The arterial stiffness evaluation is largely reported as an independent predictor of cardiovascular diseases. The central pulse waveform can provide important data about arterial health and has been studied in patients with several pathologies, such as diabetes mellitus, coronary artery disease and hypertension. The implementation and feasibility studies of a fiber Bragg grating probe for noninvasive monitoring of the carotid pulse are described based on fiber Bragg grating technology. Assessment tests were carried out in carotids of different volunteers and it was possible to detect the carotid pulse waveform in all subjects. In one of the subjects, the sensor was also tested in terms of repeatability. Although further tests will be required for clinical investigation, the first studies suggest that the developed sensor can be a valid alternative to electromechanical tonometers.
One of the early predictors of cardiovascular diseases, with growing interest, is the arterial stiffness which is typically
evaluated through the velocity and morphology of the arterial pressure wave.
In each cardiac cycle the heart generates a pressure wave which propagates through the arterial tree. Along its path, the
pressure wave interacts with the arterial walls and, consequently, the morphology of a local arterial pressure wave can be
assessed by the arterial distention movement. Due to its superficiality, proximity of the heart and high probability of
atherosclerosis development, the carotid artery has particular interest to be monitored.
In this work, the development of a non-invasive fibre Bragg grating (FBG) probe for the acquisition of the arterial
distention wave is presented. Comparing to traditional methods, optical FBG based sensors can offer many advantages,
namely, compactness, immunity to electromagnetic interference, high sensitivity, low noise and immunity to light source
intensity due to its codification in the wavelength domain.
The arterial movements induce strain on a uniform FBG, with the arterial distention pattern. The carotid pulse wave was
successful accessed in young human carotid artery, with an acquisition rate of 950 Hz, allowing a clear distinction of the
carotid pulse identification points.
A sensing head configuration and the necessary interrogation parameters to simultaneously measure strain and
temperature using a single FBG are presented and demonstrated. By writing the FBG in a linearly etched fibre, we were
able to use the information encoded in the peak wavelength and in the spectral width of the fibre Bragg grating. The
spectral width of the grating depends uniquely on the applied strain and is temperature independent. An uncertainty of
±15.26 με and ±1.92 ºC was obtained in the experimental verification.
This work reports a case study of a structural health monitoring (SHM) system combining large and micro scale
measurements installed in a 16th Century Church in Aveiro. This dual scale SHM system relies on a network of 24 fibre
Bragg grating (FBG) sensors to perform micro scale, high resolution displacement and temperature measurements in
several key points of the structure, while the large scale measurements are ensured by a scanning laser range finder. The
results demonstrate that the developed systems allow adequate monitoring of the evolution of deformation in buildings,
in different scales, keeping the visual impact in the structure reduced to a minimum and contributing for the
implementation of best practices for rehabilitation of historic and cultural heritage.
This paper presents a structural health monitoring system, based on fibre Bragg gratings, developed for the church of
Santa Casa da Misericordia of Aveiro. This system comprises 19 displacement sensors and 5 temperature sensors. All
the sensors were custom made according to the monitoring points' characteristics. The results obtained over the first
months are presented. The objective of this work is to gather data that will bring a deeper knowledge of how this
structure behaves and to help planning the recovering interventions in this historical building.
The use of fibre Bragg grating sensors to study mortars' dimensional variations during the setting process is reported.
When determining a mortar's potential to fissure, it's important to know its total retraction. This means it is necessary to
know not only the mortar's retraction after hardened, but also to know how much it retracts during the plastic phase.
This work presents a technique which allows to measure dimensional variations, either expansion or retraction, during
the whole setting process. Temperature and strain evolution during both plastic and hardened phase of the mortar were
obtained, allowing the determination of dimensional variations and setting times.
Due to its high-speed, ease of implementation and low operation costs, this technique will allow to get a deeper
knowledge of the effects of several additives on the mortar's behaviour, allowing to improve its mechanical properties
through the determination of the proper chemical composition.