The use of normative models under combined compression and bending for verification of concrete-filled steel tubes with high strength materials

Resumo

Buildings have been demanding increasingly slender pillars from projects, consequently increasing the demand for efficient and economical solutions. One of the solutions adopted is the use of high-strength concrete and steel and the optimization of sections for filled mixed tubular pillars, which has been widespread in European, American, and Asian countries; however, there is little application in Brazil's constructions. Verification of mixed pillars under flexo-compression can be done by simplified methods or analytical methods such as the method of deformation compatibility. The draft revision of ABNT NBR 8800:2023 introduces three simplified calculation models for flexo-compression verification, with limitations in its application for concrete with characteristic compression strength below 50 MPa and steel profile with yield strength below 450 MPa, as well as proposing polygonal lines to trace interaction curves. In this article, the simplified calculation models from the draft revision of ABNT NBR 8800:2023 are compared with experimental results from the literature of prototypes of circular tubular filled mixed pillar sections with concrete strength above 50 MPa and steel profile with yield strength above 450 MPa. For this purpose, a computational tool was developed in MATLAB that traces the interaction curves of the draft revision project of ABNT NBR 8800:2023. The suitability and conservatism of simplified methods were verified when using high-strength materials outside the normative range.