• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.5
• /
• pp.569-576
• /
• 2019

PSC-Edge Rahmen Bridge makes low thickness and long span by introducing prestressed force to the edge girder and reducing positive moment. In the bridge, diagonal tension cracks occurred in the direction of $45^{\circ}$ to outer side of the girder after the temporary bent supported on the lower part of the upper slab and the secondary strand is tensioned on the girder. Researches on stress distribution and burst crack behavior of pre-stress anchorage has been conducted, it is difficult to analyze an obvious cause due to difference between actual shape and boundary condition. This study performed 3D frame analysis with additional boundary condition of temporary bent, the maximum compression stress occurred in the girder and there was a limit to identify the cause. It performed 3D Solid analysis with LUSAS 16.1 and the maximum principal tensile stress occurred at the boundary between the girder and the slab. As analyzing required reinforcement quantity at obtuse angle of the girder with the maximum principal tensile stress and directional cosine, reinforcement quantity was insufficient. Additional bridges have increased reinforcement quantity and extended area and crack was not occurred. It is expected that cracks on the girder during construction could be controlled by applying the proposed method to PSC-Edge Rahmen Bridge.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.34 no.4
• /
• pp.100-108
• /
• 2022

Three-dimensional FEM numerical analysis was performed to understand the behaviors of blocks and piles according to the horizontal load for the block breakwater combined with piles. The Modified Mohr-Coulomb model, the improved version of the Mohr-Coulomb model, was applied for the ground modeling. The cases when the pile is embedded only into the block, embedded to the riprap layer (H = 4.29 cm), and embedded to the ground down to 2H, 3H, and 4H were examined. The results of the laboratory model experiment and the numerical analysis showed similar horizontal resistance force-displacement behaviors. The pile showed rotational behavior up to the embedment depth of 1H~2H and bending behavior in the case of 3H~4H depth embedment. When the embedment depth of the pile is 3H or more, the pile shows a bending behavior, so it can be considered that the pile contributes significantly to the horizontal resistance of the block breakwater. The results of this study will be used for various numerical analyses for real-size structure design.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6D
• /
• pp.587-597
• /
• 2010

When a car accident occurs, people who had an accident are not free from civil and criminal issues so that the accident investigator should reenact and analyze the accident situation accurately. In addition, the obtained documents through the analysis of such car accident occurrence and related factors have to be used to carry out the improvement of the areas that has numerous car accidents and complementary actions. The vehicle speed, accelerating force, braking power are currently known as the most affecting factors in accordance with many car accidents, traffic facilities, road design, etc. The vehicle's performance and rode friction coefficient road surface friction coefficient are affecting the most closely in this field. Especially, once the estimate of the speed of the accident moment relating to main eleven articles of Traffic Accident Exemption Law is very important and accuracy is required. However, currently the researches of these matters have not made exclusively yet in Korea. In this study by reflecting this current situation, until the sudden braking history is found from the car's sudden braking, it estimates accurately the transient brake time and rode friction coefficient by measuring a time of transient brake time through the precision speed detector (Vericom VC2000PC). The analysis of the experimental results calculated the transient brake time and friction coefficient to fit into the purpose of this study in the basis of different kind of various special purpose asphalt pavement and slip-prevention pavement and provided the fundamental data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.6
• /
• pp.2411-2425
• /
• 2013

In the design of pile foundation on the rock layer in the stratified structure with sedimentary and rock layers, the structural analysis of the stratified rock layer is required to determine the failure modes (flexural failure, punching shear failure or end bearing failure) and the bearing capacity of the rock layer. However, the existing usable Elastic Plate Analysis Method (EPAM) suggested by ACI committee 436 and Korean Code Requirements for Structural Foundation Design is very complex, and engineers have many difficulties in using it. Therefore, in this research, we proposed the relatively simple Circular Foundation Analysis Method (CFAM) with the concept and the equation of the equivalent effective width (radius) instead of the complex EPM, and the related equations of bending moment and shear force to be equal to the analysis results of EPAM. As a result, the proposed CFAM using the equivalent effective width (radius) is simple and convenient to use, and the analysis results of it are very good in their accuracies comparing those of EPAM and Finite Element Method.

• Physical Therapy Korea
• /
• v.15 no.1
• /
• pp.38-45
• /
• 2008

This study investigated gait characteristics, kinematics, and kinetics in the lower extremities between two different shoe conditions (high heeled shoes (7 cm), and high heeled shoes with a total contact insert (TCI)) after lower extremity muscle fatigue. Although TCI shave been applied in high heeled shoes to increase comfort and to decrease foot pressure, no study has attempted to identify the effects of TCI in fatigue conditions. The purpose of this study was to determine the effects of walking in high heeled shoes with TCI after lower extremity muscle fatigue was induced. This study was carried out in a motion analysis laboratory at Hanseo University. A volunteer sample of 14 healthy female subjects participated. All in fatigue conditions, the subjects were divided into two groups. The muscle fatigue was induced by 40 voluntary dorsi- and plantar-flexion exercises and 40 heel-rise exercises of the dominant foot. Surface electromyography was used to confirm the localized muscle fatigue using power spectral analysis of three muscles (tibialis anterior, gastrocnemius medialis and lateralis). The results were as follows: (1) In muscle fatigue conditions, the use of TCI decreased the peak flexion angle of the hip joint significantly in the early stance phase (p<.05) and increased the peak hip flexion moment in the terminal stance phase (p<.05). (2) In muscle fatigue conditions, the application of TCI also increased peak hip power generation in the early stance phase and peak hip power absorption in the terminal stance phase (p<.05). (3) In muscle fatigue conditions, the use of TCI reduced the impact force significantly and increased the secondary peak vertical GRF. These findings suggest that the TCI may provide beneficial effects when muscle fatigue occurs for a high heeled shoe gait. Future research employing the patient population and various types of TCI materials are required to clarify the effects of TCI.

• Journal of the Ergonomics Society of Korea
• /
• v.35 no.6
• /
• pp.551-568
• /
• 2016

Objective: The objective of this study is to identify the difference in the press behavior characteristics of 3D Touch, which is a new touch interaction of smart phones, and the existing 'Tap and Long Press' touch interaction, and to examine behavior changes upon feedbacks. Background: Since 3D Touch is similar to the existing 'Tap and Long Press' touch interactions in terms of press behavior, which is likely to cause interference, it is necessary to conduct a preliminary study on behavior characteristics of touch interactions. Method: In utilization of smart phones with the 3D Touch function to measure press behavior characteristics of touch interaction, an experiment was conducted where 30 subjects were given a task to press 30 buttons of touch interactions on the screen. During the experiment, two press behavior characteristics-maximum touch pressure and press duration-were analyzed. To grasp changes in behaviors upon feedbacks, the task was carried out in a condition where there was no feedback and in a condition where there were feedbacks of specific critical values. Results: While there was no feedback given, subjects tended to press with much strength (318.98gf, 0.60sec) in the case of 3D Touch, and press the Long Press button for a while (157.12gf, 1.10sec) and press the Tap button with little strength only for a short moment (37.92gf, 0.10sec). 3D Touch and Long Press had an area of intersection in time, but when feedbacks of specific critical values were given, there were behavior calibration effects to adjust the press behavior characteristics of 3D Touch and Long Press. Conclusion: Although interferences are expected between 3D Touch and Long Press due to the similarity of press behaviors, feedbacks induce behavior calibration. Hence, once feedbacks were provided with 3D Touch operated in an appropriate condition of critical pressure, interference between two motions can be minimized. Application: The findings of this study are expected to be utilized as a basis for the values of optimal critical pressure, at which users can easily distinguish 3D Touch from Long Press which is the existing touch interaction.

• Composites Research
• /
• v.32 no.5
• /
• pp.284-289
• /
• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.12
• /
• pp.93-102
• /
• 2023

Despite recent modifications to building structural standards emphasizing the seismic stability of building foundations, the current design focus remains solely on vertical support, resulting in insufficient consideration of horizontal loads during earthquakes. In this study, we evaluated the dynamic behavior of inclined tripod micropiles (ITMP), which provide additional seismic resistance against horizontal and vertical loads during earthquakes. A comparison of the dynamic characteristics, such as acceleration, displacement, bending moment, and axial force, of ITMP with a 15° installation angle and normal vertical micropiles with a 0° installation angle was performed using dynamic centrifuge model tests. Results show that under moderate seismic loads, the proposed ITMP exhibited lower acceleration responses than the vertical micropiles. However, when subjected to a long-period strong seismic excitation, such as sine (2 Hz), ITMP showed greater responses than the vertical micropiles in terms of acceleration and settlement. These results indicate that the use of ITMP reduces the amplif ication of short-period (high-f requency) contents compared with the use of vertical micropiles. Therefore, ITMP can be used to enhance seismic performance of structures.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.5
• /
• pp.1915-1933
• /
• 2013

In this study, the virtual fixed point analysis and 3D fully modeling analysis for bent pile structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, the optimized column-pile length ratio is analyzed for supplementing virtual fixed point design and examining a more exact behavior of bent pile structures by taking into account the major influencing parameters such as pile length, column and pile diameter, reinforcement ratio and soil conditions. To obtain the detailed information, the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D fully modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D fully modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of bent pile structures. Therefore, it is necessary that 3D fully modeling analysis is considered for the exact design of bent pile structures. In this study, the emphasis is on quantifying an improved design method (optimized column-pile length ratio) of bent pile structures developed by considering the relation between the column-pile length ratio and allowable lateral deflection criteria. It can be effectively used to perform a more economical and improved design of bent pile structures.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.40 no.5
• /
• pp.527-534
• /
• 2020

A significant factor in construction work is cost. At early- and advanced-stage design, costs should be calculated to derive realistic cost estimates according to unit price calculation. Based on these estimates, the economic feasibility of construction work is assessed, and whether to proceed is determined. Through the Korea Institute of Civil Engineering and Building Technology, the construction cost index has been calculated by indirect methods after both the producer price index and construction market labor have been reprocessed to easily adjust the price changes of construction costs in Korea, and the Institute has announced it since 2004. As of January 2000, however, the construction cost index was released, and this has a time constraint on the correction and use of past construction cost data to the present moment. Variables were calculated to compute a rough construction cost that utilized past construction costs through surveys of the producer price index and the construction market labor force consisting of the construction cost index. After significant independent variables among the many variables were selected through correlation analysis, the construction cost index from 1970 to 1999 was calculated and presented through multiple regression analysis. This study therefore has prominent significance in terms of proposing a method of calculating rough construction costs that utilize construction costs that pre-date the 2000s.