• 한국산업융합학회 논문집
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• 제4권2호
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• pp.157-166
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• 2001

The purpose of this study is to examine the accuracy of the code provisions on lateral load distribution factors of prestressed concrete girder bridges. Most designers in Korea use the lever method or lateral load distribution formula in the existing design codes. However, the methods do not account for the effect of bridge skew or direction of diaphragm. Therefore, this study analysed the prestressed concrete girder bridge with grillage model for various girder spacings, directions of diaphragms, span lengths, and skews, and compared the results with those of existing design code. It has been found that lateral load distribution factors were proportional to the girder spacing while they were not significantly affected by the change of span length, direction of diaphragm, and skew. For bending moments, lateral load distribution factors from the grillage analysis were 60%~68% of those from Korean bridge design code. Therefore, the code provisions result in very conservative design. For support reactions, however, lateral load distribution factors from the grillage analysis were slightly greater than those from Korean bridge design code. Therefore, the capacity of bearings of the bridge with a large skew should be determined by grillage analysis.

• Steel and Composite Structures
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• 제30권3호
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• pp.293-304
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• 2019

The optimum cost of a reinforced concrete plane and space frames have been found by using the Genetic Algorithm (GA) method. The design procedure is subjected to many constraints controlling the designed sections (beams and columns) based on the standard specifications of the American Concrete Institute ACI Code 2011. The design variables have contained the dimensions of designed sections, reinforced steel and topology through the section. It is obtained from a predetermined database containing all the single reinforced design sections for beam and columns subjected to axial load, uniaxial or biaxial moments. The designed optimum beam sections by using GAs have been unified through MATLAB to satisfy axial, flexural, shear and torsion requirements based on the designed code. The frames' functional cost has contained the cost of concrete and reinforcement of steel in addition to the cost of the frames' formwork. The results have found that limiting the dimensions of the frame's beams with the frame's columns have increased the optimum cost of the structure by 2%, declining the re-analysis of the optimum designed structures through GA.

• Wind and Structures
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• 제32권5호
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• pp.439-452
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• 2021

The concept of Performance objective assessment is extended to wind engineering. This approach applies using the Database-Assisted Design technique, relying on the aerodynamic database provided by the National Institute of Standards and Technology (NIST). A structural model of a low-rise building is analyzed to obtain influence coefficients for internal forces and displacements. Combining these coefficients with time histories of pressure coefficients on the envelope produces time histories of load effects on the structure, for example knee and ridge bending moments, and eave lateral drift. The peak values of such effects are represented by an extreme-value Type I Distribution, which allows the estimation of the gust wind speed leading to the mean hourly extreme loading that cause specific performance objective compromises. Firstly a fully correlated wind field over large tributary areas is assumed and then relaxed to utilize the denser pressure tap data available but with considerably more computational effort. The performance objectives are determined in accordance with the limit state load combinations given in the ASCE 7-16 provisions, particularly the Load and Resistance Factor Design (LRFD) method. The procedure is then repeated for several wind directions and different dominant opening scenarios to determine the cases that produce performance objective criteria. Comparisons with two approaches in ASCE 7 are made.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.695-712
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• 2005

Hybrid coupled shear walls in tall buildings are known as efficient structural systems to provide lateral resistance to wind and seismic loads. Multiple hybrid coupled shear walls throughout a tall building should be joined to provide additional coupling action to resist overturning moments caused by the lateral loading. This can be done using a coupling beam which connects two shear walls. In this study, experimental studies on the hybrid coupled shear wall were carried out. The main test variables were the ratios of coupling beam strength to connection strength. Finally, this paper provides background for rational design guidelines that include a design model to behave efficiently hybrid coupled shear walls.

• Transactions on Control, Automation and Systems Engineering
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• 제4권3호
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• pp.231-238
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• 2002

In this paper, we present a new approach to autopilot design for skid-to-turn missiles which may have severe aerodynamic cross-couplings and nonlinearities with angle of attack. The model of missile motion is derived in the maneuver plane and, based on that model, pitch, yaw, and roll autopilot are designed. They are composed of a nonlinear term which compensates for the aerodynamic couplings and nonlinearities and a linear controller driven by the measured outputs of missile accelerations and angular rates. Besides the outputs, further information such as Mach number, dynamic pressure, total angle of attack, and bank angle is required. With the proposed autopilot and simple estimators of bank angle and total angle of attack, it is shown by computer simulations that the induced moments and some aerodynamic nonlinearities are properly compensated and that the performance is superior to that of the conventional ones.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.167-174
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• 2005

Through time-dependent analyses of RC bridges constructed by a movable scaffolding system (MSS) considering the construction sequence and creep deformation of concrete, structural responses related to the member forces are reviewed. On the basis of the compatibility condition and equilibrium equation at every construction stage, basic equations that can describe the moment variation with time in movable scaffolding construction are derived. By using the introduced relations, the design moment and its variation over time can easily be obtained with only the elastic analysis results and without additional time-dependent analyses considering the construction sequences. In addition, the design moments determined by the introduced equations are compared with the results from a rigorous numerical analysis with the objective of establishing the relative efficiencies of the introduced equations.

• 한국CDE학회논문집
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• 제15권4호
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• pp.306-313
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• 2010

In this paper, an acceleration based passenger evacuation simulation is performed. In order to describe a passenger‘s behavior in an evacuation situation, a passenger is modeled as a rigid body which translates in the horizontal plane and rotates along the vertical axis. The position and rotation angle of a passenger are calculated by solving the dynamic equations of motions at each time step. The destination force, the contact force, and the group force are considered as external forces and the moments due to each force are also considered. With the passenger model proposed in this paper, the test problems in International Maritime Organization, Maritime Safety Committee/Circulation 1238(IMO MSC/Circ.1238) are implemented and the effects of passenger rotation on the evacuation time are confirmed.

• 소성∙가공
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• 제10권4호
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• pp.329-337
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• 2001

The finite element simulation model and the program to calculate the reverse moment have been developed to analyse the stress state and deformation of pipe bending using local induction heating with small bending radius in this study. The reverse moment that is to be applied on the bending arm to control the wall thinning ratio of the bending outside to within a particular value. Even though the demand of pipes with small bending radius is increasing in power plants and ship buildings, the welded elbows are still widely used. The bending process with or without a reverse moment acting on the bending arm has been simulated. The reverse moments calculated from the developed program are in good agreement with the finite element simulations and the experiments.

• 전기학회논문지
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• 제59권8호
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• pp.1406-1415
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• 2010

As process technology for semiconductor goes beyond the ultra-deep submicrometer regime, interconnect reliability on a chip has become a serious design concern. As process parameters scale, interconnect widths are reduced rapidly while the current flowing through the interconnect does not decrease in a proportional manner. This trend increases current densities in metal interconnects which may lead to poor reliability for electromigration. Hence, it is critical to estimate the current amount passing through the interconnects earlier in semiconductor design stages. The purpose of this paper is to propose a fast yet accurate current estimation technique that can offer not only analysis time equivalent to those offered by the previous approximation methods but also a relatively precise estimation by using closed-form equations. The accuracy of the proposed technique was confirmed to be about 8 times better on average when compared to the previous work.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.409-413
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• 2007

To assure the structural integrity for the hub and low speed shaft (LSS) of the drive train, it is necessary to obtain the ultimate aerodynamic loads acting on the wind turbine blade. The aim of this study is to predict the time histories of 3 forces and 3 moments at the hub and the LSS based on the design load case of the IEC 61400-1. From the calculated results most of the load components have rotor revolution frequency whereas thrust and torque of the LSS show blade passage frequency. It turns out that the EWM wind condition involves the maximum ultimate loads at both hub and LSS of the horizontal axis wind turbine.