Advancing seismic performance evaluation of steel moment frames using the MLS-OpenSees-RMC hybrid simulation platform

Hybrid simulation is increasingly used in earthquake engineering because it is efficient, flexible, and relatively economical. Nevertheless, it often requires high-performance computing devices with multi-core CPUs and high-speed memory and still involves substantial complexity in loading and controlling the physical substructure. To cope with such challenges, an MLS-OpenSees-RMC Motion Controller hybrid testing platform is proposed, featuring modular hardware to support hybrid simulations with varying structural parameters. An interruption-resilient communication interface is developed between OpenSees and the RMC75E controller. This mechanism enables the use of high-fidelity numerical substructures, reduces PC hardware requirements, and improves platform reliability. The communication test results show that, under the USB connection, the single-register and multi-register access times of the MLS-OpenSees-RMC platform are reduced by 96.3% and 94.3%, respectively, compared with the MATLAB middleware solution. In addition, the inner-loop displacement tracking error of the MLS-OpenSees-RMC generally remains within 5%, while the relative errors in the maximum displacement under outer-loop control are 12.75% and 0.39%, respectively. During the execution of hybrid simulation on a portable laptop (12th Gen Intel Core i5–12500H), a timeout zone is observed near the end of the displacement time history, but the system remains uninterrupted. Finally, the seismic performance of a steel frame is simulated. At the LS level, only limited plasticity develops at the end of the physical substructure, without the formation of a clear plastic hinge, and structural continuity is maintained. At the CP level, plastic hinges progressively form and local instability becomes evident, confirming the structural behavior associated with the two performance levels.