This paper presents the results of experimental studies to examine propagation of fault ruptures with particular concern on dip-slip fault. The pattern of rupture propagation through a sandy soil and the location of surface rupture were investigated. The distortion of surface ground accompanied by fault rupture has been examined as well. The 1-g model tests showed that the location of surface fault rupture varied depending on the model thickness due to strongly dilatant behavior of sand under low confinement. However, the increase of confinement at centrifuge models provided no definite variation of the location against the change of model thickness, which suggested the importance of interpretation about the results from small scale sandbox test.

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A new analysis method, which is a hybrid of the Finite Element Method (FEM) and the Distinct Element Method (DEM), is proposed for fracture analysis of continuous media. The basic concepts of the new method are introduced in contrast with the conventional DEM. In the new method, three distinct elements are connected by one equilateral triangular finite element (constant strain). The efficiency of the new method is evaluated through static, fracture and re-contact analyses for several kinds of materials. Finally, as an application of the developed method, dynamic fracture analysis of surface ground on a non-uniform base rock is carried out under seismic wave and estimation of pipeline's damage is also conducted.

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In this study, we performed parametric analyses to examine the fault rupture process and generated earthquake motions near a fault by using three dimensional (3D) finite element method. First, we examined the validity of our method by comparing the work done by Day. Next, the effect of the direction of the rupture propagation were studied. Then, the effect of the length of the fault on the rupture propagation process, magnitude of dislocation on the fault plane, and generated earthquake motions. Finally, the comparison between the results from 3D analyses and those from 2D analyses was made.

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The three-dimensional propagation directions of earthquake waves near ground surface were estimated for eight earthquakes. Travel times of the incidence and reflected waves were obtained by using the Normalized Input-Output Minimization (NIOM) method, and 3-D angles of propagation directions were estimated. The estimated directions correlated well with the theoretical ones calculated from the epicenter coordinates, focal depth, and the velocity distribution in the earth's crust. However, the estimated angles (0-20 degrees) from the vertical axis for the observed waves were somewhat larger than the theoretical ones (0-4 degrees).

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Many cases of fatigue damage on “the orthotropic steel deck structure with box girder” have been reported. There is a pressing need to identify the causes and to retrofit these bridges. This damage is caused by the complex behavior of the deck, which is directly subjected to vehicle loads. This paper discusses our investigation of the mechanism of fatigue damage that occurred in an orthotropic deck bridge. The investigation was performed by comparing field measurement results with the analytical results from a fine-meshed FEM model. We explain the characteristics of the stress and deformation behavior which dominate the fatigue damage on this type of bridge.

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A computational method to predict long-term corrosion loss to occur on weathering steel is studied. An algorism to obtain kinetic parameters to predict penetration curves for bare and surface treated weathering steels is outlined, based upon recently established durable state concept. The proposed computational scheme also contains a meteorological database, an air-born salt simulator, a sulfur oxides estimator, etc. The most important argument in this paper is in the clarification of various parameters which are related to the extent of future degradation to occur on weathering steel members. These parameters should be systematically shared among engineers to establish minimum maintenance durable steel structures. Expecting further development, the authors explain all contents of the presently established corrosion prediction system in details.

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High strength bolted L-stub joints are expected to be used in connections of members with box cross section, because of their good mechanical properties and appearance. However, they are not utilized for connecting these members of actual bridge structures due to lack of enough information of their mechanical behavior for design. The deformation of the tee flange/web plates of L-stub joints may considerably affect the mechanical properties of this type of joints such as the ultimate strength, the distribution of contact stress between the joint surfaces and so on. In this study, the effect of the thickness of the tee flange/web plates on the mechanical behavior of L-stub joints is discussed analytically.

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In through truss bridges, severe corrosion damages have been observed at the diagonal members in boundary with concrete slab. The similar structural details are also used at boundary of web and flange in corrugated steel web PC bridges. In the future, the similar type of corrosion damages with the truss bridges seems to occur in the PC bridges. In this study, in order to clarify the corrosion behavior for the steel structural members in boundary with concrete, accelerated exposure tests were carried out on model specimens. And classification of the corrosion characteristics and the corrosion regions were analyzed using variograms and regression trees. As the result, corrosion behaviors at boundary and general corrosion region and that of anode region were clarified. Quantitative evaluation and estimation methods for corrosion behaviors in boundary with concrete of the steel members were also proposed.

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Response delay of MR fluid results in distortion of the control force of MR dampers. This results in problems when we use MR dampers as variable dampers. To mitigate the time delay of MR dampers, the PID Control was used. Overshoot termination control (OTC control) and 2-step PID Contol were proposed. A series of cyclic loading test for a Lord Corporation MR damper and a shaking table test of a model bridge with the MR damper were conducted to verify the effectiveness of the PID control. It was found that the PID control is effective to mitigate the time lag for friction control.

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By adoption of the grouped arrangement of stud shear connectors in steel-concrete composite constructions, the prestressing force by tendons is able to introduce only in concrete member easily and effectively. As one of its example, an application of the grouped studs to the continuous composite girder was studied in this paper. In addition to the push-out test in static and fatigue of the grouped studs, the static and fatigue loading test of prestressed concrete slab by using the full-sized specimen was also carried out. The applicability of grouped studs to the continuous composite girder was confirmed by calculation example based on the test results and the design rules.

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The cable safety factor for cable-supported bridges in Japan is higher for other bridge members. The main reason is that the reliability of cable fatigue damage is not clear. We pay attention to cable fatigue damage due to live loadings, and investigate the relationship between cable fatigue damage and the safety factor of stay cables. We tentatively designed three-span continuous steel cable-stayed bridges by changing the cable safety factor and the center span length. The fatigue damage to the stay cables caused by random traffic flows was evaluated by Monte Carlo simulation. We arrived at the conclusion that the possibility of reduction of the cable safety factor is suggested in viewpoint of the fatigue safety.

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An effective width formula for crack width evaluation in negative bending moment regions near internal supports of continuous composite girder bridges is proposed. The formula takes account of shear-lag effect and includes cracking effect in concrete slabs of composite bridges. A parametric study of 3D nonlinear FE analyses for composite bridges with span lengths ranging from 30 to 60 m are carried out to develop the formula. Since the effective width varies depending on the strain level of concrete slabs due to nonlinear effects, a modification equation of the effective width is proposed as well.

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The verification of vertical response of bridge girders is important especially for the bridges with sliding isolation bearings, because the friction damping is not expected during the girder lifts up from the sliding bearing. This paper aims at evaluating the performance of the sliding type seismic isolation system for the vertical response of the bridges through the experiments and the numerical simulations. When the bridge girder lifts from the bearing due to the vertical response during an earthquake, the horizontal load distribution device undergoes tension force in the vertical direction, and the sliding plate undergoes impact force from the falling girder after floating. The test results and the numerical simulations show that the device holds the function as a seismic isolator even after the vertical movement of the girder.

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A cyclic bi-axial loading experiment has been carried out to examine the ultimate seismic behavior of thin-walled steel circular columns by using the accurate 3D-loading system recently developed by authors. The cyclic circular loading is adopted as one of the severest bi-axial loading patterns for circular columns. The results of the experiments are also used to confirm the applicability of the nonlinear FEM shell analysis where the three-surface cyclic plasticity constitutive model is implemented. With the nonlinear FEM analysis as well as the experiment, the potential decrease in the maximum horizontal restoring force and ductility of circular columns under cyclic bi-axial loading are quantitatively evaluated in comparison with that under in-plane cyclic loading.

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Under the tight financial condition of each local government, public investment including investment in bridge maintenance is continuously reduced. Since preventive maintenance is the optimum policy from the viewpoint of LCC, the present successive reductions cause concern for inevitable huge future expenses. In this study, future BHI under several secular scenarios of public investment are investigated. The difference in the time values due to the vehicle kinds are also considered. The yearly investment, by which the total investment in the project year can be minimized under various levels based on BHI, was calculated to study the possible optimum investment scenarios for maintaining a healthy condition.

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For sleeve joints between concrete-filled circular steel tubular column and steel beam, authors carried out the monotonic static loading tests by using the T-shaped joint specimens, and have proposed an equation for estimating the ultimate strength. However, an application of the equation to an actual structure needs to consider the effects of cyclic loading and the diaphragm, including the application of the proposed method to the cross-shaped joint. Then, in addition to the monotonic static loading tests, the static loading tests by using the T-shaped joint specimens were carried out in order to investigate the effects of loading method and the diaphragm. Moreover, the monotonic static loading tests by using the cross-shaped joint specimens were also carried out. The test results indicate that the loading method (cyclic or monotonic) and a diaphragm affect on the ultimate strength, and that the application of the proposed method to the cross-shaped joint is promising.

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Studied herein is the strength, ductility and energy absorption capacity of simply supported 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. It is concluded that the transversely profied steel plate in the shape of concavity can have superiority in strength, ductility as well as energy absorption capacity.

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Similarity of earthquakes is generally assumed for the prediction of strong ground motion for future large earthquakes. If earthquakes are similar, it is expected that short-period source spectral amplitude is proportional to one-third power of the seismic moment. Strong motion records at K-NET and KiK-net stations are analyzed and relationship between short-period source spectral amplitude and seismic moment is examined. Similarity is not found for the earthquakes analyzed here. Larger earthquakes radiate short-period seismic energy more effectively than smaller ones.

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