• Journal of KSNVE
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• v.6 no.2
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• pp.147-161
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• 1996

The stress and vibration analysis of stiffened box structure is investigated by experiment and FEM analysis. The effects of stiffener number and box section shape on the structure response are presneted. The 1st natural frequency of stiffened folded byx structure with a stiffeners is 300 Hz. It is highter than that of stiffened rectangular box structure with 5 stiffeners, which is 251 Hz. Maximum deflection of folded box structure with thickness of 1 mm is lower than that of rectangular box structure with thickness of 1 or 2 mm. The natural frequencies of box structures are increeased with the number of stiffener, while the deflections are decreased with the number of box structures. When we compare between fundamental frequency (251 Hz) of stiffened (with 5 stiffeners) and one (137.64 Hz) of unstiffened rectangular box structure under clamped-clamped boundary condition, the ratio of frequency increase is 82%. The stiffened structures of 2 mm thickness can reduced to 120% of maximum deflection of 1 mm thickness rectangular box structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.833-839
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• 2003

The effects of stiffeners on the modal characteristics of rectangular plates are investigated. A modeling method for the modal analysis of rectangular plates with stiffeners is presented. A mass density Dirac's delta function is used to idealize the stiffeners mathematically. The equations of motion for the plates are derived and transformed into a dimensionless form. To confirm the accuracy of the method presented in this study, numerical result are obtained and compared to those of a commercial program. The mode shape variations due to some parameter variations are also exhibited.

• Earthquakes and Structures
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• v.27 no.3
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• pp.191-207
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• 2024

Due to the many advantages of concrete-filled double steel tube (CFDT) columns, they are highly recommended for use in heavy-load structures such as bridges, subway stations, and high-rise buildings. This study was carried out with the aim of numerically investigating and comparing the performance of CFDT columns under cyclic and seismic loads and providing innovative strengthening methods for CFDT columns. Hollow circular steel sections have been used for internal and external tubes. To make the circular CFDT columns stronger against seismic loads, stiffeners with different shapes (rectangular and T-shaped sheets) have been welded to the outside and inside tubes. The validated finite element (FE) model of the ABAQUS program is used to look into the behavior of CFDT columns numerically. Two frames of 10 and 20 floors with strengthened CFDT columns were modeled. The results showed that the use of stiffeners in the CFDT column has a significant effect on seismic performance, so that the maximum lateral load of the column is increased up to 32.74% under the effect of cyclic load. Also, the results revealed that the use of stiffeners in the columns of moderate and high-rise building frames causes a significant increase in the shear of the base and consequently the stiffness. Among the other important results that followed, it reduced the drift of floors and increased energy absorption.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.622-628
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• 2011

The purpose of this study was to analyze the vibro-acoustic characteristics of a stiffened rectangular plate at high frequencies. The stiffeners attached along the plate surface were assumed to have rotational and translational stiffness and inertia. The harmonic response of the stiffened plate were predicted and compared using the Rayleigh-Ritz method with two different trial functions - polynomial and beam functions. The variation of the spatially averaged mean square velocity and the modal characteristics with the number of stiffeners were obtained. The use of the beam function ensured fast convergence which was essential for analyzing the high frequency vibration responses. Using the calculated modal characteristics and the Rayleigh-integral, the radiated sound power was predicted, and the effects of stiffeners were investigated. The proposed model can be applied to study optimal layout of stiffeners for minimal noise generation of the stiffened structures.

• Structural Engineering and Mechanics
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• v.57 no.6
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• pp.1051-1064
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• 2016

Link-to-column connections in Eccentrically Braced Frames (EBFs) have critical role in their safety and seismic performance. Accordingly, in this study, contribution of supplemental stiffeners on hysteretic behavior of the link-to-column connection is investigated. Considered stiffeners are placed on both sides and parallel to the link web between the column face and the first stiffener of the link. Hysteretic behaviors of the link beams with supplemental stiffeners are numerically investigated using a pre-validated numerical model in ANSYS. It turned out that supplemental stiffeners can change energy dissipation mechanism of intermediate links from shear-flexure to shear. Both rectangular and trapezoidal supplemental stiffeners are studied. Moreover, optimal placement of the supplemental stiffeners is also investigated. Obtained results indicate a discrepancy of less than 9% in maximum link shear of the numerical and experimental specimens. This indicates that the numerical results are in good agreement with those obtained from the test. Trapezoidal supplemental stiffeners improve rotational capacity of the link. Moreover, use of two supplemental stiffeners at both ends of the link can more effectively improve hysteretic behavior of intermediate links. Supplemental stiffeners would also alleviate the imposed demands on the connections. This latter feature is more pronounced in the case of two supplemental stiffeners at both ends of the link.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.42-49
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• 2005

The vibration analysis of a rectangular plate with stiffeners is formulated by using the transfer stiffness coefficient method (TSCM). This method is based on the concept of the successive transmission of stiffness coefficients which are defined as the relationship between the force vector and the displacement vector at an arbitrary nodal line. In order to confirm the validity of the present method, bending vibration analysis for a rectangular plate with stiffener is carried out on a personal computer by using the present method and the finite element method (FEM). Through comparing computational results of the TSCM and the FEM, the effectivness of the TSCM from the viewpoint of computational cost, that is, computational time and storage is demonstrated.

• Steel and Composite Structures
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• v.44 no.4
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• pp.489-502
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• 2022

The stiffeners, also known as ribs, are utilized to increase the resistance of T-stubs. The author's previous studies showed that stiffeners can increase plastic capacity by an average of 1.71 times. A combined experimental and numerical study was undertaken to examine the effects of the stiffener configuration on the behavior of T-stubs. A total of 20 stiffened T-stubs where the shape and angle of stiffeners were considered as the main parameters were tested under monotonic loading. Rectangular, triangular and AISC types of stiffener were tested under monotonic loading. The experimental results indicated that when the height of the stiffener is equal to or higher than the length of the stiffener, the shape of the stiffener does not have an influence on the behavior. A numerical study using the finite element tool ABAQUS was carried out in order to further investigate the effects of the stiffener shapes. In this case, the height is considered less than the length of the stiffener. Moreover, the shape of the stiffeners was investigated with the different thicknesses of the stiffener. The simulation findings revealed that when the height of the stiffener is less than the length of the stiffener, the shape of the stiffener significantly affects the plastic capacity. Based on the numerical and experimental results, it is recommended to use the triangular shape of the stiffener when height is equal to or higher than the length of the stiffener while it is recommended to utilize the rectangular shape of the stiffener when height is less than the length of the stiffener.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.3
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• pp.350-357
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• 2012

The velocity response of stiffened rectangular plate under high velocity impact was studied. Numerical simulation was conducted on the stiffened plate with four stiffeners under various impact positions. Considered stiffener types were rib, I, hat and T stiffener. For the center impact position of I stiffened plate, the simulated residual velocity was 365.6 m/s with the initial projectile velocity 500 m/s. The reinforcing characteristic of I stiffened plate was excellent among four stiffeners.

• Computational Structural Engineering
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• v.10 no.1
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• pp.135-148
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• 1997

The main objective of this paper is to analyze the rectangular stiffened plates with two opposite ends elastically restrained and the others simply supported subjected to in-plane bending by Finite Element Method. Another objective is to develope Classical Method analyzing the unstiffened rectangular plates with the above boundary conditions. In order to validate finite element and classical methods, the buckling strengths of the rectangular plates with four simply supported ends, and with two simply supported and the others fixed ends by finite element method and classical method are compared with those of references. In finite element method, elastically restrained ends can be obtained as considering torsional and warping rigidities of end stiffeners. The buckling strengths of the rectangular plates with elastically restrained ends by finite element and classical methods are calculated and compared with each other. In case of stiffened plates, to validate finite element method, the buckling strengths of the rectangular stiffened plates with four simply supported ends, and with two simply supported and the others fixed ends are also compared with those of references. The buckling strengths of the rectangular stiffened plates with elastically restrained ends by finite element method are calculated as solving eigenvalue problems which are obtained as assembling rectangular plate elements and beam elements considered torsional and warping rigidities. The buckling strengths of rectangular stiffened plates according to various positions of rectangular intermediate stiffener, J and I/sub w/ of end stiffeners are also obtained, which are compared to determine the efficient position of intermediate stiffener.

• Composites Research
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• v.13 no.6
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• pp.9-22
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• 2000

The Rayleigh-Ritz procedure based on energy method is used to present analytically the natural frequencies and the critical buckling loads for four types of loading conditions: (1) uniaxial, (2) biaxial, (3) positive shear and (4) negative shear, of the rectangular, composite plates unidirectionally stiffened with box beam type stiffeners. In analysis the discrete stiffener theory is adopted to present the effect of stiffeners in the plate structure. The convergence study is presented to demonstrate the accuracy of the results. Contour plots of the vibrated and buckled mode shapes are shown for some examples. The effect of various parameters such as numbers, position, aspect ratio of stiffener and layer angle, aspect ratio of plate are focused.