Earticle

Since the collapse accident occurred frequently during the construction when the floor height is high and the connection is made more than two stories, the government recommends the installation of the system support instead of the pipe support in the case of the construction of the height over a certain height. However, the system has been repeatedly assembled in a narrow place, so that it is possible to work as a cause of the disease called musculoskeletal disease. Particularly, in temporary equipment lender and construction companies, it is necessary to repetitively work with assembling and tooling of each member when working on workers. Therefore, as the number of occupational diseases such as musculoskeletal diseases increases, the related research is underway. However, in the existing research, the research has been limited to the lighter weight of the scaffold and the formwork, and there is no research on the weight saving of the system supporting the form. Therefore, in this study, we perform performance test and structural analysis of the high strength lightweight system support, which is developed to minimize the worker's musculoskeletal diseases and workload, and compare with the performance of the current system support.

Objective To investigate the effects of glenohumeral internal rotation deficit (GIRD) on the isokinetic strength, body pain, and the quality of life in male high school baseball players of Korea.Methods Fifty-six male high school baseball players were divided into either group A (GIRD≥20o, n=12) or group B (GIRD<20o, n=44). The range of motion in the shoulder and the isokinetic strength were measured. Questionnaires were administered regarding the body pain location by using the visual analogue scale, and the quality of life was measured by using the SF-36 Form.Results All subjects had increased external rotation range of motion and decreased internal rotation in the throwing shoulder. The incidence of GIRD (≥20o) was 21.43% in the present study. In the isokinetic strength test, a significantly weaker muscular state at an angular velocity of 180o/s was observed in group A, compared to group B. For the comparison of the pain, the frequency of shoulder pain was higher (33.93%) than other body pain, among the study subjects.Conclusion GIRD is one of the main risk factors of glenohumeral joint damage, and it is correlated with reduced isokinetic strength and quality of life. High school baseball players will need appropriate shoulder rehabilitation programs for the improvement in their quality of life and performance.

Polyurethane resin containing isocyanate is marked by excellent tensile and mechanical strengths and this test aims to gauge its applicability as a medical high polymer. Tris [2-(acryloyloxy)ethyl]isocyanurate and hexamethylenediisocyanate were added to a basic mixing ratio of HEMA (2-hydroxyethyl methacrylate), MMA (methyl methacrylate), NVP (n-vinyl- 2-pyrrolidone) and crosslink agent, EGDMA (ethylene glycol dimethacrylate) with increasing proportions and copolymerized respectively. Also, the basic physical properties of the polymerized high polymers including refraction rate, tensile strength, light transmission and water content were measured to confirm that they are appropriate as hydrogelcontact lenses. After measuring the physical properties of high performance polymers produced by adding tris [2-(acryloyloxy) ethyl]isocyanurate, it was found that the average tensile strengths of sample TRIS1 to TRIS10 were between 0.285 and 0.612 kgf, while the average values of refractive index were ranged from 1.441 to 1.449 with water content from 30.00 to 37.35%.The measurement of physical properties of the copolymers generated by adding hexamethylenediisocyanate showed that the average tensile strength of sample HEXA1 to HEXA10 ranged from 0.267 to 1.742 kgf, the refractive index ranged from 1.443 to 1.475 and water contents were in the range of 21.22 to 35.58%. In all combinations the transmission rates satisfied the transmittance of general hydrogel contact lenses. From theresults, it is possible to conclude that the produced copolymers can be used as contact lens materials with excellent tensile strength.

Bi-2212 (Bi2Sr2CaCu2O8+x) high temperature superconducting (HTS) wires are attracting significant attention in high field magnet applications due to their high engineering critical current density (Je) and excellent performance in high magnetic fields. However, the Ag/AgMg alloy matrix used in Bi-2212 wires exhibits a low elastic modulus (E = 70 GPa) and yield strength (σy < 100 MPa) [1], making the wires prone to deformation even under small loads, which leads to performance degradation. These low electromechanical properties impose strain-induced limitations on the performance of high-field solenoid magnets rather than current-induced limitations. To address this issue, enhancing the mechanical strength of Bi-2212 wires is essential. In this study, we aimed to improve the mechanical strength of Bi-2212 wires using a strip lamination technique. The Bi-2212 round wire was processed into a tape form through a flat-rolling process, and Inconel X-750 strips were bonded to both sides of the Bi-2212 tape using a bonding process, resulting in the fabrication of a final Inconel X-750 laminated sample with a thickness of 0.84 mm and a width of 1.88 mm. Tensile tests at cryogenic temperatures (77 K) revealed that the Inconel X-750 laminated sample achieved a strength of 278 MPa at a strain of 0.4 %, representing a twofold improvement compared to the original round wire. Additional investigations included filament area uniformity and Je property changes during the flat-rolling process, as well as interfacial analysis between the Bi-2212 tape and the Inconel X-750 strip during the heat treatment process.

This study was to examine the effects of high-intensity circuit training on muscle strength, blood irisin, fibroblast growth factor (FGF)-21, and adiponectin in obese female college students. The subjects (n=10) of this study performed high-intensity circuit training (jogging, stretching, squat jump, arm walking & push up, lunge jump, burppe test, mountain climber, side step, crunch & side crunch). The exercise program in this study corresponded to an intensity of 60 to 80% of the maximum oxygen consumption and was performed three times per week for 4 weeks. Obesity and metabolic syndrome markers, including blood pressures, lipid profiles, fasting glucose and serum irisin, FGF-21, total adiponectin and HMW adiponectin were measured at baseline and after exercise intervention. Paired t-test were used to assess the effects of high-intensity circuit training. Following 4 weeks, body weight, body fat (%), body mass index (BMI), waist circumference (WC) significantly decreased, whereas Irisin significantly increased. These results suggested that high-intensity circuit training may be useful for improving Irisin and obesity index in obese women.

Purpose: This study is to investigate the relationship between pitcher’s ball speed, shoulder muscle strength, and proprioception. Methods: Thirteen high school pitchers participated in this study. Ball speed was measured using a speed gun. A dynamometer and an electrogoniometer were used to measure the strength and proprioception, respectively, for both internal and external rotations in the shoulder. Results: This study demonstrated that pitcher’s ball speed was correlated with muscle strength and proprioception of shoulder internal rotation. Conclusion: This result will help to provide the basic knowledge for sports rehabilitation and athletic performance.

Electrotherapy modalities are one of the increasing ways of muscle strength and endurance. However, it is not clear which electrotherapy modalities are more effective. The purpose of this study is to compare the effect of Russian current (RC) and high voltage pulsed current (HVPC) on the strength and endurance of the quadriceps muscle. The study was performed on 10 volleyball athletes. The participants’ extrem-ities were divided into two groups as RC and HVPC. Muscle strength and endurance levels were assessed by an isokinetic device. Isokinetic training and 20-min electrotherapy were given in each treatment ses-sion. This training program consisted of a total of 12 sessions, sched-uled twice a week for 6 weeks. After training, knee extensor peak torque values and endurance ratios have increased in both groups, but it was determined that this increase was only significant in terms of the endurance ratio (P<0.05). There was no significant difference between the muscle strength and the endurance ratio of the RC and HVPC groups (P>0.05). RC or HVPC have no advantages over each other, and therefore it has been determined that both currents can be used in or-der to strengthen muscles and increase muscular endurance. Addition-al studies whose longer-term effects will investigate are needed.

본 연구는 다양한 산업부산물을 활용하여 고강도 클링커를 제조하기 위해 원료 배합 설계 및 이에 따른 클링커 주요 광물상(C3S, C2S, C3A, C4AF)의 형성 특성을 분석하였다. 실험을 통해 원료 대체율 및 Modulus 조건(LSF, SM, IM)이 클링커의 주요 광물상의 형성과 물리적 특성에 미치는 영향을 확인하였다. 소성온도 1,500 ℃, LSF 100, SM 2.7, IM 1.5의 Modulus 조건에서 제조된 A-1 클링커는 C3S 생성량이 75.0 %으로 확인되었으며, 로드밀 분쇄를 통해 4,000 cm2/g의 분말도(Fineness)를 확보하였다. A-1 클링커를 이용해 제작한 모르타르 공시체의 3일, 7일, 28일 압축강도는 각각 37.1 MPa, 45.6 MPa, 60.5 MPa를 확인하였다. 또한, 기존 연구와의 비교를 통해 산업부산물 활용이 클링커의 C3S 함량 및 물리적 특성에 미치는 영향을 분석하였다. 특히, 본 연구에서 활용한 KR 슬래그 기반 A-1 클링커는 기존문헌에서 보고된 C3S 함량(65∼70 %)을 상회하였으며, 고강도 시멘트로의 적용 가능성을 확인하였다.

This study analyzed the formation characteristics of major clinker phases (C3S, C2S, C3A, C4AF) by varying the raw material mixing design to manufacture high-strength clinker using various industrial by-products. The effects of raw material substitution content and modulus conditions (LSF, SM, IM) on the formation and physical properties of the major clinker phases were confirmed through experiments. The A-1 clinker, manufactured under the modulus conditions of LSF 100, SM 2.7, IM 1.5, and a calcination temperature of 1,500°C, was confirmed to have a C3S production of 75.0%. A fineness of 4,000 cm2/g was achieved through rod milling. The compressive strengths of the A-1 clinker were 37.1 MPa, 45.6 MPa, and 60.5 MPa at 3, 7, and 28 days, respectively. A comparative analysis with previous studies examined the impact of industrial by-products on C3S content and clinker properties. The A-1 clinker utilizing KR slag achieved a C3S content exceeding the typical range reported in the literature (65~70%). This result confirms the potential of A-1 clinker for high-performance cement applications.

플라이애쉬와 고로슬래그를 첨가하여 만드는 3성분계 콘크리트는 산업부산물 이용에 따른 초기공사비 절감과, 환경친화적인 측면에서 매우 효과적이다. 3성분계 콘크리트는 장기강도의 안정적인 발현, 높은 작업성과 수화열 감소에도 매우 효과적인 것으로 알려져 있다. 그러나, 3성분계 콘크리트는 포졸란계 혼화재의 사용에 따른 초기강도 발현이 문제점이다. 이러한 문제는 시공성 및 경제성에 있어 3성분계 콘크리트 사용을 제약하는 요소로 작용하고 있다. 본 연구에서는 이러한 문제를 해결하기 위하여 플라이애쉬, 고로슬래그 미분말을 혼입한 콘크리트에 있어 조강시멘트를 사용하여 단기 및 장기강도 발현, 투수저항성 및 내화학약품성을 평가하였다. 플라이애쉬 혼입율은 10%로 고정하고 고로슬래그 미분말을 0, 10, 20, 및 30%로 혼입한 3성분계 조강콘크리트를 제작하였다. 실험결과, HE-TBC의 압축 및 휨강도의 우수한 초기강도발현 특성을 얻을 수 있었으며 특히, 플라이애쉬 10% 및 고로슬래그 30%가 혼입된 HE-TBC의 투수특성은 매우 낮은 투수성을 나타내어 새로운 3성분계 조강콘크리트의 활용이 가능할 것으로 판단되었다.

Ternary blended concrete(TBC), which contains both fly ash and granulated blast furnace slag, has an initial cost effective and is environment friendly. Furthermore, it has a lot of technical advantages such as the improvement of long term compressive strength, high workability, and the reduction of hydration heat. However, as the use and study on the performance of ternary blended concrete is limited, it is low short term compressive strength. This study was performed to evaluate the characteristics which are a long and short term compressive strengths, permeability and chemical attacks resistance of hardened high early concrete containing slag powder and fly-ash using high early strength cement(HE-TBC). Replacement rate of FA is fixed on 10% and replacement rate of slag powder are 0%, 10%, 20% and 30%. The test results showed that compressive and flexural strength of HE-TBC increased as the slag contents increased from 0% to 30% at the short term of curing. The permeability resistance of HE-TBC(fly ash 10%, blast 30%) was extremely good at the short and long terms. However, high early strength ternary blended concrete had weak on carbonation of chemical attack.

본 연구는 산업부산물을 다량 활용하여 지반 함몰 발생시 긴급 복구를 위한 저강도·고유동 경량기포 콘크리트의 최적배합을 설정하고, 이를 현장에 적용하여 가능성을 평가하기 위한 연구이다. 실험의 변수로는 배합수 대비 기포제의 혼입률과 페이스트 용적대비 기포의혼입률이며, 실험을 통하여 선정된 최적배합으로 현장적용을 통한 기초특성을 평가하였다. 실험결과 배합수 대비 최적의 기포제 혼입률은 10%가 가장 효율적이라 판단되었으며, 페이스트 대비 선발포된 기포의 혼입률은 170%에서 목표를 만족하였다. 그러나, 현장적용 시안정적인 품질확보를 위하여 기포 혼입률은 140%로 현장의 배합에 적용하였다. 친환경 결합재를 이용한 저강도·고유동 경량기포 콘크리트의 현장적용 결과 목표성능을 모두 만족하여 지반복구용 배합 및 공법으로서의 가능성을 확인하였다. 그러나 기포 및 페이스트간의분리로 인한 상하부의 품질편차가 발생함에 따라 이의 개선을 위한 후속연구가 요구된다.

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

The column-supported wall system structures are being built according to increase of population and accelerated urbanization. In this study, characteristics of shear wall system subjected to lateral load is analyzed and the stress distribution and deformation characteristics of the column-supoorted wall system structures were compared. The results obtained from the model using the plane stress elements were compared with the results of the model with a beam-column elements for column - supported wall type structures. The bending moment of the model with beam-column elements was 0.53 times of that of model with plane stress elements at the end of transfer girder. And the bending momomet at the center of transfer girder consist of beam-column elements was 1.59 times of that of model with plane stress elements.

Currently buildings in Korea get ultra higher-storied by rapidly changed technology of construction and a dense population. However, Korea uses high-price silica fume depending on import in the whole quantity generally to be manifested compressive strength for ultra high-rising buildings and currently has a lot of difficulties in applying high-strength concrete to the field by increase of concrete’s unit price according to using silica fume. Therefore, the study enforced experiments, setting up each kind of water-binder rates and fin aggregate rates to achieve design standard strength and slumpflow of its target and applying each king of additives to analyze engineering properties of high-strength concrete with high-strength binder with which we can replace silica fume. As the result, high-strength binder showed better tendency than the existing silica fume in fluidity and early strength properties.

In this study, many concrete specimens were tested to investigate the variations of strength characteristics of high-strength concrete due to amount of recycled coarse aggregates, and to investigate the effect of steel-fiber reinforcement on concrete using recycled coarse aggregates. The variables of specimens were displacement ratios of recycled coarse aggregates, 30%, 60%, 100%, of total coarse aggregates and steel-fiber reinforcement. Test results showed that all of the variations of compressive, tensile and flexural strength appeared in linear reduction according to icrease the amount of recycled coarse aggregates, and steel-fiber reinforcement of 0.75% volumn of concrete recovered completely spliting tensile strength and flexual strength and recovered greatly compressive strength of concrete using recycled coarse aggregates of 100% displacement.

본 연구에서는 고강도 그라우트를 충전한 기계식 슬리브 철근이음의 강도를 보다 포괄적이고 적절하게 평가하기 위하여, 저자에 의하여 실시된 철근이음 실험체를 포함한 기존의 350여개 그라우트 충전형 슬리브 철근이음의 실험자료를 대상으로 하여 주요한 슬리브 철근이음의 영향인자가 이 철근이음의 강도에 미치는 영향을 비교분석하였다. 본 연구에서는 ACI 규준과 AIJ 규준에서 요구하는 기계식 철근이음의 인장강도를 만족하는 fg*(L/d)(fg는 그라우트의 압축강도, L/d는 철근의 정착길이와 철근직경의 비)를 제시하였다. 또한 본 연구 결과에서 철근이음의 슬리브 형상은 고강도 그라우트 충전형 기계식 슬리브 철근이음의 강도에 영향을 주는 것으로 나타났다.

The purpose of this research is to evaluate more diversely and adequately the strength of the mechanical reinforcement splices filling high-strength grout. For this purpose, we analyzed and compared the previous test results of 349 actual-sized splices specimens, including splices prepared and tested by the author. The study results showed that the minimum values of compressive strength of grout(fg) multiplied by the ratio of reinforcement development length to bar diameter(L/d) were proposed for retaining the tensile strength of the mechanical reinforcement splices required in ACI code and AIJ code. Also, the result of this research indicated that the sleeve shape of the bar splices had influence on the strength of mechanical reinforcement splices filling high-strength grout.

In this study compressive and shear strength reduction of green-type polymer concrete and effect of steel-fiber reinforcement were investigated to make clear the possibility of using vast amount of the blast furnace slag powder and recycled coarse aggregates for reducing CO₂emission and resolving a problem of the natural environmental disruption by using 2nd class blast furnace slag powder and 1st class recycled coarse aggregates. Test results showed that when blast furnace slag powder with displacement ratio, 80% and recycled coarse aggregates with displacement ratio, 100% were used at the same time, the compressive strength were reduced 13% at 10 days, 5% at 28 days, 2%~4% at 56 days, but by steel-fiber reinforcement the reduced compressive strength were recovered and increased 2%~4%, and that diagonal shear strength of short beams were reduced 12%~15%, but by steel-fiber reinforcement the reduced shear strength were recovered completely and increased 10% above ln comparison with that of base concrete specimen.

In this study, 25 concrete specimens were tested to investigate the variations of shear strength characteristics of high-strength concrete beams due to amount of recycled coarse aggregates replaced, and to investigate the effect of steel-fiber reinforcement on concrete using recycled coarse aggregates. The variables of specimens were replacement ratios of recycled coarse aggregates, 30%, 60%, 100%, of total coarse aggregates and steel-fiber reinforcement. Test results showed that the shear strength deterioration was not proportioned to replacement ratios of recycled aggregates, the shear strength falled rapidly at 30% of replacement ratio so far as 34% of strength reduction ratio, but after that it falled a little within 3% up to the replacement ratio 100%, and steel-fiber reinforcement of 0.75% of concrete volumn recovered completely the deteriorated shear strength and shear elastic modulas, moreover improved the shear strength above 50% rather than that of the high-strength concrete using natural coarse aggregates.

According as structure becomes skyscraper-ization, bigger and importance of land price environmental problem etc. increases, special pile method that use in only usual earthwork is used some in architecture works. According as safety realization of structure with introduction of an earthquake resistant design, file used for foundation structure need bigger intrusion and bearing power Therefore, it is selection and real condition that new public law is required of pile foundation that consider necessary basic data acquisition and economy that do reasonable construction project establishment, static pile load test and dynamic pile load test, soil quality basic data assembling flag age of forty years and stability in pile foundation design through soil survey of site.

In this study, experimental research was carried out to improve the seismic performance of reinforced concrete interior beam-column joints using high performance mortar and advanced reinforcing detailings. Test result shows that retrofitting specimens(IJIR, IJIRCS, IJIRCSP) designed by the improvement of earthquake-resistant performance and ductility using high performance mortar and advanced reinforcing detailings could attained more maximum load-carrying capacities and stable hysteretic behavior. The maximum load-carrying capacities of each specimens were increased 1.14~1.22 times in comparison to standard specimen.