International Concrete Abstracts Portal

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.

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.

This paper reports the structural rehabilitation of a 28 story reinforced concrete building. Structural assessment of this building was initiated upon observing damage in one column after five years of service. As a result of this investigation it was concluded that the main cause of damage in the column was temperature induced deformations. A total of 36 circular (spiral) and 46 square (tied) columns were strengthened by steel jacketing. After the completion of rehabilitation, 122 sensors were placed in the building at different locations to monitor the temperature changes and deformations in structural members. In the paper results of seven years of monitoring are also given.

Rehabilitation of structures requires knowledge on the anticipated nonlinear behavior of building components. Column retrofitting using jackets made of different materials, designed to counter deficiencies in the original design, can be used to improve the overall performance of an existing building. This paper presents a procedure to obtain the backbone nonlinear response of jacketed columns based on existing experimental results for this class of elements. Column jacketing has been used in the past to increase ductility and strength of reinforced concrete columns. Jacket designs can be varied to selectively improve the lateral-load response of columns depending on the original design deficiency. A uniform methodology or specific recommendations on how to estimate the response of jacketed columns with different jacket materials types do not exist. Existing experimental data are used to determine the backbone nonlinear response of jacketed columns. These data are then used to develop recommendations to determine non-linear force and deformation parameters of jacketed columns. Although the most common types of jackets used are made from: concrete, steel, and FRP, only the last two are included in this paper. The backbone curves thus generated can then be used in performance assessment of reinforced concrete buildings where columns have been jacketed.

The paper deals with a rehabilitation case study on a pre-stressed concrete (PC) bridge (named “Torrente Casale”), located in the south of Italy (on the Salerno-Reggio Calabria highway). The bridge, built in the ’70s, was enlarged in 2001 in order to satisfy the new traffic demand. A seismic assessment of the bridge resulted necessary in order to verify its capacity to sustain both gravity and seismic loads. Both destructive and non-destructive tests have been performed in order to evaluate concrete and steel reinforcement mechanical properties. A theoretical analysis was performed, showing that the bridge piers existing cross section and internal reinforcement were not adequate to satisfy the seismic actions. Thus, two rehabilitation systems were investigated: a) an innovative technique based on the combined use of Fibre Reinforced Polymer laminates (FRP) and Steel Reinforced Polymer spikes (SRP), b) a traditional rehabilitation technique (i.e. RC jacketing). The design assumptions and calculations for the rehabilitation as well as the comparison between the effectiveness of the two investigated strategies are presented and discussed in the paper. The main construction phases of the strengthening technique, executed by following the first outlined strategy are also presented and illustrated.