• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.147-148
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• 2023

Recently, as blast furnace slag concrete has become widely used, managing the strength of concrete has become important. mSn is a method of correcting the difference in strength between standard cured specimens and concrete exposed to changes in temperature. In this study, the predicted strength based on the maturity of the central and outer parts of the blast furnace slag concrete structure is compared with the actual strength measured through coring. As a result, the actual strength difference between the center and the outer part of the concrete mixed with blast furnace slag was larger than the predicted strength difference.

• Journal of Welding and Joining
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• 제10권1호
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• pp.20-34
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• 1992

Characteristics of two correcting methods, a new Autogeneous GTAW heating (TIG) method and the conventional GMAW bead-on plate welding(MIG) method, for distorted aluminum fabrication structures were studied. As a result of microscopic study of Autogeneous GTAW heating and GMAW bead-on plate welding areas, porosities in weld metal and surface cracks in local heating zone were found. Through the mechanical tests, it was verified that porosities decrease tensile strength and surface of distortion, angular displacement and transeverse shrinkage were measures and compared. In order to investigate changes of material properties in heating area and cause of defects such thermal stresses were calculated by ADINA. Through the computations of transient thermal stresses and microscopic observation of fracture surface, thermal stress was found to be the cause of crack during Autogeneous GTAW heating.

• Computers and Concrete
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• 제14권1호
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• pp.19-40
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• 2014

Reinforced concrete deep beams are structural beams with low shear span-to-depth ratio, and hence in which the strain distribution is significantly nonlinear and the conventional beam theory is not applicable. A strut-and-tie model is considered one of the most rational and simplest methods available for shear strength prediction and design of deep beams. The strut-and-tie model approach describes the shear failure of a deep beam using diagonal strut and truss mechanism: The diagonal strut mechanism represents compression stress fields that develop in the concrete web between diagonal cracks of the concrete while the truss mechanism accounts for the contributions of the horizontal and vertical web reinforcements. Based on a database of 406 experimental observations, this paper proposes a new strut-and-tie-model for accurate prediction of shear strength of reinforced concrete deep beams, and further improves the model by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method. Seven existing deterministic models from design codes and the literature are compared with the proposed method. Finally, a limit-state design formula and the corresponding reduction factor are developed for the proposed strut-andtie model.

• 한국지반신소재학회논문집
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• 제7권2호
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• pp.1-5
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• 2008

일반적인 콘크리트 건축물이나 도로포장에서 발생되는 부등침하는 건물의 붕괴나 도로의 수명저하로 인한 비용을 증가시킨다. 이에 대하여 침하된 구조물 하부지반에 그라우팅 공법을 이용하여 지반침하복원을 실시한다. 그러나 기존 그라우트 공법의 경우, 강도발현기간이 길고, 보강효과가 지속적이지 못한 단점을 지니고 있다. 이를 보완하기 위한 주입재료로써, 고밀도 팽창 재료의 특성을 평가하였다. 지반상태와 팽창재료의 주입량의 변화에 따른 압축강도의 변화와 화학물질에 대한 안정성 시험 및 SEM 촬영을 통하여 특성을 연구하였다. 압축강도는 다른 물질과의 혼합으로 높은 강도가 발현되었으며, 화학적 저항성은 대부분의 조건에서 반응하지 않았으나 알코올계열에 변화가 발생하였다. SEM 촬영을 통하여 강도발현에 있어서 조직구성이 촘촘할수록 치밀하게 구성된다고 판단하였다.

• 한국지반공학회논문집
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• 제19권1호
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• pp.93-102
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• 2003

일축압축시험은 방법이 비교적 간단하고 경제적이기 때문에 점토지반의 비배수 전단강도($c_u$)를 결정하는데 널리 사용되고 있다. 하지만, 구속압이 없는 상태에서 시험이 시행되기 때문에 지중응력 조건을 재현할 수 없고, 또한 삼축압축시험에 의한 강도보다 과소평가 되는 경우가 많다. 따라서, $c_u$를 시료교란에 대해 보정하여 실무에서 간단히 사용할 수 있는 강도 보정법이 요구된다. 본 연구에서는 흡수력 측정을 겸한 일축압축시험 만으로 원지반의 비배수 전단강도(이하, 원지반 강도)를 추정할 수 있는 방법을 제시하고자 한다. 제안된 방법은 완전시료의 이론적 전단강도식(Noorany와 Seed, 1965)을 기본으로 하며, 유효토피압과 일축압축시험의 유효응력거동 분석 결과( $A_f,\phi'$)를 필요로 한다. 특히, 전단저항각($\phi'$)은 일축압축시험의 수정파괴포락선($K_f$) 기울기가 삼축압축시험에 비해 약 1.6배정도 더 크게 평가된다는 시험결과를 근거로 하여 간단히 유추할 수 있다. 연구 결과, 제안된 방법에 의해 추정된 원지반 강도는 삼축압축시험(CK$_0$UC)의 비배수 전단강도와 유사한 값을 나타냈다.

• International Journal of Korean Welding Society
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• 제3권2호
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• pp.7-14
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• 2003

During the manufacture of a ship, longitudinal deformation is produced by fillet welding on the Built­Up beam used to improve the longitudinal strength of a ship. This deformation needs a correcting process separate from a manufacture process and decreases productivity and quality. This deformation is caused by welding moment, which is the value multiplied the shrinking force due to welding by the distance from the neutral axis on a cross section of Built­Up beam. This deformation can be offset by generating a moment which is the same magnitude with and is located in an opposite direction to the welding moment on web plate by induction heating. Accordingly, this study clarifies the creation mechanism of the longitudinal deformation on Built­Up beam with FEM analysis and presents the preventative method of this deformation by induction heating basing the mechanism and verifies its validity through analysis and experiments. The induction heating used here is performed by deciding its location and quantity with experiments and simple equations and by applying them to a real structure.

• 소성∙가공
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• 제18권6호
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• pp.488-493
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• 2009

The very big springback of advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be generally eliminated by die correction or process parameter control. The springback reduction by controlling the forming process parameters is easy for the application, but limited for the bulky achievement. In this study, the effective die correction method, which obtains the modification of tool shape from the relationship between die design variable and springback, is introduced and is applied to the TWB tool of automotive side rail to show the validity and usefulness. Among the die correction trials repeatedly performed, the first trial is carried out by correcting the tool shape to the opposite direction to the springbacks of several tool sections. Next trials are done by extrapolating the springbacks of among the original tool uncorrected and the tools corrected negative amounts of the springback and by finding tool shapes without springbacks. After the angle of side wall and radius of curvature of horizontal bottom floor are chosen as design variables in the tool design of side rail, the tool shape is corrected 3 times. The accuracy of final shape within the assembly limit of 1mm and the springback reduction of 75.8% compared to the uncorrected tool are achieved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.670-691
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• 2013

In RSSI-based RFID(Radio Frequency IDentification) indoor localization system, the signal path loss model of each sub-region is different from others in the whole localization area due to the influence of the multi-path phenomenon and other environmental factors. Therefore, this paper divides the localization area into many sub-regions and constructs separately the signal path loss model of each sub-region. Then an improved LANDMARC method is proposed. Firstly, the deployment principle of RFID readers and tags is presented for constructing localization sub-region. Secondly, the virtual reference tags are introduced to create a virtual signal strength space with RFID readers and real reference tags in every sub-region. Lastly, k nearest neighbor (KNN) algorithm is used to locate the target object and an error compensating algorithm is proposed for correcting localization result. The results in real application show that the new method enhances the positioning accuracy to 18.2% and reduces the time cost to 30% of the original LANDMARC method without additional tags and readers.

• 한국운동역학회지
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• 제25권4호
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• pp.401-412
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• 2015

Objective : The purpose of this study is to evaluate the effects of hip joint exercises and orthotics on RCSP, ankle's range of motion, and core muscle strength of middle school students with pes planus. Method : Out of the original pool of 200 students, 60 students with pes planus (RCSP < -2) were selected for the study. The selected 60 students were then divided into four groups. The first group was a combined orthotics and exercise group (12 students), the second was the orthotics-only group (9 students), the third was the exercise-only group (8 students), and the last was the control group (10 students). Exercise groups worked out twice a week for 60 minutes per session over 8 weeks. The independent variables were corrective hip joint exercises and orthotics. The dependant variables consisted of kinematic and kinetic variables. The kinematic variables were RCSP, and ankle's range of motion (dorsiflexion and plantarflexion). The kinetic variables were muscles forces that consist in core muscle strength, which are hip joint adduction, abduction, and flexion muscles forces. Statistical analysis was performed via SPSS 18.0 with multivariate analysis of covariance (MANCOVA) and a paired t-test was used. Results : The left foot was more responsive to the treatments, both exercise and orthotics, than the right foot. RCSP improved significantly in the left foot for the first and third groups. Only the first group significantly improved hip joint adduction, abduction, and flexion muscles' strengths. As for the ankle's range of motion of the left foot, plantarflexion showed improvement when treated with exercise, orthotics, or both. Conclusion : This study found that exercise is more effective in correcting RCSP and foot orthotics is more effective in reinforcing core muscle strength. Future studies should expand on these results to examine the relationship between the ankle, hip, and pelvis.

• 한국도로학회논문집
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• 제12권4호
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• pp.203-209
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• 2010

서울시내 도로 유지보수 4개 현장에서 수집된 재령 및 물리적 특성이 서로 다른 폐아스팔트를 폼드 아스팔트 공법을 사용하여 기층용 혼합물을 제작하였다. 혼합물은 구재와 신재의 비율을 서로 달리하여 제작하였으며 구재 비율 변화에 따른 성능을 실내시험을 실시하여 분석하였다. 실내시험은 마샬안정도, 간접인장강도, 회목탄성계수, 크리프 시험 및 휠 트레킹 시험을 실시하였으며 시험 결과는 재생가열 아스팔트 혼합물 시험 결과와 상호 비교하였다. 비교 결과, 재생 폼드 아스팔트 혼합물은 소성변형 및 온도 변화에 대한 저항성은 재생 가열 아스팔트 혼합물에 비하여 동등하거나 우수한 것으로 나타났다. 한편 재생 폼드 아스팔트 혼합물의 건조시 간접인장강도는 재생 가열 아스팔트 혼합물에 비하여 낮게 측정되었으며 습윤시에는 구재의 비율과 관계없이 모두 간접인장강도가 낮게 나타나서 습윤 조건에서는 취약한 것으로 발견되었다.