Nonlinear finite difference analysis of reinforced concrete building columns under vehicular impact: application to brazilian design practice

Abstract

Abstract Vehicle collisions with building columns can cause severe consequences to the structural integrity of both the element and the overall structural system, requiring adequate analyses in accordance with current technical standards. This study aimed to develop and validate a computational tool for nonlinear analysis of reinforced concrete columns subjected to vehicle collisions, as well as to evaluate current Brazilian design practices for this type of action. The methodology employed the Finite Difference Method coupled with the Dirac Delta function for applying concentrated equivalent static forces, utilizing the N-M-1/r diagram to account for material physical nonlinearity. The effect of axial force on the member curvature is considered. The program was validated against reference cases from the literature and applied to case studies involving low- and mid-rise buildings, with columns subjected to different axial load levels. Results showed discrepancies of about 5% compared to reference solutions, confirming the model’s accuracy. Structures with low axial loads exhibited greater vulnerability to collisions, requiring a considerable increase in the longitudinal reinforcement, whereas columns with moderate loading demanded lower strengthening. This structural vulnerability was quantitatively evaluated through a proposed Impact Safety Factor (ISF), which measures the cross-section’s reserve capacity under combined bending and compression. Comparison between the developed tool and the Nominal Curvature Method revealed differences between 6.6% and 18% for low-slenderness columns. The developed tool fills a gap in Brazilian structural engineering practice by combining low computational cost with refined analysis, overcoming limitations of simplified methods in commercial software and providing a robust alternative for verifying columns under vehicle impact.