https://doi.org/10.11112/jksmi.2020.24.4.1

한재도(Jae-Doh Han) ; 이윤수(Yun-Su Lee) ; 이한승(Han-Seung Lee)

This study conducted to understand effects of CA (CaAl2O4) and CA2 (CaAl4O7) ratio on chloride binding ability and compressive strengthand pore structure of cement mortar incorporating mixture of CA and CA2. The Portland cement based specimens were mixed with the clinkers CAand CA2, and these calcium aluminate clinker mixture were replaced 0, 5, 10% by weight of cement. After all the test specimens were cured for 28days under water curing, they were immersed in the distilled water and NaCl solution. As a result, 28 days compressive strength of all specimens wassimilar, and As the replacement ratio of calcium aluminate clinker in the specimen increased, Friedel’s salt production tended to increase. However,it was dependent on the amount of Al2O3 in the level of 5% replacement and CA ratio in the level of 10% replacement. Through equilibrium isothermresult, it was also indicated that as replacement ratio of calcium aluminate clinker in cement matrix increased, chloride binding capacity was improved,and chloride penetration was suppressed. In this study, the specimen replaced with 10% of the calcium aluminate clinker mixture (CA 39%, CA2 60%)was remarkable to control chloride attack. We figured out necessity to understand optimal CA/CA2 ratio to effectively apply CA2 as a sustainable buildingmaterial by improving the chloride binding ability in Portland cement based system.

https://doi.org/10.11112/jksmi.2020.24.4.10

이화정(Hwa-Jung Lee) ; 변대근(Dae-Kun Byon) ; 윤성기(Sung-Kee Yoon)

The recent earthquake in Korea caused large and small damages to many school building. School building is an important building thatis used as a shelter in the event of disaster. Among the seismic retrofit methods, the internal steel braced frame type method is used for its relativelyeasy construction and excellent performance. In this study, the maximum shear force and displacement were compared and examined by applyingthe brace frame to existing concrete school buildings. As a result, we verified the adequacy of the analytical model and compared and examined theeffect of brace-height ratio on the span of the existing school buildings. The adequacy of the maximum shear force and displacement relationship canbe confirmed in the model with a length of 0.3. In addition, seismic frame was applied to the actual non-seismic reinforced concrete school building,and the seismic performance was evaluated by nonlinear static analysis(Push-over analysis) according to the ratio of brace-height. As a result, the increaseof the brace-height according to the brace-height ratio has the effect of increasing the maximum shear force and maximum load at the performancepoint. But the collapse of the braced frame due to the increase in the lateral stiffness occurred, indicating that seismic retrofit according to the properbrace-height is necessary. Therefore, in the seismic retrofit design of brace frame of existing school building, it is necessary to select the properbrace-height after retrofit analysis according to the brace-height ratio.

https://doi.org/10.11112/jksmi.2020.24.4.18

김병준(Byung Jun Kim) ; 유성원(Sung Won Yoo) ; 최영철(Young Cheol Choi)

The purpose of this study is to investigate the mechanical and carbon-capture properties of foam concrete containing stainless steelargon oxygen decarbonization(AOD) slag. AOD slag was used as a binder, and foam concrete having a foaming ratio of 69 ± 0.5 % and a slurrydensity of 573.2 to 578.6 kg / m3 was produced. In order to examine the effect of carbonation, blended specimen was cured by two types : normalcuring and CO2 curing. As a result of the experiment, the specimens incorporating AOD slag showed higher compressive strength than Plainafter CO2 curing. According to the analysis of the image of foam concrete, it was confirmed that the ST30 has a lower total pore volume andaverage pore size than plain, resulting in high compressive strength. The SEM analysis confirmed the formation of calcite by carbonation ofAOD slag. Through the thermogravimetric analysis, the increase of CO2 uptake was confirmed by the incorporation of AOD slag. Foam concretehas a higher porosity than normal concrete, so it is expected that carbon-capture performance can be improved by using a AOD slag.

https://doi.org/10.11112/jksmi.2020.24.4.26

신연우(Yeon-Woo Shin) ; 홍기남(Ki-Nam Hong) ; 권용민(Yong-Min Kwon) ; 연영모(Yeong-Mo Yeon)

This study intends to present a fragility analysis method suitable for concrete cable-stayed bridges by performing an analysis reflectingdesign criteria and material characteristics from the results of inelastic time-history analysis. In order to obtain the fragility curve of the cable-stayedbridge, the limit state of the main component of the cable-stayed bridge is determined, and the damage state is classified by comparing it with theresponse value based on inelastic time history analysis. The seismic fragility curve of the cable-stayed bridge was made by obtaining the probabilityof damage to PGA that the dynamic response of the vulnerable parts to input ground motion would exceed the limit state of each structural member. According to the pylon's fragility curve, the probability of moderate damage at 0.5g is 32% for the longitudinal direction, while 7% for the transversaldirection, indicating that the probability of damage in the longitudinal direction is higher in the same PGA than in the transversal direction. The seismicfragility curve of the connections showed a very high probability of damage, meaning that damage to the connections caused by earthquakes is verysensitive compared to damage to the pylon and cables. The cable's seismic fragility curve also showed that the probability of complete damage stateafter moderate damage state gradually decreased, resulting in less than 30% probability of complete damage at 2.0g.

https://doi.org/10.11112/jksmi.2020.24.4.38

송은석(Eun-Seok Song) ; 김재요(Jae-Yo Kim)

A parametric study for analytical correction using measurement results was performed to minimize errors in the predictions of columnshortening in RC tall building. The parameters of the column shortening analytical correction are the execution standard of analytical correction, thevalue of the analytical correction, and the measurement location, and the analytical correction models with the parameters were applied to theconstruction sequence analysis of a 41-story RC building to compare and analyze the correction effect according to the parameter. The reduction ratioof the error value for each floor was compared with the number of corrections and the total corrected value, and it was confirmed that the error tendedto be minimized when the execution standard of analytical correction was performed based on a regular interval, when the analysis correction valuewas corrected by the error value, and when the measurement position was measured every floor. From this, it was confirmed that the most appropriateanalytical correction model can be derived by applying multiple analytical correction models to the actual analysis model.

https://doi.org/10.11112/jksmi.2020.24.4.48

우태련(Tae-Ryeon Woo) ; 정치영(Chi-Young Jung) ; 김인태(In-Tae Kim) ; 이종한(Jong-Han Lee) ; 정진환(Jin-Hwan Cheung)

Cracks in reinforced concrete structures are the most common type of damage and are used as important analytical data to understand thefracture behavior characteristics of structures. Currently, there is a problem that most of the crack investigation relies on visual inspection, thereforemany researchers have proposed image analysis techniques to improve the problem. In this study, we proposed a crack evaluation method to be appliedat an indoor experimental level using image analysis method. The image analysis technique using color is for distinguishing a boundary surface betweenobjects existing in an image, and is a method for separating similar colors into one region based on a predefined color. In this study, to improve theaccuracy of image analysis, blue paint was applied to the concrete surface and bending experiments were performed. The image analysis method wasable to measure the crack width with superior accuracy compared to the crack diameter, and at the same time, it was also possible to analyze the deflectionof the beam. Both the crack and deformation were able to confirm the accuracy similar to the existing measurement method, and it was found thatthe image analysis method was very excellent in terms of applicability.

https://doi.org/10.11112/jksmi.2020.24.4.55

정연웅(Yeonung Jeong) ; 임귀환(Gwi Hwan Lim) ; 박수현(Su Hyeon Park) ; 김주형(Joo Hyung Kim) ; 김태상(Tae-Sang Kim)

This study investigates the mechanical properties and reaction products of activated slag pastes depending on gypsum presence and calciumcarbonate addition in terms of compressive strength tests and synchrotron X-ray diffraction. The chemicals of CaO and NaOH are used as activatorswith different two dosages. The reaction of CaO-activated slag without gypsum just accelerated by addition of calcium carbonate at early ages, butno improvement was observed at later ages. On the other hand, the mechanical properties of CaO-activated slag pastes with gypsum were improvedwith calcium carbonate, enhancing the stability of ettringite. The variation of mechanical properties of NaOH-activated slag pastes was negligibledepending on calcium carbonate addition in case of no gypsum. The addition of calcium carbonate into NaOH-activated slag pastes with gypsumdeteriorated its mechanical properties due to the ion competition between CO32- ions and SO32- ions, decreasing crystallinity of reaction products.

https://doi.org/10.11112/jksmi.2020.24.4.64

박주현(Ju-Hyun Park) ; 안효준(Hyojoon An) ; 한만석(Manseok Han) ; 민지영(Jiyoung Min) ; 이종한(Jong-Han Lee)

In recent years, many infrastructure have been rapidly aging around the world, which grows interest in the maintenance of theinfrastructure. Among the social infrastructure, bridge is a very important structure to transport lots of human and various products. Theperformance evaluation of bridge can be divided into the condition evaluation and safety evaluation, proposed by Korea Infrastructure Safety andTechnology Corporation. However, there are no separate criteria for the performance evaluation of three-class bridges. In general, the performanceof bridge is dominated by the results of the condition evaluation, which is lower than that of the safety evaluation. Therefore, this study assessed thecorrelation between the condition evaluation of superstructure and bridge and also between the condition evaluation and the safety andload-carrying capacity of bridge. The results of the study would provide a basic data for the more quantitative and higher relevant performanceevaluation of the existing bridges, particularly for three-class bridges.

https://doi.org/10.11112/jksmi.2020.24.4.72

박경언(Kyoung-Yeon Park) ; 윤현도(Hyun-Do Yun)

The purpose of this study is to secure the same or more structural performance and constructability for the details of hooks cross-constructedat 135 degrees used as external-ties standard detail in RC columns, therefore, to the purpose of improving constructability, the clip-type bindingimplement was suggested and A total of 28 pull-out specimens were prepared with the parameters of concrete compressive strength and clip-embededlength, clip installation location to examine the anchorage behavior of the clip-type binding implement. The experiment was carried out. The resultsof the experiment confirmed that the anchorage strength of the clip-type binding implement was higher than the details of hooks cross-constructedat 135-degree regardless of the diameter of tie and concrete strength, embeded clip length, clip installation. and The 90-degree end hook with clip-typebinding implement was showed a similar an anchorage behavior of 135-degree end-hooked transverse reinforcement, consequently, The 90-degreeend hooked with clip-type binding implement is evaluated to be the same anchorage behavior and performance as standard 135-degree end hook detail.

https://doi.org/10.11112/jksmi.2020.24.4.81

최형욱(Hyoung-Wook Choi) ; 이상호(Sang-Ho Lee) ; 최형석(Hyoung-Suk Choi) ; 김태형(Tae-Hyeong Kim) ; 백은림(Eun-Rim Baek)

A textile and capillary tube composite panel(TCP) was developed to simultaneously retrofit the seismic performance and the energy efficiency(e.g. heating or insulation performance) of existing unreinforced masonry (URM) buildings. TCP is a light-weight mortar panel in which carbon textilereinforcements and capillary tubes are embedded. Textile reinforcements plays a role of seismic retrofit and capillary tubes that hot water circulatescontribute to the energy retrofit. In this paper, the static cyclic loading tests were performed on the masonry walls with/without TCP to understandthe seismic retrofit effect of TCP retrofit and the results were summarized. The results of the test showed that the TCP contributed to increase thecapacity of the Shear strength and ductility of the URM walls. In addition, the deformation of the wall after cracking was substantially controlledby the carbon textile.

https://doi.org/10.11112/jksmi.2020.24.4.91

방진수(Jin Soo Bang) ; 윤일로(Ilro Youn) ; 권양수(Yangsu Kwon) ; 임홍재(Hong Jae Yim)

Post-installed anchors were widely used due to its workable benefits. Regarding the resistance performance of anchors, the critical edge distanceis presented to minimize the impact of concrete splitting. In the case of actual anchors, however, it is difficult to obtain the ideal edge distance. Thepurpose of this study is to identify resistance performance and behavior characteristics that contain complex elements such as concrete crack occurringunder tensile load. Tensile tests were conducted based on the standard method. Failure shape and the resistance characteristics that do not have thecritical edge distance were derived by tensile load. Parametric analysis according to the boundary condition was performed to simulate the actual tensilebehavior, through a nonlinear finite element model based on the specimen. Consequently therefore, verifying analysis results the resistance mechanismcan be applied through boundary conditions.