Journal of Infrastructure Intelligence and Resilience最新文献

This study aims to quantify Rayleigh scattering based measurement accuracy of distributed fiber optic sensors under a heating-holding load protocol and characterize the effect of polymer coating on the sensors as the polymer softens and melts away at elevated temperatures. Two segments of a coated single-mode optical fiber were loosely attached and firmly bonded to a steel plate, respectively. When locally heated up to 405 $°\text{C}$ in a furnace, the two segments were used to measure temperature alone and thermal-induced strain. The axial displacement associated with the strain measurement was compared with that of a dial gauge. A temperature increment of 13 ​°C (≪ 20 ​°C) is recommended to ensure successful correlation analysis of Rayleigh scattering signals. The polymer was found to start softening at 155 $°\text{C}$ and melting at 267 ​°C. As temperature sensors, optical fibers with an insulation sheath can accurately measure temperature untill 155 ​°C without and till 267 ​°C with thermo-mechanical analysis of sheath-fiber bonding behavior. As strain sensors, optical fibers with temperature compensation are accurate for strain measurement up to 155 ​°C, above which strain transfer analysis is required due to softening of the fiber coating. Under a large temperature gradient covering 155–267 °C, the fibers attached on steel plates with epoxy function like an extensometer as a center portion of the coating with the high-end temperature is melted as verified by microscopic analysis.

Phononic crystals that are artificially engineered structures have recently been introduced for vibration energy harvesting and sensing applications due to their unique features of band gaps and wave propagation control. Conventional energy harvesters made of phononic crystals are mainly designed for acoustic energy harvesting at a high-frequency vibration source (i.e., kHz levels). In this work, a defect-mode-induced energy harvester is designed for low-frequency excitations in the range of 0–300 ​Hz. The entire system that is a locally resonant phononic crystal (LRPC) plate with line defect patterns is consisted of elastic-wrapped core scatterers periodically embedded in epoxy resin. A two-dimensional (2D) three-component unit cell structure is arranged on the plate and the band gap property is analyzed to optimize the geometric parameters. Defects are then introduced to the LRPC plate with a 7 ​× ​7 point array for analysis. In addition, numerical and experimental studies are conducted to investigate the performance of energy harvesting when attaching a piezoelectric patch on the defect points. The results demonstrate that the proposed LRPC vibration energy harvester having a line defect mode (with continuous or alternate points) shows good performance in energy harvesting, in which a peak power output of 42.72 ​mV can be achieved under 10 ​m/s² and 252 ​Hz. The performance is almost 6 times more than that of the single-point defect model under the same excitation conditions. The present LRPC-type energy harvester with a line defect mode is more suitable for energy harvesting for low-frequency and broadband conditions.

Rapid structural inspections and evaluations are critical after earthquakes. Computer vision-based methods have attracted the interest of researchers for their potential to be rapid, safe, and objective. To provide an end-to-end solution for computer vision-based post-earthquake inspection and evaluation of a specific as-built structure, the concepts of physics-based graphics model (PBGM) and digital twin (DT) are combined to develop a graphics-based digital twin (GBDT) framework. The GBDT framework comprises a finite element (FE) model and a computer graphics (CG) model whose state is informed by the FE analysis, representing the state of the structure before and after an earthquake. The CG model is first created making use of the FE model and the photographic survey of the structure, yielding the virtual counterpart of the as-built structure quickly and accurately. Then damage modelling approaches are proposed to predict the location and extent of structural and nonstructural damage under seismic loading, from which photographic representation of the predicted damage is realized in the CG model. The effectiveness of the GBDT framework is demonstrated using a five-story reinforced concrete benchmark building through the design and assessment of various UAV (Unmanned Aerial Vehicle) inspection trajectories for post-earthquake scenarios. The results demonstrate that the proposed GBDT framework has significant potential to enable rapid structural inspection and evaluation, ultimately leading to more efficient allocation of scarce resources in a post-earthquake setting.