• International Journal of High-Rise Buildings
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• v.9 no.2
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• pp.155-166
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• 2020

To connect exterior reinforced concrete (RC) columns with the steel belt truss, the gusset plates are welded to the steel plates embedded in the RC column. Then, the concrete around an embedded plate is very likely to be damaged by the heat input from a long-time (6 to 48 hours) welding of the embedded and gusset plates at a joint between RC columns and steel belt truss. However, very few studies have assessed the concrete damage caused by the welding heat between embedded and gusset plates, and no clear onsite solution has been found. In this paper, experimental tests have been carried out on 4 full-scale specimen to analyze the effect of long-time (about 6 hours) onsite welding (1-side welding and 3-side welding) between a gusset plate and an embedded plate in high strength concrete with compressive strength of 55 MPa and 80 MPa on RC columns. The effect of the long-time welding heat of embedded and gusset plates, which are used in real high-rise building construction sites, on concrete is analyzed in terms of the following three items: 1) temperature distribution, 2) pattern and characteristics of cracks, and 3) effect of the cracks on the compressive strength of RC column. Based on the experimental results, even though the heat input up to about 150? from the long-time onsite welding on the high-strength concrete column for the joint could result in concrete cracks in a radial form, it is found that the welding cracks have no effect on the axial stiffness and strength of the concrete column.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.441-448
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• 2020

In this study, the engineering characteristics of CLSM mixed with GBFS and GF were identified to review the applicability as a replacement material and further evaluate the recharge and field applicability as a joint filler material. This study has resulted in the following findings. First, Using more than 30% of GBFS to replace FA enabled bleeding control through improved fluidity. Moreover, it has been confirmed that effective strength and proper quality can be achieved when it was applied as a refiller and joint filler material with higher early strength than the base material. Second, When using more than 30% of FNS to replace sand, it was found that adding 0.3~0.35 of the AE agent is effective for bleeding control through improved fluidity. Third, When using more than 30% of both GBFS and FNS in combination, it was found that adding 0.3~0.35 of the AE agent is effective for bleeding control through improved fluidity. Also, it was confirmed that proper mixing of 15~60% of GF secured the effective strength and desired quality as a refiller and joint filler material. Fourth, The relationship between the superficial level and internal micro pores of CLSM from the curing process needs to be discussed and reviewed in more detail through further research studies.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.491-501
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• 2012

Generally, a steel pier-foundation has been designed and constructed with a anchor frame. However, because of the complicated design and construction, the foundation's size has become large and has been overdesigned. In this study, three specimens were made and the tests were conducted to suggest a new shape in regard to the pier-foundation's joint details using the high performance steel. One of the specimens was made up of the general anchors and the anchor frame. Another specimen consisted of the high tension anchors and the studs, and the other specimen was composed of the high tension anchors and the inner steels. After the performance of each specimen was compared and analyzed, the behavior characteristics according to the joint were analyzed.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.9-16
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• 2005

This paper presents the development of new anisotropic conductive adhesives with enhanced thermal conductivity for the wide use of adhesive flip chip technology with improved reliability under high current density condition. The continuing downscaling of structural profiles and increase in inter-connection density in flip chip packaging using ACAs has given rise to reliability problem under high current density. In detail, as the bump size is reduced, the current density through bump is also increased. This increased current density also causes new failure mechanism such as interface degradation due to inter-metallic compound formation and adhesive swelling due to high current stressing, especially in high current density interconnection, in which high junction temperature enhances such failure mechanism. Therefore, it is necessary for the ACA to become thermal transfer medium to improve the lifetime of ACA flip chip joint under high current stressing condition. We developed thermally conductive ACA of 0.63 W/m$\cdot$K thermal conductivity using the formulation incorporating $5 {\mu}m$ Ni and $0.2{\mu}m$ SiC-filled epoxy-bated binder system to achieve acceptable viscosity, curing property, and other thermo-mechanical properties such as low CTE and high modulus. The current carrying capability of ACA flip chip joints was improved up to 6.7 A by use of thermally conductive ACA compared to conventional ACA. Electrical reliability of thermally conductive ACA flip chip joint under current stressing condition was also improved showing stable electrical conductivity of flip chip joints. The high current carrying capability and improved electrical reliability of thermally conductive ACA flip chip joint under current stressing test is mainly due to the effective heat dissipation by thermally conductive adhesive around Au stud bumps/ACA/PCB pads structure.

• Journal of Korean Institute of Industrial Engineers
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• v.28 no.2
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• pp.216-222
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• 2002

The ergonomic human model can be considered as a tool for the evaluation of ergonomic factors in vehicle design process. The proper anthropometric data on driver's postures are needed in order to apply a human model to vehicle design. Although studies on driver's posture have been carried out for the last few decades, there are still some problems for the posture data to be applied directly to the human model due to the lack of fitness because such studies were not carried out under the conditions for the human model application. In the traditional researches, the joint angles were evaluated by the categorized data, which are not appropriate for the human model application because it is so extensive that it can not explain the posture evaluation data in detail. And the human models require whole-body posture evaluation data rather than joint evaluation data. In this study a postural evaluation function was developed not by category data but by the concept of the loss function in quality engineering. The loss was defined as the discomfort in driver's posture and measured by the magnitude estimation technique in the experiment using a seating buck. Four loss functions for the each joint - knee, hip, shoulder, and elbow were developed and a whole-body postural evaluation function was constructed by the regression analysis using these loss functions as independent factors. The developed postural evaluation function shows a good prediction power for the driver's posture discomfort in validation test. It is expected that the driver's postural evaluation function based on the loss function can be used in the human model application to the vehicle design process.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.417-424
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• 2003

A bearing failure in RCS(Reinforced Concrete Column and Steel Beam) system is recognized as one of the distinct joint failure modes for the composite frames. Vertical and transverse reinforcement in addition to concrete are effective for better transfer of vortical forces through concrete bearing. To examine the effect of the vertical bars, tie bars, a U-type detail developed in this study and concrete confinement, local bearing tests were conducted using 22 small-scale concrete block specimens. Test results show that vertical reinforcement and tie bars mainly contribute to the bearing capacity. However larger amounts of tie reinforcement are required than those recommend from ASCE guidelines, to apply the nominal concrete strength as 2 $f_{ck}$ over the bearing area. Cross ties are proved to be highly effective for resisting the vertical forces. Maximum bearing strength can be increased upto 2.5 $f_{ck}$ . An accurate prediction model for bearing strength is proposed for better design of the composite Joint.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.3
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• pp.45-52
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• 2011

It is known that test methods to evaluate solder joint reliability are die shock test, die shear test, 3points bending test, and thermal shock test. The present study investigated the effects of failure mode on 3 types (as-reflowed, $85^{\circ}C$/85%RH treatment, and $150^{\circ}C$/10hr aging) of solder joints for flip-chip BGA package by using various test methods. The test methods and configurations are reported in detail, i.e. die shock, die shear, 3points bending, and thermal shock test. We focus on the failure mode of solder joints under various tests. The test results indicate that die shock and die shear test method can reveal brittle fracture in flip-chip ball grid array (FCBGA) packages with higher sensitivity.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.437-447
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• 2011

In this study, the lower limbs joints were analyzed for features based on the biomechanical characteristics of landing techniques according to height and landing on the ground type (flats and downhill). In order to achieve the objectives of the study, changes were analyzed in detail contents such as the height and form of the first landing on the ground at different angles of joints, torso and legs, torso and legs of the difference in the range of angular motion of the joint, the maximum angular difference between joints, the lower limbs joints difference between the maximum moment and the difference between COM changes. The subjects in this study do not last six months did not experience joint injuries 10 males in 20 aged were tested. Experimental tools to analyze were the recording and video equipment. Samsung's SCH-650A model camera was used six units, and the 2 GRF-based AMTI were used BP400800 model. 6-unit-camera synchronized with LED (photo cell) and Line Lock system were used. the output from the camera and the ground reaction force based on the data to synchronize A/D Syc. box was used. To calculate the coordinates of three-dimensional space, $1m{\times}3m{\times}2m$ (X, Y, Z axis) to the size of the control points attached to the framework of 36 markers were used, and 29 where the body was taken by attaching a marker to the surface. Two kinds of land condition, 40cm and 60cm in height, and ground conditions in the form of two kinds of flat and downhill slopes ($10^{\circ}$) of the landing operation was performed and each subject's 3 mean two-way RM ANOVA in SPSS 18.0 was used and this time, all the significant level was set at a=.05. Consequently, analyzing the landing technique as land form and land on the ground, the changes of external environmental factors, and the lower limbs joints' function in the evaluation were significantly different from the slopes. Landing of the slop plane were more load on the joints than landing of plane. Especially, knee extensor moment compared to the two kinds of landing, slopes plane were approximately two times higher than flat plane, and it was statistical significance. Most of all not so much range of motion and angular velocity of the shock to reduce stress was important. In the further research, front landing as well as various direction of motion of kinetic, kinetic factors and EMG variables on lower limbs joints of the study in terms of injury-prevention-approach is going to be needed.

• Steel and Composite Structures
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• v.49 no.5
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• pp.517-532
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• 2023

Tower structures have been widely used in communication and transmission engineering. The failure of joints is the leading cause of structure failure, which make it play a crucial role in tower structure engineering. In this study, the aluminum alloy three tube tower structure is taken as the prototype, and the middle joint of the tower was selected as the research object. Three different stainless steel-aluminum alloy composite joints (SACJs), denoted by TA, TB and TC, were designed. Finite element (FE) modeling analysis was used to compare and determine the TC joint as the best solution. Detail requirements of fasteners in the TC stainless steel-aluminum alloy composite joint (TC-SACJ) were designed and verified. In order to systematically and comprehensively study the mechanical properties of TC-SACJ under multi-directional loading conditions, the full-scale experiments and FE simulation models were all performed for mechanical response analysis. The failure modes, load-carrying capacities, and axial load versus displacement/stain testing curves of all full-scale specimens under tension/compression loading conditions were obtained. The results show that the maximum vertical displacement of aluminum alloy tube is 26.9mm, and the maximum lateral displacement of TC-SACJs is 1.0 mm. In general, the TC-SACJs are in an elastic state under the design load, which meet the design requirements and has a good safety reserve. This work can provide references for the design and engineering application of aluminum alloy tower structures.

• Korean Journal of Applied Biomechanics
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• v.33 no.1
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• pp.25-33
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• 2023

Objective: The purpose of this study was to investigate the differences in static arch height and ankle stability according to the preference for insole height and hardness in the arch area. Method: The study participants were 20 adult males (age: 22.7 ± 1.8 yrs., height: 175.3 ± 4.3 cm, body weight: 72.5 ± 7.7 kg). First, the arch heights of all subjects were measured in static postures (sitting and standing). The inversion and eversion movements of the ankle joint were analyzed during walking (1.3 m/s & 1.7 m/s) and running (2.7 m/s & 3.3 m/s). The variables (static arch height, and inversion and eversion angle of ankle joint) were compared by classifying groups according to the preference for the height and hardness of the arch of the insole. First, it was divided into a high arch insole preference group (HAG, n=8) and a low arch insole preference group (LAG, n=12) according to the preference for the arch height of the insole. Second, it was divided into a high hardness insole preference group (HHG, n=7), medium hardness insole preference group (MHG, n=7), and low hardness insole preference group (LHG, n=6), according to the preference for the arch hardness of the insole. Results: First, the range of motion (ROM) of inversion-eversion at the ankle joint during walking was statistically smaller in HAG than in LAG (p<.05). Second, the arch height change of HHG was statistically greater than that of MHG and LHG (p<.05). Conclusion: In the case of flexible flat feet with a large change in arch height, providing a high hardness arch insole that can disperse foot pressure can improve comfort. It was found that people with high medial and lateral sway of the ankle joint preferred a low arch insole, but it is necessary to differentiate and compare the insole heights of the arch part in detail. In addition, in the case of fast motion such as running, the preference for the arch height and hardness of the insole was not related to the static arch height and ankle stability.