The Italian building heritage is aged and inadequate to the high-performance levels required nowadays in terms of energy efficiency and seismic response. Innovative techniques are generating a strong interest, especially in terms of multi-level approaches and solution optimizations. Among these, Nested Buildings, an integrated intervention approach which preserves the external existing structure and provides a new structural system inside, aim at improving both energy and structural performances. The research presented hereinafter focuses on the strengthening of unreinforced masonry (URM) buildings with cross-laminated timber (CLT) panels, thanks to their lightweight, high stiffness, and good hygrothermal characteristics. The improvement of the hygrothermal performance was investigated through a 2D-model analyzed in the dynamic regime, which showed a general decreasing in the overall thermal transmittance for the retrofitted configurations. Then, to evaluate the seismic behavior of the coupled system, a parametric linear static analysis was implemented for both in-plane and out-of-plane directions, considering various masonry types and connector spacings. Results showed the efficiency of the intervention to improve the in-plane response of walls, thus validating possible applications to existing URM buildings, where local overturning mechanisms are prevented by either sufficient construction details or specific solutions.

Masonry arch bridges, despite their age, are still fundamental structures in transport networks throughout Europe, especially for railways. Furthermore, these bridges are often found in seismic-prone areas, such as Italy. Developing of specific fragility models is of fundamental importance for large-scale seismic risk assessments of these structures and related transport networks. Unlike other types of bridges, for which significant progress has been made in assessing their seismic vulnerability and fragility, comparable results for masonry arch bridges are not fully available. Moreover, a realistic risk assessment of masonry bridges should account for deterioration and damage, which most of these bridges have developed being more than 100 years old and often in a poor state of maintenance. Therefore, this work intends to provide seismic fragility models for two generalised classes of single-span masonry arch bridges, i.e. segmental and semi-circular, taking into account their potential degradation through 2 D finite-element modelling and parametric nonlinear static analyses. Material loss from the intrados of the arch, material degradation, and longitudinal cracks on the arch barrel vault are investigated as typical defects. Overall, the seismic fragility of masonry bridges increases appreciably when the effects of degradation are considered, the loss of material being the most influential defect.