###### Abstract  
In recent decades, the urgency to protect and upgrade cultural heritage structures (CHS) has become of primary importance due to their unique value and potential areas of impact (economic, social, cultural, and environmental). Structural health monitoring (SHM) and the management of CHS are emerging as decisive safeguard measures aimed at assessing the actual state of the conservation and integrity of the structure. Moreover, the data collected from SHM are essential to plan cost-effective and sustainable maintenance solutions, in compliance with the basic preservation principles for historic buildings, such as minimum intervention. It is evident that, compared to new buildings, the application of SHM to CHS is even more challenging because of the uniqueness of each monitored structure and the need to respect its architectural and historical value. This paper aims to present a state-of-the-art evaluation of the current traditional and innovative SHM techniques adopted for CHS and to identify future research trends. First, a general introduction regarding the use of monitoring strategies and technologies for CHS is presented. Next, various traditional SHM techniques currently used in CHS are described. Then, attention is focused on the most recent technologies, such as fibre optic sensors and smart-sensing materials. Finally, an overview of innovative methods and tools for managing and analysing SHM data, including IoT-SHM systems and the integration of BIM in heritage structures, is provided. structural health monitoring; cultural heritage structures; fibre optic sensors; computer-vision based approach; Internet of things paradigm +
Footnote †: journal: _Sci._  
Footnote †: journal: _Sci. raised the interest of the community to evaluate the structural/energy state of the existing buildings, which fulfil both structural and energy upgrading requirements [9; 10; 11; 12]. In contrast, integrating seismic and energy upgrading with systems for smart monitoring of CHS was recently proposed as a concept [13]. SHM involves the process of implementing strategies that serve two primary purposes: (1) to evaluate the current health condition (diagnosis) by analysing the collected monitoring data to determine the occurrence, location, and severity of damage [14]; and (2) to predict the future performance (prognosis) of the monitored structure, which is based on predictive models and algorithms [15; 16; 17]. The diagnosis and prognosis processes, combined with the basic knowledge of damage mechanisms and behaviour laws, aim to plan the health management (organization of maintenance strategies, repair interventions, etc.) of the structure [15; 18]. While there is no current reference standard for SHM in CHS, the importance of monitoring for the conservation of CH buildings has been highlighted by various guidelines, such as the ICOMOS/ISCARSAH committee's Guidelines on the Analysis, Conservation, and Structural Restoration of Architectural Heritage [19] and the Italian guidelines for assessing and mitigating the seismic risk in CH structures [20]. These guidelines embrace the ICOMOS/ISCARSAH principles [21] based on the need for scientific and cultural insight in the study and care of architectural heritage while minimizing interventions to optimally combine structural requirements with heritage preservation and authenticity. SHM for CHS can increase understanding of structural behaviour, estimate the need for strengthening, control damage progression, and evaluate the effectiveness of incremental strengthening interventions. The field of SHM is wide ranging and includes many techniques that can be grouped according to various classification criteria.