Hybrid simulation with multiple synchronized substructures as virtual fire-exposed models and physical specimen in laboratory

Fire tests have been used to provide a guidance on the design and analyses of steel structures subjected to fire. However, conducting full-scale fire tests on structures is costly, leading to the practice uncommon. Hybrid fire simulation (HFS) approach enables testing fire-exposed elements as substructures, while considering their boundary condition by system-level numerical model. In previous studies on HFS, an isolated fire-exposed specimen is always adopted as a specimen or a separate program. As multiple structural members may be subjected to fire exposure, this paper introduces an advanced HFS approach that employs a 2D/3D steel frame structure model for global behavior, synchronized with multiple virtual fire-exposed models and simultaneously laboratory test on a column specimen at ambient temperature. High-fidelity numerical models using shell elements were employed to reproduce the structural performance of fire-exposed column in a virtual HFS environment, while the physical tests were performed in a real HFS environment. Furthermore, the effects of column's axial stiffness and composite floor system are discussed using the proposed virtual HFS strategy. This paper is to validate the cyber-physical interface between a structural model in OpenSees for fire and a real specimen with MTS servo system. This is the first time to perform synchronized tests with OpenSees for fire, and enabling simultaneous operation of a virtual sub-structure model of high resolution with a structural system model and a physical specimen. This study serves as a key step of developing HFS based on the open-source tools OpenSees for fire and OpenFresco, which will facilitate the hybrid testing as next step to include the tests on physical specimens with synchronized thermal loading.