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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Concrete Institute
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Korea Concrete Institute
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Volume & Issues
Volume 22, Issue 6 - Dec 2010
Volume 22, Issue 5 - Oct 2010
Volume 22, Issue 4 - Aug 2010
Volume 22, Issue 3 - Jun 2010
Volume 22, Issue 2 - Apr 2010
Volume 22, Issue 1 - Feb 2010
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Seismic Performance of Precast Beam-Column Joints with Thru-Connectors
Park, Soon-Kyu ; Kim, Min-Hee ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 441~450
DOI : 10.4334/JKCI.2010.22.4.441
This is a preliminary study on the development of precast beam-column joints for dry construction methodology. Precast beam column joints with thru-connectors (BCJ_TC) using high strength bars or PS strands were developed and their seismic performance including strength degradation, stiffness degradation and energy dissipation capacity was experimentally evaluated. Test results showed that compressive failures at the end blocks of PC beam members occurred dominantly while PC columns including panel zones were free from any damage. However, the connections confined with CFRP at the end block showed much improved seismic performance than that of the unconfined connections. Connections with neoprene pad fillers between beam and column interfaces were better than the other connections in all the seismic performances except initial stiffness. To improve the seismic performances of BCJ_TC, compressive strength of the concrete at the end block need to be increased to compensate for the additional compressive stresses due to unbonded connectors and deformation of connectors should be controlled respectively.
Shear Strength Reduction Ratio of Reinforced Concrete Shear Walls with Openings
Bae, Baek-Il ; Choi, Yun-Cheul ; Choi, Chang-Sik ; Choi, Hyun-Ki ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 451~460
DOI : 10.4334/JKCI.2010.22.4.451
There are many types of remodeling, however, engineers and architectures preferred to merge two or more separate units to one very spacious unit. Performing this type of remodeling, in the case of wall dominant apartments, requires partial removal of structural wall causing a concern of structural integrity. However, there are insufficient studies about partial removal, that is, openings. Presently, ACI standard have no clear way to evaluate the effect of opening on the structural wall. AIJ has the provision about strength reduction factor `
`. However, this reduction factor cannot exactly evaluate the reduction effect of openings because this factor `
` was determined through the elastic analysis. Therefore, in this study, 2 structural wall specimens were tested and many test results from previous studies were collected. Using these data, this study performed statistical analysis about strength of structural wall which have the opening in wall panel. And this study performed parametric study verifying shear strength reducing effect by opening area. In the results of statistical study, previous reduction factor show very conservative results because this equation did not consider other factors, reinforcement ratio and aspect ratio of openings, which was affect the shear strength of shear walls. Therefore we performed parametric study based on the test data and suggest new equation for shear strength reduction factor `
Behavior of Precast Concrete Shear Walls with C-Type Connections
Lim, Woo-Young ; Hong, Sung-Gul ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 461~472
DOI : 10.4334/JKCI.2010.22.4.461
This paper investigates the behavior of precast concrete (PC) shear walls with a new vertical connections for a fast remodeling construction. The C-type vertical connections for the PC wall systems are proposed for transfer of bending moment between top and bottom walls in the vertical direction while a shear key in the center of wall is prepared to transfer shear forces by bearing action. The proposed vertical connections allows easy fabrication thanks to slots at the edges of wall in opposite directions. The plane PC wall systems subject to lateral load are compared with ordinary wall systems by investigating the effects of connection on the stiffness, strength, ductility, and failure modes of whole systems. The load-displacement relationship and influence of premature failure of connections are examined. The experimental test showed that the longitudinal reinforcing steel bars placed at the edges of walls yielded first and the ultimate deformation were terminated due to premature failure of connections. The diagonal reinforcements for efficient shear transfer in the walls were not effective. The strength and deformation obtained through the section analysis were generally in agreement with the experimental data, and indicated that. Gap opening contributed to the deformation behavior more than any other factors.
Effect of Fiber Types on Fundamental Properties of Pavement Concrete
Han, Cheon-Goo ; Park, Jong-Sup ; Jung, Woo-Tai ; Jeon, Kyu-Nam ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 473~479
DOI : 10.4334/JKCI.2010.22.4.473
The objective of the paper is to experimentally investigate the effect of commercially avaliable fiber types such as polypropylene (PP), nylon (NY), polyvinyl alcohol (PVA) and cellulose (CL) on the engineering properties of concrete for pavement application. The results, showed the fluidity tends to decrease with fibers addition compared to that of plain concrete. As for the effect of fiber types on fluidity loss, use of NY appear to give the most favorable results among all of the fiber types investigated in this study while the effect of the fibers on air content was negligible. For the properties of hardened concrete, compressive and flexural strengths increased with fibers compared to plain concrete. The contribution of NY fibers to strength was the highest followed in the order by NY, PVA, PP, and CL. However, in the case of the splitting tensile strength, its values were increased with NY and PP only. For porosity based on MIP(mercury intrusion penetration) method, the number of around 1 was observed when NY was mixed resulting in increased cumulated amounts of porosity compared with that of plain mix. Thus, based on the consideration of fluidity and strength it was found that the addition of NY fiber showed the optimal results under the conditions applied in this study.
Constitutive Model of Laterally Confined High Strength Concrete
Yun, Sung-Hwan ; Kang, Yoon-Sig ; Park, Tae-Hyo ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 481~488
DOI : 10.4334/JKCI.2010.22.4.481
Since existing constitutive models developed for confined normal strength concrete overestimate ductility when they are applied to confined high strength concrete, these models cannot be directly applied to confined high strength concrete. In an effort to solve this problem, an accurate stress-strain relationship of the hihg strength concrete needs to be formulated by examining the confinement effects due to increase of the concrete strength. In this study, a constitutive model is developed to express the stress-strain relationship of confined high strength concrete by carrying out regression analysis of the main parameters affection strength and ductile behavior of reinforced high strength concrete columns. Twenty-five test specimens were chosen from the reported experimental studies in the literature. The experimental results of stress-strain relationships of show a good agreement with results of the stress-strain relationships of suggested high strength concrete, covering a strength range between 60 and 124 MPa.
Behavior of Columns Due to Variation of Performance Influencing Factors Based on Performance Based Design
Yun, Sung-Hwan ; Choi, Min-Choul ; Kang, Yoon-Sig ; Park, Tae-Hyo ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 489~498
DOI : 10.4334/JKCI.2010.22.4.489
The performance evaluation of reinforcement concrete structure is carried out as a function of the following performance influencing factors: (1) the strength of concrete, (2) longitudinal reinforcement, (3) transverse reinforcement, (4) aspect ratio, and (5) axial force. With various values of the five parameters, eigenvalue analysis and non-linear static analysis were performed to investigate the structural yield displacement, yield basis shear force, and static performance of ductility ratio. In addition, the performance evaluation is carried out according to the modified capacity spectrum method (FEMA-440) using the results of non-linear static analysis, and the effect of each parameter on performance point is analyzed. Based on the result of eigenvalue analysis and non-linear static analysis indicates, that the natural period and the ductility ratio are affected more by the structural properties than the material properties. In case of the analysis of the criterion of performance points, the effect of section shape is one of the important factors together with natural period and ductility ratio.
Development of Performance Based Mix Design Method Using Single Parameter Bayesian Method
Kim, Jang-Ho Jay ; Phan, Hung-Duc ; Oh, Il-Sun ; Lee, Keun-Sung ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 499~510
DOI : 10.4334/JKCI.2010.22.4.499
This paper presents a systematic approach for estimating material performance and designing mix proportion of concrete based on an application of Bayesian method in the form of satisfaction curves. The one-parameter satisfaction curve represents a satisfaction probability of a concrete performance criterion as a function of concrete material parameter. An analysis method to combine multiple satisfaction curves to form one unique satisfaction curve that can relate the performance of concrete to a single evaluating value called Goodness value is proposed. A proposed PBMD procedure and examples of application of the PBMD method for concrete mix proportion design are carried out to verify the validity of the proposed method. Finally, the comparison between the expected performance results of a concrete mix proportion designed using PBMD to the ACI estimation equation calculated results are performed to check the applicability of the method to actual construction.
Analytical Study on the Shear Behavior of Prestressed Concrete Deep Beams
Kim, Tae-Hoon ; Kim, Young-Jin ; Shin, Hyun-Mock ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 511~517
DOI : 10.4334/JKCI.2010.22.4.511
The purpose of this study is to investigate the shear behavior of prestressed concrete deep beams and to provide the data for development of improved design criteria. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. Hence, in this study, the computer program, named RCAHEST (reinforced concrete analysis in higher evaluation system technology), was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. A bonded or unbonded tendon element based on the finite element method, that can represent the interaction between tendon and concrete of prestressed concrete member, is used. The proposed numerical method for the shear behavior of prestressed concrete deep beams is verified by comparing the analytical results with test data by others.
Development and Splice Lengths of FRP Bars with Splitting Failures
Chun, Sung-Chul ; Choi, Dong-Uk ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 519~525
DOI : 10.4334/JKCI.2010.22.4.519
Data from beam-based bond tests for FRP bars in the literature were collected and regression analyses were conducted for the data of splitting failure. Average bond strengths obtained from splice tests were found to be lower and more affected by C/
values than average bond strengths from anchorage tests, indicating needs of new design equation for the splice length of FRP bars based on the data of splice tests only. In addition, the variation of bond strengths was greater than that of tensile strengths of FRP bars and, therefore, a new safety factor should be involved for the design equation. Five percent fractile coefficients were used to develop the design equations based on the assumption that load and resistance factors for FRP reinforced concrete structures are same to the factors for steel reinforced concrete structures. The proposed design equations give economical and reliable lengths for development and splice of FRP bars. The proposed equation for splice provides shorter lengths than the ACI 440 equation in case of C/
of 3.0 or greater. Because FRP bars are expected to be used in slabs and walls exposed to weather with thick cover and large spacing between bars, the proposed equation gives optimal splice lengths.
Experimental Study on Improvement of Bond Performance of RC Beams with High-Strength Shear Reinforcement
Kim, Sang-Woo ; Kim, Do-Jin ; Yoon, Hye-Sun ; Baek, Sung-Cheol ; Kim, Kil-Hee ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 527~534
DOI : 10.4334/JKCI.2010.22.4.527
This study presents a simple method to improve the bond performance of reinforced concrete (RC) beams having high-strength shear reinforcement. In general, the yield strength and the ratio of shear reinforcements are the main parameters governing the shear capacity of RC beams. The yield strength of shear reinforcement, however, has little influence on the bond capacity of RC beams. Therefore, a sudden bond failure of the members with high-strength shear reinforcement can occur before flexural failure. To estimate the structural performance of the proposed method, four RC beams were cast and tested. The main test parameters were the yield strength, ratio, and reinforcing types of shear reinforcements. The experimental results indicated that the proposed method was able to effectively improve the bond performance of RC beams with high-strength shear reinforcement.
Development of Performance Based Resistance Capacity Evaluation Method for RC Compression Member under Vehicle Impact Load
Kim, Jang-Ho Jay ; Yi, Na-Hyun ; Phan, Duc-Hung ; Kim, Sung-Bae ; Lee, Kang-Won ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 535~546
DOI : 10.4334/JKCI.2010.22.4.535
Recently, the probability of collision accident between vehicles or vessels and infrastructures are increasing at alarming rate. Particularly, collision impact load can be detrimental to sub-structures such as piers and columns. The damaged pier from an impact load of a vehicle or a vessel can lead to member damages, which make the member more vulnerable to impact load due to other accidents which. In extreme case, may cause structural collapse. Therefore, in this study, the vehicle impact load on concrete compression member was considered to assess the quantitative design resistance capacity to improve, the existing design method and to setup the new damage assessment method. The case study was carried out using the LS-DYNA, an explicit finite element analysis program. The parameters for the case study were cross-section variation of pier, impact load angle, permanent axial load and axial load ratio, concrete strength, longitudinal and lateral rebar ratios, and slenderness ratio. Using the analysis results, the performance based resistance capacity evaluation method for impact load using satisfaction curve was developed using Bayesian probabilistic method, which can be applied to reinforced concrete column design for impact loads.
Development of Self-Repairing Smart Concrete Using Micro-Biologically Induced Calcite Precipitation
Kim, Wha-Jung ; Ghim, Sa-Youl ; Park, Sung-Jin ; Choi, Kil-Jun ; Chun, Woo-Young ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 547~557
DOI : 10.4334/JKCI.2010.22.4.547
This paper presents a study on the development of next generation smart concrete in an eco-friendly manner using micro-biologically induced calcite precipitation (MICP) via microbial biomineralization. It seems that currently, the reformation and functional improvement of concrete using MICP can be achieved using Sporosarcina pasteurii, which is a representative microorganism that produces calcite precipitation. Based on previous studies on MICP the biochemical tests and crystallinity evaluation of cement using sporoasrcina pasteurii and four additional micro-organisms from the concrete structures as identified by 16S rDNA sequence analysis were conducted. Also by applying the Sporosarcina pasteurii and separated four effective micro-organisms from the concrete structures to mortar, the compressive strength improvement by varying curing conditions, repair of crack were examined, and plans for future study were suggested. The effect of the application of effective micro-organisms can lead to the development of a new material that will contribute to resolution of environmental problems and facilitate repair work, and this can also serve as a new research theme in the future. In addition, the importance of this study is to use micro-organism, which is found common in concrete structures, this new microbial is not only environmentally safe but also persists in the natural environment for an extended period of time. Therefore, it seems to have a great potential to became a new environmentally low-burdened functional material.
Air Content, Workability and Bleeding Characteristics of Fresh Lightweight Aggregate Concrete
Sim, Jae-Il ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 559~566
DOI : 10.4334/JKCI.2010.22.4.559
Fifteen lightweight concrete mixes were tested to evaluate the effect of maximum size of coarse aggregate and the replacement level of natural sand on the various properties of fresh lightweight concrete. The different properties, such as water absorption against the elapsed time, pore size distribution and micro-structure of lightweight aggregates used, influencing on the workability of fresh concrete were also measured. Test results showed that the initial slump of lightweight concrete decreased with the increase of the replacement level of natural sand. The slump of all-lightweight concrete sharply decreased by around 80% of the initial slump after 30~60 minutes. The air content and bleeding rate of lightweight concrete were significantly affected by the replacement level of natural sand as well as the maximum size of coarse aggregates. Empirical equations recommended in ACI 211 and Korea concrete standard specifications underestimated the air content of the lightweight concrete, indicating that the underestimation increases with the decrease of the replacement level of natural sand. In addition, equations to predict the air content and bleeding rate of lightweight concrete were proposed based on the test results.
Flexural Performance of Activated Hwangtoh Concrete Beam
Lee, Nam-Kon ; Hwang, Hye-Zoo ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 567~574
DOI : 10.4334/JKCI.2010.22.4.567
As a eco-friendly material, Hwangtoh(red clay) has been studied for a partial or complete replacement of portland cement. Most of existing studies focused on the mechanical properties of the Hwangtoh concrete including the compressive strength, drying shrinkage, creep. In the present study, the flexural capacity of the beams made with the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated Hwangtoh replacing all the cement. The simple beams were tested under two point static loading. The flexural strength, cracking moment, deflection, and ductility were compared with those of the beams made with ordinary portland cement concrete.
Influence of Number of Twist on Tensile Behavior of High Performance Fiber Reinforced Cementitious Composites with Twisted Steel Fibers
Kim, Dong-Joo ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 575~583
DOI : 10.4334/JKCI.2010.22.4.575
This research investigated the influence of the number of twist on single fiber pullout behavior of Twisted steel (T-) fiber and tensile behavior of high performance cementitious composites reinforced with the (T-) fibers (HPFRCC). Micromechanical pullout model for T- fibers has been applied to analytically investigate the influence of various fiber parameters including the number of twist on single fiber pullout behavior; and, to optimize the number of twist to generate larger pullout energy during fiber pullout without fiber breakage. In addition, an experimental program including single fiber pullout and tensile tests has been performed to investigate the influence of twist ratio experimentally. Two types of T- fiber with different twisted ratios, T(L)- fiber (6ribs/30 mm) and T(H)- fiber (18ribs/30 mm), were tested. T(L)- fiber produced higher equivalent bond strength (larger pullout energy) although T(H)- fiber produced higher pullout stress during pullout since T(H)- fiber showed fiber breakage during pullout. Tensile test results confirmed that T(L)- fiber in high strength mortar generates better tensile performance of HPFRCC, e.g., load carrying capacity, strain capacity and multiple micro-cracking behavior.
Shear Strength Model for Slab-Column Connections
Choi, Kyoung-Kyu ; Park, Hong-Gun ; Kim, Hye-Min ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 585~593
DOI : 10.4334/JKCI.2010.22.4.585
On the basis of the strain-based shear strength model developed in the previous study, a strength model was developed to predict the direct punching shear capacity and unbalanced moment-carrying capacity of interior and exterior slab-column connections. Since the connections are severely damaged by flexural cracking, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the compressive normal stress developed by the flexural moment, the shear strength of the compression zone was derived on the basis of the material failure criteria of concrete subjected to multiple stresses. As a result, shear capacity of the critical section was defined according to the degree of flexural damage. Since the exterior slab-column connections have unsymmertical critical sections, the unbalanced moment-carrying capacity was defined according to the direction of unbalanced moment. The proposed strength model was applied to existing test specimens. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods.
Reliability-Based Service Life Estimation of Concrete in Marine Environment
Kim, Ki-Hyun ; Cha, Soo-Won ;
Journal of the Korea Concrete Institute, volume 22, issue 4, 2010, Pages 595~603
DOI : 10.4334/JKCI.2010.22.4.595
Monte-Carlo simulation technique is often used in order to predict service life of concrete structure subjected to chloride penetration in marine environment based on probability theory. Monte-Carlo simulation method, however, the method gives different results every time that the simulation is run. On the other hand, moment method, which is frequently used in reliability analysis, needs negligible computational cost compared with simulation technique and gives a constant result for the same problem. Thus, in this study, moment method was applied to the calculation of corrosion-initiation probability. For this purpose, computer programs to calculate failure probabilities are developed using first-order second moment (FOSM) and second-order second moment (SOSM) methods, respectively. From the analysis examples with the developed programs, SOSM was found to give a more accurate result than FOSM does. The sensitivity analysis has shown that the factor affecting the corrosion-initiation probability the most was the cover depth, and the corrosion-initiation probability was influenced more by its coefficient of variation than its mean value.