• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.141-153
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• 1987

The prediction of the exact behavior of multistory building is one of the most complicated problem encountered in structural engineering practice. An efficient computer method for the three dimensional analysis of building structures is presented in this paper. A multistory building is idealized as an assemblage of a series of rectangular plane frames interconnected by rigid floor diaphragms. The matrix condensation technique is employed for the reduction of degrees of freedom, which results in a significant saving in computational efforts and the required memory size. Kinematical approach was used to assemble condensed stiffness matrices of plane frames into a three dimensional stick model stiffness matrix. The static analysis follows the modified tridiagonal approach. Since this procedure utilizes the condensed stiffness matrix of the structure, the dynamic equations of motion for the story displacement are developed by assigning proper mass for each story. Analysis results of several example structures are compared to those obtained by using the well-known SAP IV for verification of the accuracy and efficiency of the computer program PFS which was developed utilizing the method proposed in this study. The analysis method proposed in this study can be used as an efficient and economical means for the analysis of multistory buildings.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.69-74
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• 2005

In order to evaluate the safety of navigation at sea and the safety of mooring on berthing, it is necessary that the wave and wind induced ship dynamic motion should be measured in real time domain for the validity of theoretical evaluation method sum as sea-keeping performance and safety of mooring. In this paper, the basic design of sensors is discussed and some system configurations were shown. The developed system mainly consists of 4 kind of sensors sum as three dimensional accelerator, two dimensional tilt sensor, two displacement sensors and azimuth sensor. Using this measuring system(MMS), it can be obtained the 6 degrees of freedom of ship dynamic motions at sea and on berthing sum as rolling, pitching, yawing, swaying, heaving, surging under the certain external forces.

• Journal of the Korea Convergence Society
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• v.11 no.5
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• pp.175-182
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• 2020

The calculation of the optimal trajectory of the stepped top-down robot was made using a genetic algorithm and a computational torque controller. First, the total energy efficiency was minimized using the Red-Cold Generic Algorithm (RCGA) consisting of reproductive, cross, and mutation. The reproducibility condition related to the position assembly of the start and end of the stride and the joints, angles, and angular velocities are linear constraints. Next, the unequal constraint accompanies the condition for preventing the collision of the swing leg at the corner with the outer surface of the stairs, the condition of the knee joint for preventing kinematic peculiarity, and the condition of no moment in safety in the traveling direction. Finally, the angular trajectory of each joint is defined by fourth-order polynomial whose coefficient is to approximate chromosomes. This is to approximate walking. In this study, the energy efficiency of the optimal trajectory was analyzed by computer simulation through a biped robot with seven degrees of freedom composed of seven links.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.847-852
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• 2005

In order to evaluate the safety of navigation at sea and the safety of mooring on berthing, it is necessary that the wave and wind induced ship dynamic motion should be measured in real time domain for the validity of theoretical evaluation method such as sea-keeping performance and safety of mooring. In this paper, the basic design of sensors is discussed and some system configurations were shown. The developed system mainly consists of 4 kinds of sensors such as three-dimensional accelerator, two-dimensional tilt sensor, azimuth sensor and two displacement sensors. Using this measuring system, it can be obtained the 6 degrees of freedom of ship dynamic motions at sea and on berthing such as rolling, pitching, yawing, swaying, heaving, surging under the certain external forces.

• Journal of Biosystems Engineering
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• v.32 no.5
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• pp.339-347
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• 2007

A hexapod walking robot had been developed for gathering information in the field. The developed robot was $260{\times}260{\times}130$ ($W{\times}L{\times}H$, mm) in size and 14.7 N in weight. The legs had nineteen degrees of freedom. A leg has three rotational joints actuated by small servomotors. Two servomotors placed at ankle and knee played the roles of vertical joint for up and down motions of the leg and the other one placed at coxa played the role of horizontal joint for forward and backward motions. In addition, a servomotor placed at thorax between the front legs and the middle legs played the role of vertical joint for pumping the two front legs to climb stair or inclination. Walking motion of the robot was executed by tripod gait. The robot was controlled by manual remote-controller communicated by an infrared ray. Two controllers were equipped to control the walking of the robot. The sub-controller using PIC microcomputer (Microchips, PIC16F84A) received the 16 bit command signal from the manual remote controller, decoded it to 8bit and transmitted it to the main microcomputer (RENESAS, SH2/7045), which controlled the 19 servomotors using the PWM command signals. Walking speeds were controlled by adjusting the period of command cycle and the stride. Forward walking speed were within 100 cm/min to 300 cm/min. However, experimental walking speed had the error of 4-40 cm/min to compare with the theoretical one, because of slippage of the leg and the circular arc motion of servomotor of coxa.

• Coupled systems mechanics
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• v.13 no.4
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• pp.293-310
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• 2024

This paper investigates the dynamic response of structures during earthquakes and provides a clear understanding of soil-structure interaction phenomena. It analyses various parameters, comprising ground shear wave velocity and structure properties. The effect of soil impedance function form on the structural response of the system through the use of springs and dashpots with two frequency cases: independent and dependent frequencies. The superstructure and the ground were modeled linearly. Using the substructure method, two different approaches are used in this study. The first is an analytical formulation based on the dynamic equilibrium of the soil-structure system modeled by an analog model with three degrees of freedom. The second is a numerical analysis generated with 2D finite element modeling using ABAQUS software. The superstructure is represented as a SDOF system in all the SSI models assessed. This analysis establishes the key parameters affecting the soil-structure interaction and their effects. The different results obtained from the analysis are compared for each studied case (frequency-independent and frequency-dependent impedance functions). The achieved results confirm the sensitivity of buildings to soil-structure interaction and highlight the various factors and effects, such as soil and structure properties, specifically the shear wave velocity, the height and mass of the structure. Excitation frequency, and the foundation anchoring height, also has a significant impact on the fundamental parameters and the response of the coupled system at the same time. On the other hand, it have been demonstrated that the impedance function forms play a critical role in the accurate evaluation of structural behavior during seismic excitation. As a result, the evaluation of SSI effects on structural response must take into account the dynamic properties of the structure and soil accordingly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.597-604
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• 2010

This study focuses on the design of a mechanical joint for a zero moment crane (ZMC), which is a specialized loading/unloading system used in a mobile harbor (MH). The mechanical joint is based on the concept of zero moment point (ZMP), and it plays an important role in stabilizing a ZMC. For effective stabilization, it is necessary to ensure that the mechanical joint is robust to a wide variety of loads; further, the joint must allow the structures connected to it to perform rotational motion with two degrees of freedom By adopting a traditional design process, we designed a new mechanical joint; in this design, a universal joint is coupled with a spherical joint, and then, deformable rolling elements are incorporated. The rolling elements facilitate load distribution and help in decreasing power loss during loading/unloading. Because of the complexity of the proposed system, Kriging-based approximate optimization method is used for enhancing the optimization efficiency. In order to validate the design of the proposed mechanical joint, a structural analysis is performed, and a small-scale prototype is built.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.7-14
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• 1989

A trajectory control method being capable of singularity avoidance is proposed for a robot and positoner (R-P) system. In the proposed method, the damping factor of the Damped Least Square (DLS) method is adjusted by gradients of trajectory following errors so that the singularity avoidance can be achieved while mimimizing the errors. Two numerical examples are given by employing a Rhino robot with five degrees-of-freedom (d.o.f.) and two d.o.f's, where the method of maximizing the manipulagility the DLS method with a fixd damping factor and the proposed method are compared in terms of trajectory following errors, manipulabilities and joint velocities.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.11-22
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• 1999

In this study, the validity of the currently used seismic regulations for seismic isolated building structures is investigated, and a new formula for vertical distribution of seismic load is proposed. The distribution formula in UBC-91 did not provide sufficient safety, and thus revised in 1994. However it is pointed out that the revised formula overestimates the seismic load because of its similarity to that of the fixed-base structure. Therefore, in the proposed approach, it is intended to satisfy safety, economy, and applicability by combining the mode shapes of the seismic isolated structure idealized as two degrees of freedom system and those of fixed-base structure. For verification of the proposed formula, both a moment resisting frame and a shear wall system are analyzed. The results obtained from the proposed method turn out to be close to the results from a dynamic analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.185-196
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• 1988

In this study, a method of nonlinear dynamic analysis of suspension bridges subjected to random wind loads is pre.sented. The nonlinearity considered is the one due to the interaction between the motion of the bridge girder and the tertsion variation of the main cables. The equation of motion is formulated using a continuum approach. The coupling between the vertical and torsional motions are included in the analysis. The equation of motion is solved by using the mode superposition method. The analysis is carried out in the frequency domain utilizing the stochastic linearization technique on to the modal equations. In the linearization procedure, the nonlinear terms are approximated as linear ones with constant terms. The verification of the method has been performed on a case with four modal degrees of freedom. Example analyses are carried out on two suspension bridges for various wind speeds and wind force parameters. Numerical results indicate that, by including the nonlinearity into the analysis, the dynamic responses of the bridges, particularly in the vertical direction, change considerably.