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A thin-walled structure that is an assemblage of stiffened panels in which various kinds of general and local buckling can occur

Different types of buckling in each stiffened panel include:
1. Global buckling of stiffened panel
2. Buckling of skin and stringers between adjacent transverse stiffeners
3. Buckling of skin between stiffeners
4. Buckling of parts of the stiffeners
5. Combined buckling modes.
6. Global buckling of a panel in which one or more types of local buckling have already occurred.

Khostrow Ghavami (1) and Mohammad Reza Khedmati (2)
(1) Department of Civil Engineering, Pontificia Universidade Católica (PUC-Rio,) Rio de Janeiro, , Brazil
(2) Faculty of Marine Technology, Amirkabir University of Technology, Tehran, , Iran
“Nonlinear large deflection analysis of stiffened plates”, Chapter 4 in Finite Element Analysis – Applications in Mechanical Engineering, edited by Farzad Ebrahimi, October 2012, DOI: 10.5772/48368

PARTIAL INTRODUCTION: Stiffened plates are basic structural members in marine structures as shown in Figure 1, and include also aeronautic and space shuttles among other structures. Due to the simplicity in their fabrication and high strength-to-weight ratio, stiffened plates are also widely used for construction of land based structures such as box girder and plate girder bridges. The stiffened plate has a number of one-sided stiffeners in either one or both directions, the latter configuration being also called a grillage ( Figure 2). Ultimate limit state design of Stiffened plates’ structures requires accurate knowledge about their behaviour when subjected to extreme loading conditions. One of the most important loads applied on stiffened plates is the longitudinal in plane axial compression arising for instance from longitudinal bending of the ship hull girder as presented in Figure 3. The need to improve our knowledge of the buckling modes of such plates was emphasised after the collapse of several offshore structures and some ships in Brazil as well as the failure of several box girder bridges in the seventies of the twentieth century, Merrison Committee [ 1], Crisfield [ 2], Murray [ 3], Frieze, [ 4]. Stiffened plates are efficient structures, as a large increment of the strength is created by a small addition of weight in the form of stiffeners. However the collapse mechanisms of stiffened plates under predominantly compressive load present a complex engineering problem due to the large number of possible combinations of plate and stiffener geometry, materials, boundary conditions and loading. The design of such structure has to meet several requirements such as minimization of the weight and maximization of the buckling load. Thus, the designer of this structure is confronted with the problem of satisfying two conflicting objectives; such problems are called multi-objective or vector optimisation problems. In general, the objective-functions do not attain their optimum in a common point of the feasible points, Brosowski & Ghavami [ 5, 6].

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