Currently, the significant increase in devastating seismic events has made the technical, scientific and political communities aware of the seismic vulnerability of buildings located in highly exposed urban areas. In historical centres, the conspicuous construction heterogeneity, conjunctly with the intrinsic typological–structural deficiencies of some buildings, negatively influences their global behaviour against earthquakes. As it is known, existing buildings in urban areas are potentially at risk due to the precarious behaviour caused by age and lack of maintenance, which make risk very complicated to predict. In general, the buildings in historical centres are often arranged as building compounds made of a non-homogeneous set of interacting structural units (SUs) built in different historical periods and characterized by architectural, material, and functional complexity, such as to make the clustered structure ineffective against seismic actions. The pre-code and a low standard design have brought out an evident lack of structural and non-structural details, that have slavishly altered the assets of these buildings.

In this case, the assessment of seismic vulnerability is a useful strategy for planning and mitigating any systemic crises to safeguard buildings of immeasurable architectural and cultural value. To cope with this structural inadequacy, it is essential to intensify the cohesion between analytical innovation and consolidation techniques for developing a more sophisticated structural process to globally improve the conservation of buildings exposed at risk.

Based on the previous premises, this Special Issue aims to encourage the dissemination of ideas and knowledge concerning the assessment and reduction of the seismic vulnerability of existing buildings, favouring interdisciplinarity between architectural and engineering issues. To this intent, original contributions are welcome that contain fundamental and applied research, case studies or discussions on the state of the art of the following topics:

(1) Seismic vulnerability:

Evolution; conceptual understanding; historical analysis and future multidisciplinary perspectives; failure detection and diagnosis systems; inventories and intelligent digitized structures.

(2) Vulnerability assessment methods and tools:

Empirical approaches; mechanical analytical methods; advanced numerical simulation; large-scale evaluation methods; analysis of systemic fragility; GIS approach.

(3) Seismic consolidation and retrofit techniques, architectural–functional conservation:

Traditional and innovative strategies; cost–benefit analysis; Experimental tests; development and validation; analytical and numerical simulation; application cases; post-earthquake surveys; conservation, protection, and prevention; architectural and functional redevelopment.

This entry collection is aimed to collect high-quality original entries for the journal Encyclopedia (https://www.mdpi.com/journal/encyclopedia).