In this study, estimation method of seismic damage of railway embankment was proposed, complying with the current seismic design. The proposed method requires fundamental features of embankment, such as gradient or height, as well as magnitude, hypocentral distance and peak ground acceleration of the target earthquake. Given these parameters, the sliding deformation of embankment is estimated. Since the method requires only geometry of embankment, proposed method is also applicable for existing embankment, the design of which might not comply with the current design standard. The efficacy of the proposed method is confirmed by comparing the estimated damages with those observed in the 1995 Hyogo-ken Nanbu earthquake.

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 Lateral bracings of deck type steel arch bridges have large axial force under seismic force for transverse direction, and its damage leads to reducing whole strength of bridges. Therefore, required lateral bracing extensional rigidities were studied so that lateral bracings might not be weak points. The study had two approaches, one was "out-of-plane buckling approach" that was invented from out-of-plane buckling of arch ribs under vertical force, the other was "yield strength approach" that was invented from yield strength of arch ribs. For each approaches, simple formulas that compute required lateral bracing extensional rigidities and sectional force for design were proposed. In addition, a simple formula that computed required gusset plate thickness of lateral bracings was proposed. Finally, a trial design is conducted to check formulas, and the design flow is proposed.

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 In this paper, two kinds of lateral walking design forces per person are proposed and compared with the Imperial College test results, etc. Numerical simulations considering these walking design forces which are incorporated into the neural-oscillator proposed by Matsuoka are carried out placing much emphasis on the synchronization (the lock-in phenomenon) for a existing pedestrian suspension bridge with the center span of 62.4 m. As compared with full scale measurements for this suspension bridge, it is confirmed that the analytical method based on the neural-oscillator model might be one of the useful ways to explain the synchronization (the lock-in phenomenon) of pedestrians being on the bridge in case that oscillator frequency is less than or equal to the natural frequency of the bridge.

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 Weathering steel were steel with high atmospheric corrosion resistance by alloying Cu, Ni, etc. Use of weathering steels was limited by environmental conditions especially for airborne salts. Thus, new weathering steels with higher corrosion resistance in more salty condition were developed by adjusting composed elements. However, increasing alloying element will increase its cost. Thus, selecting weathering steels fit for construction sites is important. This study is aiming to understanding relationships among corrosive resistance, composite effects of weathering steels and local environments in order to select the best weathering steel. For this purpose, exposure tests of several weathering steels were conducted under various environmental conditions. Following findings were obtained: (1) The corrosion rate parameter A_s could be proportional to the weathering alloy index V and the regional corrosivity index Z. (2) Another corrosion rate parameter B_s could be proportional to log(Z), had almost no relation with V. (3) Specimens with a butt weld joint do not have any significant deterioration but, the existence of weldment increased A_s about 20%. And, (4) Rainfall effects could be explained as modification factor for A_s and the factor related with index Z. Based on these facts, the index V can be used to select adequate weathering steel if design period, allowable thickness reduction and index Z were given.

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 The main reason of deterioration in a steel girder is corrosion. Because the characteristic of Carbon Fiber Reinforced Polymer (CFRP) is light weight, high strength and high durability, CFRP has been paid to attentions for repairing or reinforcing the steel bridge. Although many studies on the application of CFRP to the steel bridge have been reported so far, previous studies mainly focus on axial or bending members. However, most of the corrosion in the steel bridge is found on webs near the end of the girder. There has been few investigated on repairing or reinforcing the web using CFRP. Therefore, shear buckling test for steel girder bonded CFRP sheets on the web is carried out in this study. In the test, CFRP sheets are bonded on the web through low elastic putty layer in order to improve the ductility for out-of-plane large deformation under shear. Furthermore, an evaluation method of its ultimate strength is proposed by modifying the Basler's equation.

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 As seismic retrofit method against a Level-2 ground motion for an existing sway bracing and lower lateral bracing of upper-deck type steel arch bridge, an efficient retrofitting method by energy absorption had been proposed to prevent these buckling. In this study, these performance confirmation experiments and FEM analyses were conducted. As a result, a global buckling of the member was restrained by proposed retrofitting method of ductility improvement type, and it was satisfied with the deformability of the required performance on the design. It became clear that an energy absorption by axial strain can be expected beyond yield strain from the early stage over the whole axial member. Also, the experimental result was reproduced by the FEM analysis considered with the contact phenomenon between the existing steel bracing and the steel restraint member.

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 The JMA scale of seismic intensity has ten degrees by using the instrumental seismic intensity. The filtered acceleration amplitude, a₀, used for the instrumental seismic intensity is a value that the accumulated time for acceleration larger than a₀ is 0.3 second in the time history of acceleration. The effect of the acceleration in the remaining time history is not considered. The time history expression of seismic intensity using the running r.m.s. method will be discussed and compared with the instrumental seismic intensity in the paper. A modified seismic intensity is proposed by using a parameter which shows an extent of the seismic intensity with time.

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 This paper presents results of an investigation of evaluating the bridges health index for maintaining more effectively by using general statistical analysis of bridge inspection data. In this study, the first principle component of principle component analysis using a lot of inspection item results on each member is defined as bridge health index (BHI). The special feature in BHI is to be continuous quantify in order not to lose the amount of information contain in the discrete many inspection results. In addition, the bridges seem to be stratified into 4 categories considering deterioration mechanisms using the information obtained from second principle component. For this reason, the result in this study showed to be the effective information for repair and maintenance plan of bridges.

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 While distributed strain sensor has been advanced by the use of stimulated Brillouin scattering in optical fiber, fiber optic sensor has recently increased its application in civil engineering field. In this study, fiber optic sensor installation technique is developed, and it is experimentally proven that the sensor can contribute to strain monitoring for asphalt layer, which has a difficulty in embedding sensor because of its temperature-dependent behavior. Due to the softening of asphalt, the fact that the transferred stress from asphalt to sensor is drastically decreased over the transition temperature leads to low sensor sensitivity. To obtain both durability and sensitivity in asphalt over a wide range of temperature, several types of fiber optic sensor coated with resin materials are designed, fabricated, and evaluated for its basic performance. Through experiments on both prism specimens and a full-scale pavement with the developed sensor coated with polyester and polyethylene of 5 millimeters in total diameter, it can be stated that the sensor directly monitors asphalt behavior even if the temperature has been changed. Moreover, post-processing technique for measured strain distribution data is proposed toward global integrity monitoring.

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 Three-dimensional dynamic cracking propagation analysis was conducted to evaluate seismic safety of concrete gravity dams, since seismic response of the dams were strongly affected not only riverbed rock but also abutment of base rock. Analytical models were constituted by reservoir, base rock and dam body using smeared crack model. Crack pattern, crack propagation and failure pattern of dam body were discussed comparing those obtained from two-dimensional analysis. It was realized that the results for crack pattern and propagation based on three-dimensional analysis would be more acceptable than those based on two-dimensional analysis. Moreover, residual ligament height defined from crack propagation was newly introduced for index of earthquake-resistant safety concerning utilization of reservoir. The relationship between residual ligament height and input acceleration was investigated to evaluate seismic safety of concrete gravity dams.

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 Recently, serious fatigue cracks have been reported increasingly at rib-to-deck weld in orthotropic steel decks on severe traffic highway routes. As an effective countermeasure for these fatigue cracks, steel-fiber reinforced concrete (SFRC) overlay is being gradually used, while crack tips are removed for local stress reduction in the shape of cut-out details. Static/fatigue loading tests and FE analyses were conducted for a full scale existing steel deck specimen overlaid by SFRC in order to investigate fatigue behavior around cut-out details by changing length and location of cracks through rib-to-weld. In this paper, these results are presented and retrofit effect by SFRC overlay is discussed.

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 When a train runs on a bridge, the natural frequency of the bridge decreases apparently due to the effect of the mass of the train. However, there have been no researches that discussed this effect based on actual measurement data. In this study, the authors formulate a TV-VAR model in which the VAR coefficient of a vector autoregression model changes with time stochastically, in order to evaluate the decline in the apparent natural frequency of a bridge at the time of train passing, and then develop an estimation method for unknown parameters based on the hierarchical Bayesian method. By applying numerical calculation results and the actual acceleration response of the bridge at the time of train passing, it was found that (1) the proposed method can evaluate the change in natural frequency accurately, (2) apparent natural frequency decreases actually in the bridge at the time of train passing, and (3) the decrease amount is 14% on average, 20% at a maximum for the target bridge of this study.

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 In this paper, in order to reduce the ground vibration caused by Shinkansen running, we executed some measures as a part of the maintenance of the railway track in the tunnel, and verified the effect. First of all, lower stiffness rail pad was adopted replacing the current one to soften the track stiffness in vertical direction. As a result of the measurement, the vibration of 50Hz band reduced in the tunnel. On the other hand, the vibration corresponding to the wavelength of 2.5m was prevailing. Then, by evaluating the rail surface irregularity by using axle-box acceleration, we found that the irregularity of it wavelength is large for a part of rail. Next, in order to reduce the excitation load acting on the track caused by the irregularity, these rails were ground or replaced. As a result of the measurement afterwards, the vibration of 12.5Hz band reduced in the tunnel. Finally, it was confirmed that by these measures the ground vibration in the residential quarter on the upper part of the tunnel decreased by 6 dB on the average.

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 Many kinds of steel are widely used in steel bridge structures. This report summarized the welding procedure tests carried out in 2003-2010. In these welding tests, four kinds of steel were employed to fabricate welded joint specimens, which were SM490Y, SMA490W, SM570Q and SMA570W. In this report, the results of tensile strength and Charpy absorbed energy were shown. Tensile strength exceeded to the nominal base metal strength for all tensile coupon specimens. Charpy absorbed energy of HAZ (heat affect zone) also exceeded to 200J on an average in many type of steel. However, there were a few cases that an average of Charpy absorbed energy of Depo (weld metal) is beyond 100J, regardless of welding wire and welding method. It has been shown that the mechanical properties, such as tensile strength and Charpy absorbed energy, of welding materials does not exceed to that of steel material.

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 Practically, it is very important to clarify the magnitude of stress and deflection of the beam subjected to an impact force. Although, many studies have been made from old, no practically useful equation has been ever found yet. There upon, loading experiments were carried out to investigate the dynamic behavior of the model beam with three sizes of span and height in the way of hitting the loading rod at the tip of which a rubber material is put on, by the knocking rod. It was revealed that the apparent static loads to produce equivalent deflections by the dynamic test are proportioned to -1 power of the span of the beam. It was also revealed the deflections are proportional power 2 of the span, and power -0.6 of the equivalent spring constants of the beam. According to the results of this study, it is possible to estimate the dynamic behavior of beams of different sizes of span and height through the test for two species of beams.

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 A rheology originally proposed for high damping rubber bearing (HDRB) is applied to natural rubber bearing (RB) and lead rubber bearing (LRB) along with its simplified form. Comparing HDRB, the elastic-plastic equilibrium responses were found to be more dominant than the rate-dependent response due to viscosity for RB and LRB. Moreover, the overstress in loading/unloading was found to be analogous. The dependency of nonlinear viscosity on current strain was found to be weak in contrast to the existence of considerable nonlinearity in elastic response. The original rheology model considers the nonlinear elasto-plastic and viscosity induced rate-dependent behavior into account, while the viscosity effect is eliminated in the simplified version. The models are implemented in a finite element code. The modeling effects of bearings on the seismic responses of a multi-span continuous highway bridge are investigated via nonlinear dynamic analyses for two strong earthquake ground motions. Three analytical models of isolation bearings are considered for comparison: the conventional design models and the proposed two models. Model parameters for the bearings were determined for two temperature conditions: the room temperature (+23°C) and the low temperature (20°C) based on experimental data. The implication of the rheology models for response prediction of a prototype bridge is studied by comparing the rotation of a plastic hinge in pier and shear strain at the top of the bearing. The comparison suggests that the modeling of RB and LRB considering rheology properties is important for rational prediction of the seismic response of highway bridges, particularly at low temperature condition.

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 This work deals with influence of bi-directional cyclic displacement loading on the ductility of hollow circular steel columns and to develop a seismic verification method for bridge piers, with pipe sections, when subjected to coupling action of two horizontal earthquake components. For this purpose, nonlinear numerical analyses are performed on Finite Element models by setting radius-thickness ratio and slenderness ratio as main design parameters. The strain-based ductility formulas are developed separately for uni- and bi-directional cyclic loadings, and based on these formulas a seismic verification method is proposed. To confirm this method, nonlinear dynamic analyses are carried out on three different beam element models of bridge piers. The deformation and strain performances are evaluated by displacement-based and strain-based methods. The comparative study shows that the strain-based seismic verification method is critical than displacement-based method. Further, comparison between allowable values given by past ultimate strain formula indicates that the formulas developed in the present study are more adequate for use in seismic verification of circular steel bridge piers when subjected to two directional earthquake components at the same time.

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 Given the different geology and earthquake activity, establishing a regional attenuation relationship is deemed important for the seismic design of structures. This paper presents a new equation in place of the relationship currently used in Vietnam for horizontal ground motion based on database sets compiled from strike-slip and shallow crustal earthquakes with magnitudes ranging from 3.0 ≤ M_w ≤ 6.9 and source distances of up to 300 km for northern Vietnam. This new equation estimates the ground motion in terms of moment magnitude, distance and site conditions for strike-slip earthquakes. The equation is derived based on a regression analysis of earthquake records; in this study, the database consists of earthquake records from Japan, Vietnam and adjacent areas. We also assume a few simple relationships, such as the relation-ship between M_w and M_s, the closest distance to the fault and the effects of shallow site conditions on the average shear-wave velocity in the upper 30 m to develop a comparison with existing relationships. The new equation for northern Vietnam corresponds better with other equations for near- and far-field distances than the equations currently used for seismic design in Vietnam.

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