P. Alagusundaramoorthy

Interaction curves for stiffened panel with circular opening under axial and lateral loads

Stiffened panels in ships and offshore oil platforms are provided with circular openings for repair, access and maintenance. This paper presents the numerical study carried out on the ultimate strength of stiffened panel with central circular opening subjected to axial load, lateral load and a combination of axial and lateral loads. Ultimate strength of the panel was evaluated considering both geometric and material non-linearities using FEA software ANSYS. Plates of varied widths and open section unequal angle stiffeners covering plate and column slenderness ratios in the practical range of 1.0–4.5 and 0.32–1.00, respectively, keeping the opening ratio equal to 1.0 are the parameters considered in this study. On the basis of the study, interaction curves were developed for normalised axial load and normalised lateral load. The developed interaction curves for stiffened panels with angle stiffeners and circular opening were found to be non-linear for lower plate slenderness ratio up to 2.0 and for the range of column slenderness ratio covered in the present study. Interaction equations were also proposed based on non-linear regression analysis for determining the ultimate strength of stiffened panel under axial, lateral and also under combined axial and lateral loads.

Ultimate strength of stiffened panels with cutouts under uniaxial compression

Abstract An approximate method based on strut approach to predict the ultimate strength of simply-supported stiffened panels with initial imperfections and square cutouts, subjected to uniaxial compression is presented. The reduction in stiffness of the plate between stiffeners is considered by using an ‘effective width concept’. Tests are reported on welded stiffened steel panels with varying plate slenderness ratio and column slenderness ratio. Based on the experimental investigations and the proposed method, the influence of square openings, extending the full width between stiffeners, on the ultimate strength of stiffened panels is evaluated.

Flexural Behavior of R/C Beams Strengthened with CFRP Sheets or Fabric

The resistance to electrochemical corrosion, high strength to weight ratio, larger creep strain, fatigue resistance, non-magnetic and non-metallic properties of carbon fiber reinforced polymer (CFRP) composites offer a viable alternative to bonding of steel plates in repair and rehabilitation of reinforced concrete structures. The objective of this investigation is to study the effectiveness of externally bonded CFRP sheets or fabric in increasing the flexural strength of concrete beams. Four-point bending flexural tests are conducted up to failure on nine concrete beams strengthened with different layouts of CFRP sheets and fabric, and on three beams with different layouts of anchored CFRP sheets. An analytical procedure, based on compatibility of deformations and equilibrium of forces, is presented to predict the flexural behavior of beams strengthened with CFRP sheets and fabric. Comparisons are made between the test results and the analytical calculations. Results of the testing showed that the flexural strength is increased up to 40% on beams strengthened with two layers of CFRP fabric, 49% on beams strengthened with two 1.42 mm thick CFRP sheets, and 58% on beams strengthened with two anchored 4.78 mm CFRP sheets.

SHEAR STRENGTH OF R/C BEAMS WRAPPED WITH CFRP FABRIC

The emergence of high strength epoxies has enhanced the feasibility of increasing the shear strength of concrete beams by wrapping with carbon fiber reinforced polymer (CFRP) fabric. The objective of this investigation is to evaluate the increase in shear strength of concrete beams wrapped with different configurations of CFRP fabric. Shear tests are conducted up to failure on two reinforced concrete control beams and twelve reinforced concrete beams wrapped with four different configurations of CFRP fabric. An analytical procedure is presented to predict the shear strength of beams wrapped with CFRP fabric. Comparisons are made between the test results and the analytical calculations. The shear strength is increased up to 33% on concrete beams wrapped with CFRP fabric at an angle of +/- 45 deg to the longitudinal axis of the beam.

Experimental study on collapse load of stiffened panels with cutouts

Abstract Experimental investigations are carried out up to collapse on eighteen stiffened steel plates having initial imperfections under uniaxial compression with simply supported boundary conditions on both loading and unloading edges. The thickness of the flange plates is varied as 4 mm and 5 mm respectively. Three types of commercially available open section rectangular flats are used as stiffeners. Six panels without cutout, six panels with square cutout which extends the full width in between stiffeners (d/b=1.0), four panels with rectangular cutout (d/b=1.5) and two panels with reinforced rectangular cutout are fabricated. The initial geometric imperfections such as plate imperfection Δx, overall imperfection of the whole panel Δsx and torsional imperfection in stiffener Δsy are measured for all panels fabricated. The axial deformation of the whole panel, out-of-plane deflections and strains along the midsection of the panels measured during the tests is discussed. The reduction in strength of the panels due to the presence of square cutout, rectangular cutout and increase in strength due to reinforcement around rectangular cutout are calculated based on the experimental observations.

A Novel Setup for Testing of Ship Deck Stiffened Panels under Axial and Lateral Loads

A novel setup for testing of stiffened panels in ship decks subjected to axial and lateral loads is developed in the Department of Ocean Engineering, IITMadras. The entire setup consists of self-straining test rig, imperfection measuring device, displacement controlled hydraulic jacks, rigid grillage, inflatable air balloon with and without opening, and a data acquisition system. The fabricated deformable test rig replicates similar boundary conditions along the loaded and unloaded edges of stiffened panels in between transverse stiffeners of a ship deck. An imperfection measuring device located on the test rig is designed and fabricated to measure geometrical initial imperfections on the plate and stiffener. A unique displacement controlled twin hydraulic jack system is developed to apply axial load on the panel. A rigid grillage connected to the bottom of the test rig to act as reactive support for the application of lateral load on the panel is fabricated by performing static nonlinear analysis using ANSYS. An inflatable air balloon with and without opening is fabricated to simulate constant cargo (lateral) load acting on the panels. The applied axial load and produced axial deformation measured by load cells and LVDT, respectively, is plotted simultaneously while testing using an integrated data acquisition system. Nonlinear finite element analysis of tested specimens is performed using ANSYS to compare the ultimate load obtained from experiments. A close agreement between the experimental data and finite element analysis results indicates realistic simulation of truly combined axial and lateral loads with deformable supports acting on stiffened panels as in ship decks achieved in the laboratory and numerically.

ULTIMATE STRENGTH OF STEEL AND GLASS FIBRE REINFORCED COMPOSITE PLATES WITH SQUARE OPENING UNDER AXIAL AND OUT OF PLANE LOADS

The weight of glass fiber reinforced polymer composite (GFRP) plate is about one fourth of the steel plate and can be used in ship and offshore structures, so that the payload can be increased. However comparative studies on the behaviour of steel and GFRP composite plates with square opening have not been studied in detail. The experimental studies on steel and GFRP plates with and without openings are carried out for the combined loading of axial compression and out-of-plane loads. The in-plane and out-of-plane deflections are measured. The reduction in the axial load carrying capacity of the plates due to out-of-plane load is quantified. The effect of column slenderness ratio and plate slenderness ratio on the collapse load of simply supported stiffened plates is presented. Two sets of interaction equations are developed, one for the steel plate and another for the GFRP composite plate.Copyright

Flexural Behavior of Concrete Sandwich Panels Under Punching Load and Four-Point Bending—Experimental and Analytical Study

Concrete sandwich structural panels can serve dual purposes of transferring load and insulating. This paper presents and discusses results of experimental and numerical studies carried out to understand the flexural behavior of concrete sandwich panels under different flexural loading conditions such as four-point bending and punching load. The experimental study consisted of testing two prototype concrete sandwich panels. Wythes of the panels were reinforced using wire mesh and rebars, and shear connectors were used to connect both wythes. Experimental study indicated that flexural behavior of these panels is significantly affected by type of the loading conditions. Though constructional details of both panels tested in this study are same, failure mode of the panels are different under four-point bending and punching load. The panel tested under four-point bending failed by forming inclined shear cracks and the panel tested under punching load failed by forming flexural cracks. Numerical analysis was carried out using finite element package ABAQUS. Numerical models developed are able to approximately predict load-deflection responses of concrete sandwich panels under different loading conditions. Further experimental and numerical studies are required in this area toward developing design guidelines.

Inspection and Evaluation of a Bridge Deck Partially Reinforced With GFRP Rebars

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