Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korea Concrete Institute
Journal Basic Information
Journal DOI :
Korea Concrete Institute
Editor in Chief :
Volume & Issues
Volume 23, Issue 6 - Dec 2011
Volume 23, Issue 5 - Oct 2011
Volume 23, Issue 4 - Aug 2011
Volume 23, Issue 3 - Jun 2011
Volume 23, Issue 2 - Apr 2011
Volume 23, Issue 1 - Feb 2011
Selecting the target year
Fatigue Behavior of Prestressed Concrete Beams Using FRP Tendons
Kim, Kyoung-Nam ; Park, Sang-Yeol ; Kim, Chang-Hoon ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 135~144
DOI : 10.4334/JKCI.2011.23.2.135
Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam`s safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam`s static strength, respectively.
Study on Hydration Heat of Blended Belite Binder
Lee, Kewn-Chu ; Cho, Jae-Woo ; Jung, Sang-Hwa ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 145~150
DOI : 10.4334/JKCI.2011.23.2.145
Presently, mass concrete structures are being built in federal and private projects of civil infrastructures and building structures. The hydration heat of mass concrete structures is the most important factor in the quality of concrete matrix and construction period. Moreover, internal cracks caused by hydration heat degrades durability, water tightness, and strength of concrete. To reduce hydration heat, it is necessary to blend belite cement (
) with industrial by-products (i.e. granulated slag and fly ash). In this experiment, 14 levels of binary binders and 4 levels of ternary binders were used to understand the effect of different replacement ratio on hydration heat, strength and microstructure (i.e. SEM and XRD) of mortar. Cumulative hydration heat at 28 days for the binary and ternary binders was affected by replacement ratio of fly ash and/or granulated slag. As fly ash content increased, hydration heat decreased. As granulated slag content increased, reduction rate of the hydration heat was lower than when fly ash was used. Especially, the hydration heat of ternary binder blended with 40% flyash and 30% granulated slag showed about 50% of hydration heat from using belite cement (P). The study results showed that the temperature rise of concrete matrix can be decreased by using blended belite binders producing low hydration heat and reasonable strength.
Properties of Bubble According to Types and Concentrations of Concrete Foaming Agent
Kim, Jin-Man ; Kwak, Eun-Gu ; Oh, Kwang-Chin ; Kang, Cheol ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 151~158
DOI : 10.4334/JKCI.2011.23.2.151
Bubbles within the foamed concrete manufactured by pre-foaming method is the main factor which affects the physical properties of foamed concrete such as density, strength, and porosity. Although many researches on foamed concrete have been continuously carried out, insufficient number of researches on the properties related to bubbles in the foamed concrete has been performed except for chemical application related researches. In order to make an optimal foamed concrete, study on the bubble properties must be pursued. In order to effectively implement bubbles in the manufacturing of foamed concrete, the bubble properties must be estimated. In this study, in order to determine the bubble properties, examination of the bubble properties according to types and foaming agent concentration was performed. An foaming agent used for this test were anionic surfactant, rosin, and protein system with the foaming agent concentration range of 0.05~13%. Test parameters considered in the study were foaming rate, foam volume, drainage solution volume, and bubble size. The study results showed that, regardless of foaming agent type, higher concentration of foaming agent showed an increase in the foaming rate. Also, the results showed that concentration of foaming agent affected bubble size, drainage solution volume change, and bubble distributions. With respect to the stability of the bubble, protein foaming agent was better than anion surfactant or rosin foaming agent. With respect to the bubble shape, anion surfactant and rosin formed bubbles had polygon shape where as protein formed bubbles had spherical shape.
Direct Punching Shear Strength Model for Interior Slab-Column Connections and Column Footings with Shear Reinforcement
Choi, Kyoung-Kyu ; Kim, Sug-Hwan ; Kim, Dong-Hoon ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 159~168
DOI : 10.4334/JKCI.2011.23.2.159
In the present study, an improved design method was developed for the punching shear strength of interior slabcolumn connections and column footings with and without shear reinforcement. In the evaluation of the punching shear strength, the possible failure mechanisms of the connections and column footings were considered. The considered failures modes were inclined tensile cracking of concrete, yielding of shear re-bars, and concrete crushing of compression zone/strut. The punching shear applied to the concrete critical section was assumed to be resisted mainly by the compression zone. The punching shear strength of the concrete compression zone was evaluated based on the material failure criteria of the concrete subjected to the compressive normal stress and shear stress. For verification of the proposed design method, its prediction was compared with the existing test results. The result showed that the proposed method predicted the strengths of the test specimens better than the current design methods of the KCI code for both the shear reinforced and unreinforced cases.
Flexural Behavior of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) Beam with a Reinforcing Bar
Shin, Kyung-Joon ; Kim, Jae-Hwa ; Cho, Jae-Yeol ; Lee, Seong-Cheol ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 169~176
DOI : 10.4334/JKCI.2011.23.2.169
In this study, the flexural test for reinforced high performance fiber reinforced cementitious composites (R/HPFRCC) members has been conducted in order to investigate the flexural behavior including the effect of an ordinary tensile reinforcing bar. Through the test, it was observed that the flexural strength increased due to the stable tensile stress transfer of HPFRCC, even up to the ultimate state. In addition, no localized crack appeared until the yielding of the reinforcement. From the layered section analysis of the tested members, it was found that the analysis with the tensile model obtained from the tension stiffening test showed better agreement with the flexural test results, whereas the analysis with direct tension test results overestimated the flexural capacity. Through the experimental and analytical studies, two flexural failure modes have been defined in this paper; concrete crushing at the top compression layer or tensile failure at the bottom tensile layer of the beam section. Based on these two flexural failure modes, a simple formula that estimates the ultimate flexural strength of the member has been proposed in this paper. The proposed equations can be useful in a design and an analysis of R/HPFRCC members.
Nonlinear Analysis for Negative Moment Distribution of MRS Slab End Joints
Moon, Jeong-Ho ; Oh, Young-Hun ; Lim, Jae-Hyung ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 177~184
DOI : 10.4334/JKCI.2011.23.2.177
This paper describes an analytical study on the design approach of PC system with continuous connections at member ends. In multi-ribbed moment resisting slab (MRS) system, double tee members are connected continuously over inverted tee beams with the continuous reinforcements placed within topping concrete. Thus, negative moments are concentrated within the narrow connection area. In order to propose a design method, experimental results of the companion study were examined using detailed nonlinear analysis. Then nonlinear static analysis was used to evaluate the partial continuity effect and the moment redistribution mechanism. Material and cross sectional properties were obtained from experimental results of the companion study. Plastic hinge properties for nonlinear static analysis were modeled with cracking moment, nominal moment, corresponding member deformations, etc. The analysis results showed that a large amount of negative moment of MRS slab can be reduced by applying partial continuity and moment redistribution in MRS joint.
Shear Strength Model for FRP Shear-Reinforced Concrete Beams
Choi, Kyoung-Kyu ; Kang, Su-Min ; Shim, Woo-Chang ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 185~193
DOI : 10.4334/JKCI.2011.23.2.185
In the present study, a unified shear design method was developed to evaluate the shear strength of concrete beams with and without FRP shear reinforcement. The contributions of FRP and concrete on shear strength were defined separately. By comparing the current design method calculated results with the existing test results, it was found that Triantafillou model shows a reliable prediction of FRP effective strain and FRP shear strength contributions. The concrete shear strength contribution was defined by the strain-based shear strength model developed in the previous study. The shear strength of concrete compression zone was evaluated based on the material failure criteria of the concrete subjected to the compressive normal and shear stresses. The proposed strength model was verified by comparing its prediction results to prior test results. The comparisons showed that the proposed method accurately predicts the strengths of the test specimens for both FRP shear reinforced and unreinforced concrete beams.
Experimental Study on Behavior of Confined Concrete with Electric Arc Furnace Oxidizing Slag Aggregates
Kim, Sang-Woo ; Lee, Jung-Mi ; Lee, Yong-Jun ; Jung, You-Jin ; Kim, Kil-Hee ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 195~201
DOI : 10.4334/JKCI.2011.23.2.195
This paper estimates the structural performance of spirally confined concrete having electric arc furnace (EAF) oxidizing slag aggregates. The EAF oxidizing slag is a by-product generated from iron and steel industry. The EAF oxidizing slag have been largely put to low-value-added uses due to its expansive properties of the free-CaO and free-MgO. Recently, this problem has been solved by the advances in steelmaking technology and thereby stabilizing EAF oxidizing slag aggregate. To verify the application of the EAF oxidizing slag aggregate to the structural concrete usage, a total of 27 cylindrical specimens with a diameter of 150 mm and a height of 300 mm were cast and tested. The test parameters were aggregate type and spiral reinforcement yield strength. Experimental results showed that the structural performance of specimens with EAF oxidizing slag aggregates was equivalent to that of confined concrete with natural aggregates.
A Fundamental study on the Characteristics of Zeolite Cement Mortar
Jo, Byung-Wan ; Kang, Suk-Won ; Park, Seung-Kook ; Choi, Ji-Sun ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 203~209
DOI : 10.4334/JKCI.2011.23.2.203
The cement industry is expected to face a major set-back in the near future due to its large energy consumption and
production, causing global warming. In order to overcome these environmental problems, this research has bee carried out to find a cement substitute material. One possible cement substitute material is Zeolite cement. In this study, the materialistic characteristics of Zeolite cement mortar were evaluated. Natural Zeolite cement mortar was prepared using alkali activation (NaOH) instead of water (
) to determine achievable strength and appropriate mixing ratio. Based on the mixing ratio, functional material was added to alkali active agent to harden Zeolite mortar to develop a highly functional construction material. The study result showed that pure Zeolite cement mortar achieved compressive strength of 42 MPa in 7 days depending on the mixing amount of alkaline catalyst and the hardening temperature, showing high efficiency and possibility as a new construction material.
Design Equations of Compression Splice Strength and Length in Concrete of 100 MPa and Less Compressive Strength
Chun, Sung-Chul ; Lee, Sung-Ho ; Oh, Bo-Hwan ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 211~217
DOI : 10.4334/JKCI.2011.23.2.211
Although a compression splice length does not need to be longer than a tension splice length due to end bearing effect, current design codes impose a longer compression lap splice than a tension lap splice in high strength concrete. Hence, new criteria for the compression lap splice including concrete strength effect need to be found for economical design of ultra-high strength concrete. An experimental study has been conducted using column specimens with concrete strength of 80 and 100 MPa with transverse reinforcement. The test results showed that splice strengths improved when the amount of transverse reinforcement increased. However, end bearing strength did not increase when larger amount of transverse reinforcement is provided within the spliced zone. Therefore, the splice strength enhancement was attributed to the improvement of bond. From regression analysis of 94 test results including specimens made with concrete strength of 40 and 60 MPa, a new design equation is proposed for compression lap splice in the concrete compressive strength ranging from 40 to 100 MPa with transverse reinforcement. By using the proposed equation, the incorrect design equations for lap splice lengths in tension and compression can be corrected. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.
A Study on Applicability of Embedded Smart Sensor for Concrete Curing Monitoring
Park, Seung-Hee ; Kim, Dong-Jin ; Hong, Seok-Inn ; Lee, Chang-Gil ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 219~224
DOI : 10.4334/JKCI.2011.23.2.219
In this study, a piezoelectric smart sensor that can be embedded inside of concrete structures is developed to investigate the early stage of concrete curing. A waterproof coating is used to protect the piezoelectric sensor from moistures of concrete mixture. Also, a mortar case is utilized to encapsulate the sensor to protect it from impact loads. To estimate the strength of concrete, a self-sense guided-wave actuated sensing technique is applied. In the guided wave, its velocity is varied according to the mechanical properties of concrete such as modulus of elasticity. Because modulus of elasticity directly affects the strength of concrete, the guidedwave`s velocity also affects the concrete strength development. To verify the feasibility of using the proposed approach, the smart sensor was embedded into a 100MPa concrete cylinder and the self-sense guided wave is continuously measured throughout the curing process. The measurements showed that the propagation time (TOF) of the measured guided waves gradually decreased as the curing age increased. Especially, at the early age of the curing process, the variation of the TOF was very significant. Furthermore, the results showed that there is a linear relationship between the TOF of the self-sense guided waves and the strength of concrete existed. It is safe to conclude that the proposed approach can be used very effectively in monitoring of the strength development of high strength concrete structures.
Fundamental Properties of Cement Composites Containing Lightly Burnt MgO Powders
Jang, Bong-Seok ; Kwon, Yong-Gil ; Choi, Seul-Woo ; Lee, Kwang-Myong ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 225~233
DOI : 10.4334/JKCI.2011.23.2.225
The volume change in concrete takes place with changes in temperature and water content immediately after concrete casting. In the early age stage, the thermal and drying shrinkages can cause cracks that are very crucial to the durability of concrete. It was reported that when the cement with lightly-burnt MgO powder was used, the shrinkage of concrete can be reduced. This study investigates fundamental properties of cement composites with lightly burnt MgO powder by performing various experiments. The stability test results verified that MgO powder in cement composites does not cause any abnormal expansion. Also, the hydrate product analysis results obtained from MgO cement paste showed that MgO powder reduces the shrinkage at the longterm ages. In addition, the cement composites containing the proper amount of MgO powder could improve compressive strength. Finally, the shrinkage reduction from using MgO powder can be optimized by increasing MgO replacement level and curing temperature.
An Experimental Study on the Joints in Ultra High Performance Precast Concrete Segmental Bridges
Lee, Chang-Hong ; Chin, Won-Jong ; Choi, Eun-Suk ; Kim, Young-Jin ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 235~244
DOI : 10.4334/JKCI.2011.23.2.235
Failures of segmental bridges have been attributed to the inadequate joint connection techniques, which led to corrosion of the post-tensioned tendons connecting the segmental joints. The principal objective of this study is to evaluate the performances of the in-situ cast joint and epoxy applied shear key joints as a function of shear and ultimate strengths. Furthermore, shear behavior and strength of shear key joints in ultra high performance precasted concrete segmental bridges are experimentally evaluated to understand its shear failure behavior. The test parameters of shear key shape and type, load-displacement relations, cracking behavior, concrete strength, and fracture modes are considered in the study. Also, several parameters which influence the mechanical behavior of the shear key joint are analyzed. Based on the study results, the optimal shear key shape and joint type are proposed for the joint design and analysis guidelines.
Evaluation for Progressive Collapse Resistance of a RC Flat Plate System Using the Static and Dynamic Analysis
Lee, Seon-Woong ; Shin, Sung-Woo ;
Journal of the Korea Concrete Institute, volume 23, issue 2, 2011, Pages 245~252
DOI : 10.4334/JKCI.2011.23.2.245
Currently, the design guidelines for the prevention of progressive collapse are not available in Korea due to the lack of study efforts in progressive collapse resistance evaluation of RC flat plate system. Therefore, in this study, three types of analysis were conducted to evaluate the progressive collapse resistance of a RC flat plate system. A linear static analysis was carried out by comparing the demand-capacity ratio (DCR) differences of the systems using the alternate load path method, which is the guideline of GSA. A dynamic behavior was investigated by checking the vertical deflection after removal of the column using the linear dynamic analysis. Lastly, a maximum load factor was investigated using the nonlinear static analysis. The finite element (FE) analyses were conducted using various parameters to analyze the results obtained using effective beam width (EB) model and plate element FEM (PF) model. This study results showed that the strength contributions of the slab in the EB models are underestimated compared to those obtained from the PF models. Therefore, a detailed FE analysis considering the slab element is required to thoroughly estimate the progressive collapse resisting capacity of flat plate system. The scenario of the corner column (CC) removal is the most dangerous conditions where as the scenario of the inner column (IC) removal is the least dangerous conditions based on the consideration of various parameters. The analysis results will allow more realistic evaluations of progressive collapse resistance of RC flat plate system.