Abstract
Structural health monitoring (SHM) systems using modal- and vibration-based methods, particularly wireless systems, have been widely investigated in relation to the monitoring of damage states in civil infrastructures such as bridges and buildings. Unlike many current efforts in developing wireless sensors, one can instead leverage the suite of sensors, network transmission, data storage, and embedded processing capabilities built into modern smartphones for SHM. The objective of this work was to assess and validate the use of smartphones for the monitoring of artificial damage states in a three-story steel frame model subjected to shaking table-induced earthquake excitations. The steel frame was a 2D structure with six rotary viscous dampers installed at the beam–column joints, which were used for simulating different damage states at their respective locations; the columns were also replaced with ones of reduced cross-sectional areas to further emulate damage. In addition to instrumenting the frame with conventional tethered sensors, Apple iPhones (pre-loaded with customized smartphone apps to record acceleration and inter-story displacement) were also installed. Shaking table tests were then conducted on the undamaged and damaged frames, while conventional sensors’ and smartphones’ responses were collected and compared. Wavelet packet decomposition was employed to analyze the acceleration data to detect damage in two different cases. Structural displacements were also computed from acceleration measurements and compared with displacement measurements to further validate the quality of smartphone sensor measurements.
Highlights
IntroductionExtreme events such as earthquakes can cause severe damage to structures, and an event can occur at any time during the structure’s operating service lifetime [1,2]
Extreme events such as earthquakes can cause severe damage to structures, and an event can occur at any time during the structure’s operating service lifetime [1,2].For example, the 2011 Christchurch earthquake caused ~11 to 15 billion US dollars in economic losses [3,4]
The wavelet packet analysis method is used in this paper
Summary
Extreme events such as earthquakes can cause severe damage to structures, and an event can occur at any time during the structure’s operating service lifetime [1,2]. The 2011 Christchurch earthquake caused ~11 to 15 billion US dollars in economic losses [3,4]. Another example is the 2011 Tohoku earthquake, which caused nearly 30,000 casualties [2] and ~195 billion US dollars in losses. The assessment of structural performance, before, during, and after an extreme event, is critical for ensuring their safe operations and resiliency to natural hazards such as earthquakes. Maintaining civil infrastructure systems’ optimal performance is necessary for preventing structural
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