This book develops several novel foam-filled structures and steel-concrete-steel (SCS) sandwich structures, which provides more alternatives for ensuring the safety of buildings and infrastructures under extreme loading, like impact and blast. In the first part of this book, the aluminium foam- and polyurethane foam-filled structures have been developed for dissipating impact and blast energy. Experimental and numerical studies have been conducted to obtain their behaviours under impact loading. In addition, analytical models have also been proposed to assess their energy absorption performances and facilitate the impact and blast design when using the proposed foam-filled structures. In the second part of this book, SCS sandwich structures with novel shear connectors have been developed and their behaviours under impact and blast loading have been experimentally, numerically and analytical studied. Analytical models for predicting the impact and blast responses of SCS sandwich structures have also been developed. In the third part of this book, a new steel-polyurethane foam-steel-concrete-steel (SPUFSCS) panel (i.e. the combination of foam material and SCS panel) has been developed to achieve a higher impact resistant capacity. Owing to the increasing impact and blast threats on buildings and infrastructures, the studies presented in this book are of significant importance for providing several new solutions for impact and blast enhancement.