Analysis of Ring-Stiffened Cylindrical Shells

1995 ◽  
Vol 62 (4) ◽  
pp. 1005-1014 ◽  
Author(s):  
Bingen Yang ◽  
Jianping Zhout
Keyword(s):  
Natural Frequencies ◽  
Transfer Functions ◽  
Cylindrical Shells ◽  
Middle Surface ◽  
Mode Shapes ◽  
Structural Components ◽  
Modeling And Analysis ◽  
Stiffened Shells ◽  
Modeling Techniques ◽  
Stiffened Cylindrical Shells

A new analytical and numerical method is presented for modeling and analysis of cylindrical shells stiffened by circumferential rings. This method treats the shell and ring stiffeners as individual structural components, and considers the ring eccentricity with respect to the shell middle surface. Through use of the distributed transfer functions of the structural components, various static and dynamic problems of stiffened shells are systematically formulated. With this transfer function formulation, the static and dynamic response, natural frequencies and mode shapes, and buckling loads of general stiffened cylindrical shells under arbitrary external excitations and boundary conditions can be determined in exact and closed form. The proposed method is illustrated on a Donnell-Mushtari shell, and compared with finite element method and two other modeling techniques.

Distributed Transfer Function Analysis of Ring-Stiffened Cylindrical Shells

1995 ◽  
Author(s):  
J. Zhou ◽  
B. Yang
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Function Analysis ◽  
Cylindrical Shells ◽  
Middle Surface ◽  
Mode Shapes ◽  
Structural Components ◽  
Stiffened Shells ◽  
Transfer Function Analysis ◽  
Stiffened Cylindrical Shells

Abstract A new analytical and numerical method is presented for modeling and analysis of cylindrical shells stiffened by circumferential rings. This method treats the shell and ring stiffeners as individual structural components, and considers the ring eccentricity with respect to the shell middle surface. Through use of the distributed transfer functions of the structural components, various static and dynamic problems of stiffened shells are systematically formulated. With this transfer function formulation, the static and dynamic response, natural frequencies and mode shapes, and buckling loads of general stiffened cylindrical shells under arbitrary external excitations and boundary conditions can be determined in exact and closed-form. The proposed method is illustrated on a Donnell-Mushtari shell, and compared with finite element method and two other modeling techniques.

Analysis for the Dynamic Response of Stiffened Shells

1973 ◽  
Vol 40 (4) ◽  
pp. 1085-1090 ◽  
Author(s):  
A. Harari ◽  
M. L. Baron
Keyword(s):  
Dynamic Response ◽  
Excellent Agreement ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Shell Elements ◽  
Stiffened Shells ◽  
End Caps ◽  
Stiffened Cylindrical Shells ◽  
Theoretical Results ◽  
Theory And Experiment

The natural frequencies and mode shapes for the vibrations of stiffened cylindrical shells with, or without, hemispherical end caps are evaluated. The approach utilizes a theory in which the shell elements and the circumferential stiffeners are considered as separate structures and compatibility is enforced at their junctures. The results are compared with those from orthotropic theory in which the stiffener effects are smeared over the shell. Numerical results are presented for frequencies and mode shapes for several cases of interest. The theoretical results have been compared with a set of experimental results from the Ordnance Research Laboratories and excellent agreement has been found. Comparisons of theory and experiment are presented in this paper.

Observed Natural Frequencies, Damping Ratios, and Mode Shapes of Vibration of a 30-Story Building Excited by a Major Earthquake and Typhoon

2010 ◽  
Vol 26 (2) ◽  
pp. 371-397 ◽  
Author(s):  
Kun-Sung Liu ◽  
Yi-Ben Tsai
Keyword(s):  
Natural Frequencies ◽  
Transfer Functions ◽  
Measurement Data ◽  
Spectral Ratio ◽  
Transverse Mode ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Building Structures ◽  
Ambient Vibrations ◽  
Frequency Changes

The safety of building structures and contents, as well as the comfort of occupants, under such strong forces as earthquakes and typhoons remain major engineering concerns. In order to improve our understanding of building structural responses, records of a structural array in the 30-story PS Building in Taipei from the M7.6 Chi-Chi earthquake and Typhoon Aere are analyzed. In addition, wind data measured at the Taipei Meteorological Station are also used. First, the field measurement data clearly demonstrate that serviceability of the PS Building met the criteria for occupant comfort during Typhoon Aere. Secondly, several structural vibration parameters of this highrise building, including the transfer functions, natural frequencies, damping ratios and mode shapes, excited by the Chi-Chi earthquake, Typhoon Aere, and ambient vibrations are also determined and compared. The results show the frequency of the first mode for the longitudinal components is approximately 8.6% lower for the earthquake than the ambient vibrations. The transverse mode frequencies behave similarly. In contrast, frequency changes from the typhoon to ambient vibrations are in the third decimal (1.3% and 0.9% lower in the longitudinal and transverse directions, respectively), indicating little nonlinearity. The damping ratios of the PS Building apparently increase with vibration amplitudes. Finally, results of a spectral ratio analysis of the Chi-Chi earthquake data do not indicate significant SSI effects in the longitudinal and transverse directions.

Free Vibrations of Longitudinally Stiffened Cylindrical Shells

1974 ◽  
Vol 41 (4) ◽  
pp. 1087-1093 ◽  
Author(s):  
J. T. S. Wang ◽  
S. A. Rinehart
Keyword(s):  
Experimental Data ◽  
Free Vibration ◽  
Cylindrical Shells ◽  
Free Vibrations ◽  
Mode Shapes ◽  
Structural System ◽  
Isotropic Cylinder ◽  
Simply Supported ◽  
Thin Walled ◽  
Stiffened Cylindrical Shells

This study is concerned with the free-vibration characteristics of thin cylindrical shells reinforced by longitudinal stringers for any edge boundary conditions. The structural system is treated as an isotropic cylinder interacting with a set of discrete thin-walled stringers. Frequencies of simply supported shells obtained according to the present analysis compare favorably with Ritz solution and existing experimental data. For mode shapes, the present analysis often yields much better results than Ritz solution. Numerical results for frequencies and mode shapes for clamped-clamped cylindrical shells are included, and frequencies of a shell with very flexible stiffeners compare favorably with frequencies of an unstiffened shell.

Analytical and Experimental Modal Characteristics of Cylindrical Shells

2005 ◽  
Author(s):  
Basem Alzahabi
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Offshore Structures ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Design Stage ◽  
Scaled Model ◽  
Modal Characteristics ◽  
Acoustic Signature

Cylindrical Shells are widely used in many structural designs, such as offshore structures, liquid storage tanks, submarine hulls, and airplane hulls. Most of these structures are required to operate in a dynamic environment. The acoustic signature of submarines is very critical in such high performance structure. Submarines are not only required to sustain very high dynamic loadings at all time, but also being able maneuver and perform their functions under sea without being detected by sonar systems. Reduction of sound radiation is most efficiently achieved at the design stage, and the acoustic signatures may be determined by considering operational scenarios, and modal characteristics. The acoustic signature of submarines is generally of two categories; broadband which has a continuous spectrum; and a tonal noise which has discrete frequencies. Therefore, investigating the dynamic characteristics of cylindrical shells is very critical first step in developing a strategy for modal vibration control for specific operating conditions. Unlike those of beam structure, the lowest natural frequency does not necessarily correspond to the lowest wave index. In fact, the natural frequencies do not fall in ascending order of the wave index in cylindrical shells. Mode shapes associated with each natural frequency are combination of Radial, Longitudinal, and Circumferential modes. In this paper, a scaled model of submarine hull segment under shear diaphragm boundary conditions is analyzed analytically and numerically. Then experimental modal analysis of the scaled model utilizing a fixed response approach was performed to obtain the modal characteristics of the cylindrical shell between 0 and 800 Hz. The cylinder was excited at predetermined points with an impact hammer, while the response was measured using an accelerometer at specified fixed point. Designing a boundary condition that simulate a shear diaphragm is very challenging task by itself. A total of ten natural frequencies were found within that range with their corresponding mode shapes. The experimental data were correlated with those results obtained analytically and numerically using the finite element methods using MSC.NASTRAN software. The results were found to be in excellent agreement.

Modal Characteristic of Cantilevered Beams and Plates: A Study of Transition From Beam-Like to Plate-Like Behaviour

1999 ◽  
Author(s):  
K. Tangchaichit ◽  
S. O. Oyadiji
Keyword(s):  
Transition Point ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Fe Analysis ◽  
Mode Shapes ◽  
Structural Components ◽  
Cantilevered Plates ◽  
The Difference ◽  
Cantilevered Beams ◽  
High Length

Abstract The paper presents the finite element (FE) analysis of the free vibrations of cantilevered aluminium alloy beams and plates of 5mm thickness and of length-to-breadth ratios ranging from a ratio of 20 for a beam down to a ratio of 0.25 for a plate. The analysis was carried out using the ABAQUS FE programme. For each ratio, a total of 20 natural frequencies and mode shapes were predicted. The objective of the paper was to demonstrate that a transition zone for beam-like to plate-like behaviour of structural components can be approximately defined for various length-to-breadth ratios. It is shown that the frequency parameters of cantilevered plates asymptotically approach the frequency parameters of cantilevered beams at high length-to-breadth ratios. In addition, it is shown that at the transition point for beam-like to plate-like behaviour, which occurs at small length-to-breadth ratios, the difference between the frequency parameters of cantilevered beams is less than the frequency parameters of cantilevered plates about 3 %.

Asymmetric Free Vibrations of Layered Conical Shells

1982 ◽  
Vol 104 (2) ◽  
pp. 453-462 ◽  
Author(s):  
K. Chandrasekaran ◽  
V. Ramamurti
Keyword(s):  
Natural Frequencies ◽  
Middle Surface ◽  
Free Vibrations ◽  
Mode Shapes ◽  
Orthotropic Materials ◽  
Conical Shells ◽  
Shell Models ◽  
Theoretical Predictions ◽  
Parametric Studies ◽  
Ritz Procedure

Asymmetric free vibrations of layered truncated conical shells are studied. Individual layers made of special orthotropic materials and both symmetric and asymmetric stacking with respect to the middle surface are considered. An energy-method based on the Rayleigh-Ritz procedure is employed. The influence of layer arrangements and that of the coupling between bending and stretching on the natural frequencies and mode-shapes are analyzed. Experimental results from tests on two shell models are provided for comparison with theoretical predictions. Numerical results based on extensive parametric studies are presented.

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