Ultimate Strength of Aluminum Plates and Stiffened Panels for Marine Applications

Abstract

The use of high-strength aluminum alloys in marine construction has certainly obtained many benefits, particularly for building fast ferries and also for military purposes. It is commonly accepted that the collapse characteristics of aluminum structures are similar to those of steel structures until and after the ultimate strength is reached, regardless of the differences between them in terms of material properties. However, it is also recognized that the ultimate strength design formulas available for steel panels cannot be directly applied to aluminum panels even though the corresponding material properties are properly accounted for. This is partly due to the fact that the stress versus strain relationship of aluminum alloys is different from that of structural steel. That is, the elastic-plastic regime of material after the proportional limit and the strain hardening plays a significant role in the collapse behavior of aluminum structures, in contrast to steel structures where the elastic perfectly plastic material model is well adopted. Also, the softening in the heat-affected zone significantly affects the ultimate strength behavior of aluminum structures, whereas it can normally be neglected in steel structures. In this paper, the ultimate strength characteristics of aluminum plates and stiffened panels under axial compressive loads are investigated through ANSYS elastic-plastic large deflection finite element analyses with varying geometric panel properties. An "average" level of welding-induced softening and initial imperfections is assumed for the analyses. Closed-form ultimate compressive strength formulas for aluminum plates and stiffened panels are derived by regression analysis of the computed results.

Study on Ultimate Compressive Strength of Aluminium-Alloy Plates and Stiffened Panels

“…For evaluating the ultimate compressive strength of aluminium plates rapidly, several formulations are developed like one of Johnson-Ostenfeld, Faulkner (1975), Kristensen (2001), Paik and Duran (2004), Wang et al (2005) and Eurocode 9 (2009). Initially, the critical buckling strength of aluminium plates may be estimated based on the Johnson-Ostenfeld formulation which is well summarized in Paik et al (2005b), Paik (2018) and Syrigou and Dow (2018). It is given as follows:…”

“…The deck and bottom structures of ships are subjected periodically to compressive and tensile loads resulting from the sagging and hogging vertical bending moments. In this case, the plating between longitudinal stiffeners and transverse frames is compressed, and thus in most current practical design materials, it is assumed to be simply supported or clamped at four edges subjected to an axial load (Wang et al 2005;Yao and Fujikubo 2016;Paik 2018). At the initial regime of loading, the compressive stress and lateral deflection increase linearly.…”

Load shortening characteristics of marine grade aluminium alloy plates in longitudinal compression

“…Mazzolani [20] suggests a 25mm representative HAZ, based on experiments. Zha and Moan [23] and Paik and Duran [13] also propose a 25mm HAZ breadth. In addition, Zha tested HAZ breadths of 12.5mm.…”

“…Paik and Duran [13] developed a design formula specifically to define the ultimate strength of flat rectangular unstiffened aluminium plates including the effects of the HAZ. The formulation is based on regression of results from NLFEM analyses of plates with material properties equivalent to 5083-H116, 5383-H116 and 6082-T6 aluminium alloys.…”

Compression load failure of aluminum plates due to fire

“…Studies have been reported on the structural response of aluminum under compression at room temperature for flat plates [1], different cross-sections [2][3][4], and effects of welds [1,3,4]. Elevated temperature thermo-structural response of aluminum alloys under compression loading has been measured for columns and sections with welds [6][7][8].…”