Influence of web holes on the structural design of cellular beams: central perforated plate buckling under compression

Leitão, César Hernández

http://hdl.handle.net/10198/35375

Use this identifier to reference this record.

Name:	Description:	Size:	Format:
César Leitão.pdf		19.95 MB	Adobe PDF	Download

Send Feedback

Authors

Leitão, César Hernández

Advisor(s)

Mesquita, L.M.R.

Abstract(s)

Cellular steel beams gain their efficiency from circular, or other shapes, cutouts on the web panel, but these openings reduce compressive buckling capacity and trigger complex failure modes. This study quantifies the role of hole geometry in governing both elastic and plastic behaviors, developing design formulas that account for these effects. This process is made in three steps: An analytical stage, where using energy-based Ritz formulation, closed form for the critical buckling coefficient kf,app. of simply supported plates containing a circular cutout at the center, covering aspect ratios 1 ≤ β ≤ 4 and cutout ratios 0.1 ≤ df /b ≤ 0.8. This solution is only reliable for df /b = 0.1. The numerical stage, where Eigenvalue buckling analysis and GMNIA are performed in ANSYS, that supported the validation of proposed equations, and reproduced mode switching phenomena (e.g., for odd β, the governing half-wave number m is always equal to β). Experimental stage, where compression tests on solid plates made from S235JR steel, with a thickness of 1.5mm confirmed the predictions within 0.82% for an aspect ratio of 1.1, and 0.96% for an aspect ratio of 1.5. These allowed the FEM calibration and the closed form model. The parametric analysis, revealed an optimal design windows at β = 2 and β = 4, with a df /b = 0.5 ratio, delivering the highest buckling loads before plastic mechanisms arise. As for square plates, the hole centered, coincide with the maximum amplitude line, reducing its buckling capacity. The resulting formulas predict the numerical solution with different accuracies. For fixed β values, the approximation is much better. The usage of approximated expression with double variables should be used only if really needed for other values different of β.