A Review on the Latest Advancements and Innovation Trends in Vibration-Based Structural Health Monitoring (SHM) Techniques for Improved Maintenance of Steel Slit Damper (SSD)

Steel slit damper (SSD) is specifically engineered to absorb and disperse energy to mitigate the possibility of structural damage and collapse during seismic events. However, the effectiveness of these dampers are compromised due to wear, corrosion and other forms of material degradation and failure mechanisms. For this reason, it is important to consistently monitor its condition and conduct maintenance and repairs to guarantee safety and dependability of the structures it is installed with. Now, vibration-based techniques have emerged as a promising structural health monitoring (SHM) strategy. It involves methodologies for detecting changes in functions and analyzing vibrations to discover potential problems. This study entails a comprehensive examination of the most recent advancements and breakthroughs in vibration-based methodologies used in SHM. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020), we identified several key techniques and technologies that show promise in enhancing the maintenance and monitoring of steel– or steel and metal surfaces- slit dampers. The pros and cons of these methods are presented to be applicable when monitoring an SSD. This paper presents notable figures and their corresponding discussions to achieve enhanced understanding of the advancements in SHM towards sensor technologies, monitoring techniques, and applications in civil infrastructure. Furthermore, this paper reviews the applications and functions framework for real-time SHM of SSDs together with their practical implementations and applications using diverse monitoring technologies to promote innovation. Finally, the optimal sensor selection criteria, data gathering methodologies, experimental settings, innovative approaches with comparative analyses, and a proposed maintenance standard for SSDs are described in this study.


I. INTRODUCTION
SHM is crucial for ensuring the safety of people and the protection of essential infrastructures [1].It encompasses an The associate editor coordinating the review of this manuscript and approving it for publication was Mauro Fadda .array of sophisticated technologies [2] and methodologies [3] that promotes the potential of continuous development in the field including systems-of-systems application [4].While image-based techniques offer valuable insights through visual analysis for surface anomaly detection [5], the focus of this paper shifts predominantly towards the complex methodology of vibration-based SHM.By employing sensors to monitor vibrations, vibration-based SHM provides understanding of a structure's integrity, enabling the early detection of potential failures through subtle changes in vibration patterns.It has become a crucial tool in predictive maintenance, providing a detailed and proactive strategy to protect the durability and safety of engineering structures.It has garnered our primary focus due to its impact and relevance in various industries.
Meanwhile, SSDs have emerged as vital components in enhancing the resilience and longevity of structures in regions susceptible to earthquakes [6].These dampers are engineered to absorb and dissipate energy, significantly reducing the impact of dynamic loads and vibrations on infrastructures.
By employing real-time vibration-based monitoring techniques in conjunction with SSDs, engineers can proactively assess the condition of structures, plan timely interventions, and fortify the structural resilience of the city's infrastructure [7].
While vibration-based SHM and the utilization of SSDs have made substantial strides [8], significant gaps and challenges persist.Fig. 1 depicts the gaps and issues that we have discovered which are necessary for further investigation.

A. GAPS AND CHALLENGES 1) OPTIMAL UTILIZATION OF VIBRATION-BASED TECHNIQUES
While the potential of vibration-based monitoring techniques for SHM is widely recognized, there exists a pressing need to discern the best practices for their practical implementation in conjunction with SSDs [9].The existing knowledge offers some understanding in a bridge setup [10], civil structures [11], and even on modern structures [12].However, a complete comprehension of the criteria for selecting sensors, protocols for acquiring data, and experimental settings that result in real-time insights into structural health is still difficult to achieve.

2) PERFORMANCE EVALUATION OF SSDs
SSDs are metal dampers and are considered as a hysteretic type of damping device.Their seismic performance and efficacy in mitigating structural damage and enhancing resilience has been well-established in the recent study conducted by Behnamfar & Almohammad-albakkar in 2023 [13].In addition, several researchers delved in the seismic performance of an optimized and novel shaped [14], torsional [15] and hysteretic [16], multi-slit [17] and strip [18] metal yielding damper.Thus, a thorough analysis of the performance of these dampers under real-world conditions remains essential [19].A systematic presentation of the results of these studies promotes operational efficiency, safety benefits, and the long-term effects of utilization.

3) DATA VALIDATION TECHNIQUES IN VIBRATION-BASED MONITORING
With the increased reliance on vibration-based monitoring [20], there is a need for the systematic review and evaluation of common and best practices related to data validation techniques.Ensuring the accuracy and reliability of the data acquired through these monitoring techniques is paramount for effective structural health assessment.

4) STRUCTURAL LONGEVITY AND MAINTENANCE
SHM is fundamentally linked to the long life and maintenance of SSDs and the structures they safeguard [5].It is imperative to examine the impact of SHM on the operational efficiency and safety of these critical components, thereby addressing the fundamental question of how to ensure their prolonged and effective use.

5) EXPERIMENTAL DESIGN AND VALIDITY
The validity of experimental results hinges on robust design.Accordingly, an exploration of aspects that impact experimental design, such as sample size determination, testing conditions specification, and the choice of suitable statistical analysis methods, is crucial for reliable and meaningful findings.
Considering these gaps and challenges, this research specifically aims to comprehend the significance of SHM and SSDs in their different contexts.It is imperative to utilize vibration-based techniques in SHM to guarantee the future safety and longevity of critical infrastructure.This will be achieved by analyzing past and present developments in the field through a comprehensive systematic literature analysis.This study brings a significant impact to the field of SHM by investigating the function and improving the use of SSDs to enhance seismic resilience.Our paper addresses important gaps in knowledge regarding SSDs' performance during seismic events and present methodological ways for evaluating and incorporating them into structural systems conducted from past researches.We systematically investigated the efficiency of vibration-based monitoring methods combined with SSDs that confirms their usefulness and improves the accuracy of structural health evaluations.Our study has practical consequences that go beyond theoretical improvements, providing real methodologies for designing, maintaining, and optimizing structures with SSDs.This study addresses the significant knowledge gaps identified in subsection I.A -'Gaps and Challenges,' and establishes a new standard for future research in the field.It emphasizes the importance of combining advanced monitoring technologies with seismic damping solutions to protect critical infrastructure and human lives from seismic hazards.

II. METHODOLOGY
Our systematic literature review (SLR) is conducted using PRISMA 2020 [21] to specifically answer this research question: ''What are the current advances and best practices in utilizing vibration-based monitoring techniques that are applied and/ or can be applicable to SSDs for real-time SHM, with emphasis on sensor selection, data acquisition protocols, and experimental parameters?''

A. RESEARCH STRATEGIES
We conducted a comprehensive search in the IEEE database, which served as our main source of literature.Additionally, we searched through various esteemed databases such as Google Scholar, Elsevier, MDPI, Springer, Wiley Online, and the ASCE Library.The search was conducted during the time frame of January 6, 2024, to January 19, 2024.
The selection of these databases was based on their extensive coverage of academic literature in the fields of engineering, technology, and related fields.To ensure the accuracy and completeness of the review, a uniform search strategy was employed.We used carefully chosen keywords to ensure that all relevant studies related to our research question were included.The choice of keywords was determined using the criteria devised by Cooke et al. in 2012 [22].Two search string formats were developed to align with the diverse search preferences across selected databases.Our research protocol are tabulated in Appendix A.
To ensure relevance and comprehensiveness, several filters were applied, focusing exclusively on studies published between January 2010 to 2024, written in the English language, excluding conference papers, and focusing solely on journal articles and periodicals.After applying these filters, a total of six hundred ninety-seven (697) literature were selected and considered as potential literature for data extraction.Articles were screened based on title, abstract, and relevant research keywords to ensure alignment with the research question and objectives.The subsequent important stage entails implementing the inclusion and exclusion criteria specified in Appendix A. This method enables a comprehensive assessment of the collected literature.

B. LITERATURE SCREENING AND EXTRACTION METHOD
To guarantee the reliability and replicability of our research, we carefully established a data extraction protocol to systematically gather and arrange data from scholarly journals, closely fitting with our research goals.The guideline classifies the fundamental elements of each paper, encompassing publication particulars, research objectives, procedures, data particulars, and key discoveries.The systematic methodology employed facilitates a comprehensive examination of the existing body of literature, establishing a strong basis for comprehending the research framework, assessing the methodological rigor, and incorporating pertinent findings that align with our study objectives.
The extraction method employed in this literature screening process is based on a three-way approach encompassing copy and pasting, paraphrasing, and summarizing techniques.
Copying and pasting were utilized to capture verbatim excerpts, ensuring the precision of key information.Paraphrasing was applied to articulate extracted content in a nuanced and varied manner, promoting a thorough understanding of the literature.Summarizing was used to condense complex ideas into concise representations, facilitating the synthesis of information across multiple articles.This multifaceted approach ensures a comprehensive extraction strategy, striking a balance between accuracy, depth, and clarity in the analysis of relevant data.
We employed a standardized spreadsheet-based data extraction form to ensure uniform and efficient data recording, entry, and organization, minimizing discrepancies and errors.We rigorously reviewed the data to eliminate inconsistencies, thus enhancing the reliability and validity of our conclusions.
As part of the systematic literature process, redundant copies of gathered literature were eliminated to determine the total number of sources available for data extraction.This involved using Zotero Reference Management tool to automatically identify and exclude duplicate items across multiple databases.After removing these duplicates, sixty (60) unique sources remained eligible for data extraction.Fig. 2 shows our PRISMA 2020 flow produced using the tool of Haddaway et al. [23].

III. OVERVIEW OF RESULTS AND DISCUSSIONS
When considering the countries of publication, it can be observed from Fig. 3 that the studies included in the analysis had the most substantial representation from China, Italy, and the United States of America.The substantial contributions from these countries can likely be attributed to factors such as: i.)China has been heavily investing in research and development in recent years.The country has made substantial efforts to become a global leader in science and technology [24].This includes a focus on advances in engineering and structural monitoring technologies; ii.) Italy is known for its engineering excellence, particularly in fields related to architecture and construction [25].Italian researchers and institutions may excel in developing and implementing vibration-based monitoring techniques due to their strong engineering foundation; iii.)The advanced technological infrastructure in the U.S. and the presence of a skilled workforce contribute to the country's ability to conduct sophisticated research in SHM [26], including the use of vibration-based techniques and SSDs.The distribution of included articles with respect to the publishing is heavy on the IEEE Sensors Journal as shown in Fig. 4.  Consequently, the concept map in Fig. 5 offers a cohesive visualization of the extensive range of research topics, innovative technologies, methodologies, and practical applications within SHM, synthesized in this paper.
At its core, the map revolves around SHM, branching out into key research domains including (1) Sensor Technologies, (2) Computational and Data Analysis Methods, (3) Monitoring Techniques and Algorithms, and (4) Applications in Civil Infrastructure.Sensor Technologies explores various innovations like dielectric resonator sensors and fiber bragg grating (FBG) systems, each linked to specific studies detailing their applications and efficiencies.The Monitoring Techniques and Algorithms branch underscores the analytical framework of SHM, showcasing developments from vibration mode estimation to advanced deep learning techniques, illustrating the field's computational progression.The Applications in Civil Infrastructure segment demonstrates SHM's critical role in safeguarding infrastructure, with examples ranging from railway to building monitoring, emphasizing its practical impact.Lastly, the Computational and Data Analysis Methods branch highlights the support systems of SHM, blending computer science with engineering to enhance monitoring through Internet of Things (IoT), data analytics, and energy-efficient strategies, thereby capturing the multidisciplinary essence and innovative spirit of SHM research.

IV. VIBRATION-BASED TECHNIQUES IN SHM
A common thread across literature is practical orientation, emphasizing real-world applicability (see Fig. 6).
Each literature source introduces unique insights while maintaining a focus on practical implementation utilizing vibration-based monitoring techniques in SHM.The proceeding paragraphs address their presentation and thematic analysis in turn as depicted in Fig. 7.

A. PRACTICAL IMPLEMENTATION
Four practical strategies including the Levenberg-Marquardt method (LMD), the least squares method (LSM), compressed sensing method (CSM), and linear demodulation method (LDM) for automated DC offset calibration may be used to enhance the applicability of vibration-based monitoring in real-world scenarios [27].These methods respectively employ the following concepts: • LDM-rotation of the baseband signals' initial course to the optimal location in the pattern diagram being employed [28], [29].
• LMD-the residual error function's gradient must first be identified to establish its direction and lower its errors.[30].
• CSM-a reliable and efficient method for handling significant interference using radar demodulation [34], [35].Hackmann et al. considered practical constraints, addressing challenges in existing systems, and emphasizing real-world applications of SHM technologies [36].In their work, overcoming challenges in SHM systems is achieved through an architecture that mimics how a structure would react to an earthquake (see Fig. 7a).A wireless network that must be flexible and efficient according to the study Hackmann et al [37] which was based on the cyber-physical systems written by Chang et al. [38] requires maintenance and monitoring.A study conducted by Dang et al. explored the use of feature fusion and hybrid deep learning in data-driven SHM to enhance real-time monitoring capabilities and practicality of vibration-based monitoring methods, while also considering safety and reliability [39].
The emphasis on real-time monitoring addresses the need for immediate data insights, contributing to more proactive decision-making in SHM.The process, shown in Fig. 7b, begins with the acquisition of data through sensors, which is then augmented to enrich the dataset for robust training.Key features are extracted using advanced techniques like autoregressive models, discrete wavelet transform, and empirical mode decomposition.The features are combined to provide a comprehensive set of new features that incorporates the fundamental aspects of the structural data.The integrated dataset is partitioned into subsets for training, validation, and testing.Subsequently, a hybrid deep learning model, which utilizes the advantages of convolutional neural networks (CNN) and long short-term memory (LSTM) networks, is trained using this data.Through an iterative process of training and hyperparameter tuning, the model learns to detect and assess structural damage accurately.The model's output is examined closely for damage localization, severity, and detection, yielding a thorough evaluation of the structural health.The performance of the model is rigorously assessed using accuracy metrics and confusion matrices, guaranteeing a high degree of dependability in the health monitoring procedure.Additional iterations of the system are informed by feedback from the evaluation phase, which improves the system's precision for real-world applications.
Crack monitoring was achieved by Zhang et al. using a passive wireless sensor with a dielectric based resonator [40].They configured the device for a versatile and energy-efficient monitoring solution, expanding the options for SHM.Their sensor, schematically illustrated in Fig. 7c is a breakthrough for crack monitoring.It is particularly noted for its ability to endure extreme environmental conditions.The cylindrical dielectric resonator (CDR) sensor's novelty lies in its capacity to detect cracks through shifts in resonant frequency, boasting a significant sensitivity for crack depth characterization.Its versatility is further enhanced by the ability to adjust polarization to detect cracks in various orientations, signaling a substantial advancement in SHM technology.
Wan et al. in 2023 presented a novel multiparameter integration method for chipless RFID sensors (see Fig. 7d) with a focus on SHM [41].The sensor they developed integrates multiple functionalities, including strain and humidity sensing, as well as encoding capabilities without relying on traditional chip-based designs.The sensor achieves its multiparameter sensing through a unique spiral-shaped design that allows for simultaneous measurement of different physical parameters.In addition, their study presented a cost-effective wireless control technique utilizing pin diodes, which improved the sensor's ability to adapt and perform well in various SHM situations.This advancement in chipless RFID technology demonstrates potential for broader application in modern infrastructure monitoring, where multifaceted sensor feedback is crucial for maintenance and safety.FBG ultrasonic sensing system for SHM offers a dynamic damage detection methodology that utilizes ultrasonic guided waves and an adaptive wavelength-demodulated system in locating and monitoring damage through precise ultrasonic signal detection [42].The effectiveness of the FBG (Fig. 7e) in sensing ultrasonic signals up to 1 MHz on an aluminum plate, underlining its potential in enhancing SHM practices across various industries by employing FBG sensors, is achieved by utilizing an adaptive wavelength-demodulated approach based on edge filter detection.

B. TECHNOLOGY DIVERSITY AND REAL-TIME STRATEGY
The utilization of Brillouin fiber-optic sensors and an IoT health detection system for bridge monitoring in the construction management of steel structures supports technological diversity in monitoring.Minardo et al. used a unique optical dimension of a Brillouin fiber-optic sensor for SHM [43].On the other hand, a study by Liu et al. on the IoT health detection system in steel structure construction management emphasized the transformative potential of IoT technology, providing a networked approach for continuous health monitoring [44].Liu et al. investigated the implementation of a health monitoring system to enhance quality management for steel constructions.Their IoT system provides dynamic, automated, and network-integrated solutions that enable continuous, real-time online monitoring.Their approach promotes the enhancement of the operational and management levels of steel frame structures by providing valuable insights into their health status, thus ensuring safety and guiding maintenance decisions.
In 2015, San-Millan and Feliu established an online estimation algorithm for real-time monitoring, addressing challenges posed by noise and offset in signals [45].
According to [41], the methods for characterizing the chipless RFID sensors with spiral shape involve the use of high-frequency structure simulator (HFSS) for modular modeling with lumped RLC functions to simulate interconnected structures, including the effects of solder joints.The modeling is precise, considering the resistance, capacitance, and the On and OFF state inductance values of the PIN diode mirror real experimental conditions.For the antenna design, ultra-wideband technology is employed, optimized to improve transceiver effects within the operation band, ensuring compatibility with multiparameter integrated sensors.Strain and humidity experiments are conducted using a tensile machine and a sealed container with PI film for humidity sensing, respectively.The reconfiguration experimental design utilizes a PIN diode for flexible control of sensor codes and function switching, enabling dynamic adaptation of the sensor system for various SHM applications.
Meanwhile, Sabato et al. in 2016 focused on a wireless accelerometer board for accurate wireless vibration measurements, crucial for real-time assessment [46].Their acceleration evaluator (ALE), referred from the works of Sangiovanni-Vincentelli et al. [47], is a wireless accelerometer board optimized for SHM.The device includes a microelectro-mechanical systems (MEMS)-based accelerometer with low floor noise, a voltage-to-frequency (V/F) converter to convert analog data into frequency values with little loss of accuracy, and a low-power RF transmitter for transmitting the signals.The laboratory tests showed that ALE's accuracy in monitoring vibrations necessary for SHM applications is like that of wired-based integral electronics piezoelectric (IEPE) sensors.Further validation involved back-to-back comparisons of recorded data during simulated earthquakes, showing ALE's efficacy in monitoring real engineering structures and its ability to evaluate earthquake-induced vibrations with high accuracy, comparable to high-sensitivity wire-based IEPE accelerometers.

C. EMERGING TRENDS AND FUTURE DIRECTIONS
Dubey et al. [48] provided a persistent review on the latest methodologies in vibration-based SHM.They have highlighted the use of a frequency shift coefficient (FSC) algorithm referred from the works of Kim and Stubbs [49] for precise damage detection, localization, and quantification in structures.The algorithm's effectiveness is applicable across various scenarios involving those with uncertainties in natural frequencies, showcasing advancements in accuracy and efficiency for SHM.If cracks in beam-type structures may be identified using frequency data, so are the cracks in SSDs using the FSC algorithm.
Other promising trends, applicable in the vibration-based monitoring even of SSDs, are evident and can be founded from the study of Giannelli et al. in 2017 [50] and Santos et al. in 2021 [51], respectively.Reference [50] underlines a significant leap towards multifunctionality and integration within SHM technologies.The creation and application of a multifunctional piezopolymer film transducer, as detailed in the paper, exemplify the innovative strides being made in the field.This device not only aims to enhance the efficiency and effectiveness of SHM systems by combining the capabilities of Lamb wave generation and reception, impact detection and localization, and temperature measurement into a single unit but also showcases the potential for new SHM methodologies that can leverage such integrated functionalities for more comprehensive and accurate structural assessments.The use of metallized piezoelectric polyvinylidene fluoride (PVDF) film and a laser etching process for the fabrication of this transducer represents a technological advancement that addresses some of the limitations of existing SHM systems.By integrating multiple sensing functions, the device aims to reduce the complexity and increase the reliability of SHM applications.[50] focused on overcoming challenges such as inhomogeneous metal coating properties for the resistance temperature detector (RTD) component illustrates a commitment to refining these innovations further.This advancement is indicative of the broader trend in SHM towards systems that are not only multifunctional but also more adaptable and easier to deploy across various structures and conditions.As SHM technologies continue to evolve, the emphasis on developing devices that can provide comprehensive monitoring capabilities in a single package is likely to grow.The trend is fueled by the growing need for SHM systems that provide in-depth, immediate information about the condition of structures.This allows for proactive maintenance and safety measures to be taken without causing major interruptions or costs.The versatile piezopolymer film transducer is a significant advancement in addressing these requirements, offering insight into the future of SHM where integration, efficiency, and precision are crucial.As the field progresses, further innovations in materials, fabrication processes, and sensor design are expected to emerge, pushing the boundaries of what is possible in vibration-based SHM and opening new possibilities for monitoring the structural integrity of a wide range of assets.
Meanwhile, an aligned carbon nanotube sensors, representing a cutting-edge technology for precise strain monitoring in composites was introduced by [51].From their study, which is distinct from vibration-based SHM, the potential applications of advanced sensors in SHM indicate an emerging trend toward more accurate and specialized monitoring solutions is achievable.Although it enhances the SHM field by allowing the detection and monitoring of strain via electrical resistance changes, it does not specifically focus on vibration-based monitoring techniques.Instead, it offers an innovative approach to assessing structural integrity through strain measurements, promising for applications in aeronautics and potentially beyond.This method represents a different facet of SHM, emphasizing material deformation over vibrational analysis.Santos et al describes the development and evaluation of aligned carbon nanotube (CNT)-based sensors for strain monitoring in composite materials, emphasizing their application in SHM.The sensors are intended to be positioned on traditional aeronautical laminates and have two alignment options (parallel and transversal to strain direction) to detect strain by monitoring alterations in electrical resistance.Their study emphasizes the sensors' ability to recognize strain directions and measure strain levels accurately, showcasing its potential for sophisticated SHM applications.This method signifies notable progress in applying nanotechnology for enhanced SHM, offering better safety and performance in several engineering sectors.
The results of vibration-based SHM, even when used to SSDs, can be influenced by factors such as sample size determination, testing condition requirements, and statistical methods.For instance, within the realm of sample size determination, Contreras and Ziavras [52] demonstrated a consistent emphasis on controlled conditions, simulations, and comparative analyses.When it comes to sample size, there is a trade-off between statistical power and practical implementation.Increasing the sample size can lead to decreased transmission rate proportional to the data payload size of the networking specification, but it also results in a longer measurement window.Detailed descriptions of testing conditions were crucial for understanding the validity of the experimental setups.In Ran et al.'s study [53], information on the dimensions of the clamped beam offered essential insights for replicating experiments and interpreting results.Despite the absence of specific information in the damage detection on infrastructure using low-cost, efficient output-only wireless sensor networks, the critique of not providing such details acknowledged the significance of documenting specific conditions under which the monitoring system was tested or implemented.Lastly, broader and clear discussion on applied statistical analysis methods are important to set future research directions.It serves as a guide for upcoming studies.For example, Zonzini et al. [54] introduced the Gini index and the modal assurance criterion (MAC) as measures of sparsity and signal recovery quality, respectively.These introduced metrics enhanced the robustness and reliability evaluation of the experimental designs, showcasing a thoughtful approach to statistical analysis.

V. OPTIMAL SENSOR SELECTION CRITERIA, DATA GATHERING METHODOLOGIES, AND EXPERIMENTAL SETTINGS
The criteria for selecting the most effective sensors, the approaches for collecting data, and the experimental configurations usually employed in vibration-based monitoring techniques are compiled in Fig. 8.The subsequent sections elaborate on the main discoveries.

A. SENSOR SELECTION CRITERIA 1) MULTIFUNCTIONAL PIEZOPOLYMER FILM TRANSDUCER
Introduces the integration of different sensors into a single device, providing insights into optimal sensor selection for multifunctional purposes [50].An example is using an interdigital transducer (IDT) to generate and receive Lamb waves.The design of the IDT is specifically optimized to improve the frequency range and accuracy of the monitoring process.A circular piezoelectric sensor is used because of its high accuracy in detecting and precisely determining the positions of impacts.It mimics a point sensor to ensure excellent interaction with waves.The resistive temperature device (RTD) is used to monitor temperature precisely.Its design considers the requirement for substantial changes in resistance at typical temperatures, even when there is variability in metallization.

2) CDR-BASED SENSOR
The evaluation of the CDR-based sensor, proposed by Zhang et al., unveils distinctive criteria, emphasizing compact size, installation flexibility, and robustness [55].This contributes significantly to defining optimal sensor selection criteria for real-time SHM.Their study suggests the creation and testing of a CDR-based sensor intended for detecting cracks, emphasizing its selection based on precise and efficient detection capabilities.It utilizes a ceramic with a high dielectric constant of 90 to achieve a compact form factor.The sensor's dimensions, including an inner radius of 7 mm, an outer radius of 12 mm, and a height of 9 mm, are chosen to minimize variations in detection sensitivity due to the sensor's placement.Through evaluating the resonant frequencies under different crack sizes and locations, the sensor's design is proven to offer consistent and reliable monitoring for metallic structures, adapting to various crack conditions.

3) FIBER-OPTIC SENSORS
These references underscore the importance of fiber-optic sensors, particularly FBG technology and polymer optical fibers (POFs) [56].These technologies bring forward sensitivity, resistance to electromagnetic interference, and cost-effectiveness as crucial factors in optimal sensor selection [57].

4) ALIGNED CARBON NANOTUBE (CNT) SENSORS
The assessment of electrical resistance response, gauge factor values, and electrical resistance anisotropy in aligned carbon nanotube [58], [59] sensors contribute to the understanding of optimal sensor selection criteria, emphasizing sensitivity and performance metrics, focusing on electrical resistivity changes under strain.The sensor demonstrates significant sensitivity to deformation, highlighting a notable increase in gauge factor values when strained perpendicular to CNT alignment.This sensitivity is attributed to the unique anisotropic electrical properties of the VA-CNTs, providing a reliable means of strain detection across different substrates, 44390 VOLUME 12, 2024 Authorized licensed use limited to the terms of the applicable license agreement with IEEE.Restrictions apply.including polyimide (PI), epoxy, and polyethylene terephthalate (PET) films.

5) THICK-FILM ACOUSTIC EMISSION SENSORS
The development and comparison of a novel thick-film acoustic emission sensor can support structurally integrated condition monitoring sensor selection criteria [60].

B. DATA GATHERING METHODOLOGIES 1) WIRELESS MONITORING OF CORROSION POTENTIAL IN STEEL SURFACES
In 2023, Bhadra et al. presented a wireless monitoring of the corrosion potential of reinforcing steel in concrete using passive sensor.Their sensor, based on an LC coil resonator, adjusts its resonant frequency in response to changes in the corrosion potential [61].The sensor is designed for remote monitoring through an inductively coupled interrogator coil, offering a no-power-required, cost-effective solution for long-term corrosion monitoring.The methodology includes accelerated corrosion tests, highlighting the sensor's ability to detect corrosion initiation and progression with high resolution on steel surfaces embedded in concrete.

2) NUMERICAL SIMULATIONS AND EXPERIMENTAL PROCEDURES
Gao et al. employed a detailed numerical simulation and experimental procedure to investigate the mechanical properties and parameter sensitivity of a steel damper U-shaped configuration [62].Using ANSYS software [63], a finite element model was created to simulate unidirectional tension and compression tests, validating theoretical predictions against experimental outcomes.This approach emphasized the importance of geometric parameters on damper behavior, providing insights into the stiffness and energy dissipation characteristics under varying conditions.The study's methodology underscores the synergy between computational modeling and physical testing in optimizing damper design for enhanced structural resilience.
In a comparable case, Lee and Kim proved that it is possible to focus on the development and seismic retrofit application of box-shaped SSDs through numerical simulations and experimental procedures including cyclic loading tests to assess seismic energy dissipation capabilities [64].Their damper design, integrating four slit plates into a compact box shape, aims to produce a larger damping force efficiently.Lee and Kim' experimental setups involved a 300 kN hydraulic actuator for testing two damper specimens, utilizing FEMA-461M guidelines for quasi-static cyclic testing.The results from these methodologies affirm the dampers' effectiveness in energy dissipation and displacement control, highlighting their potential for seismic retrofitting in reinforced concrete structures.
Additionally, dynamic behavior of piezoelectric microcantilevers can be investigated using 3D-Laser Doppler Vibrometry for both out-of-plane and in-plane motion detection [65].A numerical simulation through finite element analysis and experimental validations, focusing on microdevices' vibration in the hundred kHz to MHz range.The methodology integrates analytical modeling and 3D-FEM with experimental procedures, highlighting the precision in detecting bending, torsion, and lateral modes of microcantilevers.This study advances the characterization of microsystem dynamics, offering insights for future nondestructive evaluation tools in MEMS technology.This combination provides a nuanced understanding of data-gathering methodologies, especially in the context of capturing subtle vibrations in flexible structures.

3) 2D VIBRATION SENSOR BASED ON MULTI-AXIS FLEXURE HINGE
Wei et al. utilized a sophisticated methodology for data gathering, which combines FBG technology with a multi-axis flexure hinge mechanism to sense 2D vibrations [66].Through detailed numerical simulations, the design was refined to improve sensitivity and resonant frequency, focusing on dimensions such as hinge diameter and thickness.The experimental validation included calibration tests to evaluate the sensor's performance in detecting vibration signals, with a focus on understanding its amplitude-frequency and linear response characteristics under varying conditions.This innovative approach enables precise 2D vibration measurements, highlighting its applicability in accurate monitoring scenarios.The innovative approach referred to here involves a distinct arrangement in which both ends of the FBG are firmly fastened between the cantilever beam and a height block.This structure greatly improves the sensitivity of the sensor while effectively preventing the development of chirp or multi-peak phenomena, which are commonly encountered issues in FBG sensor design.The study cites Wang et al.'s proposition of an FBG 2-D vibration sensor with adjustable sensitivity, achieved by altering the mass ring's position, allowing for customized sensitivity settings according to specific application needs [67].In the study, a lever-type FBG vibration sensor was utilized.This sensor is known for its restricted beam amplitude and exceptional shock resistance qualities.The science behind this FBG accelerometer based on an L-shaped beam and elastic diaphragm, which boasts remarkable stability and lateral interference immunity was referred from Zeng et al. [68].Their accelerometer demonstrated an acceleration sensitivity of 220 pm/g and operates efficiently within a frequency response range of 20 Hz to 70 Hz, although its complex structure is a noteworthy aspect of its design.

4) CHIPLESS RFID SENSORS
Chen et al. [69] and Wan et al. [41] provided detailed insights into experimental setups for chipless radio frequency identification (RFID) sensors.Their works contribute significantly to the synthesis of knowledge on data-gathering methodologies, particularly for strain and wireless parameters.In particular, [69] introduced a novel approach to chipless RFID strain sensing for metal structure defect detection that focus on a multibranch U-shaped tunable encoding design.Their work focused on the creation of a sensor that had a high Q-value, high spectral efficiency, and high encoding capacity.This sensor combines strain detection and compact encoding capabilities.Their study details the sensor's design, including the use of a low dielectric constant substrate for durability and performance in harsh environments, and presents a low-cost, intelligent detection scheme leveraging a lightweight vector network analyzer for data collection and transmission.Their methodology emphasizes the sensor's potential for large-scale deployment in SHM systems within the IoT framework.Finally, [41] studied simultaneous monitoring of strain, humidity, and encoding using a multiparameter chipless RFID sensor.This integrated approach leverages innovative designs, including a spiralized bandstop filter and PIN diodes for reconfigurability.The sensor facilitates the combination and independent functioning of these parameters, validated through comprehensive simulations and experimental verifications.Their methodology exemplifies a leap in chipless RFID technology, emphasizing the sensor's versatility in SHM applications, enabled by a novel wireless control scheme for dynamic parameter adjustment and monitoring.

C. EXPERIMENTAL SETUP AND SETTINGS
In the study by Zhang et al. [40], a passive wireless sensor for crack monitoring, utilizing a CDR to detect cracks in various infrastructures was developed.Their experimental setup involved a compact CDR of 24.0 mm in diameter and 9.0 mm in height, made from ceramic with a relative dielectric permittivity of 90, designed to operate at a resonant frequency of 1.36 GHz.This configuration allowed for the detection of crack depths with a sensitivity of 25.4 MHz/mm for a fixed crack width of 2.0 mm.The sensor's effectiveness in monitoring crack growth was demonstrated through measurements made at 0.25 m using a horn antenna, highlighting its potential for use in extreme conditions without the need for electronic devices or metal components.In 2021, Yao et al. [70] embarked on an experimental and numerical investigation of low-yield-point steel shear panel dampers, focusing on their cyclic behavior for seismic damage mitigation.Their comprehensive research incorporated full-scale testing of three shear panel damper specimens, each designed with distinct flange configurations and subjected to varying loading conditions.The core of these dampers, crafted from LYP225 steel, uses an innovative approach to enhance seismic resistance.The experimental setup meticulously gauged the dampers' hysteretic response, deformation behavior, crack propagation, and energy dissipation capabilities, alongside ultra-low cycle fatigue performance.To complement the experimental data, a plasticity analysis concerning cyclic hardening of LYP225 steel was conducted, leading to the development of a simplified calibration method for a combined hardening constitutive model.Their holistic evaluation not only confirmed the effectiveness of the dampers in dissipating seismic energy but also informed the refinement of numerical models aiming to accurately predict the dampers' performance under seismic loading.In the case of Zlatkov et al. [71], their team investigated a new metallic damper device designed for seismic energy dissipation.Their innovative approach focused on the experimental testing of eight vertical components, each varying in cross-sectional size, to evaluate their hysteretic behavior and capability for seismic energy absorption.Their experiments, conducted using a steel S-15-30 for its ductility, involved 16 nonlinear tests to examine the components under cyclic loads.Additionally, their exploration integrated numerical simulations with finite element analysis in Abaqus/Standard to validate and verify the experimental outcomes, offering a cost-effective alternative to physical testing.Their research highlighted the device's effectiveness in adapting to seismic demands, providing a significant advancement in passive seismic protection technologies.
In the work presented by Chen et al. [69], innovative low-cost chipless RFID strain sensor tailored for IoT-based SHM systems was introduced.This sensor integrates strain sensing and tunable encoding capabilities, offering a novel approach to monitoring structural integrity efficiently.The sensor's design leverages a U-shaped band-stop resonator, enabling high spectral efficiency and encoding capacity while maintaining a small form factor.A significant aspect of their research included the development of a cost-effective detection method, suitable for large-scale mechanical structures, which enhances the potential of RFID technology in monitoring the health of critical infrastructure.Through this study, they have successfully demonstrated the sensor's utility in providing valuable data for assessing the condition of structures, thereby contributing to the advancement of smart city development and IoT applications in the field of SHM.
The research by Wan et al. [41] focused on the development of a chipless RFID sensor capable of multiparameter integration, including encoding, humidity, and strain measurements.Their sensor, designed for SHM, leverages a novel approach by combining organic materials and RF switches for reconfigurability.Through experimental validation, their scientific work demonstrated the sensor's ability to flexibly monitor and report on various parameters critical for assessing the condition of structures.The integration of PIN diodes facilitates state reconfiguration, enhancing the sensor's versatility.Additionally, a low-cost wireless control method is proposed, expanding the potential for remote monitoring applications.Their work represents a significant step forward in the SHM field by offering a more adaptable and cost-effective solution for monitoring structural integrity.Hong et al. [72] started a novel, data-driven approach for monitoring the health of high-speed rail suspension systems using multi-location vibration data.Their innovative framework avoids the need for complex dynamic models or high-fidelity simulations, leveraging instead the synergy of data analysis and domain knowledge.Additionally, their approach employs multi-output support vector regression (MSVR) to estimate the stiffness and damping coefficients of the suspension system in real-time from vibration signals.The framework's practicality was validated through simulations and real-world operational data, demonstrating its potential for enhancing maintenance strategies and operational efficiency of high-speed rail systems.Pickwell et al. [60] developed a novel thick-film acoustic emission (AE) sensor for structurally integrated condition monitoring.Utilizing lead zirconate titanate, the sensor demonstrated a thickness of 17.6 µm and was directly deposited onto a Kovar plate.Their work aimed at providing a more compact and cost-effective solution for continuous, nondestructive SHM.The sensor's performance, comparable to commercial AE devices, was validated through simulations of acoustic emissions, underscoring its potential for broader application in industries requiring efficient and reliable monitoring techniques.

VI. INNOVATIVE APPROACHES AND COMPARATIVE ANALYSES SHM OF SSDs
A visual abstract of the complex and multifaceted approach that is applicable to monitoring the performance of SSDs, extracted from selected literature, is shown in Fig. 9.

A. MONITORING STRATEGIES
In Fig. 9, section A, the established the works of AbdelRaheem et al. [73], and Lamonaca et al. [74], IoT technology into SHM systems presents a compelling case for its applicability in monitoring strategies for SSDs.IoT-based SHM leverages connected devices to acquire and process data, offering a robust framework for assessing the integrity of civil and industrial structures in real-time.This approach enhances the ability to detect, identify, and characterize structural damage by utilizing smart sensors, such as synchronized accelerometer sensors, to collect vital data points.These systems efficiently transmit data over wireless networks, eliminating the need for fixed infrastructure and enabling dynamic monitoring of structures' stiffness and mass changes.The use of IoT in SHM facilitates the automated management of big data, improving damage detection and identification techniques.This methodology not only supports the feasibility of using IoT-based systems for the monitoring of SSDs but also highlights the significant benefits of IoT in advancing the safety and maintenance of engineering structures through precise and real-time monitoring capabilities.Additionally, Sofi et al. [75] tackled the use of synchronized accelerometer sensors for real-time damage monitoring, application of GPS for damage localization, and integration of smart materials and MEMS in sensor networks to enhance monitoring efficiency.These strategies demonstrate the applicability and potential of wireless smart sensor network in monitoring strategies for SSDs, leveraging advancements in technology to ensure the safety and durability of engineering structures.Extracted from the works of [76], wireless sensor networks (WSNs) for SHM, offers advantages over traditional wired systems, such as reduced installation and maintenance costs.The architecture and operation of WSN-based SHM systems includes sensor node architecture, data processing strategies, and network topology.In the case of SSDs, the potential for integrating advanced wireless communication technologies, energy harvesting, and enhanced data processing capabilities could significantly improve the monitoring efficiency of steel structures, including slit dampers, by enabling more sophisticated data analysis, better fault tolerance, and improved scalability of SHM systems.Fiber optic sensors (FOS) for SHM, offer advantages such as high sensitivity, resistance to electromagnetic interference, and the ability to perform distributed measurements over large structures [77].These characteristics make FOS particularly suitable for monitoring the health of steel structures, including slit dampers, by enabling precise and real-time tracking of structural changes, thereby providing an effective monitoring strategy for ensuring structural integrity and safety.Lopez-Higuera et al. [77] investigated the potential of intensity-based FOS for SHM, particularly calibrated using an impact tester.This approach enhances the monitoring of structural integrity by allowing the precise calibration of FOS through impact testing.This methodology, particularly relevant for SSDs, suggests a novel way to quantify the effects of physical impacts on structural components.By integrating impact testers for calibration, the sensitivity and accuracy of FOS in detecting and assessing damage in steel structures, such as those involving slit dampers, are significantly improved.This approach could provide a more refined and reliable monitoring strategy, ensuring the safety and durability of steel constructions against impacts and vibrations.High-speed camera that functions as multiple cameras through rapid viewpoint switching, demonstrates the capability to accurately monitor dynamic behaviors and estimate modal parameters like resonant frequencies and mode shapes [78].Given its success in a bridge model experiment, applying such a system to SSDs could enhance the monitoring accuracy and efficiency, potentially offering a novel approach to assess their structural health and dynamic responses effectively.

B. COMPARATIVE ANALYSIS
Section B of Fig. 9 illustrates the application of several innovative approaches and designs to monitor the performance of SSDs.For instance, Antunes et al. [79] presented a low-cost, compact, intensity-encoded accelerometer based on polymer optical fibers, optimized for SHM applications, including civil engineering structures.Its innovative design offers a novel approach for monitoring, with a sensitivity of 33.5 ± 0.1 mV/g and a resonant frequency suitable for various applications.This technology's advantages, such as cost-effectiveness and robustness compared to conventional accelerometers, can be directly applied to evaluating SSDs' performance, showcasing potential improvements in monitoring strategies through comparative analysis.
A novel approach for optimizing data compression in SHM systems, leveraging model-assisted compressed sensing (CS) to adapt the statistical distribution of sensing mechanisms has been the focus of work for [54].
Their work enhances the efficiency and accuracy of monitoring structural integrity, making it potentially applicable to analyzing the performance of SSDs through comparative analysis.Their concept suggests that SSD monitoring must focus on leveraging model-assisted compressed sensing techniques to enhance the monitoring framework.This involves utilizing advanced algorithms such as the Rakeness-based compressed sensing (Rak-CS), model-assisted Rakeness-Based CS (MRak-CS), and wavelet packet transform (WPT) to reduce the amount of data required for accurate monitoring, thereby increasing efficiency and reducing costs.Specifically, integrate compressed sensing with a predictive model of the dampers' behavior under various loads and conditions.By doing so, we can achieve a more precise comparative analysis of damper performance, identifying subtle changes in behavior that may indicate damage or wear more effectively than traditional methods.The study of Ren & Lissenden in 2016 [80] explored the use of polyvinylidene fluoride (PVDF) sensors for detecting and analyzing Lamb waves in structures, which is essential for SHM.These sensors offer advantages like low profile, low mass, minimal influence on wave propagation, and the capability to conform to curved surfaces.Given their ability to efficiently capture and analyze wave modes and their interactions with structural damage, this technology could be applied to measure the performance of SSDs through comparative analysis.Specifically, the sensor's ability to identify mode conversions and characterize damage makes it a promising tool for evaluating the effectiveness of SSDs in dissipating seismic energy.Ran et al. [53] worked on a novel fiber sensor for vibration sensing, leveraging the single mode-no core-single mode (SM-NC-SM) structure based on multimode interference (MMI).This sensor demonstrates high sensitivity and a wide frequency detection range from 100 Hz to 29 kHz, making it suitable for real-time vibration monitoring.Given its attributes, this technology could be effectively applied to comparative analysis in measuring the performance of SSDs by enabling precise monitoring of vibrational characteristics and structural integrity, offering a new dimension to SHM strategies.

C. DATA VALIDATION TECHNIQUES
A real-time virtual sensing method by Kong et al. [81] using FBG sensors for dynamic vibration monitoring of structures directly estimates vibration parameters like displacements, rotational angles, angular rates, and accelerations from measured strains, utilizing Birkhoff interpolation for algebraic displacement-strain relationships and tracking differentiators for noise attenuation.These techniques offer precise and real-time estimation capabilities, making them applicable for monitoring the performance of SSDs, especially in terms of enhancing accuracy and efficiency in data validation within vibration-based monitoring systems.Contreras and Ziavras [52] introduced a WSN for SHM that is particularly applicable to SSD.This system employs an output-only approach, utilizing statistical features calculated from ambient structural vibrations to assess the condition of structures without the need for controlled stimuli.By treating these features as random variables and establishing baseline healthy conditions, the system can efficiently detect deviations indicating damage.This methodology, with its focus on minimal computational requirements and efficient data transmission, could be adapted for monitoring SSD by providing a cost-effective, scalable solution for real-time damage assessment.A novel, model-based compressive sensing strategy optimized for vibration monitoring was introduced by Zonzini et al. in 2021 [54].Their strategy, validated through experiments on a steel beam, leverages the MRak-CS sensing scheme to achieve higher compression ratios while maintaining the quality of reconstructed structural parameters.This method's adaptability and effectiveness, even in defective configurations, suggest its potential applicability for real-time, efficient monitoring of SSD, offering a promising avenue for enhanced data validation techniques in vibration-based monitoring systems.

D. BENEFITS AND DRAWBACKS
Table 1 compiles various research articles on the benefits and drawbacks (Fig. 9, section D) of employing different damping technologies, including SSDs (SSD), in SHM systems.This organized presentation aids in understanding the comparative advantages and potential limitations of SSD and other damping solutions in enhancing the resilience and safety of structures against seismic and dynamic loads, serving as a crucial reference for engineers and researchers in the field of SHM.

E. APPLICABILITY IN STEEL STRUCTURE CONSTRUCTION
A handful of studies considered innovative approaches and comparative analyses in SHM of steel structures.For instance, we found out that Liu et al. [44] directly addressed monitoring strategies for steel structures, emphasizing quality management.Contreras and Ziavras [52] explored cost-effective monitoring strategies broadly applicable to steel structures and Ran et al. [53] discussed the principles that can be applied to the dynamic behavior of steel structures.

F. PROPOSED MAINTENANCE STANDARD
Presenting a standardized method for improving the maintenance of SSDs through vibration-based SHM provides  professionals in the field with a comprehensive and systematic guide.The accompanying diagram shown in Fig. 10 leads professionals through well-defined steps, commencing with the identification of specific monitoring objectives tailored to the unique characteristics of SSDs.Incorporating common objectives derived from literature, such as anomaly detection and performance optimization, the method ensures a holistic understanding of the monitoring goals.The selection of monitoring strategies is a critical step, involving consideration of the specific context of SSDs and conducting efficient comparative analyses to choose the most suitable sensor technologies.Professionals are then guided through the implementation of robust data validation techniques, enhancing the reliability of collected data through calibration procedures and error handling protocols.The diagram also facilitates a balanced analysis of benefits drawbacks associated with chosen monitoring strategies, enabling professionals to make informed decisions based on factors cost-effectiveness and real-time capabilities.By incorporating advances and innovations from literature, such as IoT-based monitoring and fiber optic sensors, the method ensures that practitioners stay at the forefront of technology, fostering continuous improvement in the monitoring process.Finally, the application of monitoring strategies involves the regular collection and analysis of data, allowing professionals to adjust their approach based on ongoing assessments, ultimately contributing to the long-term reliability and performance optimization of SSDs.This standardized method provides a clear roadmap for professionals, offering a systematic and informed approach to enhancing the maintenance practices of SSDs within structural applications.

VII. CONCLUSION
This research paper reported the answers to the research question focused on the latest advancements and innovation trends in vibration-based SHM.We have systematically presented literature helpful in understanding currently applied and potential practical criteria, data gathering, experimental settings, and advance approaches for research focused on SSDs.
This study is significant for the field of civil engineering and SHM.The significance can be summarized in terms of the value added and the benefits displayed in Fig. 11.

A. INFORMED DECISION-MAKING
By synthesizing and analyzing current advances and best practices in vibration-based monitoring techniques, alongside the application of SSDs, this SLR equips engineers, researchers, and practitioners with comprehensive insights.It guides decision-makers in making informed choices regarding sensor selection, data acquisition protocols, and experimental para meters.The result is a significant value addition to the realm of SHM.

B. ENHANCED STRUCTURAL SAFETY
The core value of this research is its potential to enhance structural safety.It delves into the applications and functions of vibration-based monitoring techniques, providing a deeper understanding of how these techniques can be optimally applied.Through informed decision-making, the study contributes directly to the safety and longevity critical structures, ultimately saving lives and resources.

C. OPERATIONAL EFFICIENCY
Practical implications extend to operational efficiency.By optimizing the utilization of vibration-based monitoring techniques, engineers can streamline maintenance procedures, reduce downtime, and minimize operational costs.This not only adds value but also directly benefits the stakeholders involved in the maintenance and operation of structures.

D. ENVIRONMENTAL RESILIENCE
An often-overlooked aspect is the study's alignment with environmental preservation objectives.The integration of these monitoring techniques and dampers enhances structural resilience, thereby mitigating the environmental impact of structural failures.This contribution to environmental sustainability represents an essential value addition to the study.

E. GLOBAL IMPACT
The insights gained through this SLR hold global significance, shaping best practices and informed decision-making in the broader field of civil engineering and SHM.In essence, the value of this study is underlined by its potential to elevate the standards of SHM, enhance safety, increase operational efficiency, and contribute to environmental preservation.

FIGURE 2 .
FIGURE 2. PRISMA flow of the study.

FIGURE 3 .
FIGURE 3. Distribution of included articles with respect to countries of origin.

FIGURE 4 .
FIGURE 4. Distribution of included articles with respect to publishing journals.

FIGURE 5 .
FIGURE 5. Advancements in SHM: a comprehensive overview of sensor technologies, monitoring techniques, and applications in civil infrastructure.

FIGURE 6 .
FIGURE 6. Conceptual framework for the applications and functions of vibration-based monitoring techniques in real-time SHM with SSDs.

FIGURE 7 .
FIGURE 7. Practical implementations and applications of diverse monitoring technologies (a.Cyber-physical codesign architecture; b.Data-driven SHM using feature fusion and hybrid deep learning; c.Cylindrical dielectric resonator; d.Chipless RFID sensor; e. Fiber bragg grating).

FIGURE 8 .
FIGURE 8. Optimal sensor selection criteria, data gathering methodologies, and experimental settings.

FIGURE 9 .
FIGURE 9. Innovative approaches and comparative analyses in SHM of SSDs.

TABLE 1 .
Benefits and drawbacks.