Few studies have investigated the structural behavior of steel-concrete composite alveolar beams in hogging bending regions. Their resistance can be reached by lateral distortional buckling (LDB), coupling LDB and local failure modes, or limit states of cracking or crushing in the concrete slab. This case is characteristic of continuous or cantilever elements. Another critical issue is that the design and calculation recommendations only address the LDB verification on steel-concrete composite beams without web openings, thus disregarding the interaction between the buckling modes. Furthermore, it is necessary to use adaptations of these formulations for beams with web openings. This review paper aims to evaluate the different approaches for standard code adaptations to verify the LDB resistance of the beams in question and to highlight the investigations that addressed this issue. The addressed adaptations consist of different approaches which determine the cross-section geometric properties in the central region of the openings, the so-called double T section, in the region of the web posts (solid section), and the averages between the solid section and double T section. The accuracy of the formulations in question is verified against experimental results from the literature. Furthermore, discussions and suggestions for further studies are presented.
Lateral distortional buckling (LDB) is an instability phenomenon characteristic of steel-concrete composite beams (SCCB) that occurs in the presence of hogging moments in regions close to internal supports. The LDB behavior in SCCB is not yet fully understood. The procedures for determining the LDB strength are based on the classic lateral torsional buckling theory or on the inverted U-frame model. In addition, the standard procedures make use of the classic design curves of the SSRC (Structural Stability Research Council) and ECCS (European Convention for Constructional Steelwork) developed to analyze the stability behavior of steel elements. However, studies indicate that the use of the same empirical curves obtained for the analysis of steel elements leads to the conservative results of the LDB strength in SCCB. Therefore, this article aims to assess the LDB strength in SCCB through the development of post-buckling numerical analysis using the ABAQUS software. In the parametric study, four types of steel with different mechanical properties were analyzed. In addition, the I-section, the unrestrained length, and the reinforcement rate in the concrete slab were varied. The results showed the influence of the steel type on the LDB strength and deviations from the standard procedures. A small influence of the longitudinal reinforcement area variation was verified in the LDB strength in the FE analyses; however, this factor is significantly important in the standard procedures, causing considerable divergences. These results can provide a reference for future research and specification reviews.
7 December 2023 in Arabian Journal for Science and Engineering