Hybrid Testing Approach for Thermo-Mechanical Testing of Structures Using Impedance Matching

Understanding the behavior of a structure at an elevated temperature is very important for the development of fire-resilient infrastructure. Current testing methods are based on element-level testing to obtain the standard heat resistance curve. The major drawback of element-level testing is that it does not consider the interaction of the test specimen with the surrounding structure and thus does not provide an accurate picture of the structural behavior. This paper proposes hybrid thermo-mechanical testing which promises more realistic response evaluation as opposed to current testing methods. Hybrid thermo-mechanical testing couples the test specimen subjected to elevated temperature (physical substructure, PS) with the computational model (virtual substructure, VS) of the surrounding structure. A transfer system (TS), in the form of an actuator, is used to realize the interaction between the two substructures. The controls for the TS are designed in such a way that it mimics the dynamic behavior of the surrounding structure. The controls for the TS are designed using impedance matching. The proposed methodology is applied to a case of coaxial bars fixed at both ends. It is found that the controller designed based on impedance matching results in a TS whose dynamics are close to that of the VS. This ensures that the interactions between the two substructures are captured accurately during the hybrid thermo-mechanical testing.