• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.589-596
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• 2014

Joints, fasteners or connected parts frequently have a significant effect on the dynamical behavior of assembled mechanical structures. Therefore, the analytical prediction of structural responses depends on the accuracy of joint modeling. This paper deals with the formulation and analysis of dynamic mechanism for joint flexibilities whose relevant magnitudes of stiffnesses are investigated by using linear and torsional springs. The equation of motion is derived by using a generic joint in the middle of clamped-clamped beam. A reanalysis due to changes in magnitudes of joint stiffnesses is based on the reduced analysis where the binomial series terms are used as basis vectors. The solution procedures are straightforward and the method can be readily used with a general finite element method. The computational effort needed by this approach is usually much smaller than the effort needed for complete vibration analysis. Two numerical examples show that accurate results are obtained efficiently by reducing the number of degree in the reduced model.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.110-118
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• 2000

For reasonable fatigue design and estimation of fatigue durability considered fatigue strength and stiffness of the automotive body structure, many fatigue data must be insured according to the shapes, materials, and welding conditions of the spot welded lap joints. However, because it is actually difficult problem, there is need to establish a new method to be able to predict its fatigue life without any additional fatigue tests. Therefore, In order to improve such problems, in this study, the maximum stress function presenting the $\delta\sigma_{1max}―\delta P$ relation was defined form the relation between $\delta\sigma_{1max}-N_f$ and ${\delta}P-N_f$. By using the fatigue data on the IB type spot-welded lap joints previously obtained from the fatigue test results, fatigue life of the spot-welded lap joint previously obtained from the fatigue test results, fatigue life of the spot-welded lap joint having a certain dimension was tried to predict without any additional fatigue tests. And, its result was verified by ${\delta}P-$N_f$ curves. Obtained conclusion are as follows, 1) a maximum stress function considered the relation of the maximum principal stress, fatigue load, and the effects of geometrical factors of the IB type spot-welded lap joint was suggested. 2) the fatigue life predicted by the maximum principal stress function and the relation of $\delta\sigma_{1max}-N_f$ was well agreed with the fatigue life obtained through the actual fatigue test result. 3) the fatigue life of the IB type spot-welded lap joint having a certain dimension is able to be predicted without any additional fatigue tests from the fatigue life prediction method by the maximum principal stress function.

• Earthquakes and Structures
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• v.6 no.1
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• pp.89-110
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• 2014

Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.207-213
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• 2011

The purpose of this study was to investigate changes in elastic properties of tendon structure of human ankle dorsiflexor following eccentric exercise. Six male subjects(age: $27.3{\pm}2.0$ years, height: $180.3{\pm}1.4$ cm, weight: $82.6{\pm}5.3$ kg) and three female subjects(age: $26.7{\pm}2.9$ years, height: $170.0{\pm}4.2$ cm, weight: $66.6{\pm}1.4$ kg) performed a single bout eccentric exercise consisting of 120 repetitions of maximum eccentric contractions. Prior to and following the eccentric exercise, isometric ankle dorsiflexion strength along with longitudinal ultrasound image of the tibialis anterior(TA) were collected. Muscle strength decreased about 30% after eccentric exercise. From the muscle strength vs. aponeurosis elongation curve, we obtained an index of stiffness. Stiffness of deep aponeurosis of the TA was assessed and found to be decreased from $87.4{\pm}33.56$ N/mm to $73.1{\pm}23.52$ N/mm. The results of this study suggest that decrease in stiffness of the TA aponeurosis following eccentric exercise might have significant implications to functions of the muscle-tendon complex and the involved joint motion and provide better understanding of eccentric exercise in the fields of training and rehabilitation.

• Steel and Composite Structures
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• v.29 no.1
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• pp.1-22
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• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.405-413
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• 2019

Deployable structures are widely used for space mission because of their advantages in storage and transportation coming from its transformability of configuration. The space structures should be designed with high stiffness to withstand the various types of disturbance that they encounter during operation. Especially for the deployable structures, the internal forces loaded on the component or the stiffness at its deployed configuration should be analyzed since they usually consist of the thin and light structures. In this paper, a dynamic model of the scissors structure is established and its deployment behavior is analyzed, especially focusing on the deployment speed and the internal force on each joint. In addition, modal analysis is carried out for the 1-stage and 2-stage scissors structures in order to analyze the stiffness of the scissors structure based on its deployed configuration. The fundamental mode shapes and natural frequencies are analyzed and discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.13-24
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• 1988

A geometrically nonlinear analysis procedure for plane frame structures in order to study the static and dynamic post-buckling behavior of these structures subjected to circulatory forces is presented. The elastic and geometric stiffness matrices, the mass matrix and load correction stiffness matrix are derived from the extended virtual work principle, where the tangent stiffness matrix becomes non-symmetric due to the effects of non-conservative circulatory forces. The dynamic analysis of plane frame structures subjected to circulatory forces in pre- and post-buckling ranges is carried out by integrating the equations of motion directly by the numerically stable Newmark method. Numerical results are presented in order to demonstrate the vality and accuracy of the proposed procedure.

• Journal of Korean Foot and Ankle Society
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• v.7 no.1
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• pp.13-20
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• 2003

Purpose: We analysis the outcome and complications of treatment of lesser toe brachymetatarsia. Materials and Methods: We analysed 28 patients 35 cases of lesser toe brachymetatarsia. Mean post operative follow up period was 2 years 8 months. All of the patients were female and mean age at operation was 21 years old. 2 cases of third metatasal bone and 33 cases of fourth metatarsal bone were operated. 8 metatarsal bones were treated using one staged lengthening with tricortical bone graft and 27 metatarsal bones were treated using callotasis with monofixator. Results: The average amount of lengthening was 13.3mm(12mm-15mm) in one staged lengthening, while 14.4mm(4mm-23mm) in callotasis. Average percentile increase was 28.9%(26%-34%) in one staged lengthening and 32%(18%-46%) in callotasis. The average healing index of callotasis was 76 days/cm (41 days/cm-166 days/cm). Satisfied outcomes in 4 cases of 8 cases (50%) after one staged lengthening and 17 cases of 27 cases (63%) after callotasis. 6 complications in 4 cases were occurred after one staged lengthening; insufficient length gain in 3 cases, fracture on the junction of graft bone and metatarsal bone in 1 case, plantar bowing deformity in 1 case and bony fusion of metatarsophalangeal joint in 1 case. 17 complications in 10 patients were occurred after callotasis ; metatarsophalangeal joint stiffness in 8 cases, metatarsophalangeal joint subluxation in 2 cases, overlengthened metatarsal bone in 2 cases, tapering of callus in 1 case, fracture of callus in 1 case, premature consolidation of callus in 1 case, osteomyelitis of metataral head in 1 case and plantar bowing deformity in 1 case. Conclusion: Although one staged lengthening and gradual lengthening using callotasis are effective treatment for lesser toe brachymetatarsia, complications not rarely occured after lengthening. Insufficient lengthening are most common complication after one staged lengthening while metatarsophalangeal joint stiffness lire most common complication after callotasis.

• Journal of Pharmacopuncture
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• v.5 no.2
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• pp.63-70
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• 2002

Objective: To evaluate the effects of bee venom acupuncture(BVA) on the rehabilitation and quality of life in rheumatoid arthritis(RA) patients Methods: Patients with RA were treated with the BVA therapy twice a week for 3 months. Tender joint counts, swollen joint counts, morning stiffness, Erythrocyte Sedimentation Rate(ESR), C-reactive protein(CRP), patient global assessment, physician global assessment, Korean health assessment questionnaire(KHAQ) were estimated and analyzed before and after BVA therapy. Results: Tender joint counts, swollen joint counts, morning stiffness showed significant decrease after BVA therapy. But, as acute inflammatory reactants, ESR showed no significant difference and CRP showed significant increase after BVA therapy. Patient global assessment, physician global assessment, and KHAQ index showed significant improvement after BVA therapy. Conclusions: BVA therapy can improve rehabilitation and health-related quality of life in RA patients as well as clinical symptoms and signs. Further study is required in more population with large scale including acute inflammatory reaction of BVA therapy.

• Journal of Acupuncture Research
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• v.20 no.6
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• pp.80-88
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• 2003

Objective : This study was performed in order to evaluate the effect of bee venom therapy on rheumatoid arthritis by randomized controlled double blind method. Methods : RA patients were recruited and divided into an experiment group and a control group by random selection. As a double blind test, the experiment group was treated with bee venom injection on acupoints, and the control group was treated with normal saline injection on acupoints twice a week for 8 weeks. Tender joint count, swollen joint count, morning stiffness, pain, health assessment questionnaire, ESR, and CRP were estimated and analyzed at baseline, and at 1 month and 2 months after bee venom therapy. Results : Compared to the control group, the experiment group showed significant decrease in tender joint count, swollen joint count, morning stiffness, and health assessment questionnaire after 2 months. Pain, ESR and CRP showed significant decrease in the experiment group after 1 & 2 months. Conclusions : These results suggests that bee venom therapy could be an effective method in the treatment of patients with rheumatoid arthritis.