Abstract
The coverage intensity of sensors is the most important issue on structural health monitoring technique. The geometric configuration of sensors must be optimized based on coverage intensity with proper objectives. In this article, a novel algorithm for optimal sensor placement in various steel frames was evaluated. These frames including moment-resisting frame, moment-resisting frame with base isolation, and moment-resisting frame with base isolation with steel shear wall were selected for case studies. This approach was proposed based on combination of common optimal sensor placement algorithm and nonlinear time history analysis. A new method called transformed time history to frequency domain approach was evaluated to transform nonlinear time history analysis results to frequency domain and then the effective frequencies according the maximum range of Fourier amplitude were selected. The modified type of modal assurance criterion values can be achieved from modal assurance criterion with the exact seismic displacement. All of novel optimal sensor placement processes were done through FEM-MAC-TTFD code modeled and developed in MATLAB by authors of this article. The results show that there is good relative correlation between the sensors number and coverage intensity obtained with modal and modified modal assurance criterion approaches for moment-resisting frame system, but for integrated frame such as moment-resisting frame with base isolation and moment-resisting frame with base isolation with steel shear wall, the modified modal assurance criterion approach is better approach. There is no significant difference between coverage intensity of sensors for top joints between modal assurance criterion and modified modal assurance criterion approaches for moment-resisting frame, moment-resisting frame with base isolation, and moment-resisting frame with base isolation with steel shear wall systems ( R2 = 0.994, 0.986, and 0.724, respectively). It was found that if reference point is located in center of frame, there is significant difference between modal assurance criterion and modified modal assurance criterion approaches, and modified modal assurance criterion generated slightly better results.
Highlights
The main purpose of evaluating a novel approach for health monitoring of steel frames is to develop the existing modal assurance criterion (MAC) with worthier computational process and make the method more reliable regarding this issue. This criterion was carried out using the modal analysis (MA) and nonlinear time history analysis (NTA) to make modified type of MAC method and estimate the optimal sensor placement (OSP)
There are some obscurities, for example, how many sensors are necessary to detect damage in frame and what is the acceptable level of MAC value for optimize sensor placement
Results showed that MAC and Modified-MAC could accurately obtain optimal number of sensors
Summary
The smart sensors, remote sensing, and decisionmaking knowledge are used in structural health. The MinMAC method was evaluated via extending the MAC idea This algorithm[3] was proposed to ensure modal correspondence between the various mode shapes. The forward–backward combinational extension (EMAC)[4] and co-ordinate modal assurance criterion (COMAC)[5] were defined based on original MAC Another approach based on maximization of the determinant of the Fisher information matrix called effective independence (EI)[6,7] was utilized for the structural modal identification and optimization. For example, eigenvalue vector product (EVP)[11] and mode shape summation plot (MSSP),[12] were used through finding the maximum EVP and MSSP values These calculations were done in order to prevent the placement of sensors on nodal lines. The novel objective function of OSP process was evaluated with the combination of structure response and coverage intensity
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