Parametric Resonance of Skew Stiffened Plates

1973 ◽  
Vol 40 (2) ◽  
pp. 439-444 ◽  
Author(s):  
R. G. Merritt ◽  
N. Willems
Keyword(s):  
Perturbation Technique ◽  
Equation Of Motion ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Skew Angle ◽  
Principal Resonance ◽  
First Approximation ◽  
Spatial Modes ◽  
Principal Region ◽  
Boundary Curves

An investigation of the region of principal resonance of low-order spatial modes of an in-plane loaded, skew stiffened plate is considered. Hamilton’s principle is used to arrive at the equation of motion in which plate stiffening is accounted for through discrete representation. The method of averaging in the first approximation reduces the equation of motion to two independent equations which are subsequently solved by a perturbation technique in order to determine boundary curves for the principal region of resonance. Selected numerical examples indicate the effect of variation of skew angle and stiffening on the principal region of resonance. A brief discussion of problems inherent in this consideration of simply supported skew plates is included.

Numerical Investigation of Ultimate Strength of Stiffened Plates With Various Cross-Section Forms

2018 ◽  
Author(s):  
Huilong Ren ◽  
Yifu Liu ◽  
Chenfeng Li ◽  
Xin Zhang ◽  
Zhaonian Wu
Keyword(s):  
Aluminum Alloy ◽  
Ultimate Strength ◽  
Cross Section ◽  
High Performance ◽  
Lightweight Design ◽  
Offshore Structures ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Element Analysis ◽  
Hull Structure

There is an increasing interest in the lightweight design of ship and offshore structures, more specifically, choosing aluminum alloys or other lightweight high-performance materials to build structure components and ship equipments. Due to its better mechanical properties and easy assembly nature, extruded aluminum alloy stiffened plates are widely used in hull structures. When the load on the hull reaches a certain level during sailing, partial or overall instability of stiffened plate makes significant contribution in an event of collapse of the hull structure. It is very necessary to investigate the ultimate strength of aluminum alloy stiffened plate to ensure the ultimate bearing capacity of large aluminum alloy hull structure. Most of studies of the ultimate strength of stiffened plates deal with stiffened plates with T–shaped stiffeners. Stiffeners of other shapes have seldom been explored. In this research, the ultimate strength of six different cross–section aluminum alloy stiffened plates and one steel stiffened plate was studied based on the non–linear finite element analysis (FEA). Taking into account stiffness, weight and other issues, the new cross–section aluminum stiffener has finally been concluded for replacing the original steel stiffener in upper deck of a warship.

RELIABILITY OF CORRODED STIFFENED PLATE SUBJECTED TO UNIAXIAL COMPRESSIVE LOADING

2021 ◽  
Vol 162 (A4) ◽  
Author(s):  
K Woloszyk ◽  
Y Garbatov
Keyword(s):  
Mechanical Properties ◽  
Reliability Index ◽  
Structural Reliability ◽  
Limit State ◽  
Plate Thickness ◽  
Thickness Reduction ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Initial Imperfections ◽  
Subsequent Decrease

The work is focused on the reliability of corroded stiffened plates subjected to compressive uniaxial load based on the progressive collapse approach as stipulated by the Common Structural Rules for Bulk Carriers and Oil Tankers, employing the limit state design. Two different cases have been investigated. In the first model, the corrosion degradation led to uniform thickness loss, whereas the mechanical properties were unchanged, as given in the Rules. In the second model, the plate thickness degradation was followed by mechanical properties reduction. The uncertainties related to the mechanical properties, thicknesses, and initial imperfections of the corroded stiffened plate were taken into account. Several initial design solutions of stiffened plates, as well as different severity levels of corrosion degradation were investigated. The results show that structural reliability significantly decreases with corrosion development, especially when in addition to the initial imperfections and corrosion plate thickness reduction, corroded plate surface roughness and the changes in the mechanical properties were considered. The uncertainties, their origins and confidence levels are discussed. It was found that non-linear time-dependent corrosion degradation accounting not only for the thickness reduction due to corrosion wastage but also the subsequent decrease of mechanical properties lead to a significant reduction in the reliability index. Additionally, it was defined that the reliability estimate is very sensitive to the uncertainties related to the initial thickness and the spread of corrosion degradation as a function of the time. Incorporating the probability of corrosion detection into the original reliability model introduces additional information about the validity of structural degradation that may lead to a higher beta reliability index estimate compared to the original model.

A Comparative Numerical Study on the Bending Response of Aluminium Stiffened Plates With Fixed/Floating Frames

2008 ◽  
Author(s):  
Mohammad Reza Khedmati ◽  
Mehran Rastani
Keyword(s):  
Finite Element ◽  
Maximum Stress ◽  
Numerical Study ◽  
Point Of View ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Finite Element Analyses ◽  
Bending Response ◽  
Structural Arrangements

In this paper, different structural arrangements of the transverse frames in an orthogonally stiffened plate are investigated from the bending response point of view. The transverse frames are assumed to be either fixed or floating. Other alternate placements of the transverse frames are also included in the comparative calculations. Stress and deflection contours are obtained via finite element analyses. Finally, some recommendations are outlined comparing the results of maximum stress and deflection with the allowable limits.

VIBRATION AND DYNAMIC INSTABILITY OF STIFFENED PLATES SUBJECTED TO IN-PLANE HARMONIC EDGE LOADING

2002 ◽  
Vol 02 (02) ◽  
pp. 185-206 ◽  
Author(s):  
A. K. L. SRIVASTAVA ◽  
P. K. DATTA ◽  
A. H. SHEIKH
Keyword(s):  
Dynamic Instability ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Stiffness Properties ◽  
Edge Loading ◽  
Instability Regions ◽  
Varying Mass ◽  
Good Agreement

The vibration and dynamic instability behavior of a stiffened plate subjected to uniform in-plane edge loading is studied using finite element analysis. The method of Hill's infinite determinants is applied to analyze the dynamic instability regions. Rectangular stiffened plates possessing different boundary conditions, aspect ratios, varying mass and stiffness properties and varying number of stiffeners have been analyzed for dynamic instability. The results are obtained considering the bending displacements of the plate and the stiffener. Eccentricity of the stiffeners give rise to axial and bending displacement in the middle plane of the plate. The results show that the principal instability regions have a significant effect considering and neglecting in-plane displacements. Comparison with published results indicates good agreement.

Experimental Study on Crack Propagation and Strain Accumulation of Cracked Stiffened Plate Under Cyclic Load

2018 ◽  
Author(s):  
Wei Jiang ◽  
Ping Yang ◽  
Ziya Peng
Keyword(s):  
Experimental Study ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Low Cycle Fatigue ◽  
Stiffened Plates ◽  
Strain Accumulation ◽  
Stiffened Plate ◽  
Cycle Fatigue ◽  
Fatigue Load ◽  
Cracked Structures

Stiffened plates with cracked damage are often subjected to constant amplitude and/or variable amplitude cyclic loads in sea environment. Under the stress-controlled asymmetric low-cycle fatigue loads, the coupling effect of low-cycle fatigue crack propagation and accumulative plasticity contributes to the increase of accumulative mean strain of cracked structures. Low-cycle fatigue crack growth and the increase of whole strain of cracked structures will change the bearing capacity of cracked structures. In this paper, experimental study on crack propagation and strain accumulation of cracked stiffened plate under low cycle fatigue load has been conducted. AH32 steel is used to make stiffened plate specimen with crack symmetrically located about stiffener. The accumulative strain of the cracked stiffened plate specimens during low-cycle fatigue crack propagation was obtained. From the experiments for cracked stiffened plates under the low-cycle fatigue loading, it is found out that the crack propagates firstly in the weld and then also gradually takes place in the stiffener. The stress ratio of low-cycle fatigue load and stiffener stiffness have been investigated in the experimental study and it is found out that these parameters significantly affect the low-cycle fatigue crack growth life and accumulation strain of the cracked stiffened plate specimens.

Nonlinear Elastoplastic Behaviour of Intermittently Welded Stiffened Plates Under Inplane Compression

2006 ◽  
Author(s):  
Mohammad Reza Khedmati ◽  
Mehran Rastani
Keyword(s):  
Finite Element ◽  
Compressive Load ◽  
Steel Plates ◽  
Stiffened Plates ◽  
Finite Element Code ◽  
Stiffened Plate ◽  
Plate Models ◽  
Different Types ◽  
Stiffened Steel ◽  
Continuous Chain

The objective of this study is to investigate the sensitivity of the ultimate strength and failure mechanism of stiffened plates constructed by different welding methods in common. A series of detailed numerical analyses of longitudinally stiffened steel plates subjected to inplane compressive load are performed using ADINA commercial finite element code. Complete equilibrium paths are traced up to collapse for nonlinear elastoplastic response of stiffened plates. Stiffened plates analysed are imperfect and their aspect ratio, plate slenderness and column slenderness are changed in a systematic manner. Different types of stiffener are chosen for stiffened plate models. Three different stiffener-to-plate welding procedures are considered: continuous, chain intermittent and staggered intermittent fillet welding.

scholarly journals Three-Dimensional Simulation of Crack Propagation in the Central-Cracked Flat and Stiffened Plates Under Uniform Tension

2020 ◽  
Author(s):  
Mohammad Hossein Taghizadeh Valdi
Keyword(s):  
Crack Propagation ◽  
Crack Tip ◽  
Crack Arrest ◽  
Correction Function ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Propagation Behavior ◽  
Out Of Plane ◽  
Plane Bending ◽  
Geometry Correction

Abstract In this paper, the crack propagation behavior in flat and stiffened plates with central-cracked is studied based on the theory of linear elastic fracture mechanics and 3D finite-element method. The magnitude and distribution of the stress intensity factor in a 3D stiffened plates are affected by the out-of-plane bending and loading modes. Initially, for validating this method, the behavior of crack propagation in a central-cracked flat plate (unstiffened), followed by the propagation behavior and the crack arrest effects on stiffened plates by stiffeners, as well as the out-of-plane bending effect on the geometry correction function distribution are studied; However, the results are compared with the results of the referenced article. In order to analyze the effect of stiffeners in preventing crack expansion, stiffeners with variable thickness and height were used. It should also be noted that the crack propagation behavior in the stiffened plate is analyzed in two methods. In the first analysis, after the crack tip reaches to the stiffeners, they have not fracture and the crack only expands in the stiffened plate (in the stiffened plate type 1 and 2). In the second analysis, with the crack growth in the stiffened plate and the crack tip reaching to the stiffeners, Also they fractured and cracks in the stiffened plate and stiffeners are propagated (only in the stiffened plate type 2). In both analyses, the magnitudes ​​of the geometry correction function in the middle-plane, the crack arrest effect by the stiffeners (Δβs), and the out-of-plane bending effect (Δβ) were obtained. Then, the changes in these magnitudes ​​were investigated. It was observed that the stiffeners thickness had a negligible effect on the distribution of the geometry correction function and, in general, the stiffeners had a significant role in preventing the crack growth compared to the flat plate, and the more the crack tip is closer to the adjoining stiffeners; the stiffeners effect in the crack arrest will increases. Furthermore, with attention to the geometry correction function that is studied for different crack sizes, it was determined that the geometry correction function and stress intensity coefficient with increasing the length of the crack in the plate, increase.

The Orthogonally Stiffened Plate Under Uniform Lateral Load

1940 ◽  
Vol 7 (4) ◽  
pp. A143-A146
Author(s):  
Henry A. Schade
Keyword(s):  
Exact Solution ◽  
Approximate Solution ◽  
Transverse Dimension ◽  
Lateral Load ◽  
Lateral Loading ◽  
Stiffened Plates ◽  
Infinite Strip ◽  
Stiffened Plate ◽  
Longitudinal Dimension ◽  
Side Ratio

Abstract The problem of designing structures with orthogonally stiffened plates under lateral loading has been solved approximately by the infinite-strip method and has been applied, for example, to the double-bottom structure of a ship. Under certain conditions where the side ratio, that is, the ratio of the longitudinal dimension to the transverse dimension, is small, the approximate solution is inadequate. The author gives herein an exact solution applicable to all side ratios.

Bending of Orthogonally Stiffened Plates

1955 ◽  
Vol 22 (2) ◽  
pp. 267-271
Author(s):  
W. H. Hoppmann
Keyword(s):  
Boundary Conditions ◽  
Experimental Method ◽  
Circular Plate ◽  
Elastic Constants ◽  
Orthotropic Material ◽  
Elastic Moduli ◽  
Unit Area ◽  
Stiffened Plates ◽  
Stiffened Plate ◽  
Clamped Edge

Abstract In this paper the flexure theory for plates of orthotropic material is applied in the case of orthogonally stiffened plates using an experimental method to determine plate stiffnesses in bending and in twisting. Once these stiffnesses, or elastic moduli, have been determined by test they may be used in calculating bending deflections for plates of identical stiffened construction but any given boundary conditions. As an example, calculated deflections of a stiffened circular plate with clamped edge are compared with those which were determined experimentally. It is also demonstrated that the theory can be applied to the case of vibration of a stiffened plate if in addition to the orthotropic elastic constants the weight per unit area of the plate is determined. The various experimental results show considerable promise for use of the proposed combination of theory and experimental method in the analysis of both statically and dynamically loaded plates with attached stiffeners.

Nonlinear Dynamic Response of Elastically Supported Stiffened Plates with Initial Stresses and Geometric Imperfections Under Impact Loads

2020 ◽  
Vol 20 (04) ◽  
pp. 2050053
Author(s):  
Niu-Jing Ma ◽  
Li-Xiong Gu ◽  
Long Piao
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Dynamic Properties ◽  
Initial Stresses ◽  
Stiffened Plates ◽  
Impact Loads ◽  
Stiffened Plate ◽  
Geometric Imperfections ◽  
Nonlinear Dynamic Response ◽  
Elastically Supported

This paper deals with the nonlinear dynamic response of elastically supported stiffened plates with initial stresses under impact loads. A stiffened plate is assumed to be composed of a plate with some stiffeners, which are treated separately. The plate is modeled by the thin plate theory, whereas the stiffeners are considered as geometrically nonlinear Euler–Bernoulli beams. First, the equations of both the kinetic energies and strain energies of the plate and stiffeners are established. Then, the dynamic equilibrium equations for the stiffened plate are derived as the Lagrange’s equation of the functional. A parametric analysis is performed to evaluate how initial stresses, initial geometric imperfections, elastic supports, impact loads and configuration of stiffeners affect the time-history responses of the stiffened plates. Some useful nonlinear dynamic properties are obtained, which serve as references for engineering design and application.

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