• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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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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• v.10 no.1
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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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• v.14 no.1
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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.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.1-5
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• 2008

The differential settlement on ordinary concrete buildings and paved roads are often occurred and which caused the failure of structure. The grouting method can be used for correcting the settlement of the structure. However, the grouting method has a disadvantage like that it takes a long time period to get a desired strength, and it is not a continuous in the phase of reinforced effect. In this paper, as an injecting material called GPCON to complement disadvantage, it is estimated about the characteristic that has a high-density expansion. With the changing of ground conditions and amount of injection, the change of physical strength on compression, the stability against chemical material are studied through the filming of SEM. The physical strength with compression is developed to high strength due to mixing with other material. It is not react with most of the material on chemical conditions except the component of alcohol. Through the SEM test. it is confirmed that the strength of material was increased as formation is being densified.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.93-102
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• 2003

Unconfined compression test (UC) has been widely used to determine the undrained shear strength ($c_u$) of clay, because it is convenient and economical. However, UC can not represent the behaviour of in-situ stress condition and the strength obtained by the test is generally underestimated compared to that of triaxial compression, due to no confining pressure. Therefore, a simple and practical method to correct the ($c_u$) for sample disturbance and to be used in geotechnical practice is needed. This study is aimed at proposing the method to estimate in-situ undrained shear strength from UC with suction measurement. The proposed method is based on theoretical shear strength equation of perfect sample (Noorany & Seed, 1965), and effective overburden stress and analysis results ($A_f,\phi'$) of effective stress behaviour by UC are needed for the equation. The shear resistance angle ($\phi'$) can be simply estimated through the result that $K_f$-line slope of the UC is 1.6 times higher than that of triaxial compression test. The result of this study shows that the measured strength by this method is very similar to that of the undrained shear strength by triaxial compression test (CK$_0$UC).

• International Journal of Korean Welding Society
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• v.3 no.2
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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.

• Transactions of Materials Processing
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• v.18 no.6
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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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• v.7 no.4
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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.

• Korean Journal of Applied Biomechanics
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• v.25 no.4
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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.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.203-209
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• 2010

The base asphalt mixtures that used the waste recycle asphalt correcting from the four different overlay construction sites in Seoul city were made using the foamed asphalt method. The sample mixtures were made in different ratio of the recycle asphalt and new asphalt material and the performance of the mixtures of the different ratio was investigated in the laboratory. The laboratory tests includes the Marshall test, the indirect tensile test, the resilient modulus test, the creep test and the wheel tracking test. The test of the recycle foamed asphalt mixtures(RFA) were compared with the those of the recycle hot mix asphalt(RHA) mixtures. The performance of the RFA is comparable to that of the RHA. On the other hand, the indirect tensile strength of the RFA in dry condition is lower than that of RHA and the indirect tensile strength of the RFA in wet condition is much lower than that of the RHA.