A 2D beam‐column joint macro‐element for the nonlinear analysis of RC frames

Abstract

Recent earthquakes have shown that the seismic behavior of noncode‐conforming reinforced concrete buildings are in several cases strongly affected by the nonlinear response and possible failure of the beam‐column joints. Beam‐column joint inelasticity is typically due to either shear cracking and failure of the central concrete panel or bond‐slip of the longitudinal steel bars. This paper proposes a new Joint with Hinges macro‐element capable of simulating the most important sources of nonlinearities in the joints. It consists of a quadrilateral central panel whose rigid edges are connected to the beams’ and columns’ end nodes through nonlinear finite‐length interfaces that represent the plastic hinge zones. The central panel deforms in shear only. The joint macro‐element accounts for the nonlinear shear response of the central panel, for the bond‐slip of the longitudinal rebars crossing the joint and for the nonlinear shear and flexural behavior of the plastic hinge zones of the beams and columns connected to the joint. The resulting model of the reinforced concrete frame is the assembly of nonlinear Joint with Hinges macro‐elements connected by elastic frame elements. The proposed formulation is applied in this paper to plane frames. Validation studies with results from available experimental tests on beam‐column joint subassemblages show the proposed model capability to predict the hysteretic responses and the failure mechanisms of connections with unreinforced joints and different beam reinforcement ratios.

Hyper‐reduced order models for accelerating parametric analyses on reinforced concrete structures subjected to earthquakes

“…A better modeling of concrete shearing could have been achieved using a 2D plane strain material law, even if modeling accurately shearing failure mechanisms still requires 3D finite elements linked to 1D steel reinforcements (Hervé‐Secourgeon et al., 2021), which was not addressed in this work. Multilayer plates or shells could also have been used to model membrane components (e.g., walls or slabs), as well as nonlinear macro elements to model the RC column/beam connections using homogenized properties that depend on the steel reinforcements (Pantò et al., 2021).…”

Unified Simplified Capacity Model for Beam-Column Joints into RC Moment Resisting Frame

“…Further studies [74] implementing this model on more complex structures (Finite Element Models (FEM)) have clarified many key factors in the behavior of beam-column RC joints. Other non-linear models based on rotational hinges have been refined [75], or macro-element models have been outlined [76], in order to simulate the ultimate behavior of the RC joints. However, this has led to complex and cumbersome FEM models, which are usually not acceptable for practitioners.…”