In this study, we verified the basic properties of high strength bolted friction joints with slits as the bolt holes to improve the energy absorption capacity from static loading tests and static analysis. The results showed that the coefficient of slip remained almost constant with increasing slip after the initial slip. It was also shown that the shape of the slit affects the resistance force after sliding. Furthermore, we propos ed a joint that amplifies the post slip resistance and elucidated its mechanism.

One of the typical fatigue cracks is observed the lower flange on the bearing of railway rivet girder constructed until 1960’s in many. The fatigue crack is caused by the deterioration, such as the gap on the bearing and the local wear at the bottom of end stiffener due to aging. This paper reports the results of load test and FEM analysis conducted for investigating the effects of the support condition of those on the fatigue crack generation and propagation. As a result, we confirmed the relation between the deterioration state of the bearing and the stress increase at the lower flange, and the tendency of the fatigue crack growth rate and direction.

One of the typical fatigue crack in welded girder of railway steel bridge is observed at the bottom of end stiffener. To repair the subsidence of bearing causing the stress concentration and the fatigue cracking at the bottom of end stiffener is burden on maintenance management. This study proposes the retrofit of end stiffener with the method with splice plate used bearing type bolt for pressing. This paper reports the results of static load test and cyclic load test conducted for evaluating the applicability of the proposed method.

The metal-sprayed surface and hot-dip galvanized surface are often applied to high strength bolted joints and bolts in those joints are tightened by turn-of-nut method. However, it is still not enough clear how much axial force is induced into bolts by difference of bolt diameter. In this paper, we investigated characteristics of induced axial force by literature search in high strength bolted joints using turn-of-nut method. From the results, we show difference of induced axial force by bolt diameter.

RC slabs of existing road bridges have been deteriorated by repeated vehicle wheel loads and by water and chloride ion penetration into RC slabs, which lead to scaling and a sandy surface of RC slabs. Replacing the top surface of an RC slab with UHPFRC is one of the most effective methods to solve these problems. Therefore, in this study, finite element analysis on the punching shear tests of RC slabs with UHPFRC overlay repair and strengthening has been conducted to examine the contribution of UHPFRC to load bearing capacity. From the results, we have found that UHPFRC overlay improved the load bearing capacity and contributed to delaying crack progression as well as reducing strain of rebar and bending deformation.

Curing of concrete is an important part of the construction process because it affects the durability of concrete. However, unexpected accidents may shorten the curing period or cause the concrete surface to dry out during the curing period, resulting in a loss of durability. In this cases, it is expected that the concrete surface can be re-wetted to restore its quality. In this study, the quality changes of concrete surfaces were quantitatively evaluated using an air permeability test after re-wet curing the concrete with different initial curing periods of concrete. The results of a quantitative study of the resistance of concrete to penetration of chloride ions by re-wet curing are also reported.

The fatigue resistance of RC decks subjected to water penetration is known to become significantly degraded. However, it has been found that the fatigue resistance can be improved by shear reinforcement using carbon fiber grids and PVA fibers in a cross-section of a singly reinforced concrete deck. Although a quantitative evaluation of the optimum amount of reinforcement has not yet been performed. In this study, the fatigue resistance was examined based on fatigue loading tests and a three-dimensional FEM analysis using beam specimens in order to evaluate the synergistic effect under fatigue action. The results indicated that both carbon and PVA fibers had a significant effect on fatigue resistance. Therefore, the fatigue resistance was verified by fatigue tests on RC decks.

In order to expedite and save manpower for replacement of existing bridge deck slabs, a longitudinal mechanical joint for precast prestressed concrete (PC) slab is proposed. A static flexural test of RC beams and a static punching shear test of PC slabs were carried out. In the static flexural test, it was found that the flexural capacity of RC beams joined by the mechanical joints was equivalent to that of RC beams without joints, and the tensile force due to bending moment was transferred from the mechanical joint to the rebar in the beams as calculated. In the static punching shear test, it was confirmed that the PC slabs joined by the mechanical joints showed the same load-displacement relationship and the punching shear capacity as those of RC loop joints generally used for the precast PC slabs.

In previous experimental study, strengthening by post tensioning anchors improved seismic performance of RC column with low reinforcement ratio, such as spillway gate pier, under cyclic loading. This study verifies the applicability of 3 bond-slip models to behaviors of post tensioning anchors in contact with concrete by comparing finite element analysis and previous experiments. The results suggested that, the bond-slip model for deformed rebars and the no-bond model can be applied to a full-bond post tensioning anchor and an unbonded anchor respectively.

The objective of this study is to investigate the fatigue resistance of a slab system consisting of precast PC slabs and a novel joint system consisting of high-strength fiber reinforced mortar and screw-type rebar. The fatigue resistance is assessed through a wheel load test, initially designed to comply with the NEXCO 442 test method to ensure a 100-year service life; subsequently, the test has been extended to further verify fatigue resistance at higher repetitions, higher loads and in wet conditions. The results demonstrate that the slab system's fatigue life largely surpasses 100 years. Furthermore, comprehensive post-test investigation confirmed that no significant or localized damage occurred to either the joint system or the slab during the test.

In order to estimate potential deterioration conditions such as alkali-silica reaction, it is necessary to evaluate the strain distribution concrete inside properly. To evaluate the strain distribution, core drilling experiments using the stress release method were conducted on concrete specimens. In the experiments, the eccentric load was applied, and the strain was measured by the embedded sensor. Moreover, the stress analysis was performed and the results were compared with the experimental results. As a result, it was confirmed that the embedded sensor can measure the strain distribution of the concrete inside. Furthermore, it was confirmed that the accuracy of the elastic strain was improved by applying the expansion strain of the mortar.

The purpose of this study is to evaluate the damage level of concrete delamination or internal defects using impact elastic waves. First, the relationship between the sound waveform obtained from steel ball drop test and artificial corrosion crack in concrete was discussed. It was confirmed that the method considering attenuation property of wave form is important in order to evaluate damage, and a method of evaluating attenuation graphs using normalized wave energy curve was proposed. The proposed method was applied to steel ball drop test and laser hammering test to the specimen and succeeded not only to detect damage area but also to evaluate damage level. In addition, the applicability of the method to the surface vibrations on the existing tunnel lining using a laser hammering system was confirmed.

As a technology for measuring strain changes in prestressed concrete (PC) members, we are focusing on distributed optical fiber sensors that are highly durable and capable of measuring the strain distribution of an entire structure. Strain was measured using this sensor in loading experiments and outdoor long-term exposure experiments on PC members. As a result, it was confirmed that measurement using this sensor is effective as a method for understanding the bending behavior and long-term strain fluctuations when an external force acts on a PC member. In addition, as a result of examining a method for evaluating the effective prestress of PC members from the obtained strain, we found that it was necessary to consider the influence of the installation environment.

In this study, the results of impact loading tests were evaluated to determine whether the thick plate theory, which is based on the three-dimensional elasticity theory, is applicable to the maintenance of bridge deck slabs. As a result, it was shown that it is possible to confirm the effect of reinforcement and to grasp the progress of deterioration by comparing the results with calculated values. The results of the impact loading tests are considered to be consistent with the thick plate theory due to the effect of the vibration-damping rubber placed at the weight drop position of the testing machine.

Loading test was carried out at four span continuous PC box girder bridge degraded by deicing agent. The bridge was loaded up to 1900 kN with hydraulic jacks. Stiffness of bridge was reduced when the load reached 1200 kN. This trend was succesufully simulated by non-linear FE analysis in which long-term monitoring data was considered. However, experiment was lower than FE analysis with regard to cracking load at several segment boundaries. This result indicates that strain measurement is necessary in long-term monitoring to detect the signs of deterioration earlier. Therefore, we focused on optical fiber sensors that can measure strain distribution. Consequently, we developed estimation method for the crack position and crack width from optical fiber data.

Many urban expressways have been in service for more than 40 years, and aging of the entire structure is becoming a serious problem. In particular, the progress of deterioration of reinforced concrete (RC) decks bearing the direct load. A wheel load running test can be used for evaluation of the durability of RC deck. However, since a higher-than-actual load is applied directly onto the RC deck slab without asphalt pavement, the behavior between movement and response in an actual traffic environment is not necessarily reproduced. In this study, to make sure the relationship between the action and response of RC deck, strain measurement was performed on actual RC deck of an urban expressway using a constant load vehicle, and various factors affecting the strain response of RC deck were analyzed.

This study evaluated the fatigue durability of the precast replacement RC slab bridges arrayed in parallel with the width direction by the wheel load running fatigue test. The experimental results showed that the equivalent number of cycles of specimens with the filling part at the affected bending and shear was reduced to 0.60 and 0.82 times, respectively, as compared with the standard RC slab. In addition, the equivalent number of cycles of specimens with the adhesive applied to the roughening surface of filling members were 0.95 times and 1.01 times, respectively, as compared with the standard RC slab. This experiment yields that applying adhesive contributes to improving fatigue durability. Therefore, we propose the use of adhesives at the interface between the precast slab and the roughening surface of the filling part in the installation of the actual bridge.

This study deals with non-destructive damage judgement of RC member by hitting response based on k-nearest neighbor algorithm. To advance the performance of judgement results, the semi-supervised learning aided by the k-means method is implemented which can increase the number of labeled training data for the k-nearest neighbor algorithm. Validity of the proposed method is verified through an shear loading experiment with RC beam specimen. Furthermore, the effects of parameters used in the semi-supervised learning on judgement results are discussed.

The purpose of this research is to suggest the utility poles replacement evaluation method from the structural dynamics perspective. This study shows the result of bending test of utility poles subjected to cyclic loading to clarify the failure progress of utility poles by cyclic loading, and measurement of utility poles behavior to confirm the correlation between damage and dynamic characteristics. As a result, as for the bending test, it was confirmed that failure of utility poles subjected to cyclic loading is caused by flexural compression failure by the accumulation of fatigue damages of the concrete. As for dynamic characteristics, it was confirmed that there is the correlation between damage and change of dynamic characteristics, especially natural period and damping.

The authors have developed precast RC-slab made of Ultra high-strength PVA reinforced concrete (PVA-UFC) having thin thickness, lightweight and high fatigue durability. In this study, fatigue durability of joined PVA-UFC slab is evaluated by wheel load running test according to "NEXCO Test Method 442", and loading with a step-wise loading method by PWRI until 394kN. Even though the slab is designed about 80% thinner thickness than ordinary slab based on "Specifications for highway bridges", the specimen developed sufficient fatigue durability. Thus, PVA-UFC slab including the joint showed over 100 years fatigue durability at the Test of 442, and at the Test of PWRI, over 300-times fatigue durability of NEXCO 442 loading was recognized even under a wet condition having pool on the surface.

This study investigated repair/strengthening effect for RC beams with corroded steel bars. The significance of this study was that a new idea of repair/strengthening method using CFRP strand sheets was proposed for deteriorated RC beams without any measures such as patch with mortar repair and replacement of steel bars. As a result of this study, CFRP strand sheets embedded in fiber reinforced mortar with high-strength and high-ductility, UHP-SHCC, effectively enhanced the flexural performance as well as those bonded with epoxy resin. No delamination or sheet pullout were observed until failure as well. Moreover, the results of sectional analysis quantitatively confirmed the effectiveness of the proposed method.

During placing of concrete, it is necessary to pay attention to the time interval of placing concrete to prevent cold joints from occurring. For this reason, the STANDARD SPECIFICATIONS FOR CONCRETE STRUCTURES-2017 [Materials & Construction] defines 2.5 hours as the standard allowable placing on consolidated time interval when the outside temperature is below 25℃. In this case, concrete is placed in separate top and bottom sections. Bridge has thin deck slab and the connection is at an angle. We report on the investigation regarding the time interval of fresh concrete for bridge deck slab.

This research aims to improve learning accuracy when mislabeled data is contaminated in training dataset in rebar corrosion judgement using neural network. A hammering experiment was conducted using beam specimens with rebar corroded by electrolytic corrosion, and a method for removing mislabeled data using the local outlier factor method was investigated for training dataset contaminated with mislabeled data. As a result, it was confirmed that a certain amount of mislabeled data could be removed, improving the learning accuracy of the neural network. In addition, it was considered the influence of each parameter, such as the number of training data, on the removing results and learning accuracy.

In 2023, there are approximately 730,000 bridges nationwide in Japan. Of these, 477,000 bridges are managed by local municipalities. Many of these smaller bridges are structurally degraded, and these bridges often lack seismic resilience. Problems arise in replacing bridges due to densely populated areas and narrow surroundings. To address this, our study focuses on PC decks using carbon fiber tendons that are premanufactured and cut as needed, aiming to minimize burden on local residents and speed up construction. However, mechanical characteristics for thin PC decks remain uncertain. Therefore, it was clarified the mechanical characteristics and replaced the PC decks on an actual bridge.

For the purpose of clarifying the load-bearing mechanism and load-bearing capacity of the joint during two-way loading, we investigated the beam-column joint of ridged frame viaduct by finite element analysis. Inner radium of axial rebars in the transverse beam affects the bearing capacity of the joint because a compressive strut is formed at the bending inner radius when the angle of the loading is around 0°. The effect of tie reinforcing bars at joint increased the bearing capacity by up to 10% in any loading direction. In addition, when the torsional moment of the longitudinal beam was considered, the horizontal force was shared at each fulcrum, but it did not affect the joint bearing force.

While CLT(Cross-Laminated-Timber), which is lightweight and is resistant to fa- tigue, is expected to apply to bridge deck, it is needed to install commercially avail- able railing post on it for popular use. It is important to confirm the safety and to investigate the load bearing performance of the joint part between the railing post and the CLT deck. In this study we propose replaceable railing post fixed by lug screw bolt so that we can only replace the upper part of railing post after fracture. We show relatively simple modeling of the CLT deck with the railing post using general- purpose 3D FEM tool and illustrate the numerical results. The modeling considering elasto-plasticity for steel members and orthotropy for CLT member seems to well simulate the deformation behavior of the CLT deck with the railing post.

The use of adhesive bonding is to be a key in realizing longer spans and larger sizes of FRP structures. Then, this study focuses on a strengthening technique using a wrapping single layer of glass fiber by Vacuum Infusion molding technique over conventional double strap joints of GFRP plates. The strengthening effects of the technique on the tensile performance of the joint are investigated through tensile experiments. The experimental results indicated that the VI wrapping technique increases the loading capacity of the joint and FEM analysis revealed that the one effectively reduces the shear and normal stresses in the adhesive at the edge of the connecting plates.

The strength and deformation capacity of FRP members when subjected to shear forces are still largely unknown. This study reproduced the results of three-point bending tests by the finite element method. The shear behavior of GFRP members and its evaluation method were analytically investigated by changing the thickness and width of members in the analytical model including failure damage model. The analytical result found that the strength ratio decreased linearly as the web width-to-thickness ratio increased, and the strength ratio decreased exponentially as the flange width-to-thickness ratio increased.

In a composite girder, the concrete slab and steel girder are not perfectly integrated in practice, and there will be misalignment between the concrete slab and steel girder depending on the stiffness and spacing of the headed studs. This study evaluates the stiffness and flexibility constants for studs with varying diameters and spacing, based on the results of push-out tests of headed studs conducted by the authors. It was found that the theoretical equations of the flexible composite girder considering the stud stiffness correspond to that given by FEM analysis. The behavior of horizontal shear forces acting on studs based on the theory of flexible composite girders is also clarified.

Carbon fiber reinforced plastic (CFRP) bonding has been applied to corrosion- damaged steel members subjected to compression. Uniaxial compression tests and eigenvalue analysis of specimens with CFRP bonded to intact steel plates have confirmed the strengthening effect of CFRP bonding. However, there is no method for estimating the elastic buckling load of CFRP bonded to a cross-sectional defective steel plate with elastic putty. Therefore, this study proposes a method to estimate the elastic buckling load of CFRP-bonded steel plates with cross-sectional defects. The proposed method was in good agreement with the eigenvalue analysis using the finite element method and the maximum load in uniaxial compression tests.

One of the repair methods for corroded steel tube is the CFRP bonded repair. However, the debonding of CFRP is one of the concerns about the CFRP bonded repair. To prevent the debonding of CFRP, the shear stress or energy release rate in the adhesive layer is applied to the design verification. A theoretical analysis of CFRP bonded steel tubes has been proposed to calculate these debonding parameters. However, no theoretical analysis of steel tubes partially bonded with CFRP is given. In this study, the shear-lag theory was applied to the steel tubes partially bonded with CFRP subjected to axial force or pure bending moment. Then, finite element analysis was performed to confirm the validity of the derived equations.

There is growing needs to replace damaged and aging wooden floor slabs of pedestrian deck, promenade and so on with lighter and more durable ones for a long-term use and an easy erection. Then focused on in this study is a sandwich composite panel, which consists of GFRP plates as surface material and rigid polyurethane foam as core material integrally and is molded by Vacuume Infusion techinique. Three-point and four-point bending tests of the sandwich panels on dry and wet conditions were conducted. The experimental results revealed that the wet conditions hardly influence on the bending behaviors of the GFRP sandwich panels and the panel can be applied to a span up to 1.2m.

In this study, an existing nonlinear concrete constitutive model was improved and applied to local damage analyses of concrete structures subjected to low to high velocity impacts. The yield surface and the tensile softening model were modified, and the parameters in the model were determined through numerical analyses of compression tests. Dynamic strength, wave propagation, and local damage were also considered with the improved model. Finally impact test simulations from low to high velocities were conducted, and it was confirmed that the improved model can reproduce the time history response of the concrete slab and local damage such as penetration, scabbing, perforation, and deep penetration. The effect of the numerical erosion criteria proposed in the past was also discussed.

This study investigated the blast pressure characteristics acting on a structure by conducting explosion tests and numerical simulations.Prior to the explosion tests, a method for evaluating the blast pressure characteristics proposed by the U.S. facility criteria was described and its unpublished concept was discussed.Then, scaled explosion tests for investigating the blast pressure acting on a box-type structure were conducted by using composition C-4 high explosive. Blast pressure characteristics at a front wall, a top roof, lateral and rear walls were discussed comparing those estimated by the U.S. facility criteria. Numerical simulation was carried out to further investigate the blast pressure characteristics. Numerical results showed good agreement with the test results.

In this study, the applicability of the proposed similarity law to gate-shaped rahmen and fence structures was investigated, comparing its estimation accuracy with the replica law. The proposed similarity law is particularly applicable to estimating the elastic behavior of the above two structures in the direction of action. Replica law is more applicable than the proposed law of similarity for structures subjected to impact and collisions when not affected by gravitational acceleration. On the other hand, the proposed similarity law is more applicable than Replica law under the gravitational acceleration.

In recent years, there has been an increase in natural disasters, such as large-scale debris flows, prompting considerations for reinforced measures for steel pipe Sabo dams. Consequently, there is a need for an analytical method to evaluate the reinforcement of steel pipe Sabo dams. The study analytically examines the damage factors of a steel pipe Sabo dam at a real scale to reproduce the damage cased by large-scale debris flow. Additionally, it investigates the reinforcement effects of increasing the number of joints and using joint covers under debris flow disaster conditions. Therefore, the proposed method can be an effective approach for evaluating and verifying retrofitting measures for existing steel pipe Sabo dams.

Explosions occurred inside a structure due to terrorist attacks or accidental explosive incidents can cause severe damage to people and structures outside the structure. In order to reduce or predict and avoid such damage, it is necessary to accurately evaluate the characteristics of the blast pressure caused by internal explosions. However, the characteristics of the external blast pressure caused by internal explosions can only be determined for limited conditions. In this study, internal explosion tests using a steel specimen with openings on the top and sides were conducted. The effects of the position and size of the openings on the blast pressure-time profiles were examined, and the distribution of the maximum blast pressure and blast impulse were evaluated.

In this paper, an impact resistance behavior of the steel post with higher flexural stiff- ness for the 4 m high rockfall protection fence anchored into the 3 m high plain con- crete retaining wall was numerically investigated by means of 3D elaso-plastic dynamic response analysis method. H-section steel members of H200 × 200 × 8 ×12 were used as the post. The results obtained from this study are as follows: 1) the design force may be evaluated by using fully plastic load irrespective of the magnitude of the input energy; 2) when the loading position is lower, the shear deformation of the post becomes more severe; and 3) the anchoring depth specified by the guideline may be reasonable even though the input energy increases.

The applicability of the proposed FE model on the impact response behavior of the rockfall protection fences anchored to the plain concrete foundation was investigated comparing with the experimental results for the full-scale fence models. In this study, the fences having both conventional type and base-plate type anchoring systems for the steel posts were used. The results obtained from this study were as follows: 1) the time histories of the impact force and tensile forces acted to the wire-ropes which may be key parameters for designing the fence system considering the dynamic response characteristics, can be better predicted by using the proposed method; and 2) the local buckling behavior of the steel post near the base can be also appropriately evaluated.

A large rockfall disaster on Hakusan Shirakawa-go White Road occurred on a forest road in Ishikawa Prefecture on December 14, 2018. This is the only important road connecting Ishikawa and Gifu prefecture. Therefore, it was out of service for four and a half years. Fortunately, it was fully opened at May 20 2023. Firstly, this disaster is explained in detail. Subsequently, the rockfall simulation method is introduced that had been developed by the authors. The method is applied to this real slope. The results of the risk evaluation of rockfalls on a road have been concretely shown. A rock shed is located on the road as a protection structure against rockfalls from the steep mountain slope. Finally, the current extent of the risk for rockfalls on the road considering the rock shed been shown.

In this study, 24 cases of static loading and impact loading experiments were conducted using shear-failure type RC beams and cushioning materials in order to analyze the energy absorption characteristics of cushioning materials in shear failure type RC beams subjected to impact loads. Two types of cushioning materials made of foam resin and two types of weights with different masses were used in the experiments. As a result, it was found that the energy absorbed by the RC beam under the impact load was roughly equivalent to the kinetic energy possessed by the weight and beam immediately after the collision. It was also found that the energy absorbed by the RC beam under impact load could be evaluated from the load-displacement relationship of the RC beam under static load.

Investigate the influence of the concrete constitutive law on the precision of numerical simulations for RC beams subjected to collision forces, simulations were conducted utilizing three distinct concrete constitutive laws. The numerical simulations were based on 134 impact loading experiments, including various cross-sectional dimensions, span lengths, reinforcing bar ratios, masses of weights, and impact velocities, conducted at both domestic and international research institutes. The concrete constitutive laws employed included the K&C model and two continuous surface cap models. The evaluation of analysis accuracy and the applicable range for each concrete constitutive law focused on the maximum displacement.

Recently, natural disasters have been occurring due to abnormal whether. Especially, debris flow or woody debris have been increasing in valleys adjacent to residential areas. An open Sabo dam supported by cables has been proposed for small scale stream that is no-flow mountain stream. However, the response to debris flow loads remains unclear. This study investigates the dam’s response of debris flow impact force using an experimental channel and a sliding dam model. The experimental results indicates that debris flow load acting on the proposed dam is similar to that on a steel pipe open Sabo dam. Additionally, it was found that the load of cables decreases with increase of the dam’s weight.

In this study, a total of 18 cases of static and impact loading experiments using RC beams were conducted to estimate the maximum displacement of bending failure type RC beams subjected to impact load from the load-displacement relationship of the beam when subjected to static load. Two types of weights with different masses and two types of cushioning materials with different unit volume weights were used in the experiments. As a result, it was found that the maximum displacement of the beams could be estimated on the safe side based on the equivalent relationship between the energy transferred to the beams during the falling weight and the energy that could be absorbed by the beams obtained from the static loading tests.