• Computers and Concrete
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• 제20권4호
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• pp.369-380
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• 2017

The effects of the vertical component of a ground motion on the earthquake performances of semi-ductile high-rise R/C structures were investigated in the present study. Linear and non-linear time-history analyses were conducted on an existing in-service R/C building for the loading scenarios including and excluding the vertical component of the ground motion. The ratio of the vertical peak acceleration to the horizontal peak acceleration (V/H) of the ground motion was adopted as the main parameter of the study. Three different near-source earthquake records with varying V/H ratio were used in the analyses. The linear time-history analyses indicated that the incorporation of the vertical component of a ground motion into analyses greatly influences the vertical deflections of a structure and the overturning moments at its base. The lateral deflections, the angles of rotation and the base shear forces were influenced to a lesser extent. Considering the key indicators of vertical deflection and overturning moments determined from the linear time-history analysis, the non-linear analyses revealed that the changes in the forces and deformations of the structure with the inclusion of the vertical ground motion are resisted by the shear-walls. The performances and damage states of the beams were not affected by the vertical ground motion. The vertical ground motion component of earthquakes is markedly concluded to be considered for design and damage estimation of the vertical load-bearing elements of the shear-walls and columns.

• 대한치과보철학회지
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• 제31권3호
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• pp.303-316
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• 1993

The purpose of this study was to analysis the stress distribution induced by three unit PFM bridges and various cantilever bridges replacing maxillary latersal incisor. The simplified two-dimensional photoelastic models used for this study was contructed in the folio- wing way. CR/R ratio was designed to be 1 : 1, 1 : 1.25 and 1 : 1.5. The pontics of cantilever bridge supported by maxillary canines consisted of wrap-around type, rest-extension type, and simple type. 3-unit PFM bridge was constructed with traditional method. 1kg vertical static load was applied on the center of the incisal edge of the pontic. The stress pattern was examined and recorded by photography. The results obtained were as follows ; 1. The magnitude of stress on the abutment root apex area of a traditional 3-unit bridge was the lowest. 2. The model of cantilevered pontic with a rest showed the relatively well distributed stress around the abutment tooth. The model with simple pontic generated the greatest stress concentration in the supporting structure of the abutment tooth. 3. As the height of bone level reduced, the rotational and vertical force increased around the abutment tooth. 4. The stress concentration of the 3-unit bridges occured on the root apex and stress concentration of the cantilever briage occured on the root apex and cervix area, 5. In the case of the cantilever bridge, stress concentrated distally on the root apex area of the abutment tooth and additional stress was observed mesially on the upper part of the root. Especially in the case of the simple pontic, was phenomenon was more apparent than the others. 6. Force applied to cantilevered pontic was transmitted to the adjacent central incisor through the contact surface. Stress was markedly observed on the mesial cervix area in the case of simple pontic and on the root apex area in the case of wrap-around type and rest-extension type.

• 한국운동역학회지
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• 제15권3호
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• pp.1-7
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• 2005

Excessive pronation and impact force during running are related to various running injuries. To prevent these injuries, three type of running shoes are used, such as cushioning, stability, and motion control. Although there were may studies about the effect of midsole hardness on impact force, no study to investigate biomechanical effect of motion control running shoes. The purpose of this study was to determine biomechanical difference between cushioning and motion control shoes during treadmill running. Specifically, plantar and rearfoot motion, impact force and loading rate, and insole pressure distribution were quantified and compared. Twenty male healthy runners experienced at treadmill running participated in this study. When they ran on treadmill at 3.83 m/s. Kinematic data were collected using a Motion Analysis eight video camera system at 240 Hz. Impact force and pressure distribution data under the heel of right foot were collected with a Pedar pressure insole system with 26 sensors at 360 Hz. Mean value of ten consecutive steps was calculated for kinematics and kinetics. A dependent paired t-test was used to compare the running shoes effect (p=0.05). For most kinematics, motion control running shoes reduced the range of rearfoot motion compared to cushioning shoes. Runners wearing motion control shoe showed less eversion angle during standing less inversion angle at heel strike, and slower eversion velocity. For kinetics, cushioning shoes has the effect to reduce impact on foot obviously. Runners wearing cushioning shoes showed less impact force and loading rate, and less peak insole pressure. For both shoes, there was greater load on the medial part of heel compared to lateral part. For pressure distribution, runners with cushioning shoes showed lower, especially on the medial heel.

• 한국운동역학회지
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• 제26권4호
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• pp.413-420
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• 2016

Objective: The purpose of this study was to analyze and compare different kinds of outdoor walking shoes in terms of muscle fatigue and ground reaction force on walking, and to provide foundational data for developing and choosing outdoor walking shoes that fit the users. Method: The study subjects were 30 healthy men. The experiment was conducted by using outdoor walking shoes with different inner and outer harnesses of the midsole, and shapes of the outsole. For data collection, electromyography was used to measure the muscle fatigue of the anterior tibial muscle and gastrocnemii, which contribute to the dorsiflexion and plantarflexion of the ankle joint, and the biceps muscle of the thigh and lateral great muscles, which contribute to the flexion and extension of the knee joint. A GRF measurement device was used to measure the X, Y, and Z axes. Results: In the type A outdoor walking shoes, regarding the hardness of the midsole, the inner part was soft, while the outer part was hard. The vertical ground reaction force was the lowest, which means least impact while walking and light load to the knees and ankles. The type C outdoor walking shoes were intended to provide a good feel in wearing the shoes. The tibialis anterior, biceps femoris, and gastrocnemii indicate low fatigue, which means that during a long-distance walk, it will minimize the fatigue in the muscles of the lower limbs. Conclusion: To sum up the study results, the different types of outdoor walking shoes indicate their unique characteristics in the biomechanical comparison and analysis. However, the difference was not statistically significant. Thus, a systematic and constant follow-up research should be conducted to cope with expanding market for outdoor walking shoes. Lastly, this study is expected to present foundational data and directions for developing outdoor walking shoes.

• 한국강구조학회 논문집
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• 제18권2호
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• pp.137-146
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• 2006

본 연구에서는 단재하경로 구조로 인식되는 강합성 2-거더교에서 가로보의 제원 및 배치 간격에 따른 여유도 평가를 위한 해석적인 연구를 수행하였다. 이를 위해 수평브레이싱은 생략하고 수직브레이싱은 I-단면 가로보로 적용한 40+50+40m의 2차로 연속교를 대상으로 하였다. 본 교량에 대해 정상 상태 및 한 개 거더에 심각한 균열을 가정한 손상 상태로 구분하고 가로보의 제원과 배치 간격을 변수로 하여 재료 및 기하비선형 해석을 수행하였다. 해석으로부터 구해진 각 경우에 대한 내하력을 토대로 정상 상태 및 손상 상태 교량의 여유도를 평가하였다. 평가 결과, 정상 상태 및 손상 상태 모두 가로보의 제원과 배치 간격에 따른 여유도 차이는 거의 없었다.

• 한국강구조학회 논문집
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• 제25권2호
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• pp.209-222
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• 2013

800MPa급 강재와 100MPa급 콘크리트를 적용한 매입형 합성기둥에 대하여 편심압축실험을 수행하였다. 강재단면의 모멘트팔길이와 변형(응력)을 증가시켜 고강도강재의 성능활용을 극대화할 수 있도록, ㄱ형 강재단면을 네 모서리에 집중 배치한 후, 래티스철근, 링크철근, 띠판을 이용하여 일체화하였다. 이 경우 강재단면의 강력한 횡구속효과로 인해 심부콘크리트의 성능도 개선된다. 실험결과 ㄱ형 강재 매입형 기둥은 H형 강재 매입형 기둥에 비하여 최대강도와 유효휨강성이 1.4배 이상 증가하였다.

• 한국지진공학회논문집
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• 제19권4호
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• pp.195-205
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• 2015

Various non-seismic tie details are frequently used for one- and two-story small buildings because the seismic demand on their deformation capacities is not relatively significant. To evaluate the effects of the non-seismic tie details on the seismic performance of reinforced concrete columns, six square columns with a cross section of $400{\times}400mm$ and six rectangular columns with a cross section of $250{\times}640mm$ were tested. The anchorage details at both ends and spacing of tie hoops, along with the cross-sectional shape and the magnitude of axial load, were considered as the primary test parameters. Test results showed that square columns had higher stiffness and lower lateral deformation rather than rectangular columns. Both lap spliced tie and U-shaped tie provided comparable or improved seismic performance to $90^{\circ}$ hook tie in terms of maximum strength, ductility, and energy dissipation. The predicted curves with modeling parameters in ASCE41-13 were conservative for test results of lap spliced tie and U-shaped tie specimens since plastic behavior after flexural yielding could not be considered. For economical design, ASCE41-13 should be revised with various test results of tie details.

• 한국구조물진단유지관리공학회 논문집
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• 제14권1호
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• pp.133-140
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• 2010

와이어로프와 T형 강판을 이용한 비부착공법의 내진성능을 평가하기 위해 중심 축하중과 반복 횡하중을 받는 5개의 보강된 기둥과 무보강 기둥을 실험하였다. 주요 변수는 T형 강판의 정착방법과 피복 모르터의 유 무이다. 실험결과 T형 강판이 정착된 기둥의 하중분배로 인한 휨 내력 및 연성 증가를 확인할 수 있었다. 그러나 T형 강판이 정착되지 않은 기둥은 연성 증가에는 효과적이지만 T형 강판으로 하중이 분배되지 않았다. 피복 모르터가 있는 보강된 기둥은 효과적인 초기 강성 및 휨 내력 증가를 보였지만 연성증가에는 불리하였다. 단면분할법을 이용해 예측한 보강된 기둥의 최대 휨 내력은 등가응력블럭을 사용하여 예측한 ACI 318-05 기준보다 실험결과를 예측하였다.

• Advances in concrete construction
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• 제8권3호
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• pp.173-185
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• 2019

This article presents a comparative study of the effect of steel layouts on the seismic behavior of transition steel-concrete composite connections, both experimental and analytical investigations of concrete filled steel tube-reinforced concrete (CFST-RC) and steel reinforecd concrete-reinforced concrete (SRC-RC) structures were conducted. The steel-concrete composite connections were subjected to combined constant axial load and lateral cyclic displacements. Tests were carried out on four full-scale connections extracted from a real project engineering with different levels of axial force. The effect of steel layouts on the mechanical behavior of the transition connections was evaluated by failure modes, hysteretic behavior, backbone curves, displacement ductility, energy dissipation capacity and stiffness degradation. Test results showed that different steel layouts led to significantly different failure modes. For CFST-RC transition specimens, the circular cracks of the concrete at the RC column base was followed by steel yielding at the bottom of the CFST column. While uncoordinated deformation could be observed between SRC and RC columns in SRC-RC transition specimens, the crushing and peeling damage of unconfined concrete at the SRC column base was more serious. The existences of I-shape steel and steel tube avoided the pinching phenomenon on the hysteresis curve, which was different from the hysteresis curve of the general reinforced concrete column. The hysteresis loops were spindle-shaped, indicating excellent seismic performance for these transition composite connections. The average values of equivalent viscous damping coefficients of the four specimens are 0.123, 0.186 and 0.304 corresponding to the yielding point, peak point and ultimate point, respectively. Those values demonstrate that the transition steel-concrete composite connections have great energy dissipating capacity. Based on the experimental research, a high-fidelity ABAQUS model was established to further study the influence of concrete strength, steel grade and longitudinal reinforcement ratio on the mechanical behavior of transition composite connections.

• 한국철도학회논문집
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• 제10권5호
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• pp.619-625
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• 2007

본 논문은 인천국제공항철도에서 운행하고 있는 전동차의 동적특성시험을 수행한 결과이다. 인천국제공항철도의 직통형 전동차는 국내 처음으로 120km/h로 주행한 차량으로 탈선계수를 공차와 만차로 구분하여 측정하였다. 탈선계수측정결과 탈선에 대한 안전성을 판단할 때 가장 기본적인 지표로 사용하는 탈선계수는 공차 때가 만차 때보다 높게 나타났으며, 공차와 만차 모두 0.8 미만이었다. 속도에 따른 탈선계수는 80km/h를 전후한 속도 대역으로 운행하는 구간이 선로상태가 좋지 않은 구간으로서 탈선계수도 증가하는 것으로 나타났다. 횡압은 공차 때에는 2.1톤 미만이었으며, 만차 때에는 2.4톤 미만으로 발생하였다. 인천국제공항철도 전동차가 120km/h 주행에서도 안전함을 탈선계수 실측에 의해 확인하였다. 그러나 본 논문에서 적용된 평가방법의 경우 시험방법이 복잡하고, 측정장치 설치의 어려움이 있으며, 비용이 많이 드는 단점이 있었다. 따라서 측정이 간단한 방법으로 영업운전에서도 차량의 안전성을 확인할 수 있는 방안이 연구되어야 할 것이다.