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.

Unreinforced masonry has been for centuries one of the most widespread constructive techniques for both massive structures and civil buildings (e.g., palaces, hospitals, houses), for the most still standing nowadays. Their future conservation relies on (i) their protection from main natural threats (e.g., earthquakes) and (ii) updating to current functionality and hygrothermal standards. In the former framework, existing masonry buildings proved to have some intrinsic vulnerabilities, depending on composition (units and binder) and structural typologies. Based on experience gathered from seismic events, various retrofitting techniques have been proposed. In such a context, the use of cross-laminated timber (CLT) components is a very promising solution, in terms of compatibility with built heritage and integration of seismic and hygrothermal performances. This paper aims at improving the knowledge of the structural performances of compound timber–masonry interventions by numerical simulations carried out at (i) pier scale and (ii) building full scale via finite element modeling and nonlinear static analyses (pushover). First, a coupled timber–masonry wall was simulated and underwent sensitivity analyses with the properties of both components varying; then, the optimized solution was applied to a case study to assess the intervention benefits, and the results were also cross-checked with those of more traditional interventions (e.g., grout injections).

The Temple of Apollo Pythios in Gortyn (Crete, Greece) dates back to the mid-7th century BC. The temple underwent several transformations and an ultimate destruction over time that resulted in the current remains of a Roman colonnade composed of six fragmented stone columns lying on the ground within the naos. In addition, the region was struck by several earthquakes which contributed to the various changes. The analysis of the fragments composing the column portions and their geometric features provided a possible outline for their standing repositioning. Based on the current seismic hazard of the region, a predictive numerical model of the colonnade in the anastylosis conditions suggested the need for proper connections between the fragments and the bases to ensure their overall conservation as a compound structure. The comparison of various configurations of intervention and the simple superimposition of the fragments also provided details on the accomplishment of minimal and compatible solutions.