STRUCTURAL ANALYSIS OF ACCESS BRIDGES OF THE FORTIFIED ALEXANDRIA CITADEL

In December 2017 the Municipality has placed considerable restrictions on the transit of vehicles on the access bridge to the Gateway; it was consequently highlighted the need to deepen the structural situation of the bridges to guarantee their accessibility especially in emergency situations. That’s why the Ministero dei Beni e delle Attività Culturali e del Turismo - Segretariato Regionale per il Piemonte entrusted to Foppoli Moretta e Associati the execution of a diagnostic campaign with the aim of determining the geometrical and mechanical characteristics of the masonry of the access bridges to the Citadel Gateways.

The diagnostic activities involved both the “Royal Gate” and the “Rescue Gate” access bridges. They requested the execution of:

• exploratory surveys to identify the foundations shape and level;
• core drilling in the pile inspected with videoendoscopy survey to analyse the materials constituting the structural elements and to identify the possible presence of stratified masonry, discontinuities and / or cavities;
• endoscopic inspections in the arches of the vaults to obtain an adequate knowledge of the geometry and thicknesses of the same structures;
• single flat jack and double flat jacks tests in the piles and in the vaults to detect the local stress state and the deformability characteristics of the masonry structures.

The results of the surveys made it possible to acquire useful information to characterize the structure and to provide useful indications for modeling and structural verification of the building and for the subsequent planning and execution of urgent safety works.