• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.361-375
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• 2014

The main aim of this paper is to investigate the relationship between thickness and height of the axially symmetric cylindrical reinforced concrete (RC) walls by the help of a meta-heuristic optimization procedure. The material cost of the wall which includes concrete, reinforcement and formwork, was chosen as objective function of the optimization problem. The wall thickness, compressive strength of concrete and diameter of reinforcement bars were defined as design variables and tank volume, radius and height of the wall, loading condition and unit cost of material were defined as design constants. Numerical analyses of the wall were conducted by using superposition method (SPM) considering ACI 318-Building code requirements for structural concrete. The optimum wall thickness-height relationship was investigated under three main cases related with compressive strength of concrete and density of the stored liquid. According to the results, the proposed method is effective on finding the optimum design with minimum cost.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1041-1044
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• 2002

Inchworm linear motor is one of the ultra precision position apparatuses and has many kinds of forms and structures according to the conditions of working space and range. In this paper, the Inchworm linear motor consists of three PZTs(Piezo-electric transducer), three columns ma two plates. finite element method was used to determine the type or hinges installed in column of inchworm linear motor DOE(Design of experiment) was used to determine the optimal design condition of a column by comparing the von-mises stresses according to the change of thickness of hinge, round of hinge, height of arm, angle of v-notch, round of v-notch and thickness of column. From the result, round of hinge, height of arm and thickness of hinge were determined a effective design parameters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.66-77
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• 1992

A prototype probabilistic approach to thickness design for asphalt pavement surface course was developed using first-order second moment probability model. The tensile strain (load effect) developing at the bottom of surface layer due to the wheel load and the critical strain (resistance) of asphalt concrete were used as random variables for pavement reliability analysis. Based on the parameters for load effect and resistance data collected from reference and field, simulated data were generated by Monte Carlo method for reliability evaluation of the pavement for a typical rural highway. Thickness of pavement surface course was defined in terms of target reliability of the pavement, growth factor of traffic, design life of pavement and resistance of the asphalt concrete to be placed on the pavement. According to these rationales, prototype thickness design chrats were sugested through example studies. From these, similar design charts can be developed for many pavements if appropriate data and target reliability are determined.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.19-28
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• 2012

PURPOSES : Recently, the mechanistic-empirical overlay pavement design program that is linked with Korea Pavement Research Program (KPRP) has been developed. This paper focused on establishing the framework and developing the program for the asphalt overlay design over the existing asphalt concrete pavement. METHODS : The overlay pavement design program developed in this study was investigated to assess the sensitivity to various pavement conditions, such as the damage level and thickness of existing layers. In addition, the actual overlay design on currently performing pavement was carried out as a practical example. RESULTS : From the sensitivity analysis, it was found that the thickness and damage level of existing asphalt layer mostly affect the overlay design results. In addition, under the same condition, the overlay pavement would better perform in cold region. From the overlay design with the actual condition, it is noted that the overlay thickness varies depending on the given condition. CONCLUSIONS : Based on various evaluations, it was concluded that the overlay design program developed in this study is a reliable and reasonable tool to be used in the actual pavement design.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.4
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• pp.15-27
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• 2021

In this study, the effect of design factors in a pump station on the pressure variations which are the main cause of water hammering has been investigated by numerical simulations. As design factors, the flow rate, Young's modulus, diameter, thickness, roughness coefficient of pipeline are considered. The relationships between the pressure variations and the design factors are analyzed. The results show that the pressure variation increases sensitively with the flow rate and Young's modulus, and increases gradually with the thickness and roughness coefficient of pipe, whereas it decreases with the pipe diameter. The wavelength of the pressure wave becomes longer for a smaller Young's modulus, a smaller pipe thickness and a bigger pipe diameter. These relationships are nondimensionalized, and logarithmic curve-fitted functions are proposed by regression analysis. Most effective factors on the nondimensional pressure variation is Young's modulus. Flow rate, roughness coefficient, relative thickness and pipe diameters are the next impact factors.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.428-435
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• 2011

In general, thickness of the sublayers under track is designed based on concept of vertical soil reaction value or vertical stiffness. However, this design method cannot take consideration into soil-track interaction under repetitive load, traffic condition and velocity of the train. Furthermore, the reinforced roadbed soils experience complex behavior that cannot be explained by conventional stress-strain relation expressed as soil reaction value k. The reinforced roadbed soils also can produce cumulative permanent deformation under repetitive load caused by train. Therefore new design method for the sublayers under track must be developed that can consider both elastic modulus and permanent deformation. In this study, a new design concept, a rule-of-thumb, is proposed as the form of design monograph that is developed using elastic multi-layer and finite element programs by analyzing stress and deformation in the sublayers with changing the thickness and elastic modulus of the sublayers and also using data obtained from repetitive triaxial test. This new design concept can be applied to design of the reinforced roadbed before developing full version of design methodology that can consider MGT, axial load and the material properties of the layers. The new design monograph allows the user to design the thickness of the reinforced roadbed based on permanent deformation, elastic modulus and MGT.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.873-876
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• 2002

This paper presents the effect of internal corrosion, external corrosion, material properties, operation condition, earthquake, traffic load and design thickness in pipeline on the failure prediction using a failure probability model. A nonlinear corrosion is used to represent the loss of pipe wall thickness with time. The effects of environmental, operational, and design random variables such as a pipe diameter, earthquake, fluid pressure, a corrosion rate, a material yield stress and a pipe thickness on the failure probability are systematically investigated using a failure probability model for the corrosion pipeline.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.403-410
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• 2002

This paper presents the effect of internal corrosion, external corrosion, material properties, operation condition, earthquake, traffic load and design thickness in pipeline on the failure prediction using a failure probability model. A nonlinear corrosion is used to represent the loss of pipe wall thickness with time. The effects of environmental, operational, and design random variables such as a pipe diameter, earthquake, fluid pressure, a corrosion rate, a material yield stress and a pipe thickness on the failure probability are systematically investigated using a failure probability model for the corrosion pipeline.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.3
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• pp.134-141
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• 1996

In this paper, we formulate the mathematical model for a single-stand rolling mill and design control systems for the thickness control at the exit of roll stand and for the tension control of the strip in the process. We propose a thickness controller based on the Internal Model Control structure which can be an effective application when the frequency components of the thickness deviation of the entry strip are known and, show how it can be appropriately combined with BISRA AGC method for a precise thickness control while maintaining the robustness against the modeling error of the mill modulus. It is illustrated by simulations that the proposed thickness control method gives better performance than existing methods and has the robustness against the modeling error of the mill modulus as well.

• International Journal of Highway Engineering
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• v.11 no.1
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• pp.187-194
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• 2009

This paper presents the development of transfer function accounting for cross-anisotropic behavior of aggregate base material for the pavement thickness design. The stress distributions predicted by nonlinear cross-anisotropic finite element program were realistic by eliminating excessive tensile stress at the bottom of the base layer and the critical pavement responses predicted by nonlinear cross-anisotropic model are higher than those predicted by linear or nonlinear isotropic models (Kim, 2004, Kim et at., 2005). Since the previously developed transfer functions such as Asphalt Institute and Chevron models, etc. were based on the critical responses obtained from linear isotropic model, those equations are not appropriate for the thickness design nonlinear cross-anisotropic base behavior. Therefore, the development of usable transfer functions for nonlinear cross-anisotropic model is ever more important. When the newly developed transfer functions were compared with AASHTO method for the thickness design, the newly developed transfer functions produce approximately 25mm reduced UAB thickness in AASHTO thickness design and this illustrates that linear isotropic model results in more conservative pavement design.