Differential Settlement in Historic Masonry Towers: The Case of the Murcia Cathedral Bell Tower

Abstract

The bell tower of Murcia Cathedral (1521–1793) exhibits a documented inclination whose origin and structural significance have never been examined through an integrated geotechnical–structural approach. This study aims to identify the causes, quantify the magnitude, and assess the safety implications of the tower’s long-term differential settlement. A multidisciplinary methodology is adopted, combining historical construction records, geological and geotechnical data from the Segura alluvial plain, non-destructive testing of masonry, and classical analytical modelling based on Heyman’s masonry theory, consolidation mechanics, and elastic column behaviour. This approach is selected in place of finite element modelling because the tower’s geometry, construction sequence, and material parameters are sufficiently constrained to allow a non-invasive and verifiable assessment suited to heritage structures. Results indicate a total horizontal displacement of approximately 0.56 m toward the northwest, produced by the slow consolidation of compressible silty–clayey deposits influenced by groundwater fluctuations and by historical eccentric load redistributions during the eighteenth-century construction phase. The calculated working compressive stresses (0.83–1.02 N/mm2) remain far below the estimated strength of the limestone masonry, and the bearing capacity analysis suggests a safety factor of about 1.5 against foundation failure. These findings confirm that the tower’s deformation reflects the long-term geotechnical response of the subsoil rather than structural instability. The study provides a non-destructive analytical framework for interpreting settlement mechanisms in historic masonry towers and contributes a quantitatively grounded explanation of the Murcia Cathedral tower’s inclination, offering guidance for future assessment of similar heritage structures.