• Journal of KSNVE
• /
• v.8 no.1
• /
• pp.57-74
• /
• 1998

This paper is concerned with a combination of experimental and analytical investigation aimed at identifying modeling errors, accounted for the lack of correlation between experimental measurements and analytical predictions of the modal parameters for lap joint panels. A nonlinearity vibration test methodology, initiated from the theoretical analysis, is suggested for measurements of dynamic stiffnesses in a lap joint using the rivet fastener. Based on the experimental evidence on discrepancies between measured and predicted frequencies, improved finite element models of the joint are developed using PATRAN and ABAQUS, in which the beam element size is evaluated from the joint stiffnesses readily determined in the test. The beam element diameter as a principal design parameter is tuned to match experimental results within the evaluated bound value. Frequencies predicted by the proposed numerical model are compared with frequencies measured by the test. Improved predictions based on this new model are observed when compared with those based on conventional modeling practices.

• Explosives and Blasting
• /
• v.34 no.3
• /
• pp.10-16
• /
• 2016

Recently, transition from open pit to underground mining in limestone mines is an increasing trend in Korea due to environmental issues such as noise, dust and vibrations caused by crushers and equipment. The severe damages in the surrounding rock mass of underground opening caused by explosive blasting may lead to rock fall hazards or casualties. It is well known that variables which mainly affect blast-induced rock falls in underground mining are: blast vibration level, joint orientation and distribution and shape of the cross sections of underground structures. In this study, UDEC program, which is a DEM code, is used to simulate blast vibration-induced rock fall in underground openings. Variation of joint space, joint angle and joint normal stiffness was considered to investigate the effect of joint characteristics on the blast vibration-induced rock fall in underground opening. Finally, jointed rock mass models considering blast-induced damage zone were examined to simulate the critical blast vibration value which may cause rock falls in underground opening.

• Archives of Reconstructive Microsurgery
• /
• v.11 no.1
• /
• pp.11-18
• /
• 2002

Large soft tissue defects around the knee joint are known to significantly diminish joint function. Severe soft tissue defects on the anterior aspect of the knee joint especially bring on significant joint motion limitation. Although simple split skin grafts can cover the skin defect, the progressing scar contracture of the grafted skin causes joint stiffness. One of the best solutions of large soft tissue defects around the knee joint is covering the defect with a good quality skin flap. Separated flaps with one vascular pedicle are good candidates for covering anterior and posterior aspects of the joint for example. Authors performed 12 cases of combined scapular and latissimus dorsi free flaps from 1984 to 2000. Among them, we experienced 5 cases of knee joint defect covering using the double free flap for coverage of the soft tissue defect with preservation of the knee joint function and satisfactory results. The system of flaps based on the subscapular artery and vein provides a variety of composite free flaps. The possible flaps that can be harvested based on this single vascular pedicle include the scapular and parascapular skin flap, the serratus anterior and latissimus dorsi muscular flap, the lateral scapular bone flap, the latissimus dorsi-rib flap, and the serratus anterior-rib flap. This combined flap is available for multiple tissue defects or complex defects because it can be incorporated with skin, muscle and bone flaps. A main advantage is the independent vascular pedicles of each component, which allow freedom in orientation of each components. Consequently it can be freely applied to any form of three dimensional defects on the upper and lower extremities. The combination of scapular cutaneous flap and latissimus dorsi musculocutaneous flap can be resurfaced for massive cutaneous defects on the extremities. We report the use of the combined scapular and latissimus dorsi free flap in five patients to reconstruct massive defects on the extremities with resultant improved joint function. There was no flap failure and minimal complications and disadvantages. The anatomy of this flap is reviewed and the indication and advantages are discussed. All of the five flaps survived and there was no scar contracture affecting the joint motion.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.1
• /
• pp.203-208
• /
• 2002

In order to reduce the booming noise caused by first bending mode of a drive shaft, this paper proposes a simulation program for prediction of the bending mode frequency of any tubular shaft. This program consists of a pre-processor for modeling of geometrical shape of the drive shaft with boundary conditions of various joints, a processor for constructing of global finite element matrices using beam elements and an eigen-solver based on MATLAB program. Using this simulation program, the effective and accurate FE model far a shaft attached to vehicle can be obtained by aid of database for stiffness of each joint. Thus the resonance frequencies and mode shapes of a shaft can be calculated accurately. Because the effect of the resonance on interior noise can be verified, more improved shaft will be proposed at the early stage of design.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.6
• /
• pp.1446-1454
• /
• 1990

A systematic method of design modification to reduce the influence of impact from multiple clearances in a planar four bar mechanism is developed. For this purpose, an optimization method is used with the objective function which is the linear sum of the Earles and Wu criteria for every joints with clearances. One coil spring is attached to a joint of limited range of revolution to reduce the undesirable dynamic effects due to clearances at joints. The stiffness of the coil spring and its pre-loading angle are chosen as design variables. A numerical example is taken for a four bar mechanism. The initial and modified mechanisms are compared using a clearance mechanism analysis technic to see the difference in dynamic effects due to contact loss. It is found that the modified mechanism produces much more smooth joint contact forces than the original design.

• Structural Engineering and Mechanics
• /
• v.40 no.3
• /
• pp.297-313
• /
• 2011

As bridge conditions in the United States continue to deteriorate, rapid bridge replacement procedures are needed. Decked precast prestressed concrete (DPPC) girders are used for rapid bridge construction because the bridge deck is precast with the girders eliminating the need for a cast-in-place slab. One of the concerns with using DPPC girders as a bridge construction option is the durability of the longitudinal joints between girders. The objectives of this paper were to propose a method to use a spring element modeling procedure for representing welded steel connector assemblies between adjacent girders in DPPC girder bridges, perform a preliminary study of bridge performance under multiple loading scenarios and bridge configurations, and discuss model flexibility for accommodating future field data for model verification. The spring elements have potential to represent the contribution of joint grout materials by altering the spring stiffness.

• Journal of the Korean Society for Precision Engineering
• /
• v.5 no.2
• /
• pp.23-32
• /
• 1988

A control system for improving the moving accuracy of robotic manipulators with elastic joints is devloped. The dynamics of manipulator system is splitted into two sub-dynamics; of arm-link and actuator rotor- link, which are coupled statically through joint torque. Two contorl loops are implemented respectively around both sub-dynamic systems. Computed torque algorithm with acceleration feedback is used for the arm-link control loop, and for the actuator rotor-link control loop PID algorithm is adopted. The resulting control system is tested through a series of computer simulation for a PUMA type manipulator, The reaults show good performance of the developed control system for wide range of joint stiffness and moving speed.

• Journal of Korean Biological Nursing Science
• /
• v.17 no.1
• /
• pp.1-10
• /
• 2015

Purpose: This study is aimed at grasping the benefit/effect of program promoting intention to exercise performance based theory of planned behavior in the elderly who live in the rural areas with degenerative joint diseases (DJDs). Methods: There were 2 groups; 32 people in the experimental group and 24 in the control group, all above the age of 60. Program promoting intention to exercise performance was applied to the experimental group for 12 weeks. Results: Compared to the control group, the experimental group showed a significant the increase of attitude towards exercise, subjective norm, perceived behavior control, exercising intention, and exercise performance. Also, pain as a physical function, joint stiffness, ADLs, body flexibility, parallel, perceived health state as a psychological function, and life satisfaction were significantly improved. Conclusion: We expect that program promoting intention to exercise performance is used in nursing practice for the elderly with DJDs are needed to manage lifestyle.

• Steel and Composite Structures
• /
• v.33 no.2
• /
• pp.277-298
• /
• 2019

Concrete filled steel tubular (CFST) column joints with composite beams have been widely used as lateral loading resisting elements in civil infrastructure. To better utilize these innovative joints for the application of structural seismic design and analysis, it is of great importance to investigate the dynamic behavior of the joint under cyclic loading. With this aim in mind, a novel phenomenal model has been put forward in this paper, in which a Bouc-Wen hysteresis component is employed to portray the strength and stiffness deterioration phenomenon caused by increment of loading cycle. Then, a modified chicken swarm optimization algorithm was used to estimate the optimal model parameters via solving a global minimum optimization problem. Finally, the experimental data tested from five specimens subjected to cyclic loadings were used to validate the performance of the proposed model. The results effectively demonstrate that the proposed model is an easy and more realistic tool that can be used for the pre-design of CFST column joints with reduced beam section (RBS) composite beams.

• Advances in concrete construction
• /
• v.8 no.2
• /
• pp.91-100
• /
• 2019

In this paper three damaged exterior RC beam-column joints made of recycled aggregate concrete (RAC) were repaired. The aim of the study was to restore back the lost capacity of the beam-column joint to the original state or more. A relatively cheap material locally available galvanized steel welded wire mesh (GSWWM) of grid size 25 mm was used to confine the damaged region and then jacketed with cement mortar. Repaired specimens were also subjected to similar cyclic displacement as those of unrepaired specimens. Seismic parameters such as load carrying capacity, ductility, energy dissipation, stiffness degradation etc. were analyzed. Results show that repaired specimens exhibited better seismic performance and hence the adopted repairing strategies could be considered as satisfactory. These findings would be helpful to the field engineers to adopt a suitable rapid and cost efficient repairing technique for restoring the damaged frame structural joints for post earthquake usage.