https://doi.org/10.11112/jksmi.2020.24.1.1

한운우(Woonwoo Han) ; 이병재(Byungjae Lee)

As of 2018, Steel slag was generated approximately 24.23 million tons. Howeve, except blast furnace slag, steel slag is a typical by-product which does not have a clearly defined purpose in recycling. Thus, countries around the world are putting great efforts into developing a purpose for the recycling of steel slag. The vast habitat foundation of marine life has been destroyed due to recent reckless marine development and environment pollution, resulting in intensification of the decline of marine resources, and a solution to this issue is imperative. In order to propose a method to recycle large amounts of by-product slag into a material that can serve as an alternative to natural aggregate, the engineering properties and applicability for each mixing factor of environment friendly porous concrete as a material for the composition of seawater purification were in this study. Regarding the nutrient elution properties, it was clear that the nutrients continuously flowed out up to an immersion time by 8 months in natural seawater; the nitrogenous fertilizer displayed excellent elution properties in this regard.

https://doi.org/10.11112/jksmi.2020.24.1.8

천영수(Young-Soo Chun)

In the present paper, as a way of reducing heavyweight impact sounds, in particular, among floor impact sounds which have come to the forefront as a social issue recently, a floor joist slab is proposed that is expected to bring an effect of reducing heavyweight impact sounds through a shift in the natural frequency by installing a floor joist on a flat-type slab to increase the rigidity of the floor slab, differently from the existing method that increases the thickness of floor slab, and the heavyweight impact sound characteristics depending on the floor joist height and interval are interpretively analyzed. As a result of the analysis, though a trend is shown where the sound pressure level decreases as the slab thickness of floor joist increases, and as no difference is shown when thickness is above a certain value, it is thought that there is a threshold for the effect of an increase in floor thickness on blockage of heavyweight impact sounds. Also, as an increase in floor rigidity resulting from an increase in the floor joist height and a decrease in the interval does not lead to a consistent increase in the performance of blocking heavyweight impact sounds, it is thought that a different floor joist height and interval should be applied to each type of house to expect optimum performance of blocking heavyweight impact sounds, and an increase of 100mm in the floor joist height or a decrease of about 100mm in the interval is expected to bring an effect of reducing heavyweight impact sounds by about 1dB to 2dB.

https://doi.org/10.11112/jksmi.2020.24.1.16

전법규(Bub-Gyu Jeon) ; 장성진(Sung-Jin Chang) ; 김재봉(Jae-Bong Kim) ; 주부석(Bu-Seog Ju)

Water pipes are important facilities and consist of pipes of various specifications and materials. The annual average number of earthquakes in Korea is steadily increasing. Therefore, in case of the water pipe, it is estimated necessary to prepare for earthquakes. Damages to the water pipe by the earthquake can cause problems such as water supply and fire suppression, and cause damage to life and property. In Korea, however, it is difficult to find examples of seismic performance evaluation of water pipes based on experimental study. Damage to the water pipes by the earthquake is caused by the displacement-controlled behavior of the ground which is the liquifaction and fault lines. Especially, The damage to the water pipes by the earthquake is concentrated on the joint of the pipe. In particular, piping less than 200mm in diameter was found to be dangerous. Thus, in this study, the seismic and settlement performance of iPVC buried water pipes with fixed joints with a clamp of 150mm was evaluated with a test approach.

https://doi.org/10.11112/jksmi.2020.24.1.24

서기영(Ki-Young Seo) ; 김태완(Taewan Kim) ; 김성도(Seong-Do Kim)

This research is a study on the characteristics of OPC-slag cement using nano-silica solution (NSS) with water-weight substitution method. The new replacement method is a fundamental step to study the behavior of cement with higher NSS replacement rates than previous studies. NSS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. As a result, the mechanical and microstructural characteristics were improved. This can be summarized in two ways. First, when the NSS is replaced with mixing water, the homogeneous dispersion action of the nano-silica particles is improved. This promotes initial hydration. Second, substitution of NSS with higher density than mixing water reduces w / b. This forms a dense hydration reaction material. The new substitution method did not show any degradation of mechanical and microstructural properties as compared with the results using the powdered nano-silica particles revealed in the previous study. Therefore, it is considered that the method of weight substitution of NSS used in this study can be applied to the formulation of OPC-slag cement.

https://doi.org/10.11112/jksmi.2020.24.1.35

유석형(Suk-Hyung Yoo) ; 김달기(Dal-Gee Kim)

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30 °, the shear force of the column increased less than that of 60 °, and the lateral displacement of column was decreased in the order of □, ? and Ｈ in cross-section.

https://doi.org/10.11112/jksmi.2020.24.1.43

김수연(Soo-Yeon Kim) ; 김명지(Meong ?Ji Kim) ; 오상근(Sang-Keun Oh)

In this study, the possibility of seismic performance design was proposed and the quality verification test method was reviewed as part of the design of waterproof performance in underground walls under accelerated environment conditions for waterproofing materials, which are barrier and finishing material that can prevent ingress or overflowing water from inside and outside of a building by attaching all of the construction materials used in construction structures. Considering the current state of earthquake-resistant design of construction materials in Korea and abroad, seismic product groups are rare and mostly dependent on construction methods because there are no regulations on materials, although there are still regulations on earthquake-resistant design in the building process under the current law. Overseas, it was possible to confirm that various building materials that gave seismic performance to non-structural materials, such as Japan, Canada, and Germany, are being developed. If it is possible to have a complementary response to earthquakes in the advanced external waterproofing materials, it can be expected to be applicable as leak prevention and prevention technology along with the seismic designed structure.

https://doi.org/10.11112/jksmi.2020.24.1.51

최정일(Jeong-Il Choi) ; 이방연(Bang Yeon Lee) ; 김윤용(Yun Yong Kim)

The purpose of this study is to investigate experimentally the material strength and tensile deformation behavior of highly ductile high-strength cement composites reinforced by synthetic fibers. Materials and mixture proportions were designed to make composites with a strength level of 80 MPa in compression. Two kinds of polyethylene fibers with different properties were employed as reinforcing fibers. A series of experiments on density, compressive strength, and deformation performance was performed. Experimental results showed that the tensile behavior and cracking patterns of cement composite strongly depends on the types of reinforcing fibers. It was also demonstrated that the cement composite with a compressive strength of 77.7 MPa and a tensile strain capacity of 7.9% can be manufactured by using a proper polyethylene fiber.

https://doi.org/10.11112/jksmi.2020.24.1.59

오성록(Sung-Rok Oh) ; 김철규(Cheol-Gyu Kim) ; 남은준(Eun-Joon Nam) ; 최연왕(Yun-Wang Choi)

In this study, self - healing solid capsules of crystal growth type which can be mixed directly with repair mortar were prepared, and the quality and crack healing performance of repair mortar with self - healing solid capsules were evaluated. The table flow and the air flow rate of the repair mortar material mixed with self-healing solid capsules were found to have no significant influence on table flow and air volume regardless of mixing ratio. Compressive strength tended to decrease with increasing capsule mixing ratio. As a result of evaluation of crack healing properties according to constant water head permeability test, initial water permeability decreased, and reaction products were generated over time and cracks were healed.

https://doi.org/10.11112/jksmi.2020.24.1.67

신동익(DongIk Shin) ; 무하마드하룬(Haroon Muhammad) ; 민경성(Kyung Sung Min) ; 이광명(Kwang-Myong Lee) ; 이정윤(Jung-Yoon Lee)

In this study, the self-healing performance of mortar beams containing self-healing materials was evaluated through experiments. Normal mortar beams and self-healing mortar beams were used In the experiments. The self-healing performance was evaluated by comparing the mortar compressive strength, member strength, and self-healing effects of cracks. The experimental results showed that the compressive strength of mortar containing self-healing material was smaller than that of normal mortar, but the ratio of 118 days compressive strength to 28 days compressive strength was the same. The member strength tended to increase with increasing curing period. In normal mortar specimens, the member strength did not recover even if the curing period increased, but the strength of the self-healing mortar specimens tended to recover as reaction products were produced. The crack width tended to decrease after the healing periods in both specimens, but the reaction product was observed only in the self-healing mortar specimens.

https://doi.org/10.11112/jksmi.2020.24.1.74

김재환(Jaehwan Kim) ; 서동우(Dong-Woo Seo) ; 정규산(Kyu-San Jung) ; 박기태(Ki-Tae Park)

Safety inspection of cable-supported bridge has increasingly attention as many cable-supported bridges are currently constructed/operated. Whilst cables as a main component in cable-supported bridge should be inspected regularly, traditional method (visual inspection) has limitation to check the condition of cables properly due to restricted factors. It is evidently necessary to develop cable-inspection robot to overcome this concern. In this respect, the main aim in this study is to manufacture the improved robot compared with the existing robot. The improved functions of the robot in this study were that the robot can be operated in large cable diameter (greater than 200 mm) and climbing ability of the robot increases. In addition, electro-magnetic sensor as a non-destructive method in the robot was added to detect damaged cables and performance of the sensor was evaluated in indoor and field experiments. Consequently, the robot was able to move on the cable with ~0.2m/s and to detect damaged cables using the sensor. It was also confirmed that performance of the robot in field test is similar to that in indoor test.

https://doi.org/10.11112/jksmi.2020.24.1.80

조영국(Young-Kug Jo) ; 김완기(Wan-Ki Kim)

The purpose of this study is to investigate the physical properties and self-healing effects of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS). The EMMs with GGBFS were prepared with various polymer-binder ratios and GGBFS contents, and tested for strengths, adhesion in tension, water permeation and self-healing effects. The conclusions obtained from the test results are summarized as follows. The compressive strength of the EMMs with GGBFS is reduced with increasing polymer-binder ratios because of reduction of the degree of hardening in the EMMs, and is somewhat inferior to that of unmodified mortars. In the flexural and tensile strengths, the flexural strength of the EMMs is almost constant with increasing polymer-binder ratios. However, the tensile strength of the EMMs is gradually increased with increasing polymer-binder ratios. Regardless of the GGBFS contents, the adhesion in tension of the EMMs increases sharply with increasing polymer-binder ratios. The water permeation of the EMMs is remarkably reduced with increasing polymer-binder ratios and GGBFS contents. The self-healing effect of the hardener-free EMMs with GGBFS is improved with increasing water immersion period at a GGBFS content of 20%.

https://doi.org/10.11112/jksmi.2020.24.1.88

차경문(Kyoung-Moon Cha) ; 최소영(So-Yoeng Choi) ; 김일순(Il-Sun Kim) ; 양은익(Eun-Ik Yang)

It were found that the heavyweight waste glass can be used as a construction materials including concrete from previous experimental studies. In this study, in order to evaluate the structural behavior of RC members using heavyweight waste glass as fine aggregate, a flexural behavior test was performed. And then, its results were compared with those obtained from non-linear finite element model analysis. From the results, when the heavyweight waste glass as fine aggregate in RC member, the area of compressive crushing and the number of cracks increased, however, the mean of cracking spacing decreased. Also it had reduced the ductility at high loading stage. For this reason, the same analysis method about the RC member using natural sand as fine aggregate did not predict the initial stiffness, yield load and maximum load on the flexural behavior of the RC members using heavyweight waste glass as fine aggregate. On the other hand, when it is analytically implemented the reduction of neutral axis depth due to developed compression crushing, the results of non-linear finite element analysis could be predicted the experimental results, relatively well.

https://doi.org/10.11112/jksmi.2020.24.1.97

김예솜(Ye-Som Kim) ; 최병정(Byong-Jeong Choi)

In this study, finite element analysis was carried out through the finite element analysis program (ANSYS) to investigate the fire resistance of composite columns in fire. Transient heat transfer analysis and static structural analysis were performed according to ASTM E 119 heating curve and axial force ratio 0.7, 0.6, 0.5 by applying stress-strain curves according to temperature, and loading heating experiments were carried out under the same conditions. In addition, the nominal compressive strength of the composite column according to the heating time according to the standard(Eurocode 4) was calculated and expressed as the axial force ratio and compared with the analytical and experimental values. Through the analysis, As a result of finite element analysis, the fire resistance time was 180 minutes and similar value to the experimental value was obtained, whereas the fire resistance time 150 minutes and 60 minutes were derived from the axial force ratios 0.6 and 0.7. In addition, it was confirmed that the fire resistance time according to the axial force ratio calculated according to the reference equation (Eurocode 4) was lower than the actual experimental value. However, it was confirmed that the standard(Eurocode 4) was higher than the experimental value at the axial force ratio of 0.7. Accordingly, it is possible to confirm the fire resistance characteristics(time-axial force ratio relationship) of the SRC column at high axial force, and to use the experimental and anaylsis data of the SRC column as the data for verification based on Eurocode.

https://doi.org/10.11112/jksmi.2020.24.1.108

권기성(Ki-Seong Kwon) ; 전재영(Jae-Yeong Chun) ; 방진욱(Jin-Wook Bang) ; 김윤용(Yun-Yong Kim)

In this study, the flexural performance of Highly Ductile Cement Composites(HDCC) mimicking boundary conditions of shellfish skin layer was evaluated. To improve ductility by mimicking the boundary skin layer structure of shellfish, the method of stratification by charging between precast panels using HDCC and the method of distributing PE-mesh to the interface surface were applied. Evaluation of flexural performance of layered cement composite materials mimicking boundary conditions of shellfish skin layer resulted in increased ductility of all test specimens applied with stratified cross-section compared to typical bending test specimens. The layered method by inserting PE-mesh showed excellent ductility. This is most likely because the inserted PE-mesh made an interface for separating the layers while the HDCC pillars in the PE-mesh gave adhesion between layers.

https://doi.org/10.11112/jksmi.2020.24.1.116

김정래(Jung-Rae Kim) ; 김재요(Jae-Yo Kim)

In order to analyze the lateral-load resisting capability according to the core locations, three-dimensional structural analyses were performed for 20-story buildings with symmetric plan. Four analytical models for a center core, a single-axial eccentric core, and a double-axial eccentric core were constructed, and eigenvalue analyses, wind-load analyses, and earthquake-load analyses were performed. Torsion did not occur in the central core building, but the bending and torsion occurred in combination with the arrangement of the eccentric core, and the lateral-load resisting capability was degraded. The change in the wind load according to the eccentric core was small, but the maximum lateral displacement was found to increase greatly by the eccentric arrangement of the core. In addition, in case of the eccentric core, the seismic load was slightly reduced compared to the center core due to the decrease in the lateral stiffness, but it was found that the maximum story drift ratio increased significantly due to the torsional effect. Based on these results, the structural behavior according to the position of the core can be clearified and used as a guideline for core locations in the planning and design stage.

https://doi.org/10.11112/jksmi.2020.24.1.125

최효은(Hyo-Eun Choi) ; 최소영(So-Yeong Choi) ; 김일순(Il-Sun Kim) ; 양은익(Eun-Ik Yang)

The causes of concrete shrinkage are very diverse, in particular, aggregates impact the characteristics of shrinkage in concrete by constraining the shrinkage of cement paste. Meanwhile, owing to the lack of natural aggregate, various alternative aggregates are being developed, and their application in concrete also becomes more diverse. This study aimed to experimentally evaluate the drying and autogenous shrinkage in concrete that was composed of electric arc furnace slag as coarse aggregates. And, the results were compared with prediction models. From the results, the application of electric arc furnace slag can reduce the drying and autogenous shrinkage. In particular, autogenous shrinkage is greatly decreased. The predictions using GL2000 for drying shrinkage and Tazawa model for autogenous shrinkage were similar to the experimental results. However, the most prediction models do not consider the impact of aggregates, hence, the new prediction model should be developed or improved.

https://doi.org/10.11112/jksmi.2020.24.1.133

이상훈(Sang-Hoon Lee) ; 한선진(Sun-Jin Han) ; 조해창(Hae-Chang Cho) ; 이윤정(Yoon Jung Lee) ; 김강수(Kang Su Kim)

Korea Infrastructure Safety and Technology Corporation (KISTEC) specifies that the safety inspection and precise safety diagnosis of concrete structures shall be conducted in accordance with the 'Special Law on Safety Management of Infrastructure'. The detailed safety inspection and precise safety diagnosis guidelines presented by KISTEC, however, gives only the grade of members and structures, and thus it is impossible to quantify remaining service life (RSL) of the structures and to quantitatively reflect the effect of differential settlements on the RSL. Therefore, this study aims to develop a RSL evaluation model considering the differential settlements. To this end, a simple equation was proposed based on the correlations between differential settlements and angular distortion, by which the angular distortion of structures was then reflected in nominal strengths of structural members. In addition, the effects of the differential settlements on the RSL of structures were analyzed in detail by using the safety diagnosis results of actual concrete structure.

https://doi.org/10.11112/jksmi.2020.24.1.142

안은종(Eunjong Ahn) ; 신명수(Myoungsu Shin)

This study investigates the effects of moisture content on diffuse ultrasound to be applied for the evaluation of micro-structural damage in concrete subjected to various environmental conditions. We monitored diffuse wave parameters for concrete samples in process of water saturation for 5 days. Dried samples were immersed in a water bath, and the change of moisture content in concrete were estimated by measuring the change of mass. For the diffuse wave analysis, a frequency range of 500 kHz, which represents a scattering regime of ultrasound in concrete, was selected. The test results reveal that the ultrasonic diffusivity slightly changed, and the ultrasonic dissipation significantly increased by approximately 120% in the process of water saturation. Therefore, the moisture content in concrete should be considered for the evaluation of micro-structural damage using diffuse wave techniques.

https://doi.org/10.11112/jksmi.2020.24.1.148

이창용(Chang-Yong Lee) ; 김승훈(Seung-Hun Kim)

The paper is a summary of the results of the basic pullout test which is conducted to evaluate the anchorage capacity of high strength headed bars that is mechanical anchored vertically on steel fiber reinforced concrete members. The main experimental parameters are volume fraction of steel fiber, concrete strength, anchorage length, yield strength of headed bars, and shear reinforcement bar. Both sides of covering depth of the specimen are planned to double the diameter of the headed bars. The hinged point is placed at the position of each 1.5and 0.7 around the headed bars, and the headed bars are drawn directly. As a result of pullout test experiment, concrete fracture and steel tensile rupture appear by experimental parameters. The compressive strength of concrete is 2.7~5.4% higher than that of steel fiber with the same parameters, while the pullout strength is 20.9~63.1% higher than that of steel fiber without the same parameters, which is evaluated to contribute greatly to the improvement of the anchorage capacity. The reinforcements of shear reinforcements parallel to the headed bars increased 1.7~7.7% pullout strength for steel fiber reinforced concrete, but the effect on the improvement of the anchorage capacity was not significant considering the increase in concrete strength. As with the details of this experiment, it is believed that the design formula for the anchorage length of KCI2017and KCI2012 are suitable for the mechanical development design of SD600 head bar that is perpendicular to the steel fiber reinforced concrete members.