Vol. 4, No. 1, Division E (Materials, Concrete Structures and Pavements), Journal of JSCE (in English)
J-Stage (Journal of JSCE in Engish)
J-Stage (Journal of JSCE (E2 Division) in Japanese)
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SHEAR-RESISTING MECHANISMS OF PRE-TENSIONED PC BEAMS WITHOUT SHEAR REINFORCEMENT STRENGTHENED BY CFRP SHEETS
Thi Thu Dung NGUYEN, Koji MATSUMOTO, Yuji SATO, Masahiko YAMADA and Junichiro NIWA
Vol. 4, No. 1, pp. 59-71, Journal of JSCE (in English)
Abstract:
Although externally bonded carbon fiber-reinforced polymer (CFRP) sheets have been used more commonly for the strengthening of existing reinforced concrete (RC) structures, the effects of this strengthening method on prestressed concrete (PC) beams have not been well clarified. In this study, an experiment was conducted to investigate the behaviors of pre-tensioned PC beams without shear reinforcement strengthened in shear using externally bonded CFRP sheets with the consideration of CFRP reinforcement ratio, stiffness and prestressing level in strands. The results implied that the shear resistance in the strengthened PC beams depended on maintaining the combination of beam action, arch action, and the bonded sheets. The failures and the increase in shear capacity of the strengthened PC beams were strongly affected by the amount, thickness of the CFRP sheets, and the effective prestress in the strands. The higher effectiveness of strengthening could be obtained in the beams strengthened with a higher CFRP reinforcement ratio of the same thickness, higher elastic modulus sheets or having higher prestressing level. Nevertheless, the increase in the thickness of the sheets did not provide a better performance. Moreover, the high inaccuracy in the calculations using the equations stipulated in the recent design guidelines compared to the increment of the shear strength obtained by the experiment was explained by the shear-resisting mechanisms.
A NEW ALTERNATIVE SHEAR IMPROVEMENT OF CONCRETE BEAMS BY INTERNALLY REINFORCING PBO FIBER MESH
Sirapong SUWANPANJASIL, Koji MATSUMOTO, Junichiro NIWA
Vol. 3, No. 1, pp. 67-80, Journal of JSCE (in English)
Abstract:
This paper aims to develop a new method for shear reinforcing concrete beams by using the ultrahigh performance PBO fiber mesh as a replacement for conventional stirrups inside a concrete structural member. The elementary test was performed first to investigate the general behavior of the internal reinforcing PBO fiber mesh as a fundamental objective of this study. Then, nine RC beams with and without internal PBO fiber mesh were conducted in the RC beam test. The parameters in the RC beam test were the number of internal PBO mesh layers, the width of internal PBO mesh in the shear span, and the reinforcing configuration of the internal PBO mesh. The experimental results showed that the shear capacity and the shear carried by internal PBO fiber mesh increased significantly with a higher number of the internal mesh layers; however, the shear capacity decreased when the width of internal mesh in the shear span was expanded. Besides, the difference in reinforcing configuration of the internal PBO mesh showed a great impact on the shear capacity of concrete beams reinforced with internal PBO fiber mesh. Furthermore, an empirical method for evaluating shear carried by internal PBO fiber mesh was modeled and a moderate agreement between values from the model and values from the experiment was obtained.
SHEAR FAILURE MECHANISM OF REINFORCED CONCRETE HAUNCHED BEAMS
Chenwei HOU, Koji MATSUMOTO, Junichiro NIWA
Vol. 3, No. 1, pp. 230-245, Journal of JSCE (in English)
Abstract:
This study aims to clarify the shear resistance mechanism of reinforced concrete haunched beams (RCHBs). Four series of ten RCHBs with different parameters (positions of haunched portions, thickness of the concrete cover, presence of stirrups and the arrangement of the tensile rebar) were tested. The results demonstrated that the bending position of the tensile rebar as well as the different arrangement of the tensile rebar highly influenced the crack propagations which caused the variation in the shear capacities due to different contributions of the arch action. Different diagonal crack angles also resulted in different contributions by stirrups in RCHBs with stirrups. The thicker concrete cover at the mid span affected the crack propagation but had almost no effect on the shear capacity. Nonlinear FEM analyses were also conducted to complement the experiments and verify the results, which showed a good agreement including load-deflection curves, load capacities and crack patterns. The shape of the compression zone, which dominates the arch action in RC beams, was also evaluated by the analyses.
STUDY ON EVALUATION OF STRUCTURAL PERFORMANCE IN 15-YEAR-OLD PC ROAD BRIDGE AFTER RECONSTRUCTION UNDER SEVERE CHLORIDE ENVIRONMENT
Masaki MIYAMURA, Hideki NAITO, Satoshi NAKANO, Masuo KADO, Ichiro IWAKI and Motoyuki SUZUKI
Vol. 72, No. 2, pp. 41-55, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In this study, the structural performance of 15-year-old PC box-girder road bridge after reconstruction under severe chloride environment was evaluated. Since non-destructive test should be used for evaluating the structural performance of bridge in service, static and dynamic loading tests using dump trucks, impact vibration test by weight, and forced vibration test by vibration exciter were applied, focusing on the stiffness in whole superstructure, members, and local points in birdge. Also, by carrying out the FEM analysis considering the test results, it was verified the validity of consistency and test methods of various vaibration test results with different inspection range. These field testing results reveal that the stiffness of whole superstructure is similar to the design value, the degradation of stiffness in a part of decks is indicated, and in some local points in deck, the stiffness is remarkably decreased.
SEISMIC DEFORMATION OF A STEEL-CONCRETE SANDWICH MEMBER COMPOSED OF STEEL ELEMENTS CONNECTED WITH INTERLOCKING JOINTS
Tomonori ABO, Tadayoshi ISHIBASHI, Shigeru MATSUOKA, Tatsuji NAGAO and Motoaki KURISU
Vol. 72, No. 2, pp. 56-67, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Currently, very few studies have been published that aim to examine the seismic deformation performance of a steel-concrete sandwich member integrating shear reinforcing steel plates which, with no displacement stop, are placed perpendicular to the member's axis. Furthermore, as regards the member composed of steel elements connected with interlocking joints, there have been no studies that quantitavely evaluate bending deformation performance under axial forces. In order to investigate this problem, we conducted a cyclic loading test of a full-scale specimen, through which we confirmed that localized cracks develop in the concrete, and using a non-linear finite element method, clarified a mechanism in which bending deformation progresses along with opening of localized cracks. At the same time, we proposed a model able to evaluate the amount of deformation in a simple quantitative way by accumulation of rotational deformations of blocks sandwiched between shear reinforcing steel plates. The validity of this model was demonstrated with a loading test and a finite element analysis.
FATIGUE EVALUATION FOR RC FOUNDATION OF WIND TURBINE BASED ON FIELD MEASUREMENT AND NONLINEAR FE ANALYSIS
Kaoru YONETSU, Chikako FUJIYAMA, Masuo KADO, Takuya MAESHIMA and Yasuhiro KODA
Vol. 72, No. 2, pp. 68-82, Journal of JSCE (Division E2) (in Japanese)
Abstract:
This paper shows fatigue evaluation method based on field measurements and FEM for RC foundation of wind turbine rated as 40 kW power class. First, field measurements for existing wind turbine were carried out to investigate the relation of action-response of tower-foundation system. Through a data analysis of the results of field measurement, multi-directional bending moment on foundation was expected. Next, a integrated model of tower-foundation system was built up for three dimentional nonlinear FE analysis. Damage process of reaching failure of the model was examined and limit state of concrete in the foundation was defined by numerical simulation. Furthermore, one of the indexes assessing damage state could identify a fatigue limit state of concrete subjected to repetition of loads.Consequently, the S-N diagram derived from the index indicated that the number of repetition of multi-directional loads reaching the fatigue limit state of concrete is much smaller than the number of repetition assuming single-direction loads, and experience of excessive load amplitude can affect the latter fatigue damage.
QUANTITATIVE EVALUATION OF WATER MIGRATION IN CONCRETE WITH THRESHOLD PORE DIAMETER OBTAINED BASED ON CRITICAL VOLUME FRACTION FOR PERCOLATION
Yuya SAKAI and Toshiharu KISHI
Vol. 72, No. 2, pp. 83-96, Journal of JSCE (Division E2) (in Japanese)
Abstract:
This study proposes a quantitative evaluation method of water migration in concrete. The threshold pore diameter (TPD) was obtained using the concept of critical volume fraction for percolation (CVFP; assumed to be 16%). This TPD had good correlation with the TPD obtained using another method which we had proposed in a previous study. The time required for water to penetrate in the concrete specimen by capillary actioin was calculated using the obtained TPD and compared with the measured time. The comparison yielded the tortuosity of six. Based on the concept of CVFP, the volume fraction of the pore whose size is greater than TPD can be constant. Permeated water volume in a water permeability test was calculated assuming tortuosity and effective area to be six and 16%, respectively, and the results agreed to some extent with the experimental ones. However, the calculation with the effective area of 16% overestimated the permeated water volume. We suggest that trapped air bubble during water infiltration can be the reason for the gap.
STUDY ON EVALUATION METHOD OF AUTOGENOUS SHRINKAGE STRAIN IN DAM CONCRETE
Hideaki SATO and Shingo MIYAZAWA
Vol. 72, No. 2, pp. 97-108, Journal of JSCE (Division E2) (in Japanese)
Abstract:
For the control of thermal cracking of concrete gravity dams in the design and construction stages, the effect of autogenous shrinkage of concrete on thermal ceacking has been considered to be negligible from such that it is lean mix concrete. On the other hand, the effects of cement type and mix proportion on autogenous shrinkage of dam concrete have not been made clear. In this study, autogenous shrinkage strain of dam concrete using full-sized aggregate was experimentally investigated. Autogenous shrinkage characteristics of dam concrete with several types of cement, which have generally been used in Japan, was also investigated. In addition, the design values of autogenous shrinkage strain to be used for verification of thermal cracking in the construction stage of concrete gravity dams were proposed.
FUNDAMENTAL STUDY ON IMPROVEMENT OF ESTIMATION ACCURACY OF CONTENT OF CHLORIDE IONS IN CONCRETE USING ELECTROMAGNETIC WAVES METHOD
Junichiro NOJIMA, Mami UCHIDA, Junichi ARAI and Toshiaki MIZOBUCHI
Vol. 72, No. 2, pp. 109-125, Journal of JSCE (Division E2) (in Japanese)
Abstract:
Chloride induced corrosion is one of the cause of deterioration reinforced concrete structures. In generally, as one of evaluation method of deteriorated situation caused by reinforcement corrosion in the concrete, drawing cores and chemical analysis are carried out. It is possible to perceive chloride content in the neighborhood of reinforcing bars. However, it is not possible to perceive only chloride ions at the position drawn cores and difficult to perceive about any corrosion of reinforcement unless corrosion induced cracks appear on the surface. Then, if it is possible to estimate the chloride ions in concrete using electromagnetic waves as a non-destructive method, it is possible to perceive the chloride ions in concrete without giving any damages. In addition, it is possible that this method conveniently evaluate the condition of degradation in respect of the wide area.
From past studies, it was confirmed that the amplitude value of the electromagnetic waves decreases with increasing chloride ions within concrete. It is possible to estimate chloride ions by utilizing this characteristic.
In this report, in order to improve the accuracy of this method, the theory construction and confirmation experiment were carried out. At first, the phenomenon of attenuation of electromagnetic waves by content of chloride ions in concrete was clarified by applying the electromagnetism and physicochemical theory. Next, each optimal solution was obtained by the result of measurement of radar, using specimens of concrete in which varied depth of concrete, temperature, water content and chloride content.
As the results, it is possible that the attenuation characteristics to electromagnetic waves by material changes of properties of concrete and to obtain the principle equation which contribute to improve in accuracy of estimation of chloride ions in concrete using electromagnetic waves.
INFLUENCE OF ALKALI SILICA REACTION ON FATIGUE RESISTANCE OF RC BRIDGE DECK
Takuya MAESHIMA, Yasuhiro KODA, Ichiro IWAKI, Hideki NAITO, Ryo KISHIRA, Yasunori SUZUKI, Koji OHTA and Motoyuki SUZUKI
Vol. 72, No. 2, pp. 126-145, Journal of JSCE (Division E2) (in Japanese)
Abstract:
This study aims at investigating an influence of alkali-silica reaction (ASR) on fatigue resistance of RC bridge deck. Firstly, using full-sized RC deck specimens, two types of ASR accelerated tests were performed by varying the environmental condition of ASR. Then, a wheel load trucking test was conducted focusing on the presence or absence of water on upper-surface of the specimen. In this experiment, the deflection and crack patterns of RC deck specimen in each number of trucking were measured, and the degradation of stiffness due to ASR and fatigue was evaluated by forced vibration test using small vibration device. As a result, it was revealed that the fatigue resistance of RC bridge deck by ASR depended on the environmental condition of ASR, which was assumed due to the introduction of chemical prestress by ASR, and the interaction of crack propagation and water action. Furthermore, the vibration test proved useful in evaluating the fatigue resistance of RC bridge deck by ASR.
EXPERIMENTAL STUDY ON FLEXURAL LOAD-CARRYING BEHAVIOR OF REINFORCED RC BEAMS WITH PRETENSIONED AFRP SHEET
Norimitsu KISHI, Hiroshi MIKAMI and Yusuke KURIHASHI
Vol. 72, No. 2, pp. 165-180, Journal of JSCE (Division E2) (in Japanese)
Abstract:
To establish a rational flexural reinforcing method for existing Reinforced Concrete (RC) beams using pretensioned Aramid Fiber Reinforced Polymer (AFRP) sheet, static loading tests on flexural reinforced RC beams were conducted taking sectional shape of beam, rebar ratio, sheet volume ratio, shear span ratio, and pretension force ratio as variables. In this study, the effects of these parameters on load-carrying capacity of the beams and debonding behavior of the sheet were investigated by comparing with between experimental results and analytical ones calculated by means of the multi section method. Furthermore, empirical prediction equations for failure mode of the RC beams reinforced with pretensioned AFRP sheet were developed. From this study, following results were obtained: 1) applying the pretensioned AFRP sheet bonding method proposed here, the load-carrying capacity of the RC beams can be upgraded irrespective of the magnitudes of design parameters of the RC beam; 2) introducing the pretension force to the AFRP sheet, sheet debonding due to peeling action of the critical diagonal cracks can be more restrained; and 3) an empirical prediction equation for failure mode of the flexural reinforced RC beam with pretensioned AFRP sheet was proposed which is composed of calculated two bending moments at rebar yielding and the ultimate state.
STUDY ON DYNAMIC SHEAR RESISTANCE OF RC BEAMS BASED ON DYNAMIC MODIFIED COMPRESSION FIELD THEORY
Amornthep SOMRAJ, Kazunori FUJIKAKE and Bing LI
Vol. 72, No. 2, pp. 181-195, Journal of JSCE (Division E2) (in Japanese)
Abstract:
In order to examine safety over over shear failure of RC beams subjected to impact loadings, it is essential to investigate the influence of loading rate on the shear resistance of RC beams and to develop an analytical model to evaluate it. Therefore, this paper initially presents an experimental investigation through rapid loading tests for RC beams with a shear span-to-depth ratio of 3.3 to clarify the effects of loading rates and shear reinforcement ratios on the failure modes and ultimate resistance of the RC beams. It was found that the RC beams without shear reinforcement exhibited diagonal tension shear failure under all the loading rates, while the failure modes were changed from brittle shear failure to ductile flexure failure by increasing the shear reinforcement ratios. The influence of loading rates on the ultimate resistance of the RC beams was more significant in shear failure than in flexure failure. Subsequently, well-known Modified Compression Field Theory (MCFT) developed under static loading was extended to the dynamic loading to evaluate the dynamic shear resistance of RC beams. The developed dynamic MCFT was justified by comparing with the experimental data. Finally it was found that the dynamic increase ratios in the shear resistance of RC beams calculated from the dynamic MCFT were consistent with those in the dynamic shear strength of concrete.
EFFECTS OF REINFORCING BACK SURFACE OF CONCRETE PLATES ON LOCAL DAMAGE CAUSED BY EXPLOSIVE LOAD
Hiroyoshi ICHINO, Makoto NAGATA, Masuhiro BEPPU and Tomonori OHNO
Vol. 72, No. 2, pp. 146-164, Journal of JSCE (Division E2) (in Japanese)
Abstract:
To establish a protective design for concrete structures, the explosive-resistant performance of concrete plates and the reinforced back surface of concrete plates were experimentally examined. In this study, explosion tests are conducted to examine the failure modes of concrete plates subjected to the contact explosion and the close-in explosion. Fiber sheet or polymer coating is used for the reinforcement of back surface of concrete plate. Generally, fiber sheet has high strength (high elastic modulus) and polymer coating has high braking strain. From test results, it is found that the reinforcement employed for these materials has remarkable effectiveness to reduce the local damage of concrete plates. Moreover, reinforcement of back surface can prevent the scattering of concrete fragment. The effect of reinforcement is formulated as a function of tensional stiffness of materials.