Kinematics-Based Modelling of the Cyclic Behaviour of Deep Shear-Critical RC Members

Nonlinear time history analysis is progressively becoming a common tool for seismic assessment of existing concrete structures. In many cases, existing structures do not comply with the principles of capacity design, and therefore can exhibit brittle global failure mechanisms and brittle shear failures that need to be captured by the analysis. At the same time, in order to analyse complex structures, there is a need for computationally efficient nonlinear models of various structural members. So far, most effort has been devoted to the development of such models for shear walls and slender frame elements (beams and columns), typically based on the plane-sections-remain-plane hypothesis and fibre discretization of the section. However, deep shear-critical members such as deep transfer girders in buildings, which do not comply with the classical beam theory assumptions, continue to require complex high-fidelity finite element models.
To address this issue, this study proposes an efficient yet accurate kinematics-based model for the complete cyclic behaviour of deep beams and other similar deep members. The model uses only four kinematic parameters (two in each loading direction) to describe the complete deformed configuration of deep shear spans with diagonal shear cracks, including the opening and slip displacements in the cracks. The kinematic conditions of the model are combined with hysteretic constitutive models for the shear-resisting mechanisms, as well as equilibrium conditions, to formulate a complete predictive approach. The paper discusses the formulation of the modelling approach and its validation with experimental data.