Summary Substructure identification is an effective decentralized structural health monitoring approach for large civil structures. Previously, the authors proposed a loop substructure identification method for shear structures, which utilized the dynamic equilibrium of a non‐top‐floor substructure to formulate a loop identification sequence (LIS), directly estimating the substructure's parameters by only using four structural acceleration responses. However, it was found that the LIS is conditional converged. To ensure the LIS's convergence, two different methods were previously investigated, but both methods have their limitations and may not guarantee satisfactory identification results under certain circumstances. In this paper, some virtual control systems (VCSs) are introduced into the loop substructure identification. The VCS is a self‐balanced system, consisting of some virtual control devices and the self‐balanced forces. The virtual control devices are combined with the substructure to form a controlled substructure that is used to replace the original substructure in the loop substructure identification. An in‐depth error analysis of the VCS‐based loop substructure identification was conducted herein, showing that the carefully designed VCS can tune the dynamics of the controlled substructure so that the convergence of the LIS can be easily achieved. Furthermore, a robust two‐step design strategy is proposed to obtain the optimal VCS's parameters with uncertain structural parameters. Finally, the numerical simulation study on a 20‐story shear building and the shake table tests on a five‐story bench‐scaled structural model were conducted to verify the effectiveness of the designed VCS to improve the convergence and identification accuracy of the LIS.

Vibration monitoring is one of crucial functions of structural health monitoring (SHM) systems. Traditional structural vibration monitoring usually relies on specialized sensors, data transmission and acquisition equipment, which are expensive and may not be easily available in urgently needed situations like post-disaster structural evaluation. Therefore, developing an affordable and efficient structural vibration monitoring technique becomes an important topic in SHM research. In this paper, the authors developed an android system APP that can easily convert multiple android smartphones into a wireless structural vibration monitoring system. To make the designed system reliable and easy to use, the server/client architecture is adopted. One smartphone is designated as the serve of the system to remotely control all other smartphones, which function as sensors to measure structural vibration. An efficient method is proposed herein to establish the smartphone-based structural vibration monitoring network, allowing the server smartphone to quickly and easily connect multiple sensor smartphones to form the wireless network for structural vibration monitoring. Additionally, a synchronization method is also proposed to synchronize different smartphones for simultaneously measuring structural vibration. To verify the time synchronization accuracy of the developed system, an experiment is designed and conducted. Moreover, a new analysis method of the time synchronization accuracy is also proposed, which verifies that the designed smartphone-based monitoring can achieve the millisecond-level time synchronization accuracy. Finally, a shaking table experiment is conducted on a three-story bench-scale structural model, the results of which demonstrate that the designed smartphone-based wireless structural vibration monitoring system can quite accurately identify the modal parameters of the tested structure.

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