PSI - Issue 78

Florence More et al. / Procedia Structural Integrity 78 (2026) 944–951

945

1. Introduction Structural timber has long been celebrated as a construction material due to its abundance, renewable nature and aesthetic appeal. In recent decades it has re-emerged as a structural material in modern architecture and engineering, particularly depending upon the introduction of the engineered timber products (GluLam, Cross-Laminated Timber, etc.) (Sandoli et al. 2016). They have enabled the construction of increasingly ambitious and complex structures, including long-span bridges, multi-story residential buildings and landmark architectural projects. The mechanical properties of timber are strongly influenced by environmental factors such as moisture content and temperature, resulting in a time-dependent behavior - i.e. creep - highly sensitive to the surrounding environmental conditions. Furthermore, timber is susceptible to biological deterioration, including fungal decay and insect attack, which can significantly compromise structural integrity if not detected and mitigated in time, particularly for structures located in seismic-prone areas (Riggio et al. 2019; Amaddeo et al. 2025). In such a context, Structural Health Monitoring (SHM) emerges as a fundamental technique to control the service conditions of timber structures, engaging a multidisciplinary domain spanning from civil and structural engineering, material science, data analytics and even biology. SHM refers to the systematic observation and service assessment of structures through the deployment of sensors and data analysis tools to detect, locate and quantify damage or other deterioration forms . For timber structures, SHM serves as a critical safeguard, compensating for the material’s variability and its dynamic response to environmental factors. A diverse array of sensing technologies for SHM in timber structures is currently available, ranging from conventional electrical resistance strain gauges and accelerometers to advanced fiber optic sensors and wireless sensor networks. These sensors can measure a variety of physical and mechanical parameters, including strain, displacement, acceleration, temperature and moisture content (Baas et al. 2020, Palma et al. 2020). The selection of appropriate sensors and measurement strategies is crucial to ensure accurate and reliable monitoring, especially given the complexity of geometries and composite nature of modern and ancient timber elements and of base material. Moreover, the integration of sensors within timber structures, whether embedded during manufacturing or installed on-site, presents unique challenges and opportunities. They can provide continuous, high-resolution data throughout a structure’s lifecycle but must withstand harsh environmental conditions and potential damage during fabrication (Mardanshahi A et al. 2025). By contrast, surface-mounted sensors, while easier to retrofit, may be more vulnerable to external impacts or environmental exposure. This paper aims to provide a state-of-the-art review about SHM methods, sensors and their practical applications to timber structures, serving as a valuable resource for researchers, engineers and industry practitioners operating in the sector or that are approaching. The paper outlines the fundamental concepts and objectives of SHM in the context of timber construction, including its role in damage detection, localization and prognosis, particularly in evaluating the service performance of timber structures, also during and after earthquakes. Moreover, it delves into an examination of the various sensor technologies employed in timber SHM, discussing their operating principles, strengths, limitations and suitability for different applications. Real-world applications of SHM in timber structures are also explored, ranging from laboratory-scale experiments that validate sensor performance to full-scale field deployments in bridges, buildings and cultural heritage structures. These case studies provide valuable insights into the practical challenges of SHM implementation, as well as the innovative solutions developed by engineers and researchers to address these challenges. 2. Factors affecting the serviceability of timber structures Maintaining the integrity and the durability of structural timber elements is essential, particularly in seismically active regions where earthquake can cause damage and collapse of structures. One of the most critical factors influencing the performance of timber elements is the Moisture Content (MC). Timber is a hygroscopic material that absorbs or releases moisture depending on the environmental conditions such as humidity, temperature, solar radiation and wind. Fluctuations in moisture content, especially below the fibre saturation point (~30%), can significantly affect the physical and mechanical properties of wood, including swelling, shrinkage, density, sound propagation, electrical resistance and strengths and elastic moduli. Excess of moisture weakens the timber material, modify the dynamic