• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.730-738
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• 2007

As well known when the linear machine is operated between two points repeatedly under positioning control, there are various positioning error at the moment of zero speed owing to the non-linear disturbance like as unpredictable friction force. To remove this positioning error, a simple least order disturbance observer is introduced and is actually implemented in this study. Due to this simple algorithm the over-all machine system can be modified to simple arbitrary given one-mass load without any disturbance. So, the total construction process for positioning control system is much easier than old one. Moreover, to generate a proper effective position profile with the limited actual machine force, a very powerful on-line mass identification algorithm using the load force estimator is presented. In the proposed mass identification algorithm, the exact load mass can be calculated during only one moving stage under a normally generated position profile. All presented algorithm is verified with experimental result with commercial linear servo machine system.

• Journal of the Korean Institute of Navigation
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• v.11 no.2
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• pp.73-88
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• 1987

It is well known that the height of tank metacenter above the centroid of fluid in a tank is given by i/v where I is the inertia moment of free surface and v is the fluid volume. It is supposed in this formula that the inclination of ship is small and that the free surface of fluid do not touch the top and the bottom of tank. It the inclination of ship is large, the height of tank metacenter may be possibly greater than that given by i/v. The height of tank metacenter is smaller than i/v when the free surface of fluid touch the top or the bottom of tank. The reasonable method to calculate the height of tank metacenter is presented in this paper and prepared in FORTRAN program by FUNCTION EFFRES. The approximate formula was also developed and given by $g_m=(1+\frac{2}{1}tan^2\theta)[1-EXP\{-12(\frac{\alpha(1-\alpha)k}{tan\theta})^{1.25}\}]\frac{i}{v}$ where $g_m$ is the distance from the centroid of fluid to the tank metacenter, $\theta$ is inclined angle of ship, $\alpha$ is the ratio of filled volume to tank capacity and k is the ratio of the depth to the width of tank. The values calculated by the approximate formula given in this paper were compared with the exact values from the computer program and proved out to be sufficiently precise for practical use.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.253-260
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• 1998

An approximate method for the calculation of creep deflections of reinforced concrete beams under sustained service loads is proposed. The position of neutral axis and strain and stress distribution of fully cracked section after creep is determined from the requirements of strain compatibility and equilibruim of a section and then the long-term flexural rigidity of fully cracked section is determined based on the new neutral axis. The long-term flexural rigidity of uncracked section at the level of the reinforcenment. The approach of calculating long-term effective flexural rigidity and defections is similar to the current American Concrete Institue procedure for calculating effecitve moment of inertia and short-term deflections. The accuracy of the analysis is verified by comparison with several experimental mesurements of beam deflectons. The result is good between the theotetical values and mesured valus.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.101-112
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• 2022

Expanding urbanization practices result in high numbers of buildings being developed in city centers. This high building concentration leads to an increased fire risk, resulting in higher casualty rates and increased economic damages compared to fires in the past. The purpose of this study was to analyze the structural behavior of fire-damaged reinforced concrete buildings using analytical methods and to suggest methods of improving fire resistance in the event of a fire. Damage levels were measured using commercial software to apply the finite element method, ABAQUS, and MIDAS GEN to the dataset. Load-deflection curves were calculated using the effective area and moment of inertia of the fire-damaged columns provided by ABAQUS. The results of this analysis indicate that fire-damaged beams with experience greater deflection from indoor fires than they will from outdoor fires. Fires that occurred on the middle floors were more dangerous than those occurring on higher floors, and eccentrically loaded columns experienced more damage than axially loaded columns. The results indicate that these methods accurately predict structural behaviors of fire damaged concrete columns by considering fire exposure area and eccentric loading.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.7
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• pp.3-10
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• 2018

Steel fiber reinforced concrete can improve the resistance to cracking by adding steel fibers when mixing concrete. It can reduce the temperature and shrinkage cracks, and its flexural performance can be improved by increasing the effective moment of inertia. In this study, the deck-plate was used to replace the concrete form and reinforcing bars, and the steel fiber reinforced concrete was used to control the shrinkage and temperature cracks, and improve the flexural performance of the slab. Total 9 slab specimens were tested for analyzing the structural performance and serviceability. As a results, flexural capacity of the slab with deck-plate was evaluated to be superior to that of the normal reinforced concrete slab specimens with the same tensile reinforcement. The steel fiber reinforced concrete was found to have about 8% flexural capacity increase depending on the steel fiber content $15.7kg/m^3$. Also, in terms of flexural stiffness, the specimens using steel fiber reinforced concrete for the same parameters were evaluated to have a stiffness increase of about 30% compared with the case of using ordinary concrete. Especially, it was found that the stiffness of the test results was significantly higher than the analytical result because the increase of the tensile strength of the steel fiber reinforced concrete is not reflected in the current structural code.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.361-373
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• 2022

This paper examines the flexural performance of concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars under fatigue loading. Experiments were carried out on concrete beams of size 1500×200×100 mm reinforced with 10 mm and 13 mm diameter GFRP bars under fatigue loading. Experimental investigations revealed that fatigue loading affects both strength and serviceability properties of GFRP reinforced concrete. Experimental results indicated that (i) the concrete beams experienced increase in deflection with increase in number of cycles and failed suddenly due to snapping of rebars and (ii) the fatigue life of concrete beams drastically decreased with increase in stress level. Analytical model presented a procedure for predicting the deflection of concrete beams reinforced with GFRP bars under cyclic loading. Deflection of concrete beams was computed by considering the aspects such as stiffness degradation, force equilibrium equations and effective moment of inertia. Nonlinear finite element (FE) analysis was performed on concrete beams reinforced with GFRP bars. Appropriate constitutive relationships for concrete and GFRP bars were considered in the numerical modelling. Concrete non linearity has been accounted through concrete damage plasticity model available in ABAQUS. Deflection versus number of cycles obtained experimentally for various beams was compared with the analytical and numerical predictions. It was observed that the predicted values are comparable (less than 20% difference) with the corresponding experimental observations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.77-86
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• 2003

Dynamic response of baffled fuel-storage tank in turnaround motion is simulated using the ALE finite element method. Fuel-storage tank undergoes abrupt impact load caused by inertia force of internal fuel in turnaround motion. Also, large dynamic force and moment caused by this load influence structural stability and control system. In this paper, ring-type baffles are adopted to suppress the dynamic influence. Through the parametric analysis with respect to the baffle number and location, the effects of baffle on the dynamic response of baffled fuel-storage tank is analyzed. The ALE finite element method is adopted for the accurate and effective simulation of the hydrodynamic interaction between fluid and structure.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.257-268
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• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.25-34
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• 2009

RC flat plate, which has no large flexural stiffness by boundary beams, may be governed by serviceability as well as strength condition. A construction sequence and its impact on distributions of construction loads among slabs tied by shores are decisive factors on immediate and long term performances of flat plate. The over-loading and tensile cracking in early-aged slabs significantly increase the deflection of flat plate system. In this study, for slab deflections, the practical analysis scheme using a linear analysis program is formulated with considering construction sequence and concrete cracking effects. The concept of the effective moment of inertia in calculating deflections of one-way bending member, that is presented in structural design codes, is extended to the finite element analysis of the two-way slab system of flat plates. Effects of over-loads during construction on deflections of flat plate system are analyzed by applying the proposed practical analysis scheme into the critical construction load conditions calculated from the simplified method.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.469-484
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• 2023

A deep recursive bidirectional Cuda Deep Neural Network Long Short Term Memory (Bi-CuDNNLSTM) layer is recruited in this paper to predict the entire force time histories, and the corresponding hysteresis and backbone curves of reinforced concrete (RC) bridge piers using experimental fast and slow cyclic tests. The proposed stacked Bi-CuDNNLSTM layers involve multiple uncertain input variables, including horizontal actuator displacements, vertical actuators axial loads, the effective height of the bridge pier, the moment of inertia, and mass. The functional application programming interface in the Keras Python library is utilized to develop a deep learning model considering all the above various input attributes. To have a robust and reliable prediction, the dataset for both the fast and slow cyclic tests is split into three mutually exclusive subsets of training, validation, and testing (unseen). The whole datasets include 17 RC bridge piers tested experimentally ten for fast and seven for slow cyclic tests. The results bring to light that the mean absolute error, as a loss function, is monotonically decreased to zero for both the training and validation datasets after 5000 epochs, and a high level of correlation is observed between the predicted and the experimentally measured values of the force time histories for all the datasets, more than 90%. It can be concluded that the maximum mean of the normalized error, obtained through Box-Whisker plot and Gaussian distribution of normalized error, associated with unseen data is about 10% and 3% for the fast and slow cyclic tests, respectively. In recapitulation, it brings to an end that the stacked Bi-CuDNNLSTM layer implemented in this study has a myriad of benefits in reducing the time and experimental costs for conducting new fast and slow cyclic tests in the future and results in a fast and accurate insight into hysteretic behavior of bridge piers.