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In real-time hybrid simulation (RTHS), a simulated structure is split into two substructures: one being a physical specimen, and the other a numerical model of the rest of the structure. These are connected in a real-time feedback loop to simulate the dynamic response of the combined structure. An issue in RTHS is the delay in the response of the servo-hydraulic actuators applying the displacements which can destabilise the feedback loop. The delay can vary significantly during the simulation, predominantly due to nonlinearity of the tested specimen. This thesis presents work developing and testing RTHS procedures, which are used to simulate buildings fitted with buckling-restrained braces (BRBs) as the physical substructure. An improved version of the well-known Adaptive Time Series (ATS) delay compensator is presented, retaining the performance of the original but significantly improving its computational efficiency. An online stiffness simulator is then presented which ensures stable force feedback using a continually updated numerical model of the BRB response. Accuracy is further improved by correcting for rig flexure using feedback from encoders measuring the BRB extension. Finally, a numerical model of the BRB is created which is then used in a multi-degree-of-freedom model. The performance of the modified ATS compensator and rig flexure correction was demonstrated through predefined displacement tests, achieving excellent displacement accuracy. This was combined with a single-degree-of-freedom numerical substructure and the stiffness simulator to form a RTHS system showing excellent accuracy and stability up to high frequencies – the compensator adapting effectively to changes in delay caused by yielding. A multi-degree-of-freedom numerical substructure was then implemented to simulate the nonlinear response of realistic structures designed to Eurocode 8. Finally, the system was applied to RTHS with a viscoelastic damper, demonstrating the versatility of the adaptive system. |
