In the last few decades, numerous tragic accidents highlight the need to build and retrofit structures and facilities, to better protect the occupants in the event of extreme loading conditions, including terrorist or mass-casualty attacks, natural hazards, and disasters. This is the case of critical civil infrastructures such as embassies, government buildings, airports, hospitals, or bridges, where continuous and effective protection tasks have a key role in preventing injuries and in providing appropriate service, even in the case of emergencies. The definition of the so-called "soft targets" can then be generalised and extended to mostly open areas and spaces, accessible to the public however particularly vulnerable to attacks.

From a practical point of view, the design of protective structures or the definition of hazard mitigation systems requires multiple functions and reasonable safety criteria, according to the intrinsic features of possible target structures. To this aim, several research studies have been dedicated in the last years to the assessment, enhancement, and protection of civil engineering materials, components, and complex structural systems, including refined numerical simulations, experimental investigations, and analytical studies at the component and/or assembly level.

The aim of this Special Issue is to solicit original research articles and review articles, providing an insight of recent advancements in the design, and analysis of protective structures, especially related to engineering applications. These may include buildings, infrastructures and bridges, defense facilities, as well as industrial plants, pipelines, offshore platforms, shipping, and offshore/underground structures.

Potential topics include but are not limited to the following:

• Analysis, design, assessment methods, and retrofitting techniques for soft targets
• Hazard sources, including classification, measurement methods, and analytical/numerical description
• Risk and failure analyses
• Design methods against terroristic and mass-casualty attacks, with careful consideration for hazard mitigation solutions
• Blast damage assessment
• Advanced numerical simulations
• Experimental investigation and performance assessment of materials, structural details, and assemblies