A heating experiment assuming a bridge fire was conducted on cruciform columns assembled by SBHS400, SBHS500, and SBHS700. The lower parts of the columns were locally heated up to 600 ℃ and 900 ℃ and rapidly cooled by water. After the heating experiments, the monotonic compressive loading experiments were performed. The elastic stiffness of the heated columns became lower than that of the sound column according to the magnitude of the out-of-plane deformation by the heating. The ultimate compressive strengths of the heated columns were reduced by the change in mechanical properties due to the heating over the A1 transformation point, regardless of the cooling methods.

This study presents an efficient methodology for estimating the mid-span deflection in simply supported bridges using slopes at end supports. The estimation is formulated through the correlation between the deflection and slopes, based on the Euler-Bernoulli beam under bending. Two methods are investigated: the first directly links the mid-span deflection and ends-of-span slopes, while the second accounts for uncertainties in boundary conditions by modifying supports with rotational elastic springs. Slopes are determined by extracting the quasi-static responses from accelerometer measurements through a robust signal-processing approach, and the practical feasibility was examined on a prestressed concrete bridge. Findings indicate that the end-slope-based method, considering rotational springs at the supports, estimated the mid-span deflection within 3–5% of the laser displacement measurements.

Currently, when analyzing steel bridges as a whole or in part, the member joints of gusset plates are ignored, and the members are connected in a very simple manner, such as pins or rigid connections. This study focused on gusset plates with twosided lap joints frictional connected by high-strength bolts. Through experiments applying compressive forces and detailed FE analysis, we investigated loadcarrying behaviors such as slippage and buckling. Additionally, we constructed a simplified analytical model using beam elements and nonlinear spring elements, which can be applied to whole structural analysis of bridges. As a result, the mechanical behavior of the gusset plate, such as sliding and buckling, was reproduced using beam elements and nonlinear springs.

A scissors-type bridge that applies a deployable scissors mechanism to its structural form has been developed to support emergency restorations after disasters. In previous studies, the fundamental static test was performed using the experimental pedestrian bridge, and its simplified calculation method was identified based on the beam approximation model. As a continuous study, the hammering test and numerical simulation were conducted to make clear the dynamic characteristics of the scissors-type bridges using experimental pedestrian bridge focusing on the deployment angles and boundary conditions. Then, we applied the beam approximation model to estimate the natural frequencies of the scissors-type bridge as well. The estimation results showed their validity and range of applications compared with experimental and numerical values to determine.

The extreme rainfall events occurring in recent years have been causing severe damage to social infrastructure and lifeline networks. To address these complex challenges, it is essential to conduct detailed and quantitative analysis of both the extent and causes of damage. This paper examines a specific case in which the Misasa River Bridge collapsed during flooding. Using computational fluid dynamics (CFD) methods, we evaluated the hydrodynamic loads and maximum flow velocities under extreme flood conditions. These hydrological parameters were then compared with values calculated through numerical simulations. Furthermore, we estimated the flood-induced forces acting on the bridge girders and clarified the mechanisms behind the pier collapse.

The number of bridges damaged by severe natural disasters is increasing, highlighting the need for rapidly deployable emergency bridges to restore traffic networks. The authors have studied a scissors-type emergency bridge with a deployable mechanism in its main structure. While previous reinforcement methods improved load capacity, they required manual installation on-site. This study proposes a novel foldable panel bridge with scissors mechanisms integrated into both the main frame and reinforcement members. This foldable system enhances stiffness and load capacity; and performance improvements were found to depend on the stiffness ratio between members.

The static cyclic test of the column specimen was conducted. To observe the behavior of the column of the arch bridge under the seismic excitation exceeding the design earthquake ground motion, the two-directional horizontal displacements and axial force were controlled based on the results of the dynamic analysis of the arch bridge system. The geometrical data of FE model of the test specimen, including the initial imperfection, were calculated by using its point cloud. Comparing the strain distribution measured by the digital image correlation (DIC) technique, it is confirmed that the FE analysis simulated not only the forcedisplacement relation but also the deformation of the test.

In this study, an analytical investigation is conducted on stiffened connecting plates, which are a type of bridge unseating prevention device, by directly cutting steel plates to stiffen the openings of the connecting plates. The accuracy of the analysis is validated by tensile failure experiments. Moreover, analyses are performed using models with different thickness and width for the stiffened part, aiming to propose its effective thickness and width. The results indicated that controlling the cross-sectional area ratio and thickness-to-width ratio is effective for identifying an optimal model.

Transverse loads caused by flooding may induce lateral displacement of bridge superstructures and damage bearing side blocks, leading to bridge washout. Such displacement generates shear forces and bending moments in long-connection type bolts through transverse loading on the side blocks. However, these bolts are not designed to resist transverse loads, and their load-bearing capacities and failure mechanisms have not been sufficiently clarified. In this study, loading tests were conducted on long-connection type bolts subjected to shear and combined shear and bending. The results show that larger edge distances increase the maximum load and result in thread shear–dominant behavior, whereas smaller edge distances enhance the influence of bending-induced tensile stresses.

For municipal governments with limited financial resources and personnel, achieving efficient and strategic maintenance is an urgent issue. In this study, we statistically analyzed the relationship between the results of periodic inspections of bridges in the Okhotsk region and the affecting factors, including weather and geographical data, and identified damage trends in materials and individual members that tend to be overlooked at the bridge level. As a result, we found a correlation between damage and some factors, and these results were consistent with the damage mechanism from inspection photos.

This study aims to present a decision-making framework that combines structural health monitoring data with expert opinions. Monitoring data are used to estimate hidden state variables which are utilized for time-dependent reliability analysis to primarily judge the structural safety. If a probability of failure exceeds the target probability, experts are deployed onsite for a secondary judgement. Qualitative visual inspection is modeled by a binary decision. Life-cycle cost including risk is calculated as a preliminary investigation on quantifying cost-effectiveness of this framework. A long-term tension monitoring of a cable-stayed bridge is used as an exploratory study to show an applicability of the proposed framework.

This paper analyses actual data such as exposure test results to develop a quantitative evaluation method for the durability of road bridges. The results of the inspections, which examined the deterioration of steel and concrete members, showed that deterioration rates can vary depending on factors such as design specifications, paint systems and environmental conditions. This suggests that the durability of road bridges can be evaluated quantitatively. The reliability of the current road bridge specification was evaluated based on the exposure test results for weathering steel and concrete cover. The S-N curve concept was demonstrated to be a useful method for evaluating the time taken to reach a durability performance limit state.

Scissors structure (SCI) are deployable mechanisms with cyclic symmetry and are used in a wide range of applications due to their excellent functionality and transportability. However, the stresses and displacements of SCI components tend to be large, and SCI must be designed to meet these constraints. The objective of this study is to derive the optimal topology of SCI, a deployable structure, through topology optimization using SCI-FEM. As an optimization method, the optimality criterion method (OC method), which is useful in homogenization and SIMP methods, is employed. In addition, the Simulated Annealing (SA) method is used to perform extensive searches when there are multiple minima in the objective function.

The mechanical properties of concrete in which gravel was partially bonded with mortar was examined. Two types of mortar with different water-to-cement ratios were used to prepare six concrete mixes with varying porosities. Uniaxial compression tests, splitting tensile tests, and triaxial compression tests were conducted. The results were compared with existing knowledge on porous concrete and granular geomaterials. It was found that the effect of mortar binding strength becomes relatively small in high-porosity concrete. In particular, within the range corresponding to porous concrete, the dominant deformation mechanism was not shear deformation of the material but rather shrinkage deformation caused by negative dilatancy due to the movement and rotation of gravel particles.

Methods for dynamic analysis of stainless steel rectangular water tanks have not been clearly established. Because bulging vibrations involve complex structurefluid interactions, their characteristics greatly depend on side plate shape, plate thickness, and reinforcement rigidity. In this paper, the effects of various analytical conditions on bulging vibration were examined using two finite element analysis software packages. The results obtained from both software agreed well with experimental results. Time history response analysis showed that the distribution of hydrodynamic pressure varies depending on the seismic input. Finally, key analysis conditions and important considerations for FEM of stainless steel rectangular water tanks are summarized.

This study investigated the extremely low cycle fatigue behavior of bellows-type expansion joints used in water pipe bridges subjected to large seismic displacements. Cyclic loading tests on single- and multi-convolution bellows revealed differences in failure modes and fatigue life under large-amplitude deformation. All specimens exhibited longer fatigue lives than those predicted by the fatigue curve adopted in existing design practice. Finite element analyses were conducted to clarify strain distribution and to support the interpretation of observed failure modes. Based on the experimental and analytical results, a design fatigue curve applicable to extremely low cycle fatigue conditions was proposed for the seismic design of bellows-type expansion joints.

For the cable-stayed bridge under consideration, a functionally separated bearing system is planned. Under conditions such as eccentric live-load application and seismic excitation, uplift forces are expected to develop at the bearing locations. Conventionally, counterweights (e.g., concrete blocks) have been installed to resist these uplift forces. However, this method increases the dead load, thereby amplifying the inertial forces during earthquakes, which poses a significant design challenge. Based on this, a bidirectionalsliding bearing equipped with an uplift resistance mechanism capable of maintaining sliding functionality even under uplift conditions has been proposed.

In recent years, ozone cracking has been reported in rubber bearings. This cracking is thought to occur in areas where surface strain on the rubber bearing is high. Few studies have examined the relationship between surface strain and cracking in rubber bearings in detail. Therefore, this study investigated the surface strain of rubber bearings in detail using image measurement while varying their shear deformation. The results showed that the distribution pattern of surface strain changes depending on the magnitude of shear deformation. Furthermore, accelerated ozone aging tests on rubber bearings indicated that cracks occurred in areas with high surface strain. These findings are expected to be useful for inspecting rubber bearings.

This study aimed to establish a quantitative evaluation method for the evaluation of ozone cracks in accordance with JIS K 6259-1. Natural and chloroprene rubber without antiozonants were exposed to ozone, and crack length, width, and depth were analyzed three-dimensionally using a laser microscope. Distinct differences in crack morphology were observed between the two rubbers. Crack propagation occurred in two stages: a proportional “single stage” of depth and length and a “linkage stage” where length increased rapidly. Crack depth shape changes were related to condition rank: higher ranks showed more pot-bottom-like and asymmetrical shapes. These results suggest that the JIS method, based only on crack number and length, may not sufficiently reflect crack severity.

Efficient maintenance methods are needed for aging bridge structures. Vibration-based structural health monitoring (SHM) is effective for managing infrastructures. To apply this technique to prestressed concrete (PC) structures, it is essential to understand how reduced prestress affects their vibration characteristics. This study conducted vibration experiments on four pre-tensioned PC girders with varying prestress levels and compared with finite element analysis. Both methods revealed that reducing the prestress did not significantly affect vibration characteristics without cracks. After the cracking load, the natural frequency decreased as crack developed. Suitable equipment should be chosen for the SHM system of PC structures considering these vibration characteristics.

This study investigates the development of snow accretion shapes on conductors by considering accretion rates dependent on the collision angle of snow particles, and evaluates their aerodynamic characteristics. Snow accretion experiments were conducted in a low-temperature wind tunnel to establish a model in which the accretion rate varies with collision angle. The rate can be conveniently approximated by a quadratic function, reaching its maximum when particles collide perpendicularly and decreasing to zero beyond a critical angle. Aerodynamic coefficients for conductors with estimated snow accretion reveal that, even with low accretion height, galloping is more pronounced during growth than with higher accretion—particularly under high Reynolds number conditions.

This paper presents the results of a feasibility study on a method for detecting abnormal vibrations excited in power-transmission cables, based on acceleration measurements of a steel tower. In this study, the acceleration responses of a steel tower were recorded over a period of 10 months on the Tsuruga experimental line, where galloping has previously been reported. Analysis of the time-series data reveals that several spectral peaks associated with the cable vibration modes appear below 1 Hz, but only during winter. The predominant frequency, damping ratio, and amplitude of these spectral peaks were quantified using the autoregressive (AR) method. Furthermore, numerical simulations were conducted to investigate the amplitudes of the acceleration responses observed in the tower body.

This study investigates the effect of spiral rod specifications on vortex-induced vibration (VIV) countermeasures through wind-tunnel tests, aiming to optimize the VIV countermeasure for steel tower members. Experimental results showed that applying two or more spiral rods with sufficient diameter was generally effective in suppressing VIV. However, its effectiveness was influenced by the helix angle of spiral rods. Therefore, VIV amplitudes of various members used in actual transmission towers were evaluated theoretically. The evaluation indicated that applying two or more spiral rods with a diameter equal to 0.08-0.13 times of the member diameter and a helix angle of 24.3-29.8˚ was effective in improving the fatigue life of various transmission tower members.

This study investigated the characteristics of the bulging pressure in a partitioned water tank through parametric analysis, and proposed a simplified method for estimating dynamic pressure caused by seismic excitation. Eigenmode and dynamic response analyses incorporating fluid structure interaction were conducted for various liquid levels and bulkhead thicknesses. The results indicate that the maximum dynamic pressure on each wall caused by seismic excitation can be estimated using bulging pressure modes together with the seismic response spectrum. Furthermore, comparison with detailed dynamic response analyses demonstrated that applying mode superposition in simplified estimation yields more accurate prediction of the maximum dynamic pressure.

Traditional vibration-based cable damage detection in cable-stayed bridges is limited by the need for prior modal identification, which is often inaccurate for higher modes. This study proposes two end-to-end Principal Component Analysis (PCA)-based methods—the Principal Component Eigenvector Correlation (PCEC) and Principal Component Curvature Difference (PCCD)—that directly process deck vibration signals, bypassing modal identification and enabling a full data-to-damage framework. PCEC quantifies damage severity, while PCCD accurately localizes it by capturing vibration changes induced by damage. Numerical analysis on a finite element bridge model demonstrates the proposed methods’ efficiency and accuracy for cable damage detection.

This study examined the mechanical characteristics of a ring girder structure, which has a circular arc-shaped planar shape and is composed of tension rings, compression rings, and beams (deck) connecting them. To understand the effects of tension ring position and stiffness on mechanical and vibration characteristics, static numerical analysis and time-history response analysis simulating walking vibration were conducted. The results showed that the displacement was smaller when the tension ring was located lower. In addition, it was shown that resonance occurs at the first and second natural frequencies in response to walking-induced vibrations, resulting in large response accelerations.

This report compares data measured by different vibration meters at the Musota Aqueduct Bridge, and examines a method for detecting anormal vibrations using the minimum number of measurement points necessary. Arch-type aqueduct bridges have natural frequencies and natural modes determined by the mass and stiffness of their structure. By placing vibration meters at appropriate locations, it is possible to confirm whether the vibration characteristics align with those of a healthy structure. The report demonstrates a comparison between the vibration characteristics of the bridge which exhibited abnormalities, and the repaired bridge. It also shows that even with a single inexpensive accelerometer using a moving measurement method, abnormalities in lower-order modes can be detected.

To evaluate the aerodynamic stability of motorcycles running over an empty road or long-span bridges subjected to strong crosswinds, accurate estimation of aerodynamic loads is required. Although widely used, motorcycles have received limited attention in wind stability research. This study employs wind tunnel experiments to evaluate wind effects on motorcycle stability. The six-component force coefficients of the motorcycle model were tested with the force balance equipment from various scenarios: Flat ground, differing wind barrier porosities, and varying upcoming wind speed via wooden panel setups. Different wind directions were analyzed to observe the changes of aerodynamic coefficients with wind direction. The results show that aerodynamic coefficients vary significantly with different incident angles, providing a more comprehensive understanding of motorcycle stability under strong wind.

By returning to the fundamental equations, we examined the relationship between the stiffness of the U-shaped frames at the cross-girder positions in a two-girder bridge and the lateral buckling of the compression flange. Holt’s method has traditionally been applied to determine the required stiffness of these U-shaped frames, but theoretical considerations in this paper and the results of analyses of an actual bridge model using a constant shear-flow panel elements have revealed that Holt’s method yields non-conservative results. Therefore, we propose a new evaluation formula that covers the range in which the Eurocode 3 design equations become non-conservative.

For the long bolted joints with filler plates in rusted contact surfaces, the nut rotation angles of turn-of-nut tightening method for the design of the joint are not proposed because the axial force induced into the bolts under those conditions have not been clarified. In order to clarify the induced axial force of the bolts, bolttightening tests of joints were carried out. Considering the influence of bolt length on induced axial forces and its relaxation obtained in the bolt-tightening tests, the nut rotation angles according to different bolt length were proposed.

In this study, the authors examined whether fatigue crack propagation inside box girders of steel railway bridges can be detected by measuring static strain without loading. Monitoring focused on cracks at the weld toe of the scallop in the cross ribs and at the welding between longitudinal and cross ribs. Monitoring results revealed that crack propagation can be evaluated by observing static strain changes. In addition, fatigue tests were conducted to investigate the tendency of static strain change by crack propagation at the welding between longitudinal and cross ribs. The results confirmed the reliability of crack evaluation through static strain monitoring.

In densely populated urban areas, work has begun to replace damaged slabs of each lane on oneway regions express-way. In such cases, joints of precast panels are set along the bridge axis direction, but until now, there is no appropriate method to evaluate the fatigue durability including these jointing parts. Therefore, the authors proposed a method to evaluate the fatigue durability by changing the combination of bending moments and shearing forces acting on slabs by change of the paths of vehicle wheels. And comparative tests were carried out for PC slabs without any joint and with the longitudinal Cotter Joints.

In this study, two different methods are used to construct finite element (FE) models of a damaged bridge. The first method involves converting the point cloud data of the entire structure into solid FE model. The second method converts only damaged part into solid elements, while the intact part is modeled based on the dimensions and then integrated with damaged part. This method significantly improves the efficiency of point cloud acquisition and processing. A comparison between the linear static analysis results of these two FE models and measured values from loading experiments showed that both models successfully captured the stress increases due to damage. Notably, the integrated FE model exhibited close agreement with the measured values at the location of the maximum stress.

Generally, stop-holes are installed as an emergency countermeasure against fatigue cracks, and patch plate repairs are performed as a permanent countermeasure. It has been clarified that the distributed axial force can be estimated by applying displacement compatibility conditions between high-strength bolts with fatigue cracks. However, it can only be applied within the elastic boundary conditions. In this study, the authors propose a method for estimating the shared axial force up to the yield condition of the main plate repaired by the stop-holes with patch plates using shear lag theory, considering axial force loss of high-strength bolts. Furthermore, the authors evaluate the validity of the proposed method by comparing it with FEM analysis results.

In this study, slip tests were conducted to evaluate the slip behavior of high - strength friction joints using environmentally conscious high -strength bolts (CEB). Four joint conditions were considered: rough surface, inorganic zinc coating, enlarged hole, and enlarged hole with bolt eccentricity. Comparative tests were performed using both the CEB and conventional high-strength hexagon bolts (HTB). As a result, the CEB showed slightly higher axial force relaxation and slightly lower slip coefficients compared to the HTB, but the differences were small, with a maximum of 4%. These findings confirm that the CEB provides slip performance equivalent to that of the HTB.

Following recent large-scale earthquakes, plastic deformation and buckling have been observed at the bearings of steel bridges. It is important to evaluate the vertical and horizontal load-carrying capacity after seismic events. In this study, in order to grasp the load-carrying capacity of the steel I-girder bridge, the load-displacement relationship caused by horizontal and live loads, and events occurring in bearings were investigated by using FE model. As a result, the damage events occurring in the members under each load were clearly identified. Furthermore, considering the point at which residual deformation increases sharply, the state in which the effective column section of all girder bearings undergo full-section yielding could potentially be defined as limit state 2 for each load direction.

In high-strength bolted friction joints, a diagram has been proposed to estimate slip resistance based on splice plate thickness reduction. However, considering the load transfer mechanism, the effect of corrosion varies with the bolt-row position. In particular, reduction around bolts in the outermost row, where corrosion tends to progress, is critical to investigate. This study investigates the relationship between plate reduction at each bolt row and slip resistance using finite element analysis. The results indicate that thickness reduction around the outermost bolts has only a minor effect on slip resistance, suggesting that the joint capacity is less sensitive to localized corrosion at these positions.

In this study, the effectiveness of ICR treatment on fatigue cracks in sole plate welding was evaluated. Fatigue tests were carried out on plate girder specimens with welding sole plates. For all specimens, fatigue cracks initiate from the weld root and propagate through the weld bead. The 11 mm long crack that appeared on the bead surface has almost been arrested by ICR treatment. For the 37 mm long crack on the weld bead surface, ICR treatment can also extend the fatigue life of the weld root crack. However, the root crack propagates within the weld bead of the sole plate. Additionally, it was found that the re-propagation of fatigue cracks closed by ICR treatment can be detected through static strain monitoring.

As bridges age, the need for maintenance and repair increases, highlighting the growing importance of structural integrity assessment. This study investigates the potential application of temperature-induced structural responses for assessing through truss bridge structural integrity by exploring the use of thermal input as a non-destructive and low-cost excitation signal. A finite element model was developed based on field data from an actual bridge, and case studies were conducted under thermal loading. These included simulations of internal force redistribution caused by heating individual members to identify key members that dominate structural responses, as well as comparisons between healthy and damaged structural states under localized joint damage. The results indicate that members close to the fixed support exhibiting dominant response patterns under thermal input.

The stair floor deck of the standard design pedestrian overpass is prone to corrosion due to stagnant water. In addition, the progression from corrosion to defect is faster than that of road bridge due to the thinner plates. In other words, an expected initial performance will degrade significantly by the progression of corrosion. In this study, a loading experiment was conducted using full size test body to evaluate the effect of corrosion loss on performances. As a result, the responses of the floor deck were quantitatively demonstrated using load-displacement relationships and strain states in relate to the position of corrosion loss and loading. Furthermore, the deflection limits are not met in some loading cases due to changing the boundary conditions by corrosion loss.

High strength stud bolts (Strength: equivalent F8T or SM570) are welded with the base plate using an arc and are used as frictional joints. It is an issue to determine the mechanical properties of the stud weld depend on the stud bolt or the base plate. Through element tests of the stud bolts, it was found that the mechanical property of the stud weld was determined by the stud bolt. Tensile test of frictional joints showed that the fracture position is the stud weld, and the shear strength of the weld is greater than the shear strength of the stud bolt. In addition, the weld collar has a significant effect on the shear fracture load of the stud weld.

Fatigue crack initiates at the boxing weld of load carrying cruciform joint of existing bridge member such as stiffener. Fatigue strength improvement by toe grinding is effective method for preventing fatigue crack initiation. This study investigated the effect of toe grinding on stress concentration reduction at the boxing weld by conducting FE analysis, and evaluated the effect of fatigue strength improvement of toe grinding by conducting cyclic loading test. These results indicated the fatigue strength improvement is achieved after grinding the boxing weld of load carrying cruciform joint.

Numerous fatigue cracks have been reported at welded joints between the deck plate and vertical stiffeners in orthotropic steel decks. This study investigates the influence of cut-out geometry, which is commonly adopted as a fatigue countermeasure, on stress reduction at these welded joints. Furthermore, a simplified method for estimating the stress reduction effect at the wrap-around welds of vertical stiffeners is proposed using a beam model. In addition, regression curves are proposed to estimate the stresses at the scallops and at the curved edges of the cut-outs using the dimensions of the vertical stiffeners, deck plate, and cut-outs.

Root-deck cracks, initiating from the welds between the deck plate and closed ribs, have been observed in orthotropic steel deck (OSD) bridges under severe traffic. In the authors’ previous study, their propagation behavior was examined through fatigue tests on scallop-detailed specimens simulating the weld root and adjacent details under varying load ranges. In the present study, fatigue tests were conducted under low load ranges on both scallop- and non-scallop-detailed specimens, and fatigue strength was evaluated using effective notch stress to examine the potential for a unified fatigue strength curve. Furthermore, FEA, incorporating a fracture mechanics approach, was performed to simulate crack propagation and investigate the influence of tensile residual stress on the behavior.

Many reports have suggested that failure of corner welds in steel bridge piers during large earthquakes is due to fracture of the corner welds containing unwelded sections. In this report, we clarified the specifications of the corner welds of existing steel bridge piers and conducted low-cycle fatigue tests to clarify their fracture behavior. As a result, we found a relationship between the strain at the fillet weld root and the throat area ratio. We also proposed a design fatigue strength curve for corner welds.

The authors have proposed the use of high strength threaded studs (hereafter, stud bolts) in friction joints of steel plate-concrete composite decks. It has been revealed that friction joints with stud bolts have sufficient static strength. However, there are few studies focusing on its fatigue durability. In this study, we have confirmed the fatigue durability of steel plate-concrete composite deck using friction joints with stud bolts through the wheel running fatigue test. As a result, no significant damage to the stud bolts was found at the time the wheel running fatigue test was completed. This indicated that this joint structure had sufficient fatigue durability.

Methods for calculating the shear strength of RC deep beams have been proposed since the 1980s; however, the mechanism of strength enhancement by compression struts has not been fully clarified. This study visualizes the failure process of RC deep beams using Digital Image Correlation (DIC) to examine strain distributions associated with compression struts. The results indicate that failure related to compression struts exhibits characteristics similar to concrete failure under compressive stress, particularly splitting failure. Furthermore, failure processes of RC deep beams with a/d ratios of 1.0 or less are classified into three types: rapid diagonal cracking, tied-arch-type failure, and failure governed by stress transfer along compression struts.

In this study, four-point bending tests were conducted on reinforced concrete (RC) beams with non-contact lap splices in the main rebars to investigate the effect of transverse rebars spacing on joint performance. The non-contact lap splices were located in the equi-bending moment region with main rebar spacings equal to five times the diameter of the main bars. Three kinds of transverse rebars spacings and a case without transverse rebars were examined. The results show that transverse rebars can improve the load-carrying capacity of RC beams with noncontact lap splices. However, it confirmed that when the transverse rebars spacing exceeds the main rebars spacing in a non-contact lap splice joint, the performance improvement is limited. In addition, the effective anchorage length can be conservatively estimated as the basic anchorage length minus the main rebars spacing.

This study presents a fundamental investigation toward quantitative nondestructive testing for steel bars in concrete, based on elastic waves. The propagation characteristics of leaky guided waves in a steel bar embedded in concrete were analyzed using the semi-analytical finite element (SAFE) analysis. The SAFE formulation was conducted in cylindrical coordinates, incorporating the radiation condition of the surrounding concrete. The dispersion curve showed that the energy velocity of the longitudinal (L) mode increases with frequency and asymptotically approaches the bulk L-wave velocity of steel. While the L-mode waves in embedded bars exhibited attenuation due to leakage into the concrete, higher-frequency components showed less attenuation compared with lower frequencies.

This study proposes a non-destructive method for damage assessment of reinforced concrete (RC) beams by combining transfer learning with an ensemble Local Outlier Factor (LOF) approach．A selective transfer strategy was introduced to address domain mismatch between source and target data, while Bagging－based ensemble LOF was applied to improve accuracy and stability under small－data conditions．The results indicate that integrating transfer learning with ensemble methods provides a robust and reliable framework for RC beam damage assessment．