• Steel and Composite Structures
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• v.36 no.4
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• pp.447-462
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• 2020

The paper aims to investigate the mechanical mechanism and seismic effect of stiffeners in blind bolt endplate connection to CFST column. A precise 3D finite element model with considering the cyclic properties of concrete and steel materials was established, and the efficiency was validated through monotonic and cyclic test data. The deforming pattern and the seismic performance of the unstiffened and stiffened blind bolt endplate connections were investigated. Then a parametric analysis was conducted to analyze the contribution of stiffeners and the joint working behaviors with endplate under cyclic load. The joint stiffness classifications were compared and a supplement stiffness classification method was proposed, and the energy dissipation ability of different class connections were compared and discussed. Results indicated that the main deformation pattern of unstiffened blind bolt endplate connections was the local bending of end plate. The vertical stiffeners can effectively alleviate the local bending deformation of end plate. And influence of stiffeners in thin endplate and thick endplate was different. Based on the stiffness of external diaphragm welded connection, a more detailed rigidity classification was proposed which included the pin, semi-rigid, quasi-rigid and rigid connection. Beam was the main energy dissipation source for rigid connection. For the semi-rigid and quasi-rigid connection, the extended endplate, stiffeners and steel beam would all participate in the energy dissipation.

• Journal of muscle and joint health
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• v.16 no.1
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• pp.46-54
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• 2009

Purpose: The purpose of the study was to compare the effects of the Tai Chi self-help program with a self-help program on pain, stiffness, physical functioning, and fear of falling in women with osteoarthritis. Method: Total of 82 women with Osteoarthritis recruited from outpatient clinics or community health centers were randomly assigned either to a Tai Chi self-help group or a self-help group. Thirty subjects in the Tai Chi self-help group and 39 in the self-help group completed posttest measures(pain, stiffness, physical functioning, and fear of falling) at 6 months. Results: After the 6 month study period, the subjects in the Tai Chi self-help group reported significantly less difficulties in performing daily activities(mean difference=-0.16 vs. 6.19 for the self-help), and less fear of falling(mean difference=-3.20 vs. 0.27 for the self-help) than those in the self-help group. There were no significantly differences in pain and stiffness between the groups. Conclusion: The Tai Chi combined with self-help program was more effective than the self-help only program in reducing difficulties in performing daily activities and fear of falling in women with Osteoarthritis. Whether these changes prevent fall episodes requires further study.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.145-157
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• 2008

Load transfer efficiency (LTE) reflects the structural performance of doweled and undoweled joints of Jointed Concrete Pavement (JCP). A 3-dimensional (3-D) model of JCP was built using ABAQUS software in this study. Three concrete slabs were placed on bonded sublayers composed of a base and subgrade. Spring elements were used to connect the adjacent slabs at joints. Different spring constants were input to the model to simulate different joint stiffness of the concrete pavement. The LTE of the joint increased with an increase of the spring constant. The effects of material properties and geometric shape on the behavior of JCP were analyzed using different elastic modulus and thickness of the slab and base in the modeling. The results showed the elastic modulus of the subgrade affected the behavior of the slab and LTE more than that of the base and the thickness of the slab and base. The effects of a negative temperature gradient on the behavior of the slab and LTE were more than that of positive and zero temperature gradients. Joints with low stiffness were more sensitive to the temperature gradient of the slab.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.3
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• pp.19-28
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• 2018

Key factors that ensure competitiveness of modular unit include consistent high quality and connection condition that ensures high structural performance while minimizing the overall scale of the on-site process. However, it is difficult to evaluate the structural performance of the connection of modular unit, and its structural analysis and design method can be different depending on the connection to its development, which affects the seismic performance of its final design. In particular, securing the seismic performance is the key to designing modular systems of mid-to-high-rise structure. In this paper, therefore, the seismic performance of the modular system with bracket-typed fully restrained moment connections according to stiffness and the shapes of various connection members was evaluated through experimental and analytical methods. To verify the seismic performance, a cyclic loading test of the connection joint of the proposed modular system was conducted. As a result of this study, theoretical values and experimental results were compared with the initial stiffness, hysteresis behavior and maximum bending moment of the modular system. Also, the connection joint was modeled, using the commercial program ANSYS, which was then followed by finite element analysis of the system. According to the results of the experiment, the maximum resisting force of the proposed connection exceeded the theoretical parameters, which indicated that a rigid joint structural performance could be secured. These results almost satisfied the criteria for connection bending strength of special moment frame listed on KBC2016.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.82-89
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• 2010

Ankle-foot orthosis with an artificial pneumatic muscle which is intended for the assistance of plantarfelxion torque was developed. In this study, power pattern of the device in the various pneumatics and the effectiveness of the system were investigated. The pneumatic power was provided by ankle-foot orthosis controlled by user‘s physiological signal, that is, muscular stiffness in soleus muscle. This pneumatic power can assist plantarflexion torque of ankle joint. The subjects performed maximal voluntary isokinetic plantarflexion motion on a biodexdynamometer in different pneumatics, and they completed three conditions: 1) without wearing the orthosis, 2) wearing the orthosis with artificial muscles turned off, 3) wearing the orthosis activated under muscular stiffness control. Through these experiments, we confirmed the effectiveness of the orthosis and muscular stiffness control using the analyzing isokinetic plantarflexion torque. The experimental results showed that isokinetic torques of plantarflexion motion of the ankle joints gradually increased in incremental pneumatic. The effectiveness of the orthosis was -7.26% and the effectiveness of the muscular stiffness control was 17.83% in normalized isokinetic plantarflexion torque. Subjects generated the less isokinetic torques of the ankle joints in wearing the orthosis with artificial muscles turned off, but isokinetic torques were appropriately reinforced in condition of wearing the orthosis activated under muscular stiffness control(17.83%) compared to wearing the orthosis(-7.26%). Therefore, we respect that developed powered orthosis is applied in the elderly that has weak muscular power as the rehabilitation equipment.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.249-255
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• 2016

Objective: This purpose of this study was to analyze the relationship between dimensionless leg stiffness and kinetic variables during gait performance, and its modulation with body weight. Method: The study sample consisted of 10 young women divided into 2 groups (Control, n=5 and Obese, n=5). Four camcorders (HDR-HC7/HDV 1080i, Sony Corp, Japan) and one force plate (AMTI., USA) were used to analyze the vertical ground reaction force (GRF) variables, center of pressure (COP), low limb joint angle, position of pelvis center and leg lengths during the stance phase of the gait cycle. Results: Our results revealed that the center of mass (COM) displacement velocity along the y-axis was significantly higher in the obese group than that in control subjects. Displacement in the position of the center of the pelvis center (Z-axis) was also significantly higher in the obese group than that in control subjects. In addition, the peak vertical force (PVF) and dimensionless leg stiffness were also significantly higher in the obese group. However, when normalized to the body weight, the PVF did not show a significant between-group difference. When normalized to the leg length, the PVF and stiffness were both lower in the obese group than in control subjects. Conclusion: In the context of performance, we concluded that increased dimensionless leg stiffness during the gait cycle is associated with increased velocity of COM, PVF, and the change in leg lengths (%).

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.94-101
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• 2010

Recently, the interest of precast concrete is increased for rapid construction in construction fields. Experimental study about the shear performance of the joint between hollow core slabs which have internal core to reduce their weight was performed. Main test variables were thickness of the topping concrete and existence of the wiremesh. Total 8 specimens including 4 in-plane shear and 4 out of plane shear were tested. Test results were analyzed in terms of cracking load, failure load, failure aspect, stiffness and ductility, and compared its design load to develop optimum design details. Test results indicated that the shear performance of the non-shrinkage mortar specimen was similar to that of 30mm thickness topping concrete specimen, and the effect of wiremesh reinforcement did not affect the failure load or stiffness of the specimens but the increase of ductility. And this paper presents the comparison results of the test results and design load to provide the optimum detail of the joint design between the hollow core slabs.

• Physical Therapy Korea
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• v.25 no.2
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• pp.13-21
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• 2018

Background: After a stroke, the patient may have abnormal muscle tone due to abnormal alignment. Physical therapists have used stretching, neural mobilization other methods to treat patients after stroke. In addition, joint mobilization is also used to stimulation in pathway of cervical segmental region and to normal cervical spine alignment. Objects: The purpose of this study was to determine whether Maitland cervical spine mobilization has an immediate effect on muscle tone and stiffness of upper extremity. Methods: Thirty subjects were divided into a experimental group ($n_1=10$), a placebo group ($n_2=10$), and a control group ($n_3=10$). The Maitland cervical spine mobilization was applied in the supine position. Immediately after the intervention, muscle tone and stiffness of biceps brachii, brachioradialis, deltoid, and pectoralis major were measured using Myoton(R)PRO. In the placebo group, sham mobilization was applied to the fifth and sixth cervical vertebra, and the control group was instructed to control breathing. Results: In the experimental group, significant differences were found in muscle tone and stiffness of biceps brachii and brachioradialis in comparison with the affected side and the non-affected side before the intervention (p<.05), whereas there was no significant difference after the intervention (p>.05). Muscle tone of biceps brachii on the non-affected side and pectoralis major on the affected side was significantly decreased before and after the intervention (p<.05). The placebo and control group showed no changes on the non-affected and affected side, and no significant differences were detected before and after the intervention. All the groups revealed no significant differences in muscle tone and stiffness of upper extremity before and after the intervention. Conclusion: This study suggests that the application of Maitland cervical spine mobilization enhanced muscle tone of upper extremity on the involved side symmetrically, and influenced a decrease in muscle tone.

• Research in Community and Public Health Nursing
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• v.21 no.1
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• pp.118-127
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• 2010

Purpose: The purpose of this study was to evaluate the effects of a Tai-Chi exercise program on subjective health and physiological function index. Methods: This study was designed as non-equivalent control group pretestposttest research. Eighteen women in each group completed the posttest with an attendance rate of 78.3 % after 12 weeks. The Tai Chi exercise program was provided two times a week over three months for the experimental group, but no program for the control group. A questionnaire was used for subjective health index, which consisted of Korean-WOMAC Index for joint stiffness, K-HAQ for physical disability, EQ-5D for quality of life and perceived health status, and CES-D for depression. To measure the effect on the physiological function index, femoral muscle strength, shoulder joint and back flexibility were measured. Results: All variables except left anterior femoral muscle strength had significant homogeneity between the two groups. There were statistically significant differences between the experimental group and the control group in joint stiffness (t=-2.165, p=.03), physical disability (t=-2.231, p=.038), EQ-5D index (t=3.783, p=.001), perceived health status (t=-2.349, p=.025) and femoral posterior muscle strength (t=2.487, p=.038). Conclusion: The Tai-Chi exercise program was beneficial for women with arthritis in rural communities.

• Journal of muscle and joint health
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• v.17 no.1
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• pp.68-78
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• 2010

Purpose: This study was conducted to determine the effects of Tai-Chi exercise and self-help management program applying laughter therapy in patients with osteoarthritis. Methods: This quasi-experimental study recruited a sample of 61 patients with osteoarthritis (experimental group: 30, control group: 31) through the community healthcare centers located in Seoul and Kyung Gi area. The primary outcome measures included symptoms of osteoarthritis, basic physical performance, fatigue, and depression assessed before and after the study. The data were analyzed using SPSSWIN V. 12.0. Results: At the end of the six-week intervention, left shoulder flexibility (t=2.011, p=.049), 6m walking speed (t=3.639, p=.001), and right balance (t=-2.30, p=.025) were significantly improved in the control group. Fatigue (t=3.012, p=.004), stiffness (t=2,093, p=.041), right shoulder flexibility (t=2.138, p=.037), right balance (t=-2.065, p=.043), and 6m walking speed (t=2.683, p=.009) were significantly improved in the experimental group. Conclusion: A twice a week, 6-week tai-chi exercise self-help management program applying laughter therapy is effective in decreasing fatigue and stiffness. Osteoarthritis is one of common chronic diseases that the patients should be required to continue self management for the rest of their life. Therefore, there is a need to develop the more effective self-help management program and nursing intervention to motivate them to maintain their own self-help management.