In finite element analysis, a kind of instability, which is called the hourglass mode, arises when one-point quadrature integration rule is used to calculate the stiffness matrix for the 2-D quadrilateral element. To control the instability, various kinds of methods have been proposed, among them, the one proposed by Kosloff and Frazier is thought to be the most effective and simple one, but in their paper, they confined the hourglass control method within the elastic problems. In this paper, the details of how to apply the hourglass control method in nonlinear analysis is presented, and a modified scheme is proposed to obtain the accurate nonlinear element response.

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The purpose of this paper is to develop a systematic method of time-domain nonlinear system identification using NARMA model. In the beginning the Hilbert transform test was used for nonlinearity, then an orthogonal parameter estimation algorithm is applied to a NARMA model which represents the nonlinear system model. Finally the nonlinear frequency response functions were computed. Application of the methodology to a combined Duffing and Van Der Pol nonlinear system and the seismic response data of Van Nuys building to Whittier and Northridge earthquakes are studied.

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Propagation of gravity perturbated waves in a deep oceanic structure was investigated to examine the effects of compressibility of the ocean as well as solid-fluid interaction on the gravity perturbated waves. Gravity perturbated waves were calculated from Green's function represented by the thin layered element and discrete wavenumber method. It was found from the numerical calculations that the compressibility of the ocean affected the amplitude of the gtravity perturbated waves.

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Tests of stiffened steel plates subjected to biaxial compressive forces have been performed to obtain the ultimate strength of the plates. A plate test rig has been modified to apply compressive forces to rectangular stiffened plates. A new approach is presented for predicting the ultimate strength of plates under biaxial loadings. The experimental results are used to show the validity of the new approach. The existing numerical and experimental results are also used to examine the applicability of the present approach to the plates under biaxially applied in-plane compressive and tensile forces. Although the present approach is easier to apply than other available approaches, it provides consistently good predictions.

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Layered solid-fluid media in a gravity field were analyzed by a thin-layered element and discrete wave number method. The gravity effects were incorporated to the governing equation for fluid and solid-fluid interaction equations. Green's function for layered solid-fluid media in a gravity field was represented in terms of the normal modes, which were obtained from the thin-layered element matrices. Several investigations were applied to the differences between the Rayleigh wave mode and the gravity wave mode. Numerical calculations showed that the gravity waves, in which the phase velocity and frequency is very low, were caused as a reult of the propagtion of the body waves and the Rayleigh wave.

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The vibration, buckling and dynamic stability of anti-symmetric angle-ply laminated rectangular plate is studied. The effect of shear deformation is considered. This problem is studied by using Rayleigh-Ritz method and Hamilton principle. The dynamic stability is solved by the harmonic balance method.
Natural frequencies and buckling properties are shown at first for various parameters of the anti-symmetric laminated rectangular plate. The regions of instability which contain simple parametric resonances and combination resonances are discussed.

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The purpose of this study is to develop a nonlinear finite element method to simulate the results from experiments on stick-slip shear failure of rock masses. First, we introduced the constitutive relations obtained from the experiments into joint elements which we employed to model the fault of rock masses. Then we performed parametric study to investigate the effect of parameters which control the constitutive relations on the rupture propagation. Finally, we compared the results obtained from the proposed method and those obtained from the experiments and discussed the validity of the method to simulate the rupture mechanism of faults.

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Pseudo-dynamic tests have been performed with five concrete-filled steel columns and one steel box column in order to investigate the seismic behavior of slender bridge piers. The test results show that concrete-filled steel slender bridge piers do not always cause large residual displacements, but cause large maximum response displacements.

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The objective of this paper is to propose a simplified procedure of estimating a degree of imperfection for a composite girder with partial interaction, paying attention to a longitudinal force and a horizontal shearing force obtained by solving a differential equation of the girder. A relation between rigidity of shear connectors and a parameter composed of the sectional properties and the girder span are used, in estimating a degree of imperfection of a longitudinal force, a horizontal shearing force and a deflection for the composite girder having a uniform and a stepped cross section. It is also clear that the fiber stresses of the composite girder with partial interaction can be predicted by employing the estimated degree of imperfection. Finally, main findings are summarized and an efficiency of this method is confirmed.

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In order to analyze an elasto-plastic behavior of composite structures, it is required to take into account a non-linear shearing force-slip relation of a shear connector as well as non-linear stress-strain relation of concrete and steel materials.
In this paper, the elasto-plastic behavior of the composite girder with incomplete interaction was analyzed by the rigid-body-spring model taking into account the non-linear shearing force-slip relation obtained from the corresponding push-out test.
The analytical results were compared with the experimental one and the efficiency of this analytical method was comfirmed.

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Fatigue crack propagation analyses for typical steel structural details are performed under various types of variable amplitude stresses which may approximately express the stress spectrum in various steel structures. On the basis of the analytical results, the relationship between threshold stress range to give the fatigue damage and the degree of fatigue damage is verified. By combining the relationship with the linear cumulative damage conception, a new procedure is proposed to predict the fatigue life under variable-amplitude stresses. Fatigue life estimated by the proposed procedure is compared with that predicted by previous procedures such as Miner's law, modified Miner's law, Haibach's procedure and so on, and with experimental results by Melhem et al.

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At a pin connection detail of suspender ropes to chord member of stiffening truss for a suspension bridge, all loads are transmitted by bearing of pin and pin plate. Further at a wind condition, out-of-plane force acts repetitively at the connection due to the horizontal component of suspender rope tension caused by the relative movement between stiffening truss and main cables. This creates nonuniform bearing stress condition or pin connection. This report presents the results of static loading test and fatigue test on a full-scale specimen with two proposed pin connection detail a truss-stiffened long-span suspention bridge in order to verify the weak point and the fatigue strength.

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Although high strength bolted tensile joints could have much advantage over the originated bolted connections from the view point of its mechanical behavior, structural simplicity and easiness of erection, tensile joints have not been commonly used for primary members of bridge structures because of the lack of rational design procedure for such joints. In order to apply tensile joints for bridge structures, it is necessary to establish the rational design procedure based on the strength not only under static loading but also under cyclic loading. In this study, split tee flange joint which is a typical high strength bolted tensile joint, cyclic loading test is carried out varying the thickness of the flange plate. Based on experimental results, the mechanical behavior under cyclic loading and the fatigue strength of tensile joints are assessed. As a result, it is confirmed that split tee flange joints are rationally designed considering static and cyclic loading.

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An efficient knowledge acquisition support method is necessary for improvement and maintenance of knowledge base in durability evaluation of RC bridge deck. In this paper, a method is proposed to automatically acquire fuzzy production rules using genetic algorithms with neural network. Evaluation functions of genetic algorithms can be obtained by using weights of the neural network. Introducing a neural network into genetic algorithms, it is possible to acquire new knowledge so that the method is useful when it is difficult to acquire knowledge in the field.

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RC deck slabs were cut out from highway bridges as the specimens, and various investigations and tests were conducted to clarify the conditions of construction, actual state of damages and remaining fatigue life of those slabs. The following results were obtained. (1) The state of damages can be rated by parameters such as crack density, deflection and static loading capacity of the slab. (2) The actual bridge deck slabs have 20 to 30 percent less static loading capacity compared to newly constructed slab specimens. (3) Remaining fatigue life of the actual bridge deck slabs is shorter than the estimated life from the existing S-N curves. Finally, correction of the S-N curve for the actual slab was proposed considering equivalent repeated numbers, the effect of drying shrinkage and the effect of water. (4) The present rating criteria for damaged RC slabs by JH was proved to be reasonable through those experiments.

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As a method to determine the time to re-painting of steel bridges, the relation between the ratio of deterioration area observed on a paint film surface and the corrosion degree (corrosion density) of the steel occurred under its paint film was measured by using the image processing for 6 bridges with the different natural environments.
As a consequence of analyzing these data through a statistical technique, it was found that there was a significant correlationship between a ratio of deteriorated area of paint film surface and a deterioration degree under its paint film.
In addition, the corrosion degree under paint film would be presumed from the deterioration degree on the surface of the paint film by the regression fomula of our research.

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As far as the aerodynamic behavior of recent super long span bridge concerns, three dimensional motions, including the lateral motion of the deck, are very important to describe the flutter occurrence. To make detailed discussion on it, 3 dimensional precise aerodynamic farce information is also very important. In the measurement of unsteady aerodynamic farce there have been applied the free vibration method and the forced vibration method. However they can be hardly extended to the measurement of more complex motion. In this paper newly developed flexible method in extension to multiple dimensional measurement was introduced and its effectiveness was examined by a wind tunnel test.

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Because of increase of span length of suspension bridges, it has become more important to evaluate the stability of flutter phenomena. This study aims to clear the mechanism of coupled flutter. In order to clear it, wind tunnel test is carried out on fundamental bluff bodies to calculate aerodynamic derivatives of them, and roles of aerodynamic derivatives on flutter is investigated by using step-by-step analysis in place of conventional complex eigen value analysis.

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In this paper, the geometrical nonlinear analysis of three-dimensional, long-span cable-stayed bridges is formulated to investigate their static behaviors.
A cable-stayed bridge with 1500m center span is analysed as an example. The static nonlinear behaviors of the bridge under the in-plane live loads as well as those under the displacement-dependent, out-of-plane wind loads are discussed in detail. The analytical results show that the effect of geometrical nonlinearity in the in-plane loading is not remarkable but that the nonlinearity under the wind loading due to the wind-induced deformation of the bridge can be very significant.

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The purposes of this study are to investigate the human vibration sensibilities at the using of pedestrian bridges and to discuss serviceability limit states. Traditional ways of the relationship between the human vibration sensibilities and serviceability limit states are ambiguous. This relationship is presented in remarkably simple and the human vibration sensibilities obtained in this study can be applied easy to design pedestrian bridges.
The dynamic response characteristics of pedestrian bridges are investigated, and the range of the frequencies of pedestrian bridges that need the serviceability checking are considered in detail. And, the rational procedure to judge vibration serviceability on pedestrian bridges is proposed and the applicability is shown.

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Human behaviour in a closed space such as an under ground structure during disaster is simulated by using distinct element method (DEM). DEM is the numerical analysis method in which the positions of the elements are calculated by solving the equations of motions step by step. Not only the individual but also the group behaviour can be obtained by using this method.
In this paper, we considered the DEM elements as humen beings and investigated the behaviour of the crowd flow that evacuates from the closed space to the outside through the passage or the steps. The trace of evacuating people and time history of the force that acts on the people can be easily calculated. The theoretical equations of input and output flow at the exit of the room are proposed according to the regression analysis based on the results of the DEM simulations. The present method enable us to simulate the evacuation during disaster.

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This study is concerned with methods for optimizing restoration process of damaged lifelines by earthquakes. We developed algorithms by using Simple Genetic Algorithms (Simple GA) and Hybrid Genetic Algorithms (Hybrid GA) for deciding the priority of component to restore. Simulation results show that Hybrid Genetic Algorithms is useful tool.
We also apply Single Populated Genetic Algorithms (SPGA) to distribute restoration teams at damaged sites for optimizing the restoration process of lifeline networks.

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Complex spaces such as underground shopping centers or department stores where many people gather could be dangerous places if a fire breaks out. It is very important that owners or salesclerks who are responsible for fire control in such places know how to lead quickly and safely people to the exits in an emergency. To simulate the behavior of evacuees and guides in a fire, we developed a computational model using genetic codes that are used in genetic algorithm. This model simulates not only the behavior of guides and evacuees but also the interaction between evacuees' behavior and guide's instructions.

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This paper deals with the effect of known parameter errors on structural identification problems by using the estimation formula of confidence region. Numerical experimentation is conducted to examine the validity of the proposed method by mean of the sensitivity analysis of identified parameters with respect to model parameter errors and the propagation low of errors. In this paper, a method, which estimates the confidence region of identified parameters based on the concept of prior information about unknown model parameters, is proposed. The investigation of proposed method is performed by numerical simulation. The validity of the proposed method is verified with the numerical results.

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In this paper, the effectiveness of neural networks applied to optimization is presented. By the example of structural optimization, it is shown that the method based on the neural networks can be used as a substitute of the conventional mathematical optimization method. By the example of mix proportion design of concrete, it is shown that the proposed method is applicable to the problem in which the conventional mathematical optimization method is difficult to apply.

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To construct the main tower foundation of suspension bridge (the Hakucho Ohashi), an artificial island and a continuous underground deep wall methods were applied. In this paper, the mechanical behavior of the continuous underground deep wall under excavating inside of the wall and constructing the foundation were numerically analyzed. Here, by means of the finite prism method with axial, symmetric, isoparametric and quadratic ring element, three-dimensional elastic analysis considering the interaction between the structure and soil was executed in each construction stage. Comparing the numerical results with the measured ones at the real construction, it was made clear that this kind of structures can be rationally analyzed by means of the present analytical method.

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The Daikai subway station of Kobe Rapid Transit System was seriously damaged during the 1995 Hyogokennanbu earthquake. The upper floor was collapsed and the route 28 above the floor was settled. These were caused by failure of the reinforced concrete columns. The test hammer test and the laboratory soil test were carried out to obtain the actual concrete strength and dynamic deformation characteristics of filled soil material. Furthermore, in order to make clear the reason why the structure was damaged, 2 kinds of analysis were conducted. First, dynamic response analysis was carried out. Static analysis considering non linear relationship between the moment and rotational angle at the end of the elements of the structure was carried out in which applied load derived from such sectioanl force as axial and shear force obtained at nodal point. Cracks at the end wall and failure of the columns indicate that severe lateral seismic force applied to the trnsverse section of structure. It is concluded that center columns failed due to bending and shear failure mechanism based on the analysis.

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This paper reports and discusses the statical loading test over longitudinal ribs in the orthotropic steel deck, forcusing on the strength of high strength bolted joints in a specimen with dimensions almost equal to the full size. Hand holes are required in the joints which causes the loss of a section. To compansate it, the base metal are incresed in thickness. Regarding the process, the fatigue strength in the butt weldings are low that can be a structual defect. Comparisons are made between the base metal increased in thickness joints and unchanged thickness joints at the longitudinal ribs, the consequences of the tests were almost the same.

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Fatigue tests of stripped plates with a circular hole are carried out under tension and bending. The condition of the prevention of the cracking at circular holes subjected to combined membrane and plate-bending stresses is investigated. An equation for estimation of the maximum stress at the edge of drilled holes is established. This equation contains the membrane and plate-bending stresses which are calculated by the finite element analysis with plate elements. An application of the drilled holes is shown for the fatigue cracks propagating in the girder webs where cross beams are connected.

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