Experimental tests on typical masonry of Messina area (Italy) retrofitted with CAM: A full scale arch

The present paper focuses on an in-situ testing campaign recently developed in the Messina area, Italy, aiming at the assessment of the in-plane shear behaviour of traditional masonry structures retrofitted with the innovative CAM system (a system of 3D pre-tensioned stainless steel ties). The typical masonry of Messina area, is characterised by low mechanical properties, both for its texture and for the bad quality of mortar, as well as lack of transverse connections. The high seismic risk characterizing the zone, amplifies the need for in-plane strengthening and transverse connections improving. The CAM system, Masonry Active Ties or Manufact Active Confining, allows to realise a 3D pre-t…

Safety assessment in N-M-V interaction of prestressed concrete elements subject to degradation of the reinforcements

The estimation of residual life of viaducts and bridges is urgently topical, due to the age of Italian infrastructure network. Among the causes of reduced life of prestressed concrete structures, the role played by corrosion in prestressed reinforcements is fundamental. In fact, the reduction of the reinforcement cross-section with the formation of the outer layer of iron oxides and hydroxides and the bad filling of the ducts, induces an intermediate behaviour between that of external (unbonded) and internal (bonded) prestressing. For these reasons, the evaluation of degradation and its influence on structural safety cannot be neglected in the assessment of sections of existing structures c…

THE REHABILITATION THROUGH EXTERNAL PRESTRESSING OF HISTORICAL REINFORCED CONCRETE BRIDGES WITH REDUCED PERFORMANCE: A CASE STUDY

Many existing reinforced concrete bridges exhibit behaviour at the Service Limit State and the Ultimate Limit State which can be considered unsatisfactory with respect to the current provisions of Codes, but which are actually deficiencies deriving from obsolete calculation methods, structure age, material degradation, diffuse or localized corrosion and increased loads. Among these, cantilever bridges with half-joints may present a decrease in global safety coefficients for the most stressed current sections of the deck or in the local ones, that affect the performance of elements sensitive to degradation, such as Gerber saddles. In these cases, simple strengthening interventions through ex…

Rheological and mechanical properties of self compacting concrete with pumice powder

EXPERIMENTAL INVESTIGATION ON R.C. BEAMS RETROFITTED IN FLEXURE AND SHEAR BY PRETENSIONED STEEL RIBBONS

The experimental results of three and four point loading tests on reinforced concrete beams strengthened by angles and/or pre-stressed stainless steel ribbons (CAM system) are presented. The stainless steel prestressed ribbons play the role of adjunctive transversal reinforcement as well as confine the structural element. Six flexural critical beams and nine shear critical beams were tested. In the first group four beams were retrofitted with bottom stainless steel angles and transversal ribbons, with two different spacing. In the second group three specimens were retrofitted by wrapping the beam with the ribbons, while three specimens were strengthned by perforation of the beam beneath the…

Response behaviour of reinforced concrete beams strengthened in shear with FRP

In this paper an analytical model, able to predict the shear-displacement response of slender RC beams reinforced in shear with FRP, is presented. It allows to evaluate the complete strain and stress fields, for each load step, on the basis of the MCFT framework. The key role of the effective strain of FRP reinforcement at failure has been investigated. At the same time, the interaction FRP-steel stirrups has been taken into account by introducing an appropriate factor. It is able to reproduce the decrease of stirrups stress level when an external reinforcement is used. The proposed model has been validate against a database of specimens collected in literature. Results have shown the remar…