Edge Shear Loads Research Articles

An experimental and numerical investigation on buckling strength assessment of perforated plates under combined in-plane loads

Openings and cut-outs are widely used in ship structures for inspection, maintenance, service purposes, and lightning of the structure, reducing the buckling strength of the plates. This paper presents linear and elastic buckling analyses of the perforated plates, located in the double bottom floor of a container ship, under mutual interaction of both geometric discontinuities (opening and cut-outs) and subjected to combined in-plane loads (longitudinal compression, transverse compression, biaxial compression, and in-plane edge shear loading). A series of experimental and numerical analyses are undertaken on perforated plates under the determination of the influence of different stiffening methods, their relation to the load condition and different values of the plate slenderness ratio. The most effective stiffening method is obtained and alternative geometries that optimize the weight of the structure are proposed by means of topology optimization. The results shown are useful for understanding this structural failure and provide design and recommendation guidelines, improving the quality of the hull inspections and the ability to evaluate the structural defects.

Vibration and Acoustic Radiation of Stiffened Plates Subjected to In‐Plane Forces

This study is devoted to vibration and acoustic radiation of stiffened plates in the presence of in‐plane normal and shear loads using the finite element method. In structural modelling, the plate and stiffeners are treated as separate elements and the strain and kinetic energies of the stiffened plate with an elastic boundary are introduced. The results show good agreement with those obtained using other methods. Parametric studies show that in‐plane normal forces have obvious influences on the acoustic radiation efficiency and the sound power level of the structure. Furthermore, the position of in‐plane normal forces warrants attention; e.g., the farther the boundary in‐plane normal forces from the boundary constraint are, the greater the effect on the acoustic performance is. However, in‐plane edge shear loading has little influence on the acoustic performance of structures.

Effect of reinforcement on buckling and ultimate strength of perforated plates

Cutouts are widely used in ships and offshore structures. These cutouts are used mainly for inspection, and they may be fitted for various purposes, including passing pipes and weight reduction. In general, plates with cutouts (perforated plates) are given high importance at the structural design stage because they can reduce the structural strength. In this regard, local reinforced perforated plates are used in shipyards to satisfy buckling and ultimate strength requirements, but quantitative evaluations of the reinforced perforated plates have not yet been carried out. To mitigate the decrease in the strength of perforated plates, the Carling, face-plating, and doubling stiffening methods have been adopted with the goal of increasing both the buckling and ultimate strengths. In particular, the Carling stiffener has been partially adopted at holes typically found in shipyards (e.g., access holes, lightening holes), but no standard methodologies or recommendations are available for the use of this stiffener. In the present study, a series of numerical studies were undertaken to analyze the buckling and ultimate strengths for various stiffening methods (Carling, face-plating, and doubling) and loading conditions (axial compression and in-plane edge shear loading). An optimal reinforcement method was determined by comparing stiffened weights and ultimate strengths of the three methods. Finally, a design formula for calculating the ultimate strength of a perforated plate was developed on the basis of over 144 cases of finite element analysis.

Buckling behavior of strengthened perforated plates under shear loading

This paper is dedicated to the buckling behaviors of strengthened perforated plates under edge shear loading, which is a typical load pattern of steel plates in civil engineering, especially in plate and box girders. The square plates considered each has a centric circular hole and is simply supported on four edges in the out-of-plane direction. Three types of strengthening stiffeners named ringed stiffener (RS), flat stiffener (FSA and FSB) and strip stiffener (SSA, SSB and SSC) are mainly discussed. The finite element method (FEM) has been employed to analyse the elastic and elasto-plastic buckling behavior of unstrengthened and strengthened perforated plates. Results show that most of the strengthened perforated plates behave higher buckling strengths than the unstrengthened ones, while the enhancements in elastic buckling stress and elastoplastic ultimate strength are closely related to sti ffener types as well as plate geometric parameters including plate slenderness ratio and hole diameter to plate width ratio. The critical slenderness ratios of shear loaded strengthened perforated plates, which determine the practical buckling pattern (i.e., elastic or elasto-plastic buckling) of the plates, are also studied. Based on the contrastive analyses of strengthening efficiency considering the influence of stiffener consumption, the most efficient cutout-strengthening methods for shear loaded perforated square plates with different slenderness ratios and circular hole diameter to plate width ratios are preliminarily identified.

Ultimate strength of perforated steel plates under combined biaxial compression and edge shear loads

The present paper is a sequel to the author's papers [Paik JK, Ultimate strength of perforated steel plates under edge shear loading. Thin-Walled Structures 2007; 45: 301–6, Paik JK Ultimate strength of perforated steel plates under axial compressive loading along short edges. Ships Offshore Struct, 2007; 2(3): (in press)]. In contrast to the previous papers with the focus on edge shear or uniaxial compressive loads, the aim of the present study is to investigate the ultimate strength characteristics of perforated steel plates under combined biaxial compression and edge shear loads, which is a typical action pattern of steel plates arising from cargo weight and water pressure together with hull girder motions in ships and ship-shaped offshore structures. The plates are considered to be simply supported along all (four) edges, keeping them straight. The cutout is circular and located at the center of the plate. A series of ANSYS nonlinear finite element analyses (FEA) are undertaken with varying the plate dimension (thickness). Based on the FEA results obtained, closed-form empirical formulae of the ultimate strength interaction relationships of perforated plates between combined loads, which can be useful for first-cut estimations of the ultimate strength in reliability analyses or code calibrations, are derived.

Ultimate strength of perforated steel plates under edge shear loading

The aim of the present study is to investigate the ultimate strength characteristics of perforated steel plates under edge shear loading, which is a primary action type arising from cargo weight and water pressure in ships and ship-shaped offshore structures. The plates are considered to be simply supported along all (four) edges and kept straight. The cutout is circular and located at the center of the plate. A series of ANSYS nonlinear finite element analyses (FEA) are undertaken with varying the cutout size (diameter) as well as plate dimensions (plate aspect ratio and thickness). By the regression analysis of the FEA results obtained, a closed-form empirical formula for predicting the ultimate shear strength of perforated plates, which can be useful for first-cut strength estimations in reliability analyses or code calibrations, is derived. The accuracy of the ultimate strength formula developed is verified by a comparison with more refined nonlinear FEA results.

Ultimate strength of dented steel plates under edge shear loads

The aims of this paper are to investigate the ultimate shear strength reduction characteristics of steel plates due to local impacts, and also to develop the ultimate shear strength design formulae of dented steel plates. The ANSYS nonlinear finite element code is used to investigate the effects of shape, size (depth, diameter), and location of the denting on the ultimate strength behavior of simply supported steel plates under edge shear loads. A closed-form expression for predicting the ultimate shear strength of dented steel plates is derived by the regression analysis based on the computed results. The results and insights developed from the present study will be very useful for damage tolerant design of steel plated structures with local denting.

Nonlinear and postbuckling analyses of curved composite panels subjected to combined temperature change and edge shear

The results of a detailed study of the nonlinear and postbuckling responses of curved unstiffened composite panels with central circular cutouts are presented. The panels are subjected to uniform temperature change and an applied in-plane edge shear loading. The analysis is based on a first-order shear-deformation Sanders-Budiansky type theory with the effects of large displacements, moderate rotations, transverse shear deformation and laminated anisotropic material behavior included. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the panel. The nonlinear displacements, strain energy, transverse shear stresses, transverse shear strain energy density, and their hierarchical sensitivity coefficients are evaluated. Numerical results are presented for cylindrical panels with central circular cutouts and are subjected to uniform temperature change and an applied in-plane edge shear loading. The results show the effects of variations in the panel curvature, hole diameter, laminate stacking sequence and fiber orientation, on the nonlinear and postbuckling panel responses, and their sensitivity to changes in the various panel, layer and micromechanical parameters.

Buckling of Orthotropic, Curved, Sandwich Panels Subjected to Edge Shear Loads

A linear analysis is presented for determining the shear buckling load of a rectangular, sandwich panel with constant cylindrical curvature and having specially orthotropic facings and core. Solution for classical simplesupport boundary conditions was carried out by the Galerkin method, taking precautions not to escalate the equations by differentiati on. This resulted in two doubly infinite sets of eigenvalue equations, representing buckling in the symmetric and unsymmetric modes. Numerical solutions were obtained on a digital computer and the results were compared with those of previous analyses for special cases and with limited test data available for the general case. Finally parametric design curves are presented for a range of parameters.