Improved real‐time force control for applying axial force to axially stiff members

Abstract

One of the challenges in real‐time dynamic testing is effectively controlling axial forces for axially stiff members such as columns, walls, and base isolators. Axial force has a significant influence on structural strength and post‐yield behavior, thereby maintaining proper axial force boundary conditions is crucial for accurate seismic performance evaluation. To overcome this challenge, a displacement‐based force control method using the adaptive time series compensator (D‐ATS) was developed in the existing study, but this method requires additional sensors such as displacement transducers and accelerometers to ensure the accuracy of force control. In this study, a new real‐time force control method is introduced, which eliminates the need for additional sensors beyond the default sensors available in a typical servo‐hydraulic actuator. Newly developed modules are also provided, which can satisfactorily estimate the velocity and force change rate of actuator, while effectively mitigating oil‐column resonance. Experimental validation is conducted using lead rubber bearings (LRBs) subjected to axial force and lateral movements. The results demonstrate the exceptional performance of the new force control method, offering a convenient and cost‐effective approach for applying axial forces in real‐time dynamic testing.