• Journal of Ocean Engineering and Technology
• /
• v.8 no.2
• /
• pp.151-156
• /
• 1994

The equations of motion of a submarine pipeline with the internal flowing fluid and subject to hydrodynamic loadings are derived by using Hamilton's principle. Coupling between the bending and the longitudinal extension due to axial load and thermal expansion are considered. Coupling between the twisting and extension are not considered. The equations of motion are well agreed with the results which are derived by the vector method.

• Geotechnical Engineering
• /
• v.8 no.1
• /
• pp.19-28
• /
• 1992

Recently, testing equipment which can run resonant column test altogether with the torsional shear test at the very highly controlled condition was developed at the University of Texas at Austin(U.S.A). With this equipment, the effects of high amplitude pre-straining vibrations on the dynamic properties of clean sands were studied. Tests showed the following results. Low amplitude shear modulus was gradually increased with little void ratio change as the number of high amplitude vibration cycles increased. Variation of volumetric strain with confining pressure for the pre -strained specimen under vibration was smaller than that of fresh specimen. Also the slope of the diagram for shear modulus and confining pressure relationship of the prestrained specimen was smaller than that of fresh specimens. These results agreed well with the analytical results.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.13 no.1
• /
• pp.63-69
• /
• 2003

The ordinary differential equations governing free vibrations of elastic horizontally curved beams are derived, in which the effects of rotatory inertia and shear deformation as well as the effects of both vertical and torsional inertias are included. Frequencies and mode shapes are computed numerically for parabolic curved beams with the hinged-hinged, hinged-clamped and clamped-clamped ends. Comparisons of natural frequencies between this study and ADINA are made to validate the theories and numerical methods developed herein. The lowest three natural frequency parameters are reported. with and without the effects of rotatory inertia and shear deformation. as functions of the three non-dimensional system parameters: the horizontal rise to span length ratio. the slenderness ratio and the stiffness parameter.

• International Journal of Highway Engineering
• /
• v.10 no.2
• /
• pp.81-89
• /
• 2008

Shear test procedure for concrete-dowel interaction was proposed along with determination of dowel support reaction factor or shear spring stiffness constant using the spreadsheet example. For this task, three AASHTO-type standard specimens were prepared to simulate behavior of the jointed concrete pavement. A side support system was adopted to minimize twisting of the test specimen which had been observed in a preliminary test. A typical elastic behavior of the dowel-concrete interaction was observed from several test loops of loading, unloading and reloading procedures. However load versus slab displacement represents to be nonlinear. Test results show that the dowel support reaction factor ranges from 550-880 GN/m3, which is 1.4-2.2 times greater than 407GN/m3 proposed by Yoder and Witczak. This is because less torsional distraction was occurred with the help of a side support system adopted in this experiment. The dowel support reaction factor or shear spring stiffness constant obtained from the procedures proposed in this paper may be used as a reference data for the structural analysis of jointed concrete pavement.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.35-42
• /
• 2020

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30°, the shear force of the column increased less than that of 60°, and the lateral displacement of column was decreased in the order of □, ◯ and Ｈ in cross-section.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.8
• /
• pp.1083-1089
• /
• 2010

Shape memory alloys (SMAs) are smart materials. The unique characteristics of SMAs enable the production of large force and displacement. Hence, SMAs can be used in many applications such as in actuators and active structural acoustic controllers; the SMAs can also be used for dynamic tuning and shape control. A SMA torque tube actuator consisting of SMA tubes and superelastic springs is proposed, and the behaviors of the actuator are investigated. From the results of heat transfer analysis, it is proved that the SMA torque tube actuator with both resistive heating of SMA itself and a separate conventional heating rod in the tube core has good performance. The behavior of an actuator system was analyzed by performing a contact analysis, and the twisting motion was noticed when checking the actuation. 3D SMA nonlinear constitutive equations were formulated numerically and implemented by performing a nonlinear analysis by using Abaqus UMAT.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.3
• /
• pp.249-257
• /
• 2013

This study newly presents a synthetic phase tuning technique to suppress the unwanted torsional mode while enhancing the desired torsional mode in a pipe. Specifically, we aim at the enhancement of the first torsional mode and the suppression of the undesired, second torsional mode. Earlier efforts were to enhance the desired wave mode only in the hope that the enhancement results in the suppression of the unwanted wave mode. Unlike these efforts, the suggested technique makes the complete cancellation of the unwanted wave mode but it is shown to enhance the desired first mode for torsional wave problems. In the present study, the synthetic phase tuning is developed for the cancellation of the unwanted wave mode, meaning that the number of necessary experimental equipments is reduced. Simulation and experiment were carried out to check the effectiveness of the proposed method. As an application of the suggested technique, we investigated the reflection and mode conversion characteristics of the first torsional mode according to the step thickness variation in a stepped pipe.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.2
• /
• pp.139-146
• /
• 2009

In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. The piezoceramic shear actuation mechanism along with elastic couplings of composite blades is used for vibration reduction. The rotor blades are modeled as composite box-beams with actuator layers bonded on the outer surfaces of the thin-walled section. The governing equations of motion for helicopter blades are obtained using Hamilton's principle. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. Various rotor configurations with different elastic couplings with appropriate actuator placement are used to investigate the hub vibration characteristics. Numerical results show that a substantial reduction of $N_b$/rev hub vibration can be achieved using the optimal control algorithm.

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

• Journal of Korean Society of Steel Construction
• /
• v.23 no.2
• /
• pp.249-259
• /
• 2011

In this study, the distortional behaviors of tub-section steel girders subjected to torsional loading were analyzed, and predictor equations were developed for estimating the member forces induced in the internal bracing system installed in the steel tub girders. Torsional loadings originated either by eccentric vertical loading or girder curvature were decomposed into the pure torsional force component that does not affect the distortional box deformation, and into the distortional force component that directly induces box distortion. The axial member forces induced in the internal cross frames were formulated as a function of the magnitude of torsional loading through the analytical investigation of the interactions between the distortional force component and internal cross frames. To verify the proposed equations, three-dimensional finite element analysis (3D FEA) was conducted for the straight simple-span girder and the three-span continuous girder samples. Very good agreement was found between the member forces from the FEA and the proposed equations.