Three-dimensional Modelling of Poorly Detailed RC Frame Joints
This paper presents preliminary work on three-dimensional numerical modelling of seismic strengthening measures for poorly detailed reinforced concrete frames, primarily designed for gravity loads, as was typical in seismic-prone countries before the introduction of more advanced seismic codes in the early 1970s. These buildings are at risk due to inadequate structural detailing, deficiencies in reinforcement anchorage and the absence of measures to prevent brittle failure modes. Representative beam-column joints tested experimentally at the University of Pavia are analyzed using a continuum finite element program specially developed for detailed modelling of fracture in quasi-brittle materials. The microplane material model with relaxed kinematic constraint is used for the concrete. In the first stage of this work, which is presented in this paper, the proper modelling of the behaviour of smooth reinforcement with hooked ends, as well as the accurate representation of brittle shear failure modes in joints, are of particular interest. In the second stage of the project, strengthening measures that incorporate post-installed anchors for connection to the existing structure will be assessed.