The stainless steels have higher corrosion resistance than the carbon mild steels. Therefore, the stainless steel structures are able to reduce their life cycle cost. In this study, the compressive and bending strength behavior of steel member made of stainless steel at both ends are clarified by numerical analysis. First, the influence of the change of the ratio of stainless steel at both ends for the entire member on the strength behaviors was investigated. The strength behaviors of these hybrid members are compared with the ones made of carbon steel. Finally, this paper proposed the strength evaluation method by comparing present design curves in several design standards.

In this paper, the optimal cross-section shape and the ultimate strength of longitudinally stiffened aluminum alloy plates in bending are investigated. First, the optimal cross-section shape to maximize the buckling strength of longitudinally stiffened aluminum alloy plates in bending is provided. Next, the elastic-plastic large deflection analysis with FEM clarifies the ultimate strength of those plates, followed by the equation to estimate it. The aluminum alloy considered is the heat treated aluminum alloy A6061-T6.

This paper deals with the collapse mechanisms of steel columns with variable cross-section subjected to the cyclic bending under alternating axial force. The second order rigid plastic and elasto-plastic analyses of columns with rotational restraint at both ends are carried out by using the rigid body - rotational spring models. Numerical results demonstrate that the collapse mechanisms in columns might vary every half cycle due mainly to the plastic deformation in the middle of columns and corresponding PΔ effect. Then the instability region S of collapse mechanisms develops severely by the variation of axial force. A conventional method on the basis of rigid plastic approach is proposed to predict the instability transition region S in columns with variable cross-section.

The authors devised a double-square joint (referred to as DS joint) as a bar joint structure capable of avoiding the bar interference when precast beams are installed, and reducing the joint width between the precast beams. For DS joint, U-shaped bars are protruded from the end surface of the precast beams. After setting those U-shaped bars abutted, square shaped bars are inserted to overlap and form a joint with the U-shaped bars. In this study, bending load test of the precast beam with the DS joint was carried out, and the flexural capacity and crack behavior of the DS joint structure were clarified. Furthermore, FEM analysis was conducted and the flexural capacity mechanism of the DS joint composed of closed bar shape was discussed.

Unsupported sleepers cause various problems in track management. Although authors have developed a method for detecting them accurately composed of a 2D FEM model in which track longitudinal irregularity data and track specifications are used, there was a problem in that the model requires great effort setting the strict track condition of commercial lines for its practical application. Therefore, we examined the effect of track specifications’ variation on the calculation of unsupported sleepers, and confirmed that the effect of the detection accuracy of unsupported sleepers is small. Then, we built a calculation method of detecting unsupported sleepers more easily for practical work, confirmed its accuracy, and proposed its proper usage.

Corrosion leads to thickness reduction and surface roughness on steel plates. Under loading, the roughness may cause high stress concentration, non-uniform yielding, and strain localization leading to a reduction in ductility. In this study, thickness data obtained from corroded steel pipe piles, which had been exposed to the marine environment for 19.5 years, were used to construct finite element (FE) models of corroded tensile test coupons. Elastoplastic nonlinear large deformation analysis was conducted on these coupons subjected to static monotonic tension using a general purpose FE analysis software. In addition, different surface roughness parameters of the corroded coupons were determined as specified in ISO 25178-2. Static ductility was found to decrease as surface height roughness parameters increased as a result of stress concentration and strain localization.

This paper discusses remaining capacity of compressive box-section members with artificial section loss area, which were cut out from an actual truss bridge and tested in authors’ previous study. FE analyses of 7 test specimens were conducted by solid element models with consideration of initial imperfection in order to clarify the effect of the section loss on the elasto-plastic behaviors through comparison between experimental findings and analytical results. Also, parametric FE analyses were carried out to obtain the relation between section loss and decrease of compressive strength. As the results, elasto-plastic behaviors were almost properly evaluated by analytical model, and effects of section loss on the compressive strength were assessed by analytical results.

In this study, the corrosion damage investigation and field loading test of a pratt truss bridge which was constructed 97 years ago were carried out for clarifying the acting live-load stress of main structure members and deflection behaviors. The maximum reduction rate of cross-section area was confirmed in the joint part between sway bracing and the vertical member. From the consideration of current traffic restriction, 2 dump trucks with 80kN weight used as loading condition. As the test results, the acting compressive force of vertical member with severest corrosion damage was estimated about 1/3 of buckling load. Also, it could not confirm the serious effects due to corrosion damages and repairs to load bearing capacity under current traffic restriction.

This paper shows the revise of the equations and the evaluation of the accuracy to estimate the axial bearing capacities of piles. Firstly, the estimation equations on the axial bearing capacities of piles are improved by analysis of pile load test results. Secondly, the ratio of the axial bearing capacities estimated by improved the equations to actual values are compared with the one estimated by the former equations. Finally, the accuracy to estimate the axial bearing capacities of piles by improved the estimation equations are evaluated.

In this study, the practical replacement strategies of the existing steel flap gate used for more than 30 years was considered. A steel flap gate consists of three main members of steel gate panel, hydraulic cylinders, and hydraulic controllers. The deterioration prediction of steel gate panel was predicted from the result of the weathering test for 2 years at the existing steel flap gate. The prediction equation of the replacement probability in future of hydraulic cylinder and hydraulic controllers was calculated from results which analyzed replacement history statistically. And, the reduction of the replacement total cost of the existing steel flap gate was confirmed by some simulations of practical replacement strategies.

In the maintenance of existing bridges, a bridge life-extending repair plan has been formulated. Recent years, the importance of risk management has been recognized in view of severe damage due to natural hazards. Natural hazards cause serious disruption to societies and their transport infrastructure network. Therefore, it is necessary to formulate the life-extending repair plan considering connectivity of road network. In this study, an effective maintenance plan of the bridges is simulated in consideration of the connectivity of the network by the increased risk of damage at the time of disaster due to deterioration of the bridges. Simulation results show it is possible to formulate a life-extending repair plan that can secure a more robust network with leveling the annual repair cost.

Due to their wide applicability in inspection of concrete structures, there is considerable interest in the development of automated crack detection method by image processing. However, the accuracy of existing methods tends to be influenced by the existence of traces of tie-rod holes and formworks. In order to reduce these influences, this paper propose a crack detection method based on semantic segmentation by deep learning. The accuracy of developed method is investigated by the photos of concrete structures with lots of adverse conditions including shadow and dirt, and it is found that not only the crack region could be detected but also the trace of tie-rod holes and formworks could be removed from the detection result with high accuracy.

Strengthened methods supported by aramid sheet together with resin layer are recently separated two types, so-called type T and type S, the former is treated as isotropy and the latter is guessed as anisotropy with structural particularities. In this paper displacements and stresses in damaged RC slab strengthened by these types are individually calculated. From comparison of strengthened effect per a layer yielded by linear regression about elastic deflection of slab, equivalent number of layer in type S is determined to type T. Next residual life of type T given from wheel running tests and assumed residual life of type S are respectively discussed in consideration of strengthened effect. It is confirmed that type T is superior to type S regarding magnitude of recoverable deflection and length of residual life.

In order to carry out rapid reconnaissance of the structure after strong earthquake, quick investigation of the distribution of the earthquake intensity is indispensable. It could be realized by high density measurement system, however, only a few has been applied to the real structures in terms of long-term reliability, cost, and stable power supply. To this end, this paper proposed the simple and economical physical gadget to detect whether the induced acceleration exceeded predetermined level or not. A prototype of the device was manufactured and tested using a shaking table. It was confirmed that the device successfully worked if the subjected acceleration to the device exceeds the predetermined level estimated from the simple identification test.

When planning to construct structures, it is desirable to select an area not to be affected by fault induced permanent ground deformations. But there are inevitable cases with railway structures, so it is necessary to consider the effect of fault induced permanent ground deformations on the structural behavior. Therefore, in this paper, the difference of the growing process of the shear zone with and without foundation was investigated through scaled static experiment. In the test, bottom of the layered sand was partially dislocated using a hydraulic jack to simulate a dip slip fault. As a result, it was found that the shear zone tends to grow up to the ground surface while avoiding the foundation.

The authors propose foundation composed of micropiles and soilbags as a new foundation type. The foundation is characterized by laying soilbags on the pile head and constructing structures on the soilbags. The expected effects are omitting junction structures of piles and footing, reducing diameter of piles, and reducing response acceleration of structures. In this study, shaking table tests and their reproduction analysis targeting piers on the supporting ground, on the micropiles, and on the proposed foundation were conducted. The tests and analysis results showed that bearing capacity of proposed foundation was almost equivalent to that of supporting ground, and that the bending moments of micropiles were suppressed by laying soilbags on the micropiles.

This paper presents an experimental and analytical study on the behavior of a bridge superstructure with double spherical sliding bearings subjected to live load. Two single span superstructure models with an I-section beam supported by two spherical sliding bearings were tested under static loadings to investigate the influence of live loads to the double spherical sliding bearings, and the experiments were simulated by 2D finite element analyses. It is found that a slider of the bearing tends to be returned to the stable positon without residual displacement after the cycle of loadings. Also, the finite element analyses show that there could be a stress concentration to the slider due to the rotation and displacement of the bearing.

Dampers are useful for bridges to reduce structural response by their energy absorption. It is important that excessive seismic response is not developed even if bridges are subjected to severe ground motions. Seismic response characteristics of bridges with hysteretic dampers between the abutment and the deck subjected to severe ground motions were investigated. It was shown that the summation of the yield seismic coefficients of the bridge columns and dampers is an important parameter to reduce excessive seismic response under severe ground motions.

Elasto-plastic large deflection static/dynamic analysis using beam elements is one of the most practical, yet reliable tools in stability/seismic design of steel structures. This analysis cannot take into account local buckling; however, member flexural bucking can be incorporated into the analysis if adequate analytical models are used for the bracing members. This paper deals with an in-depth study on exploring a rational analytical model for bracing members under cyclic loadings. As a result, the Initial Lateral Load Method (ILLM) proposed in the previous study is proved to be the most reliable as well as practical method.

In the seismic upgrading design of existing steel arch bridges if it is difficult to prevent damages to the secondary members such as braces, bridges are designed allowing damages to the secondary members while ensuring the safety of the structure. In such a case, it is important to accurately predict the behavior in the post-peak regions of the secondary members in the seismic response analysis. In this study, the applicability of an analytical model that can accurately and easily predict the post-peak behavior of the secondary members is discussed. As a result, the post-peak behavior of the secondary members could be accurately predicted by the numerical model investigated, if the effective slenderness ratio of the secondary members is appropriately evaluated.

The coupling effect of bendig moments and shear forces on the materially nonlinear behavior of the Timoshenko beam model is usually ignored in the conventional seismic analysis. This paper invetigate the validity and accuracy of ignoring the above coupling effects. As the result of this investigation, it is revealed that there exist cases in actural structures where the coupling effect considerably reduces the strength and ductility of structures. In these cases, the coupling effect have to be inevitably considered. Therefore, the corresponding cases are demonstrated in terms of structural parameter ranges. The validity of the above parameter range is examined by the time history response analysis on elevated-girder bridge model under bi-directional seismic accelerations.

This paper discusses the effects of local deformation, dent, of a line pipe. Bending tests were conducted using one normal pipe and two dented pipes with an outside diameter of 200mm. One dented pipe was bent in the direction that the dent was caved inside the pipe, another was bent in the direction that was parallel with the surface of the dent. All pipe were not broken. A series of finite element analyses were conducted to investigate the bending behaviors. Two kind of analyses were conducted, one was considering only the dent shape, another was considering the dent shape and the residual strain. The analysis considering the dent shape and the residual strain could reproduce the result of bending tests.

The plastic hinge length is one of the important factors to evaluate the ductility of reinforced concrete columns that fail in flexure at the bottom by seismic load. This paper presents the analytical studies on buckling of longitudinal reinforcement in jacketed columns through FEM analyses and compares with the result of jacketed column loading tests. In the analyses, the effects of resistance of cover concrete wrapped by carbon fiber sheet or steel plate against buckling are examained. Furthermore, the simplified procedure to evaluate the plastic hinge length of jacketed reinforced concrete columns is proposed based on the analytical studies on the buckling of longitudinal reinforcement with taking account of the inelastic behavior.

We proposed a nondestructive testing method based on a visualization technique of the dynamic motion in a target structural component. The motions were excited by hammering at multiple points, and received at a fixed position. Using the reciprocity theorem in elastodynamic problems, we visualized the dynamic motion of the structural component. In the visualization, the significant deformation was observed when a wall thinning part was located just at the position of an antinode in a bending vibration mode. Therefore, the use of the guided wave of bending mode was applied to the detection of wall thinning at unknown locations. By choosing an appropriate guided wave mode, it was shown that the location of the wall thinning can be evaluated successfully.

This paper introduces the details of a transient damping feature extracting method based on the bridge monitoring data with the aid of the frequency slice wavelet transform (FSWT) which is a time-frequency space analysis tool and its application to damage detection of the bridges. The proposed method via the state representation methodology (SRM) algorithm has been verified by the state probably distribution using the vibration signal from a laboratory bridge monitoring system. As a result, the system state vector as a non-parametric state variable will be able to apply to assess the state change (damage) of the bridge structures by expression of the state probably distribution.

As a method of detecting bridge damages at low cost, the applicability of VRA (Vehicle Response Analysis) based on SSMA (Spatial Singular Mode Angle) has been examined. The previous studies for SSMA-based method numerically and experimentally shows that SSMA is a sensitive index for serious damages. However, for practical application of this technology, it is necessary to detect not only serious but also relatively mild damages. In this study, to examine the applicability of SSMA-based method to the detection of mild damages, an actual sensor-equipped car travels on a steel girder bridge. Bolts are loosened, and a lateral girder is removed as the damage models. As the result of this experiment, it is found that both damages can be detected by the Maharanobis distance of SSMA.

If the running speed of the vehicle further increases in the future, the ground vibration propagating to the surroundings may increase. In this study, we focused on the floating slab track as a countermeasure against ground vibration and evaluated the dynamic response at 400 km/h by numerical analysis. Moreover, we carried out the vibration test for full-scale track model and confirmed that the floating slab track showed high reduction effect of ground vibration.

In order to develop a simple estimation method for the bulging frequency of a rectangular water storage tank with inner members, shaking tests with scaled stainless steel tank models were carried out, and the results were compared to those calculated. The influence of inner members, such as, reinforcement column and horizontal beam on the bulging behavior was evaluated from the experimental results. Subsequently, the frequencies obtained from experiment were compared with those estimated by classical energy method and FE analysis. As a conclusion, it was indicated that the appropriate assumption of vibration mode and the use of equivalent stiffness for tank wall enables to estimate simply the bulging frequency.

This paper presents the results of a real bridge field experiment, carried out on a glass fiber reinforced polymer (GFRP) pedestrian truss bridge of which nodes are reinforced with stainless steel plates. The aim of this paper is to identify the modal properties of this bridge by using both conventional techniques and a model updating algorithm. Pedestrian-induced vibrations are also measured and utilized to identify modal properties of the bridge. A stochastic subspace identification combined with stabilization diagram was utilized to identify modal properties of the bridge. Moreover, an FE model capable of reproducing experimental results was constructed using the cross-entropy method.

Aerodynamic forces acting on railway vehicles depend not only on the shapes of the vehicles but also on the types of infrastructures. In this study, the railway vehicle is simplified as a finite-length square cylinder. Large-eddy simulations (LES) of the flow around the finite-length square cylinder, namely, the simplified railway vehicle on a flat ground, embankment, and viaducts simplified as rectangular cylinders, were conducted at 40°, 50°, 60°, and 90° yaw angles. The velocity field around the finite-length square cylinder on flat ground was also measured using particle image velocimetry to validate the LES results. The side force coefficients of the train model on the thick viaducts were large, and the effect of the viaduct on the flow field was thus revealed.

In this study, the wind stability of multi-span suspension bridge with center span length of 3000 m was verified. In order to stabilize the wind performance, two cross stays were installed in the main span of the bridge, and static analysis was performed by the wind load. As a result of the multi-mode flutter analysis, flutter wind speed of the bridge were 51 m/sec. Then, cross stays were most effective when installed at 675 m from the center of the main span, and flutter wind speed increased up to 67 m/sec. Furthermore, cross stays did not yield and was not unstable under the flutter wind speed.

Recently inconvenience on the community due to infrastructure construction are required to minimize as much as possible. In order to construct temporary bridges quickly, we are considering using the high strength bolted tensile joint with multiple bolt lines. In the bolted tensile joint, it is desirable that the joint surface is flat and completely adhered by the load transmission mechanism. However, since it is a prerequisite to reuse a member of temporary bridges as temporary structures, there is concern that the joint surface may be deformed by repeated use. In this study, the influence of the faying surface conditions and the behavior when filler plates were inserted on the tensile joint was examined with experiment and finite element analysis.

This study focuses on influence of the number of bolt rows of specimen in tensile experiment of high strength bolted frictional joint. Difference of constraint condition on side surface of the joint according to the number might affect to mechanical behavior such as slip and yield of the joint. FEM analysis has been carried out to evaluate the influence in these behaviors. Slip and yield load of single bolt row joint are almost same or smaller than those of a row of multi bolt row joint. This fact suggests that the result obtained by a specimen with single bolt row might be lower load and gives safety evaluation. This paper also indicates the mechanism causes the difference of the loads.

Repair using high strength bolted steel plates is often performed due to cross section loss by corrosion. However, the mechanism of load transfer of base plate and patch plate is not obvious enough. In this study, the tensile tests were conducted in order to clarify the slipping behavior in the patch plate repair part. The effect of the number of bolts, thickness of patch plate, bolt axial force and slipping coefficient on the slipping behavior of the part of patch plate were investigated. It was confirmed that the slipping behavior occurs after yield of corrosion section or outermost bolt position. Moreover, the slipping behavior was classified as yield-leading type of net section and yield-leading type of corrosion section.

In recent, the deterioration of RC slabs of the steel girder bridges has been increased. It is supposed that these updating is necessary in the future. The cast iron deck was developed as lightweight and highly fatigue resistant deck slab. The mechanical connections between these modules are inevitable because the cast iron deck is composed of multiple modules due to manufacturing limitations. In this study, high strength bolted tensile joint is applied to improve constructability by FEM analysis. It is confirmed that the tensile joint could be used at the connections between the cast iron deck modules, and the load transferring mechanism of this connection is clarified.

The authors are investigating the joint structure that can be applied only from the upper surface of the composite deck using high strength stud bolt. However, it’s supposed that the slip resistance decrease due to the deformation at the time of stud welding or application of axial force to high strength stud bolt because of the small thickness of steel plate. In this study, the tightening performance, deformation of the steel plate and slip resistance of the friction joint using high strength stud bolt on thin plate are studied by experiments and FEM. As a result, it was found that the axial force to the high strength stud bolt should be restricted. Also, the behavior at tensile loading didn’t differ from the case with large plate thickness.

In reinforcing the patch plates to the damaged member of the bridge, Single-sided construction is desired in some cases. The high-strength stud bolt welds the bolt directly to the plate, enabling single-sided construction. However, there are only a few examples of one side frictional joints with high strength stud bolts, and it is desirable to accumulate data of them. We conduct slip test of one side frictional joints with high strength bolts (F8T) and high strength stud bolts (S8T), and compare and examine their mechanical behavior. As a result of the slip test, their slip coefficient was 0.4 or more. The same tendency as the slip behavior of one side frictional joints with high strength bolts (F8T) was seen.

The bearing section of steel railway bridge is a critical point of maintenance. When exchanging a bearing, it is usually replaced with the original form of bearing. In this paper, we examined “replacement bearing”. The structure of the replacement bearing is based on BP-B bearing. Bearings are generally cast, but in replacement bearings they are made of steel. This time, we used this bearing at the actual bridge and measured the behavior of the bearing part. Furthermore, we carried out a loading test and grasped the friction coefficient etc.

This paper sets forth a influence exerted by cable creep on change in the status of small-scale suspension bridges. It also presents methodology for action to repair the configuration in the event of deformation. Furthermore, it obtained the conclusion that it is possible to estimate the amount of creep strain from the configuration of the road surface based on data acquired from the results of periodic checking.

The main girders in a steel I girder bridge are connected with the slab, the sway bracing and the cross frame behaving together as a system. Therefore, if a single part of one main girder is corroded, the remaining healthy main girders are supposed to compensate it. In this study, the bridge loading capacity was evaluated using an FEM model of the bridge system assuming one of the girders is corroded. As result, it was observed that in case one of the girders in a multi-girder bridge system is corroded, the remaining healthy main girders compensate it, confirming the bridge system redundancy.

As for steel bridges, corrosion of girder ends is one of the major damage for reducing the load carrying capacity. This research focuses on proposing a simplified approach for evaluating remaining bearing capacity of steel plate girder end with section loss due to corrosion. Laser surface measurement of corrosion depth and compressive loading test were conducted for a girder end specimen which were cut out from a demolished 90-year-old steel railroad bridge in order to investigate the influence of the section loss on the remaining capacity. Also parametric finite element analyses for remaining capacity of girder end were carried out considering typical section loss patterns with various depth and discussed a practical method for estimating remaining capacity.

Corrosion damage is often found at the steel girder end, which leads to a decrease in load carrying capacity. This paper investigates the performance recovery mechanism of the corroded steel girder end with patch plates fastened by high strength bolts through numerical analysis. Firstly, the residual loading capacity of steel girder end with corrosion at the web or vertical stiffeners is evaluated for different corrosion levels and compared to that of intact steel girder end. Secondly, the performance recovery effect and failure mode of corroded steel girder end repaired by patch plates are examined. Moreover, this study investigates the influence of difference in the patch plate shapes on the performance recovery by the patch plate repair.

It is important to accurately evaluate the corrosive environment of steel bridges for corrosion prevention and maintenance. In the last couple of years, an evaluation of the dew condensation was carried out using weather research and forecasting (WRF) and inverse distance weighting (IDW) techniques. In this study, an accuracy enhancement of IDW for different land topographies and its employment was discussed to achieve more accurate results. Thus, a quantitatively investigation was conducted, and it was found that IDW yields accurate results, particularly for flat land with regard to the temperature and humidity. Additionally, appropriate adaption points selection of IDW was discussed, as a results the optimum number of interpolation points for evaluation of a corrosive environment was proposed.

Though most of buckle plate girders for steel railway bridges have been in existence for about a century since their constructions, it is often preferable to prolong their lives considering such as their narrow construction space. Some situations exist where cracks generate in buckle plates. The conventional repairing method for this crack has problems in terms of its workability and economy. In this study, first of all, the load-bearing characteristics of a buckle plate with crack of some length were clarified by the laboratory load test and the FE analysis. Next, based on the result, the simple repairing method against the crack was developed and its effect was verified.

A target bridge in this study whose floor beam is jointed to the main structure only with web angle has fatigue cracks at the end of welded joint between the upper flange and the web of the floor beam. Therefore, field test was carried out to clarify the cause of these fatigue cracks. It is found that fatigue cracks are occurred by local out-of-plane bending at web gap. Futhermore, FE analysis was conducted to examine the effective repair methods. Analytical results show maximum stress range of the welding toe is reduced by cutting the upper flange or applying it to the web gap.

Impact crack closure retrofit (ICR) treatment has been proved to be effective to repair small cracks initiated from weld toe. High compressive residual stress induced by peening near the weld toe attributes to it. In this study simplified ICR treatment using an automatic center punch (ACP) with rounded tip is proposed. ACP is commercially available hand-tool, so that treatment can be carried out even during inspection. Compressive residual stress induced by ACP was about a half of that due to ICR treatment, yet fatigue tests showed that fatigue life was prolonged for cracked and as-welded specimens. Proposed technique was applied to fatigue crack at upper end of vertical stiffener, and stress measurements showed the similar effect as one due to ICR treatment.

For the countermeasure technique of fatigue crack on the weld bead between orthotropic steel deck and U-shaped rib, it was proposed to use high-strength stud-bolts as the connection between steel deck and U-shaped rib. In this paper, fatigue strength of high-strength stud-bolt with patch plate under bending was investigated. The high-strength stud-bolt of M20 with the bolt tension of 100kN was used. As the results of bending fatigue test, it was found that the fatigue life of stud-bolt with patch plate is extremely longer than that of the stud-bolt without patch plate. Furthermore, it was revealed the crack depth of specimen with patch plate is lower than that without patch plate.

One of the typical fatigue cracks in orthotropic steel deck is observed at the top end of vertical stiffener. This study investigates the repair and retrofit for those fatigue cracking with the newly developed method with L-shaped splice plate. The main characteristics of this method are followings: (1) bearing type bolt is used for lifting up L-shaped splice plate, (2) detail of L-shape splice plate itself is modified to facilitate the maintenance process and also to gurantee the effectiveness of this application. This paper reports the results of static test, filed test and fatigue tests conducted for evaluating the applicability of the proposed method.

In this study, the impact loading test was carried out at the highway bridge. By comparing with static loading test results, the application to the degradation degree evaluation of the bridge slab was investigated. As a result, deterioration was not observed in this slab in any method. In application to degradation degree evaluation, it became clear that it is important to consider the difference from the static action taking into consideration that the impact test is a dynamic action. Also, when assessing the degree of deterioration with curvature, it was shown that care should be taken in evaluating the Young's modulus value in a relatively healthy bridge slab.

In this research, mechanism of generating microcracks in upper surface of concrete was investigated by experiments and numerical simulations. Based on the past researches, the authors assumed that generation of microcracks was promoted by waterproofing layer. As the results, it was found that microcracks were generated when moisture content of concrete is relatively high. Using waterproofing layer with permiable type primer, securing sufficient air content in concrete or polishing on upper surface of concerte were effective on mitigating microcracks. Furthermore, these cracks could be occurred only when thermal stress is increased in concrete, and vapor pressure is increased in micro pores, simulatenously.