Description:FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
&
The Patents Rules, 2003

Claims:We Claim:

1. A system (100) for monitoring health of a load bearing structure (1), the system (100) comprising:
an optical fiber (2) comprising a plurality of Fiber Braggs Grating (FBG) sensors (3) is positioned around the structure (1);
a transceiver (4) communicatively coupled to each of the plurality FBG sensors (3), wherein the transceiver (4) is configured to:
transmit a laser pulse of a pre-defined wavelength to the plurality of FBG sensors (3) at defined intervals of time, and
receive a reflected wavelength from each of the plurality of FBG sensors (3); and
a control unit (5) communicatively coupled to the transceiver (4), wherein the control unit (5) is configured to:
convert, the reflected wavelength received by the transceiver (4) to a proportional strain value;
compare, the strain value with a threshold strain value; and
indicate, the health of the structure (1), on an indication unit (6), based on the comparison.

2. The system (100) as claimed in claim 1, wherein each of the plurality of FBG sensors (3) are provisioned in a core of the optical fiber (2).

3. The system (100) as claimed in claim 1, wherein the pre-defined positions of the plurality of FBG sensors (3) in the optical fiber (2) correspond to three different parallel planes of the structure (1).

4. The system (100) as claimed in claim 1, comprising a plurality of temperature compensating FBG sensors (3) to measure strain value in the structure (1) due to temperature variations.

5. The system (100) as claimed in claim 1, comprising the indication unit (6) is commutatively coupled to the control unit (5) and is at least one of audio indicator, visual indicator and an audio-visual indicator.

6. The system (100) as claimed in claim 1, wherein the indication unit (6) indicates the health of the structure (1) in form of at least one of charts, tables, diagrams and graphs.

7. The system (100) as claimed in claim 1, wherein the control unit (5) generates an alert signal through the indication unit (6), when the strain value exceeds the threshold strain value.

8. A method of monitoring health of a load bearing structure (1), the method comprising:
transmitting, by a transceiver (4), a laser pulse of a pre-defined wavelength through an optical fiber (2) at defined intervals of time, wherein the optical fiber (2) comprising a plurality of Fiber Braggs Grating (FBG) sensors (3) is positioned around the structure (1);
receiving, by the transceiver (4), a reflected wavelength of the laser pulse from each of the plurality of FBG sensors (3);
converting, by a control unit (5), the wavelength of the reflected laser pulse from each of the plurality of FBG sensors (3) to a proportional strain value;
comparing, by the control unit (5), the converted strain values with a preset threshold strain value;
indicating, by the control unit (5), the health of the structure (1) based on the comparison.

9. The method as claimed in claim 8, wherein the pre-defined positions of the plurality of FBG sensors (3) is defined based on finite element method of analysis of the structure (1).

10. The method as claimed in claim 8, wherein the finite element method of analysis of the structure (1) includes determination of points of maximum strain in full load and no load conditions of the structure (1).

11. The method as claimed in claim 8, comprising a plurality of temperature compensating FBG sensors (3), wherein the strain in the structure (1) due to temperature variations is measured through the plurality of temperature compensating FBG sensors (3).

12. The method as claimed in claim 11, wherein the control unit (5) is configured to determine a mechanical strain by compensating a strain in the structure (1) due to temperature variations based on signals received from temperature compensating FBG sensors (3).

13. The method as claimed in claim 8, wherein the indication unit indicates the health of the structure (1) in form of at least one of charts, tables, diagrams and graphs.

14. The method as claimed in claim 8, comprising the indication unit (6) commutatively coupled to the control unit (5), and is at least one of audio indicator, visual indicator and an audio-visual indicator.

15. The method as claimed in claim 8, wherein the control unit (5) generates an alert signal through the indication unit (6), when the strain value exceeds the threshold strain value.

Dated 13th day of March 2020

GOPINATH A S
IN/PA 1852
OF K&S PARTNERS
AGENT FOR THE APPLICANT

COMPLETE SPECIFICATION
[See section 10 and rule 13]

TITLE: “A SYSTEM FOR MONITORING HEALTH OF A LOAD BEARING STRUCTURE”

Name and Address of the Applicant:
TATA STEEL LIMITED, Jamshedpur, Jharkhand, India 831001.

Nationality: INDIAN

The following specification particularly describes the nature of the invention and the manner in which it is to be performed.
TECHNICAL FIELD

The present disclosure relates in general to the field of structural engineering. Particularly, but not exclusively, the present disclosure relates to the aspect of measuring strain in structures through Fiber Braggs Grating (FBG) sensors. Further embodiments of the present disclosure disclose a system for monitoring health of the structure from the strain measured through Fiber Braggs Grating (FBG) sensors.

BACKGROUND

Man-made objects such as buildings, machines, bridges, dams etc. may be broadly classified as structures. All of these structures have a fixed operational life and all of the structures are subjected to deterioration. The structural deterioration of the man-made objects are mainly due to factors like environment, corrosive fumes, excessive unforeseen load, fatigue, creep, aging etc. When a structure is subjected to such external factors over an extended period of time, the critical components or the key links of the structure may deteriorate and eventually cause the failure of the structure. These failures are catastrophic in nature and failure of critical structures such as bridges, dams, critical infrastructure in large manufacturing plants etc. may cause severe loss of human life and may also interrupt the production process in a business thereby causing damages to the value chain of the business. In view of the above, it has become very important to detect the deterioration in the structures and accordingly monitor the health of the structures using suitable non-destructive testing methods.

Visual inspection is one of the most versatile and powerful NDT method, and it is typically one of the first steps in the evaluation of a concrete structure. Visual inspection can provide a wealth of information that may lead to positive identification of the cause of observed distress. However, its effectiveness depends on the knowledge and experience of the investigator. Broad knowledge in structural engineering, concrete materials, and construction methods is needed to extract the most information from visual inspection.

Conventionally, inspection of the structure were usually performed by manual inspection. One of the common methods used for inspecting a structure manually is visual inspection. However, visual inspection has the obvious limitation that only visible surface can be inspected. Internal defects of the structure often remain undetected and such inspection methods do not make use of any quantitative information regarding the properties of the structure. Methods such as optical magnification provide a detailed view of the structure at different areas. Instruments such as magnifying glasses or microscopes are used to detect and inspect cracks in the structure. However, such methods fail to provide a detailed view and also fail to estimate the actual extent of damage or deterioration the structure is subjected to. The above mentioned methods of traditional inspection sometimes becomes impossible due to extent of the structure and human reachability. Also, the efficiency and accuracy of manual inspection on structures completely depends on the experience and knowledge of the investigator. Hence, it may be difficult to obtain consistent and accurate results through manual inspection of the structures.

With advancements in technologies, several wired and wireless techniques have been used to determine the health of the structure. Wired techniques such as impedance-based structural health monitoring are used. Electrical impedance is the measure of the opposition that a circuit presents to the passage of a current when a voltage is applied. Impedance-based structural health monitoring makes use of strain gauges. Strain gauge is a sensor whose resistance varies with applied force. Strain gauge converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured. When external forces are applied to a structure, stress and strain in the structure due to the external load are estimated by calculating the resistance offered by the gauges. However, the impedance-based structural health monitoring system uses complex hardware and cables that not only extend throughout the length of the structure but also extend through all the bends and supporting members of the structure. Strain gauges in metallic structures tend to be less accurate since, the calculation of resistance by the strain gauges is hampered by the magnetic field in large metallic structures.

Wireless techniques which make use of X-rays and gamma-rays to get visual images of interiors of structures such as steel cables, slabs etc. Wireless techniques such as vision based systems for monitoring the structural health are also used. Vision based systems for monitoring the structural health utilize multiple cameras that record the displacement of a bridge or a structure under load and no load conditions. Based on the recorded displacement inputs from the camera, the structural damage is detected. However, the operational aspects of such wireless techniques are expensive and complicated. Further, vision based systems for monitoring the structural health do not provide real time data. Instead, the bridge or the structure has to be in a loaded and a no-load condition for the system to indicate a damage in the structure.

The present disclosure is directed to overcome one or more limitations stated above or other such limitations associated with the conventional systems.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the conventional method and system are overcome by the method and the system as claimed and additional advantages are provided through the provision of the system as claimed in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a system for monitoring health of a load bearing structure is disclosed. The system comprises an optical fibre comprising a plurality of Fiber Braggs Grating (FBG) sensors is positioned around the structure. A transceiver is communicatively coupled to each of the plurality FBG sensors, where the transceiver is configured to transmit a laser pulse of a pre-defined wavelength to the plurality of FBG sensors at defined intervals of time. The transceiver also receives a reflected wavelength from each of the plurality of FBG sensors. A control unit is communicatively coupled to the transceiver and the control unit is configured to convert the reflected wavelength received by the transceiver to a proportional strain value. The control unit further compares the strain value with a threshold strain value and indicates the health of the structure on an indication unit, based on the comparison.

In an embodiment of the disclosure, each of the plurality of FBG sensors are provisioned in a core of the optical fiber.

In an embodiment of the disclosure, the pre-defined positions of the plurality of FBG sensors in the optical fiber correspond to three different parallel planes of the structure.

In an embodiment of the disclosure, a plurality of temperature compensating FBG sensors are provided to measure strain value in the structure due to temperature variations.

In an embodiment of the disclosure, an indication unit is commutatively coupled to the indication unit and the indication unit is at least one of audio indicator, visual indicator and an audio-visual indicator.

In an embodiment of the disclosure, the indication unit indicates the health of the structure in form of at least one of charts, tables, diagrams and graphs.

In an embodiment of the disclosure, the control unit generates an alert signal through the indication unit, when the strain value exceeds the threshold strain value.

In one non-limiting embodiment of the disclosure, a method of monitoring health of a load bearing structure is disclosed. The method comprises steps of a transceiver transmitting a laser pulse of a pre-defined wavelength through an optical fiber at defined intervals of time, wherein the optical fiber comprising a plurality of Fiber Braggs Grating (FBG) sensors is positioned around the structure. The transceiver further receives a reflected wavelength of the laser pulse from each of the plurality of FBG sensors. A control unit converts the wavelength of the reflected laser pulse from each of the plurality of FBG sensors to a proportional strain value. The control unit further compares the converted strain values with a pre-set threshold strain value and indicates the health of the structure based on the comparison.

In an embodiment of the disclosure, the pre-defined positions of the plurality of FBG sensors is defined based on finite element method of analysis of the structure.

In an embodiment of the disclosure, the finite element method of analysis of the structure includes determination of points of maximum strain in full load and no-load conditions of the structure.

In an embodiment of the disclosure, a plurality of temperature compensating FBG sensors are provided, where the strain in the structure due to temperature variations is measured through the plurality of temperature compensating FBG sensors.

In an embodiment of the disclosure, the control unit is configured to determine a mechanical strain by compensating a strain in the structure due to temperature variations based on signals received from temperature compensating FBG sensors.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Fig. 1 is a schematic representation of a system for monitoring health of a load bearing structure, in accordance with an embodiment of the present disclosure.

Fig. 2 illustrates a front view of a pipe conveyor with a plurality of FBG sensors, in accordance with an embodiment of the present disclosure.

Fig. 3 is a graphical representation shown in the form of a trend chart of data obtained from the plurality of the FBG sensors, in accordance with an embodiment of the present disclosure.

Fig. 4 is a graphical representation shown in the form of a spider chart of the data obtained from the plurality of the FBG sensors, in accordance with an embodiment of the present disclosure.

Fig. 5 illustrates a constructive interference of the incident laser pulse from several crystallographic planes, in accordance with an embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the system for monitoring health of a load bearing structure and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other devices for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to its organization, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such mechanism. In other words, one or more elements in the device or mechanism proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the mechanism.

Embodiments of the present disclosure discloses a system for monitoring health of a load bearing structure. Conventionally, inspection of the structure were usually performed by manual inspection. One of the common methods used for inspecting a structure manually is visual inspection. However, such methods fail to estimate the actual extent of damage or deterioration the structure with required accuracy.

Accordingly, the present disclosure discloses a system for monitoring health of a load bearing structure. The system comprises an optical fibre comprising a plurality of Fiber Braggs Grating (FBG) sensors that may be positioned are pre-defined places around the structure. In an embodiment, the FBG sensors may be positioned in three different parallel planes along the structure. The system includes a transceiver, which is communicatively coupled to each of the plurality FBG sensors. The transceiver may be configured to transmit a laser pulse of a pre-defined wavelength to the plurality of FBG sensors at defined intervals of time. The transceiver also receives a reflected wavelength from each of the plurality of FBG sensors. The system further includes a control unit that is communicatively coupled to the transceiver and is configured to convert the reflected wavelength received by the transceiver to a proportional strain value. The control unit further compares the strain value received from the FBG sensors with a threshold strain value and indicates the health of the structure on an indication unit.

The following paragraphs describe the present disclosure with reference to Figs. 1 to 5

Fig. 1 illustrates is a schematic representation of a system (100) for monitoring health of a load bearing structure (1). Here, in Fig. 1, only a part or section of the structure (1) is shown for simplicity, however, the present disclosure is applicable to the whole structure (1). The system (100) includes an optical fiber (2) cable which may run through the structure (1) in a defined orientation. Further, the core of the optical fiber (2) may be provisioned with a plurality of Fiber Braggs Grating (FBG) sensors (3) at pre-defined positions. The FBG sensors (3) are sensors produced by precise laser writing in the core of optical fiber (2) in a longitudinal direction. Initially, a finite element method of analysis may be conducted on the structure (1) whose health is to be monitored. The finite element method of analysis of the structure (1) may then be used for determining the points or positions where the structure (1) is strained to the maximum in full load and no-load condition. Accordingly, the FBG sensors (3) are oriented in the optical fiber (2) and the optical fiber (2) is further positioned around the structure (1). In an embodiment, the FBG sensors (3) may positioned at the points where the structure (1) is strained to the maximum in full load and no-load condition, as determined by the finite element method of analysis.
In an embodiment, the FBG sensors (3) may be positioned in three different planes (A, B and C) along the structure (1) and each plane (A, B and C) may comprise of five FBG sensors (3). Each of the above described three planes i.e. A, B and C may be parallel to each other. The positioning of the FBG sensors (3) along three different planes (A, B and C), ensures that a larger surface area of the structure (1) is encompassed and more accurate readings of the overall deformation in the structure (1) may be obtained. Further, one of the ends of the optical fiber (2) may be connected to a transceiver (4). In an embodiment, the transceiver (4) may send a laser pulse of predefined wavelength to the plurality of FBG sensors (3) and the transceiver (4) may also be configured to receive and analyse reflected wavelength from the plurality of FBG sensors (3). The transceiver (4) may further be connected to a control unit (5), which receives the reflected wavelength from the transceiver (4). In an embodiment, the control unit (5) may be configured to convert the reflected wavelength received from each of the plurality of FBG sensors (3) into a proportional strain value. The method of such conversion by the control unit (5) is detailed below.

One of the important features of the FBG sensors (3) is that refractive index and pitch of the grating of the FBG sensors (3) changes when the FBG sensors (3) are strained due to an external force. The FBG sensors (3) are strained when a load acts on the structure (1). The refractive index and pitch of the grating of the FBG sensors (3) changes proportionately with the load that acts on the structure (1). Thereby, the wavelength of the laser pulse that is reflected by the FBG sensors (3) also changes proportionately with the change in the refractive index and pitch of the grating of the FBG sensors (3).

Once the FBG sensors (3) are strategically oriented or positioned around the structure (1), the transceiver (4) that is connected to the plurality of FBG sensors (3) through the optic fiber (2) cable transmits a laser pulse of predetermined wavelength. The transmitted laser pulse travels through the optic fiber (2) cable to the plurality of FBG sensors (3). The refractive index and the grating of the FBG sensors (3) are configured to reflect a certain wavelength of the transmitted laser pulse known as the braggs wavelength. The reflected wavelength or the braggs wavelength is received by the transceiver (4). Under normal or no-load conditions, the reflected wavelength corresponds to refractive index and the grating of the FBG sensors (3). Further, when the structure (3) is loaded or when the structure (3) experiences an external force, the refractive index and pitch of the grating of the FBG sensors (3) changes proportionately with the load that acts on the structure (1). Accordingly, with the change in the refractive index and pitch of the grating of the FBG sensors (3), the wavelength of the laser pulse that is reflected by the FBG sensors (3) also changes proportionately. This change in wavelength of the reflected laser pulse from the FBG sensors (3) is received by the transceiver (4) and is further transmitted to a control unit (5). The control unit (5) converts the reflected wavelength into suitable strain values.

With reference to Fig. 5, braggs law describes the condition for constructive interference from several crystallographic planes of the crystalline lattice separated by a distance “d”
2dsin?=n? (1)
For ?=900 and n=1,

? = 2d (2)
Equation (2) is derived for vacuum, for silica fiber.
? = incident angle
n is an integer
? = wavelength
?B = 2µeff? (3)
where,
?B = Bragg wavelength
µeff = Effective refractive index of the fiber ? =Periodicity of the grating

From equation (3) it is clear that braggs wavelength or the reflected wavelength (?B) of an FBG sensor (3) is a function of the effective refractive index of the fiber (µeff) and the periodicity of the grating (?).
The longitudinal deformation of the structure (1) produced by an external force, may change the grating (?) and the refractive index (µeff) in the FBG sensors (3). Further, a variation in temperature can also change the above mentioned parameters (? and µeff).
Therefore, FBG sensors (3) are essentially a sensor for temperature and strain measurement. Further, by using an FBG sensors (3), measurements of strain, temperature, pressure, vibration, displacement, etc. may also be derived.
Further, differentiating equation (3) with respect to temperature change and length change and combining, sensitivity of the braggs wavelength with temperature, strain is obtained
??B/?B = (1 - ?e)?z + (a + ?)?T (4)

Where,
a = thermal expansion of silica
? = thermo-optic coefficient
???? = photo-elastic coefficient

Substituting the value of constants used for silica fiber with a germanium doped core the sensitivity of FBG sensors (3) with respect to temperature and strain can be derived as below:

???B
????

??? B
???

= 14.18 pm/0C (5)

= 1.2 pm/µ? (6)
For measuring only temperature, the FBG sensors (3) may be protected against strain which can be simply done by inserting the FBG sensor (3) into a small-bore rigid thermally conducting tubing which will prevent any strain in FBG sensors (3) and hence any wavelength shift that occurs can be attributed to be caused by temperature only.
For measuring only strain two FBG sensors (3) needs to be used in close proximity. One for measuring only temperature and other is for strain and temperature both. The wavelength shift produced by former is subtracted from the shift produced by latter and the resultant shift can be attributed to strain only.

The above calculated strain and temperature values at different positions of the structure (1) may be suitably indicated by the control unit (5) itself. In an embodiment, the control unit (5) may calculate as well as indicated the strain and the temperature measurements in structure (1). In an embodiment, the control unit (5) may further be connected to an indication unit (6) for suitably indicating the strain and the temperature measurements.

Fig. 2 is a front view of a pipe conveyor with a plurality of FBG sensors (3). The optical fiber (2) cable is positioned around the pipe conveyor and the FBG sensors (3) are mounted at different points around the pipe conveyor. The optical fiber (2) cable is oriented around the pipe conveyor such that the FBG sensors (3) are mounted at left chord (a), left supporting frame (b), right supporting frame (c), bottom chord (d) and the right chord (e) of the pipe conveyor.

Fig. 3 and Fig. 4 are graphical representation shown in the form of a trend chart and a spider chart respectively. The graphical representation shown in the form of charts are data obtained from the plurality of the FBG sensors (3) mounted around the pipe conveyor. The strain and the temperature experienced by the plurality of FBG sensors (3) at different positions of the pipe conveyor is calculated by the control unit (5) and may be suitably indicated by the control unit (5) or by the indication unit (6) in charts or graphs as seen from Fig. 3 and Fig. 4.

From the design calculations and FEM analysis, strain levels at different operating conditions and maximum allowable limit of the structure (1) may be determined and a threshold strain value may be derived. The strain range obtained from design calculations and FEM analysis forms the basis of abnormality detection. Any strain value calculated from the control unit (5), which is greater than the estimated threshold strain value, indicates the possible alarming situation. The control unit (5) compares the calculated strain values from the reflected wavelength of the FBG sensors (3), with the estimated threshold strain values. Accordingly, any strain value that exceeds the threshold strain value is indicative of an excess load or a damage to the structure (1). Consequently, the control unit (1) indicates any excessive load that acts on the structure (1). Also, in order to estimate the combined effect of strains at multiple points, the overall strain level in a reduced dimension is calculated using Principal Component Analysis (PCA). As seen from Fig.4, normal values of variables in the low dimension space of principal components are used to create a bounding polygon and whenever any value goes out of this polygon, alarm is generated by the control unit (5), indicative of the excessive load on the structure (1).

In an embodiment of the disclosure, the orientation of the FBG sensors (3), provides accurate strain readings of the structure (1).

In an embodiment of the disclosure, the system (100) enables the real time monitoring of the health of the structure (1).

Equivalents

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description.

Referral Numerals:

Referral numeral Description
1 Component/structure
2 Optical fibre
3 FBG sensors
4 Transceiver
5 Control unit
6 Indication unit
100 System for monitoring the health of the structure
a Left chord
b Left supporting frame
c Right supporting frame
d Bottom chord
e Right chord