This paper presents flexural reinforced concrete single-column structures which will exhibit better seismic performance than conventional reinforced concrete columns. Some simple ideas for improving seismic performance were proposed based on the arrangement of longitudinal reinforcement. Cyclic loading tests were conducted for comparison of ductility capacity and damage level among the columns designed with the proposed new concepts and conventional one. Test results showed that the termination of some longitudinal bars near single-column base according to the actual bending moment action, the partial unbonding of longitudinal bars in the footing and the anti-buckled longitudinal bar arrangements were significantly effective for enhacing the ductile capacity of the columns.

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Hierarchical finite elements are examined for average mechanical behavior of composite structures. The formulation is formally similar to that of the overlaying mesh method, but its main purpose is to derive the element stiffness that is equivalent to the actual composite structures with local heterogeneities. The resulting elements possess additional internal degrees of freedom in the local finite element mesh for improving the performance and thus are nonconforming. In other words, the local structure with actual heterogeneities is reflected on the evaluation of the element stiffness matrix of a global element, so that a global element behavior is enhanced by the local degrees of freedom. Several numerical analyses are performed to examine the validity and accuracy of the proposed hierarchical finite elements.

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When a seismic analysis was conducted for infinitely long elevated bridge, generally, the boundary conditions for joint of a unit bridge have been considered as free. It has been also considered that the results of such analysis would be on safe side. In this research, the transmitting boundary for discrete system was formulated by using beam element model of 3 D. O. F, and its verifications were carried out. Furthermore, parametric analyses were carried out, which are dynamic analyses for structures applied harmonic excitation with various frequencies. As results, we have verified the possibility that responses considering the transmitting boundary could be greater than that of free boundary.

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The present study focuses on input loss of deeply embedded foundations that support bridges and viaducts. It is predicted that slippage and separation occur at the interface between soil and the sidewall of the foundations when subjected to strong motions. Therefore, it is desirable to know the effect of slippage and separation on the input loss. This study investigates the above effect by means of analytical approach based on a three-dimensional wave propagation theory, including the influence of inertial interaction due to the mass of foundation and superstructure upon the interface. The present study gives physical understanding of the effect of slippage and separation on the input loss.

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The major slip of high-strength friction grip (HSFG) bolted joint is the limit state on design, but it has more load carrying capacity after the slipping. When the South Hyogo earthquake was occurred in 1995, there were many bolted joints at which slip phenomena appeared, then the problem was the way of evaluating their load carrying capacity and repairing. This paper shows the characteristic investigation and the cyclic slip experiment of HSFG bolted joints that were damaged by earthquake. As results, the change of bolt tension, slip coefficient and slip load carrying capacity by cyclic slip tests are showed and the effect of energy absorption of HSFG bolted joints in big earthquake is discussed.

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The authors have investigated fatigue crack propagation behavior and fatigue life of welded joints under combined normal and shear stresses acting in phase through fatigue tests. In this study, methods of fatigue life assessment of welded joints under the combined stresses are investigated. Fatigue life assessment methods based on maximum principal stress range or normal stress range are reviewed. A method based on fatigue crack propagation behavior and the concept of maximum strain energy release rate is proposed. Using the proposed method, fatigue life under the combined stresses is in good agreement with that under normal stress, and thus fatigue design S-N curves of welded joints for the normal stress cycle can be applicable to the combined normal and shear stress cycles.

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Separately proposed rust evaluation techniques, such as visual inspection, thickness measurement, ion transfer resistance measurement, electrochemical potential measurement, ferroxyl spot rating test, X-ray diffraction analysis, are systematically studied based upon corrosion nature of weathering steels. Criteria for these techniques are revised according to the recently established durable state concept.

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This study shows mechanical properties of Channel-Shaped precast PC slabs (CPC slabs) by experiments and analysis. It clearly indicates that CPC slabs have a large load carrying capacity and high durability against the traffic load through a series of systematic experiments, static and fatigue tests. On the other side, bending moment distribution of CPC slabs using wheel live loads is different from ordinary flat RC slab, due to its channel shape. Therefore, we cannot use the bending moment calculation formulae of slab design using live wheel load that defined in the Japanese specifications for high way bridge. So, FEM analysis for CPC slab was carried out to provide the original bending moment calculation formula. And the design method of CPC slabs is shown in this paper.

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Fatigue cracks were found in beam-column connections of steel piers in the Metropolitan Expressway, and examination of retrofitting measures for these cracks has been proceeded. Total of 566 out of 2200 columns are found to have cracks in the connections. Detailed investigations of the damaged piers including opening of damaged weld bead, investigation of fabrication sequence were carried out with the piers which had comparatively large cracks. Starting point of cracks were turned out to be characteristic internal flaw which contain un-welded cavity and metal-touch zone in most cases. A damage database was constructed based on these investigations and fatigue damage modes of the steel pier are examined based on it.

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Bi-axial stress usually exists in welded joint between main girder web and lateral girder flange. For the purpose of examining influence of hi-axial loading on the fatigue strength, a test set-up has been developed to conduct fatigue tests under hi-axial loading. Fatigue tests have been carried out under the condition that stress range on the web was set at 100N/mm² and stress range on the flange was 0, 50, 100 or 150/mm². The fatigue life under bi-axial loading was drastically decreasing compared with the fatigue life under single axial loading. This fact was derived from stress increment due to bi-axial sress and stress bi-axiality itself, which was confirmed by stress measurement tests and stress analyses.

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Recently, it is recognized that the concepts of lifecycle cost (LCC) and lifecycle assessment (LCA) are useful to evaluate new technologies and decision-makings in the lifecycle of infrastructures. It is necessary to consider the effect in LCC and LCA when natural events such as earthquake cause damages for transportation infrastructures during their lifecycles. In this research, focusing on earthquakes that cause serious damages, lifecycle evaluations were performed considering probabilities of losses caused by earthquakes. As a result, it was shown that effects of seismic risk were not large in the case of only taking account of structural damages. However, when the user cost was also considered, the seismic risk showed a large value. Furthermore, when transportation infrastructures such as bridges are given different performance levels in a case study, it is shown that lifecycle cost of whole road networks can be minimized.

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The elastodynamic inversions for the ultrasonic pitch-catch mode are investigated in order to take advantage of the waveforms measured at multi-points. The inversion is based on Born or Kirchhoff approximation to linearize the integral expression for the scattered wave. The multi-point measurements are applied to the shape reconstructions for two flaws of a cavity and a crack. It is confirmed that the adjacent part of two flaws is clearly reconstructed by the multi- point measurements, even though the dynamic interaction effects of flaws are included in the measured waveforms.

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Ambient vibration measurement is a convenient tool for health monitoring of structures in service. The authors proposed a new procedure for structural inversion analysis from ambient vibration data, which resolves some problems of the previous methods. The main advantages of the proposed procedure are: for modal analysis, the method can distinguish noise from meaningful mode and deal with multi-input system; for the inversion analysis, the procedure does not require any assumption over damping, prior estimation of structural properties, or iterative approach. The method is applied to ambient response data of Hakucho Bridge. Since authors applied a different procedure for structural inversion analysis to the same bridge before, the results are compared and the effectiveness of the new method is demonstrated.

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Reinforced concrete C-bent columns with longer beams in one direction than the other are subjected to eccentric loadings in the vertical and the longitudinal directions. A cyclic loading test was conducted to 8 reinforced concrete specimens with various eccentricities. It was found that failure of concrete in the plastic hinge is extensive on the face where compression is induced resulted from the eccentricity. This results in a residual drift in the eccentricity compression side and a rotation of columns around the vertical axis. It was also found that the bilateral loading results in more extensive failure in the columns with eccentricity than the unilateral loading.

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Shaking table tests were conducted on foundation models to elucidate the dynamic behavior of existing foundations strengthened with micropiles and verify the effect of such seismic retrofit. The tests were then simulated by numerical analysis. Three models were used in the tests: a model representing the existing piles, model strengthened with vertical micropiles added in the front and back of the existing foundations, and model strengthened with battered micropiles. As the results of simulation by nonlinear seismic response analysis agreed well with the results of the experiments, the strengthening effect of micropiles was confirmed both by testing and numerical simulation.

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Structures and facilities can be characterized as an asset to produce benefit. Therefore, the asset pricing of facilities will be evaluated with an income capitalization model. If a seismic risk is quantitatively represented as financial loss, the seismic risk is taken in the income capitalization model as a part of loss in weight of the asset pricing. Further, from a point of view of an investment, the effect to reduce risk due to earthquake disaster prevention will be analyzed by applying the income capitalization model. This study will propose a methodology for decision making of earthquake disaster prevention that is represented by seismic reinforcement or earthquake insurance, and the validity of the proposed method is demonstrated through the numerical example.

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The purpose of this study is to investigate the relation between the damping model used in the horizontally laminated ground model and the accuracy in identification of the parameters using vertical array records of ground motions. The stiffness and damping parameters are generally identified in this type of problem, supposing onedimentional multiple reflection of shear wave. As to the stiffness, the shear wave velocity of each layer is identified. On the other hand, as to the damping, several models have been proposed, moreover some researchers identified uniform parameters through the layers and others identified the parameters of each layer. In this paper, it is demonstrated how the difference of damping model and conditions of analysis influence on the accuracy of identification of damping parameters.

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