Assessment of rotational stiffness in HSS-UHPC composite cellular beams under hogging moment

Resumo

The structural system comprising a steel section and a concrete slab, interconnected by shear connectors, is referred to as a steel–concrete composite beam. These beams may be designed as simply supported, continuous, or semi-continuous elements. In the latter two configurations, the verification of the hogging moment region is critical to prevent the occurrence of lateral-distortional buckling (LDB). For this purpose, design standards recommend the calculation of the elastic critical moment, which can be estimated using the inverted U-frame mechanism. This approach accounts for the rotational stiffness of each constituent component of the composite beam to determine the overall stiffness, thereby facilitating its practical application. However, the methodologies prescribed by current design codes do not fully address the diversity of cross-sectional geometries and material properties available in contemporary construction, such as high-strength steels (HSS) and ultra-high-performance concrete (UHPC). These limitations may result in reduced accuracy when applied to composite members that deviate from conventional configurations—specifically, I-section beams without web openings and normal-strength concrete slabs. Accordingly, this study aims to numerically investigate the rotational stiffness of composite cellular beams composed of HSS and UHPC in regions subjected to negative bending moments. A novel predictive formulation for rotational stiffness is proposed using machine learning algorithms. Finite element models were developed in ABAQUS and validated against experimental data from the literature. Preliminary results from a parametric study indicate that web thickness, web opening diameter, and steel grade are among the most influential parameters affecting rotational stiffness. The findings also highlight that the overall flexibility of the mechanism is predominantly governed by the stiffness of the cellular steel profile. The proposed formulation for rotational stiffness is expected to enable more accurate estimations of the elastic critical moment. This advancement will support the development of a new parametric study aimed at deriving a comprehensive predictive model for this parameter, specifically tailored to the characteristics of composite cellular beams utilizing HSS and UHPC.