Towards Mixed-Type Modelling of Structures with Slender and Deep Beam Elements

Concrete frame structures often include both slender and deep beams. Deep beams
possess a large shear capacity, and thus are typically used as transfer girders to carry
heavy loads over large spans. The overloading of such members due to extreme events
such as earthquakes may result in the collapse of the entire structure. To evaluate the
resilience of large frame structures under extreme loading, it is necessary to model the
interaction between the deep girders and the rest of the structure in an accurate and
computationally effective manner. To address this issue, this paper proposes a mixed-type
modelling framework by formulating an innovative 1D macro deep-beam element and
coupling it with 1D slender elements. The new macro element aims to combine the
accuracy of 2D micro finite elements with the simplicity of 1D macro elements. The
paper summarizes the formulations of this element, based on the three-parameter
kinematic theory, and integrates it into an existing global nonlinear analysis procedure to
create a mixed-type modeling framework. The verification study, including a frame
structure with a deep transfer girder, has shown that this approach captures the response
of the frame with an accuracy similar to that of 2D micro finite elements, while requiring
approx. 20% of the analysis time.