It is quite complicated for the linear differential equation of beam deflection to be expanded as to varying cross section. But, once a tapered beam element is solved, its nodal stiffness relations can be adopted into a general discrete analysis of framed structures. In this paper, the method of separation into rigid displacement and deformation, which has been developed in the geometrically nonlinear analysis, is found to have a fitness for dealing with the varying beam elements; and typical two types of tapered 2-D beams are discretized from their linear solutions into the geometric and second-order stiffness relations.

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In most more economically developed countries an ever growing percentage of existing structures is threatened by obsolescence in the short- to medium-term−either because of structural deficits due to deterioration, or due to functional aging. To ensure sustained serviceability and safety of these structures, maintenance interventions are utilized, which allow partial or complete structural rehabilitation. However, such maintenance interventions have to be economically reasonable, that is, maintenance expenditures spent have to be outweighed by expected future benefits. For this purpose, we propose herein a novel optimization formulation for maintenance planning based on cost-benefit criteria. The usefulness of the proposed approach lies in the fact, that it not only allows to determine optimal sequences of maintenance times, rehabilitation levels and inspection qualities, but also allows to specify economically optimal lifetimes and acceptable failure rates of structures. The modeling of structural deterioration and maintenance, as well as the setting of all relevant cost factors is discussed in detail. Numerical examples investigate the effect of imperfect execution of maintenance actions and functional aging.

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The objective of this paper is to develop a vibration measurement system using three laser Doppler vibrometers. This makes possible to measure three-dimensional behavior of an object spatial densely as well as high accurately. Measurement principle of three-dimensional vibration using LDVs is based on the geometrical transformation of coordinates. At first, to validate the principle, fundamental system was developed. Then, the system was applied to measurement of train-induced vibration at a steel box girder bridge. Since local three-dimensional vibration was captured, its applicability was confirmed. Finally, three-dimensional vibration measurement system allowing a scan and an arbitrary setting for more suitable for on-site measurement was developed. In the system, measurement procedure was formulated in order to identify configurations of each LDV. Laboratory experiment showed the validity.

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Japanese design code for highway bridges has adopted the allowable stress design concept which requires the structures to have elastic behavior under the given design conditions. On the other hand some design codes in foreign countries include the plastic design concept, which can contribute to the cost reduction of steel bridges. In this study, considering strength and some other parameters in stress-strain relation of materials as random variables, Monte Carlo simulation is carried out in order to examine their influence on the probability distribution of positive flexural strength of composite compact sections, and the design formulae of positive flexural strength considering variation of material strength are proposed.

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This paper presents a new image processing for stably detecting cracks from various surface-images of concrete structures and identifying width and direction of them. The process for detection consists of two steps. The first step is to build a robust image-filter for detecting major cracks with the aid of genetic programming. The second step is to remove noises and to trace obscure cracks by iterative applications of the image-filter in local regions. The proposed method was found to stably detect cracks from photos taken under the various conditions. Then, widths and directions of the detected cracks are identified on the basis of the spatial derivatives of brightness patterns, and it is found that the identified values show good agreements with those by visual inspection

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In the 1995 kobe Earthquake, over 100 thousand houses were collapsed, 6,433 people died and 43,782 people were injured. Most of the casualties were crushed or suffocated to death under collapsed houses. In order to reduce human casualties caused by an earthquake, it is very important to know the process of structure collapse. In this study, the three dimentional behaviors of the collapse of timber house under seismic motion was analyzed using the distinct element method (DEM). To validate the simulation technique, two experiments were carried out. In a static experiment, timber joint parameters were determined. Secondally, a dynamic experiment was performed on a simplified structural model in order to verify the results of the DEM analysis. Finally, the numerical simulation technique was applied to a real structural model including the effect of building furniture contents.

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Double bevel T-joint is one of the most fundamental joints of steel bridges. Double bevel T-joint can be seen at beam-column connection of bridge piers. In the Japanese specifications, the welding should be full penetration. Fatigue cracks can be propagated from the weld defects such as incomplete penetration. Incomplete penetration should be avoided. The authors have developed a tandem array transducer. Specimens of double bevel T-joint were made. Ultrasonic test was conducted for those specimens. Detectability of incomplete penetration was investigated. Image reconstruction of incomplete penetration by synthetic aperture focusing technique was carried out. Height of incomplete of penetration could be estimated accurately. When a fatigue crack exists in a welded joint, crack tip opening occurs. Crack tip opening can be observed by echo height from the crack tip. Fatigue crack could be detected by comparing echo height between when load was applied and no load was applied.

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First, Average S-wave velocity in the uppermost 30 m (Vs30) obtained from PS-logging data and site amplification factors for peak acceleration and velocity derived from strong motion records are compared at the dense strong-motion network sites in Yokohama (Y-NET). Next, a simple method for estimating Vs30 is examined at Y-NET sites. This method involves placing 3 sensors in the shape of the letter ‘L’ for simultaneous microtremor observation. Finally, a method to estimate peak ground acceleration and velocity using Vs30 is proposed and its applicability is investigated.

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In this study, a truck tire loading device is produced and, with this, the influence of the contact shape of a truck tire on the plate-bending stresses in aluminum decks is clarified. First, the characteristics of the contact shape and pressure of a tire are revealed and the relations of load are formulated with the contact area, the average contact pressure and the contact radius of a tire. Next, the investigation on the plate-bending stresses occurring in an aluminum deck shows that the relation between load and the plate-bending stresses is nonlinear. Last, the comparison of the plate-bending stresses produced by truck-tire loading and rectangle-area loading discloses that the plate-bending stress created by rectangle-area loading is not on the safe side.

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The objective of the present study is to analytically investigate the inelastic behavior of H-section beam-columns, used in steel bridge structures, under cyclic loading, which will serve as the starting point for development of a seismic performance evaluation method for H-section steel members. Cantilever H-section members with various dimensional and loading parameters are subjected to combined constant axial force and varying lateral loading, both about strong axis and weak axis. The numerical method employed can take into account the effects of local, flexural and lateral-torsional buckling in both monotonic and cyclic loading. Validity of the numerical model is confirmed through comparison with experimental results. The numerical results are then summarized to elucidate the failure mechanisms. The difference of failure modes in cyclic loading from those in monotonic loading is highlighted, which needs to be given particular attention in seismic design of steel structures composed of H-section members.

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In order to analyze failure phenomena, it is important to use heterogeneous models instead of an ideally homogeneous one since crack path is strongly influenced by the presence of local heterogeneities in the real deformable bodies. Numerical Monte-Carlo simulation is not feasible for such heterogeneous models if each simulation is computationally expensive. The authors are proposing FEM-β to solve this problem. The present paper provides two examples of Monte-Carlo simulation of analyzing crack path in heterogeneous models. The probability density functions of the crack paths are obtained, and they are compared with the path of the ideally homogeneous model. The usefulness of the Monte-Carlo simulation of heterogeneous models for failure analysis is discussed.

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A new practical method is proposed for evaluating the failure probability of the intake tunnel for seismic PSA of the nuclear facility. The strength of the structure is specified by the limit deformation angle between the adjacent slabs and the realistic response of structure is expressed by its maximum deformation angle. The median for the stochastic characteristics of the actual response is evaluated by the non-linear seismic response analysis using FEM. The variation is evaluated conveniently based on the semi-empirical relationship between the deformation angle of the ground and that of the structure. By using this simplified method the computation time to obtain the variation was reduced extremely. The method is applied to evaluate the failure probability of the two stories intake tunnel with seven walls as the partition. As a result, the failure probability was obtained to be about 0.13 for input motion of maximum acceleration of 900 Gal. It was also found by comparing the FEM and semi-empirical methods that the estimated deformation angle by the simplified method has a sufficient accuracy for a practical use because the estimated error is less than10%.

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The deterioration of concrete structures by an alkali aggregate reaction is the important issue. It is necessary to build up the numerical analysis method to reproduce alkali-aggregate reaction which causes cracking or the fracture of steel bar. In this study, a numerical model is proposed in order to simulate the behaviors of concrete structures damaged by the alkali aggregate-reaction and is implemented into a finite element analysis code. Numerical results simulated by the proposed method and measurement data, such as the distribution and deformation of cracks occured in the bridge abutment damaged by the alkali aggregate-reaction, are compared. By considering the comparisons of the numerical results and the measurement data in terms of the distribution, deformation and fracture energy of cracks, it is clarified that the proposed method is able to predict the behaviors of concrete structure damaged by the alkali-aggregate reaction. It is considerd that the proposed method has availability for the prediction of the deterioration of concrete structures damaged by the alkali aggregate-reaction.

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It is important to clarify the stress transfer mechanism through the contact surface between steel and concrete, or by the shear connector in steel-concrete hybrid structures. In this paper, the effect of the bonding and frictional action between steel and concrete contact surface, and the mechanical action by the stud shear connector on the shear strength and shear transmission behavior of the contact surface under the bearing stress is investigated by conducting the push-out test. Furthermore, the fatigue strength of the contact surface between steel and concrete with the stud shear connector under the bearing stress is investigated by employing the same push-out test. As a result, the static and fatigue bonding behavior of the contact surface between steel and concrete with the stud shear connector is clarified experimentally.

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The bottom thickness increasing method is a rehabilitation work for RC slabs of highway bridges that places reinforcing bar under the existing slabs and sprayed mortar. Expressway bridges can be kept opening even during this rehabilitation work, so that this method has been applied for the bridge slab under heavy traffic condition. This rehabilitation method improves mainly the flexural strength and the shear strength of existing slabs. In order to assess the strengthening effects of this rehabilitation method for RC slabs, this study carried out the fatigue tests of RC beam specimens and the wheel running fatigue tests of real scale slab specimens with this rehabilitation work. As the results of the tests, it was clarified that the fatigue test of RC beam specimen was useful for the assessment of strengthening effects of the rehabilitation method as well as the wheel running fatigue test. As the result of these fatigue tests, it was found that the fatigue durability of RC slab was improved by the bottom thickness increasing work.

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In this paper, the method of determining the seismic design force is proposed by evaluating the seismic risk cost. The relation between the total costs and seismic forces of the input earthquake wave is calculated applying the structural optimization technique proposed by the authors. The seismic force that gives the minimum total cost is called as the target seismic design force. Here the total cost is defined as the summation of the initial construction cost and the seismic risk cost. It is shown that the different values of the target seismic design force are obtained depending on the applying seismic hazard curves. Also the numerical examples considering the several values of user costs are shown.

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In this study, durability of hot dip galvanizing, zinc-aluminum alloys, zinc-aluminum pseudoalloys and aluminum alloys was examined by salt water spray and acid rain spray combined cyclic corrosion tests. The differences of deterioration characteristics between the salt water spray and acid rain spray combined cyclic corrosion tests were investigated. As a result of the test, it is clarified the coating thickness loss of zinc hot dip galvanizing, zinc-aluminum alloys, and aluminum alloys by acid rain spray combined cyclic corrosion test was larger than that one by salt water spray test combined cyclic corrosion test.

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A new self-centering damage-free seismic resisting system is proposed for steel portal-frame type bridge piers by applying post-tensioned energy dissipating connections (PTED connections) to the beam-to-column connections together with the columnbase-to-footing connections. In this system, the two columns of the portal frames are connected to the footing and the beam by the post-tensioned high strength strands running parallel to the column axes. At the same time, both the beam-to-column and columnbase-to-footing connections include energy dissipation rods installed at the column flanges in the vertical direction. The post-tensioned high strength strands remove the residual deformation of the energy dissipation rods after earthquake, while the semi-rigid action of the PTED connections controls the magnitude of the connection moment and dissipates the kinetic energy of the frames. The advantages of the proposed seismic resisting system over the conventional regid-frame system are examined in terms of the volume of steel obtained as a result of optimum design. In addition, the characteristic seismic behavior of the self-centering damage-free seismic resisting frames is discussed.

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This study is the report that carried out field welding procedure test in a hybrid joint of the bolt joining and the welding joining with 3% Ni-advanced weathering steel. At first, this study showed a welding characteristic of 3% Ni-advanced weathering steel. Next, we performed welding execution of a flange and a web after having tightened a bolt of a longitudinal rib and a horizontal stiffener as application procedure in a hybrid joint. At that time, we measured the shrinkage by welding, and the sliding situation of a bolt. We also carried out slip test of the join surface that sliding produced once, and we made it clear that fall degree of a sliding proof stress. Based on these results, we suggested application procedure in a hybrid joint of the bolt joining and the welding joining in the construction spot.

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Since the Great Kobe earthquake in 1995, the seismic design of infrastructures in Japan was revised greatly in many items. But as far as the bridge piers are concerned, the design concept based on the conventional single directional seismic force has remained, not taking into account the actual bidirectional horizontal seismic forces. In this study, the strength and ductility of rectangular cross section steel bridge piers subjected to bi-directional horizontal forces are investigated experimentally in order to provide the basic information to establish the rational design rules. As the first stage of this research, the actual seismic response is idealized into several simple histeretic loading patterns, such as linear, circle, oval, radial, square and octagon types. The different seismic performances are obtained according to these loading patterns.

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Liquefaction array observation have been performed since 1990 at three sites on soft ground in Tomakomai-City. Orientation errors of accelerometers have previously been examined. However, there were some problems in the observed records, which were used for analysis. Therefore, orientation error examination was conducted again using new appropriate records. As a result, 2 accelerometers in Site A and 1 accelerometer in Site C were corrected for orientation error. Non-linear characteristics of the surface layer during the earthquake at Site A were studied by an observation records. Therefore we verified validity of past results. However, it was confirmed that results of the past analyses were correct because the influence of the orientation error was small.

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