0000000000104031
AUTHOR
M. F. Granata
Influence of bond deterioration on shear-flexure failure of prestressed girders with post-tensioned tendons
Internal prestressing with bonded tendons suffers corrosion of wires and bond deterioration due to the bad infill of grouted sheaths. Many bridge girders show this state through cracking, deflections and in the worst cases, sudden failures. In Italy these are common situations, and the internal tendon corrosion is among the major causes of bridge degradation and damage, especially for grouted post-tensioned tendons. This paper presents the analysis of failure of prestressed cross-sections considering shear and flexure in the case of bond deterioration due to corrosion of internal post-tensioned tendons. The structural behaviour is analysed for different typologies of bridge deck composed of…
The Rehabilitation of Segmental Bridges Subjected to Time-dependent Deflections Through Additional Prestressing
Segmental bridges built by cantilevering with in-situ casting in the ‘60s-‘80s of the XX Century present a central hinge on the main span or a central simply supported span between the two cantilevers (drop-in span). Due to time-dependent phenomena like creep of concrete and to unexpected loss of prestressing, several bridges of this typology show an abnormal deflection at hinges causing discomfort of traffic as well as insufficiencies of checks at Service and Ultimate Limit States. Moreover, these bridges are today at the end of their nominal service life, impacting significantly on Italian road network. A methodology for retrofitting these bridges by partial recovering of deflection and o…
Degradation and rehabilitation of Gerber saddles of concrete bridges
In recent decades, many concrete bridges, built in the 60s and 70s of the 20th Century with a Gerber-girder scheme, show severe damage of the saddles due to concrete degradation and reinforcement corrosion. On the basis of the recent Ministerial Guidelines for the assessment of existing bridges, it is necessary to evaluate the state of the Gerber saddles in a large number of bridges on both main and secondary roads. To do this, it is necessary to apply flexible assessment procedures that can be adapted to several situations and that allow a speedy assessment of the intervention priorities. The methodologies of intervention represent the crucial point for a rapid rehabilitation of these infr…
Case-studies of corroded reinforced concrete bridges in Southern Italy
On Italian roads, a lot of reinforced concrete bridges were built in the 1950’s and 1960’s for short spans, before the advent of prefabricated structures. Many of these bridges, sited on principal or secondary roadways, show the effects of corrosion of reinforcements and high levels of damage, leading to the likelihood of achievement of the Ultimate Limit State, below the required performances of serviceability, especially in the case of Gerber saddles having strongly corroded reinforcements. Different case studies of bridges sited in Southern Italy (Sicily) are shown, allowing engineers to classify the main effects of damage in corroded structures with the Gerber static scheme (cantilever …
Applicazione delle Linee guida italiane alle valutazioni di sicurezza strutturale del ponte Corleone sulla tangenziale di Palermo
The "nominal life" of a large part of existing reinforced and prestressed concrete bridges, in Italy, is expiring, often in the absence of ordinary or extraordinary maintenance. Consequently, the Italian infrastructural network is in a critical phase, followed by the alarmed awareness of the public opinion, especially after the collapse of the Polcevera viaduct. Specific guidelines on risk classifi-cation, management, safety assessment, monitoring of existing bridges have been issued by the Superior Council of Public Works in 2020, to address the emergency. Between ‘50s and ‘70s of the last century, important examples of reinforced and prestressed concrete bridges were built in Italy by the…