• Structural Engineering and Mechanics
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• v.35 no.5
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• pp.593-616
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• 2010

The seismic performance of reinforced concrete (RC) bridge columns is a significant issue because the interaction of flexural ductility and shear capacity of such columns with varied amounts of lateral reinforcement is not well established. Several relationships between flexural ductility and shear capacity have been proposed by various researchers in the past. In this paper, a parametric study on RC bridge columns is conducted using a nonlinear finite element program, "Simulation of Concrete Structures (SCS)", developed at the University of Houston. SCS has been previously used to predict the seismic behavior of such columns. The predicted results were compared with the test results obtained from experiments available in literature. Based on the results of the parametric study performed in this paper, a set of new relationships between flexural ductility and shear capacity of RC columns is proposed for seismic design.

• Steel and Composite Structures
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• v.12 no.2
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• pp.93-115
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• 2012

This paper presents a numerical investigation of the mechanical behaviour of extended end - plate steel connections including comparison with full size experiments. Contact and friction laws have been taken into account with nonlinear, three dimensional finite element analysis. Material and geometric nonlinearities have been implemented to the model, as well. Results are then compared with experimental tests conducted at the Jordan University of Science and Technology. According to the most significant observation of the analysis, a separation of the column flange from the extended end - plate occurs. Other important structural parameters of the connection, like the impact of some column stiffeners on the overall response, local buckling of the column and friction of the beam to column interface, have been examined as well.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.8
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• pp.377-386
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• 2005

This paper presents the control algorithm of single-phase hybrid active power filter for the compensation of harmonic current components in nonlinear R-L load with passive active Power filters. To construct two phase system, an imaginary second phase was made. In this proposed method, the new signal which is the delayed through the filtering by the phase-delay property of low-pass filter is used as the secondary phase. Because two-phases have the different phase, the instantaneous calculation of harmonic current is possible. In this paper, a reference voltage is created by multiplying the coefficient k by the compensation current using the rotating reference frame synchronized with the source-frequency, not applying to instantaneous reactive power theory which has been used with the existing fixed reference frames In order to verify the validities of the proposed control methods, experiments are carried out with the prototypes of single-phase hybrid active power filter.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.51-59
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• 1997

This paper presets a methodology of improving a conventional model in power systems using Genetic Algorithms(GAs) and suggests a GAs-based model which can directly solve the real-valued optimum in an optimization procedure. In applying GAs to the power flow, a new fitness mapping method is proposed using the proposed using the probability distribution function for all the payoffs in the population pool. In this approach, both the notions on a way of the genetic representation, and a realization of the genetic operators are fully discussed to evaluate he GAs' effectiveness. The proposed method is applied to IEEE 5-bus, 14-bus and 25-bus systems and, the results of computational experiments suggest a direct applicability of GAs to more complicated power system problems even if they contain nonlinear algebraic equations.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.12
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• pp.714-722
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• 2002

This paper presents a control algorithm for a 3-phase 4-wire series active Power filter. This control algorithm compensates harmonics, input power factor and neutral line currents which are generated by balanced or unbalanced nonlinear loads. The advantage of this control algorithm is direct extraction of compensation voltage references. Therefore, the calculation time is shortened and the performance of the series active power filter is improved. The compensation principle of the proposed control algorithm is presented in detail. A 3KVA laboratory prototype of the three-phase four-wire series active power filter was built and experiments have been carried out. Experimental results are shown to verify the effectiveness of the proposed control algorithm.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.13-18
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• 2000

Recently due to the environmental pollution and the requirement for the substitute energy the interest for development of the solar energy system has been highly escalated It has been approved that the solar energy is a very useful on e because of purity and low cost. Some studies about the evaluation of solar radiation on the land has been carried out but few studies on the sea. This paper deals with a study on the evaluation of solar radiation on the sea. The experiments were carried out on the training vessel on the adjacent water of Korea Japan and China for twenty days. The distributions of solar radiation from the sea were changed into nonlinear in from according to the temperature. The solar radiation on the sea has a great influence on the velocity of wind as well as the temperature The distribuition of solar radiation has higher values on the track of the coastal sea than the open sea at same conditions.

• Journal of Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.1-6
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• 2006

Modulation theory describes propagation of surface waves with deep wave number and frequency modulation. Locally spectrally narrow wave packet can have accumulated large scale frequency shift of carrier wave during propagation. Some important nonlinear modulation effects, such as negative frequencies, phase kinks, crest pairing, etc., often observed experimentally at long fetch propagation of finite amplitude surface wave trains, are reproduced by the proposed theory. The presented model permits also to analyze the appropriately short surface wave packets and modulation periods. Solutions show the wave phase kinks to arise on areas' of relatively small free surface displacement in complete accordance with the experiments.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.211-216
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• 1997

An inverse method with regularization has been developed to determine the viscoelastic properties of trabecular bone. A series of stress relaxation experiments were performed under the condition of uniaxial compression stress state. Optimization has been formulated within the framework of nonlinear least-squares and a modified Gauss-Newton method with a zeroth-order regularization technique. The stress relaxation behavior of trabecular bone was analyzed using a standard viscoelastic model. The present study clearly shows that trabecular bone exhibits typical viscoelastic stress relaxation behavior, and the obtained material parameters well represent the viscoelastic behavior of trabecular bone.

• Computers and Concrete
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• v.20 no.4
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• pp.381-389
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• 2017

The various types of structural materials that are available in the construction industry nowadays make it necessary to predict their stress-strain behavior. Geopolymer are alternatives for ordinary Portland cement concrete that are made from pozzolans activation. Due to relatively new material, many mechanical specifications of geopolymer are still not yet discovered. In this study, stress-strain behavior has been provided from experiments for unconfined geopolymers. Modulus of Elasticity and stress-strain behavior are critical requirements at analysis process and knowing complete stress-strain curve facilitates structural behavior assessment at nonlinear analysis for structures that have built with geopolymers. This study intends to investigate stress-strain behavior and modulus of elasticity from experimental data that belongs for geopolymers varying in fineness and mix design and curing method. For the sake of behavior determination, 54 types of geopolymer are used. Similar mix proportions are used for samples productions that have different fineness and curing approach. The results indicated that the compressive strength ranges between 7.7 MPa and 43.9 MPa at the age of 28 days curing.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.127-134
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• 2015

Recently, the external bonding of carbon fiber reinforced polymer (CFRP) sheets has come to be regarded as a very effective method for strengthening of reinforced concrete structures. The behavior of CFRP-strengthened RC structure is mainly governed by the interfacial behavior, which represents the stress transfer and relative slip between concrete and the CFRP sheet. In this study, the effects of bonded length, width and concrete strength on the interfacial behavior are verified and a bond-slip model is proposed. The proposed bond-slip model has nonlinear ascending regions and exponential descending regions, facilitated by modifying the conventional bilinear bond-slip model. Finite element analysis results of interface element implemented with bond-slip model have shown good agreement with the experimental results performed in this study. It is found that the failure load and strain distribution predicted by finite element analysis with the proposed bond-slip are in good agreement with results of experiments.