• Steel and Composite Structures
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• v.44 no.4
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• pp.545-555
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• 2022

Empirical relationships that capture the nonlinear behavior of headed steel shear stud anchors have been derived from standard push out tests, where the specimens are comprised of large wide flanged steel sections attached to flat concrete slabs via the anchors. However, many composite systems used in practice utilize much smaller steel members and/or steel decking as part of the slab system. Composite open web steel joist systems generally include both of these elements and consequently the nonlinear performance ofthe anchor is not accurately represented by existing models. In this paper, a new empirical relation is presented for open web steel joist systems based on experimental results from a modified push out test that more realistically represent a composite open web steel joist system. The methodology for obtaining the proposed nonlinear function where the response of the system is characterized by two parameters(α and β) is presented. The two-step process for obtaining the two parameters is described and the empirical relation is calibrated with the experimental data. In comparison with existing expressions, the new proposal herein more accurately predicts the high initialstiffness of the system and overall nonlinear system performance.

• Steel and Composite Structures
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• v.25 no.1
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• pp.79-92
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• 2017

Initial damage to a stud due to corrosion, fatigue, unexpected overloading, a weld defect or other factors could degrade the shear capacity of the stud. Based on typical push-out tests, a FEM model and theoretical formulations were proposed in this study. Six specimens with the same geometric dimensions were tested to investigate the effect of the damage degree and location on the static behavior and shear capacity of stud shear connectors. The test results indicated that a reduction of up to 36.6% and 62.9% of the section area of the shank could result in a dropping rate of 7.9% and 57.2%, respectively, compared to the standard specimen shear capacity. Numerical analysis was performed to simulate the push-out test and validated against test results. A parametrical study was performed to further investigate the damage degree and location on the shear capacity of studs based on the proposed numerical model. It was demonstrated that the shear capacity was not sensitive to the damage degree when the damage section was located at 0.5d, where d is the shank diameter, from the stud root, even if the stud had a significant reduction in area. Finally, a theoretical formula with a reduction factor K was proposed to consider the reduction of the shear capacity due to the presence of initial damage. Calculating K was accomplished in two ways: a linear relationship and a square relationship with the damage degree corresponding to the shear capacity dominated by the section area and the nominal diameter of the damaged stud. This coefficient was applied using Eurocode 4, AASHTO LRFD (2014) and GB50017-2003 (2003) and compared with the test results found in the literature. It was found that the proposed method produced good predictions of the shear capacity of stud shear connectors with initial damage.

• Steel and Composite Structures
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• v.36 no.1
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• pp.103-118
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• 2020

The static behavior of grouped large-headed studs (d = 30 mm) embedded in ultra-high performance concrete (UHPC) was investigated by conducting push-out tests and numerical analysis. In the push-out test, no splitting cracks were found in the UHPC slab, and the shank failure control the shear capacity, indicating the large-headed stud matches well with the mechanical properties of UHPC. Besides, it is found that the shear resistance of the stud embedded in UHPC is 11.4% higher than that embedded in normal strength concrete, indicating that the shear resistance was improved. Regarding the numerical analysis, the parametric study was conducted to investigate the influence of the concrete strength, aspect ratio of stud, stud diameter, and the spacing of stud in the direction of shear force on the shear performance of the large-headed stud. It is found that the stud diameter and stud spacing have an obvious influence on the shear resistance. Based on the test and numerical analysis results, a formula was established to predict the load-slip relationship. The comparison indicates that the predicted results agree well with the test results. To accurately predict the shear resistance of the stud embedded in UHPC, a design equation for shear strength is proposed. The ratio of the calculation results to the test results is 0.99.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.91-97
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• 2006

This paper presents the results of push-out test conducted for the perfobond rib shear connectors welded onto steel-concrete composite deck. Push-out test specimen consists of profiled steel sheeting, perfobond rib, reinforcement, and concrete. To provide longitudinal shear resistance between the profiled sheeting and the concrete, perfobond rib with a number of holes was used. The parameters considered in the design of perfobond rib were the spacing and location of holes, and effect of reinforcing bars placed in the holes. To validate the effectiveness of the proposed system, twelve specimens were fabricated and tested. Although the scope of test was limited in nature, the results of test have shown that the perfobond ribs can be effectively used for shear connection in the steel-concrete composite decks.

• Physical Therapy Korea
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• v.21 no.2
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• pp.48-56
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• 2014

The aim of this study to investigate the effects of craniocervical flexion on muscle activities of scapular upward rotators during push-up plus exercise in subjects with winging scapula. Eighteen males with scapular winging were recruited, and each subject performed knee push-up plus and other exercises, in two conditions (craniocervical flexion vs. natural head positions). A surface electromyography (EMG) was used to measure upper trapezius (UT), serratus anterior (SA), and lower trapezius (LT) muscle activity. A paired t-test was used to determine the statistical significance between the different condition with/without applying of craniocervical flexion. UT EMG activity significantly decreased and SA EMG activity significantly increased during knee push-up plus involving the craniocervical flexion compared to the natural head position. However, no significant differences (p>.05) were found in the activity of the LT muscle. The UT/SA ratios with and without craniocervical flexion showed a significant difference (p<.05). These results showed that the knee push-up plus other exercises performed with craniocervical flexion could strengthen the serratus anterior muscle and minimize the activity of the UT muscle.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.2
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• pp.39-47
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• 2019

Purpose : This study was investigated effects of vibration on scapular winging of knee push-up plus exercise. Methods : Twenty-eight female subjects with scapular winging were evaluated after performing knee push-up plus exercise, with or without vibration, three times a week for four weeks. Muscle activation of the serratus anterior and upper trapezius, and the ratio of activation of the upper trapezius to serratus anterior were measured using surface EMG; and scapular winging length was measured by using the caliper. Results : The findings showed that knee push-up plus exercise -with and without- vibration induced a significant increase in muscle activation of serratus anterior (p<.05) and a significant decrease in muscle activation of the upper trapezius (p<.05), the ratio of muscle activation of the upper trapezius to the serratus anterior (p<.05) and scapular winging length (p<.05). There was also a significant difference in muscle activation of the serratus anterior (p<.05) and upper trapezius (p<.05) between control and experimental group at post-test. Conclusion : This study suggests positive clinical effects of knee push-up plus exercise with vibration which enhanced muscle activation of serratus anterior and reduced muscle activation of upper trapezius in person with scapular winging. However, vibration had no effectiveness to improve muscle imbalance between serratus anterior and upper trapezius, and reduce the scapular winging length.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.509-511
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• 2005

KOMPSAT -2 equipped with an optical telescope(MSC) will be launched in this year. It can take images of the earth with push-broom scanning at altitude 685Km. Its resolution is 1m in panchromatic channel with a swath width of 15 km After the MSC is tested and the performance is measured at instrument level, it is installed on satellite. The image passes through the electro-optical system, compression and storage unit and fmally downlink sub-systems. This integration procedure necessitates the functional test of all subsystems participating in the image chain. The objective of functional test at satellite level(Quick Look test) is to check the functionality of image chain by real target image. Collimated moving image is input to the EOS in order to simulate the operational environments as if KOMPSAT -2 is being operated in orbit. The image chain from EOS to data downlink subsystem will be verified through Quick Look test. This paper explains the Quick Look test of KOMPSAT -2 and compares the taken images with collimated input ones.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.63-68
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• 2002

This study performed to evaluated musculoskeletal disorders(MSDs) during sitting work. The musculskeletal system is affected by various work factors such as strength, weight, posture, repetition, duration and exertion. Ergonomic study on sitting work is necessary to evaluate these factors affecting human body. But the strength and work load data by the work factors are insufficient in Korea. Therefore, this study evaluated the work load using the elcctromyogram(EMG) and measured the arm strength by arm posture and push pull work during sitting work. to evaluated muscle load, the vertical height and horizontal angle of arm were adjusted around acromion. And EMG data were recorded on pc during the test.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.268-271
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• 2003

연구지역에 설치된 3개 관정에서 추적자시험 방법 중 단공 주입-회수시험을 실시하였다. Push-pull 추적자시험 자료 분석 결과 종분산지수는 0.086~0.657m의 값을 가지며(Pickens and Grisak, 1981), 지하수 유동속도는 9.07$\times$$10^{-4}$6.14$\times$$10^{-3}$m/min의 값을 보인다(Hall and other, 1991). 또한 계산된 종분산지수와 지하수 유속을 이용하여 종분산계수(3.77$\times$$10^{-4}$ ~ 9.53$\times$$10^{-4}$ $m^2$/min)를 산정하였다. 추적자의 거동특성이 크고 작음을 비교할 수 있게 하는 특성변수(Characteristic property)는 분산지수이므로, 분산지수의 크고 작음에 따라서 추적자의 거동특성이 달라짐에 주의해야 한다..

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.93-94
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• 2016

The resistance of crowd pressure is an important performance to be influential on safety of facility users among performances required for light weight walls of public facilities. This study has empirically evaluated the estimation of size of crowd pressure to be applied to a wall of structure. For the load analysis test, the force plate with stiffness of 28 kN/cm was designed and manufactured. For inspectors, 15 males in the age of 20s were selected. The action of putting load was set as instantaneous push of plate and continuous push. As the load was increased linearly from the weight of inspector, the size of load was indicated as the load ratio. In case of instantaneous force, about 1.18 times the weight of pushing personnel was acted as a load. In case of continuous push, about 0.80 times the weight of pushing personnel was acted as a load.