• Structural Engineering and Mechanics
• /
• v.38 no.2
• /
• pp.231-247
• /
• 2011

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.

• Journal of the Korean Society of Safety
• /
• v.21 no.6 s.78
• /
• pp.74-81
• /
• 2006

Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of a Arch Bridge. Component reliabilities of girders have been evaluated using the response surfaces of the design variables at the selected critical sections based on the maximum shear and negative moment locations. Response Surface Method(RSM) is successfully applied for reliability analyses for this relatively small probability of failure of the complex structure, which is hard to be obtained by Monte-Carlo Simulations or by First Order Second Moment Method that can not easily calculate the derivative terms of implicit limit state functions. For the analysis of system reliability, parallel resistance system composed of girders is changed into parallel series connection system. The upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts compared with the previous permutation method or system reliability analysis method.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.295-300
• /
• 2007

Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of a Arch Bridge. Component reliabilities of girders have been evaluated using the response surfaces of the design variables at the selected critical sections based on the maximum shear and negative moment locations. Response Surface Method (RSM) is successfully applied for reliability analyses for this relatively small probability of failure of the complex structure, which is hard to be obtained by Monte-Carlo Simulations or by First Order Second Moment Method that can not easily calculate the derivative terms of implicit limit state functions. For the analysis of system reliability, parallel resistance system composed of girders is changed into parallel series connection system. The upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significant]y reduced time and efforts compared with the previous permutation method or system reliability analysis method.

• Journal of the Korean GEO-environmental Society
• /
• v.2 no.4
• /
• pp.15-27
• /
• 2001

This paper proposes the force equations(thrust, moment) of corrugated steel culverts through the finite element method. The conditions for maximum thrust and maximum moment are determined from the analysis of soil-structure interaction during the three construction stages, such as backfill to the crown, backfill to the soil cover, and live loads. The proposed form of thrust and moment equations are deduced from the analysis of behaviour and the application of Castigliano's second theorem for the semi-arch structure. Finally, the coefficients used in the proposed equations are determined from a large number of analysis for the various geometries and the soil-structure relative stiffness under the conditions of maximum thrust and maximum moment.

• Korean Journal of Applied Biomechanics
• /
• v.34 no.2
• /
• pp.45-52
• /
• 2024

Objective: The purpose of this study was to measure the morphological characteristics of the foot and biomechanical variables of the lower extremity joints during vertical jump and investigate the relationship between foot morphology and biomechanics of vertical jump. Method: 24 men in their 20s (age: 22.42 ± 1.41 yrs, height: 173.37 ± 4.61 cm, weight: 72.02 ± 6.21 kg, foot length: 251.70 ± 8.68 mm) participated in the study. Morphological characteristics of the foot included the length of the first toe, the length of the second toe, and the horizontal length from the center of ankle joint to the achilles tendon (Plantar Flexion Moment Arm [PFMA]). Biomechanical variables were measured for plantar flexor strength of the ankle joint and peak angular velocity, moment, and power of the lower extremity joint during vertical jump. Results: There was a significant correlation between the length of the first toe and plantar flexion strength at 30°/s [r=.440, p=.016], the angular velocity of the metatarsophalangeal [MTP] joint [r=-.369, p=.038] while significant correlations between PFMA and the angular velocities of the knee joint [r=.369, p=.038] and ankle joint [r=.420, p=.021] were found. There were also significant correlations between the length of the first toe and the maximum moment of the hip joint [r=.379, p=.034], and the length of the second toe and the power of the hip joint [r=-.391, p=.029]. Finally, significant correlations between PFMA and the power of the ankle joint [r=.424, p=.019] and MTP joint [r=.367, p=.039] were found. Conclusion: Based on the results of this study, the length of the toe and PFMA would be related to the function of the lower extremity joint. Therefore, this should be considered when designing the functional structure of a shoe. Furthermore, this relationship can be applied to intensive training for the plantar flexors and toe flexors to improve power in athletic performance.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.1 s.173
• /
• pp.215-224
• /
• 2000

In order to reduce the variation effects of uncertainties in the engineering environments, new robust optimization method, which considers the uncertainties in design process, is proposed. Both design variables and system parameters are considered as random variables about their nominal values. To ensure the robustness of performance function, a new objective is set to minimize the variance of that function. Constraint variations are handled by introducing probability constraints. Probability constraints are solved by the advanced first order second moment (AFOSM) method based on the reliability theory. The proposed robust optimization method has an advantage that the second derivatives of the constraints are not required. The suggested method is examined by solving three examples and the results are compared with those for deterministic case and those available in literature.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.12
• /
• pp.856-865
• /
• 2015

In a high-speed press, numerous moving links are interconnected and each link executes a constrained motion at high speed. As a consequence, high-level dynamic unbalance force and unbalance moment are transmitted to the main frame of the press, which results in unwanted vibration and significantly degrades manufacturing accuracy. Dynamic unbalance force and unbalance moment inevitably transmits high-level vibrational force to the foundation on which the press is installed. Minimizing the vibrational force transmitted to the foundation is critical for the protection of both the operators and the surrounding structures. The whole task should be carried out in two steps. The first step is to reduce dynamic unbalance based upon kinematic and dynamic analyses. The second step is to design and build an optimal vibration isolation system minimizing the vibrational force transmitted to the foundation. Firstly, the dynamic design method is presented to reduce dynamic unbalance force and moment. For this a 3D CAD software was utilized and a computer program was written to compute dynamic unbalance force and moment. Secondly, the design method for vibration isolation system is presented. The method for designing coil springs and viscous dampers are explained in detail.

• Journal of the Korean Statistical Society
• /
• v.24 no.1
• /
• pp.183-195
• /
• 1995

For a distribution on the unit sphere, the set of eigenvectors of the second moment matrix is a conventional measure of orientation. Asymptotic confidence cones for eigenvector under the parametric assumptions for the underlying distributions and nonparametric confidence cones for eigenvector based on bootstrapping were proposed. In this paper, to reduce the level error of confidence cones for eigenvector, double bootstrap confidence cones based on prepivoting are considered, and the consistency of this method is discussed. We compare the perfomances of double bootstrap method with the others by Monte Carlo simulations.

• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.1
• /
• pp.45-55
• /
• 2013

With the recent advancement of control method and battery technology, the electric vehicle have been researched to replace the conventional vehicle with electric vehicle with the view point of the environmental concerns and energy conservation. An electric vehicle which is equipped with the independent front steering system and in-wheel motors has advantage in terms of control. For example, the different torque which generated by left and right wheels directly can make yaw moment and the independent steering using outer wheel control is able to reduce the sideslip angle. Using of independent steering and driving system, the 4 wheel electric vehicle can improve a performance better than conventional vehicle. In this paper, we consider the method for improving the cornering performance of independent front steering system and in-wheel motor used electric vehicle with the compensated outer wheel angle and direct yaw moment control. Simulation results show that the method can improve the cornering performance of 4 wheel electric vehicle. We also apply the steering motor failure to steer the vehicle turned by the torque difference without steering. This paper describes an independent front steering and driving, consist of three parts; Vehicle Model, Control Algorithm for independent steering and driving and simulation. First, vehicle model is application of TruckSim software for independent front steering and 4 wheel driving. Second, control algorithm describes the reduced sideslip and direct yaw moment method in view of cornering performance. Last is simulation and verification.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.4 no.6
• /
• pp.1253-1272
• /
• 2010

In this paper, we propose a new affine shape adaptation scheme for the affine invariant feature detector, in which the convergence stability is still an opening problem. This paper examines the relation between the integration scale matrix of next iteration and the current second moment matrix and finds that the convergence stability of the method can be improved by adjusting the relation between the two matrices instead of keeping them always proportional as proposed by previous methods. By estimating and updating the shape of the integration kernel and differentiation kernel in each iteration based on the anisotropy of the current second moment matrix, we propose a coarse-to-fine affine shape adaptation scheme which is able to adjust the pace of convergence and enable the process to converge smoothly. The feature matching experiments demonstrate that the proposed approach obtains an improvement in convergence ratio and repeatability compared with the current schemes with relatively fixed integration kernel.