• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.73-82
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• 2022

The study presents a three-dimensional approach to simulate the nonlinear behavior of a 72 m long Ultra High Performance Fiber Reinforced Concrete (UHPFRC) pre-stressed box girder for a pedestrian bridge in Busan, South Korea. The concrete damage plasticity (CDP) model is adopted to model the non-linear behavior of the UHPFRC material, in which the material properties are obtained from uniaxial compressive and tensile tests. The simulation model based on the proposed stress-strain curve is validated by the results of four-point bending model tests of a 50 m UHPFRC pre-stressed box girder. The results from the simulation models agree with the experimental observations and predict the flexural behavior of the 50 m UHPFRC pre-stressed box girder accurately. Afterward, the validated model is utilized to investigate the flexural behavior of the 72 m UHPFRC pre-stressed box girder. Here, the load-deflection curve, stress status of the girder at various load levels, and connection details is analyzed. The load-deflection curve is also compared with design load to demonstrate the great benefit of the slender UHPFRC box girder. The obtained results demonstrate the applicability of the nonlinear finite element method as an appropriate option to analyze the flexural behavior of pre-stressed long-span girders.

• Structural Engineering and Mechanics
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• v.37 no.4
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• pp.385-399
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• 2011

The aim of this research is to model the behaviour of recently developed high force to volume (HF2V) passive energy dissipation devices using a simple finite element (FE) model. Thus, the end result will be suitable for use in a standard FE code to enable computationally fast and efficient analysis and design. Two models are developed. First, a detailed axial model that models an experimental setup is created to validate the approach versus experimental results. Second, a computationally and geometrically simpler equivalent rotational hinge element model is presented. Both models are created in ABAQUS, a standard nonlinear FE code. The elastic, plastic and damping properties of the elements used to model the HF2V devices are based on results from a series of quasi-static force-displacement loops and velocity based tests of these HF2V devices. Comparison of the FE model results with the experimental results from a half scale steel beam-column sub-assembly are within 10% error. The rotational model matches the output of the more complex and computationally expensive axial element model. The simpler model will allow computationally efficient non-linear analysis of large structures with many degrees of freedom, while the more complex and physically accurate axial model will allow detailed analysis of joint connection architecture. Their high correlation to experimental results helps better guarantee the fidelity of the results of such investigations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.1
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• pp.1-8
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• 2018

The purpose of this study is to implement modeling by applying the parametric technique to the atypical trusses of rigid retractable large space structures. The retractable large space structure requires a lot of time and skill in modeling nonlinear shapes or generating, interpreting, and reviewing many models by alternative. To solve these problems, we introduce firstly parametric modeling tool, secondly, we analyze the connection of atypical three-dimensional trusses of a rigid retractable large-space structure, and finally model it as parametric components of the developed trusses. Therefore, it is a future study to make effective modeling of the openable roof by developing the components that can realize the modeling of the truss classified by the opening and closing method, respectively.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.103-113
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• 2005

In the present study, the Direct Inelastic Design (DID) for steel structures developed in the previous study was improved to expand it applicability. The proposed design method can perform inelastic designs that address the design characteristics of steel structures: Group member design, discrete member sizes, variation of moment-carrying capacity according to axial force, connection types, and multiple design criteria and load conditions. The design procedure for the proposed method was established, and a computer program incorporating the design procedure was developed. The design results from the conventional elastic method and the DID were compared and verified by the existing computer program for nonlinear analysis. Compared with the conventional elastic design, the DID addressing the inelastic behavior reduced the total weight of steel members and enhanced the deformability of the structure. The proposed design method is convenient because it can directly perform inelastic design by using linear analysis for secant stiffness. Also, it can achieve structural safety and economical design by controlling deformations of the plastic hinges.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1714-1728
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• 2016

This paper presents improved harmonics extraction based on Adaptive Linear Neuron (ADALINE) algorithm for single phase photovoltaic (PV) shunt active power filter (SAPF). The proposed algorithm, named later as Improved ADALINE, contributes to better performance by removing cosine factor and sum of element that are considered as unnecessary features inside the existing algorithm, known as Modified Widrow-Hoff (W-H) ADALINE. A new updating technique, named as Fundamental Active Current, is introduced to replace the role of the weight factor inside the previous updating technique. For evaluation and comparison purposes, both proposed and existing algorithms have been developed. The PV SAPF with both algorithms was simulated in MATLAB-Simulink respectively, with and without operation or connection of PV. For hardware implementation, laboratory prototype has been developed and the proposed algorithm was programmed in TMS320F28335 DSP board. Steady state operation and three critical dynamic operations, which involve change of nonlinear loads, off-on operation between PV and SAPF, and change of irradiances, were carried out for performance evaluation. From the results and analysis, the Improved ADALINE algorithm shows the best performances with low total harmonic distortion, fast response time and high source power reduction. It performs well in both steady state and dynamic operations as compared to the Modified W-H ADALINE algorithm.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1126-1134
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• 2003

The signals obtained from the $5^{th}$-order (two-dimensional) Raman spectrum of a liquid can depend dramatically on the polarizations of the various light beams, but to date there has been no evidence presented that different polarization conditions probe any fundamentally different aspects of liquid dynamics. In order to explore the molecular significance of polarization we have carried out a molecular dynamics simulation of the $5^{th}$-order spectrum of a dilute solution of CS₂ in liquid Xe, perhaps the simplest system capable of displaying a full range of polarization dependencies. By focusing on the 5 distinct rotational invariants revealed by the different polarizations and by comparing our results with those from liquid Xe, a liquid whose spectrum has no significant polarization dependence, we discovered that the polarization experiments do, in fact, yield valuable microscopic information. With different linear combinations of the experimental response functions one can separate the part of the signal derived from the purely interaction-induced part of the many-body polarizability from the portion with the largest contributions from single-molecule polarizabilities. This division does not directly address the underlying liquid dynamics, but it significantly simplifies the interpretation of the theoretical calculations which do address this issue. We find that the different linear combinations differ as well in whether they exhibit nodal lines. Despite the absence of nodes with the atomic liquid Xe, observing the resilience of our solution's nodes when we artificially remove the anisotropy of our solute leads us to conclude that there is no direct connection between nodes and specifically molecular degrees of freedom.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.509-516
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• 2010

In this study a seismic retrofit scheme for the reinforced concrete moment framed structures was investigated using steel bracing and moment frames. The analysis model structure is a 3-story 3-bay moment frame structure designed only for gravity load. The stress/strain concentration in brace-RC frame connection was investigated using finite element analysis. To prevent premature joint failure, steel moment frames were placed inside of middle bay of the RC frame. Two types of braces, steel braces and buckling restrained braces(BRBs), were used for retrofit, and the ductility and the strength of the structure before and after the retrofit were compared using nonlinear static and dynamic analyses. According to the analysis results, the strength and ductility of the structure retrofitted by the moment frames and braces increased significantly. The added steel frame did not contribute significantly to the increase of lateral strength mainly because the size is relatively small.

• Computers and Concrete
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• v.18 no.3
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• pp.297-317
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• 2016

Current codes recommend large amounts of shear reinforcement for reinforced concrete beam-column joints that causes significant bar congestion. Increase in congestion of shear reinforcement in joint core (connection zone), leads to increase accomplishment problems. The congestion may also lead to diameter limitations on the beam bars relative to the joint dimensions. Using double headed studs instead of conventional closed hoops in reinforced concrete beam-column joints reduces congestion and ensures easier assembly of the reinforcing cage. The purpose of this research is evaluating the efficiency of the proposed reinforcement. In this way, 10 groups of exterior beam-column joints are modeled. Each group includes 7 specimens by different reinforcing details in their joint core. All specimens are modeled by using of ABAQUS and analyzed subjected to cyclic loading. After verification of analytical modeling with an experimental specimen, 3D nonlinear specimens are modeled and analyzed. Then, the effect of amount and arrangement of headed studs on ductility, performance, ultimate strength and energy absorption has been studied. Based on the results, all joints reinforced with double headed studs represent better performance compared with the joints without shear transverse reinforcement in joints core. The behavior of the former is close to joints reinforced with closed hoops and cross ties according to the seismic design codes. By adjusting the arrangement of double-headed studs, the decrease in ductility, performance, ultimate moment resistant and energy absorption reduce to 2.61%, 0.90%, 0.90% and 1.66% respectively compared with the joints reinforced by closed hoops on the average. Since the use of headed studs reduces accomplishment problems, these amounts are negligible. Therefore, use of double-headed studs has proved to be a viable option for reinforcing exterior beam-column joints.

• Korean journal of applied entomology
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• v.56 no.1
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• pp.1-18
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• 2017

Temperature-dependent development model is an essential component for forecasting models of insect pests as well as for insect population models. This study reviewed the nonlinear models which explain the relationship between temperature and development rate of insects. In the present study, the types of models were classified largely into empirical and biophysical model, and the groups were subdivided into subgroups according to the similarity of mathematical equations or the connection with original idea. Empirical models that apply analytical functions describing the suitable shape of development curve were subdivided into multiple subgroups as Stinner-based types, Logan-based types, performance models and Beta distribution types. Biophysical models based on enzyme kinetic reaction were grouped as monophyletic group leading to Eyring-model, SM-model, SS-mode, and SSI-model. Finally, we described the historical development and characteristics of non-linear development models and discussed the availability of models.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.856-865
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• 2003

Current design provisions and guide for performance-based design do not accurately evaluate seismic performance of flat plate system. In the previous companion studies, parametric studies using nonlinear finite element analyses were performed to investigate behavior of the flat plate, and based on the numerical results, design methods that can predict the bending moment-carrying capacity and the corresponding deformability of the flat plate was developed. In the present study, a generalized moment-rotation relation of the flat plate was developed based on the previous studies and the numerical analyses. The proposed method was verified by the comparisons with existing experiments. In addition, the effective stiffness of the flat plate corresponding to 0.2 percent of lateral drift that is generally regarded as the serviceability limit was proposed, so as to evaluate conveniently deflection of the structure subject to wind load.