Application case: prototype of radar tower structural health monitoring system

Abstract

Abstract. Industrial and civil structures like bridges, wind turbines, pipelines etc., are widely present in rural area. To maintain functionality of these structures, their condition is controlled using Structural Health Monitoring (SHM). SHM assists engineers in finding early structural defects like cracks, deformations, material deterioration, metal fatigue and so on. Monitoring can prevent accidents from happening by giving early warnings and a chance to perform necessary repairs and adjustments to the structure. It is efficient and economically reasonable to have possibility to perform planned repairs well ahead, instead of doing urgent fixing. What is more important, structural condition monitoring improves safety along with reducing maintenance costs. There are numerous non-destructive techniques (ultrasound, Fiber Bragg Grating, acoustic emission) applied for SHM, but the focus of this paper is on vibration-based methods, particularly -Operational Modal Analysis (OMA). The aim of the study is to validate SHM application possibility for a full scale industrial structure using the Operational Modal Analysis based SHM system. The system is designed as a cost-effective solution, mainly by using cheap piezo film deformation sensors and utilizing multi-patch OMA technique. A test was performed and modal parameters of the radar tower were obtained and compared with the FE model. The possibility to perform SHM on an industrial structure was validated.

Statistical Structural Integrity Control of Composite Structures Based on an Automatic Operational Modal Analysis — a Review

“…The sensing based on piezofilm sensors is a cost-effective SHM solution. They are much cheaper (about 10 euros/ piece) than accelerometers, which, for industrial applications, can cost hundreds of euros [36]. Accelerometers typically also induce mass loadings on structures and have a considerable size, thus affecting the modal and aerodynamic properties of structures.…”

“…• a low maximum working temperature (100°C compared with 135°C for a copolymer film). The addition of preamplifiers to a sensing element allow for long measurement cables [35,36]. It has been shown that there is a considerable scatter of sensitivity of individual transducers in sensor networks; hence, sensors with preamplifiers are not optimal for precise measurements.…”

“…Moreover, each individual transducer from a larger network should be calibrated individually, which is tedious [35]. Another problem is related to environmental conditions -it is reported in [36] that the humidity induced short-circuits in preamplifiers of piezofilm transducers, so that measurements cannot be reproduced. Authors of the same study also claim that preamplifiers can be severely damaged by strong electromagnetic fields.…”

“…In [35], a network of 32 uniformly distributed piezoelectric film sensors was used to measure the structural response of a scaled wind turbine model with a height of 1.75 m. The sensors were attached on longitudinal beams of a wind turbine tower using a double-sided elastic adhesive tape. The same measurement system was used on a full-scale 24-m-high airport radar tower [36]. Authors claim that, although measurements for the OMA procedure were successful, the preamplifiers for PVDF film sensors were unstable.…”

“…Comparison of Performance of PVDF Film Sensors and Other Popular Sensors Used in the SHM Applications[31][32][33][34][35][36][37] …”