• 한국강구조학회 논문집
• /
• 제21권6호
• /
• pp.619-626
• /
• 2009

저층 장스팬 철골프레임에는 강재절감을 위해 휨모멘트 저항에 극대화한 판폭 두께비가 큰 단면 부재를 사용하고 있다. 한편, 외부환경에 노출된 강부재는 수년간을 걸쳐 부식이 진행된다. 부식에 의한 단면결손에 따른 내력감소는 판폭두께비가 큰 부재의 경우가 판폭두께비가 작은 부재에 비하여 상대적으로 크다. 또한, 부식에 의한 압축측 플랜지 및 웨브 판두께의 감소(판폭두께비 증가)에 의한 한계상태 영역이 변경될 여지도 있다. 본 논문에서, 국내 장스팬 철골프레임을 대상으로 판폭두께비가 큰 단면에 대해서 부식진행정도에 따른 모멘트-회전각관계, 초기강성, 최대내력, 최대내력이후 강성 및 에너지흡수능력에 대해서 평가를 행하였다.

• 한국의류학회지
• /
• 제28권6호
• /
• pp.795-806
• /
• 2004

Unripe indigenous persimmons which contain rich tannins have been used as natural dye materials traditionally and have been using continuously for dyed clothes named Gal-ot in Jeju. Those persimmons were cheap and easy to use as dyes because of inedible and widely cultured in Korea. Persimmon juice dyes not only make fabrics brown-color but also give functional and hygienic properities such as stiffness, air ventilation of clothes, antibacterial activity, protectivity against ultraviolet light. However there are several serious problems which are ristriction of dyeing periods, longtime irradiation, uneven color and low color fastness etc. in persimmon juice dyeing. This study purpose to improve dye effect and method in order to enlarge useability of persimmon juice dyeing. Cotton fabrics were pad-dyed to 100% pick-up using padding machine after dipping in persimmon juice extracted from unripe persimmons indigenous from Jeju. It was possible and available to control pick-up rate. The color of dyed cotton fabrics by padding method was more even and repeatable than which by traditional hand method. Persimmon juice concentrations were 4 types of 10, 25, 50 and 100％. The more concentration increased, the more color deepened. UV Irradiation instead of sunlight was applied to color developing. Irradiation times were shortened till 1∼8 hrs. Same color values could be taken without water wetting which were required in sunlight irradiation. Tensile strengths of cotton fabrics pad-dyed with low concentration of persimmon juice decreased but recovered at high concentrations. Elongations(％) of cotton fabrics pad-dyed with persimmon juice were increased 1％ more than undyed cotton in sunlight irradiation. Drape stiffness increased upto double times as much as.

• International Journal of Human Ecology
• /
• 제16권2호
• /
• pp.1-9
• /
• 2015

This study investigated the effects of persimmon-dyed clothing materials upon thermophysiological responses and subjective comfort sensations during exercise and rest in a warm environment. Six healthy, untrained women participated in two separate testing sessions, with cotton materials dyed with astringent persimmon extract (DC) and undyed cotton materials (UDC). The physical characteristics associated with heat and moisture transfer were improved in DC; also, stiffness, anti-drapery stiffness and crispness in the primary hand values were higher in DC. The experimental protocol consisted of a 10-min rest, 15-min exercise on a treadmill (at ${7km{\cdot}h^{-1}}$) and 25-min recovery at $28{\pm}0.2^{\circ}C$ and $50{\pm}3%\;RH$. The results were as follows: When wearing DC rather than UDC, mean body temperature, heart rate, heat storage and body mass loss were significantly lower during the whole experimental period. Clothing microclimate temperature showed different profiles between the two clothing materials, being lower with DC than UDC during the first half of exercise and the second half of recovery. Clothing microclimate humidity was significantly lower with DC than UDC during the whole experimental period. When wearing UDC, subjects felt significantly warmer and less comfortable during exercise, and sensed greater humidity during exercise and recovery. These results suggest that eco-friendly clothing materials dyed with astringent persimmon extract can reduce exercise-induced heat load and improve subjective sensations when exercising and resting in a warm environment, due to greater heat dissipation from the body to the outside environment compared with undyed clothing materials.

• Earthquakes and Structures
• /
• 제20권4호
• /
• pp.431-444
• /
• 2021

T-shaped column is usually used as side column in buildings, which is one of the weak members in structural system. This paper presented a quasi-static cyclic loading experiment of six specimens of reinforced concrete (RC) T-shaped columns under compression-flexure-shear-torsion combined loadings to investigate the effect in the ratio of torsion to moment (T/M) and axial compression ratio (n) and height-thickness ratio of flange plate (φ) on their seismic performance. Based on the test results, the failure characteristics, hysteretic curves, ductility, energy dissipation, stiffness degradation and strength degradation were analyzed. The results show that the failure characteristics of RC T-shaped columns mainly depend on the ratio of torsion to moment, which can be divided into bending failure, bending-torsion failure and shear-torsion failure. With the increase of T/M ratio, the torsion ductility coefficient increased, and in a suitable range, the torsion and horizontal displacement ductility coefficient of RC T-shaped columns could be effectively improved with the increase of axial compression ratio and the decrease of height-thickness ratio of flange plate. Besides, the energy dissipation capacity of the specimens mainly depended on the bending and shear energy dissipation capacity. On the other hand, the increase of axial compression ratio and the ratio of torsion to moment could accelerate the torsional and bending stiffness degradation of RC T-shaped columns. Moreover, the degradation coefficient of torsion strength was between 0.80 and 0.98, and that of bending strength was between 0.75 and 1.00.

• Smart Structures and Systems
• /
• 제23권6호
• /
• pp.589-613
• /
• 2019

Cables are prone to vibration due to their low inherent damping characteristics. Recently, negative stiffness dampers have gained attentions, because of their promising energy dissipation ability. The viscous inertial mass damper (termed as VIMD hereinafter) can be viewed as one realization of the inerter. It is formed by paralleling an inertial mass part with a common energy dissipation element (e.g., viscous element) and able to provide pseudo-negative stiffness properties to flexible systems such as cables. A previous study examined the potential of IMD to enhance the damping of stay cables. Because there are already models for common energy dissipation elements, the key to establish a general model for IMD is to propose an analytical model of the rotary mass component. In this paper, the characteristics of the rotary mass and the proposed analytical model have been evaluated by the numerical and experimental tests. First, a series of harmonic tests are conducted to show the performance and properties of the IMD only having the rotary mass. Then, the mechanism of nonlinearities is analyzed, and an analytical model is introduced and validated by comparing with the experimental data. Finally, a real-time hybrid simulation test is conducted with a physical IMD specimen and cable numerical substructure under distributed sinusoidal excitation. The results show that the chosen model of the rotary mass part can provide better estimation on the damper's performance, and it is better to use it to form a general analytical model of IMD. On the other hand, the simplified damper model is accurate for the preliminary simulation of the cable responses.

• 한국산학기술학회논문지
• /
• 제20권4호
• /
• pp.1-8
• /
• 2019

우리나라는 고령화 사회로 급속하게 진입함에 따라 휠체어 사용 교통약자는 지속적으로 증가하고 있다. 그러나, 휠체어를 사용하는 교통약자가 고속버스를 이용하는 것은 거의 불가능하다. 따라서, 휠체어 사용자의 이동권 확보를 위한 고속버스의 개발이 필요하다. 이러한 휠체어 사용자를 위한 버스는 측면부에 휠체어 승객이 자유롭게 이동할 수 있는 전용 출입구, 휠체어 승객을 차실로 안전하게 이동시킬 수 있는 리프트 및 공간 활용성을 고려하여 휠체어 사용자가 탑승하지 않는 경우 일반 좌석으로 사용할 수 있는 가변 좌석의 개발이 필수적이다. 고속버스용 휠체어 전용 출입구의 개발은 기존 고속버스 차량에 대한 설계 변경, 개조 및 프레임 보강을 필요로 한다. 본 연구에서는 휠체어 사용자를 위한 승강구 시스템 개조부 설계와 유한 요소 모델을 이용한 구조 건전성을 평가하였다. 구조 해석을 통해 비틀림 강성 및 고유 모드 해석이 수행되었으며, 개조부 프레임에 대한 민감도 평가를 수행하고 개조부에 대한 최적화를 통해 경량화를 수행하였다. 휠체어 출입구 개조부에 대한 본 연구결과는 차량 개조 및 복지산업에 활용될 수 있을 것으로 기대된다.

• Ocean Systems Engineering
• /
• 제10권4호
• /
• pp.399-414
• /
• 2020

A floating bridge is an innovative solution for deep-water and long-distance crossing. This paper presents a curved floating bridge's dynamic behaviors under the wind, wave, and current loads. Since the present curved bridge need not have mooring lines, its deep-water application can be more straightforward than conventional straight floating bridges with mooring lines. We solve the coupled interaction among the bridge girders, pontoons, and columns in the time-domain and to consider various load combinations to evaluate each force's contribution to overall dynamic responses. Discrete pontoons are uniformly spaced, and the pontoon's hydrodynamic coefficients and excitation forces are computed in the frequency domain by using the potential-theory-based 3D diffraction/radiation program. In the successive time-domain simulation, the Cummins equation is used for solving the pontoon's dynamics, and the bridge girders and columns are modeled by the beam theory and finite element formulation. Then, all the components are fully coupled to solve the fully-coupled equation of motion. Subsequently, the wet natural frequencies for various bending modes are identified. Then, the time histories and spectra of the girder's dynamic responses are presented and systematically analyzed. The second-order difference-frequency wave force and slowly-varying wind force may significantly affect the girder's lateral responses through resonance if the bridge's lateral bending stiffness is not sufficient. On the other hand, the first-order wave-frequency forces play a crucial role in the vertical responses.

• Clinics in Shoulder and Elbow
• /
• 제23권4호
• /
• pp.183-189
• /
• 2020

Background: The purpose of the current study was to investigate short- to mid-term outcomes and complications following radial head replacement (RHR) for complex radial head fractures and to identify factors associated with clinical outcomes. Methods: Twenty-four patients with complex radial head fractures were treated by RHR. The mean age of the patients was 49.8 years (range, 19-73 years). Clinical and radiographic outcomes were evaluated for a mean follow-up period of 58.9 months (range, 27-163 months) using the visual analog scale (VAS) score for pain, the Mayo elbow performance score (MEPS), the quick disabilities of the arm, shoulder and hand (Quick-DASH) score, and serial plain radiographs. Complications were also evaluated. Results: At the final follow-up, the mean VAS score, MEPS, and Quick-DASH score were 0.6±1.1, 88.7±11.5, and 19.4±7.8, respectively. The mean range of motion was 132.7° of flexion, 4.7° of extension, 76.2° of pronation, and 77.5° of supination. Periprosthetic lucency was observed in six patients (25%). Heterotopic ossification was observed in four patients (16.7%). Arthritic change of the elbow joint developed in seven patients (29.2%). Capitellar wear was found in five patients (20.8%). Arthritic change of the elbow joint was significantly correlated with MEPS (P=0.047). Four cases of complications (16.6%) were observed, including two cases of major complications (one stiffness with heterotopic ossification and progressive ulnar neuropathy and one stiffness) and two cases of minor complications (two transient ulnar neuropathy). Conclusions: RHR for the treatment of complex radial head fractures yielded satisfactory short- to mid-term clinical outcomes, though radiographic complications were relatively high.

• PNF and Movement
• /
• 제22권1호
• /
• pp.113-128
• /
• 2024

Purpose: This study aimed to investigate the effects of eccentric training applied to the calf muscles on muscle tone, muscle strength, and gait variables in patients with chronic stroke. Methods: Twenty-two participants were divided into experimental (n=12; eccentric training) and control (n=10; static stretching and stretching board) groups. The participants completed 30-minute physical therapy sessions five times a week for three weeks. Calf muscle tone, muscle strength, and gait variables were measured using MyotonPRO, a hand-held dynamometer, and Optogait, respectively, before and after each intervention. Results: Two-way analysis of variance (ANOVA) indicated a significant interaction effect between measurement points and groups in frequency, stiffness, and decrement of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles (p<.05). Paired t-tests showed that the experimental group exhibited significantly decreased frequency and stiffness scores for the lateral gastrocnemius, medial gastrocnemius, and soleus muscles (p<.05), as well as significantly increased decrement and muscle strength scores, gait speed, step length, and stride length (p<.05). Conclusion: The application of eccentric training to the calf effectively reduced muscle tone, increased muscle strength, and improved the gait speed, step length, and stride length of patients with chronic stroke.

• Geomechanics and Engineering
• /
• 제36권6호
• /
• pp.527-543
• /
• 2024

In the implementation of most civil structures, especially underground, deep excavations with a vertical slope are required. Using flexible retaining walls is applied as one of the ways to stabilize vertical holes. Therefore, it is necessary to know the parameters affecting the performance of such walls in reducing their horizontal movement. In this research, by building a suitable laboratory model, the parameters of the amount of flexibility, the embedment depth of the wall, the type and number of tieback in the wall were investigated for 42 static laboratory models. The purpose of this research is to study the flexible retaining wall with helical tieback compared to simple tieback at different heights, which shows the best performance in terms of reducing horizontal displacement in proportion to increasing or decreasing flexibility. On the other hand, one of the parameters affecting the flexibility of the wall, which is its bending stiffness, was extracted by numerical software outputs and studied on the results such as relative flexibility, stiffness, safety and numerical stability of the wall.The results of this study show that among the parameters, in the first place, the effect of the type of tieback is inhibited and in the second place, the ratio of thickness to wall height is known as the most important parameter. the best performance for walls with the helical tiebacks in reducing their horizontal displacement can be economically, flexibly and stability assigned to a wall that tiebacks is in the range of H2/t to H4/t and its flexibility ratio is 2/3.