Monitoring Deflection and Stiffness in Historic Timber Beams Using Fiber Optic Sensors
Abstract
<p>This paper evaluates a reclaimed fir beam under four-point bending using long-gauge fiber-optic sensors (FOS) and an LVDT to monitor strains, neutral-axis (NA) positions, deflections and global modulus of elasticity (<i>Eₘ,</i>g) as a representative measurement of stiffness. Results from two cam-paigns (before and after introducing cuts to artificially damage the beam) show excellent agreement among sensors and close consistency between FOS and LVDT stiffness estimates. No significant re-duction of <i>Eₘ,</i>g was observed after damage, indicating limited sensitivity of this global metric under the present conditions. In contrast, the NA position consistently shifted below the geometric cen-troid and evolved with load, proving more responsive to localized deterioration. The findings con-firm that FOS-based monitoring, particularly NA tracking, is a reliable, minimally invasive tool to support performance-based assessment and reuse of historic timber elements.</p>
Reference
Roberto Mansilla-Ruiz; Norberto Robayo; Ester Garcia-Castillo; Ignacio Payá-Zaforteza. (2026). Monitoring Deflection and Stiffness in Historic Timber Beams Using Fiber Optic Sensors. IABSE Reports. https://doi.org/10.2749/copenhagen.2026.1392
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