Saviano, Felice (2023) Degradation effects on structural safety of masonry walls. [Tesi di dottorato]

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Abstract

Assessing the vulnerability of buildings exposed to various climate conditions, which can severely influence durability and long-term performance, is a challenging topic in both research and engineering practice. Degradation affects all types of buildings across the world, differing in the timing and manifestation, for which specific rehabilitation measures are required. Most of the research activity in the last decades, was focused on seismic actions, even if analysis and rehabilitation against gravity loads represent a major challenge especially for historical buildings, mainly if degradation is the main reason for safety reduction. In this framework, this thesis aims at the quantitative assessment of the effects of aging and material degradation on structural safety. In order to reproduce a geometric degradation of mortar joint, tests have been carried out by reducing mortar joint’s width to simulate a typical form of aging in masonry, without an attempt to model the physical processes of material aging. Tests have concerned in a first phase both small scale masonry wallets of brick and tuff masonry then in a second phase full-scale unreinforced masonry (URM) walls with an opening were tested under different load schemes. Both in plane and out of plane loads were considered.In terms of in plane loading, a severe risk for existing buildings is represent by settlement at the base, on the other hand, out of plane load is significant to account for walls not being firmly connected to horizontal structures with uncounteracted horizontal forces. A further challenge has been the development of numerical analyses to simulate the capacity and behaviour of such walls against ageing effect with a calibration based on the experimental results from axial and diagonal-compression tests. Numerical models of wallets and full scale walls calibrated by using the experimental data confirmed the strength analytical envelopes, the failure mode and remarked the influence of the mechanical properties and their variations. In fact, refined numerical FEM models supported the analytical modelling approach, including a refinement of the spandrels failure criteria, modifying those devoted to piers.

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