• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.409-415
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• 2010

A finite element model for punching shear of flat plate structures is presented. A parametric study also has been conducted to verification of influence of several parameters in terms of the flexural reinforcement ratio, slab thickness. Reisnner-Mindlin assumptions are adopted to consider of shear deformation. Layered shell element is considered for the material non-linearities. The finite element model of this study was verified comparing with existing experimental results. The model is able to predict the capacity of the flat plate structures. The punching shear of flat plate structures varied depending on the flexural reinforcement ratio, slab thickness.

• Smart Structures and Systems
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• v.22 no.3
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• pp.277-290
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• 2018

In this paper, wavelet finite element model (WFEM) updating technique is employed to detect sub-element damage in thin plate structures progressively. The procedure of WFEM-based detection method, which can detect sub-element damage gradually, is established. This method involves the optimization of an objective function that combines frequencies and modal assurance criteria (MAC). During the damage detection process, the scales of wavelet elements in the concerned regions are adaptively enhanced or reduced to remain compatible with the gradually identified damage scenarios, while the modal properties from the tests remains the same, i.e., no measurement point replacement or addition are needed. Numerical and experimental examples were conducted to examine the effectiveness of the proposed method. A scanning Doppler laser vibrometer system was employed to measure the plate mode shapes in the experimental study. The results indicate that the proposed method can detect structural damage with satisfactory accuracy by using minimal degrees-of-freedoms (DOFs) in the model and minimal updating parameters in optimization.

• Steel and Composite Structures
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• v.6 no.6
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• pp.531-555
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• 2006

H-shaped welded steel column members are fabricated by welding together pre-cut flanges and the web. Modern fabricators are increasingly using plasma-cutting technique instead of traditional flame cutting. Different fabrication techniques result in different degrees of geometric imperfections and residual stresses, which can have considerable influence on the strength of steel columns. This paper presents the experimental investigation based temperature profiles, geometric imperfections, and built-in residual stresses in plasma cut-welded H-shaped steel column members and in similar flame cut-welded H-shaped steel columns. Temperature measurements were taken during and immediately after the cutting operations and the welding operations. The geometric imperfections were established at closely spaced grid locations on the original plates, after cutting plates into plate strips, and after welding plate strips into columns. Geometric imperfections associated with plasma cut element and members were found to be less than those of the corresponding elements and members made by flame cutting. The "Method of Section" technique was used to establish the residual stresses in the plate, plate strip, and in the welded columns. Higher residual stress values were observed in flame cut-welded columns. Models for idealized residual stress distributions for plasma cut and flame cut welded sections have been proposed.

• Structural Engineering and Mechanics
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• v.73 no.4
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• pp.455-462
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• 2020

The hybrid method using the extended finite element method (XFEM) and the forward Euler approach is widely employed to predict the fatigue life of plate structures. Due to the accuracy of the forward Euler approach is determined by a small step size, the performance of fatigue life prediction of the hybrid method is not agreeable. Instead the forward Euler approach, a prediction method using midpoint method and support vector regression (SVR) is presented to evaluate the stress intensity factors (SIFs) and the fatigue life. Firstly, the XFEM is employed to calculate the SIFs with given crack sizes. Then use the history of SIFs as a function of either number of fatigue life cycles or crack sizes within the current cycle to build a prediction model. Finally, according to the prediction model predict the SIFs at different crack sizes or different cycles. Three numerical cases composed by a homogeneous plate with edge crack, a composite plate with edge crack and center crack are introduced to verify the performance of the proposed method. The results show that the proposed method enables large step sizes without sacrificing accuracy. The method is expected to predict the fatigue life of complex structures.

• Journal of Ocean Engineering and Technology
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• v.33 no.2
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• pp.153-160
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• 2019

Welding often results in welding distortion during the assembly process. The welding distortion of thin-plate structures such as the living quarters of ships and offshore installations is a more significant problem than in the case of thick-plate structures. Pre-stressing/heating and fairing, which are additional works to mitigate and control welding distortion, are inevitable, and the construction planning is accordingly delayed. In order to prevent welding distortion and minimize the additional work during the assembly process, increasing the plate thickness and/or the number of stiffeners may be a simple solution, but it may give rise to problems related to cost and weight. In this study, the welding distortion control effect of the type of stiffeners on the door openings of various living quarter structures was investigated using an experimental method and a finite element method. The results showed the feasibility of mitigating and controlling the welding distortion, and the optimum selection of the type of stiffeners was confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.753-761
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• 1998

The determination of sound pressure radiated from periodic plate structures is fundamental in the estimation of noise level in aircraft fuselages or ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model is developed for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal unsymmetrical beams subjected to a sinusoidally time varying point load. The plate is assumed to be infinite in extent, and the beams are considered to exert both line force and moment reactions on it. Using this theoretical model, the sound pressure levels on axis in a semi-infinited fluid (water) bounded by the plate were calculated using three numerical tools such as the Gauss-Jordan method, the LU decomposition method and the IMSL numberial package. Especially, the variation in the sound pressure levels and their modes were investigated according to the change in frequency, bay spacing and bay distance.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.703-710
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• 2012

A structural health monitoring technique for locating impact position in a composite plate is presented in this paper. The method employs a single sensor and spatial focusing properties of time reversal(TR) and inverse filtering(IF). We first examine the spatial focusing efficiency of both approaches at the impact position and its surroundings through impact experiments. The imaging results of impact localization show that the impact location can be accurately estimated in any position of the plate. Compared to existing techniques for locating impact or acoustic emission source, the proposed method has the benefits of using a single sensor and not requiring knowledge of anisotropic material properties and geometry of structures. Furthermore, it does not depend on a particular mode of dispersive Lamb waves that is frequently used in other ultrasonic testing of plate-like structures.

• Journal of Korean Association for Spatial Structures
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• v.1 no.1 s.1
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• pp.109-115
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• 2001

Composite materials also known as fiber reinforced plastics have been developed and used in many engineering applications due to their outstanding mechanical properties. Laminated plates as structural components that are made of in composite material are widely used. Therefore, nonlinear response of laminated composite plates modeled with finite elements and excited by stochastic loading is studied. The classical laminated plate theory is used to account for the variation of strains through the thickness for modeling laminated thin plates. Approximate nonlinear random vibration analysis is performed using the method of equivalent linearization to account for material non-linearity.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.121-128
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• 1997

The Boundary Element Method(BEM) has many advantages. Nevertheless the applicability of BEM to structural analysis is seemed to be behind the other methods. This study presents the application of the BEM for analysis of assembled plate structures which is light weight and has a great loading capacity. Firstly, we formulate the boundary integral equation of the single plate, using the biharmonic fundamental solution for plate bending and internal force problems. Nextly, each plates are assembled on 3-dimensional space. In this process, the boundary conditions on assemble line are used. To verify the objectivity and universal validity of analysis by BEM, the results of BEM was compared to that of SAP90 by using FEM.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.435-447
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• 2019

Energy Flow Finite Element Analysis (EFFEA) is a promising tool for predicting dynamic energetics of complicated structures at high frequencies. In this paper, the Energy Flow Finite Element (EFFE) formulation of complicated Mindlin plates was newly developed to improve the accuracy of prediction of the dynamic characteristics in the high frequency. Wave transmission analysis was performed for all waves in complicated Mindlin plates. Advanced Energy Flow Analysis System (AEFAS), an exclusive EFFEA software, was implemented using $MATLAB^{(R)}$. To verify the general power transfer relationship derived, wave transmission analysis of coupled semi-infinite Mindlin plates was performed. For numerical verification of EFFE formulation derived and EFFEA software developed, numerical analyses were performed for various cases where coupled Mindlin plates were excited by a harmonic point force. Energy flow finite element solutions for coupled Mindlin plates were compared with the energy flow solutions in the various conditions.