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 26, Issue 6 - Dec 2014
Volume 26, Issue 5 - Oct 2014
Volume 26, Issue 4 - Aug 2014
Volume 26, Issue 3 - Jun 2014
Volume 26, Issue 2 - Apr 2014
Volume 26, Issue 1 - Feb 2014
Selecting the target year
Static Behavior of Stud Shear Connector for UHPC Deck
Lee, Kyoung-Chan ; Kwark, Jong-Won ; Park, Sang-Hyeok ; Kim, Jee-Sang ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 573~579
DOI : 10.4334/JKCI.2014.26.5.573
Typical composite girder has been composed with conventional concrete deck and steel girder. Recently, ultrahigh-performance-concrete (UHPC) deck is proposed in order to enhance durability and reduce weight of deck as well as to increase stiffness and strength of the composite girder. This study investigates that a headed stud is still compatible as a shear connector for the UHPC deck and steel girder composite beam. Twelve push-out specimens are prepared to evaluate the static strength of stud shear connectors embedded in the UHPC deck. The test program proves that the static strength of the stud shear connectors embedded in UHPC well meets with design codes described in AASHTO LRFD. Chosen experimental variables are aspect ratio of height to diameter of stud, thickness of deck and thickness of concrete cover over the head of stud. From the test program, aspect ratio and cover thickness are investigated to mitigate the regulations of the existing design codes. The minimum aspect ratio and the minimum cover thickness given in AASHTO LRFD are four and 50mm, respectively. This limitation hinders to lower the thickness of the UHPC deck. The results of the experiment program give that the aspect ratio and the cover thickness can be lower down to three and 25mm, respectively. Eurocode-4 regulates characteristic relative slip at least 6mm. However, test results show that stud shear connectors embedded in UHPC provide the characteristic relative slip only about 4mm. Therefore, another measures to increase ductility of stud should be prepared.
Tension Stiffening Effect of RC Tension Members Reinforced with Amorphous Steel Fibers
Park, Kyoung-Woo ; Lee, Jun-Seok ; Kim, Woo ; Kim, Dae-Joong ; Lee, Gi-Yeol ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 581~589
DOI : 10.4334/JKCI.2014.26.5.581
This paper presents the tension stiffening behavior from experimental results of each 6 amorphous steel fibers and normal steel fibers reinforced direct tensile specimens with the main variables such as cover thickness to bar diameter ratio. A tension stiffening effect for steel fiber reinforced RC tension members improve on the increase in cover thickness, and also amorphous steel fiber is usually superior to normal steel fiber. The reinforcement of steel fibers controlled the splitting cracks and led to significant increase in the tension stiffening effect. In particular, if cover thickness is more than twice the bar diameter, the amorphous steel fiber reinforced specimen is controlled the splitting crack and increased the tension stiffening effect. And, the tension stiffening effect of amorphous steel fiber reinforced concrete tension members is different to current structural design code provision.
A Study on the Relationship between Compressive Strength and Water-Cement Ratio According to Water Reducing Ratio
Kim, Kyung-Hwan ; Oh, Sung-Rok ; Choi, Wook ; Choi, Yun-Wang ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 591~598
DOI : 10.4334/JKCI.2014.26.5.591
In this study, the relationship between compressive strength and water-cement ratio according to water reducing ratio was evaluated, concrete mix was prepared according to 3 level of water reducing ratio (0%, 8% and 16%) and 3 level of water-cement ratio (40%, 45% and 50%). In addition, concrete mix was carried out repetition test of three times in order to secure the reliability. As a result, compressive strength according to water reducing ratio was shown that difference of strength was about 20% occurred, effect of compressive strength according to water reducing ratio was found more than the water-cement ratio. Therefore, reflected the effect of water reducing ratio, relationship equation between new compressive strength and water-cement ratio was proposed.
Reduced Degree of Freedom Modeling for Progressive Collapse Analysis of Tall Buildings using Applied Element Method
Kim, Han-Soo ; Wee, Hae-Hwan ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 599~606
DOI : 10.4334/JKCI.2014.26.5.599
Since progressive collapse of tall buildings can cause enormous damage, it should be considered during the design phase of tall buildings. The progressive collapse analysis of tall buildings using finite element methods is almost impossible due to the vast amount of computing time. In this paper, applied element method was evaluated as an alternative to the finite element method. Reduced DOFs modeling technique was proposed to enable the progressive collapse analysis of tall buildings. The reduced DOFs model include only the part which is subjected to direct damage from blast load and the structural properties such as mass, transferred load and stiffness of excluded parts are accumulated into the top story of the reduced DOFs model. The proposed modeling technique was applied to the progressive collapse analysis of 20-story RC building using three collapse scenarios. The reduced DOFs model showed similar collapse behavior to the whole model while the computing time was reduced by 30%. The proposed modeling technique can be utilized in the progressive collapse analysis of tall buildings due to abnormal loads.
Durability Assessment for Crushed Sand Wet-mix Shotcrete Mixed with Mineral Admixtures
Lee, Kyeo-Re ; Han, Seung-Yeon ; Nam Gung, Kyeong ; Yun, Kyong-Ku ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 607~614
DOI : 10.4334/JKCI.2014.26.5.607
The purpose of this dissertation was to investigate the effect of mineral admixtures, such as fly ash, blast furnace slag powder, meta kaolin and silica fume, on the basic properties and durability of crushed sand shotcrete, selecting a series of shotcrete mixtures with a variable admixture. Compressive strength increased as the content of mineral admixtures increased, specially it was the most effective when using meta kaolin both at sample specimen and core after shotcreting. Rapid chloride ion permeability test and sulfuric acid resistance test showed that both durability increased as the substitute rate of mineral admixture increased. In air void analysis with image analysis, the targeted the spacing factor and specific surface were not satisfied because air-entrained agent was not used.
Measurement and Prediction of Long-term Deflection of Flat Plate Affected by Construction Load
Hwang, Hyeon-Jong ; Park, Hong-Gun ; Hong, Geon-Ho ; Kim, Jae-Yo ; Kim, Yong-Nam ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 615~625
DOI : 10.4334/JKCI.2014.26.5.615
Excessive long-term slab deflection caused by construction load is a critical issue for the design of concrete slabs, as long span flat plates become popular for tall buildings. In the present study, the effect of construction load causing early slab cracking on the long-term deflection was theoretically studied. On the basis of the result, a numerical analysis method was developed to predict the long-term deflection of flat plates. In the proposed method, immediate deflection due to slab cracking and long-term effect of creep and shrinkage were considered. To verify the construction load effect, long-term slab deflections were measured in actual flat plate buildings under construction. The results showed that the immediate deflection due to the construction load increased significantly the long-term deflection. The proposed method was used to predict the deflections of the buildings. The results were compared with the measurement results. The predictions agree well with the long-term deflections of flat plate affected by construction load.
Evaluation of Local Damages and Residual Performance of Blast Damaged RC Beams Strengthened with Steel Fiber and FRP Sheet
Lee, Jin-Young ; Jang, Dae-Sung ; Kwon, Ki-Yeon ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 627~634
DOI : 10.4334/JKCI.2014.26.5.627
In this study, standoff detonation tests and static beam tests on
RC beams were conducted to investigate the effect of local damage on the flexural strength and ductility index. And also, blast resistance of RC beams strengthened with steel fiber and FRP sheet were evaluated by these tests. The standoff detonation tests were performed with charge weight of 1kg and standoff distance of 0.1m. After the tests, crater diameters and loss weights of specimens were measured to evaluate the local damage of specimens. Flexural strength and ductility index were measured by conducting the static beam tests on the damaged and undamaged specimens. As a test results, normal concrete specimen(NC) showed relatively large crater and spall diameters that caused weight loss of 23.5kg as a local damage. Whereas, steel fiber reinforced concrete specimen(SFRC) and FRP sheet retrofitted specimens(NC-F, NC-FS) showed higher blast resistance than NC by reducing crater size and weight loss. Flexural strength and ductility index were decreased in case of local damaged specimens by detonation. Especially, large decrease of flexural strength was shown in NC as compared with intact specimen and brittle failure was occurred due to buckling of compressive reinforcement. In case of specimens strengthened with steel fiber and FRP sheet, residual flexural strength and ductility index were increased as compared with NC. In these results, it is concluded that critical local damage can be occurred unless enough standoff distance can be assured even if the charge weight is small. and it is verified that strengthening method using steel fiber and FRP sheet can increase blast resistance.
Evaluation of Shear Strength of Precast-prestressed Hollow Core Slabs Based on Experiments
Han, Sang-Whan ; Moon, Ki-Hoon ; Kang, Dong-Hoon ; Im, Ju-Hyeuk ; Kim, Young Nam ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 635~642
DOI : 10.4334/JKCI.2014.26.5.635
The weight of concrete could be reduced by using hollow core slabs instead of heavy solid slabs, leading to cost reduction. The long span be also achieved by introducing prestress in hollow core slabs. but the evaluation of shear strength of precast-prestressed hollow core slabs are needed because the cross section is reduced in web and arranging shear reinforcement is not possible. In this study, the shear strength of precast-prestressed hollow core slabs were evaluated based on experimental tests. For this purpose, six full scale specimens were made and tested. The shear strength of the specimens were compared with those evaluated from current design provision(EC2 ACI, EN1168 and AASHTO).
Estimation Method of Residual Performance for Hollow Slab at Elevated Temperature
Choi, Hyun-Ki ; Chung, Joo-Hong ; Choi, Chang-Sik ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 643~650
DOI : 10.4334/JKCI.2014.26.5.643
Generally, the reinforced concrete slab has great fire resistance performance because concrete has excellent thermal material properties under fire. But, in the case of hollow slab, it will be expected that hollow slabs have different temperature distribution and fire endurance performance compare to reinforced concrete slab. Because hollow slab has internal void space that occurs decreasing regenerative effect of concrete and formation of internal air layer. Evaluation method for fire resistance performance of hollow slabs was proposed using
method. For the casual use of evaluation, simplified method was proposed which was limited to solid slab and donut type hollow slab which was developed by authors of this research paper. Also, verification on proposed method was performed by comparing results of fire experiment for hollow slab and evaluation results. Proposed method of the results of this study was possible to predict the residual strength and temperature distribution of slabs under fire.
Bond Characteristics and Splitting Bond Stress on Steel Fiber Reinforced Reactive Powder Concrete
Choi, Hyun-Ki ; Bae, Baek-Il ; Choi, Chang-Sik ;
Journal of the Korea Concrete Institute, volume 26, issue 5, 2014, Pages 651~660
DOI : 10.4334/JKCI.2014.26.5.651
Structural members using ultra high strength concrete which usually used with steel fiber is designed with guidelines based on several investigation of SF-RPC(steel fiber reinforced reactive powder concrete). However, there are not clear design method yet. Especially, SF-RPC member should be casted with steam(90 degree delicious) and members with SF-RPC usually used with precast members. Although the most important design parameter is development method between SF-RPC and steel reinforcement(rebar), there are no clear design method in the SF-RPC member design guidelines. There are many controversial problems on safety and economy. Therefore, in order to make design more optimum safe design, in this study, we investigated bond stress between steel rebar and SF-RPC according to test. Test results were compared with previously suggested analysis method. Test was carried out with direct pull out test using variables of compressive strength of concrete, concrete cover and inclusion ratio of steel fiber. According to test results, bond stress between steel rebar and SF-RPC increased with increase of compressive strength of concrete and concrete cover. Increasing rate of bond stress were decrease with increase of compressive strength of SF-RPC and concrete cover significantly. 1% volume fraction inclusion of steel fiber increase the bond stress between steel rebar and SF-RPC with two times but 2% volume fraction cannot affect the bond stress significantly. There are no exact or empirical equations for evaluation of SF-RPC bond stress. In order to make safe bond design of SF-RPC precast members, previously suggested analysis method for bond stress by Tepfers were evaluated. This method have shown good agreement with test results, especially for steel fiber reinforced RPC.