Parametric analysis on hybrid design method for steel cellular beams

Abstract

Cellular beams are an attractive engineering solution due to their high strength to weight ratio, allowing for a design even lighter and more cost efficient in steel structures. These beams possess enhanced strength and stiffness compared to regular I-section beams of similar weight, due to their higher second moment of area. However, their variable cross-sections along the length introduce different modes of failure, making further research necessary, since there is a lack of standardized processes for their design. This paper investigates the design and verification procedures proposed by Ward (1990), Annex N (1998), Veríssimo et al. (2013), Fares et al. (2016), and Grilo et al. (2018) through a parametric study of cellular beams with varying geometries. To assess the buckling characteristics of cellular beams, shell finite element models are employed, which were previously validated, using experimental tests conducted by other researchers. The results obtained from a Python code implementing these design methods are then compared with Finite Element Method (FEM) analysis results for 80 beams. It can be concluded that the design methods provide conservative results for beams with intermediate or long spans. On the other hand, for beams with short spans, these methods may yield values that compromise safety. Finally, based on the FEM analysis results, a Hybrid Design Method (HDM) is proposed, which incorporates the verification procedures analyzed. This proposed method presents a better failure mode detection and limited load capacity when applied to cellular beams made from regular Brazilian I-section beams.

Keywords:
cellular beams; parametric analysis; finite elements method; failure modes; design method