• International Journal of Concrete Structures and Materials
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• v.5 no.2
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• pp.77-85
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• 2011

The use of headed bars as opposed to standard 90- or 180-degree hooked bars in beam ends, beam-column joints or other steel congested areas for anchorage and bond has become more favorable due to the fact that steel congestion is often created by large bend diameters or crossties. This research mainly focuses on evaluating the code provisions regarding the use of headed bars. Nine simply supported rectangular concrete beams with headed longitudinal reinforcement were tested under a four-point monotonic loading system. The design clear spacing, which varies from 1.5 to 4.25 times the bar diameter, was the only parameter for the experimental investigation. The test results showed that the closely-spaced headed bars were capable of developing to full yield strength without any severe brittle concrete breakout cone or pullout failure. Bond along the bar was not sufficient due to the early loss of concrete integrity. However, the headed bars were effective for anchorage with no excessive moment capacity reduction. This implies that the clear spacing of about 2 times the bar diameter for headed bars may be reasonable to ensure the development of specified yield strength of headed bars and corresponding member design strength.

• Advances in aircraft and spacecraft science
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• v.2 no.1
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• pp.45-56
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• 2015

The attitude aerodynamic control is an important subject in the design of an aerospace plane. Usually, at high altitudes, this control is fulfilled by thrusters so that the implementation of an aerodynamic control of the vehicle has the advantage of reducing the amount of thrusters fuel to be loaded on board. In the present paper, the efficiency of a wing-flap has been evaluated considering a NACA 0010 airfoil with a trailing edge flap of length equal to 35% of the chord. Computational tests have been carried out in hypersonic, rarefied flow by a direct simulation Monte Carlo code at the altitudes of 65 and 85 km, in the range of angle of attack 0-40 deg. and with flap deflection equal to 0, 15 and 30 deg.. Effects of the flap deflection have been quantified by the variations of the aerodynamic force and of the longitudinal moment. The shock wave-boundary layer interaction and the shock wave-shock wave interaction have been also considered. A possible interaction of the leading edge shock wave and of the shock wave arising from the vertex of the convex corner, produced on the lower surface of the airfoil when the flap is deflected, generates a shock wave whose intensity is stronger than those of the two interacting shock waves. This produces a consistent increment of pressure and heat flux on the lower surface of the flap, where a thermal protection system is required.

• Steel and Composite Structures
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• v.9 no.5
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• pp.397-418
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• 2009

Eight panel specimens were tested in one-way bending to study the behaviour and capacity of composite slab joists consisting of cold-formed steel C-sections and concrete. Various shear transfer mechanisms were implemented on the C-section flange embedded in the concrete to provide the longitudinal shear resistance. Results showed that all specimens reached serviceability limit state while in elastic range and failure was ductile. Shear transfer achieved for all specimens ranged from 42 to 99% of a full transfer while specimens employed with shear transfer enhancements showed a greater percentage and therefore a higher strength compared with those relying only on surface bond to resist shear. The implementation of pre-drilled holes on the embedded flange of the steel C-section was shown to be most effective. The correlation study between the push-out and panel specimens indicated that the calculated moment capacity based on shear transfer resistance obtained from push-out tests was, on average, 10% lower than the experimental ultimate capacity of the panel specimen.

• Computers and Concrete
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• v.6 no.5
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• pp.357-376
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• 2009

In the design of concrete columns, it is important to provide some nominal flexural ductility even for structures not subjected to earthquake attack. Currently, the nominal flexural ductility is provided by imposing empirical deemed-to-satisfy rules, which limit the minimum size and maximum spacing of the confining reinforcement. However, these existing empirical rules have the major shortcoming that the actual level of flexural ductility provided is not consistent, being generally lower at higher concrete strength or higher axial load level. Hence, for high-strength concrete columns subjected to high axial loads, these existing rules are unsafe. Herein, the combined effects of concrete strength, axial load level, confining pressure and longitudinal steel ratio on the flexural ductility are evaluated using nonlinear moment-curvature analysis. Based on the numerical results, a new design method that provides a consistent level of nominal flexural ductility by imposing an upper limit to the axial load level or a lower limit to the confining pressure is developed. Lastly, two formulas and one design chart for direct evaluation of the maximum axial load level and minimum confining pressure are produced.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.391-401
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• 2018

Locally available Stainless Steel Wire Mesh (SSWM) bonded on a concrete surface with an epoxy resin is explored as an alternative method for the torsional strengthening of Reinforced Concrete (RC) beam in the present study. An experiment is conducted to understand the behavior of RC beams strengthened with a different configuration of SSWM wrapping subjected to pure torsion. The experimental investigation comprises of testing fourteen RC beams with cross section of $150mm{\times}150mm$ and length 1300 mm. The beams are reinforced with 4-10 mm diameter longitudinal bars and 2 leg-8 mm diameter stirrups at 150 mm c/c. Two beams without SSWM strengthening are used as control specimens and twelve beams are externally strengthened by six different SSWM wrapping configurations. The torsional moment and twist at first crack and at an ultimate stage as well as torque-twist behavior of SSWM strengthened specimens are compared with control specimens. Also the failure modes of the beams are observed. The rectangular beams strengthened with corner and diagonal strip wrapping configuration exhibited better enhancement in torsional capacity compared to other wrapping configurations. The numerical simulation of SSWM strengthened RC beam under pure torsion is carried out using finite element based software ABAQUS. Results of nonlinear finite element analysis are found in good agreement with experimental results.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.416-419
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• 2000

A narrow slot in the broad wall of a rectangular waveguide is analysed using a Spatial Network Method[1] which takes account of the waveguide wall thickness. In essence, SNM is used to solve arbitrary shape and materials constant, derived from maxwell's equations to find the tangential electric fields on the upper and lower surfaces of the slot. In this paper, applying to the offset and length[2] which yield a zero equivalent shunt susceptance, analysing single and 4 array slot antenna. The current of the transient analysis shows each the times. Analysed result of SNM is verified by the method of moment and HFSS.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.5
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• pp.197-207
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• 2013

The seismic performance of school buildings has been a matter of common interest socially and academically. The structural system of the school buildings is representative of the domestic low-rise reinforced concrete moment resisting frames, which apply extensively infills in their masonry walls. The masonry infilled walls are divided into full masonry infill in the transverse direction and partial masonry infill in the longitudinal direction. The masonry infilled walls are usually not included in structural analysis during the design process, but affect significantly the seismic performance because they behave with surrounding frames simultaneously during earthquakes. Many researchers have studied the effect of the masonry infilled walls, but several issues have been missed such as the increase of asymmetry by adding the full masonry infill, the size of the mean strength of the full masonry infill, and short column effect by the partial masonry infill. The issues were analytically investigated and the results showed that they should be checked at least by nonlinear pushover analysis in the seismic performance evaluation process. The results also confirm the weakness of the guideline of Korean Educational Development Institute where the seismic performance is basically assessed without structural analysis.

• Structural Engineering and Mechanics
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• v.28 no.4
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• pp.387-410
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• 2008

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.97-100
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• 2008

Various flyers in nature have attracted great interests with a recent need for developing versatile and small-size flight vehicles. In the present study, we focus on the flying fish which has been observed to glide a long distance just above a seawater surface. Since previous studies have depended on the field observation or measurement of the physical parameters only, quantitative data of the flying fish flight has not been provided so far. Therefore, we evaluate the wing performance of the flying fish in gliding flight by directly measuring the lift, drag and pitching moment on real flying fish models (Cypselurus hiraii) in a wind tunnel. In addition, we investigate the roles of wing morphology like the enlarged pectoral and pelvic fins, and lateral dihedral angle of pectoral fins. With both the pectoral and pelvic fins spread, the lift-to-drag ratio is larger and the longitudinal static stability is enhanced than those with the pelvic fins folded. From the glide polar, we find that the wing performance of flying fish is equivalent to those of medium-size birds like the petrel, hawk and wood duck. Finally, we examine the effect of water surface underneath the flying fish and find that the water surface reduces the drag and increases the lift-to-drag ratio.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.19 no.2
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• pp.117-124
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• 1983

In rough seas, actual behaviours of a ship may not be estimated by the linear strip theory, because of Nonlinearities due to the hull shape, bottom slamming and bottom and/or bow-flare slamming. In case of slamming, impulsive hydrodynamic pressure occurs on the fore body surface of the ship, resulting hull vibration called whipping, by which the ship may suffer from serious structural damages and the impact pressure, depends critically on the relative velocity at re-entry. In this paper, the Time history of impact froce at each station, the longitudinal distribution of impact force at critical time, the Time history of acceleration at F.P. and the Time history of Bending moment at midship are illustrated. That is, authors analyzed Dynamic response of container ship to be subjected slamming impact force.