In recent years, high damping rubber (HDR) bridge bearings have become widely used because of the excellent ability to provide high damping as well as flexibility. However, there are few systematic studies on the deterioration problems of HDRs during their service life, and usually the long-term performance was not considered in the design stage. In this research, through accelerated thermal oxidation tests on HDR blocks, the property variations inside the HDR bridge bearing are examined. A deterioration prediction model is developed to estimate the property profiles. Then using a constitutive model and carrying out FEM analysis, the behavior of a HDR bridge bearing during its lifespan is clarified. A design procedure is proposed that takes the long-term performance in the site environment into consideration.

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In this study, the oscillation behavior and the aseismicity of bridge piers with isolating foundations are investigated. An isolating foundation is formed by installing isolation materials such as sand, gravel and PTFE (Teflon sheet) between the footing and the pier foundation and mainly utilizes the relative displacements (sliding and rocking) between the footing and the foundation to absorb and dissipate energy during large-scale earthquakes. The governing equations of motion are derived and dynamic response analyses and model vibration tests on a single pier are carried out. The results show that this isolating system has a significant positive effect in decreasing responses during earthquakes.

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In this study, influence of corrosion on fatigue strengths of parent material and its joint by the friction stir welding (FSW) of extruded A6N01-T5 is clarified. The specimens of them are exposed at Okinawa, and investigations of corrosion are carried out on them after the atmospheric exposure in a half, one and two years. The relation between corrosion and fall of fatigue strength is clarified after fatigue tests of the corroded specimens. The form of the corrosion is intergranular corrosion. The erosion in the direction of the depth of each intergranular corrosion does not proceed after a year. Fatigue cracks are generated from the intergranular corrosion. The fatigue strength after the atmospheric exposure falls to 72% on the parent material and to 85% on the FSW joints.

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The dynamic characteristics of elevated bridges due to Shinkansen trains are investigated by means of three-dimensional dynamic analysis, considering the train-bridge interaction. Trains modeled as two-, six-, and nine-degree-of-freedom dynamic systems are adopted as analytical models and the influences of different train models are examined to find the rational one. Analytical results are compared with experimental ones to demonstrate the validity of the analytical procedure. The vibration characteristics of the bridge are evaluated according to the analytical results. As an application of this analytical procedure, countermeasures to reduce the undesirable vibration are proposed and examined.

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In this paper, a size optimization problem of structures is discussed from the point of limit analysis. A size optimization problem defined here is the minimization of a cost function on the strength distribution of structures subjected to the static and plastic constraint conditions for a given external load. To this end, a new Lagrangian function is proposed for this optimization. According to the Lagrangian duality theory, its duality and complementarity condition are also derived. In addition to this, a numerical algorithm based on the interior point method is formulated in details. Finally, validity of the proposed numerical algorithm is confirmed by two size optimization problems; namely, a cantilever problem and a flat punching problem.

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Studied herein is the strength, ductility and energy absorption capacity of steel plate profiled transversely under uniform compression. In order to assess the effect of the taper ratio of steel plate thickness on the structural performance, the elasto-plastic finite displacement analysis is carried out, varying the taper ratio as well as the plate slenderness parameter. The analysis is also extended to assess the bending performance of I-shaped steel member with tapered flange and web. It is concluded that the transversely profiled steel plate in the shape of convexity can have superiority in strength, ductility as well as energy absorption capacity.

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The seismic response characteristics of semibasement structures using steel pipe piles as main walls are studied under L2 level strong seismic motions in longitudinal direction. First, the influence of ground conditions and width of structures to the response behaviors are examined based on seismic deformation method. We find that the longitudinal seismic inputs produce larger responses than those of transverse seismic inputs, the possibility to produce the damage in the main structure is small if expansion joints are used every 20m, and the deformations of steel pipe joints are slightly big because of the concentrated deformations are produced in the expansion joints. In addition, it is showed that the seismic deformation method has enough precision in practical use from the comparison with 2-D and 3-D FEM analyses.

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One of the possibilities of the efficient connection of steel-concrete composite structures is the grouped arrangement of headed stud connectors. An analytical study of the smaller spaced grouped arrangement of headed stud connectors on stud size and on stud strength is carried out and the influence of these parameters on the shear strength is investigated on the basis of the failure mode. Moreover, an estimation method of the shear strength of headed stud connectors allowing for the influence of stud size, stud strength, concrete strength, and grouped arrangement is proposed and the shear strength of the slabs close to the grouped arrangement of headed stud connectors is evaluated.

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Emergency medical care is very effective to save the lives of injured people in traffic accidents. The heliambulance has been under operation since 1999, and it is expected to contribute for the emergency medical care. However, the heliambulance is allowed to land on the expressway under only some restricted conditions, because the heliambulance generates strong wind called downwash. In this study, the moving stability of vehicles under crosswind generated by a helicopter is investigated based on field experiments and numerical simulation. Based on these results, the possibility of landing of a heliambulance on expressways is discussed.

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Long-term maintenance planning is able to reduce maintenance cost. our model is constructed from 60 elements. The maintenance plan must keep required performances for service life. To make long-term maintenance plan is considered to the combinatorial problem with many constraints. This kind of problem is very difficult to obtain a solution. We applied Improved Genetic Algorithm for this problem.
We develop new DNA structure and new natural selection. It is very easy construction and very efficiency for searching long-term maintenance plan. Numerical example was formulated and we could obtain good solution.

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Chordwise and spanwise correlated properties of surface pressures and gust forces (lift force, pitching moment) on a rectangular cross section due to vertical gusts were investigated through wind tunnel experiments. Relationships between these characteristics and the intrinsic flow pattern with separating shear layer around the cross section were focused through the discussion. A 2-D model with rectangular cross section (B/D=5, B: chord length, D: depth) was used for the measurements and discussion. In the 2-D sinusoidal gusts, the formation of separation vortex near the leading edge and its convection to the trailing edge were deduced based on the unsteady pressure on the side surface. It was confirmed that this flow pattern was realized only in the characteristic reduced frequency domain where the shear layer instability is enhanced by the approaching vertical wind fluctuations. The spatially expanding characteristics of the surface pressure along chordwise as well as spanwise directions were captured in the 3-D gusts. The amplitude of vertical wind velocity is not uniform along spanwise. It was concluded that the separation vortex is hardly expanding towards spanwise direction, but that the entire formation of the separation bubble in lower reduced frequency than the characteristic frequency domain encourage the pressure transport. This observation agrees with the higher spanwise coherence of gust force in lower reduced frequency.

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This paper presents an improvement of a particle swarm optimization method and its application for an optimal design of skeletal steel check dam. In order to improve the search efficiency, the conventional particle swarm optimization method is modified by adding both the search range constraint and the random search term. The efficiency of modification is studied by using a basic 2 dimensional nonlinear function problem. And it is shown that the search range constraint works well in the initial search process and the random search term works well in the final convergence process. To confirm the applicability of the proposed method, it is applied to the member section optimal problem of the steel check dam structure and confirmed the applicability.

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In the Monte Carlo Filter (MCF), the probability density function of the state vector is approximated by many particles. In the classical MCF, however, as the degree of freedom of structural mode lincreases, the number of particles to be generated is increased in exponential order. This results in extreme increase of computaion time. In this paper, we develop the Relaxation MCF, in which we improve the filtering process of the classical MCF. Moreover, we develop the GA-RMCF, which combines the Genetic Algorithm (GA) and the RMCF. We apply the GA-RMCF to identifying the dynamic parameters of a five-story model building using observed data obtained through the shaking table tests.

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The purpose of this study is to develop an analytical method for low frequency noise radiated from bridges due to moving vehicles. The boundary element method is used to predict the low frequency vibration to overcome drawbacks of the simplified conventional method. The validity of the procedure is verified by comparing with a measured sound pressure level. As an application for this method, effects of the end-cross beam reinforcement as a countermeasure against the low frequency vibration are investigated. Observations reveal that the developed method can provide a good tool for predicting the low frequency vibration radiated from bridge structures.

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Since common utility tunnel is very lightly reinforced without cross bars between inner and outer bars, it is vulnerable to the seismic effects. Effectiveness of seismic retrofit was clarified based on cyclic loading tests on six specimens. They are prototype models at the side wall connected to the lower slab joints. Full penetration anchor bolts and bolts with a special device which enables to anchor at mid wall height were used to confine the concrete and prevent shear failure. Carbon fiber reinforced plastic sheets were also used in the retrofit. Number of CFRP sheets and anchor at the slab was varied. It was found from the experiment that the as-built tunnel failed in shear at the wall-slab joint. The retrofit by bolts and CFRP is effective to enhance the shear capacity and ductility.

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Recently, some kinds of fatigue cracks have been discovered at the welded connection between trough rib and deck plate in the steel plate deck. In this study, finite element stress analyses, stress measurement tests and fatigue tests on model specimen for one panel of steel plate deck are performed in order to examine the cause of fatigue cracks originating at the welded joint between trough rib and plate deck and the influence of weld penetration depth and position of wheel load on stress properties.

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Fatigue strength of corroded steel wires were investigated in this paper. Specimens of different corrosion level galvanized wires were produced by wrapping with wet gauze and kept at high temperature, simulating cable corrosion environment. Fatigue strength decreased sharply after the zinc layer consumed and the steel started corrosion. The fatigue strength in wet environments decreased, comparing with dry environment. The observation fracture of every specimens shows that the crack initiation position is the corrosion pit on the wire surface. It was estimated that this decline of fatigue strength with progressing corrosion was caused by stress concentration of corrosion pit, and the decline in wet environment was caused by cooperation of corrosion and fatigue.

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In general, the hybrid girder consisting of different grades of steels for the web and the flange is superior in the cost to the homogenous girder consisting of same grades of steels. However, for the hybrid girder, the width to thickness ratio of web is required to be smaller than that for the homogeneous girder because of yielding of web before flange yields. In this study, proposed is the composite hybrid girder with newly developed high performance steel, in which the web and the upper flange are made of the normal grade steel, but the lower flange is by the high performance steel. It is demonstrated experimentally that by making the width of rectangular box section narrow and combining the hybrid girder with RC/SW slab, the web can be a non-stiffened thinner plate with the large width to thickness ratio, so that the proposed girder system can contribute the cost reduction.

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Two-girder bridges are prone to oscillation due to wind such as the torsional vortex excitation. In order to estimate a wind speed of the excitation, it will be necessary to evaluate the fundamental vertical and torsional natural frequencies at an initial stage of bridge design. According to the conventional beam theory, this paper provides a practical method to evaluate the fundamental natural frequencies of these bridge structures. Effectiveness of the proposed method is discussed for existing highway bridges of two-girder type compared with the evaluated and computed natural frequencies. These results showed that the present method could estimate the fundamental vertical and torsional natural frequencies with sufficient accuracy and less complexity.

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