Assessment of Strength Degradation of Historic Masonry Monuments due to Damage: Load Path–Based Approach

Abstract

Historic masonry monuments experience aging and accumulated damage, which consequently degrade both their stiffness and strength. Stiffness degradation can be quantified through nondestructive testing and has been widely used to determine the onset of structural damage by monitoring the changes in monuments’ dynamic behavior. For justifying and configuring repair and rehabilitation activities, strength degradation (i.e., loss in load-carrying capacity) provides a more relevant indicator than does stiffness degradation. However, strength degradation is also significantly less feasible to assess because it requires the use of destructive testing. In this paper, the authors estimate strength degradation by establishing an empirical relationship between loss in structural redundancy due to damage and the corresponding loss in load-carrying capacity. Here, structural redundancy is represented as the ability of the structure to accommodate the applied load through alternative load paths. Loss in structural redundancy is approximated as the disturbance in the load path due to the development and progression of cracks. The proposed redundancy measure is demonstrated on a historic masonry coastal fortification considering differential settlement of supports.