This paper presents the numerical simulation of reproducing model experiments of fault and actual surface earthquake faults. Suitable stochastic models are constructed for experimental samples and actual under-ground structures. It is shown that the fault conguration obtained by the simulation is in quantitative agreement with the observed one. The failure probability, which is a faction of input base slip, is computed from the simulation so that probability of fault formation is evaluated.

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 This paper shows the estimation method of bridge m ode shapes based on dynamic responses of passing vehicles on a bridge and its verification by numerical simulation. The proposed method includes four steps: (1) estimation of input displacement to a mon itoring vehicle, (2) dedu ction of a ro ad roughness from the estimated displacement to obtain a bridge displacement, (3) transfor mation of the bridge displacements obtained by moving vehicl es to those assumed to be measured at the fixed locations on the bridge, and (4) mode estimation from the transformed displacements by singular value decomposition. To verify the estimation method, measurement errors, velo cities and masses of the vehicles, types of road roughness, and mode shapes were varied in numerical simulations. As a result, it was found that using three monitoring vehicles the first mode shape can be detected with high accuracy in all assumed cases, but, much improvement should be done to estimate the higher mode shapes.

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 A new simple method for estimating the amplitude-dependent site amplification factor (that takes soil nonlinearity into account) is developed with the objective of precisely predicting ground motions for seismic hazard analysis. Amplitude-dependent amplification factor is simply calculated from one ground parameter, AVS30 or S_n-value obtained from SPT N-value, and the ground motions on reference bedrock derived from existing attenuation relationship. The ground motion indexes for the amplification factor are PGA, PGV, and 5%-damped acceleration response spectra. The proposed method leads to a reduction of the variability of the observed records compared to the conventional method that does not incorporate amplitude dependency.

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 The tests were conducted using full-scale welded plate girders (L =6.4m, H =1.044m) with cross-beam connections in order to investigate the fatigue streng ths of various temporary repair methods for fatigue cracks and the improvement effect of repair methods for decreasing local stress in gusset joint. As the temporary repair methods, drilling stop holes, tightening H.T.B at the st op hole and patching the plate were used, and the effects of repair were confiremed by the fatigue tests. Additionally, as the improvement of fatigue strength on flange gusset and web gusset, it was studied on the reduce of stress concentration by the patching plates. As the results, the repair effect by the drilling stop hole was low, the effect of patching plate was better than another metods. And, in case of the improvement of fatigue strength by patching plate, it was confiremed that the stress was reduced by setting the H.T.B at the position of stress concentration.

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 In this study, the improvement of low cycle fatigue strength by toe finishing technique was investigated experimentally and analytically. T-shape welded joints with different plate thickness were fabricated, and weld toes of some specimens were finished by TIG-dressing or burr-grinding. The low cycle fatigue test results demonstrated that the crack initiation lives of finished specimens were much longer than those of as-welded specimens. We also analyzed the local st rain around the finished zone and investigated the geometric effects on the local strain. Parametric analyses carried out by finite element analyses demonstrated that the local strain was strongly influen ced by the radius and depth of the finished dent as well as the main plate thickness. Finally, we proposed a simple equation to estimate the fatigue strength of the welded joints includ ing the geometric effects.

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 An equation for shear force-slip relationship including residual slip and ultimate slip of shear connector is necessary to rational design of composite structures. Shear force-slip relationship of the headed stud connectors is generally obtained by a pushout test. It has been cralified that external force in the axial direction of stud affects to the shear force-slip relationship. However, effect of restriction to concrete block in the pushout test on that relationship has not been cralified. Therefore, a pushoff test and pushout tests in which restrict condition of concrete block is changed were carried out in this research. Experimental results made it clear that difference of test method affects to not only shear strength but also load-slip relationship. Behaviors of axial direction of stud depending on the test method can be explained by a proposed wedge concrete model.

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 Generally, corrosion state depends on the part of bridge girder section because the effects such as wind velocity distribution, humidity, raindrops washing, are different in each part of the section. Windborne salt adhesion by the wind transportation is one of the important factor which governs the corrosion state. In this study, wind tunnel test including small particle diffusion and adhesion to the bridge girder section model is executed. Furthermore this result was compared with the ones of flow visualization experiment and the observation of the windborne salt adhesion on bridge girders. It is considered that this is the first step to build the partial corrosion protection to make the life of the bridge longer.

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 In CFRP bonded steel plate, thermal stress is induced in steel plate, CFRP strips and adhesives by temperature change, due to difference in coefficients of thermal expansion between steel and CFRP. In this study, to reduce the thermal stress induced in CFRP bonded steel plate, additional bonding of aluminum alloy plates which have about twice higher coefficient of thermal expansion than that of steel plate is proposed. To verify the effectiveness of reduction of thermal stress, theoretical and numerical analyses were carried out.

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 In the application of CFRP plate onto steel plate, stepping the CFRP plate ends is often used for prevention of debonding of CFRP plates. However, the length of CFRP plate becomes long by using stepped ends. In this study, to shorten the length of CFRP plate, aligning of several CFRP plate ends was proposed and the condition of aligning was theoretically given. Additionally, aligned steps of CFRP plates under uni-axial load were designed. It was confirmed with stress analysis that the stress in steel plate was reduced as design value by bonding CFRP plate with proposed stepped ends.

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 A framework for the risk management of power dist ributions was developed, which consists of the fragility curve of the electric pole, the typhoon hazard curve and the minimization method of expected total cost. The fragility curv e of the electric pole was constructed by the damage data caused by Typhoon 0314 and the local gust wind speed in Miyakojima evaluated by a CFD model. The typhoon hazard curve at the individual location of electric pole was constr ucted based on the annual maximum gust wind speeds obtained from the typhoon simulation and the local wind prediction. The optimum design wind speed for each pole was decided by using the minimization method of expected total cost. The expected total cost in the design life of the poles by the proposed mitiga tion measure was reduced by 13% comparing that by the current design.

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 This paper proposes a numerical prediction scheme of dynamic behavior of vehicle-bridge interaction system with the main focus on steel girder bridges. Using general software ABAQUS and MATLAB, a detailed finite element model of the bridge uner the passage of vehicles is developed, in which the de-coupled equations of motion of the vehicle-bridge system are derived and the effect of road surface roughness is included. Interaction forces between vehicle and bridge systems are calculated step by step using Newark's method. The numerical model is applied to a skew steel bridge which was monitored under in-service traffic loads. After adjusting boundary conditions of the model with the measurements' and computing the spectral roughness coefficient-the most influential but also the most uncertain parameters of the model-good agreement is obtained between the simulation results and field measurements. The study shows that using numerical simulation, not only the global response, but also the local behavior of the bridge could be investigated quantitatively. Finally the parametric analysis is carried out and capability of the proposed prediction method is confirmed.

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 Fatigue crack propagation behavior in T-shape welded joints subjected to out-of-plane bending and shear force was investigated. Firstly, the redistributio n of welding residual stress due to crack extension was investigated analytically and experimentally. Afte r the crack propagates more than about 60% of the main plate thickness, the residual stress was almost re leased. Secondly, fatigue tests on T-shape welded joints was conducted in order to grasp the crack propagation behavior. The condition that main crack arrests can be evaluated by calculating effective stress intensity factor range. In some test cases, although main crack arrested, the specimen was broken due to the initiation of counter surface crack. It was demonstrated that the initiation of counter crack was a ssessed based on plastic strain in counter surface by elasto-plastic finite element method.

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 In this research, fatigue strength improvement method which combined cleaning treatment with a grinder and hammer peening treatment is investigated. The condition of the hammer peening treatment is determined by hardness and surface texture. The improvement effect on both fatigue crack initiation life and the fatigue crack propagation life is clarified from the fatigue test with the out-of-plane gusset joint and its improvement mechanism is discussed from the view points of stress concentration and residual stress. The retardation effect of crack propagation due to the compressive residual stress, which is induced by the peening treatment, exists even if the fatigue crack propagates into the region where the tensile residual stress had originally existed. The proposed method can improve both the fatigue crack initiation life and the fatigue crack propagation life.

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 Welded joints between main girder web and lateral girder flange in girder type steel bridges are usually subjected to bi-axial stresses which are stress on the web and stress on the flange. In this study, for the purpose of obtaining the estimation formula for fatigue strength of the welded joints considering influence of bi-axial force, 3-D FEM stress analyses and fatigue tests have been performed on model specimens with various weld shapes and plate thickness. In this formula, stress increment due to bi-axial force has been paid attention. The estimation formula could simulate the tendency of the fatigue test results.

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 UIT (Ultrasonic Impact Treatment) is the method to impact on weld toe with hard pins vibrated by ultrasonic energy, so that improving the weld toe prof ile and introducing compressive residual stress can be obtained. It is confirmed that UIT has high improving effect on fatigue strength of welded joints through many experimental researches. Those tests were conducted under low stress ratio and UIT was done in condition that specimens were not subjected to stress. When UIT me thod is applied to existing structure, its effect should be verified in condition that UIT is applied under loading and fatigue tests are performed under high stress ratio. In this study, the improvement effects have been examined under such conditions.

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 In this research, a retrofit method using combination of carbon fiber reinforced polymer sheet (CFRP sheet) and steel jacketing was studied for upgrading seismic performance of reinforced concrete (RC) bridge columns that termination sections of the longitudinal reinforcements were already retrofitted with CFRP sheet jacketing in the first stage of the seismic retrofit strategy. This method takes advantage of both steel plate and FRP sheet, in which steel jacketing is adopted forstrengthening theflexuralcapacityofthecolumn basewhereplasticdeformationisexpected tooccur during the large earthquakes and CFRP sheet jacketing is adopted for strengthening the other sections of the column. CFRP sheet is connected to the steel plate by means of bonding with epoxy resin. Double-lap shear bond tests, cyclic loading tests on RCcolumn specimen and three-dimensional FEM analyses were conducted forestablishing design method. As the results of discussions, design method of the connection between CFRP sheet and steel plate was proposed and the e ff ectiveness of the proposed retrofit method was confirmed.

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 A slip coefficient controlling the slip resistance of friction type of high strength bolted connections is considered to depend on the surf ace roughness of a friction surface of st eel plate. A lot of studies have been done about relationship between th e slip coefficient and surface roug hness so far. However, in those studies, various testing conditions and surface roughness parameter were used. In this study, in order to clarify appropriate parameter for arranging the influe nce of surface roughness on slip resistance, the tensile tests and surface roughness measurements on fric tion type of high strength bolted connections with various surface roughnesses are performed.

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 This feasibility study examined the design and the serviceability of a newly proposed pedestrian slab bridge using GFRP pultrusion profiles bonded together by adhesive layers. The innovative feature is the appropriate adoption of semi-fixed support conditions with anchor bolts at both ends, in order to sharply reduce the bending deflection and to drastically improve the economic efficiency. In this paper, the validity of the development of the new type bridge is verified from results of a material design and tests, a trial structural design and partial model tests with real size. In addition, the practical design deflection calculation formula which can consider the shearing deformation is proposed, and the examination of the review of the limiting value which influences the economical efficiency directly is also carried out.

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 Structural parameters of existing arch bridges constructed after 1972 were studied using a more comprehensive data set obtained from deck-type steel arch bridges design. Ten structural parameters were investigated, namely, 1) arch span-width ratio, 2) arch span-raise ratio, 3) in-plane slenderness ratio of arch ribs, 4) out-of-plane slenderness ratio of arch ribs, 5) ratio of dead load to yield axial force, 6) lateral slenderness ratio, 7) ratio of lateral panel length to arch width, 8) steel weight per unit road area, 9) height of arch rib, and 10) height of girder. Using structural parameters described in this paper one can examine the bridge structure more easily for a given arch span.

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