In the p--Ritz method using a power function for the basis functions, effect of round-off errors in the erasing operation is increased because condition number of the stiffness matrix is large. The purpose of this study is to improve the trial function of p--Ritz method in order to apply this method to the bending analysis of plates. Orthogonal polynomials, such as the Legendre polynomial or Chebyshev polynomials of first kind is used for the basis functions. Furthermore, in selecting the displacement field, all terms of the expansion terms up to given number are used without omitting the higher order terms. The improved p--Ritz method is applied to the bending and free vibration analysis of plates based on the first order shear deformation theory, the accuracy and applicability of this method is investigated.

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Rikuzentakata City suffered great loss due to the tsunami caused by the Great East Japan Earthquake and it was found that many video or photo materials could be used for the observation of tsunami process in this area. Therefore, both the video analysis and the numerical analysis based on the non-linear long wave theory were conducted to describe and simulate the tsunami process. Besides, in the numerical analysis, the height of coastal dike model was set as the parameter to study the prevention effect of coastal dike on tsunami process. As a result, the outflow mechanism of Kesen Bridge in Rikuzentakata City was explained and the prevention effect of coastal dike on tsunami process was investigated.

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It is well-known that a scissors structure is one of the major deployable structures, and its quick folding and expansion actions are so useful for a temporary structure. We have suggested ``Mobile Bridge'' which is applied this scissors structure to a bridge form of an emergency bridge. The rapid expansion/folding action of Mobile Bridge enables %to is useful for the scissors-type emergency bridge the saving of the transit and construction time at the disaster sites. To that end, reducing the dead weight is important because mobility or performance depends on its own weight. In this paper, we evaluated the 6N01 aluminum alloys with three - hollow section experimentally and carried out the design calculation of Mobile Bridge by using the experimental results. As the results of the design examples, we revealed the correlation among the expansion angle, length of the structural member and the number of scissors unit, and obtained the basic data for design of Mobile Bridge.

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This paper describes the discussions on the ultimate strength characteristics for existing compression members of steel truss and arch bridges, and proposes new ultimate strength curve of welded box-section members. The investigation objects are section size, material, initial imperfections, stiffener size of compression member which designed based on Spec. for Highway Bridges 2002. In addition, ultimate strength characteristics of existing compression members with box-section are calculated for several steel types. The results of investigations shows that the 0.2σ_y is able to apply as upper limit of compression residual stress (σ_rc) for HTSS members. The results of numerical analyses provide the ultimate strength characteristics of welded box-section compression members for steel truss and arch bridges. Moreover, new ultimate strength curve is proposed for the compression members in this research.

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The stainless steel structures have high corrosion resistance and elongation than the carbon mild steel structures. The purpose of this paper is to clarify the compressive strength behavior and the estimation method of the ultimate compressive strength for simply supported stainless steel plates under in-plane quasi-statically uniaxial loading. Firstly, the ultimate compressive behavior of simply supported stainless steel plates under in-plane quasi-statically uniaxial loading investigated to use the numerical analysis. Secondly, these analytical resultants were examined using the strength estimation method. Finally, this paper proposed the ultimate compressive strength curve of three region for simply supported plate under in-plane quasi-statically uniaxial loading.

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In a designing of the most of Portal Rigid-frame Bridges (PRB), the earth pressure by the backfill soil for abutment is taken into account as one of design advantages. Accordingly, the soil in the backfill has to be hold in a good condition to show a proper pressure. However, generally, the soil is under an undesirable state due to the water penetration by rain water mainly and also there are few study results regarding these problems. The survey and analysis for the drainage method in Japan, USA and European countries are carried out and a desirable method is proposed in this paper. The usefulness of proposed method is confirmed by two dimensional water penetration analysis using the software PLAXIS.

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Because of various conditional inspection data, some procedures have been reported for calculating the Markov transition probability for deterioration prediction. In this paper, it is tried to verify the property of those calculation procedures based on the given data in simple Markov process. In this paper, 3 proposed procedures are verified. Based on enough amount of data, those 3 procedures give almost equal transition probabilities. But, in the case that the numbers of data of each deterioration level have deviations, those 3 procedures give the transition probabilities which have differences not to be disregarded.

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Reinforced concrete (RC) structures in a marine environment deteriorate with time due to chloride-induced corrosion of reinforcing bars. This paper presents reliability-based durability assessment of existing RC structure in a marine environment. A simple assessment criterion with partial factors that satisfy the target reliability level within the remaining life-time of existing RC structure is presented. A procedure to obtain the partial factors updated by the Sequential Monte Carlo Simulation is indicated. In this procedure, the chloride concentration distribution by coring test is used as observational data. Partial factors could be determined by taking into consideration the reduction of uncertainties associated with the prediction of chloride-induced corrosion. Partial factors for durability assessment of existing RC structures could be reduced compared with those for durability design of new RC structures.

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This is a report on long-term remote monitoring for ascertaining the occurrences of wind-induced vibration in a steel truss bridge. A large crack was found at the bottom of a diagonal member above the middle pier of a long span steel truss bridge. From the findings of investigation, it has been concluded that a fatigue crack appeared firstly and it caused brittle fracture. Hence the principal factor of the fatigue fracture is inferred wind-induced vibration of the member. We had conducted a long-term monitoring to understand wind conditions around the member and to ascertain the occurrences of wind-induced vibration.

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Chloride due to de-icing salt induced the corrosion of the guardrail post on the highway along the seashore of Hokuriku district. This study proposed the non-destructive method to estimate the structural integrity using the vibration mode obtained by the vibration test. Test guardrail posts which modeled the corrosion were produced. The vibration characteristics of those posts due to the impact and the resonance examination were observed. Also the stiffness and load carrying performance of those posts were investigated using FEM analysis. As the results of the examination and analysis, this study targeted the high-order vibration mode shapes to estimate the corrosion damage of the guardrail post at the basement. Moreover, the structural integrity of those posts was estimated using the relation of the MAC (Modal Assurance Criterion) and the ratio of the bending stiffness.

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A damage identification method for a structural health monitoring of concrete structures based on the anti-resonance frequency was investigated. The static loading tests of the two RC beam specimens were conducted to measure the resonance and anti-resonance frequency changes by the flexural cracks. The forced vibration tests by using a white noise wave were carried out when the vertical loads were subjected at the 1/2 or 1/4 of the span, respectively. As the experimental results, the distribution of the anti-resonance frequency of the beam specimen was changed to asymmetric when the vertical load was subjected at the 1/4 of the span. It was indicated that the damage location of a concrete beam could be identified based on the anti-resonance frequency change.

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The objective of this paper is to evaluate the dynamic response and distortion-stress in curved multi-girder bridges for transverse vehicle position, curvature and skew angle. To perform the numerical investigation, a three-dimensional bridge-vehicle-interaction approach consists of spaced bridge-vehicle structure and contact model is proposed using commercial ANSYS code. Inertia and horizontal force, deck friction and road roughness are taken into account in the analysis. Highly reverse distortion-stress is found on exterior girder for transverse vehicle positions. The curvature and skew angle has a significant effect on differential deflection, distortion-stress and bearing force which depend on vehicle position. Distortion-stress and differential deflection do not show proportionality and current existing practice fails to predict the distortion-stress accurately in curved bridges.

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This study is intended to propose RC vibration isolation unit as a new vibration reduction method to mitigate the ground vibration around Shinkansen viaducts induced by running high-speed trains in both vertical and lateral directions. The RC vibration isolation units can work as the vibration source isolation, propagation path obstruction or vibration receiver isolation to reduce the train-induced ground vibration by interception, absorption, scattering and diffraction of the vibration waves. Their vibration characteristics and vibration screening efficiencies are investigated by a developed 3D numerical approach with taking into account the train-bridge interaction and the soil-structure interaction. The results indicate that the RC vibration isolation units are very effective to reduce the train-induced ground vibration.

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In this study, we conduct fundamental study of structural health monitoring based on changes of modal amplitude. The free damped vibration of a pedestrian bridge is measured by using 3D wireless acceleration sensors. The pedestrian bridge has local damage on its girder. The vibration measurement is repeated after the repair work of the girder. From measurement results, natural frequencies of each mode don't change by repair work. Modal amplitudes are changed in several vibration modes. COMAC method is applied to discuss the effect of modal amplitude changes and the change of COMAC is larger on the nearest point of the damage.

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The purpose of this study is to investigate the vertical vibration of pedestrian bridge induced by higher components of human walking vertical force. From the experiment results on human walking the author has already examined, it is found that not only in-phase component with frequency of 2f_w, 3f_w, but also in-opposite-phase component with frequency of 0.5f_w, 1.5f_w, 2.5f_w where fw is the walking rate is observed. A full sacle measurement for the pedestrian bridge with center span length of 33m is carried out paying attention to the resonance phenomenon due to higher components of human walking vertical force. Dynamic response characteristics due to these vertical higher components of human walking are revealed from the dynamic design viewpoint of pedestrian bridge.

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In this study, hybrid experiment system with centrifuge, which was developed for soil-foundation-structure interaction, is discussed by focusing on its problem and validity. This experimental system often underestimates the response of foundation. From experiment and numerical analysis, it revealed that this underestimate is caused by influence of soil deformation. Applicability of this hybrid experiment system is also discussed for soil-foundation-nonlinear structure system. The experiment is conducted by using detailed numerical model to describe nonlinearity of superstructure.

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Serious damage occurred at Inohana Viaduct site along the Tohoku Shinkansen, Hanamaki City, during the 2003 Southern Sanriku Earthquake (M_J7.1). On the other hand, during the same eathquake, the nearby Nakasone Viaduct in Kitakami City did not suffer significant damage. In order to reveal the cause of of different performance of these structures, it is important to evaluate strong ground motions at the both viaduct sites. In this study, seismic waveforms at the viaduct sites were estimated based on the aftershock records at the viaduct sites and the main shock records at the nearby strong motion stations. In addition, the accuracy of the estimation methods with and without the aftershock records was discussed.

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Quick state judgement of important infrastructures such as bridges is required after earthquakes. We focused on accelerometers which are easy to be installed and already installed on many infrastructures. We tried to detect the damage of structures by applying singularity analysis based on Multi-fractal analysis to the acceleration data which are measured on RC column at large shaking table tests. Some singularity points of acceleration responses were detected by wavelet transform when the damages judged from their strain data and video record occured. However, their wavelet spectrum reaction was not clear. Therefore, we computed dominant Lipschitz-Hölder exponent of the acceleration waveform from singularity spectrum which can quantitatively evaluate singularity, and it was shown that the moments of some damage occurrences were detected form the dominant Lipschitz-Hölder exponents.

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This study is aimed at evaluating the post-earthquake seismic performance of steel frame-typed bridge piers and a steel arch bridge, installed with three types of seismic dampers, namely SMA (Shape Memory Alloy) damper, BRB (Buckling-Restrained Brace) and SPD (Shear-Panel Damper). Seismic dampers are designed to insure that the maximum response strain of the main structure is less than two times of the yield strain, and then the post-earthquake performance of main structure is evaluated by residual displacement.

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Following the previous investigation, this paper presents a further study on developing a high-performance prototype seismic damper, named Buckling Restrained Rippled Plate (BRRP) damper. BRRPs are to be installed at the edges of a girder-type bridge, acting as energy dissipating seismic dampers for Level 2 earthquakes. In order to develop a prototype damper, the thickness of BRRP's core plate is increased to 25mm from the previous thickness (9mm). The target performance of BRRPs is set as 1) the load carrying capacity is over 400kN, 2) the deformation capacity is over 40mm and 3) the local strains are smaller than four to five percent. Cyclic loading and pseudo-dynamic tests have shown that the tested BRRPs perform well and fulfill the above performance requirements.

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Many bridge girders were washed away by the tsunami due to the Great East Japan Earthquake and the design method of tsunami force affecting bridge girder has not been proposed. The authors conducted the steady flow experiment to simulate the tsunami flow and studied the characteristics of the wave horizontal force and vertical force affecting the girder model. It was obtained that the wave horizontal force was proportional to the square of flow velocity and the evaluation formula of horizontal force was proposed. The downward force was found affecting the model in the steady flow ignoring the rise speed of water level but the maximum uplift force, which was about 38% of buoyancy force applying on the model in static water condition, was found affecting the model if the rise speed of water level of steady flow was simulated by 90 cm/min (prototype: 6.4 m/min).

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In this research, by using the long water channel, the authors created solitary wave and analyzed the wave force applying on abutment-girder model (both girder and abutment are made as model). As a result, it is found that the horizontal force on abutment can be evaluated by the wave pressures on the front surface area of abutment. Besides, it is also noted that the wave pressures on the front surface area of abutment is about half of that on vertical wall structure, because the solitary wave could pass through the abutment-girder model between the two abutments, which led to the rise of wave height at the front surface of abutment became smaller compared with that at the front surface of vertical wall structure.

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In order to find out the mechanism of tsunami soliton on bridge girder, the soliton experiment was carried out with a bridge girder model. As a result, the measured maximum horizontal force on bridge girder by force transducer was found close to the calculated maximum force by the integration from the wave pressures on girder side area and the maximum forces happened at the same time. Thus, it is concluded that the horizontal force is dominant to the wave pressure on girder side area. Besides, from the parametric study of wave height, it is noted that both horizontal force and wave velocity are proportional to wave height. Thus, it is concluded that bore wave horizontal force has a high correlation with wave height.

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This paper studies the effects of uplift in spread foundations and yielding of underlying soils on sectional force induced in bridge piers subjected to pulse-like ground motions using a macro-element model developed by PWRI. Sinusoidal pulse, which simulated pulse-like ground motions, was used. As a result, it was found that degree of stress reduction effects vary depending on pulse period characteristics as well as peak acceleration of pulse-like ground motions.

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It was observed that some RC bridge columns with low longitudinal reinforcement ratio were damaged during the 2011 Great East Japan Earthquake. The seismic performance of RC bridge pier wall with low longitudinal reinforcement ratio is still not fully understood although few experimental works were conducted previously. In this research, the failure mechanism of RC bridge pier wall was clarified based on the cyclic loading tests for scaled-model pier walls and the effect of reinforced concrete jacketing for the seismic retrofit was also examined. The test results showed that the ductility of RC bridge pier wall with low longitudinal reinforcement ratio was not improved by reinforced concrete jacketing for strengthening without anchoring the additional longitudinal steel bars into the footing.

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It has been well recognized that response displacement of structures has good agreement with damage due to ground motions. However, there are large uncertainties in estimating the peak nonlinear response displacement of structures by typical seismic intensity measures. A seismic intensity measure considering the maximum seismic energy during the half of natural period of the structure was proposed and its application to the response of reinforced concrete bridge columns was shown in this paper. It was shown that the proposed intensity measure has better agreement with the peak nonlinear response displacement of reinforced concrete columns as compared with PGA, PGV, response acceleration at the fundamental natural period and SI.

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It is often difficult to conduct seismic retrofitting of all columns in railway RC viaducts by restriction of construction. In such a case, it is necessary to conduct verification of seismic performance taking no retrofitting columns of shear failure mode into consideration. However there are few studies on evaluation method of seismic performance for RC viaducts with columns of shear failure mode. In this study, evaluation method of seismic performance was proposed for such a viaduct.

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Since HYOGOKEN-NANBU Earthquake in 1995, a large number of researches on the seismic performance of steel bridge pier have been carried out. However, there is very few research for the repair method of the steel bridge pier that has been damaged in earthquake. In this study, the repairing effect of filling concrete for circular steel bridge piers which have different diameter-to-thickness ratio is to be verified. Static cyclic loading tests until reaching their predetermined damage levels were conducted. After filling the concrete inside the specimens, the same static cyclic loading tests were carried out to clarify the seismic performance of repaired piers. Then, the seismic performance has been evaluated by the strain value during cyclic loading. Finally, the suitable repair method have been suggested.

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In order to investigate the effect of environmental degradation factors (ozone and temperature) and strain on crack initiation of base-isolated natural rubber bearing for bridges, a series of accelerated ozone exposure experiment with different temperature were carried out. It was confirmed that the high temperature condition was severer than the low temperature one for ozone crack initiation of natural rubber. The crack was initiated around the region, in which the tensile strain was generated due to shear deformation of rubber bearing, under the high ozone density (150pphm) and the high temperature (40°C) condition. The mechanical performances of rubber bearing with cracks were not deteriorated because these cracks initiated in the surface rubber did not reach the inside rubber layers.

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The specifications for highway bridges require cushioning material to be installed on bridge restrainers to reduce seismic impact force; although no clear standard design method of cushioning material is provided in the current specification. Thus, it seems to have a potential for making the design of bridge restrainers more appropriate if the evaluation of cushioning effect could be more quantitatively. Therefore, weight-drop tests were conducted on cushioning rubber pieces to get fundamental data on cushioning characteristics. In this test, it was focused on rubber pieces' shape, hardness and confining conditions. It was obtained that cushioning characteristics would be significantly affected by the rubber pieces' shape and confining conditions.

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This paper is intended to evaluate the effectiveness of shock absorber devices installed between roller bearing and stopper on reducing viaduct damages. In particular, the effect of shock absorber device's stiffness on mitigating viaduct damage is focused on in this analysis. For such purpose, the viaduct seismic performance is evaluated considering four different stiffnesses of the shock absorber device combined with a kind of viscous damper, which leads to five cases including the case without shock absorber device. Deck unseating damage, pounding forces between roller bearing and stopper, pier damage, displacement of superstructures and bending moment-curvature relationship are evaluated in this paper. Based on the numerical results, the application of shock absorber devices on viaduct, especially with large stiffness, can significantly reduce the seismic damages of the curved viaduct during great earthquakes.

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This study introduces a dynamic bearing property definition method to evaluate the seismic performance of a base isolated bridge under severe cold environment. Low temperature effect of base isolation devices due to their material characteristics is particularly considered. Thermal production which results in temperature variation is also taken into account to ensure the accuracy and practicality of analysis results. For this purpose, the overall three-dimensional non-linear bridge dynamic response is examined in detail under long duration earthquake ground motions.

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During the last decades, the need for safer bridges has led to high level aseismatic design of bridges including the use of base isolation bearings. This study numerically evaluates the effectiveness of a promising base isolation bearing, the Friction Pendulum System (FPS), used to improve the seismic performance of highway bridges under strong earthquakes. Nonlinear dynamic analysis and parametric studies are conducted with three-dimensional viaduct models subjected to near-fault earthquakes. The results show that FPS supports can effectively reduce the seismic response at the piers of both straight and curved viaducts. However, curved viaducts subjected to extreme earthquakes may suffer from damage at the expansion joint. In such cases, the seismic performance can be improved by installing unseating prevention cable restrainers as well as changing the bearing arrangement of FPS.

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The basic aerodynamic force characteristics of a photovoltaic panel installed near the ground were studied in two types of shear flow. The aerodynamic force coefficients of a two-dimensional flat plate model were measured in a wind tunnel with varied height and angle of attack. The difference of the shear flow could approximately be considered by taking the reference wind speed at the height of the model center. The ground effects tendency generally changed in the order of smooth flow, less sheared flow and more sheared flow. Lift-to-drag ratio of the panel model was almost constant regardless of the model height when the angle of attack was equal or larger than 10 degrees.

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Many bridge girders were washed away by tsunami caused by the Great East Japan Earthquake 2011. Recently, the localized heavy rain causes some flood damages. Some bridge girders were washed away by flood same as tsunami. The hydraulic experiments and simulations were carried out on the assumption that water flow forces caused by tsunami and flood can be estimated as steady water flow forces of drag and lift. We focused on the drag force, and we studied about four types of steady water flows acting on a bridge girder.

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Aerodynamic stability of long-span cable-stayed bridge deck is a crucial issue. The bridge deck aerodynamics should be well understood for efficient design of a stable bridge system. In this work numerical simulation is conducted for a pentagonal shaped bridge deck to explore its aerodynamic features numerically. Analytical results are compared with previous experimental work to assess the capability of two-dimensional unsteady RANS simulation to predict the aerodynamic features for this type of deck. It is also tried to clarify the influence of carb location and height on the aerodynamic behavior of the deck. Further goal of this study is to investigate the Reynolds number influence on flow field of the bridge deck.

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In this paper we develop a theoretical model for calculating the steady inviscid flow subjected to solar radiation at the collector of a solar updraft power plant. The result was a set of nonlinear equation describing the transformation of the solar radiation into heat-flux of the collector airflow. Iterative scheme was employed in order to solve the equation for mass flow rate and temperatures, for which computer codes were developed. A comparison of simulation results with the Manzanares prototype experimental data was performed; demonstrating good agreement between the two. Computed power for selected locations in Japan was also demonstrated for potential application of a solar updraft power plant.

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Although fatigue assessment was required for highway bridge design since 2002, expansion joints and sign structures were so far not designed for fatigue. One reason was that the fatigue design loads were not well defined. Since quite a few fatigue failures occurred in such structures, fatigue durability assessment seemed essential. In this paper, simple fatigue design loads and their number of cycles are defined for durability evaluation for expansion joints and sign structures. Stress ranges needed for fatigue durability evaluation can be obtained from static design chart, since the fatigue design loads are somehow related to static design loads. Examples of fatigue durability evaluation are described in this paper.

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This study investigated a steel patch plate bonding technique on one side for the temporary repair of through-thickness crack in orthotropic steel deck, OSD, at vertical stiffener end. Out-of-plane gusset specimen was used in this study. Fatigue tests were carried out using bending type of fatigue test machine under the stress ratio R=-infinity. Steel plate or Cabon Strand Sheets were adhered on the back surface of specimen after through-thickness crack was found. Then bending fatigue test was continued until crack propagated 50mm away from the weld toe on gusset attached surface. By bonding patch plate on the back surface of the specimen, the remaining fatigue life was extremely extended if the patch plate working. Furthermore, when the impact crack closure retrofit, ICR, treatment was applied at the crack on gusset surface with pach plate bonding on the back surface, the remaining fatigue life was also extended.

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The collapse mechanism has been investigated by using FE analysis. The simulation results showed the similar failure mode to the actual bridge collapse by modeling the corrosion damage correctly. The loss of post-buckling strength by both the rupture of web-lower flange connection and web-vertical stiffener connection at the end span was thought to be the cause of collapse. On the other hand, the section loss of horizontal and vertical stiffeners, and the rupture of lower flange did not contribute significantly. According to the analysis results, the collapse might be avoided by repairing the rupture of web-vertical stiffener connection, since the recovery of shear capacity should be expected by the formation of diagonal tension field and the frame effect.

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Weathering steel is generating precise rust on the surface, and has the character which controls progress of corrosion. However, protection rust may not generate depending on the placed environment. Therefore, the weathering steel bridge needs to perform check after construction, and needs to evaluate the state of rust. The basic method is to evaluate in five steps from rust appearance of the particle diameters. This is a standard evaluation method used for a long time, but even an expert may hesitate about a judgment because it is not necessarily given a standard quantitative enough. In order to improve these problems, we propose the appearance evaluation method using the image analysis in this study.

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In this study, on-site loading test and short-term monitoring using more than a hundred sensors were carried out for an existing long-span bridge, which has been managed by a local government, with the aim of evaluating its present load-carrying capacity and performance toward planning future maintenance strategy. The bridge studied is Gerber (cantilever) steel through truss bridges that were completed and opened to the traffic in 1937. As a result, the performance of Gerber hinges were evaluated, then information on priority for repair was obtained.

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Urban highway networks typically rely on a large number of aged viaducts needing an efficient and effective maintenance. Though their numerical models exist, the level of accuracy has not been clear in terms of secondary member stress analysis and fatigue life predication. In this paper, dynamic stress response of a steel girder bridge subjected to vehicles is investigated, using field measurements and numerical simulations. The objective of this research is to investigate the capability of a FE model in predicting stress responses in local members and extend to study fatige life. Comparisons between the measurement and the simulation results from modified models were conducted. Furthermore, the local stress responses in the simulation are sensitive to vehicle speed and pavement condition. The calibrated model reproduces the measurement with the accuracy of about 10% and indicates that the pavement condition indeed affects the fatigue life of secondary member.

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This paper presents a study on seismic behavior of steel piled jetty repaired by steel patch plates, and shows a study concerned with a required thickness of steel patch plate. In this study, the whole FE model is used to study the seismic behavior of a piled jetty. Furthermore, the cantilever FE model is examined to propose a required thickness of steel patch plate. From the time history response analysis, it is shown that seismic behavior of the steel piled jetty repaired by steel patch plates becomes almost the same as behavior of the intact piled jetty. Based on pushover analyses of a number of cantilever FE models, an empirical formula to determine the required thickness of patch plate is proposed for the repair design of corroded steel pile.

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The fatigue damages have been appeared both the rib plates and vertical stiffeners near the floor frame support on the non-composite stiffening trusses suspension bridge after around 30 years of service. In order to investigate the cause of fatigue damages and to propose the repair methods, both the field measurement and FE analysis have been performed. As the results, the cause of the fatigue damages is that the sliding function of the line bearings is disappeared due to corrosion, and the deteriorated line bearings should be replaced to new ones.

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Ministry of Land, Infrastructure, Transport and Tourism has encouraged proposing the Plan for life-prolongation of bridges of municipality until the March of 2014. About 180 municipalities in Hokkaido have proposed the plans. One of the authors of this paper has concerned with drawing up the plans. Several risks were raised out by looking into the plans. The risks are the difference of the maintenance cost between the municipalities, the absence of the professional engineer in the government of the municipality, and the many charges for the big-scaled bridges those had been managed by another authority. In this paper, the increased cost burden of the citizens in the municipalities due to quick population decline is focused as the serious risk. Also the relation between the number of the repair works for the members of bridges to the financial indexes of local governments are considered in this study.

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Fatigue damage has been frequently observed at a connection between a track-beam and a cross-beam in welded steel girders of straddled-type monorail structure. This paper addressed FE analysis for appropriate maintenance of the straddled-type monorail. Fine meshed FE analysis was conducted to clarify the behavior of fatigue cracks due to the difference between a rigid-connection with a pin-connection, and to confirm the effect of moving manners of the pin-connection, span lengths, cants. Based on the parameter studies on FE analysis, we proposed the retrofitting method “Trapezoid Shaped Connection”.

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In steel structures, the installation of the additive and the various material is required for the purpose of improving the usability, repair and reinforcement. In most cases, welding joints and high strength bolts connections are used for the installation of such additives. But installing a bolt is accompanied by a constant partial loss of area and welding might cause the induction of the fatigue crack. Therefore, we consider the joining method using the stud pin that does not require welding and without a partial loss of large area such as a bolting joint.

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This study shows importance of maintenance by reporting structural accidents in 1970s and 80s of aging viaducts due to lack of maintenance in New York City. As for Japan, Tokyo Metropolitan Expressway (TME) and Hanshin Expressway (HE) are selected. The relationship between infrastructure age and maintenance cost is discussed with the recent five years data. The older the route becomes, the more its maintenance and rehabilitation cost becomes. Suppose the maintenance cost of TME would increase linearly, its cost in 2050 would be more than twice. HE doesn't have strong correlation but weak trend toward increasing maintenance cost because HE operates maintenance construction intensively with its route closed and large parts of HE were reconstructed after the 1995 Great Hanshin Earthquake.

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After the 2011 off the Pacific coast of Tohoku Earthquake, bolt loosening at brace member joints was found out during the inspection of transmission towers. As the shear bolted joint is allowed the bolt slip, the bolt loosening doesn't influence load bearing performance of transmission tower structures immediately. However, if a lot of bolt drop occurs because of the loading history after the bolt loosening, the possibility of load bearing shortage may be caused. In this paper, we conducted bolt loosening and bolt drop reproduction tests, and examined a numerical model and the procedure to analyze the rotation of bolt while considering the experimental bolt loosening behavior. And we summarize some findings concerning the bolt loosenig and drop based on the investigation results.

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