Vol. 6, No. 1, Division E (Materials, Concrete Structures and Pavements), Journal of JSCE (in English)
Vol. 73, No. 4, Division E2 (Materials and Concrete Structures), Journal of JSCE (in Japanese)
Vol. 74, No. 1, Division E2 (Materials and Concrete Structures), Journal of JSCE (in Japanese)
Vol. 74, No. 2, Division E2 (Materials and Concrete Structures), Journal of JSCE (in Japanese)
Vol. 74, No. 3, Division E2 (Materials and Concrete Structures), Journal of JSCE (in Japanese)
J-Stage (Journal of JSCE in Engish)
J-Stage (Journal of JSCE (E2 Division) in Japanese)
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Tsuyoshi MATSUMOTO, Tatsuo MUKOYAMA, Eiji YONEZAWA, Takefumi YAMAZAKI, Takayuki FUJITA
Vol. 6, No. 1, pp. 49-68, Journal of JSCE (in English)
Abstract:
The Suez Canal Bridge was constructed through a grant aid from Japan and completed in September 2001. Stone Mastic Asphalt pavement (SMA) was adopted over the orthotropic steel deck of this bridge because SMA was utilized for the orthotropic steel deck in Japan and SMA did not need any special machines, which were indispensable for the Gussasphalt Pavement ((nonporous) mastic asphalt pavement) and were unavailable in Egypt. After the bridge opening, however, hair cracks on pavement began to appear from June 2002 due to overloading of vehicles whose axle weights sometimes exceeded 25t. Upon advice from Japan, the General Authority for Roads, Bridges and Land Transport (GARBLT) limited the axle weight of vehicles to 13t. In September 2003, after inspection of the bridge, the bridge was handed over to Egypt. In 2011, a study team from Japan International Cooperation Agency (JICA) was dispatched to investigate the condition of the pavement and the steel deck. Although the pavements were heavily cracked, no fatigue cracks on the orthotropic steel deck were found. The steel deck surfaces were investigated and rusts were confirmed. The thickness reduction was measured. The average largest thickness reduction was 0.5mm. As seepage water was confirmed on the steel deck, 20 water monitors were embedded. The team recommended the repavement using the Gussasphalt Method as it was practically the only one method applicable at present in Japan. In 2016, GARBLT decided to repave the bridge using its own method and actually repaved the bridge. JICA experts could not give any advice because there were no related experiences in Japan. However, this pavement was deemed viable. Before the repavement, the water monitors were checked and seepage water was confirmed. After the removal of the pavement, all of the steel deck surfaces were investigated.
Takuya KONDO, Takashi YAMAMOTO, Toyoaki MIYAGAWA, Yusuke SUZUKI
Vol. 73, No. 4, pp. 348-362, Journal of JSCE (Division E2) (in Japanese)
Abstract:
This paper is descraibed the occurrence tendency of cracks by corrosion of the PC sheath arranged in the PC structures. To investigate these, an experiment by electrically corrosion and numerical analysis by an FEM were performed.
It is found that insufficiently grouted influences a crack of a PC by corrosion of a steel sheath. Therefore the consideration which imitated the insufficiently grouted situations assumed by existing structures was performed.
It was proposed that insufficiently grouted investigation method in the PC structure which occurred due to corrosion of a steel sheath based on an obtained result.
Koji YUASA, Hidenori MORIKAWA, Keisuke FUKUTA
Vol. 73, No. 4, pp. 363-379, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Strengthening by external cables is often used in case it is necessary to recover or improve the load-carrying capacity of prestressed concrete girder. However, in the case of PC-I girder bridges with the narrow distance between adjacent main girders, the conventional anchorage units for external cables cannot be applied. Therefore, the authors proposed and developing a new anchorage unit.
In this paper, loading tests were conducted to evaluate load-bearing mechanism and performance of the proposed anchorage unit. As a result of the tests, it was found that the anchorage unit showed small slip behavior at the interface between new and old concrete and rotating behavior before maximum loads and had large load-carrying capacity due to constraint effect. Also, the effects of the normal stress or the condition of interface or transverse girder on load-carrying capacity ware evaluated.
Kotaro DOI, Maya YAMADA, Yoshinao HOSHI, Isao SHITANDA, Hideki KATAYAMA, Masayuki ITAGAKI
Vol. 74, No. 1, pp. 1-9, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Corrosion resistance of SD345 steel, which is mainly used for reinforcing steel in concrete, was investigated by electrochemical measurements in a solution that simulates concrete with Cl-. The protective property of passive film of SD345 steel formed in saturated Ca(OH)2 solution was examined by dynamic anodic polarization and impedance measurements. It is revealed that the passive film growing with immersion time in the test solution improves the corrosion resistance of SD345 steel. However, the stability of passive film decreased in the concrete modified solution including over 0.1 M Cl-. In addition, the influence of passive film properties before corrosion test on the corrosion behavior of reinforcing steel in concrete was discussed by corrosion monitoring of SD345 steels with passive film under wet and dry cyclic environment. With increasing the growth period of passive film in the test solution, changes in the corrosion resistance of SD345 steel decreased during wet and dry cyclic environment.
Ryohei YANAGIDA, Takuro NAKAMURA, Katsuya KONO, Junichiro NIWA
Vol. 74, No. 1, pp. 10-20, Journal of JSCE (Division E2) (in Japanese)
Abstract:
This study aims to propose the mechanical models of fiber reinforced Porosity Free Concrete (PFC). The compression test, splitting cylinder test, and bending test of PFC specimens were conducted to investigate the mechanical properties of fiber reinforced PFC. The material characteristics of PFC such as the characteristic values for material strength, the compressive stress-strain relationships, and the the tension softening curve were proposed from each material test and the inverse analysis based on the results of three-point bending test, respectively. Furthermore, the size dependence of the flexural strength of fiber reinforced PFC was investigated through the four-point bending test and the finite element analysis with a discrete crack model. Based on the results of this FEM analysis, an equation to predict the flexural strength was proposed for PFC beams with the various height. Moreover, the equivalent specific length of fiber reinforced PFC beam with various height was also determined based on the numerical study using fiber modeling analysis. Finally, the tensile stress - strain relationships were obtained by the use of the equivalent specific length in order to convert the crack width of the tension softening curve into the strain.
Tomoaki SATOMI, Yuji ICHINOSE, Hiroshi TAKAHASHI
Vol. 74, No. 1, pp. 21-34, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In Japan, dehydrated cake discharged from crushed stone quarry is still disposed. To make it possible to recycle a large amount of dehydrated cake, we focused on a high temperature heating production method for recycling construction waste as concrete aggregates, we have been produced coarse aggregates for concrete by using dehydrated cake discharged from crushed stone quarry and investigated their performances. However, to produce dehydrated cake coarse aggregates, we had decided appropriate heating conditions, i.e., temperature and time of dehydrated cake granulated materials through high temperature heating test with different heating conditions. By the trial and error method, since the kinds of dehydrated cake differ depending on the kinds of crushed stone, working efficiency to produce dehydrated cake coarse aggregates decreases.
To improve the working efficiency, the objective of this study is to develop an estimation model of heat melting temperature (temperature keeping time: 30 min) of dehydrated cake discharged from crushed stone quarry based on its chemical composition by x-ray fluorescence analysis (XRF). First of all, several kinds of dehydrated cake discharged from crushed stone quarry in the Tohoku region were used and the range of heating temperature and heating time to produce dehydrated cake granulated materials were indicated through high temperature heating test. Next, the performances of melted granulated materials were evaluated and strength properties of concrete using the melted ones was measured. As a result, it was clear that the melted granulated materials can be used as coarse aggregates for concrete. Finally, based on the above results, estimation model of heat melting temperature of dehydrated cake discharged from crushed stone quarry was developed by using neural network back propagation. It was found that the estimated all results were good agreement with the measurement ones.
Yasuhiro KODA, Shohei MINAKAWA, Ichiro IWAKI
Vol. 74, No. 1, pp. 35-52, Journal of JSCE (Division E2) (in Japanese)
Abstract:
While it has long been acknowledged that water penetration into RC members under fatigue loading conditions will reduce their fatigue resistance, the influence of such water penetration on RC members subjected to freezing conditions has not yet been explored. This study evaluates the compressive and splitting tensile strength of concrete cylinders, as well as RC beam flexure properties, via static loading and fatigue testing carried out on specimens under controlled ambient temperature and moisture content conditions. The results showed that while dry concrete was unaffected by ambient temperature, water saturated concrete specimens showed reduced static strength as well as a reduction in the number of fatigue failure cycles under normal temperature conditions. However, those same saturated concrete specimens showed an increase in static compressive strength under low-temperature (freezing) conditions, even though no increase in fatigue failure cycle number could be confirmed based on incremental static strength testing. Furthermore, the flexural behavior of RC beams under water saturation conditions showed load carrying capacity and fatigue resistance reductions under normal temperature conditions, but increased load carrying capacity under low-temperature conditions. Finally, while it was revealed that the fatigue resistance of normal and low-temperature specimens were comparatively the same with regard to the number of fatigue failure cycles, there was a change in the fatigue failure mode.
Noritoshi SAITO, Hidenobu TOKUSHIGE
Vol. 74, No. 1, pp. 53-65, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In order to evaluate quantitatively and to measure by a non-contact method for degree of deterioration of concrete surface subjected to freezing and thawing action, this study investigated applicability of an arithmetical mean deviation to measurement of scaling. The arithmetical mean deviation was useful method for quantitative evaluation of measurement of scaling regardless of mix proportion, curing and experimental condition in this study, and also the measurement condition had little effect on the results of the mean, from laboratory experiments and investigation for existing actual structures. Relationships between the mean deviation and distribution of the crack density from the surface to inside of concrete cover were also discussed, thus it was revealed that the micro cracks were propagated up to 30 mm depth from the surface showed scaling. Furthermore, attempts of simplified measuring of the arithmetical mean deviation by using the stereo-camera were carried out. Evaluation of deterioration of concrete surface by using the arithmetical mean deviation was applicable satisfactory from the results of this study.
Hiroaki TAKEUCHI, Issei OZAWA, Ryota YANO, Yuki MITSUYA, Katsuhiro DOBASHI, Mitsuru UESAKA, Yasushi TANAKA, Yuya TAKAHASHI, Joichi KUSANO, Eiji YOSHIDA, Yoshinobu OSHIMA, Masahiro ISHIDA
Vol. 74, No. 1, pp. 66-79, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In response to the aging of social infrastructure, it is required to evaluate deterioration damage of concrete structure due to sophistication of maintenance technology. Authors have been developing a X-ray inspection system using mobile linac X-ray sources for bridge inspection, and trying to evaluate the state of tendons existing inside of a concrete bridge by transmission X-ray inspection. We also intend to inspect the state of grout. We have already carried out X-ray inspection system on actual bridges, but quantifying the relationship between concrete thickness and transmission X-ray imaging capability has become a problem in securing accurate inspection. For this reason, in this research, we investigated the response of X-rays with different thicknesses of concrete, and made basic studies to improve the inspection accuracy. From that, we can specify the applicable concrete thickness of each portable X-ray source. And the performance of the mobile linac X-ray source was evaluated.
Satoshi MAEHARA, Takeshi IYODA
Vol. 74, No. 2, pp. 80-87, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In this study, the effect of rain exposure on the progress of reinforcement corrosion and state of cover concrete was investigated through a survey of actual concrete structures. Sample data on the carbonation depth, cover depth, and degree of rebar corrosion were collected from 221 locations, as well as the presence or absence of rain exposure at each sampling location, and the relationship between corrosion state, spalling or falling off of the cover concrete, and the degree of rain exposure were examined. The degree of rebar corrosion was determined by analysis of rebars obtained from actual structures.
It was found that, when there is exposure to rain, the change in moisture content is larger on the surface than inside the concrete due to repetitious wetting and drying at the surface. Consequently, the corrosion rate of rebar is larger at the concrete surface than further inside the concrete.
Nozomu SOMEYA, Yoshitaka KATO, Kohei EGUCHI
Vol. 74, No. 2, pp. 88-104, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In this study, the influences of cover concrete properties (depth, degree of saturation, chloride ion concentrations, cement type, W/B, liquid phase on steel bar) were quantitatively examined by using electrochemical measurements. The difference due to the membrane potential (MP) between the half-cell potential measured on the cover concrete and the half-cell potential measured at the surface of steel bar could be observed. And the difference became larger as the degree of saturation of cover concrete became lower or the microstructure of cover concrete became denser. And, it was found that the impedance spectroscopy was affected by cover concrete properties. The impedance spectroscopy at low frequency response was related to the steel corrosion process, considering that the response at high frequencies was attributed to the cover concrete properties. Based on these results, the equivalent electrical circuit for reinforced concrete was proposed. And the differences between the proposed equivalent electrical circuit and Randles equivalent electrical circuit were discussed.
Satoshi KOMATSU, Yoto TANAKA, Tatsuya TSUBAKI, Hikaru TANIGAWA, Takatada TAKAHASHI
Vol. 74, No. 2, pp. 105-118, Journal of JSCE (Division E2) (in Japanese)
Abstract:
To optimize concrete tracks in terms of reasonable loading structure, superior workability, easy maintenance and economic efficiency, a new solid-bed track with resilient sleepers has been developed by the authors. In this research, to clarify the shrinkage behavior of this track, full-scale track members were prepared. To investigate the shrinkage behavior of the track, numerical simulation was performed using a three-dimensional multi-scale coupled model where the microscopic characteristics of cementitious composites and nonlinear structural mechanics are integrated.
The results of this study indicate that shrinkage cracks can be generated from just under the corner of sleepers in an inverted V shape when the thickness of the track is relatively thin, on the order of 80 mm. However, generation of shrinkage cracks can be restricted when the thickness of the track is greater than about 280 mm, as is typical in snowy cold regions. The results indicated also that the generation of shrinkage cracks is unlikely when the thickness of the track is about 580 mm. This may be due to the fact that the age at which the main stress peaks is delayed as development of shrinkage behavior slows down when the thickness of the track is large, and therefore the tensile strength of the concrete increases with age. Another reason might be that the restraining effect of the concrete bed of the track is small when the thickness of the track is large.
In addition, to control the propagation of shrinkage cracks, the position and size of crack induced joints were investigated. Based on the numerical simulation results, it was found that shrinkage cracks can be vertically generated when the sectional defect range is set to about 10%.
Yasuaki ISHIKAWA, Tada-aki TANABE
Vol. 74, No. 2, pp. 119-138, Journal of JSCE (Division E2) (in Japanese)
Abstract:
It has been generally accepted so far that the initial strain method may be used for crack problems due to chemical reaction induced expansion in concrete because there exists no other reliable method although the initial strain method is not adaptable in some cases. The concept of the work constant theory established by Dr. Tsuji has known to be adaptable for such kinds of problems. However, generalization of his theory has not been yet achieved.
In this paper, unified analytical method is presented in order to treat varieties of chemical expansion in concrete based on the mechanical energy conservation hypothesis, which improves theoretical defects of the work constant theory. Then, some numerical simulations for experimental results such as ASR and expansive concrete are carried out and the proposed method is shown to give more reasonable numerical results than the existing method. Moreover, the proposed method is shown to give admissible numerical results for damage problem containing MgO. Finally, the importance of the accumulation of chemical expansion energy data is stressed for unified treatment in the guidelines to evaluate crack and crack width for such chemical expansion problems.
Takashi MISAWA, Tetsuya HIRONAKA, Osamu YAMAGUCHI, Kimitaka UJI
Vol. 74, No. 3, pp. 139-157, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Reinforced concrete jacketing and steel plate jacketing are widely used to increase the flexural strength of existing reinforced concrete bridge piers. Efforts are being made, therefore, to develop a more efficient and economical seismic retrofit method using a thinner jacketing material. This study proposes an economical seismic retrofit method for increasing the flexural strength of an existing reinforced concrete pier by placing small-diameter steel bars around the pier for flexural and shear reinforcement and jacketing the pier with a thin and light layer of sprayed mortar. In the proposed method, small-diameter deformed prestressing steel bars or high-strength steel reinforcing bars (USD685) are used for axial reinforcement. To ensure ease of installation and minimize effects on footing structure, the embedment end of each axial reinforcement bar is pressed into a flatter and wider shape so that the embedment length of the steel bar in the footing can be made shorter.
Reversed cyclic loading tests on a 1/4-scale specimen mimicking an existing reinforced concrete railway bridge pier showed that the proposed method is a useful means of increasing the flexural strength of an existing reinforced concrete pier and that the load-carrying capacity and deformability of piers retrofitted by the proposed method can be evaluated by using conventional evaluation formulas.
Kodai MATSUOKA, Tsutomu WATANABE, Shintaro MINOURA, Masamichi SOGABE, Akitoshi OMODAKA
Vol. 74, No. 3, pp. 158-175, Journal of JSCE (Division E2) (in Japanese)
Abstract:
More than 50 years have elapsed since the fist introduction of PC sleepers, and some damage sleepers have also been confirmed. Although it is necessary to detect and replace damaged PC sleepers properly, it is difficult to find the damages in the ballasted track because inspectors can only see the upper surface of the sleepers. In this study, various vibration and sound measurements were conducted to develop a damaged PC sleeper detection method using modal characteristics. The bending tests, vibration and sound measurements, and numerical analyses revealed that the natural frequencies are clearly dropped due to open cracks at the cross section of rail seat, and the vibration measurement of the actual damaged PC sleepers clarified that the natural frequency of third mode have high correlation with the damage degree. In addition, a simple detection method using a sound level meter was proposed and applied to the test line and actual rail lines. As a result, it is possible to detect damaged PC sleepers efficiently with the similar accuracy of multi-point detailed measurement method.
Yuta YAMADA, Nobuhiro CHIJIWA, Mitsuyasu IWANAMI
Vol. 74, No. 3, pp. 176-191, Journal of JSCE (Division E2) (in Japanese)
Abstract:
The cyclic loading experiments and FE analyses were conducted to make clear the effect of stirrups on shear fatigue load carrying mechanism of RC beams with rebar corrosion cracks. To simulate the most severe state of rebar corrosion cracks, artificial cracks were installed in the beam specimens. As a result of the loading experiments, tied arch mechanism appeared in the beams which had artificial crack tips inside of vertical stress non-contributed region (B-region). No remarkable difference was observed on the load carrying mechanism between sound beams and the beams which had artificial crack tips inside of vertical stress contributed region (D-region). In addition, the dowel action of stirrups was identified from the comparison with the slip displacements on the artificial crack surfaces of the cracked beams with and without stirrups. After the loading experiments, the validity of reproducing method of load carrying mechanism by using artificial cracks was confirmed based on the result of beams which had real corrosion cracks. As a result of decomposition of the load carrying mechanism based on FE analysis, in the beams which had artificial crack tips inside of B-region, the absorbed energy of arch mechanism was decreased by the slip resistance on the artificial crack due to the dowel action of stirrups. It was confirmed that when the absorbed energy of arch mechanism was high, the fatigue life became short regardless of the existence of stirrups and position of the artificial crack tips.
Makoto YAMAMOTO, Koji TAKEWAKA, Toshinobu YAMAGUCHI, Yoshikazu AKIRA
Vol. 74, No. 3, pp. 192-206, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Cathodic protection is a highly reliable corrosion protection method for re-bar in concrete. Generally, “100-mV Polarization Shift or Depolarization Shift” is used as a criterion of cathodic protection for rein-forcing steel in concrete.
In this study, we examined the relationship between potential shift values and effect of cathodic protection, using concrete specimens in which small, electrically-connected steel splits were embedded. As the result, we found that the corrosion rate can be reduced by the cathodic protection applied in the range of less than 100-mV polarization shift. However, from the point of view to stop the corrosion reaction electrochemically, we concluded that 100-mV polarization shift is appropriate as the criterion.
Furthermore, we proposed a method of supplying protection current, the installation position of a reference electrodes, and the design method of criterion of cathodic protection for corrosion rate.