• Journal of the Korean Society of Safety
• /
• v.6 no.3
• /
• pp.56-63
• /
• 1991

This study investigates reliability based design criteria for the erection members, and proposes practical algorithm which is based on Ellingwood's algorithm for the reliability analysis and the derivation of reliability based criteria. The magnitude of the uncertainties associated with load effects are chosen primarily by considering our level of practice. And thus the uncertainties so obtained are applied for the reliability analysis and the derivation of reliability based design criteria. A target reliability($\beta$$_{o}$=2.0) is selected as an appropriate value by analyzing the reliability levels of our current USD and WSD design standards. Them a set of load and resistance factors corresponding to the target reliability is proposed as a reliability based design provision, and furthermore a set of allowable stresses for steel having same level of reliability with the corresponding LRFD criteria is also prepared for the current WSD design provision. It may be concluded that the proposed LRFD reliability based design provisions and the corresponding allowable stresses give more rational design than the current code for erection membars.s.s.

• Wind and Structures
• /
• v.31 no.2
• /
• pp.143-152
• /
• 2020

The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor chosen by the designer and accordingly a certain ductility capacity needs to be achieved by the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. Firstly, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Secondly, the structure always possesses a certain level of ductility that the wind design does not benefit from. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty-five-story high-rise building previously tested at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressures from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigning these walls. The ductility demand of shear walls with reduced cross sections is assessed to justify the application of the load reduction factor "R".

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.9
• /
• pp.32-40
• /
• 2004

This paper deals with an automated computer-aided process planning and die design system by which designer can determine operation sequences even if they have a little experience in process planning and die design for axisymmetric products. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM softwares, DEFORM and ANSYS, to form a useful package. The system is composed of four main modules. The process planning and the die design modules consider several factors, such as the complexities of preform geometry, punch and die profiles, specifications of available multi former, and the availability of standard parts. They can provide a flexible process based on either the reduction in the number of forming sequences by combining the possible two processes in sequence, or the reduction of deviation of the distribution on the level of the required forming loads by controlling the forming ratios. Especially in die design module an optimal design technique and horizontal split die were investigated for determining appropriate dimensions of components of multi-former die set. It is constructed that the proposed method can be beneficial for improving the tool life of die set at practice.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.530-535
• /
• 2004

This paper considers a state set estimation (SSE) based model predictive control (MPC) for linear parameter- varying (LPV) systems with input constraint. We estimate, at each time instant, a feasible set of all states which are consistent with system model, measurements and a priori information, rather than the state itself. By combining a state-feedback MPC and an SSE, we design an SSE-based MPC algorithm that stabilizes the closed-loop system. The proposed algorithm is solved by semi-de�nite program involving linear matrix inequalities. A numerical example is included to illustrate the performance of the proposed algorithm.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.473-473
• /
• 2009

There have been many academic researches on the aerodynamic design of wind turbine based on blade element method (BEM) and momentum theory (MT, or actuating disk theory). However, in the real world, the turbine blade design requires many additional constraints more than theoretical analysis. The standard procedure is studied in the present paper to design new blades for the wind turbine system ranged from the small size from 1 to 10 kW. From the experience of full design of a 10 kW blade, the authors tried to set up a standard procedure for the aerodynamic design based on IEC 61400-2. Wind-turbine scale, rotating speed, and geometrical chord/twist distribution at the segmented span positions are calculated with a suitable BEM/MT code, and the geometrical shape of tip and root should be modified after considering various parameters: wing-tip vortex, aerodynamic noise, turbine efficiency, structural safety, convenience of fabrication, and even economic factor likes price, etc. The evaluated data is passed to the next procedure of structural design, but some of them should still be corresponded with each other: the fluid-structure interaction is one of those problems not yet solved, for example. Consequently, the design procedure of small wind-turbine blades is set up for the mass production of commercial products in this research.

• Journal of Korea Society of Industrial Information Systems
• /
• v.16 no.4
• /
• pp.119-125
• /
• 2011

The part family (PF) formation in a cellular manufacturing has been a key issue for the successful implementation of Group Technology (GT). Basically, a part has two different attributes; i.e., design and manufacturing. The respective similarity in both attributes is often conflicting each other. However, the two attributes should be taken into account appropriately in order for the PF to maximize the benefits of the GT implementation. This paper proposes a clustering algorithm which considers the two attributes simultaneously based on pareto optimal theory. The similarity in each attribute can be represented as two individual objective functions. Then, the resulting two objective functions are properly combined into a pareto fitness function which assigns a single fitness value to each solution based on the two objective functions. A GA is used to find the pareto optimal set of solutions based on the fitness function. A set of hypothetical parts are grouped using the proposed system. The results show that the proposed system is very promising in clustering with multiple objectives.

• Steel and Composite Structures
• /
• v.44 no.5
• /
• pp.633-649
• /
• 2022

This paper is first implemented with the bending behavior of three-dimensional functionally graded (3DFG) plates in the framework of level set-based topology optimization (LS-based TO). Besides, due to the suitable properties of the current design domain, the thin-plate spline (TPS) is recognized as a RBF to construct the LS function. The overall mechanical properties of the 3DFG plate are assessed using a power-law distribution scheme via Mori-Tanaka micromechanical material model. The bending response is obtained using the first-order shear deformation theory (FSDT). The mixed interpolation of four elements of tensorial components (MITC4) is also implemented to overcome a well-known shear locking problem when the thickness becomes thinner. The Hamilton-Jacobi method is utilized in each iteration to enforce the necessary boundary conditions. The mathematical formulas are expressed in great detail for the LS-based TO using 3DFG materials. Several numerical examples are exhibited to verify the efficiency and reliability of the current methodology with the previously reported literature. Finally, the influences of FG materials in the optimized design are explained in detail to illustrate the behaviors of optimized structures.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1613-1616
• /
• 1997

In order to develop a human hand mechanism, a 5-bar finger with redundant actuation is designed and implemented. an optimal set of acutator locations and link lengths for the case of one redundant actuator is obtained by employing a composite design index which simulataneously consider several performance indices such as workspace, isotropic index, and force transmission ratio. Each joing is driven by an compact actuator mechanism having ultrasonic motor and a gear set with poeneiometer an controlled by VME Bus-based control system.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.161-164
• /
• 2000

The architecture of microprocessor for a embedded system should be one that can perform more tasks with fewer instruction codes. The machine codes that high-level language compiler produces are mainly composed of specific ones, and codes that have small size are more frequently used. Extended Instruction Set Architecture (EISC) was proposed for that reason. We have designed pipe-line system for 64 bit EISC microprocessor. function level simulator was made for verification of design and instruction set architecture was also verified by that simulator. The behavioral function of synthesized logic was verified by comparison with the results of cycle-based simulator.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.1307-1311
• /
• 2004

This paper deals with an automated computer-aided process planning and die design system by which designer can determine operation sequences even if they have a little experience in process planning and die design for axisymmetric products. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM softwares, DEFORM and ANSYS, to form a useful package. They can provide a flexible process based on either the reduction in the number of forming sequences by combining the possible two processes in sequence, or the reduction of deviation of the distribution on the level of the required forming loads by controlling the forming ratios. Especially in die design module an optimal design technique and horizontal split die were investigated for determining appropriate dimensions of components of multi-former die set. It is constructed that the proposed method can be beneficial for improving the tool life of die set at practice.