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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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Journal DOI :
Korea Concrete Institute
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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
Evaluation for Applicability of Reinforced Concrete Structure with Domestic Pond Ash
Lee, Bong-Chun ; Jung, Sang-Hwa ; Chae, Sung-Tae ; Kwon, Seung-Jun ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 541~550
DOI : 10.4334/JKCI.2011.23.5.541
Many researches have been performed on concrete with fly ash and bottom ash. However researches on concrete with pond ash (PA) and its application to RC (Reinforced Concrete) structure are limitedly carried out. This paper presents an applicability of PA concrete in construction of real size structure. Referring to the previous study, 2 domestic PA samples with normal performance are selected and 2 replacement ratios (25% and 50%) to fine aggregate are considered for 5 PA concrete structures consisting of column, slab, and wall. In order to evaluate the property of fresh concrete, several tests including air content, slump, and setting time are performed. Using cored out samples from hardened PA concrete structure, tests for strength, resistance to carbonation and chloride penetration are carried out and compared with control samples. Additionally, tests for rebound hardness, drying shrinkage, and hydration heat are performed for PA concrete structure. The test results showed that PA concrete has reasonable strength and durability performances compared to those of normal concrete. Therefore, its potential application to RC structure is promising. The PA aggregate can be more actively used for RC structures with better quality control for content of fly ash, bottom ash, and unburned carbon.
Mechanical Properties of Lightweight Aggregate Concrete according to the Substitution Rate of Natural Sand and Maximum Aggregate Size
Sim, Jae-Il ; Yang, Keun-Hyeok ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 551~558
DOI : 10.4334/JKCI.2011.23.5.551
The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.
Evaluation of Minimum Extensibility Standard Requirements for Steel Reinforcement
Lee, Jae-Hoon ; Kim, Dong-Hyun ; Choi, Jin-Ho ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 559~567
DOI : 10.4334/JKCI.2011.23.5.559
Recently, many researches on high strength reinforcing steel have been conducted to construct optimum reinforced concrete structures. However, the studies have shown that high strength steel shows less elongation capacity than normal strength steel. Therefore, high strength reinforcing steel may not satisfy the minimum elongation requirement of current standards. Moreover, elongation measurements may be not standardized ones since each standard has its own requirements for minimum elongation and gage length. Therefore, the standards for reinforcing steel testing must be investigated to verify the validity of Korean Standard D 3504. This research aimed to compare the requirements for minimum elongation and gage length of the Korean, American, Japanese, European, and ISO Standards. Then, the study further investigated accuracy of the standards by tensile test of reinforcing steel. The study results showed that the Korean Standard has the strictest requirement. Based on the study results, the authors proposed modified minimum elongation requirements for general reinforcing steel and new requirements for seismic reinforcing steel.
Macro Model for Nonlinear Analysis of Reinforced Concrete Walls
Kim, Dong-Kwan ; Eom, Tae-Sung ; Lim, Young-Joo ; Lee, Han-Seon ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 569~579
DOI : 10.4334/JKCI.2011.23.5.569
Reinforced concrete walls subjected to cyclic loading show complicated inelastic behaviors varying with aspect ratio, re-bar detail, and loading condition. In the present study, a macro model for nonlinear analysis of reinforced concrete walls was developed. For exact prediction of inelastic flexure-compression and shear behaviors, the macro model of the wall was idealized with longitudinal and diagonal uniaxial elements. The uniaxial elements consist of concrete and re-bars. Simplified cyclic models for concrete and re-bars under uniaxial loading was used. For verification, the proposed model was applied to slender, lowrise, and coupled walls subjected to cyclic loading. The results showed that the proposed method predicted the nonlinear behaviors of the walls with reasonable precision.
Characteristics of Early-Age Restrained Shrinkage and Tensile Creep of Ultra-High Performance Cementitious Composites (UHPCC)
Yoo, Doo-Yeol ; Park, Jung-Jun ; Kim, Sung-Wook ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 581~590
DOI : 10.4334/JKCI.2011.23.5.581
Since ultra-high performance cementitious composites (UHPCC) not only represents high early age shrinkage strain due to its low water-to-binder ratio (W/B) and high fineness admixture usage but also reduces the cross section of structure from the higher mechanical properties, it generally has more shrinkage cracks from the restraints of formwork and reinforcing bars. In this study, free and restrained shrinkage experiments were conducted to evaluate the suitability of incorporating both expansive admixture (EA) and shrinkage reducing agent (SRA). The test results indi-cated that approximately 40~44% of free shrinkage strain was decreased. Also, the results showed that 35% and 47% of residual tensile stresses were relieved by synergetic effect of SRA and EA, respectively. Residual tensile stresses from ringtest were relaxed by approximately 61% and 64% of elastic shrinkage stresses due to SRA and EA, respectively, because of the tensile creep effect. Therefore, the creep effect should be considered to precisely estimate the restrained shrinkage behavior of concrete structures. The degree of restraint of UHPCC was approximately in the range of 0.78~0.85. The addition of combined EA and SRA showed minute influence on the degree of restraint. However, the effect decreased when thicker concrete ring was used. Tensile creep strains were measured and compared to the predicted values from 4-parametric prediction model considering time dependent restrained forces.
Seismic Performance of Beam-Column Connections for Special Moment Frame Using 600 MPa Flexural Reinforcement
Hwang, Hyeon-Jong ; Park, Hong-Gun ; Choi, Won-Seok ; Chung, Lan ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 591~601
DOI : 10.4334/JKCI.2011.23.5.591
An experimental study was performed to evaluate the seismic performance of beam-column connections using 600 MPa re-bars for beam flexural reinforcement. Three full scale specimens of interior beam-column connection and two specimens of exterior beam-column connection were tested under cyclic loading. The specimens were designed to satisfy the requirements of Special Moment Frame according to current design code. The structural performance of the specimens with 600 MPa re-bar were compared with that of the specimen with 400 MPa re-bars. The test results showed that bond-slip increased in the beam-column joint. However, the load-carrying capacity, deformation capacity, and energy dissipation capacity of the specimens with 600 MPa re-bar were comparable to those of the specimens with 400 MPa re-bars.
QR Code-Based Strength Labeling Techniques for Concrete Life-Cycle Quality Maintenance
Kim, Tae-Heon ; Kim, Dong-Jin ; Park, Seung-Hee ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 603~608
DOI : 10.4334/JKCI.2011.23.5.603
In recent years, numerous mega-sized and complex civil infrastructures are being constructed all over the world. Therefore, more precise construction and maintenance technologies are required for these complicated construction projects. Especially, exact strength measurement and curing process monitoring of the concrete structures are very crucial to confirm the safety and effectiveness of these complicated structures. In this paper, a new Quick Response (QR) code-based concrete strength labeling technique using embedded self-sensing monitoring system is introduced. It is important to note that the QR code-based concrete labeling technique enables easy access of the databases related to the concrete strength at anytime, anywhere, and any smart PC devices. Finally, by integrating the proposed QR code-based concrete labeling with the concrete strength databases already prepared at a designated web-server, a feasibility of the current system is investigated for a next generation concrete life-cycle quality maintenance.
Durability Characteristics of Concrete Containing Lightly Burnt MgO Powder
Choi, Seul-Woo ; Kim, Joo-Hyung ; Lee, Kwang-Myong ; Kwon, Yong-Gil ; Jang, Bong-Seok ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 609~615
DOI : 10.4334/JKCI.2011.23.5.609
MgO concrete containing lightly burnt MgO powder at
may have a long-term expansibility characteristic. Such expansibility of MgO concrete can compensate the shrinkage at later ages since the hydration of the MgO is very slow. However, the addition of MgO delays the initial hydration of cement and increases the setting time of cement. Also, the porosity and pore-size distribution of the MgO concrete are different from OPC concrete. Therefore, in order to use MgO in practice, both mechanical and durability properties of MgO concrete should be carefully examined. In this study, durability tests on carbonation, freezing-thawing, and diffusion of chloride were carried out after 56 days of underwater curing at
to compare durability characteristics of 5% MgO-mixed concrete with those of OPC concrete. The results showed that MgO concrete shows a greater durability than the concrete with no MgO, because the micro structure in the MgO concrete is much denser due to its expansibility characteristic.
The Effect of Mild Tensile Reinforcement and Effective Prestress on the Flexural Performance of the Prestressed Lightweight Concrete Beams with Unbonded Tendons
Mun, Ju-Hyun ; Yang, Keun-Hyeok ; Byun, Hang-Yong ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 617~626
DOI : 10.4334/JKCI.2011.23.5.617
Seven post-tensioned lightweight concrete (LWC) beam specimens were tested under a symmetrical two-point top loading system. The parameters investigated were the amounts of mild longitudinal reinforcement and effective prestressing. The design compressive strength and dry density of the LWC tested were 30 MPa and 1,770
, respectively. Similar to post-tensioned normal weight concrete (NWC) beams, the crack propagation and stress increase of the unbonded tendons were significantly affected by the amounts of mild longitudinal reinforcement and effective prestressing. With the increase in the amounts of mild longitudinal reinforcement and effective prestressing, the serviceability and flexural capacity of the beams were enhanced whereas the stress increase in the unbonded tendons decreased. To control the crack width in post-tensioned LWC beams, a minimum amount of mild longitudinal reinforcement specified in ACI 318-08 provision is required. The flexural behavior of post-tensioned LWC beams and stress increase of the unbonded tendons could be rationally predicted by the proposed non-linear two-dimensional analysis. On the other hand, ACI 318-08 flexure provision was too conservative about the post-tensioned LWC beams.
Creep Behavior of High-Strength Concrete with Nylon Fibers at Elevated Temperatures
Kim, Young-Sun ; Lee, Tae-Gyu ; Kim, Woo-Jae ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 627~636
DOI : 10.4334/JKCI.2011.23.5.627
Recently, to prevent explosive spalling of high-strength concrete (HSC) members, the usage of nylon fiber instead of polypropylene fiber has increased. Past experimental studies have been conducted to examine the spalling and mechanical properties of HSC with nylon fibers when exposed to elevated temperature. However, the previous studies on HSC with nylon fibers subjected to high temperatures were performed only on the properties such as spalling, compressive strength, and elastic modulus rather than investigations on to the behaviors such as thermal strain, total strain, steady state creep, and transient creep. Therefore, in this study thermal strain, total strain, steady state creep, and transient creep of HSC mixed with nylon fibers with water to binder ratio of 0.30 to 0.15 were tested. The experimental results showed that nylon fibers did not affect the performance of HSC with nylon fibers at high temperatures. However, HSC with nylon fibers generated a larger transient creep strain than that of HSC without fibers and normal strength concrete.
Structural Capacity Evaluation of High Strength Concrete Short Columns with Various Design Parameters under High Temperatures
Kim, Hee-Sun ; Mun, Ji-Young ; Park, Jee-Eun ; Shin, Yeong-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 637~645
DOI : 10.4334/JKCI.2011.23.5.637
It is well known that high strength concrete with compressive strength higher than 50 MPa shows severe material and structural damages under fire due to spalling. To understand degradation of structural capacity of fire damaged high strength concrete structures, not only thermo-mechanical behavior needs to be defined, but also structural behavior of high strength concrete member under high temperature needs to be investigated. In this study, structural tests are performed by applying axial loads on high strength concrete columns exposed at elevated temperatures for assigned amount of time. The tested columns are prepared to have different concrete strength and polypropylene fiber percentage. The test results show that structural capacity of the columns decreased with increased compressive strength of concrete under same heating condition. Especially, it is interesting to note that high strength concrete columns with polypropylene fiber for spalling proof did not improve structural capacity compared to the columns without polypropylene fiber. The findings from the test are able to improve fire proof design of high strength concrete structural members and predicting structural performance of fire damaged structural members.
Characteristics of Pore Structures and Compressive Strength in Calcium Leached Concrete Specimens
Yang, Eun-Ik ; Choi, Yoon-Suk ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 647~656
DOI : 10.4334/JKCI.2011.23.5.647
In radioactive waste repositories constructed in underground, concrete member could be in contact with groundwater for a long time. However, this pure water creates concentration gradients which lead to the diffusion of Ca ions from the pore water and the degradation of underground concrete. Therefore, this study is aimed at investigating the alteration of pore structure and loss of compressive strength associated with dissolution. The results showed that as the leaching period became longer, the pore volume within 50 nm to 500 nm in diameter is greatly increased. Also, the volume of pores larger than 200 nm rapidly increased during initial leaching time and those below 200 nm gradually increased. Furthermore, the compressive strength gradually decreased with increase of degraded thickness. The residual strength of the degraded concrete with OPC was in the range of 33% to 58%.
Experimental Study on the Cracking Loads of LB-DECKs with Varied Cross-Section Details
Youn, Seok-Goo ; Cho, Gyu-Dae ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 657~665
DOI : 10.4334/JKCI.2011.23.5.657
LB-DECK, a precast concrete panel type, is a permanent concrete deck form used as a formwork for cast-in-place concrete pouring at bridge construction site. LB-DECK consists of 60 mm thick concrete slab and 125 mm height Lattice-girders partly embedded in the concrete slab. These decks have been applied to the bridges, which girder spacings are short enough to resist longitudinal cracking caused by construction loads. This paper presents experimental research work conducted to evaluate the cracking load of LB-DECKs designed for long span bridge decks. Twenty four non-composite beams and four composite beams are fabricated considering three design variables of thickness of concrete slab, height of lattice-girder, and diameter of top-bar. Static loads controlled by displacements are applied to test beams to obtain cracking and ultimate loads. Vertical displacements at the center of beams, strains of top-bar, crack propagation in concrete slab, and final failure modes are carefully monitored. The obtained cracking loads are compared to the analytical results obtained by elastic analyses. Long-term analyses using age-adjusted effective modulus method (AEMM) are also conducted to investigate the effects of concrete shrinkage on the cracking loads. Based on the test results, the tensile strength and the design details of LB-DECKs are discussed to prevent longitudinal cracking of long span bridge decks.
Analysis and Prediction for Abutment Behavior of Prestressed Concrete Girder Integral Abutment Bridges
Kim, Woo-Seok ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 667~674
DOI : 10.4334/JKCI.2011.23.5.667
This paper discusses the analysis method of prestressed concrete girder integral abutment bridges for a 75-year bridge life and the development of prediction models for abutment displacements under thermal loading due to annual temperature fluctuation and time-dependent loading. The developed nonlinear numerical modeling methodologies considered soil-structure interaction between supporting piles and surrounding soils and between abutment and backfills. Material nonlinearity was also considered to simulate differential rotation in construction joints between abutment and backwall. Based on the numerical modeling methodologies, a parametric study of 243 analysis cases, considering five parameters: (1) thermal expansion coefficient, (2) bridge length, (3) backfill height, (4) backfill stiffness, and (5) pile soil stiffness, was performed to established prediction models for abutment displacements over a bridge life. The parametric study results revealed that thermal expansion coefficient, bridge length, and pile-soil stiffness significantly influenced the abutment displacement. Bridge length parameter significantly influenced the abutment top displacement at the centroid of the superstructure, which is similar to the free expansion analysis results. Developed prediction model can be used for a preliminary design of integral abutment bridges.
Bond Behavior between Near-Surface-Mounted Fiber Reinforced Polymer Plates and Concrete in Structural Strengthening
Seo, Soo-Yeon ; Yoon, Seoung-Jo ; Kwon, Yeong-Soon ; Choi, Ki-Bong ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 675~682
DOI : 10.4334/JKCI.2011.23.5.675
Recently, in retrofit of RC structures using FRP (Fiber Reinforced Polymer), researches about Near-Surface-Mounted Rertofit (NSMR) method have been widely performed. In NSMR, FRP bar is normally inserted in the slit formed in the cover concrete and then bonded by using epoxy mortar. In this paper, the bond characteristic of NSMR using FRP plate instead of bar was studied experimentally. Fracture behavior is observed from bond test using the parameters of embedment length, shear key, and FRP plate layer. In addition, an equation to predict the splitting strength of NSMR using FRP is proposed using the test result. The results showed that when the longer embedment length and more layers of FRP are used, the higher bond strength is achieved. There was a good co-relationship between the test and calculated results using the proposed equation.
Reversed Lateral Load Tests on RC Frames Retrofitted with BRB and FRP
Lee, Han-Seon ; Lee, Kyung-Bo ; Hwang, Seong-Jun ; Cho, Chang-Seok ;
Journal of the Korea Concrete Institute, volume 23, issue 5, 2011, Pages 683~692
DOI : 10.4334/JKCI.2011.23.5.683
In piloti-type low-rise RC residential buildings, severe damages have been usually concentrated at piloti stories under the earthquake. In this study, a piloti story was retrofitted by installation of buckling-restrained braces (BRB's) to increase strength and stiffness of piloti story and by application of fiber reinforced polymer (FRP) sheet on columns to avoid the brittle shear and axial failure of columns. To verify this retrofit performance, reversed cyclic lateral load tests were performed on 1:5 scale bare and retrofitted frames. The test results showed that yield strength (43.2 kN) appeared to be significantly larger than design value (30 kN) due to the increase of strength in the compression side, but the stiffness value (11.6 kN/mm) turned out to be approximately one-half of the design value (24.2 kN/mm). The reasons for this difference in stiffness were due to slippage at joint between the frame and the BRB's, displacement and rotation at footing. The energy absorption capacity of the retrofitted frame was 7.5 times larger than that of the bare frame. The change of the number of load cells under the footing from 2 to 1 reduced lateral stiffness from 11.6 kN/mm to 6 kN/mm, which was only three times larger than that of the bare frame (2.1 kN/mm).