• Journal of the Korean Society of Physical Medicine
• /
• v.13 no.4
• /
• pp.51-58
• /
• 2018

PURPOSE: This study was conducted to determine if the Harrison hip score (HHS), a tool for assessing hip joint function, and the Burg balance scale (BBS), a general balance assessment tool, actually reflect the balance ability of total hip arthroplasty (THA) patients 3 months after surgery. In addition, this study investigated the initial weight distribution strategy for bilateral lower extremity after THA surgery to understand the balance of THA patients. METHODS: Fourteen 3-month THA patients performed static dual standing and sit-to-stand (STS) tasks. Ground reaction forces on each leg were collected to calculate the weight distribution symmetricity (SWD), and the HHS, functional HHS (f-HHS), and BBS were evaluated. Correlation analyses between SWD and the HHS (also f-HHS) and BBS were then applied to the THA patients. RESULTS: The correlations between functional evaluation tools (HHS, f-HHS, BBS) and SWD were weak strength for the static balance task, but moderate for the dynamic STS task. Among the evaluation tools used in the present study, f-HHS was most useful for evaluation of dynamic balance ability. CONCLUSION: The results suggest that use of HHS, f-HHS, and BBS as functional evaluation tools does not provide meaningful information regarding balance ability, but that they are useful for evaluating dynamic balance ability of THA patients. The dynamic balance ability at 3 months after THA seems to be under development.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.1
• /
• pp.10-19
• /
• 2010

ANSYS multi-physics software was applied to solve the coupled dynamic problem related to a full-scale TLP foundation for floating wind turbines. In this coupled dynamics simulation, the forced oscillation imposed on the tethers' top resulting from the sway of the wind turbine platform and the self-excited vortex-induced vibration (VIV) along the tether span have been taken into account. The stability of this tensioned tether system has been validated in the form of separate static and dynamic analyses. The dynamic characteristics of the tensioned tether linked to the floating wind turbine were analyzed by the resultant modal form and its corresponding vortex shedding pattern. The calculated result shows that even a slight forced oscillation imposed on the tethers' top leads to the VIV amplification and enhances the risk of instability in the case of low pretension. It is also found that the "synchronization" would be aggravated when the top tension decreases and the "2P" vortex shedding mode takes place. The increased top tension imposed on the tethers contributes to the stability of the tensioned legs by diminishing the oscillation amplitude markedly.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.688-692
• /
• 2001

Three-dimensional experimental analyses were conducted in the pulverizer simplified isothermal model. The experimental model was constructed on a 1/3.5 scale of 500MW pulverized coal boiler. The purpose of this study is to investigate the characteristics of coal particle separator and the pressure loss in the pulverizer models with dynamic classifier. Without regards a shape of separator top, the results showed that the increase of dynamic classifier rpm was induced in finer coal particle. But the capacity of total mass per minute was reduced. Also, the increase of dynamic classifier rpm had no effect on total pressure loss, but an increase of inlet velocity was induced that the rise of total pressure loss in the pulverizer models with dynamic classifier.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1997.04a
• /
• pp.241-248
• /
• 1997

The super-structure in a soil-structure interaction analysis is commonly idealized as lumped parameter system. In this study, the complex shear wall structure is modeled using three different kinds of modeling techniques : 1) full FEM comparatively as an exact solution, 2)equivalent shear spring model assuming mainly shear deformations of the wall, 3) equivalent beam-stick model made by independent static analysis. Dynamic characteristics due to three different modeling methods are compared and investigated before performing structural response analysis. The beam-stick model in comparison to shear spring model gives closer dynamic responses when compared with the full FEM, even though it requires additional unit load static analyses.

• Wind and Structures
• /
• v.16 no.1
• /
• pp.93-115
• /
• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6A
• /
• pp.935-941
• /
• 2006

The hysteretic behavior of steel structure under cyclic and dynami loading such as earthquake is different to that under static loading. Because structural steels on dynamic deformation is different to static deformation with respect with mechanical characteristics and stress-strain relationship. Therefore, to accurately predict the hysteretic behavior of steel structures such as circular steel columns under cyclic and dynamic loading, the difference of loading carrying capacity and deformation according to loading rate, assumed static and dynamic deformation state, must be investigated. In this study, numerical analyses of circular steel column using SM490 for change of loading rate and diameter-thickness ratio(D/t) were carried out by using three-dimensional elastic-plastic finite element analysis and dynamic cyclic plasticity model of SM490 developed by the authors. Characteristics of hysteretic behavior of circular steel column using SM490, load carrying capacity and energy dissipation ratio, were clarified by analysis results.

• Steel and Composite Structures
• /
• v.32 no.5
• /
• pp.595-610
• /
• 2019

This paper deals with the static and dynamic behavior of Functionally Graded Carbon Nanotubes (FG-CNT)-reinforced porous sandwich (PMPV) polymer plate. The model of nanocomposite plate is investigated within the first order shear deformation theory (FSDT). Two types of porous sandwich plates are supposed (sandwich with face sheets reinforced / homogeneous core and sandwich with homogeneous face sheets / reinforced core). Functionally graded Carbon Nanotubes (FG-CNT) and uniformly Carbon Nanotubes (UD-CNT) distributions of face sheets or core porous plates with uniaxially aligned single-walled carbon nanotubes are considered. The governing equations are derived by using Hamilton's principle. The solution for bending and vibration of such type's porous plates are obtained. The detailed mathematical derivations are provided and the solutions are compared to some cases in the literature. The effect of the several parameters of reinforced sandwich porous plates such as aspect ratios, volume fraction, types of reinforcement, number of modes and thickness of plate on the bending and vibration analyses are studied and discussed. On the question of porosity, this study found that there is a great influence of their variation on the static and vibration of porous sandwich plate.

• Journal of the Korean Society for Railway
• /
• v.8 no.4
• /
• pp.321-329
• /
• 2005

This paper has established the strength evaluation procedure of the bogie frame for the Korean tilting train that is being developed in KRRI, In order to establish the strength evaluation procedure, firstly, the loading conditions imposed on the tilting train were investigated. In addition, the static and fatigue strength of the bogie frame has been evaluated. In order to derive the dynamic loads according to the carbody tilting, the load redistribution effect by carbody tilting, the unbalanced lateral acceleration effect by high-speed curving and the tilting actuator force effect have been considered. Multi-body dynamic analyses have been carried out to evaluate the tilting load cases and the strength analysis has been performed by finite element analyses. From this study, the structural safety of the bogie frame could be ensured.

• Geomechanics and Engineering
• /
• v.20 no.4
• /
• pp.345-358
• /
• 2020

Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

• Journal of Advanced Research in Ocean Engineering
• /
• v.1 no.4
• /
• pp.252-267
• /
• 2015

Offshore structures might encounter several environmental and operating conditions during their lifetime of several decades. In order to predict the dynamic behavior of offshore structures, several simulation cases should be considered to deal with all the combinations of ocean environments and operating conditions. Because a sophisticated time-domain coupled dynamic analysis requires an extremely large amount of computational time to handle all the possible cases, an efficient preliminary process to prescreen the probability of severe environmental conditions can be helpful in downsizing the number of simulation cases and computational effort. In this study, a prescreening procedure to reduce the number of environmental conditions for dynamic analyses of offshore structures is proposed. For the efficiency of the procedure, frequency-domain theories were adopted to estimate the platform offset, using quasi-static analyses in line tension prediction. The results were validated by comparing with those of dynamic analysis coupled between platform and mooring lines, and reasonable agreement was observed. In addition, the characteristics of environmental conditions classified to be severe to the system were investigated through the application of the developed prescreening scheme to several actual environmental conditions.