• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.12
• /
• pp.2291-2299
• /
• 2008

Hall effect force sensors have been used to measure clamping force in conventional Electric Parking Brake(EPB) systems. Estimation of clamping force without the sensors has drawn attentions due to mounting space limitations and cost issues. Removing the sensor requires the estimation of the initial contact point where the clamping force is effectively applied to the brake pads. In this paper, we propose how to estimate the initial contact point finding the relation between the angular velocity of an actuator and the initial contact point. For force estimation a look-up table is used as a function of the displacement of parking cable from the initial contact point. The proposed method is validated by experiments. From the experimental results we observe that the proposed method satisfies the specifications. The designed method is also able to estimate clamping force although parking cables are loosened and brake pads are worn out. Applying the proposed method enables manufacturing of low cost EPB systems.

• Structural Engineering and Mechanics
• /
• v.41 no.1
• /
• pp.43-65
• /
• 2012

The primary objective of this study was to identify concrete contribution to the initial shear strength of reinforced concrete (RC) hollow columns under lateral loading. Seven large-scale RC rectangular hollow column specimens were tested under monotonic or cyclic lateral loads. The most important design parameter was column length-to-depth aspect ratio ranging between 1.5 and 3.0, and the other test variables included web area ratio, hollow section ratio, and loading history. The tests showed that the initial shear strength reduced in a linear pattern as the column aspect ratio increased, and one specimen tested under cyclic loading achieved approximately 83% of the shear strength of the companion specimen under monotonic loading. Also, several pioneering shear models proposed around the world, all of which were mainly based on tests for columns with solid sections, were reviewed and compared with the test results of this study, for their possible applications to columns with hollow sections. After all, an empirical equation was proposed for concrete contribution to the initial shear strength of RC hollow columns based on fundamental mechanics and the test results.

• Korean Journal of Materials Research
• /
• v.32 no.7
• /
• pp.313-319
• /
• 2022

Double-layer capacitors (DLCs) are developed with high surface electrodes to achieve a high capacitance value. In the present work, the initial bulk concentration of 1 mol/m³ and 3 mol /m³ are selected to show the consequential effects on the performance of a double-layer capacitor. A 1D model of COMSOL Multiphysics has been developed to analyze the electric field and potential in cell voltage, the electric displacement field and polarization induced by the field, and energy density in a double-layer structure. The electrostatics and the electric circuit modes in COMSOL are used to simulate the electrochemical processes in the double-layer structure. The analytical analysis of a double-layer capacitor with different initial bulk concentrations is investigated by using Poisson-Nernst-Plank equations. From the simulation results, the differential capacitance changes as a function of compact layer thickness and initial bulk concentration. The energy density varies with the differential capacitance and voltage window. The values of energy density are dominated by the interaction of ions in the solution and electrode surface.

• Journal of Sensor Science and Technology
• /
• v.23 no.1
• /
• pp.46-50
• /
• 2014

In this paper, we report a novel algorithm based on phase displacement, which supplements conventional TOF methods for distance measurement using an ultrasonic wave. The proposed algorithm roughly measures the distance between the transmission part and the receiving part by using the initial TOF. Thereafter, the precise distance is determined by measuring the phase displacement value between the synchronizing transmission signal and the signal obtained at the receiving end. A distance measurement experiment using a micrometer was performed to verify the accuracy of the ultrasonic wave sensor system. We found that the mean errors from the one adopting the distance measurement algorithm based on phase displacement varied from a minimum of 0.03 mm to a maximum of 0.09 mm. In addition, the standard deviation varied from a minimum of 0.04 mm to a maximum of 0.07 mm, thus giving a precision of ${\pm}0.1$ mm.

• Structural Engineering and Mechanics
• /
• v.71 no.4
• /
• pp.445-458
• /
• 2019

This study mainly aims to assess the performance of soil-structure systems designed by direct displacement-based method coupled with strong column-weak beam design concept through various system identification techniques under strong ground motions. To this end, various system identification methods are employed to evaluate the dynamic characteristics of a structure (i.e., modal frequency, system damping, mode shapes, and plastic hinge formation pattern) under a strong seismic excitation considering soil-structure interaction for different site conditions as specified by ASCE 7-10. The scope of the study narrowed down to the code-complying low- to high-rise steel moment resisting frames with various heights (4, 8, 12, 16-story). The comparison of the result of soil-structure systems with fix-based support condition indicates that the modal frequencies of these systems are highly influenced by the structure heights, specifically for the softer soils. This trend is more significant for higher modes of the system which can considerably dominate the response of structures in which the higher modes have more contribution in dynamic response. Amongst all studied modes of the vibration, the damping ratio estimated for the first mode is relatively the closet to the initial assumed damping ratios. Moreover, it was found that fewer plastic hinges are developed in the structure of soil-structure systems with a softer soil which contradicts the general expectation of higher damageability of such structural systems.

• Wind and Structures
• /
• v.36 no.2
• /
• pp.133-147
• /
• 2023

The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

• Geomechanics and Engineering
• /
• v.32 no.3
• /
• pp.335-346
• /
• 2023

For structures with underground basement walls, the soil-structure-interaction between the side soil and the walls affects the response of the system. There is interest in quantifying the relationship between the lateral earth pressure and the wall displacement using p-y curves. To date, passive p-y curves in available limited studies were assumed elastic-perfectly plastic. In reality, the relationship between earth pressure and wall displacement is complex. This paper focuses on studying the development of passive p-y curves behind rigid walls supporting granular soils. The study aims at identifying the different components of the passive p-y relationship and proposing a rigorous non-linear p-y model in place of simplified elastic-plastic models. The results of the study show that (1) the p-y relationship that models the stress-displacement response behind a rigid basement wall is highly non-linear, (2) passive p-y curves are affected by the height of the wall, relative density, and depth below the ground surface, and (3) passive p-y curves can be expressed using a truncated hyperbolic model that is defined by a limit state passive pressure that is determined using available logarithmic spiral methods and an initial slope that is expressed using a depth-dependent soil stiffness model.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.27 no.6
• /
• pp.237-244
• /
• 2023

This study analyzes the seismic response of traffic light poles, considering soil-foundation effects through nonlinear static and time history analyses. Two poles are investigated, uni-directional and bi-directional, each with 9 m mast arms. Finite element models incorporate the poles, soil, and concrete foundations for analysis. Results show that the initial stiffness of the traffic light poles decreases by approximately 38% due to soil effects, and the drift ratio at which their nonlinear behavior occurs is 77% of scenarios without considering soil effects. The maximum acceleration response increases by about 82% for uni-directional poles and 73% for bi-directional poles, while displacement response increases by approximately 10% for uni-directional and 16% for bi-directional poles when considering soil-foundation effects. Additionally, increasing ground motion intensity reduces soil restraints, making significant rotational displacement the dominant response mechanism over flexural displacement for the traffic light poles. These findings underscore the importance of considering soil-foundation interactions in analyzing the seismic behavior of traffic light poles and provide valuable insights to enhance their seismic resilience and safety.

• Journal of KSNVE
• /
• v.7 no.1
• /
• pp.81-89
• /
• 1997

The structural stress and vibration analysis of the rotary screen are investigated. The mechanical properties of the rotary screen, this is, Young's modulus and density of nickel alloy are determined experimentally. The natural vibration characteristics of the rotary screen are evaluated and the displacement, the stress of the rotary screen under the various load conditions are also examined. The radial displacement of the rotary screen is obtained by experiment under various rotating speeds.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1994.04a
• /
• pp.394-398
• /
• 1994

The aim of the present study was to determine the influence of vibration frequency and muscle contraction level at constant vibration displacement amplitudes on a commonly observed motor response elicited by local vibratory stimulation, i.e., the Tonic Vibration Reflex (TVR). Vibration was applied to the distal tendons of the hand flexor muscles. Changes in activity of the hand flexor and extensor muscles were analyzed as a function of the vibration frequency (40-200 Hz), displacement amplitude(200.mu.m and 300.mu.m peak-to-peak), and the initial contraction level of the flexor muscles (0%, 10%, and 20% of the maximal voluntary contraction: MVC). The main results indicate that the TVR increases with vibration frequency up to 100-150 Hz and decreases beyond, and the TVR attains its maximum at 10% MVC. It appears that high frequency vibration tends to induce less muscle/tendon stress. Such a result is of particular importance for the design of handheld vibrating tools.