Fermandois, Gaston

This paper reviews the conceptual and technical advances in multi-actuator dynamic loading in modern structural testing. In particular, a focus is given to the developments and challenges in multi-axial hybrid simulation (maHS) and multi-axial real-time hybrid simulation (maRTHS), where a specimen is subjected to multi-directional dynamic loading by interacting with a numerical simulation of its surrounding structural subsystems and components. This review introduces the general framework for maHS and maRTHS, describing substructuring techniques, loading equipment, and nonlinear kinematics. In particular, the process of dynamic compensation for multi-actuator loading assemblies in maRTHS is explored. Different compensation architectures in the task (Cartesian) and joint (actuator) spaces are covered, and each alternative is assessed on its own merits for the dynamic synchronization of multi-actuator loading platforms. Finally, current challenges in maHS and maRTHS testing are identified, with recommendations for future research endeavors for the scientific community.

Real-time hybrid simulation (RTHS) is a powerful and highly reliable technique integrating experimental testing with numerical modeling for studying rate-dependent components under realistic conditions. One of its key advantages is its cost-effectiveness compared to large-scale shake table testing, which is attained by selectively conducting experimental testing on critical parts of the analyzed structure, thus avoiding the assembly of the entire system. One of the fundamental advancements in RTHS methods is the development of multi-dimensional dynamic testing. In particular, multi-axial RTHS (maRTHS) aims to prescribe multi-degree-of-freedom (MDOF) loading from the numerical substructure over the test specimen. Under these conditions, synchronization is a significant challenge in multiple actuator loading assemblies. This study proposes a robust and decentralized adaptive compensation (RoDeAC) method for the next-generation maRTHS benchmark problem. An initial calibration of the dynamic compensator is carried out through offline numerical simulations. Subsequently, the compensator parameters are updated in real-time during the test using a recursive least squares adaptive algorithm. The results demonstrate outstanding performance in experiment synchronization, even in uncertain conditions, due to the variability of reference structures, seismic loading, and multi-actuator properties. Notably, this achievement is accomplished without needing detailed information about the test specimen, streamlining the procedure and reducing the risk of specimen deterioration. Additionally, the tracking performance of the tests closely aligns with the reference structure, further affirming the excellence of the outcomes.

Abstract This study proposes a force-based real-time hybrid simulation (RTHS) framework with robust compliance-based adaptive compensation. Adding a compliance spring between the loading actuator and a rigid specimen is an alternative to measure restoring forces through load cells with significant noise. But, we considered compliance spring and load cell properties to be uncertainties. Robust adaptive model-based compensation will be employed to overcome force-tracking errors between substructures. The proposed methodology will be verified in a virtual RTHS environment, where parametric studies will be considered to check the system’s robustness over uncertain compliance and specimen properties.