyogoken-Nambu Earthquake are necessity to develop more rational seismic design codes based upon a performance-based design concept, and to evaluate seismic performance of existing buildings. In my keynote lecture at the Korean Association for Computational Structural Engineering, the history of seismic design and use of structural analysis in Japan, the lessons for buildings from the Hyogoken-Nambu Earthquake, the building damage due to the earthquake, the reasons why the seismic retrofit has not been implemented much, the responses to the lessons from the earthquake, the Network Committee for promotion of seismic retrofit of buildings, the Law for promotion of seismic retrofit of buildings and the implementation of seismic retrofit in Japan are presented.

Most recent seismic design codes include Response Modification Factor(RMF) for determining equivalent lateral forces. The RMF is used to reduce the linear elastic design spectrum to account for the energy dissipation capacity, overstrength and damping of the structure. In this study the RMF is defined as the ratio of the absolute maximum linear elastic base shear to the absolute maximum nonlinear base shear of a structure subject to the same earthquake accelerogram. This study investigates the effect of hysteretic model, as well as target ductility ratio and natural period on duct based RMF using nonlinear dynamic analyses of the SDOF systems. Special emphasis is given to the effects of the hysteretic characteristics such as strength deterioration and stiffness degradation. Results indicate that RMFs are dependent on ductility, period and hysteretic model.

Although a structural analysis based on e linear elastic theory yields good results for deformations and stresses produced by working loads, it fails to assess the teal load-carrying of the plates on the verge of yielding. In case of a limit analysis of plates, the yield line theory is widely used on the basis of the upper bound theorem and theoretically it overestimates the strength of the plate. There is, therefore, a general need for analytical methods of predicting the inelastic behavior and load-carrying capacities of plate subjected to arbitrary loadings and boundary conditions. The $\rho$-version of finite element method has been presented for determining the accurate limit load of plates. The numerical results by $\rho$-version model compares with the results obtained by the h-version software ADINA as well as with the available analytical solutions in literatures.

A volume integral equation method and a mixed volume and boundary integral equation method are presented for the solution of plane elastostatic problems in solids containing orthotropic inclusions and voids. The detailed analysis of the displacement and stress fields are developed for orthotropic cylindrical and elliptic-cylindrical inclusions and voids. The accuracy and effectiveness of the new methods are examined through comparison with results obtained from analytical and boundary integral equation methods. Through the analysis of plane elastostatic problems in unbounded isotropic matrix containing orthotropic inclusions and voids, it is established that these new methods are very accurate and effective for solving plane elastostatic and elastodynamic problems in unbounded solids containing general anisotropic inclusions and voids or cracks.

A new algorithm using meshless particle method for the analysis of crack propagation problems is presented. The meshless particle method requires only a set of nodes and the description of boundaries in its formulation. The method is particulary useful for crack propagation problems due to the absence of any predefined element connectivity. Formulation procedures for the construction of displacement and shape functions are described. A numerical integration scheme and a strategy for the consideration of crack propagation are also described. Numerical examples show that the proposed method is very convenient and efficient in modeling crack problems and can guarantee the accuracy of solution in crack propagation analysis.

This paper deals with the development of a variable-node element and its application to the adaptive h-version mesh refinement-recovery for the incompressible viscous flow analysis. The element which has variable mid-side nodes can be used in generating the transition zone between the refined and unrefined elements and efficiently used for construction of a refined mesh without generating distorted elements. A modified Gaussian quadrature is needed to evaluate the element matrices due to the discontinuity of derivatives of the shape functions used for the element. The penalty function method which can reduce the number of independent variables is adopted for the purpose of computational efficiency and the selective reduced integration is carried out for the convection and pressure terms to preserve the stability of solution. For the economical analysis of transient problems, not only the mesh refinement but also the mesh recovery is needed. The numerical examples show that the optimal mesh for the finite element analysis of a wind around the structures can be obtained automatically by the proposed scheme.

A finite element analysis for physical phenomenon which are governed by parabolic equation, has some inefficiencies caused by much computational time and large storage space. In this paper, a comparative study is performed to suggest the best efficient transient analysis algorithms for parabolic equations. First, the general finite element analysis techniques are summarized in views of formulation procedures, treatments of convection terms. and time stepping methods. Results of several combinations applied to one dimensional convection-diffusion equation and Burger equation are represented and compared using some criteria such as accuracy, stability, and computational time. Through the results, some guidelines to select a algorithm for solving parabolic equations are proposed for diffusion dominant and convection dominant cases. Finally applicability of two dimensional extension of the result is also discussed.

The finite strip method is presented for the analysis of steel deck bridges. Like the Pelikan-Esslinger design method for the steel deck bridges, steel deck is treated as an equivalent orthotropic plate. In the presented method, the deck is discretised by finite strips in the longitudinal direction and the effect of main girder or floor beam deflection can also be accounted for. In this method, the terms of harmonic series at elastically support such as transverse floor or diaphragm in steel deck become coupled. Solutions of this method are compared with other available analytical and numerical solution, and good agreement is observed.

Most of tall apartment buildings constructed in our county are wall-type R/C structures composed of hear walls and slabs. It is necessary to evaluate of hysteretic properties of shear walls in wall-type R/C structures which resist lateral loads as well as axial loads. In this study, first to evaluate the wall's hysteretic behavior nonlinear analyses with IDARC 4.0 are performed for eight specimens subjected to horizontal load reversals. As a result of nonlinear analyses of specimens we can obtain three parameters which determined the hysteretic parameters such as stiffness degrading, strength deterioration and inching behavior respectively. With this three parameters, strength and deformation capacity of 5, 10, 20-story shear wall of apartment building is estimated from the results of push-over analysis.

The basic systems of spatial structures such as shells, membrane, cable-nets and tensegrity structure have been developed to create the large spaces without column. These structures may have large freedom in scale and form, and especially tensegrity structures are received much attention from the view points of their light weight and aesthetics. But There re some difficulties concerning structural stability, surface formation and construction method. One of the way to solve these problems reasonably is a combination of tensile members and rigid members. A structural system based on this concept is referred to as the "HTS ( Hybrid Tension Structure )". This is a type of flexible structural system which is unstable initially, because the cable material has little initial rigidity. As cable - dome hybrid structures is a type of HTS, the initial stress for the self- equilibrated system having stable state have to be introduced. To determine initial stress having stable state, the shape finding analysis is required before the stress - deformation analysis. In this paper, the primary objective is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity for shape finding of cable-dome, and to propose the method to decide the initial stress by the shape analysis of cable-dome hybrid structure with the self-equilibrated state.

Genetic Algorithm(GA), which is based on the theory of natural evolution, has been evaluated highly for their robust performances. The optimization problems on truss structures under the prescribed displacement are solved by using GA. In this paper, the homologous deformation of structures was proposed as the prescribed displacement. The shape analysis of structures is a kind of inverse problems different from stress analysis, and the governing equation becomes nonlinear. In this regard, GA was used to solve the nonlinear equation. In this study, the shape analysis method in which not only the positions of the objective nodes but also the layout and sectional area of the member are encoded to strings in the GA as design parameters of the structures is proposed.

The three-dimensional nonlinear analysis on the partial tension experiment of Beam-Column connections in hybrid connections with RC columns and S beams is simulated. In this paper, mechanical characteristics between steel plates and concrete is investigated. Also the stress transfer mechanism prior to beam-column connection analysis was considered by using joint element.

Static load tests were performed to propose the appropriate strengthening method of R/C deep beam using Carbon Fiber Sheets and compared to those of nonlinear structural analysis. Fiber direction and anchorage method on the deep beam specimen were chosen as experimental variables, which lead to the following conclusions that initial shear cracks are independent of strengthening method and fiber directions perpendicular to the expected fracture mode, which was given by the nonlinear structural analysis, show better performance compared to those of horizontal and vertical fiber directions.

The objectives of this paper is to analyze the reinforced concrete structures by using fiber model. In this study, the fiber modeling techniques including modeling of support conditions are studied. In order to verify the modeling techniques, analysis results obtained for reinforced concrete cantilever beam and reinforced concrete T-girder bridge under cyclic loading are compared with experimental results from full scale test. From the comparison, it is shown that the modeling techniques in this study can be well applied to the nonlinear failure analysis of reinforced concrete structures with porper modifications.

The buckling of the perforated web of a simply supported Η-section beam subjected to uniformly distributed load is examined by means of the finite element method. With buckling analysis results, the effect of this hole on the load carrying capacity of the beam with dimensions L/h = 11 and 13 ( L = span length h = web depth) is investigated. The parameters whose variation have been considered are hole size and location. It can be generally concluded that the buckling of the perforated web of an H-section beam is not affected seriously by the location of the perforation.

The chloride attack of the top mat of reinforcing bars is a major cause of deterioration of comcrete deck of plate girder bridges. This is caused by a current design method which requires a top mat of reinforcing bars to resist a negative bending moment in bridge decks. In recently, empirical evidence has indicated that the top transverse reinforcing bars can patially or fully be eliminated without jeopardizing the structural integrity of a deck. So, one of the most efficient way to increase durability of concrete deck of bridges is the development of new design method that reduce or eliminate the top mat reinforcing bars, mad it is possible by the exact analysis that considering the negative bending moment reducing effect which introduced by relative deflection of plate girders. In this study, we develop the new bridge deck analysis method that considered the effect of relative girder deflection by applying the principles of slope deflection method of frames, and that is fine tuned with results of finite element analysis. This new approach evaluate a bending moment in a deck based on the effect of relative girder deflection as well as the magnitude of wheel loads, the girder spacing and stiffness, deck stiffness and the span length

In suspension bridges, the axial farces in the wires are transferred by side pressure on the semicircular face, and further from the strand shoe through rods to a base plate fixed to the massive concrete part of the anchor block. For prefabricated strands the most common way of anchoring is by socketing the ends of the strands. In this study, strand shoe and hanger socket are analyzed far various load conditions using Finite Element Method. The finite element models are built using MSC/PATRAN and analysis is carried out using MSC/NASTRAN. Results are again completely processed using MSC/PATRAN. From the results of the analysis, trends of deformation and stress distribution are reviewed and important factors to consider in the design of strand shoe and hanger socket are discussed.

An elasto-plastic stochastic finite element method is developed to evaluate the probability of failure of the underground structure. The Mohr-Coulomb failure criteria is adopted for yield condition. The material properties such as the elastic modulus and the cohesion are assumed to be statistically independent random variables which are modeled as spatial stochastic fields. The displacements around the excavated area and the probability of the failure are examined by varying the coefficient of variance for each variables. It is found that the developed procedure can provide the proper probabilistic information about the failure of the underground structure

The development of Reinforced Concrete member design modules is necessary for user to design structures easily. The purpose of this paper is to be available for a integrated system used structure design. This module is linked with central database for the benefit of minimizing time of design and user's efforts. In order to minimize memory space, all of data is stored in central database. Member design modules applied Object-Oriented concepts are possible to be reusible, flexible for member functions in classes. This modules can be operated both independent member design modules and a part of integrated system. Sooner or later, this modules will be related to member grouping modules by data.

The object of this study is shape finding and cutting pattern generation of membrane structures under the following assumptions : (1) material is linearly elastic (2) stress state is plane stress. Cable and membrane structures should introduce the nonlinear analysis considering geometric nonlinearity because these structures deform largely under the external loads. The analysis procedure is consisted of three steps considering geometric nonlinearity unlike any other structures. First step is the shape finding analysis to determine the initial equilibrium shape. Second step is the stress-deformation analysis to investigate the behaviors of structures under various external loads. Once a satisfactory shape has been found, a cutting pattern based on the shape finding analysis may be generated from the view point of construction. In this paper, (1) shape finding analysis formulation and an example, (2) cutting pattern determination procedure using weighted least-square minimization flattening method and some results are presented.

This paper discusses the development and use of an integrated system for the design of steel box girder bridges. The system includes pre/post processors designed particularly for the ease of use by adopting GUI(Graphical User Interface). They offer convenient facilities for the management of design data and thus enable the user to draw satisfactory structural designs. In particular, ease of redesign iterations makes better structures possible in this system

An entity-based integrated design model can be used to organize and represent information and activities involved in design. The model involves a number of product and process entities. Product entities describe design information, and process entities describe design activities. The relationships among entities Includes organizational, interaction, and sequence relationships. The paper focuses interaction relationships among design information. The interaction relationships can be represented as constraints. Types of constraints includes demand constraints, dependency constraints, and interaction constraints. The paper describes dependency and Interaction constraints. The concepts of representing and processing dependency and interaction constraints in an entity-based integrated design model are presented.

Since most engineering problems have had open-ended and ill-defined characteristics, design process is in advance attended with determination of alternatives based on realistic constraints after definition of appropriate problem. And it is completed with selection of best alternative through their comparison and investigation, and with performance of selected-alternative's detail design. As the process of structural design compared with that of general design, this paper presents a paradigm which can generate structural design alternatives, select optimum structure among them and simultaneously set its optimum design variables in reference of several objective as a result in more extended design region. For this purpose, specialized genetic algorithms which can handle design alternatives and multicriteria problems is used.

To design a space frame structure by the conventional method is not easy in practical sense since it is generally a three-dimensional complicated form, and stability and nonlinear problems are not easily checked in the design process. This paper describes two modules, the Model Generator which is based on PATRAN user interface that enables users to generate a complicated finite element model; the Optimum Design Module which analyzes output results of analysis program, and designs members of a space frame. The Model Generator is based on PCL while C++ language is used in the Optimum Design Module. Structural analysis is performed by using ABAQUS. All of these modules constitute Space Frame Integrated Design System. The Core of the system is PATRAN database, in which the Model Generator creates information of a finite element model. Then, PATRAN creates input files needed for the analysis program from the information of the finite element model in the database, and in turn, imports output results of analysis program to the database. Finally, the Optimum Design Module processes member grouping of a space frame based on the output results, and performs optimal member selection of a space frame. This process is repeated until the desired optimum structural members are obtained.

Although artificial neural network based on backpropagation algorithm is an excellent system simulator, it has still unsolved problems of its structure-decision and learning method. That is, we cannot find a general approach to decide the structure of the neural network and cannot train it satisfactorily because of the local optimum point which it frequently falls into. In addition, although there are many successful applications using backpropagation learning algorithm, there are few efforts to improve the learning algorithm itself. In this study, we suggest a general way to construct the hidden layer of the neural network using binary genetic algorithm and also propose the various learning methods by which the global minimum value of the teaming error can be obtained. A XOR problem and line heating problems are investigated as examples.

Port structures are one of the important infrastructure of the nation. To ensure safety and extend lifetime of the existing port structures, it is necessary to develop proper maintenance program. In this study, port inspection manual for pier type structure are developed. The flow of inspection program is designed and defect type for each component of wharf is classified. Also systematic method of rating and evaluation is developed together with conceptual design of port maintenance data base system.

Optimum design of mooring dolphin is numerically investigated. Design optimization problem of mooring dolphin is first formulated. Geometry and cross sections of piles are used as design variables. Design objective is the total weight of steel piles of mooring dolphin and the constraints of stress, penetration depth, lower and upper bounds on design variables are imposed. Based on the design variable linking and fixing, several class of design variations are sought. For the numerical optimization, both PLBA( Pshenichny-Lim-Belegundu-Arora) program and DNCONF subroutine code in IMSL library are used. For a dolphin with 20 steel piles, vertical and inclined, optimum designs for different cases are successfully obtained, which can be applied for the mooring of a large floating structure.

Recently, the importance of multi-objective optimization techniques and stochastic search methods is increasing. The stochastic search methods have the concepts of the survival of the fittest and natural selection such as genetic algorithms(GA), simulated annealing(SA) and evolution strategies (ES). As many accidents of oil tankers cause marine pollution, oil tankers of double hull or mid deck structure are being built to minimize the marine pollution. For the improvement of oil tanker design technique, an efficient optimization technique is proposed in this study. Multi-objective optimization problem of weight and cost of double hull and mid deck tanker is formulated. Discrete design variables are used considering real manufacturing, and the concept of relative production cost is also introduced. The ES method is used as an optimization technique, and the ES algorithm was developed to generate a more efficient Pareto optimal set.

This study presents a discrete optimization of tall steel buildings under multiple drift constraints using a dual method. Dual method can replace the primary optimization problem with a sequence of approximate explicit subproblems. Since each subproblem is convex and separable, it can be efficiently solved by using a dual formulation. Specifically, this study considers the discrete-optimization problem due to the commercial standard steel sections to select member sizes. The results by the proposed method will be compared with those of the conventional optimality criteria method

Recent, more and more steel deck bridges are adopted for the design of long span bridges and the upgrading of existing concrete deck bridges, mainly because of reduced self weight, higher stiffness and efficient erection compared to concrete decks. The main objective of this study is to propose on formulation of the design optimizations to develop an optimal desist program required for optimum desist for orthotropic steel-deck bridges. The objective function of the optimization is formulated as a minimum initial cost design problem. The behavior and design constraints are formulated based on the ASD and LRFD criteria of the Korean Bridge Design Code(1996). The optimum design program developed in this study consists of two steps. In the first step the system optimization of the steel box girder bridges is carried out. And in the second step the program provided the optimum design of the orthotropic steel-deck with close ribs. In the optimal design program the analysis module for the deck optimization is based on the Pelican Esslinger method. The optimizer module of the program utilizes the ADS(Automated Desist Synthesis) routines using the optimization techniques fuor constrained optimization. From the results of real application examples, The cost effectiveness of optimum orthotropic steel-deck bridges designs based on both ASD and LRFD methods is investigated by comparing the results with those of conventional designs, and it may be concluded that the design developed in this study seems efficient and robust for the optimization of orthotropic steel-deck bridges

The purpose of this study is to show how to gain the morphology of the Hybrid Spatial Structures and to get the geometrical data such as node coordinates, member relationships and graphic images. To form spatial structures, we have developed morphological aspects of general spatial structures, programming process and techniques. Structural design has many processes. Especially, it is very important to consider the determination of structural configuration. Regular Hybrid Spatial Structures have complex configuration, so we need to make use of automated computer process to determine structural shape in Hybrid Spatial Structures. We have applied morphological aspects to double layer plate, single layer dome, double layer dome and tensegrity structure.

A solution method is presented to solve the eigenproblem arising in tile dynamic analysis of non-proportional damping systems with symmetric matrices. The method is based on tile use of Lanczos method to generate a Krylov subspace of trial vectors, witch is then used to reduce a large eigenvalue problem to a much smaller one. The method retains the η order quadratic eigenproblem, without the need to the method of matrix augmentation traditionally used to cast the problem as a linear eigenproblem of order 2n. In the process, the method preserves tile sparseness and symmetry of the system matrices and does not invoke complex arithmetics, therefore, making it very economical for use in solving large problems. Numerical results are presented to demonstrate the efficiency and accuracy of the method.

This paper demonstrates how ambient vibration measurements at a limited number of locations can be effectively utilized to estimate parameters of a finite element model of a large-scale structural system involving a large number of elements. System identification using ambient vibration measurements presents a challenge requiring the use of special identification techniques, which ran deal with very small magnitudes of ambient vibration contaminated by noise without the knowledge of input farces. In the present study, the modal parameters such as natural frequencies, damping ratios, and mode shapes of the structural system were estimated by means of appropriate system identification techniques including the random decrement method. Moreover, estimation of parameters such as the stiffness matrix of the finite element model from the system response measured by a limited number of sensors is another challenge. In this study, the system stiffness matrix was estimated by using the quadratic optimization involving the computed and measured modal strain energy of the system, with the aid of a sensitivity relationship between each element stiffness and the modal parameters established by the second order inverse modal perturbation theory. The finite element models thus identified represent the actual structural system very well, as their calculated dynamic characteristics satisfactorily matched the observed ones from the ambient vibration test performed on a large-scale structural system subjected primarily to ambient wind excitations. The dynamic models identified by this study will be used for design of an active mass damper system to be installed on this structure fer suppressing its wind vibration.

This paper deals with the influence of elastic foundations on natural frequencies of curved beams. Taking into account the effects of rotatoy inertia and shear deformation, the differential equations governing free, out-of-plane vibrations of circular curved beams resting on Winkler-type foundations are derived and solved numerically. Hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered in numerical examples. The lowest three natural frequencies are claculated over a range of non-dimensional system parameters: the horizontal rise to span length ratio, the slenderness ratio, the foundation parameter, and the width ratio of contact area between the beam and foundation. The effects of rotatory inertia and shear deformation are also analyzed.

In this paper, a newly derived formulation of a crack detection model is presented and its feasibility to detect cracks in structures is verified experimentally. To meet this objective, the followig approach is utilized. Firstly, the crack detection scheme which consists of the damage localization model and the crack detection model is formulated. Secondly, the feasibility and practicality of the complete procedure of the crack detection model is evaluated by locating and sizing cracks in clamped-clamped beams for which a f3w modal parameters were measured for sixteen uncracked and cracked states. Major results observed from the crack detection exercises include that far most damage cases, the predicted crack locations falls within very close to the inflicted locations of cracks in the test beam and the size of crack values estimated at the predicted locations are very close to the inflicted magnitudes.

A nonlinear anile element formulation of flat shell elements with drilling d.o.f, is presented for the geometrical nonlinear analysis of thin-walled structures. The shell element to be applied in finite element analysis was developed by combining a membrane element named as CLM with drilling rotation d.o.f, and plate bending element. The combined shell element possesses six degrees of freedom per node. The element showed the excellent performance in the linear analysis of the folded plate structures, in which the normal rotational rigidity of folded plates is considered, therefore, using this element geometrical nonlinear analysis of those structures is fulfilled in this study. An incremental total Larangian approach is adopted through out in which displacements are referred to the original configuration. Comparing the results with those of other researches shows the performance of this element and a folded plate structure is analyzed as an example.

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and toll.or structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates with free edges supported on elastic foundation and with a pair of opposite edges under axial forces is presented. Such plates represent the concrete highway slab and hybrid composite pavement of bridges. The reinforced concrete slab can be assumed as a special orthotropic plate, as a close approximation. The highway slab is supported on elastic foundation, with free boundaries. Sometimes, the pair of edges perpendicular to the traffic direction may be subject to the axial forces. The plate is subject to the concentrated load/loads, in the form of traffic loads, or the test equipments. Any method nay be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation, the aspect ratio of the plate, and the magnitudes of the axial forces and the concentrated attached mass on the plate, on the natural frequency is thoroughly studied.

The apparently different physical problems of lateral vibration and elastic stability of a linear member are limiting cases of a single phenomenon, the more general expression being the mode of vibration with end thrust. For a single-span beam-column, it is generally known that the square of the frequency of lateral vibration is approximately linearly related to compressive axial force. In this paper the relationship between the frequency and axial force of multi-span compression members is investigated by means of the finite element method.

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the subject problem is presented. The structure considered for this report is two span continuous special orthotropic plates with elastic intermediate support. The use of elastic support as one of the passive control means is common. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purposa in this paper. The influence of the modulus of the foundation, and $D_{ij}$ stiffnesses on the natural frequency is thoroughly studied.

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the three span continuous reinforced concrete bridge with elastic intermediate supports in presented. Such bridge represents either concrete or sandwich type three span bridge on polymeric supports for passive control or on actuators for active control. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, In this paper. The influence of the modulus of the foundation and $D_{22}$, $D_{l2}$, $D_{66}$ stiffnesses on the natural frequency is thoroughly studied.d.

In this paper, ground vibration analysis methods for train transit on bridges are studied. Train loads acting on the piers are evaluated considering the interactions between the trains and the bridge. The 2D in-plane wave propagation method and the axisymmetric wave propagation method are used in the ground vibration analysis, and then the results of the ground vibration are compared. A modified axisymmetric method is presented, which can consider the effect of the train loadings on a series of piers as the train moves.

Recently, constructions of large and slender structures have been increased owing to the advancement of the structural technologies and that of the new light-weight and high-strength construction materials. Consequently, vibration problems of those slender structures have become a new issue in the area of structural engineering. Active control for those structures is the method that keeps the structures safe from the external loads, especially dynamic loads, by enforcing active forces derived from control devices. In this paper, a procedure for the instantaneous optimal control for structural vibration is presented. Numerical method and experiment are performed for evaluating the effectiveness of active control for reducing vibration of structures.

Generally the excessive caused by isolated sources in localized to members closely located to the vibration sources. In this case it may not be economical to model the whole structure to obtain the responses of a specific member. In this study, a substructuring technique has been used for local vibration of a framed structure. The boundary conditions of members selected are determined by condensing the degrees of freedom of the remaining members. Fixed and hinged boundary condition are also assumed for comparison. According to the results, the substructuring technique is quite efficient in predicting the responses of a structure on which the vibration source in located, but is not very reliable for the members located for away from the source.

A numerical study is conducted to examine the wave scattering at infilled trenches which may be constructed to reduce the ground-transmitted vibration. The finite element method is used for the simulation of the wave propagation in the semi-infinite region. In order to keep the computational burden manageable, the absorbing boundaries are employed. The numerical technique is validated by modeling a published problem. The results are shown to be in good agreement with the published data. The screening effectiveness of the infilled trenches is then studied for different trench dimensions and material properties.

An approach to identifying input forces is proposed using measured structural dynamic responses and its analytical model. The identification of input forces is a reverse process and ill-conditioned problem. Its solution is unstable and generally case dependent. In this paper, the ill-condition is described considering characteristic matrix which is defined by reduced dynamic stiffness matrix. Special attention is focused on the condition number of a characteristic matrix used in the solution algorithm of this reverse process. Simple example is presented in support of the ill-condition of a reverse process.

This study investigated to the stability of open car parks below $600^{\circ}C$, as to predict behavior of bare FR steel structure noosed to fire. Especially, This study evaluated deformation of steel structure members of open car parks, considering change of material property by temperature. From the numerical analysis, we know the fact that the deformations comparing of standard values are stable to use the FR steel below 600 $^{\circ}C$ in open car parks plan

The distinct element method is improved to consider the charateristics of stress wave propagation in media involving the discontinuous faces. The distinct element method has many advantages to analyse the characteristics of the reflection, refraction and deflection of the waves in nonhomogeneous media. The double-suing connection system is adopted instead of the single-spring connection system because the distinct element cannot be used for analysing the contact behavior between the different materials by only one contact spring. For the verification of the improved code, the results of the numerical analysis are compared with that of the photoelastic experiments which are one or two dimensional wave propagation problem of the nonhomogeneous media including the different accoustic impendence material or voids. It is shown that the characteristics of the stress wave propagation in nonhomogeneous media can be simulated appropriately using the improved distinct element method.

The content of this paper consists of two related subjects. One is the assessment of damages in the existing structure and the other is the evaluation of seismic capacity of the structure with damage. A method is presented for damage assessment of existing structures using the modal data measured at limited points by the inverse medal perturbation technique. For efficient damage assessment, the number of the unknown probable damaged members is reduced for each damage identification by grouping the members in the large structure. The aseismic capacity is evaluated for the structure using the results of damage assessment. An example analysis is carried out for a building structure subjected to different earthquake excitations.

This paper presents the results of a major parametric study on the collapse cause of the Sungsoo Grand Bridge, a Gerber-type continuous truss bridge, which had collapsed just at the 15th year since opening to traffic. Among the various collapse causes such as poor design, poor welding, poor maintenance, and heavy traffic loads, this study focuses on the collapse cause assessment incorporating the effects of braket and H-beam members right below the expansion joint of the suspended truss. A local FEM analysis using fine shell elements is carrided out for the more precise estimation of stress range of the vertical pin-connected hanger whose fatigue fracture triggered the collapse of the bridge. Both the conventional S-N approach and the Ang-Munse's fatigue reliability method are used for the evaluation of the fatigue life and fatigue failure probability for the assessment based on all the available results of various field and labolatory tests. From these observations, It may be affirmatively stated that the effects of bracket and H-beam members accelerated the fatigue failure, and thus should be regarded as one of major causes that triggered the bridge collapse

For many decades, railroad technology was used to set up tracks with jointed rails and lengths in accordance with rolling and handling technology. The joints lead to drawbacks in the track and in controlling rising maintenance costs. So, railroad engineers became interested in eliminating joints to increase loads, speeds and improvements in rolling, welding, and fastening technology. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. In the case of the elimination of rail joints, it may cause the track to be suddenly and laterally buckled by thermal forces and vehicle load. Thermal forces are caused by an increase in the temperature of railway track. For many years, many analytical and experimental investigations have been conducted to improve the safety of CWR track by various research center in many country. In this paper, CWR track model and CWRB program is developed for buckling analysis using finite element method(FEM). The finite element discretization is used for a rail element with a total of 14 degrees of freedom. The stiffness of the fasteners, tie, and ballast bed is included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented in this paper

In this study, an explicit transient analysis program considering material and geometric nolinearities has been developed and used to analyze the dynamic behaviors of circular, parabolic, sinusoidal and catenary arches according to the change of shapes and boundary conditions. To understand dynamic behaviors of arches, first of all, the results of free vibration analysis for four kinds of arches are discussed. The results of transient analysis under impact loads we discussed in respect of boundary condition, change of height, and arch-shape. The dynamic behaviors of arches by nonlinear transient analysis considering both material and geometric nolinearities are also discussed.

A consistent finite element formation and analytic solutions are presented for spatial stability of thin-walled circular arch. The total potential energy is derived by applying the principle of linearized virtual work and including second order terms of finite semitangential rotations. As a result the energy functional corresponding to the semitangential rotation is obtained, in which the elastic strain energy terms are considered restrained warping effects. We have obtained analytic solution for the lateral buckling of monosymmetric thin-walled curved beam subjected to pure bending or uniform compression and it's boundary conditions are simply supported. For finite element analysis, the two node cubic Hermitian polynomials are utilized as shape Auctions. In order to illustrate the accuracy of this study, parameter studies for lateral buckling problems of circular arch are presented and compared with available solutions and numerical results analyzed by the FEM using straight beam element.

The equilibrium path of shallow sinusoidal arches supported by hinges at both ends is investigated. The displacement increment method is used to get the solution of the nonlinear differential equations for these structures and to plot the equilibrium paths by the results. Using the equilibrium paths, the relations between the position of buckling point and buckling type for the case of sinusoidal distributed loads are inferred. From the result that the buckling type changes according to the normalized rise of arch, it is also shown that the arch rise is the governing factor to stability regions

In this study, analytic solution and finite element formulation for the free vibration analysis of thin-walled circular arch, based on linearized virtual work and Vlasov's assumption, including restrained warping effect and second order terms of finite semitangential rotations, is presented. The total potential energy is derived by applying the Hellinger-Reissner principle. In this formulation, all displacement parameters of deformation are defined at the centroid axis. For the finite element formulation, the two node cubic Hermitian polynomials are utilized as shape functions. In special case, potential energy functional of thin-walled curved beam with monosymmetric cross section is derived. From this methodology, analytic solution for the free vibration of monosymmetric circular arch with simply supported is derived. In order to illustrate the accuracy of this study, various parameter studies for free vibration of circular arches are presented and compared with numerical solution analyzed by the FEM using straight beam element.