• Computational Structural Engineering
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• v.10 no.4
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• pp.315-325
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• 1997

This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.

• Structural Engineering and Mechanics
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• v.53 no.2
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• pp.311-324
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• 2015

The purpose of this study was to investigate experimentally the fatigue performance of reinforced concrete (RC) beams with hot-rolled ribbed fine-grained steel bars of yielding strength 500MPa (HRBF500). Three rectangular and three T-section RC beams with HRBF500 bars were constructed and tested under static and constant-amplitude cyclic loading. Prior to the application of repeated loading, all beams were initially cracked under static loading. The major test variables were the steel ratio, cross-sectional shape and stress range. The stress evolution of HRBF500 bars, the information about crack growth and the deflection developments of test beams were presented and analyzed. Rapid increases in deflections and tension steel stress occured in the early stages of fatigue loading, and were followed by a relatively stable period. Test results indicate that, the concrete beams reinforced with appropriate amount of HRBF500 bars can survive 2.5 million cycles of constant-amplitude cyclic loading with no apparent signs of damage, on condition that the initial extreme tensile stress in HRBF500 steel bars was controlled less than 150 MPa. It was also found that, the initial extreme tension steel stress, stress range, and steel ratio were the main factors that affected the fatigue properties of RC beams with HRBF500 bars, whose effects on fatigue properties were fully discussed in this paper, while the cross-sectional shape had no significant influence in fatigue properties. The results provide important guidance for the fatigue design of concrete beams reinforced with HRBF500 steel bars.

• Journal of IKEEE
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• v.16 no.2
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• pp.69-75
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• 2012

In this paper, microstrip array antenna is proposed for the wireless communication of DSRC(dedicated short range communication) scheme at 5.8GHz, which works as a part of the Navigation terminal. The microstrip patches minimized from a rectangular microstrip antenna with a half wavelength are arrayed to be mounted on the narrow and long area in the top side of the navigation terminal. Besides, the array antenna can limit its own beamwidth to the driving lane and has better directivity. It is simulated to verify the validity of the proposed application. The prototype fabricated has a volume of $18{\times}40{\times}0.8mm^3$. From the measurement, it has circular polarization performance of 4dB axial ratio over 40MHz frequency band. In addition, antenna gain of 6.2dBi and 3dB beamwidth of $70^{\circ}$ at cross section of driving lane have been achieved.

• Structural Engineering and Mechanics
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• v.31 no.4
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• pp.453-475
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• 2009

The literature regarding the free vibration analysis of Bernoulli-Euler and Timoshenko beams on elastic soil is plenty, but the free vibration analysis of Reddy-Bickford beams on elastic soil with/without axial force effect using the Differential Transform Method (DTM) has not been investigated by any of the studies in open literature so far. In this study, the free vibration analysis of axially loaded Reddy-Bickford beam on elastic soil is carried out by using DTM. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments in this study. The governing differential equations of motion of the rectangular beam in free vibration are derived using Hamilton's principle and considering rotatory inertia. Parameters for the relative stiffness, stiffness ratio and nondimensionalized multiplication factor for the axial compressive force are incorporated into the equations of motion in order to investigate their effects on the natural frequencies. At first, the terms are found directly from the analytical solutions of the differential equations that describe the deformations of the cross-section according to the high-order theory. After the analytical solution, an efficient and easy mathematical technique called DTM is used to solve the governing differential equations of the motion. The calculated natural frequencies of one end fixed and the other end simply supported Reddy-Bickford beam on elastic soil using DTM are tabulated in several tables and figures and are compared with the results of the analytical solution where a very good agreement is observed and the mode shapes are presented in graphs.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.409-412
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• 2004

Over last decade extensive researches have been undertaken on the strength behaviour of Fiber Reinforced Concrete(FRC) structures. But the use of Ultra-High Strength Steel Fiber Cementitious Concrete Composites is in its infancy and there is a few experiments, analysis method and design criteria on the structural elements constructed with this new generation material which compressive strength is over 150 MPa and characteristic behaviour on the failure status is ductile. The objective of this paper is to investigate and analyze the behaviour of reinforced rectangular structural members constructed with ultra high performance cementitious composites (UHPCC). This material is known as reactive powder concrete (RPC) mixed with domestic materials and its compressive strength is over 150MP. The variables of test specimens were shear span ratio, reinforcement ratio and fiber quantity. Even if there were no shear stirrups in test specimens, most influential variable to determine the failure mode between shear and flexural action was proved to be shear span ratio. The characteristics of ultra high-strength concrete is basically brittle, but due to the steel fiber reinforcement behaviour of this structure member became ductile after the peak load. As a result of the test, the stress block of compressive zone could be defined. The proposed analytical calculation of internal force capacity based by plastic analysis gave a good prediction for the shear and flexural strength of specimens. The numerical verification of the finite element model which constitutive law developed for Mode I fracture of fiber reinforced concrete correctly captured the overall behaviour of the specimens tested.

• Korean Journal of Construction Engineering and Management
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• v.15 no.3
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• pp.128-135
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• 2014

This paper studied design of slip form system considering the erection of a pylon mock-up. The height of the pylon is 10 m. A rectangular hollow cross-section was considered. The outer and inner dimensions of the pylons were varied with respect to the height. The thickness of 1 sides among the 4 faces were varied. Accordingly the slip form was designed to respond to continuous changes in its dimensions and thickness. Structural analysis was conducted to examine structural safety of the slip form. Virtual construction by BIM proved its practicality. The developed design technologies were successfully applied to the erection of a 10m high pylon executed for field verification test.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.68-74
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• 2008

Measurements were performed to investigate the effects on flame and pressure development by varying locations of multiple obstacles in a top-venting explosion chamber. The chamber dimension was 1000 mm in height with a $700\;{\times}\;700\;mm^2$ cross-section and a rectangular vent area of $700\;{\times}\;700\;mm^2$. Three different multiple obstacles with blockage ratio of 30% were used by changing from 200 mm, 500 mm to 800 mm in heights within the chamber. Temporally resolved flame front images were recorded by a high speed camera to investigate the interaction between the propagating flame and the obstacles. The results showed that the triangular bar caused the fastest flame developments at given times whereas the lowest was obtained with the cylindrical bar. It was also found that local flame displacement speeds of different obstacles were sensitive to the locations of obstacles. The local speed becomes larger in going from 200 mm, to 500 mm and to 800 mm in heights. The obstacles in height of 800 mm yielded the highest overpressure whereas the lowest was in height of 200 mm.

• Journal of Navigation and Port Research
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• v.35 no.5
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• pp.407-414
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• 2011

Floating architecture is the most effective way to accommodate itself to sea-level rise due to climate change. At the same time floating architecture is the best model to offer the new spatial experience through water-friendly environment. Domestic floating architecture is still on the early stage compared to Europe which has several companies specialized in designing and building floating architecture. Floating architecture is divided into 8 types according to its criteria such as program, form, scale, level, location, access, mobility and energy. The following are design characteristics of floating architecture : (1) composed of 2 stories, (2) having large deck, (3) designing rectangular plan and balanced mass, (4) maximizing view, (5) having water-friendly space, (6) multi-using space and minimizing surface, (7) planning section to control light reflecting from the water, (8) modular and unit system.

• Applied Biological Chemistry
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• v.39 no.5
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• pp.379-383
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• 1996

The ultrastructure of the compound starch granules and the protein bodies of Odaebyeo rice of early matured variety were examined by light microscope and electron microscope. The endosperm cell appealed rectangular or octangular shape on the cross section. The thickness of cell wall containing of membraneous materials was about $0.5\;{\mu}m$ in diameter. The starch cell was filled compactly with globular or oval shaped compound starch granules with the size of $20{\sim}25\;{\mu}m$ in diameter. The compound starch granules were consisted of central core starch granule and concentrical $2{\sim}3$ layers of starch granules. The average thickness of the starch granules were about $5\;{\mu}m$. Most protein bodies were found in the aleurone layer The globular protin bodies were scattered near the compound starch granules and $2.5{\sim}3\;{\mu}m$ in diameter. The protein bodies composed of central electron dense materials and peripheral electron loose materials in limiting membrane.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.539-548
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• 2007

This paper deals with flexural-torsional free vibrations of the circular strip foundation with the variable breadth on Pasternak soil. The cross-section of the strip foundation is chosen as the rectangular one with the constant thickness and variable breadth, which is symmetrical about the mid-arc. Also, the foundation that supports the circular strip is modeled as the Pasternak soil with the shear layer. Ordinary differential equations accompanying the boundary conditions are derived. In the governing equations, the transverse, rotatory and torsional inertias are included. These equations are solved numerically and four lowest frequencies are obtained. In the numerical results, the effects of foundation parameters on frequencies are extensively investigated. It is expected that the theories and numerical results of this study can be used in the dynamic design of strip foundations.