Comparative analysis of geometric imperfections and residual stresses on the global stability behavior of cantilever composite alveolar beams

Abstract

Few studies addressed the influence of geometric and structural imperfections of steel alveolar I-sections on the stability behavior of composite beams under hogging moment. Therefore, this paper aims to study the sensitivity to geometric imperfection amplitude and residual stress distribution on their global stability. The research primarily focuses on comparing numerical results with experimental data in detail, which addresses four tests involving cantilever composite beams with castellated and cellular I-sections. It includes applying various residual stress patterns and geometric imperfection values to advanced numerical analyses as documented in the literature. Linear buckling analyses (LBA) and geometrically and materially nonlinear analyses with imperfections (GMNIA) are carried out using the ABAQUS software. Regarding the first positive eigenvalue from LBA analyses, the eigenvectors presented Web-Post Buckling (WPB) with a slight compressed flange lateral curvature, inserted as the initial geometric imperfection in the GMNIA analyses. However, when the residual stresses were implemented in the GMNIA analyses, some finite element models had different failure modes regarding the deformed configurations from LBA analyses, in which the failure modes were characterized by Lateral-Distortional Buckling (LDB), which was in agreement with the test results. As the beams reached LDB in an inelastic regime, residual stresses significantly affected their resistant capacity. This way, the distribution of compressive residual stresses in the flanges had the most critical influence on the global stability behavior of the analyzed beams, as these residual stresses favor the LDB occurrence. Finally, higher geometric imperfection amplitudes did not provide only lower ultimate loads, as when the instability phenomena are reached in an inelastic regime, the effect of global geometric imperfections becomes highly complex.