Stress-Strain State of Nodal Joints of Reinforced Concrete Structures under Static-Dynamic Deformation

Abstract

A method is proposed for a more rigorous assessment of the stress-strain state parameters in structurally and physically nonlinear systems of reinforced concrete frames of multi-story buildings under extreme conditions during structural transformations caused by special impacts. The specific effects of nodal joint ductility, depending on the failure mode of the cross-section and the level of operational load, on the ability of a monolithic reinforced concrete structural system to resist potential progressive collapse due to the failure of a ground-floor column have been identified. The stress-strain state of the examined structural system is determined with consideration of both physical and geometric nonlinearities in the behavior of structural elements. At the same time, dynamic overloads in the structural elements are calculated using a direct dynamic method by integrating the equations of motion while accounting for damping forces. Parametric points characterizing the performance of nodal joints are identified using diagrammatic analysis methods. The obtained results show that taking into account the compliance (flexibility) of the joints has a significant impact on the assessment of criteria for a special limiting state, particularly in sections where concrete failure occurs and falls within the range of 30% to 45%, depending on the level of operational load.