Vol. 76, Issue 1 2020, Journal of JSCE (Division E2) (in Japanese)
Vol. 76, Issue 2 2020, Journal of JSCE (Division E2) (in Japanese)
Vol. 76, Issue 3 2020, Journal of JSCE (Division E2) (in Japanese)
J-Stage (Journal of JSCE in Engish)
J-Stage (Journal of JSCE (E2 Division) in Japanese)
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Toshihiro MATSUKURA
Volume 76 Issue 1 Pages 1-20, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/1/76_1/_article/-char/en
Abstract:
There are various direct tensile tests to estimate tensile stress-strain curve of concrete. However, in direct tensile test, bending moment which is hard to erase generates strain gradient at cross section of specimen. Present direct tensile test estimates stress in the way of dividing resultant force by the area of cross section. If strain gradient occurs, this calculation method cannot estimate accurate stress-strain curve. Inverse analysis using bending test apparatus is proposed which can estimate tensile stress-strain curve from force-deformation curve measured at loading point. However, this inverse analysis has some problem. For example, reproducing detail test condition is required. I propose method to estimate tensile stress-strain curve in direct tensile test under large strain gradient. This method is characterized by measuring system and equations. The measuring system is as follows. Indentation marks are established at the both narrow side of tabular test piece to stabilize fracture location. I define cross section between these two indentation marks as estimation section. Strain measuring apparatuses are established at the unilateral long side to measure strain distribution in estimation section. Give tensile force to tabular test piece and measure resultant force vertical to estimation section. The equations are based on inverse estimation method and can calculate stress corresponding to strain from the time series data of resultant force and strain distribution in estimation section by linking the time series data. I certificate that this method can estimate accurate stress-strain curve under strain gradient by executing numerical analysis. This method gives variance to the shape of test piece around the estimation section. So test equipment can be simplified.
Ko KAKUMA, Hiroaki NISHI, Shinya WATANABE, Shuichi ONO, Hiroshi MASUYA, Yoshimori KUBO
Volume 76 Issue 1 Pages 21-40, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/1/76_21/_article/-char/en
Abstract:
There are various direct tensile tests to estimate tensile stress-strain curve of concrete. However, in direct tensile test, bending moment which is hard to erase generates strain gradient at cross section of specimen. Present direct tensile test estimates stress in the way of dividing resultant force by the area of cross section. If strain gradient occurs, this calculation method can t estimate accurate stress-strain curve. Inverse analysis using bending test apparatus is proposed which can estimate tensile stress-strain curve from force-deformation curve measured at loading point. However, this inverse analysis has some problem. For example, reproducing detail test condition is required. I propose method to estimate tensile stress-strain curve in direct tensile test under large strain gradient. This method is characterized by measuring system and equations. The measuring system is as follows. Indentation marks are established at the both narrow side of tabular test piece to stabilize fracture location. I define cross section between these two indentation marks as estimation section. Strain measuring apparatuses are established at the unilateral long side to measure strain distribution in estimation section. Give tensile force to tabular test piece and measure resultant force vertical to estimation section. The equations are based on inverse estimation method and can calculate stress corresponding to strain from the time series data of resultant force and strain distribution in estimation section by linking the time series data. I certificate that this method can estimate accurate stress-strain curve under strain gradient by executing numerical analysis. This method gives variance to the shape of test piece around the estimation section. So test equipment can be simplified.
Kazumasa OKUBO, Michio IMAI, Naoki SOGABE, Shinji NAKAUE, Kazuyoshi CHIKIRI, Junichiro NIWA
Volume 76 Issue 1 Pages 41-54, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/1/76_41/_article/-char/en
Abstract:
For prestressed concrete structures, it is important to apply and maintain the required tensile force of the prestressing cable. During the construction and in the service period, in order to directly evaluate the distribution of tensioning force along the whole length of a prestressing cable, a new measuring method by using the optical fiber sensor has been developed. In this study, measurement performance tests were conducted, and it was verified that the optical fiber sensor can be integrated with the PC-strand and the distribution of tensioning force can be measured accurately. Furthermore, this new method was applied to a post-tensioned prestressed concrete viaduct. It was confirmed that, the distribution of tensioning force can be measured even in the actual structure, and it can be directly confirmed that the installed prestressing force exceeded the designed value, along the whole length of the cable. This method can be effectively used for the maintenance of PC structures, in addition to the control of prestressing.
Yasuhiro NAKAYA, Minoru KUNIEDA
Volume 76 Issue 2 Pages 55-64, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_55/_article/-char/en
Abstract:
This paper presents test results of pull-out behavior of short fiber (PP fiber and steel fiber) subjected to monotonic and cyclic loading. In the case of PP fiber, pull-out resistance under cyclic loading was slightly decreased comparing to that of monotonic loading. In some cases, load was suddenly dropped due to split crack due to cyclic loading. In addition, bending of PP fiber induces a damage due to compression action in the test. In the case of steel fiber, frictional bonding behavior was observed in both tensile and compression phases.
Kazuaki WATANABE, Takumi SHIMOMURA, Norihiro FUJIMOTO, Hisatoshi KASAHARA, Takanobu SUZUKI
Volume 76 Issue 2 Pages 65-77, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_65/_article/-char/en
Abstract:
An integrated heat transfer analysis of manhole and soil was conducted to predict hydrothermal condition and condensation in manhole, which affects deterioration process of manhole for information network. It was verified that time-dependent change of temperature in manholes in various region in Japan can be simulated. Based on the results of heat transfer analysis, occurrence of condensation was predicted. Water content was calculated by moisture transfer analysis in concrete, in which capillary suction of condensed water. It was clarified that condensation likely occur in manhole in winter and accordingly water content in concrete become higher in winter, which might accelerate corrosion of reinforcement in concrete.
Kazuaki WATANABE, Takumi SHIMOMURA, Norihiro FUJIMOTO, Hisatoshi KASAHARA, Takanobu SUZUKI
Volume 76 Issue 2 Pages 78-88, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_78/_article/-char/en
Abstract:
A prediction method for reinforcing bar corrosion in concrete was developed to assure efficient maintenance of concrete manholes for information network. An equation for corrosion rate of reinforcement in concrete of manholes was proposed, which took into account the effect of moisture content of concrete, temperature and supply of oxygen to reinforcement. Corrosion of reinforcement of manholes under various conditions were calculated as a function of time based on prediction results of hydrothermal condition in manhole by integrated heat transfer analysis of soil and structure. It was verified that tendencies of deterioration process of manholes due to reinforcement corrosion in various region in Japan can be predicted considering differences in regional climatic conditions.
Hiroaki HASEGAWA, Isamu YOSHITAKE, Takahisa KATO
Volume 76 Issue 2 Pages 89-97, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_89/_article/-char/en
Abstract:
Near Surface Mounted (NSM) method using Carbon Fiber Reinforced Polymer (CFRP) rods of ultra-high modulus is suitable to strengthen cantilevered deck slab subjected to negative bending moment. The NSM technique has some advantages such as negligible increase of dead-load and no corrosion of reinforcement. However, the most concern is low bond strength of the ultra-high modulus CFRP rods without shear-resistant ribs. This study focuses on the bond improvement method of the ultra-high modulus CFRP rod embedded in concrete or mortar which is a filling material for NSM. The pull-off test of CFRP rod embedded in concrete or mortar was conducted to examine bond performance. The test result confirmed that the attachment of Glass Fiber Reinforced Polymer (GFRP) rib to the CFRP rod is relatively effective to improve the bond performance. This paper presents the best dimensions of the GFRP rib to effectively improve bond performance of the ultra-high modulus CFRP rod.
Tatsuhiko SAEKI, Jun TOMIYAMA, Fuminori NAKAMURA, Ryota NAKAMURA, Daishin HANAOKA, Lin AN, Iwao SASAKI, Hirotake ENDOH
Volume 76 Issue 2 Pages 98-108, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_98/_article/-char/en
Abstract:
In this study, the same mortar chip specimens were exposed to estimate airborne salt environment in 101 places in Japan. The conversions of the chloride content of the specimen into the surface chloride concentration were carried out. The revised distance was calculated using the distance between specimen and shoreline, the altitude of specimen, the wind direction and the wave energy of exposure test place. From the regression analysis, the estimation method of the surface chloride concentration of the concrete at various environment using the revised distance was formulated.
Hiroshi YAMADA, Hiroshi KATAHIRA, Hiroshi WATANABE, Takumi SHIMOMURA
Volume 76 Issue 2 Pages 109-118, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_109/_article/-char/en
Abstract:
In design phase, drying shrinkage strain of concrete is often obtained by a prediction equation. In the prediction formula of the current Japan society of civil engineers, a coefficient α indicating the influence of aggregate quality is introduced. It is said that the prediction formula can predict approximately ±50% with respect to the actual measurement values of the concrete drying shrinkage strain. The coefficient α representing the influence of the quality of the aggregate is substituted into the prediction expression by the value of 4 to 6, but the value is not determined by the type of aggregate or the like. In this research, we analyzed that the actual values of coefficient α expressing the effect of aggregate quality by using data of concrete using coarse aggregate including quality other than Japanese industrial standard. In addition, we modified the prediction equation as a function consisting of the each water content in mortar and coarse aggregate. Moreover, we proposed a formula for calculating the coefficient α’ representing the influence of the quality of the coarse aggregate.
Daisuke YAMAZAKI, Mitsuyasu IWANAMI
Volume 76 Issue 2 Pages 119-129, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_119/_article/-char/en
Abstract:
The main required performance of repair adhesives is adhesion, and the change of the material properties on the adhesion surface is important in the durability evaluation. However, it has been difficult to directly evaluate the change in strength of adhesive surface part so far. Therefore, we analyzed the surface strength change accompanying the deterioration of epoxy resin by using surface / interface cutting analysis system. By using the surface / interface cutting analysis system, it became clear that the way of being affected by water absorption and drying changed depending on the kind of curing agent. In the accelerated degradation test with alkaline solution, it became clear that the surface strength greatly decreased initially, then became slow as the immersion time prolonged, and the deteriorated form changed with time. Furthermore, deterioration of the adhesive was dominant by alkali, but it was confirmed that it is also susceptible to water influence at the initial stage. The evaluation of the mechanical properties of the micro area on the surface using the surface and interface cutting analysis device can quantify the progress of deterioration, and is considered useful for evaluating the durability of the adhesive.
Hideaki SATOH, Shingo MIYAZAWA
Volume 76 Issue 2 Pages 130-143, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_130/_article/-char/en/
Abstract:
In concrete dams, the control of thermal stress caused by hydration heat of cement is an important issue. For that reason, various studies have been conducted for thermal crack control for a long time. In recent years, with the development of analytical methods, it has become possible to examine the thermal stress in the design and construction stages in detail. On the other hand, it has been made clear that, even with lean mixed dam concrete, autogenous shrinkage should not be ignored depending on the type of cement and mix proportion. In this study, the effect of the autogenous shrinkage strain on thermal stress in construction stage of concrete gravity dams was experimentally and analytically investigated. As a result, it has been made clear that autogenous shrinkage strain can be a cause of thermal cracking in concrete gravity dams during construction stage.
Shunsei TANAKA, Yuya SAKAI
Volume 76 Issue 2 Pages 144-157, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/2/76_144/_article/-char/en
Abstract:
As a fundamental study to establish a method for evaluating the scaling resistance of concrete in a short period of time based on the analysis of drilling powder, the correlation between the scaling resistance of cement paste and mortar and the pore volume evaluated by drilling powder was investigated. The pore volume in the drilling powder was measured by mercury intrusion porosimetry. For cement paste, the scaling resistance sharply decreased when the pore volume evaluated with drilling powder exceeded around 0.20 mL/mL, regardless of the water to cement ratio or the entrained air volume. In addition, for mortar, a method for evaluating the pore volume of the cement paste portion in the hardened matrix by applying heat treatment and acid dissolution treatment to drilling powder was proposed. As a result, it was observed that the scaling resistance of mortar specimen sharply decreased when the pore volume of the cement paste portion which were evaluated by proposed method exceeded around 0.18 mL/mL. These results suggest that the scaling resistance of cementitious materials can be estimated even from fine drilling powder.
Yuki TADA, Taito MIURA, Hikaru NAKAMURA
Volume 76 Issue 3 Pages 158-170, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_158/_article/-char/en
Abstract:
In this paper, the experimental investigation for visualization of the area of internal crack and rebar corrosion in concrete structure by using electromagnetic wave radar was carried out. Firstly, the specimens with the rebar cover thickness (30, 60 mm) were made in which local corrosion area with different corrosion rate were introduced by electrolytic corrosion experiment, and the crack width and distribution characteristics and the corrosion distribution of the rebar were evaluated. Then, the visualization of internal cracks and corrosion areas by applying Self-Organizing Map (SOM) is tried by using indexes that the difference of electromagnetic wave reflection waveform data between damaged and sound parts are considered. As a result, by applying one-step SOM to corrosion specimens, it was confirmed that corrosion areas of rebar can be detected. Moreover, we propose a method to evaluate internal cracks and corrosion amount by two-step SOM and verified the applicable range. It was confirmed that the presence of internal cracks can be quantitatively and clearly evaluated, and it was confirmed that internal cracks of 0.1 to 0.4 mm and corrosion rates of about 4% can be detected.
Atsushi SAITO, Takahiro NISHIDA, Nobuaki OTSUKI, Shu YAMAMOTO, Kazuaki MORI, Toshinari HAYASHI, Akira SHONO, Makoto SHOJI
Volume 76 Issue 3 Pages 171-188, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_171/_article/-char/en
Abstract:
The purpose of this paper is to verify the applicability of a simple water supply method using water supply curing system as an external solution supply method in electrochemical corrosion control method. The study was conducted focusing on (a) the design method, (b) the repair effect of the amount of solution, the distance between the concrete surface and the anode, and the type of anode material, and (c) the applicability to the actual structure.
As a result, a design method for selecting the suction port position and suction machine based on computation fluid dynamics was established. In addition, there was no effect of the amount of solution on the realkalization and desalination effects. On the other hand, the electrodeposition effect was found to differ depending on the type of anode material. It was also found that the greater the distance between the concrete surface and the anode, the greater the effect. Furthermore, as a result of application to actual structures, it was confirmed that the simple water supply method was easy to construct and could be applied to complex surface shapes, and also contributed to the suppression of external solution disappearance.
Fuminori NAKAMURA, Ryohei OHARA, Takayuki YAMAGUCHI, Takumi SHIMOMURA
Volume 76 Issue 3 Pages 189-208, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_189/_article/-char/en
Abstract:
Airborne chlorides from sea surface consists of small particle of seawater, generated by interaction of wave, wind and coastal structures. Airborne chlorides, which is transported by wind sticks to the surface of structures, harms long-term durability of the structures. In this study, field observation of surface chloride concentration from sea surface were carried out in the coast where the wave-dissipating concrete blocks were installed. Prediction model for surface chloride concentration, based on geographical condition in the coast, is also developed. From the results, it was shown that the amount of the surface chloride is related to the geographical condition that wave-dissipating concrete blocks installed in the coast. The increased amount of surface chloride is estimated by classifying and quantifying a locations of the wave-dissipating concrete blocks. It was confirmed that calculation results of surface chloride concentration of concrete agree with the field measurements data.
Seiji NAGATA, Toyofumi MATSUO, Hironori MOROZUMI, Keizo OHTOMO
Volume 76 Issue 3 Pages 209-228 , 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_209/_article/-char/en
Abstract:
This paper deal with the strength and hysteretic behavior during an earthquakes associated with the anchorages considering the effects of flexural cracks developed in reinforced concrete. In the experiments, eight reinforced concrete specimens with four headed anchor bolts are used. These specimens include two types of anchorages depending on the failure modes: the bolt yield type and the concrete failure type. The Results of cyclic loading tests (static tests) show that the effects of the flexural cracks in the anchorage strength appears more obviously in the concrete failure type than the bolt yield type. However, the strength can be recovered by applying crack repair with the epoxy injection. In addition, a series of the shake table tests (dynamic tests) present that the nonlinear hysteretic behavior of the anchorages under the dynamic loads demonstrates well those under the static loads.
Ryota KASAKURA, Toshiyuki KUROIWA, Toshiya TADOKORO, Kimitaka UJI
Volume 76 Issue 3 Pages 229-238, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_229/_article/-char/en
Abstract:
The authors developed a new retrofitting method aimed at improving the productivity of seismic retrofitting works. The developed method is seismic retrofitting method using divided precast panel, high strength fiber reinforced mortar and steel plate. The mortar is poured into the gap between the objective column and precast panels around it assembled with steel plate and bolt. There are few cases using high strength fiber reinforced mortar for seismic retrofitting, and its ductility is not clear. Therefore, in this paper, in order to clarify the ductility of the RC members retrofitting by this method, amount of steel plate, the high strength fiber reinforced mortar and the sectional dimensions were set as variables, and cyclic loading tests was conducted. As a result, the influence of high strength fiber reinforced mortar on ductility was clarified and an calculation formula was reconstructed.
Yuichi KITANO, Hajime ITO, Satoshi SUZUKI
Volume 76 Issue 3 Pages 239-254, 2020, Journal of JSCE (Division E2) (in Japanese)
URL:
https://www.jstage.jst.go.jp/article/jscejmcs/76/3/76_239/_article/-char/en
Abstract:
The purpose of this research is to realize lightweight and high strength prestressed concrete slab by using lightweight concrete mixed with short fibers.
In this paper, it was confirmed that the PVA short fiber mixing ratio should be 0.5vol.% or less in order to obtain mechanical performance equivalent to those of lightweight aggregate concrete with a compressive strength of 50 MPa. In addition, it was confirmed that the lightweight PC slab mixed with 0.5vol.% PVA short fibers had the same punching shear capacity as the normal PC slab. Furthermore, the increase in shear capacity of lightweight PC slab mixed with short fibers was considered to be due to suppression of crack extension in the RC section and the accompanying tide arch formation in the PC section.