• Journal of Korean Association for Spatial Structures
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• v.15 no.3
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• pp.103-110
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• 2015

Various hybrid dampers have been developed as increasing tall buildings in Korea. To minimize the installment space and cost, the new hybrid friction damper was developed using friction components. It is composed of two one-nodal rotary frictional components and a slotted bolted frictional connection. Because of these components, hybrid friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, displacement amplitude dependency tests were carried out to evaluate on the structural performance and the multi-slip mechanism of the hybrid damper. Test results show that the multi-slip mechanism is verified and friction coefficients are increasing as displacement amplitudes are increasing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.82-90
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• 2020

This study investigated the effects of empathy, self-control, and smartphone dependency on the interpersonal relationships of nursing students. The survey participants were 157 students in A city. The data was collected through self-report questionnaires that were obtained from May 27 2019 to May 31 2019. The data was analyzed using descriptive statistics and Independent t-tests, One-way ANOVA, Pearson correlation coefficients, and Stepwise multiple regression analysis of the SPSS 14.0 program. As a result, self-control (F=5.319, p=.006) and smartphone dependency (F=4.854, p=.009) showed significant differences according to the school records. Smartphone dependency (t=-3.381, p<.001) showed significant differences according to smartphone use. Age was found to have a statistically positive correlation with self-control (r=.194, p=.015) and it had a negative correlation with smartphone dependency (r=-.223, p=.005). Self-control was found to have a statistically positive correlation with empathy (r=.244, p<.01), interpersonal relationship (r=.540, p<.001). and negative correlation with smartphone dependency (r=-.432, p<.001). Empathy was found to have a statistically positive correlation with interpersonal relationships (r=.476, p<.001). Stepwise multiple regression analysis revealed that the predictors of interpersonal relationships were self-control (β=.477, p<.001), empathy (β=.359, p<.001), and smartphone use (β=.208, p<.01) which accounted for 45.0% of all the variance (F=12.029 p<.01). An enhancement program of nursing students' interpersonal relationships is needed that considers their self-control, empathy, and smartphone use.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.514-519
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• 2005

A tube hydroformability testing system was designed and fabricated enabling to apply the forming condition along arbitrarily pre-programmed internal pressure-axial feed path. The free-bulging and T-forming tests were carried out on the extruded aluminum (A6063) tube specimens with 40.6 mm outer diameter and 2.25 mm thickness. Nine different combinations of internal pressure and axial feed, yielding different strain paths from one another, were taken into consideration in order to induce bursting at various deformation modes. Major and minor strains were automatically measured from deformed grids around the fracture using a stereo-vision-based surface strain measurement system, named ASIAS. The forming limit diagram of the A6063 tube material was successfully obtained. Most of the data points acquired from free bulging and T-forming tests appeared in the range of negative minor strain on the FLD and are mostly located near the strain paths calculated from explicit finite element simulations. The forming limit obtained from tests after pre-tension was considerably lower than that from tests without pre-tension, which showed the strain path-dependency of the forming limit as well known in the sheet forming fold.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.383-391
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• 2013

A number of true triaxial tests on rock samples have been conducted since the late 1960 and their results strongly suggest that the intermediate principal stress has a considerable effect on rock strength. Based on these experimental evidence, various 3-D rock failure criteria accounting for the effect of the intermediate principal stress have been proposed. Most of the 3-D failure criteria, however, are focused on the phenomenological description of the rock strength from the true triaxial tests, so that the associated strength parameters have little physical meaning. In order to confirm the likelihood that the intermediate principal stress dependency of rock strength is related to the presence of weak planes and their distribution to the preferred orientation, true triaxial tests are simulated with the transversely isotropic rock model. The conventional Mohr-Coulomb criterion is extended to its anisotropic version by incorporating the concept of microstructure tensor. With the anisotropic Mohr-Coulomb criterion, the critical plane approach is applied to calculate the strength of the transversely isotropic rock model and the orientation of the fracture plane. This investigation hints that the spatial distribution of microstructural planes with respect to the principal stress triad is closely related to the intermediate principal stress dependency of rock strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.22-29
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• 2023

In the evaluation of seismic performance for structural materials and components, the loading rate and axial force can have a significant impact. Due to time-delay effects between input and output displacements, It is difficult to apply high-rate displacement in cyclic tests and hybrid simulations. Additionally, the difficulty of maintaining a consistent vertical load in the presence of lateral displacement has limited fast and real-time tests performed while maintaining a constant vertical load. In this study, slow, fast cyclic tests and real-time hybrid simulations were conducted to investigate the rate dependency and the influence of vertical loads of Isolation Bearing. In the experiment, the FLB System including an Adaptive Time Series (ATS) compensation and a state estimator was constructed for real-time control of displacement and vertical load. It was found that the vertical load from the superstructure and loading rate can have a significant impact on the strength of the seismic isolation bearing and its behavior during an earthquake. When conducting experiments for seismic performance evaluation, they must be implemented to be similar to reality. This study demonstrates the excellent performance of the system built and used for seismic performance evaluation and enables accurate and efficient seismic performance evaluation.

• International Journal of Concrete Structures and Materials
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• v.4 no.1
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• pp.17-23
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• 2010

The feasibility of the use of scrap tire rubber in concrete was investigated. The tests conducted in two groups: replacing of coarse aggregates with crumb rubber and cement particles with rubber powder. To distinguish the properties of new concrete, the following mechanical and durability tests were designed: compressive, tensile and flexural strength, permeability and water absorption. Rubber addition could affect the concrete properties depend on the type and percentage of the rubber added. Although the rubber addition modifies the mechanical characteristics of concrete in a way, but higher rubber content could not be useful. Concrete durability showed more dependency to the type of rubber instead of percentage of rubber. Moreover, to optimize the mechanical and durability of rubberized concrete, the useful percentage of rubber has been recommended.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.245-252
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• 2000

Model tests on free standing pile groups and piled footings with varying a pile spacing in two layered soils are carried out. The influence of pile cap on the behaviors of end bearing pile groups is analyzed by comparing the bearing behavior in piled footings with those in a single pile, a shallow footing(cap alone) and free standing pile groups. From the test results, it is found that the bearing characteristics of cap-soil-pile system are related with load levels and pile spacings. Before yield, the bearing resistance by cap is not fully mobilized, however, as the applied load increases, the bearing resistance of cap approaches to that of cap alone and settlement hardening occurs after yield due to the compaction caused by the contact pressure between cap and soil. By the cap-soil-pile interaction, shaft friction and point resistance of piles considerably increase with dependency of pile spacings. In two layered soil, the increasing effect of dilatancy in dense sandy soil adjacent to pile tips, increases the point resistance of pile.

• KCI Concrete Journal
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• v.13 no.1
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• pp.53-60
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• 2001

Tests of cylindrical concrete specimens under lateral confining pressure of up to 5,000 psi were conducted for two different axial loading cases: monotonic compression and monotonic tension. The purpose of this experimental investigation is to provide stress-strain characteristics of plain concrete in triaxial stress conditions. Lateral confining pressure levels, loading rates, and strength of concrete specimens are varied as parameters. The loading rates are $34.75$\times$10^{-5}$ in/in/sec for fast, $\times$$6.95x10^{-5}$ in/in/sec for normal. and $0.579$\times$10^{-5}$ in/in/sec for slow loading cases. The concrete specimens used in the experiment have compressive strength of 3,500 psi and 6,500 psi, respectively. Findings of this experiment include dependency of the stress-strain behavior of concrete on the above parameters under two different types of loading conditions. The parametric study includes a series of 106 triaxial tests.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.2
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• pp.17-21
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• 2000

In order to correct the strut interference in wind tunnel tests, image methods are conventionally used. Because of their excessive extra runs, some alternatives have been tried to reduce the extra runs. In this study, these alternatives were reviewed and checked by the strut interference evaluation with the panel code, CMARC. The present work shows that the strut interference is free from neither model configuration nor model attitude. This dependency makes the alternatives to the image method unfeasible. The 3-run image method was also evaluated. It worked well even for the exaggerated windshield. At this point, reducing the image runs by neglecting parameters affecting minor influence would be best.

• The Korean Journal of Applied Statistics
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• v.9 no.1
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• pp.17-29
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• 1996

Suppose we have g itesm classified as defective or as nondefective. If we test each item separately, then g tests are required. However, it is possible to test a group of g items so as to detect whether at least one of them is defective, and to proceed to individual testing only if the presense of at least one defective item is indicated. The method is called Dorfman procedure. In this paper, we consider a variant of Dorfman procedure called a hierarchal dorfman procedure. We also consider the curtailment effect resulted from the dependency of the tests. We propose an efficient blood testing procedure. We also present ot heuristic rule of thumb which is simple and easily implementable.