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Fiber Bragg grating (FBG) sensors demonstrate great potentials for structural health monitoring of civil structures to ensure their structural integrity, durability and reliability. The advantages of applying fiber optic sensors to a tall building include their immunity of electromagnetic interference and multiplexing ability to transfer optical si...
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... FBG sensors were deployed on various bridges to monitor strain, displacement, and temperature fluctuations [106,107]. FBG sensors were utilized in both high-rise buildings [93], smart civil structures [108], and dam infrastructures. For high-rise buildings, these sensors monitored seismic effects, helping to assess the buildings' resilience against earthquakes. ...
Fiber Bragg grating (FBG) sensors have emerged as advanced tools for monitoring a wide range of physical parameters in various fields, including structural health, aerospace, biochemical, and environmental applications. This review provides a comprehensive overview of FBG sensor technology, focusing on their operating principles, key advantages such as high sensitivity and immunity to electromagnetic interference, and common challenges like temperature-strain cross-sensitivity and the high cost of interrogation systems. Additionally, this review compares FBG sensors with other sensing technologies and highlights recent innovations in design, packaging, and implementation techniques. Finally, future research directions are discussed to enhance the performance, scalability, and long-term reliability of FBG-based sensing systems.
... In 2008, an 18-story Dongsheng Garden A5 building, located in Fushan Bay Area (Qingdao, China), was monitored during the construction period to analyze temperature and strain change in the vertical underground column and the first floor beam during the pouring and curing of concrete and the construction of subsequent upper floors of the building [10]. The structure health monitoring a group of columns of a high-rise building in Punggol EC26 (Singapore) was carried out in order to fix uneven settlement using long-gauge fiber optic sensors [11]. Distributed fiber optic cable was embedded in a 51 m long cast-in-place pile at a high-rise building construction site in London. ...
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Abstract
Fiber optics are increasingly being used in structural health monitoring applications. In addition to the well-known advantages, they most reliably transmit the stress–strain condition of the structure in the long term. This article presents the results of structural health monitoring on the embedding of fiber optics in the upper layer of the raft over the entire area of a high-rise building in Astana city (Kazakhstan), including the 75-storey 320 m block R. Temperature and strain data were collected constantly via a distributed fiber optic strain sensing system (DFOSS). The analysis of strains in fiber optic chainage indicated that the compression strains were observed over the entire area of the building, with values from −20 to −40 µε and with progression of the compression loaded up to −80 µε along the core wall closer to the eastern facade of the building. Tension strains were concentrated along the extreme axes of the building, with a predominance in the southern part of the R block, as well as in the immediate vicinity of the columns, in a range of −20 to −40 µε, with separate spots from −40 to −60 µε. Individual patches of tension strains near the columns have been explained by the increased deflection of the raft under the application of a concentrated load (columns). Fiber optic monitoring results at the time of testing did not exceed the permitted values for high-rise building operation; however, they characterized the general picture of the strain in the raft plane and made it possible to determine the initiation of cracks in concrete at an early stage.
... However, the strain measurements from the distributed optical fiber sensors cannot always accurately reflect the strain of the host material due to the existence of the protective layer of optical fiber sensors. This problem has been studied by many scholars, and the shear deformation of the protective layer is generally considered to be the reason for the inconsistency between the strain of the fiber core and the strain of the measured structure [4][5][6][7][8][9]. ...
Distributed optical fiber sensing techniques have been widely utilized in the field of structural health monitoring (SHM) of civil structures. However, strain measurements from distributed optical fiber sensors cannot always accurately reflect the strain of the host material of structures due to the coupled effects of the composite protective layer of the cables and the quality of the surface bonding construction. To address this issue, a method is proposed for correcting the strain data for civil structures measured by surface bonded distributed optical fiber sensors. The layered analysis method is used to establish a strain transfer model from the fiber core, through the inner protective layer, rigid protective layer, outer protective layer, and adhesive layer to the host material of the structure. With the new method, the strain transfer coefficient from the fiber core to the host material of the structures is calculated by updating the shear lag parameters based on a finite element model with a specific bonding length. The results of an experimental model and an actual bridge show that, comparing with the current methods, the proposed method effectively improves the accuracy of strain data from the distributed optical fiber sensors. The proposed method is benefit for the application of distributed optical fiber sensing techniques in monitoring the condition of actual civil structures.
... One possible low-cost sensing method, Fiber Bragg Grating (FBG)-based strain sensing, has been widely researched for the last few decades [5] due to its multi-functionality, relatively small size, and low production cost [6]. The stress sensing performance of FBG has been validated in both labscale tests [7][8][9] and full-scale applications [10][11][12]. Selfsensing smart concrete known as self-sensing composite has also been attracting interest in the civil engineering field [13]. Its functionality has been improved through the embedding of various materials such as carbon fiber [14,15], carbon black [16], carbon nanotube [17,18], steel fiber [19,20], micro wire [21], and so on. ...
Photoluminescence piezospectroscopy (PLPS) is a laser-based noncontact and nondestructive stress measurement technique but has not been studied extensively in the field of civil structural health monitoring. Using the PLPS technique, the stress level can be measured by emitting a laser source onto a target’s surface. In this study, PLPS was attempted for noncontact stress measurement of concrete. Alumina is one of the chemical components of Portland cement, and is a highly sensitive material for PLPS. Therefore, alumina in concrete can be used as a passive stress sensor by PLPS. To investigate the spectral detectability at different alumina rates, cement mortar specimens were prepared with increasing concentrations of additional alumina. It was determined that spectral detectability increases with increasing alumina concentration. Then, uniaxial compression tests were conducted to investigate the relationship between stress level and spectral shifts. It was ascertained that compressive stress and spectral shifts have a negative linear relationship. Then, the effective piezospectroscopic coefficients were calculated to be − 0.1574 cm−1/MPa and − 0.1468 cm−1/MPa for the R1 and R2 bands, respectively. The experimental results reveal that application of PLPS to concrete can provide essential information for structural health monitoring and allow for preventive measures to be taken before collapse of cement structures.
... Alternatively, Fiber Bragg Gratings (FBGs) may be used for detection of the resin flow. Usually, FBGs are embedded within structural materials because they respond to mechanical strains quite sensitively, thereby allowing, for instance, monitoring the structural health of buildings [107]. In the case of online monitoring the resin flow during processing, optical fibers that contain a Bragg grating are embedded within the molded material; upon illumination with light from a broadband source, the so-called Bragg wavelength is reflected back. ...
Process analysis and process control has attracted increasing interest in recent years. The development and application of process analytical methods is a prerequisite for the knowledge-based manufacturing of industrial goods, and allows for the production of high-value products of defined, constantly good quality. Discussed in this chapter are the measurement principle and some relevant aspects and illustrative examples of online monitoring tools as the basis for process control in the manufacturing and processing of thermosetting resins. Optical spectroscopy is featured as one of the main process analytical methods applicable to, among other applications, online monitoring of resin synthesis. In combination with chemometric methods for multivariate data analysis, powerful process models can be generated within the framework of feed-back and feed-forward control concepts. Other analytical methods covered in this chapter are those frequently used to control further processing of thermosets to the final parts, including: dielectric analysis, ultrasonics, fiberoptics, and fiber Bragg grating sensors.
... In recent years, the development and advancement in smart materials has facilitated the structural health monitoring (SHM) becoming an appealing alternative in soil compaction monitoring. These newly developed techniques, including the fiber Bragg grating (FBG) sensors [11,12], the polyvinylidenefluoride (PVDF) sensors [13,14], and the soft capacitive sensors [15,16], offer new possibility for compaction monitoring. It has been shown that these new smart materials-based techniques are effective and promising in SHM field. ...
Compaction is a crucial process in road construction and the compactness is an important parameter in determining the road foundation quality. Traditional compaction monitoring methods are based on different principles. The major principle of these techniques is detecting the water content and bulk density of the soil, and then calculating the dry density and the compactness. The disadvantages are laborious, low accuracy, low efficiency and costly for large scale measurement. These drawbacks may limit their application in certain aspects. In this paper, a novel electromechanical impedance (EMI) based compactness measuring sheet (CMS) for soil compactness monitoring was proposed. The proposed CMS was fabricated by attaching a circular piezoceramic patch onto a circular sheet with a larger size. Eight round CMSs with a diameter of 150 mm, 100 mm, 80 mm, 50 mm were fabricated in this experimental study. Among them, four CMSs were embedded into soil and subjected to compression tests to simulate the increased soil compaction. In this study, the conductance signatures of the proposed CMS were collected and analyzed during the increasing soil compaction process. Experimental results demonstrated that all the peak magnitudes in the conductance signatures in the selected frequency range of 160 kHz to 310 kHz were reduced with the increase of soil compaction. It showed that some specific frequencies shifted to the right side during the compaction process. The variations in the conductance signatures were then quantified with the aid of three statistical metrics. These metrics include root mean square deviation (RMSD), mean absolute percentage deviation (MAPD), and correlation coefficient deviation (CCD). Through calculation, all these metrics increase with the increase of soil compaction, which can be employed as indicators in the soil compaction process. To obtain more insight into CMS electromechanical system, the finite element analysis were also performed to study the EMI response. The simulation results well verified the experimental results. This preliminary study has verified that the proposed EMI based CMS is feasible and effective in monitoring soil compactness and shows a promising application prospect.
... The fiber Bragg grating technique is usable for a wide spectrum of applications and applicable to different investigated materials. The application of the FBG sensors on concrete [4][5][6] or steel structures [7] is not new, but still not used very often. Although there are some works related to application of fiber optic sensors (FOS) in timber structures such as glue-laminated timber (glulam) [8], it is still very innovative new approach and its industrially applicable process is presented in this work. ...
Long-term structural health monitoring (SHM) plays an important role in the safety of public transport infrastructure such as bridges or tunnels and warns in the event of any emerging problem. This article describes development and testing of system based on fiber Bragg grating (FBG) sensors that can detect changes in strain and temperature. The first phase of the research has been focused on the development of new fiber optic sensors for the monitoring of concrete structures and their investigation in laboratory conditions. The work also shows novel applicability of the same FBG technology for glulam structures. Mechanical loading tests of the concrete beam as well as glulam beam with embedded sensors were carried out. Data measured by developed fiber optic sensors were compared with the readings from reference sensors as well as with the analytically calculated values. The achieved results proved good agreement between the measured data, analytical data and reference methods. In second phase of the research, the pilot installation of the sensors was carried out on the newly constructed prestressed-concrete bridge. The bridge was monitored throughout pre-stressing phase and monitoring continued after the completion of the construction works. Problems with the fragility of the sensors occurred during the measurements, but the obtained results provide a good basis for further improvement of the system.
... Using the advantages mentioned above, FBG sensors were first used to test the properties of composite materials in the aerospace industry and, nowadays, these sensors have found wide applications in biomedical engineering [17,18], civil engineering [19,20], composite structures [21], pipelines [22][23][24], and mechanical systems, among others. Mendez et al. [25] first introduced them to geotechnical testing. ...
... The manual pump was used to evenly and slowly apply the load at 5, 10, 15, and 20 kN in "Active" and at 5,10,15,20,25,30,35, and 40 kN in "Passive". Meanwhile, the wavelength of the FBG sensors integrated with the rock bolt was measured and processed by the interrogator. ...
Fiber Bragg grating (FBG) sensors, which can accurately measure strain, can be integrated with rock bolts with small fingerprints. In this paper, according to the force mechanism of prestressed anchor and non-prestressed anchor, different loading modes were designed, named active loading mode and passive loading mode. Then, FBG technology was used to monitor the axial force variation of prestressed anchor and non-prestressed anchor in different loading modes. Based on the test results, it is found that when the anchoring force is relatively small (<35 kN), prestressed anchors need to be tested by active loading mode, and non-prestressed anchors need to be tested by passive loading mode. For the prestressed anchor, the force condition of the bolt-shaft was similar to that of the two-force bar, and the axial force of the bolt-shaft was nearly the same along its entire length. Taking the applied load as the reference, the change rate of the axial force of the bolt-shaft was less than 10%. For non-prestressed anchor, due to the plate, there is a certain area surrounding the plate where the axial force of the bolt-shaft was greatly influenced. With applied loads of less than 15 kN, the change rate of the axial force on FBG1 was greater than 10%. With applied loads of greater than 20 kN, this was less than 10%. In this area, influenced by the plate, the axial force of the bolt-shaft increases, and as the applied load of the pullout test increases, the influence decreases.
... At present, nondestructive testing (NDT) techniques, including ultrasonic guided waves [9][10][11][12][13][14][15], electromagnetic waves (EW) [16,17], acoustic emission [18][19][20][21][22][23][24], infrared thermal imaging [25][26][27][28], fiber optic sensors [29][30][31][32][33][34][35], x-ray diffraction [36] and radar/microwave [37][38][39], are effective in structural damage detection. Although these methods can reflect the local damage state of the structure, they require complex and expensive instrument and professional interpretation, which makes it difficult to carry out real-time and on-line structure health monitoring. ...
Concrete-filled steel tubular member (CFSTM) is widely used in high-rise buildings, long-span bridges and other complex environments. Poor cementation leads to incomplete contact and even no contact between the steel tubular member and the concrete grout, which reduces the ultimate load bearing capacity and ductility of CFSTM. A method to quantitatively evaluate the debond of the CFSTM is proposed in this paper by using a pair of piezoceramic transducers respectively as actuator and sensor to emit and to receive stress wave signals. Since the gap between the steel tubular member and the concrete grout results in the change of the difference of acoustic impedance in propagating medium, the transmission coefficient of tubular decrease and the reflection coefficient increases, which leads to the increase of head wave amplitude and the decrease of cementation index (CI). In this research, numerical simulations with finite difference time domain (FDTD) method are used to demonstrate the feasibility of this method. Additionally, experiments were conducted, and experimental results also verify the effectiveness of the proposed method and show that CI based on piezoceramic is able to quantitatively evaluate the debond of the CFSTM.
... In this regard, one of the prominent research over the use of FBG sensors in building structures to monitor the wind response is made by Ni et al. 60 where the use of massive deployment of FBG sensors in Canton tower, China, for temperature and strain monitoring has been demonstrated. Another important investigation was conducted by Li et al., 61 which includes investigation on the performance of FBG sensors in an under-construction 18-storey structure. The research evaluated the temperature and strain measurements during three main stages of construction 62 : (a) before pouring of the concrete, (b) during the pouring stage of the concrete, and (c) after pouring of the concrete. ...
This research explores the seismic damage response of a frame–shear wall reinforced concrete structure exposed to progressive seismic excitations. The shear wall structure is a three‐storey one‐quarter‐scaled reinforced concrete structure. The test was conducted by applying progressive seismic excitations using a shaking table. The shear wall structure experienced inelastic deformations under high seismic excitations that eventually caused the transformation of the structure from a state of elastic deformation to a state of highly inelastic deformation. Damage in the form of plastic hinges occurred because of induced dynamic instability in the structure. The monitored seismic responses in this research includes the variation in the residual strains and their dynamic time histories. Precise and detailed measurements of varying strain responses and effective estimation of damage response within the structure have been a primary goal in this research. Successful implementation of fibre Bragg grating (FBG) strain sensor is presented and applied in this experiment because of its enhanced sensitivity towards monitoring the structural dynamic strain response. The presented research also evaluates the suitability of FBG strain sensors in dynamic testing of a frame–shear wall asymmetric structure by comparing the damage response obtained through FBG sensors and the predictions developed from the dynamic properties of the test structure, monitoring the progress in structural damage and predicting the cracks inside the structure. The monitored responses obtained through a series of tests prove that FBG sensors have the advantages of significant accuracy, small size, and good embedding abilities. It demonstrates its promising failure monitoring abilities and potentials for the crack detection. The results achieved through this research would be beneficial to validate existing numerical simulation and analytical procedures, particularly for the structures with inherent asymmetry. It has been demonstrated in this paper that (a) the structure entered into the critical state when the ground motion excitation was 0.5 g with invisible cracks, (b) a sudden change in the residual strain response can help in detecting the initiation of a crack, and (c) the damages in the structure were due to the formation of the plastic hinges at the flexible edge of the structure near the beam–column joints.
