• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
• /
• v.4 no.1
• /
• pp.31-37
• /
• 2001

In this paper, an integrated damage identification system (IDIS) is proposed to locate and size damage in real structures. The application of the IDIS to real structures includes the measurement of modal responses, the construction of damage-detection models, and the implementation of measurements and models into the damage-detection process. Firstly, the theory of the damage identification method is outlined. Secondly, the schematic and each component of the IDIS are described. Finally, the practicality of the IDIS is verified from experiments on two different bridge-models, a model plate-grider and a model truss.

• Coupled systems mechanics
• /
• v.9 no.1
• /
• pp.29-46
• /
• 2020

In this paper we deal with stability problems of any complex structure that can be modeled by beam and shell finite elements. We use for illustration the steel plate girders, which are used in bridge construction, and in industrial halls or building construction. Long spans, slender cross sections exposed to heavy loads, are all critical design points engineers must take into account. Knowing the critical load that will cause lateral torsional buckling of the girder, or load that can lead to web buckling, as an important scenario to consider in a design process.Many of such problem, including lateral torsional buckling with influence of lateral supports and their spacing on critical load can be solved by the proposed method. An illustrative study of web buckling also includes effects of position and spacing of transverse and longitudinal web stiffeners, where stiffeners can be modelled optionally using shell or frame elements.

• Journal of Welding and Joining
• /
• v.23 no.4
• /
• pp.48-52
• /
• 2005

To estimate welding deformation for large steel structures, either experiment result with small specimen or analysis result of FEM with small numerical model is used. Consequently, it is important to decide the welding length of specimen and numerical model not to have an effect on welding deformation for accurate estimation of whole welding deformation. This study experimentally clarifies the effect of welding length on angular distortion due to welding by varying welding length of specimens, but fixing width and thickness of specimens on V-groove butt welding, fillet welding and bead on plate welding. As a resell the critical welding length on fillet welding and on bead on plate welding is over 500mm and on V-groove butt welding is over 1,000mm.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.1
• /
• pp.157-173
• /
• 2015

In the present study, the existing equivalent stain method is improved to make up for its weaknesses. The improved inherent strain model is built considering more sophisticated three dimensional constraints which are embodied by six cubic elements attached on three sides of a core cubic element. From a few case studies, it is found that the inherent strain is mainly affected by the changes in restraints induced by changes of temperature-dependent material properties of the restraining elements. On the other hand, the degree of restraints is identified to be little influential to the inherent strain. Thus, the effect of temperature gradients over plate thickness and plate transverse direction normal to welding is reflected in the calculation of the inherent strain chart. The welding deformation can be calculated by an elastic FE analysis using the inherent strain values taken from the inherent strain chart.

• Proceedings of the KIEE Conference
• /
• 1998.07g
• /
• pp.2524-2526
• /
• 1998

In this paper, the residual stress and young's modulus of the p+ thin film have been estimated by using the electrostatic resonators. The electrostatic plate resonator with four corrugated bridges and another with four flat ones have been fabricated. The deflection of the plate has been calculated under the induced tension and the residual stress and compared with the dynamic test results. When the young's modulus of the p+ silicon is 125 GPa. The estimated residual stresses of the flat and the corrugated bridges are about 15 MPa and less than 5 MPa, respectively. It has been confirmed that the corrugated structure releases the residual tensile stress resulted from the heavy boron diffusion process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.377-380
• /
• 2005

Damping materials encompass a broad range of materials, including, but not limits to, pressure sensitive adhesives, epoxies, rubbers, foams, thermoplastics, enamels and mastics. Their common characteristic is that their modulus is represented by a complex quantity, possessing both a stored and dissipative energy component. Loss factor of damping material analyzed more than 2 times than rubber to 1.5 $\sim$ 2.3, could know that Damping layer has excellent attenuation performance in side of vibration reduction. Measurements of vibration using accelerometers by adhesion of Damping layer, square Plate by Separation of Damping layer is less binding of Damping layer, analyzed low loss factor and Natural Frequency by free Vibration of Square Plate.

• Journal of Welding and Joining
• /
• v.30 no.6
• /
• pp.36-41
• /
• 2012

General condensers consist of many tubes supported by tube sheets and support plates to prevent the deflection of the condenser tubes. When a fluid at high pressure and temperature runs over the tubes for the purpose of transferring heat from one medium to another, the tubes vibrate and their surface comes into contact with the support plates. This vibration causes damage to the tubes, such as cracks and wear. We propose an ultrasonic guided wave technique to detect the above problems in the support plate region. In the proposed method, the ultrasonic guided wave mode, L(0,1), is excited using an internal transducer probe from a single position at the end of the tube. In this paper, we present a preliminary experimental verification using a super stainless tube and show that the defects can be discriminated from the support signals in the support region.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.2
• /
• pp.117-126
• /
• 2016

In this paper, a numerical procedure for the natural vibration analysis of plates with openings and carlings based on the assumed mode method is extended to assess their forced response. Firstly, natural response of plates with openings and carlings is calculated from the eigenvalue equation derived by using Lagrange's equation of motion. Secondly, the mode superposition method is applied to determine frequency response. Mindlin theory is adopted for plate modelling and the effect of openings is taken into account by subtracting their potential and kinetic energies from the corresponding plate energies. Natural and frequency response of plates with openings and carlings subjected to point excitation force and enforced acceleration at boundaries, respectively, is analysed by using developed in-house code. For the validation of the developed method and the code, extensive numerical results, related to plates with different opening shape, carlings and boundary conditions, are compared with numerical data from the relevant literature and with finite element solutions obtained by general finite element tool.

• Journal of Ocean Engineering and Technology
• /
• v.34 no.1
• /
• pp.37-45
• /
• 2020

Unstiffened and stiffened cylindrically curved plates are often used in ship structures. For example, they can be found on a deck with a camber, a side shell at the fore and aft parts, and the circular bilge part of a ship structure. It is believed that such cylindrically curved plates can be fundamentally modelled using a portion of a circular cylinder. From estimations using cylindrically curved plate models, it is known that the curvature generally increases the buckling strength compared to a flat plate under axial compression. The existence of curvature is also expected to increase both the ultimate and buckling strengths. In the present study, a series of finite element analyses were conducted on stiffened curved plates with several varying parameters such as the curvature, panel slenderness ratio, and web height and type of stiffener applied. The results of numerical calculations on stiffened and unstiffened curved plates were examined to clarify the influences of such parameters on the characteristics of their buckling/plastic collapse behavior and strength under an axial compression.

• Journal of Ship and Ocean Technology
• /
• v.10 no.3
• /
• pp.17-26
• /
• 2006

Spar platforms have been installed as a competitive alternative offshore production structure for deepwater oil field. Since the first spar platform was constructed, its configuration has evolved to the so-called the truss spar and then the cell spar. This paper describes the dynamic analysis and fatigue life assessment of steel catenary riser (SCR) connected to cell spar platform. Two different cell spar platforms are considered herein; the original cell spar and the modified one. The original cell spar was modified by introducing an additional damping plate at its bottom in order to reduce wave-frequency motions. Firstly the wave-frequency motions of cell spar platforms are calculated based on the potential theory. Then, the dynamic responses of SCR induced by platform motions are computed. Finally the fatigue life of SCR is estimated by spectral method and the performance of two spar platforms are compared in terms of the fatigue life. Through the present study, it is found that the fatigue life of the modified cell spar increases only slightly.