Ambient Vibration as a Basis for Determining the Structural Behaviour of Watchtowers against Horizontal Loads in Southeast Spain

Abstract

The Kingdom of Granada occupied the southeast of the Iberian Peninsula, what today would be the current Spanish provinces of Granada, Malaga and Almeria. Having succeeded the Nasrid kingdom of Granada (1238–1492), it remained a geographical and administrative unit until 1834, defended from the advancement of Castilian troops by means of a large network of watchtowers located principally along its inland border. Following the Castilian conquest of Granada, the extensive coastline was also strengthened with a network of towers and fortifications that were progressively adapted to house artillery. A technical survey focusing on the characteristics of their geometrics and construction, as well as their performance in a series of non-destructive tests, such as ambient vibration testing, was undertaken to study the towers’ mechanical strength against both gravitational and seismic loads. The results propose a numerical estimate that defines the fundamental frequency of this type of structure, which in turn can be used to approximate the mechanical properties of the masonry. Such a precise definition based on objective data enables accurate and rigorous numerical analysis of this defensive architecture, thus reducing uncertainties. Furthermore, slenderness is found to be a relevant parameter for adjusting fundamental frequency and for analysing the towers’ historical evolution, enabling their initial height and number of levels to be estimated.

An Open Database to Evaluate the Fundamental Frequency of Historical Masonry Towers through Empirical and Physics-Based Formulations

“…In 2017, the Ziegler consultant group [21] published a report for the dynamic assessment of 18 masonry towers in Switzerland (Z collection). In 2020, Ruiz-Jaramillo et al [22] conducted a large-scale survey of 21 watchtowers along the Southeast Spanish coast, providing valuable data for low-rise masonry towers (RJ collection). As part of the ACROSS ANR project, Mercerat et al [23] identify the modal parameters of six medieval bell towers in the Mugello area (Tuscany, Italy).…”

“…Italy contributes most extensively to the collection of instrumented towers (44% of instrumented towers), resulting from a dense slender heritage, one of Europe's most significant seismic activities, and a preservation policy since the last damaging Italian earthquakes. [7], SC [17,18], RF [19], LI [20], Z [21], RJ [22], ACROSS [23]. The 2008 L'Aquila and 2016 Amatrice seismic events are reported with a red star.…”

“…Graph of publication year for dynamic identification of slender Cultural Heritage towers in the compiled database for this study. The main previous database collections are indicated with black edge bar: LU [7], SC[17,18], RF[19], LI[20], Z[21], RJ[22], ACROSS[23]. The 2008 L'Aquila and 2016 Amatrice seismic events are reported with a red star.…”

Defensive Architecture of the Mediterranean Vol. XIV (FORTMED2023)

“…En lo referente al comportamiento estructural de las torres, durante el proceso de inspección se han llevado a cabo una serie de ensayos de vibración ambiental. Estos han permitido obtener información directa sobre la frecuencia/período fundamental de vibración y, a través de ello, determinar el módulo de elasticidad estático homogeneizado para toda la construcción (Ruiz-Jaramillo et al 2020). Este parámetro resulta de gran interés para calibrar el comportamiento estructural de los modelos numéricos tridimensionales creados con precisión a partir de la toma de datos fotogramétrica.…”

Exploration and Characterization of Dynamic Properties for Cultural Heritage Conservation: A Case Study for Historical Stone Masonry Buildings in Zanzibar

“…To bridge the gap in terms of establishing the relationships between experimental investigations with simulation outcomes, a few studies were found in the literature to assess the dynamic response of traditional masonry structures. For instance, Gentile and Saisi (2007) deployed finite element analysis (FEA) to assess the ambient dynamic response of a 74 m tall bell tower built in the 16th century [20,[25][26][27][28][29][30]. By integrating material properties in conjunction with geometry, slenderness ratio, and establishing boundary conditions to solve the equations of motion, the model was simulated under ambient environmental conditions.…”