Explosively formed projectiles (EFP) are one of the most severe explosive and impact loading threats for civil infrastructure and military vehicles. EFP warheads are commonly found in conventional anti-tank weapons. They are also regularly used by insurgent forces against armoured vehicles in conflict-affected countries. The energy of EFPs is significantly greater than that of large calibre ammunition, such that a threat is posed to the occupants of armoured vehicles both by perforation and spalling of the armour. This paper aims to present new experimental results of the hypervelocity impact of EFPs on reinforced concrete (RC) columns to demonstrate the vulnerability of infrastructure to EFP improvised explosive devices (EFP-IEDs). As a possible mitigation measure of threat against EFPs, an RC column was retrofitted with a steel-jacket. The ability of a steel-jacket to minimise RC column damage was evaluated where it was found to minimise damage to the RC column and contain concrete fragments. Threedimensional numerical simulations were performed to elucidate the different stages of EFP interaction with the RC columns. No previously published results on the EFP terminal ballistic performance of RC columns have been found in the open literature.

Ultra-High Performance – Fiber Reinforced Cementitious Composites (UHP-FRCC) show excellent mechanical performances, and therefore can be effectively used to retrofit concrete structures. Similarly to the traditional Reinforced Concrete (RC) jacketing, also when a layer of UHP-FRCC is applied on an existing column a sort of confinement can be obtained. Accordingly, the purpose of this study is to investigate the performances of plain concrete cylinders, confined by UHP-FRCC and subjected to uniaxial compression. In some of the layers, high volume fly ash has also been used to replace part of the cement and reduce the environmental impact. As a result, the compressive strength of the concrete core can be enhanced by the presence of UHP-FRCC layer, but when partially using fly-ash, the confinement effect of the jacket reduced. To determine the best solution among the different proposed options, the eco-mechanical analysis was also carried out.

HPFRC micro-concretes represent one of the most interesting results in the construction material research field. Over and above their extremely high compressive strength, these materials are characterized by an exceptional tensile strength and by a deformational capacity (ductility) superior to that of ordinary cement conglomerates. In terms of durability, their particular compact matrix makes them extremely resilient to the environmental deteriorating action.

These properties make this material an absolute protagonist in the field of structural repair and reinforcing, since they allow applications that are not only interesting from a technical viewpoint, but effectively sustainable. In fact, efficient repair work will be possible while keeping dimensions of the sections limited.

This note initially intends outlining the description of a series of experimental tests and the relative lab results obtained on innovative HPFRC products. Specifically, reference will be made to compression tests, tensile and bending-tensile tests, shear tests and adhesion tests to the support.

Next, several possible and interesting applications for repairing/reinforcing structural elements will be described, such as reinforced concrete pillars and beam, as well as floors.

Order to understand the technical benefits afforded by said interventions, useful reference will be made to a specifically developed software application for locally analyzing the reinforced concrete sections subject to structural repairing. Where pillar and beam elements are reinforced, benefits obtained by implementing reduced thickness jacketing will be highlighted, both in terms of bending-compression strength by evaluating the M-N interaction diagram, as well as in terms of the ductility of the section, by assessing the Moment – Curvature relationships.

Instead, as regards the reinforcing works done on floors, the benefits attainable will be described by constructing collaborating slabs of lesser thickness in terms of an increase in carrying capacity, and low deformations and vibrations.

The strengthening of existing reinforced concrete (RC) structures, built according to the Italian construction practice of the ’60-‘70s, has become an important and urgent issue. The reasons for strengthening are the need for: increasing strength to withstand underestimated loads; increasing the load-carrying capacity; and fulfilling the seismic code requirements. A new technique to strengthen existing RC structures, based on the application of a thin highperformance fibre-reinforced jacket, is investigated herein. The application of this technique has been studied for the strengthening of beams, columns and beam-column joints by full scale experimental tests which results showed that the application of a high-performance fibrereinforced concrete (HPFRC) jacket leads to a significant increase in strength of the elements, also reaching an adequate level of ductility. Subsequently, the experimental results are compared with analytical evaluations of the load carrying capacity of the retrofitted elements, showing that the analytical formulations are consistent with the experimental evidence.

After the Kobe earthquake in 1995 in Japan, many reinforced concrete (RC) bridge piers have been strengthened using various techniques, such as steel jacketing and concrete jacketing. It is anticipated that, when the next strong earthquake comes, foundations will possibly be damaged because of the enhanced capacity of the pier. In this paper, the seismic response of reinforced concrete (RC) bridge piers and foundations were evaluated using the substructure pseudo-dynamic (S-PSD) testing method for cases in which strengthening was provided to the pier and foundation. The S-PSD testing method for bridge pier-foundations was first developed. Based on the developed method, damage in a foundation that supported a strengthened pier was investigated through a pier specimen loading. In addition, the response of a strengthened bridge pier with a strengthened foundation was also examined through a foundation specimen loading. The possibility of foundation damage due to pier strengthening and the effectiveness of foundation strengthening were finally confirmed.