Progressive collapse analysis of reinforced concrete frame structures using beam discrete macro-elements
Abstract
This paper proposes a new simplified computer-based procedure for the dynamic analysis of reinforced concrete frame structures. It contributes to a bette understanding of the complex mechanisms involved in progressive collapse, a phenomenon characterised by resulting damage disproportionate to the original cause. Unlike the usual simplified dynamic engineering analysis of progressive collapse, a Distinct Element Method is used. Such an approach can follow the structural behaviour from the initial localised damage to the total collapse while taking into account large displacement, multiple fractures and contact. The developed macroscopic discrete beam-column element uses an inelastic hinge formulation. It consists of two rigid bodies connected through flexible joints representative of the behaviour of constitutive materials. The use of macro-elements, equivalent to Timoshenko beam elements, significantly reduces computer time. Contacts are governed by a classical compliant model with Coulomb friction. Accurate and efficient detection of contacts is performed through the use of an Oriented Bounding Box tree. The equivalence, before members fractures, between the developed beam discrete macro-elements code and a classical beam finite element approach, is illustrated through a RC frame academic example. The ability of the proposed procedure to describe complete collapse is shown with another RC frame academic example. All the beams and columns were modelled with a bilinear moment-curvature relationship and a critical bending moment for element separation.