1,720,995 research outputs found
Temperature-compensated FBG-based sensor with variable sensitivity
No full textIn this paper a FibreBraggGrating (FBG)-based sensor device for strain measurement with adjustable
full-scale sensitivity is proposed. Installation flanges of the sensor can be moved with respect to the
internal fixed FBG sensing length in order to adjust the overall strain sensitivity and the full scale
measurement range of the device. Thermal drift is compensated using a technique based on the thermal
expansion of a solid block connected to the fibre, in the pre-stressed region outside the grating. Typical
calibration curves are reported to illustrate the sensor sensitivity variation with the layout and
temperature
The role of quality control and of long-term monitoring in the structural applications of composite materials
No full textThe progressive diffusion of FRP materials for structural strengthening and reinforcement purposes is increasingly pulling the demand of specialized testing procedures aimed to assess the quality of the installation work and the durability of the intervention.
This paper introduces some critical aspects of FRP applications and presents an overview of the quality control techniques that are suggested by the Italian standard specifications. Specific non-destructive testing techniques are presented in real case studies as well. In addition, the usefulness of structural health monitoring applied to FRP applications is considered and discussed
Recent Advancements and Relevant Applications of a Smart-FRP Material for Structural Health Monitoring Featuring Brillouin Fiber Optic Distributed Strain Sensing
No full textCrack Monitoring in Michelangelo’s David
Get PDFThis paper summarizes the results of a monitoring program which has been carried out
between 2010 and 2012 with reference to some cracks observed in the lower part of the
Michelangelo’s David, one of the most famous masterpieces of western art, located inside
the Galleria dell’Accademia of Florence. A monitoring system based on Bragg Grating
fiber optic sensors has been adopted. In addition, the application of the ultrasonic
technique in the analysis of the critical zone between the left foot and the pedestal of the
statue is described
Distributed Strain Measurement in Steel Bridge with Fiber Optic Sensors: Validation through Diagnostic Load Test
No full textFiber optic sensing technologies are emerging as valid alternatives for the health monitoring of civil structures. Distributed sensors based on Brillouin scattering add the unique capability of measuring strain and temperature profiles along optical fibers. Measurement is performed by establishing the correlation between fiber strain and temperature, and the frequency shift of the Brillouin backscattered light induced by a monochromatic light pulse. The technology holds potential for use on large structures and integrated transportation infrastructure. Its effectiveness has been assessed through scaled laboratory experiments, whereas field validation is limited to very few demonstration projects conducted to date. This paper presents a pilot application of Brillouin optical time domain reflectometry to measure strain profiles along the steel girders of a continuous slab-on-girder bridge subjected to diagnostic load testing. One of the exterior continuous girders required heat-straightening after falling during construction due to wind. The significance of applying a distributed measurement technique lies in the potential to assess the global girder response, which would be impractical and uneconomical using discrete measurement techniques. A 1.16 km long sensing circuit was installed onto the web of four girders. The circuit comprises bare optical fiber sensors, and a novel adhesively bonded fiberglass tape with embedded sensing fibers for strain measurement and thermal compensation. The strain profiles were first converted into deflection profiles and validated against discrete deflection measurements performed with a high-precision total station system. Structural assessment based on comparison of the strain profiles with the results of three-dimensional finite-element analysis of the bridge superstructure, and with specification mandated criteria, indicated that the response of the girder under investigation was within the design limits, and did not pose serviceability concerns. Factors that may affect measurement accuracy are finally discussed on the basis of the experimental and numerical results
Una panoramica di recenti applicazioni di monitoraggio di ponti con sensori a fibre ottiche distribuiti di tipo Brillouin
No full textDistributed Strain Measurement in Steel Slab-on-girder Bridge via Brillouin Optical Time Domain Reflectometry
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