Modeling reinforced concrete structures under fire conditions in GiD-OpenSees: Framework, validations, and implications

This paper presents modifications to the OpenSees for fire source code and the GiD-OpenSees interface to facilitate finite element (FE) macro modeling of reinforced concrete (RC) structural frames under fire conditions. In the FE framework, RC frames are discretized by 1-D line elements, and their cross-sections are further discretized by 2-D FE mesh. The mechanical analysis is configured for 1-D line elements, whereas the heat transfer analysis handles 2-D FE meshes. New material models (DamagePlastictyConcreteECT and DPMsteelECT) are developed based on the EN1992-1-2 stress–strain relations, and they explicitly consider transient creep (concrete), damage-plasticity (concrete), and plasticity (steel). Such an approach enables precise modeling of irreversible strain components, especially during strain reversal conditions. The existing GiD-OpenSees interface is extended to implement the new material models, FE framework, and automated thermo-mechanical analysis. Six numerical examples are presented, which include experimental validations and a comparison study against standard structural fire simulation software SAFIR. The results show that the developed framework is able to trace the structural response under fire to a high level of fidelity and robustly traverses strain-reversal conditions.