• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.137-144
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• 2005

A direct shear test is classified roughly by one side simple shear test of confining horizontal displacement type and torsional shear test of non-confining one. Direct shear test that has been widely used so far has some problems with test apparatus, testing and the analysis, and in particular that its strength value is everestimated in sandy soils. Also, progressive failure of shearing process happens from shear apparatus restriction and because the shear strain and shear stress are erratic in specimen, we can not define the shear strain value. In the meantime, a simple shear test having advantage of direct shear test is an ideal test method that can get stress-strain relation on shear because it can deliver constant shearing deformation to specimen. However, simple shear test cannot be used practically, because its structure makes tester manufacturing difficult. This paper described a on outline of test apparatus, improvement of test method, and constant pressure test results based on the obtained from improved direct shear apparatus and the standardization of JGS soil testing method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.442-445
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• 1995

This paper presents the position tracking control of a laser scanning mirror system in which piezoelectic actuator is incorporated. Using the shear mode of the piezoelectric actuator,angular oscillation of a laser scanning mirror is derived. Torsion bar is rhen designed and attached to the piezoelctric actuator in order to magnify the amplitude generated by the actuator. Finite element modeling and analysis are essntial for designing the piezoelectic actuator. The torsional resonance mode of the piezoelectric actuator is found from the model analysis of the actuator and the mechanical shear is matched with the driving frequency. Transfer function between the electrical excitation and the mechanical shear deformation at resonance frequency is found form the response of the actuator calculated by the finite element analysis and the governing equation of the system is derived from d'Alembert's principle. Tracking control performance for desired trajectory which is, in fact, sinusoidal curve is presented in order to demonstrate the validity of the proposed system.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.577-585
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• 2017

To study the mechanical performances of prestressed steel-concrete composite box beam under combination of bending-shear-torsion, nine composite beams with different ratio of torsion to bending were designed. Torsion was applied to the free end of the beam with jacks controlled accurately with peripherals, as well as concentrated force on the mid-span with jacks. Based on experimental data and relative theories, mechanical properties of composite beams were analyzed, including torsional angle, deformation and failure patterns. The results showed that under certain ratio of torsion to bending, cracking and ultimate torsion increased and reached to its maximum at the ratio of 2. Three phases of process is also discussed, as well as the conditions of each failure mode.

• Structural Engineering and Mechanics
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• v.13 no.3
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• pp.277-298
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• 2002

In this study, free vibration analysis of Reissner plates on Pasternak foundation is carried out by mixed finite element method based on the G$\hat{a}$teaux differential. New boundary conditions are established for plates on Pasternak foundation. This method is developed and applied to numerous problems by Ak$\ddot{o}$z and his co-workers. In dynamic analysis, the problem reduces to the solution of a standard eigenvalue problem and the mixed element is based upon a consistent mass matrix formulation. The element has four nodes and bending and torsional moments, transverse shear forces, rotations and displacements are the basic unknowns. The element performance is assessed by comparison with numerical examples known from literature. Validity limits of Kirchhoff plate theory is tested by dynamic analysis. Shear locking effects are tested as far as $h/2a=10^{-6}$ and it is observed that REC32 is free from shear locking.

• Structural Engineering and Mechanics
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• v.21 no.5
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• pp.591-620
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• 2005

A general analytical model for thin-walled composite beams with an arbitrary open/(or/and) closed cross section and arbitrary laminate stacking sequence i.e., symmetric, anti-symmetric as well as un-symmetric with respect to the mid plane of the laminate, is developed in the first paper. All the mechanical properties, mechanical centre of gravity and mechanical shear centre of the cross section are defined in the function of the geometry and the material properties of the section. A program "fungen" and "clprop" are developed in Fortran to compute all the mechanical properties and tested for various isotropic sections first and compared with the available results. The locations of mechanical centre of gravity and mechanical shear centre are given with respect to the fibre angle variation in composite beams. Variations of bending and torsional stiffness are shown to vary with respect to the fibre angle orientations.

• Composites Research
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• v.13 no.5
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• pp.37-43
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• 2000

In this paper an analytical investigation pertaining to the elastic shear buckling behavior of transversely stiffened orthotropic plate under in-plane shear forces is presented. All edges of plate are assumed to be simply supported and the evenly placed stiffener is considered as a beam element neglecting its torsional rigidity. For the solution of the problem Rayleigh-Ritz method is employed. Using the derived equation, the limit of buckling stress of transversely stiffened plate is suggested as a graphical form. Based on the limit of buckling stress of stiffened plate, graphical form of results for finding the required stiffener rigidity is presented when one and two stiffeners are located, respectively.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1465-1486
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• 2016

Conventional plate I-girders are sensitive to local buckling of the web when they are subjected mainly to shear action because the slenderness of the web in out-of-plane direction is much bigger. The local buckling of the web can also cause the distorsion of the plate flange under compression as a thin-walled plate has very low torsional stiffness due to its open section. A new I-girder consisted of corrugated web, a concrete-filled rectangular tubular flange under compression and a plate flange under tension is presented to improve its resistance to local buckling of the web and distorsion of the flat plate flange under compression. Experimental tests on a conventional plate I-girder and a new presented I-girder are conducted to study the failure process and the failure mechanisms of the two specimens. Strain developments at some critical positions, load-lateral displacement curves, and load-deflection curves of the two specimens have all be measured and analyzed. Based on these results, the failure mechanisms of the two kinds of I-girders are discussed.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.414-417
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• 2001

Experimentally, the aligned direction of AFLCs in electro-optic cells having both the substrates rubbed along the same direction is skewed by a few degrees from the rebbing direction. To explain why, we proposed "Torsional Rigid Body Model" and interpreted their skewing angle as the action of short pitch with the large shear stress. That is, the azimuthal an anchoring strength (about 35 dyn/cm) in the cell is much larger than the maximum shear stress (about 10$^{-6}$ dyn/cm) for the original pitch and so forbids the optic axis to skew. On the side hand, the strength is smaller than the maximum shear stress (about 42 dyn/cm) for short pitch and then allows the optic axis to skew.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.480-485
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• 2004

The applications of composite materials have increased over the past few decades in a variety of structures that require high ratio of stiffness and strength to weight ratios. Recently the thick open section composite beams are used extensively as load carrying members and stiffeners of structural elements. However, most of studies on thick composite beams are limited only to closed section beams. In this study, an open cross-section thick-walled composite beam model which includes coupled stiffness, transverse shear, and warping effects is suggested and the deflections associated with the thick-walled composite beams and thin-walled composite beams are obtained and compared with the finite element analysis results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2322-2330
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• 1994

The torsion problem in a cylindrical rod is usually formulated in terms of either the warping function or the Prandtl stress function. In a rod whose cross-section is bounded by circles and rectangles, we develop an analytic solution approach based on the warping function, which satisfies Laplace's equation. The present formulation employs polynomials and The Fourier series-type solutions, both of which satisfy exactly the governing differential equation. Using the present method, the maximum shear stress and torsional rigidity are efficiently and accurately calculated and the present results are compared with those by other methods. The specific numerical examples include the case with eccentric holes which was investigated earlier. The finite element results are also compared with the present results.