Oya Mercan’s research while affiliated with University of Toronto and other places

This paper presents a comprehensive investigation on the seismic control efficiency and response prediction for a hybrid isolation system, incorporating hysteretic damping (HD) and viscous damping (VD) devices. Based on a set of full-scale dynamic tests on a representative industrial building structure, the efficiency of two typical base isolation systems (BISs), namely, BIS with HD (BIS-HD) and VD (BIS-VD), is first validated and seismically compared. A three-dimensional finite element model along with a simplified single-degree-of-freedom (SDOF) model are subsequently developed and verified under various earthquake scenarios. The novelty of this study primarily lies in the development of a consistent design procedure that facilitates a parametric comparison on the seismic performance of both BIS-HD and BIS-VD systems using the validated SDOF model. The results confirm the superior isolation performance of BIS-VD when designed with a short period and high nonlinear damping exponent. Conversely, the BIS-HD exhibits superior acceleration control and moderate displacement control efficiency, albeit with the drawback of excessive permanent residual displacement. Secondly, this study proposes a simplified prediction method for an optimal hybrid isolation technique combining HD and VD devices, aimed at enhancing the structural response control efficiency and prediction accuracy. Nonlinear time history analyses validate this method, showing high fidelity in capturing the peak relative displacement absolute acceleration responses. With the comparison and combination of HD and VD devices, the design procedure and prediction method provide alternative options for improving the seismic design of a typical industrial building structure with hybrid isolation systems.

As buildings become taller and slenderer, managing their vibrational response and mitigating it pose significant challenges in design. Tuned liquid dampers (TLDs) are liquid (usually water)-filled tanks that can mitigate structural vibrations by leveraging the sloshing motion of the contained fluid. However, the dynamic behavior of TLDs and their interaction with structures is complex. While most research on TLDs has focused on mitigating wind-induced vibrations, less attention has been paid to their seismic control of structural responses. Moreover, existing literature on the experimental research involving TLDs mostly pertains to small-scale models. This study aims to experimentally explore the effectiveness of large-scale TLDs in mitigating vibrations in both linear and nonlinear structures under seismic loads. A real-time hybrid simulation is employed as the experimental method, where only the TLD is physically constructed and tested, while the rest of the system is simulated numerically in a coupled manner, allowing for obtaining the dynamic response of the structure equipped with the TLD in real time. This approach offers the flexibility to significantly scale up the TLD size for physical testing while exploring various TLD-structure scenarios by numerically adjusting the structural properties within the simulation.

Buckling-restrained braces (BRBs) are effective and widely used devices to enhance the seismic performance of steel moment resisting frames (SMRF), but they might fail to prevent significant structural damage or structural collapse under unexpectedly high seismic loads. To address this issue, a novel hybrid BRB (HBRB) composed of a conventional BRB and a friction damper in series is proposed, where the activated force/displacement of the friction damper could be adjusted to protect the HBRB from failure. The paper begins by providing a detailed explanation of the configuration and working principle of the proposed HBRB. The cyclic behavior of the HBRB is thoroughly analyzed both theoretically and numerically. Building on this, a performance-based design approach is developed, focusing on enhancing the seismic response of SMRF using the HBRB. To assess the effectiveness of the proposed HBRB and design method, two typical SMRFs, one with 9 stories and the other with 20 stories, are enhanced with the HBRB. Comprehensive numerical models are established, considering the bare SMRFs, HBRB-enhanced SMRFs, and conventionally BRB-enhanced SMRFs. Nonlinear static and dynamic analyses are conducted to evaluate the seismic performance of these steel frames. Special attention is given to the performance comparison between HBRB-enhanced SMRFs and conventionally BRB-enhanced SMRFs, specifically under the extremely rare earthquake (ERE) scenario. The results highlight that the HBRB can achieve comparable energy dissipation capacity to conventional BRB while displaying superior energy dissipation efficiency. Moreover, the proposed design method achieves the predefined seismic performance objectives for the enhanced SMRFs in a straightforward and time-efficient manner. Furthermore, the HBRB proves effective in eliminating the failure risk associated with conventional BRB under ERE conditions, effectively mitigating structural damage and preventing collapse.

Real‐time hybrid simulation (RTHS) is an innovative experimental testing technique that tests only some structural components for which accurate numerical models do not exist (i.e., experimental substructure), while modeling the rest of the structure numerically (i.e., numerical substructure). Conventionally, the two substructures in RTHS are executed at the same rate and interact in real time. Multi‐rate real‐time hybrid simulation (mrRTHS) is a modification of RTHS where different time step sizes are applied to the numerical substructure computation and the actuator control. This configuration provides a larger allowance for real‐time execution, thereby enabling the use of higher‐fidelity numerical models in RTHS. However, it complicates the data transmission between the substructures and introduces an additional time delay. The increased delay consists of communication and computational delays, which are independent of actuator dynamics. This study compares the data transmission within RTHS and mrRTHS configurations and confirms that mrRTHS experiences a larger delay error. To improve the accuracy of mrRTHS, a time‐varying interpolation built with Chebyshev polynomials is used. Additionally, a compensation strategy based on an adaptive discrete feedforward controller is introduced to compensate for actuator‐induced tracking errors and the increased time delay in mrRTHS. A demonstrative experimental study is conducted to investigate the seismic behavior of a large‐scale base‐isolated structure equipped with gyromass dampers. The results indicate that the proposed mrRTHS compensation strategy facilitates a more realistic assessment of the dynamic performance of structural systems by employing higher‐fidelity numerical substructures in mrRTHS.

Real-time hybrid simulation (RTHS) is an economical and reliable method for the evaluation of structural dynamic performances, and the fixed analytical substructure model is often used in RTHS which may affect the accuracy of results. In this study, a real-time hybrid simulation platform (RTHSP) developed by configuring a generic National Instruments (NI) controller with hybrid programming strategy is presented in detail. The dynamic performances of a scaled base isolated structure, where the unscented Kalman filter (UKF) was used to update the analytical substructure Bouc–Wen model during the RTHSs was evaluated by presented RTHSP. RTHS of a base-isolated structure was performed where a lead rubber bearing (LRB) was tested physically as the experimental substructure of a part of the isolation layer and the superstructure with the rest of the isolation layer model updated by UKF was considered as the analytical substructure. Under the excitation of three natural earthquakes, the RTHSs with and without UKF updating were compared and analyzed the differences between the two. The results indicated that the displacements of experimental substructure generated by RTHS with UKF updating are the largest, while the relative displacements and acceleration of superstructure are the smallest overall, and the dynamic characteristics of the isolation layer of the analysis substructure updated by UKF are different from that without updated, which reflected the more authentic dynamic mechanical performance of the base-isolated structure under earthquake excitation. In addition, the RTHSP and the hybrid programming strategy are verified to be reliable in tests and experiments, and the components and implementation of a RTHSP for base-isolated structures is described in detail, providing a reference for research on RTHS method.