Corner plates are often welded at the intersection between web and flange in steel box girders. As a measure against fatigue in the weld joint between corner plate and lateral rib, the end of corner plate was cut-out in U-shape. Nevertheless, fatigue cracks have been generated from exposed root on the cut-out surface. In this study, fatigue strength and fatigue life improvement by ICR treatment were investigated. The fatigue strength of the weld joint was JSSC-G class. Application of ICR treatment improves the fatigue strength by 1 grade or more, and the fatigue limit was improved as 59 N/mm² or more. Furthermore, stress concentration factor around exposed root was investigated by finite element analysis.

In this study, the effect of the stress state of a welded joint during application of high-frequency mechanical impact (HFMI) treatment on the resulting fatigue strength was investigated. Longitudinal attachment joints were treated under a state in which a static load was applied and subsequently tested under a constant stress amplitude with stress ratios of 0 or 0.5. The test results indicated that enhanced fatigue strength can be achieved even under a high stress ratio when the joint is treated under the minimum stress of fatigue loading. In addition, residual stress measurements and finite element analysis simulating a treatment process indicated that the magnitude of compressive residual stress introduced to a weld toe is similar regardless of the stress state in the joint during treatment.

According to the Specifications for Highway Bridges, the slip coefficient of high-strength bolted friction type joints is specified as 0.4 when both of faying surfaces of the base metal and the splice plate are rough steel surface, and it is 0.45 when both surfaces are painted with inorganic zinc rich paint. In this study, slip resistance tests were carried out for the joints, where splice plates are painted with the inorganic zinc rich paint of a thickness 150 μm, and base plates painted with etching primer were cleaned by power tools to obtain rough steel surfaces. As a result, the slip coefficient was found to be greater than 0.4 under some conditions.

The continuous movement of the sun results in different amount of solar radiation at different positions of the exposed bridge structures, thus affecting the temperature distribution of different members of the bridge. In this paper, three existing steel bridges and the exposure test structure are selected as research objects to study their surface temperature distribution under direct sunlight. For each object, an infrared camera and temperature data logger are used to measure the temperature at specific positions of the whole bridge caused by direct sunlight in one day. On this basis, the temperature variation among certain members is discussed in conjunction of solar radiation and surrounding environment. The results show that the temperature difference between the components of the structure under direct sunlight is very obvious considering the size effect and the type of material.

Cracks are one of the important inspection items to keep concrete structures safe. In recent years, a method using an optical fiber sensor has been proposed as a method for efficiently measuring distributed strain over a wide area, and this method is suitable for large-scale concrete structures. Therefore, this study investigated the characteristic of the distributed strain for RC beam specimen using three types of measurement methods and two types of optical fiber sensor. Finally, we compared the strain measurement results and determined the cracks from strain measurement results.

In this study, the authors utilize the impact vibration test using a portable FWD machine as a simple soundness survey method of bridge decks. Reinforcing works including replacement of the deck was carried out in the target bridge. The tests were conducted before and after the deck replacement. We measured the response acceleration at various points on the deck. The deterioration check was examined by two methods. First, we examined natural frequencies by performing Fast Fourier Transform on the obtained acceleration. Next, we compared acceleration waveforms at each measurement point and investigated the acceleration gap that occurred between two measurement points.

In this paper, we proposed the application of the 3D Convolution Neural Network (3D-CNN) on the Ground Penetrating Radar (GPR) data to detect segregation on deck slab on two real bridges. We set this up as a classification problem whether the damage exists in a certain area. First, high accuracy of Area Under the Curve (AUC) was obtained when we trained and evaluated the models on each single bridge. Second, it decreased on the models which we trained with one bridge and evaluated with another. It shows that the features of radar data required to estimate are different on the bridges. Finally it was high on the models which we trained and evaluated on the both, and it shows a possibility that the generalization performance can be acquired by collecting radar data on various bridges.

This paper deals with a corrosion crack judgement procedure based on neural network. The primary focus of this study is put in the judgement of cracks occurred by re-bar corrosion using analyses of hitting sound spectra. For this purpose, neural network which is one kind of machine learning method is employed to determine the presence of the corrosion cracks. The validity of this procedure is evaluated from an experiment with reinforce concrete specimens, and, effects of parameters of hitting conditions and process of sound spectra are discussed with various indices.

This study focused on the small concrete spalling caused by internal defects of time dependent behavior and investigated the relationship between spalling resistance and vibration properties using laser hammering system. By referring the laboratory test data, it was succeeded to detect for small spalling by using the raster scan measurement. In addition, the specimen’s vibration property data was simulated by the modelling of internal defect’s spalling resistance with spring constant. Finally, based on the verification of the issues and advancement of diagnostic by comparing human diagnostics method applying the existing tunnel lining, an effective way of implementing the laser hammering system was suggested.

This paper presents an evaluation of shear failure mechanisms in reinforced concrete (RC) pile supported footings by using a nonlinear numerical analysis. A rigid-body-spring model, which is one of discrete type approaches, is used to analyze shear failure behaviors of RC footings. The numerical model predicts the three dimensional crack development and the punching shear capacity, and is validated by comparison with experimental observations. Sensitivity analyses are conducted to study the effect of longitudinal reinforcement arrangement that affects productivity of reinforcement placement in construction.

Prestressed concrete ridged-frame bridges "PC ridged-frame bridges" and PC long-span bridges such as PC continuous girders are often used at intersections such as rivers and roads, and PC long-span bridges are particularly susceptible to long-term deflection. PC long span bridges are particularly susceptible to long-term deflection, especially in the case of direct-connected track. In this study, a frame analysis model using beam elements was applied to a PC ridged-frame bridge that was designed and constructed, to understand the behavior of long-term deflection and to identify a structural type that is less prone to long-term deflection.

In some railway bridges, it took a lot of time to recover from the damage of the concrete around embedded part of circular steel stopper caused by recent earthquakes. If the damage can be controlled, recovery will be easy. In this paper, experiments and analyzes focused on the effect of amount of reinforcing bars and edge distance on the failure mechanism are performed. It was clarified the shear failure is occurred when the shear strength of the concrete around embedded part of circular steel stopper is lower than the full plastic circular steel stopper strength, and the cover concrete failure is occurred when the cover concrete strength is lower than 80 persent of the full plastic circular steel stopper strength.

In this study, separation and cracking behavior under fatigue loading of filling concrete in joints between precast deck slab panels was experimentally investigated. And we proposed improving methods of fatigue durability applying adhesive on the end surface of precast slab joints. Wheel load running fatigue tests were conducted to verify validity of our proposed method. The fatigue tests revealed that the case of with adhesive suppresses cracking due to peeling and fatigue durability was improved by 1.2 times by using an adhesive. In addition, effect of deflection range on fatigue durability was clarified from the results of dynamic measurements of deflection.

The present study aims to numerically investigate the essential factors affecting stepwise construction stress in RC deck slabs of multiple span steel box girder bridges utilizing layered model. According to the results of the numerical simulation on a successful case of cracking mitigation in the RC deck slab of 4-span Fudaigawa Ohashi bridge, it was revealed that time interval between concrete placing steps, concrete volume of interior support lots and placing sequence were main driving forces altering the generated tensile stress. Consequently, an effective stepwise construction strategy was proposed for mitigating maximum experienced tensile stress and residual tensile stress in concrete lots due to stepwise construction. The effectiveness of the proposed strategy was verified in back analysis of 7-span Shinkesen Ohashi bridge.

This study is the result of investigating the relationship between the repetitive action conditions of compressive stress within the elastic limit and the salt penetration of concrete members. The salt water submergence test, ultrasonic velocity test, and compressive strength test on the concrete specimens were performed after repeatedly applying compressive stress on it. As a result of the test, it was clarified that an increase in the compressive stress and the number of repeated stress application within the elastic limit decreased the salt penetration velocity. This indicates that repeated stress application within the elastic limit has a significant effect on salt penetration velocity.

In this paper, the movement of the neutral axis caused by the corrosion of the compression bars and the change in bending performance caused by the movement of the neutral axis are investigated. In order to simulate various degradation periods, RC beams with corroded compression bars were fabricated by electrical corrosion and subjected to bending tests.It was found that when the compression bars corroded, the stress was not transferred to the concrete part above the corrosion crack.In addition, whether or not the corrosion cracks penetrate the cross-section is an important factor controlling the residual performance.

In recent years, the deterioration of reinforced concrete (RC) road bridge decks has become a serious problem. The fatigue resistance of RC decks can be strongly reduced due to water penetration. The current countermeasures to this problem are the use of drainage and waterproofing. However, there have been few studies of coping with fatigue resistance to ensure on infiltration of water into deck. In the present study, the water resistance of RC decks with different cross-sectional and bar arrangements was investigated using cyclic fatigue and wheel load tests. Based on the results obtained, the optimal cross section for maximizing the fatigue resistance in the presence of water penetration was identified.

The aims of this study are to investigate the repair effect and the ultimate load-carrying capacity of beam specimens, which were quarried from removed deck slabs with steel plate bonding. From the four-point bending test, the structural behavior and the load-carrying capacity of four specimens with and without steel plate bonding, three of them were repaired by the re-injection of resin, were compared and analyzed with structural calculation. The test results showed that the specimen, which was pre-loaded and induced bending cracks, recovered the bending stiffness and the load-carrying capacity after the re-injection of resin. Finally, the specimen reached the ultimate state due to the debonding of interface between the steel plate and the resin.

Heavy rain disaster was happened on July 2020 around Kyushu. Particularly Kuma river system located in the southern part of Kumamoto prefecture had serious damages, e.g. nine road bridges were flowed out. Okitsuru bridge one of them was focused on this paper. This was prestressed T-shaped concrete beam bridge. There were large space under the deck between the gieders and edge cross girders. So buoyancy caused by the spase it was additionally applied in case of going under water. Possibility of floating, sliding off and falling down at the time of floo d is discussed.

Recently, FWD (Falling Weight Deflectometer), which evaluates the soundness of pavement, is used to evaluate the deterioration of bridge decks. The method has been proposed in which the degree of deterioration is evaluated based on the structural response of the deck. Although the FWD test can easily measure the impact load and the amount of deflection, it is difficult to say that the degree of deterioration can be evaluated accurately due to the local deformation of the pavement due to the impact load. Therefore, we have developed a Self-propelled Impact Vibration Equipment (SIVE) that suppresses the effects of local deformation and jumping of the pavement, measure the response acceleration of the bridge with an accelerometer installed on the pavement, and integrate the time on the second floor. We tried to evaluate the degree of deterioration of the bridge by calculating the amount of deflection of the floor slab.

Monopile type foundations have been mainly applied for offshore wind turbines in Europe, but jacket type foundations may be applied when installation of monopile is difficult due to rock conditions in japan. However, the undersea grouted connection of jacket type foundation possibly increases the nominal contact stress of grout and probably have unreasonable connection shape. Static loading test and FEA for both jacket type foundation with grouted connection and new sleeve pipe footing type foundation with grouted connection have been conducted. As a result, it is clarified the maximum load capacity was lower in the former connection due to the influence of the peeling between steel pipe and concrete, and higher in the latter due to the behavior of steel pipe and concrete as a composite structure.

Recently, the concrete slabs that have been seriously damaged due to aging are being replaced with precast prestressed concrete slabs, in Japan. When replacing the concrete slab of composite girder, it is necessary to reduce the weight of the precast slab in consideration of the effect on the existing steel girder. On the other hand, it is also required to efficiently place studs in the box holes of precast slabs. Therefore, the authors are developing the replacement method in which high strength headed studs are placed on the precast slab using lightweight concrete of class-2. The shear resistance and fatigue strength of high strength headed stud found from the static and fatigue push-out test are reported in this paper.

In this study, we focused on the thin mortar layer applied to adjust the height between the Precast PC slab and the steel girder. We fabricated specimens with parameters such as the thickness of the thin mortar layer and the mortar strength, and discussed the effect on the stud shearing force by push-out test. It was proven that crack was generated in the thin mortar layer by the working of bending in addition to shearing force, when there is the thin mortar layer, and that stud shearing force lowers. Therefore, it is necessary to propose a new design formula for the stud shearing force when there is the thin mortar layer between the Precast PC slabs and the steel girders.

To find voids in concrete, when we used a radioisotope backscatter detector, the thermal neutron measurement results included the effect from the sides of the detector in our prior studies. This is caused by scattered fast neutron in all directions from the source. To solve this problem, two types of experiments were conducted. In the first, the characteristics of different moderators were investigated to choose the applicable material. In the second, when the moderator was attached to the void detecting system, movement of radio-isotope count on mock specimen were examined experimentally. The experiments in this paper revealed that attached moderator to this device improves the void detection capability.

This study investigated evaluating method of the member strength for channel members fabricated from glass fiber reinforced plastic (GFRP) experimentally. The tensile and compressive tests were conducted on coupon specimens, plate element specimens and member specimens using two types of GFRP and two sizes of channel members in this experiments. As a result, the ratio of member strength to average strength of coupon test and plate element test was clarified. Additionally as for the tensile test, the relationship between the size of the specimen (thickness, width and sectional area) and the average strength was also clarified.

RC piers are required to have improved seismic performance, so there some concerns that the reinforcement bars are overcrowded and work efficiency is reduced. We proposed a composite structure with studs placed on I-beam webs. In this study, we fabricated a composite bridge pier that incorporates the proposed structure as the core of the pier, and confirmed its structural performance by a cyclic loading test. As a result, it was confirmed that the composite bridge pier has the same load bearing performance and ductility compared to the RC pier. Furthermore, since I-beams have higher buckling resistance than rebars, it was shown that there is a possibility that the number of lateral ties and cross-tie rebars can be reduced in the proposed composite pier compared to the RC pier.

For the reinforcement of piers in water bodies, the method that has the high constructability and sustainability with low river area inhibition rate, which use polymer cement mortar roll to inforce has been well used to solve rotting and sustainability issues. As for the same method, the reinforcement effect has been verified by using standard specimen but in the case of specimen with low deformation performance using fine axial reinforcing bars, the reinforcing effect may not be sufficient. In this paper, we reported the reinforcement effect of bridge pier that used the low diameter rebar was confirmed by cyclic loading test.

This study investigated applicability of the similarity law proposed by the authors for steel cantilever beams subjected to low velocity impact, by conducting experimental tests and numerical simulations. In a series of tests, a steel ball collided with a steel cantilever beam at velocities of 1-4m/s. Through the comparison of the motion of the steel ball, displacement and strain of the steel cantilever beam between a full-scaled and scaled steel cantilever beams, the proposed similarity law was found to be applicable. Based on the result, the similarity of the impulse was discussed focusing on the role of the coefficient of restitution which important factor for the proposed similarity law.

A Sabo dam is constructed to protect the infrastructure of our lives, but debris flow containing large driftwood have lately been occurring, and large driftwood are flowing into our living areas. The driftwood flow over an existing Sabo dam, and it is necessary to reinforce to the Sabo dam given trapping effect. Therefore, the hangover-type driftwood catchment is proposed with reference of driftwood disaster. However, the external load evaluation for the design is unclear. The study experimentally elucidates the external loads of hangover-type driftwood catchments given to an existing Sabo dam. The results showed that the load was affected due to the amount of initial sediment and driftwood volume.

In order to make clear failure mechanism of steel pipe open sabo dam occurred at Nagiso in 2014, the miniture model experiments are carried out. Following suggestion reported by investigation committee, a dent deformation effect of steel pipe which reduces axial resistance of horizontal steel pipe is examined in addition to effects of pipe joint strength and preset sedimentary gravel at upstream side of the structure. Among these nine experimental cases in the dent deformation model, damage occurred only in the case which the joint part is 70 % strength to the base pipe and the initial sediment is 30 % of the dam height. A detail mechanism of failure and dent deformation effect i s examined through the observation of experimental results.

This study investigated an evaluation model for perforation failure of steel plates. Impact tests were conducted by using a 6.0kg flat-nose projectile with a diameter of 50mm. The projectile collided with 6mm, 9mm and 12mm thick SS400 steel plates at impact velocities of 40-100m/s. Test results revealed that the perforation of the steel plates induced failure only at vicinity of impact point. Numerical simulation was conducted to investigate the deformation mechanism and perforation failure of the steel plates. Finite Difference Analysis simulated the experimental results. Based on the test and numerical results, an evaluation model was proposed by modeling plastic hinges and elongation behavior. Validation of the proposed model was discussed by comparing with test and numerical results.

This study investigated impact resistant performance of steel fiber reinforced porosity free concrete (SFR-PFC) panels subjected to projectile impact by conducting projectile impact tests. Test results of two types of SFR-PFC panels with different mix ratio showed that local failures such as spalling, scabbing and perforation by using a 300g-mass projectile were restrained. Based on the test results, the scabbing and perforation limit thicknesses of SFR-PFC panels were estimated by using the modified NDRC formula. The test results revealed that the scabbing and perforation limit thicknesses of the SFR-PFC panels decreased by 35-45%, as compared with RC slabs

This paper presents a simulation for a full-scale falling rock protection net by using 3D-distinct element method. In addition, the proposed method reproduced the unevenness to represent the planar elements like clump model. First the collision experiment carried out in advance, the dynamic deformation process of wire net is recorded by video and high-speed camera, and the tensions of wire ropes are measured. Second, the net and wire ropes are modeled by cylindrical and spherical elements. The reproductivity of the analysis results is examined by comparing with the experimental results. Therefore, the interlocking between the wire and the dead weight, and relationship between the impact load and time in the experiment can be represented by the proposed method.

The purpose of this study is to develop a rockfall protection fence with maintainability that does not require the replacement work of parts even after rockfall capture. To inspect the performance of the protection fence, full-scale experiments and numerical analysis were carried out. In this study, a series of impact test on the fence which had a post height of 3.5 m and length of 15 m were conducted to evaluate adequately and precisely the absorbable capacity of the impact energy. After that, the protection fence exhibited an outstanding capacity for dissipating the impact energy from 107 kJ to 320 kJ.

In order to establish a rational design procedure for the anchoring depth of the steel posts for rockfall-protection fences embedded into the rockfall-protection walls, static and drop-weight impact loading tests on prototype through-type posts in case of coupling between bending and shear actions were conducted. The results obtained from this study were as follows: 1) plastic hinge was formed in the post near the upper surface of the wall not only under static loading but also under impact loading; 2) impact force excluding high-frequency components may be able to estimate approximately by using the static perfect-plastic load; 3) impact energy may be entirely absorbed by the post deforming excluding rotation of the wall; and 4) design values obtained from the specification may be in the safety side comparing with the experimental results.

In order to obtain basic knowledge for establishing a rational impact-resistant design procedure of the steel posts for rockfall-protection fences embedded into the protection walls, 3D elasto-plastic impact response analyses were conducted taking impact velocity of the weight as variables. The applicability of the proposed method was verified by comparing with the experimental results in the case of using the through-type steel posts and the amount of the numerically simulated absorbed energy of each member was also discussed. The results obtained from this study were as follows: 1) impact resistant behavior of the steel posts except for rotation of protection wall can be appropriately simulated, and 2) it was confirmed numerically that more than 80% of the input energy was absorbed by the deformation of the steel post.

Rockfall protective soil embankment consists of only soils. In some cases, it can be the most economical, workable, and maintainable rockfall protection construction. However, the performance-based design method is not established. In this study, the weight-impact test was conducted on a small-scale model with different materials and weight masses. The results are as follows. When made with clay as soil embankment material, the weight penetrates the soil embankment and the soil embankment is compressed. When made with sand, the soil embankment is sheared and the weight run-up. When made with gravel, the soil embankment is almost no deformation. And collisions with the same kinetic energy, it was shown that the larger the mass, the more massive the destruction.

A rockfall protective soil embankment is said to be a rockfall countermeasure work with excellent workability and economy, but a performance design method has not yet been established. In this study, we conducted a full-scale weight-impact test in a sand cushion installed in the pocket back of the embankment. In addition, we performed a 2D-DEM analysis. From the test, it was shown that the energy absorption performance is improved by increasing the sand cushion layer thickness and the incident angle of the rockfall. In addition, 2D-DEM analysis showed the possibility of estimating the sand cushion thickness at which the increase in energy absorption performance converges.

In this study, in order to cumulate knowledge on impact resistant behavior of the cushion rubber set reinforced concrete (RC) beams, keeping input impact energy constant the RC beams were consecutively subjected to drop-weight impact loads up to reaching the ultimate state. Two kinds of thicknesses for the cushion rubber were taken as variable: 25 mm; and 50 mm. The results obtained from this study were: (1) impact resistant capacity of the RC beams can be increased by setting the cushion rubber because of its flattening and dispersing effects for the high intensity impact force; however, (2) maximum and residual displacements of the RC beams may not decrease because impulse of the impact force does not decrease due to setting the rubber on the beams.

The impact resistant capacity of the reinforced concrete (RC) beams may be increased by flattening the high intensity impact force. In this paper, the impact resistant behavior of the cushion rubber set AFRP-sheet strengthened RC beams which reach ultimate state with sheet failure was investigated conducting drop-weight impact test loading with varying thickness of the cushion rubber. The results obtained from this study were as follows: the primary peak impact force can be decreased by less than approximately one-fifth; however, dynamic behavior of the beams may be similar irrespective of with/without setting the cushion rubber because of similarity of those impulses; and sheet fracture can be effectively restrained by setting the cushion rubber in the case of increasing input impact energy.

This study investigated blast mitigation performance of an aluminum honeycomb composite panel by conducting explosion tests. In a series of tests, the blast mitigation effect was examined by setting the aluminum honeycomb composite panel onto a steel plate subjected to close-in explosion. Composition C-4 explosive was used to impose the explosive pressure locally to a steel plate or the aluminum honeycomb composite panel. The scaled distance was varied to investigate the effects of the scaled distance on the mitigation effects. Test results revealed that the explosive pressure distribution significantly affected the mitigation effect. The relationship between the buckling region of the aluminum honeycomb composite panel and the blast characteristics was discussed.

As an effective method to protect against damage from a terrorist attack or accidental explosion, important facilities can be constructed below ground. To improve the blast protection performance, a mitigation system consisting mainly of expanded polystyrene (EPS) and sand can be laid above an underground structure. In this study, the effects of a metal sheet which protects an EPS plate from explosion on blast mitigation were investigated experimentally. From the test results, in the bending stiffness per width of a metal sheet approximately 30kNmm or less, the blast pressure was decreased and dispersed with the increase of the bending stiffness per width of the metal sheet.