Search results for "bridge"
showing 10 items of 355 documents
The Rehabilitation of Segmental Bridges Subjected to Time-dependent Deflections Through Additional Prestressing
2022
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…
Enhanced steatosis by nuclear receptor ligands: a study in cultured human hepatocytes and hepatoma cells with a characterized nuclear receptor expres…
2010
Steatosis is the first step in the development of non-alcoholic fatty liver disease (NAFLD). However, the mechanisms involved in its pathogenesis are not fully understood. Many nuclear receptors (NRs) involved in energy homeostasis and biotransformation constitute a network connecting fatty acids, cholesterol and xenobiotic metabolisms; therefore, multiple NRs and their ligands may play a prominent role in liver fat metabolism and accumulation. In this study we have attempted to gain insight into the relevance of the NR superfamily in NAFLD by investigating the steatogenic potential of 76 different NR ligands in fatty acid overloaded human hepatocytes and hepatoma cells. Moreover, we have d…
Composition of the essential oil of allium neapolitanum cirillo growing wild in sicily and its activity on microorganisms affecting historical art cr…
2015
Essential oil of the aerial parts of Allium neapolitanum Cirillo collected in Sicily were analyzed by gas-chromatography-flame-ionization detection and gas-chromatography-mass spectrometry. Nineteen compounds were identified in the oil and the main components were found to be (E)-chrysanthenyl acetate (28.1%), (Z)-chrysanthenyl acetate (23.8%), (E)-β-farnesene (9.6%), dimethyl trisulfide (9.6%), camphor (7.4%), methyl allyl disulfide (6.8%) and 1-methyl-3-allyl trisulfide (5.8%). The essential oil showed good antimicrobial activity against 11 strains of test microorganisms, including several species infesting historical material.
Condition Assessment of Norwegian Bridge Elements Using Existing Damage Records
2020
The Norwegian Public Roads Administration (NPRA) has recorded bridge element damages in a database for all the bridges it manages since the 1990s. This paper presents a comparison of three methods to establish element condition based on damage records. The methods consist in a non-parametric procedure based on the worst damage registered in the element, linear regression considering also bridge and road characteristics data and classification through an artificial neural network. The methods are assessed using a set of 159 bridges inspected in 2016. The results show that diagnostics of bridge element condition can reach high accuracy by using an artificial neural network classifier and taki…
La variazione di schema statico nei ponti in cemento armato precompresso durante le fasi costruttive e l’influenza dei fenomeni lenti
2018
The construction of prestressed concrete bridges often presents different construction stages in which the structural static scheme changes many times, together with the characteristics of the construction elements. In fact, prefabrication and in situ assembly involve a multiple variation of the scheme with the introduction and removal of restraints, especially when temporary sup-ports are used. These transitional phases can strongly modify the structural behavior, in relation also to the deformations due to shrinkage and creep. In this study an evaluation of the effects of time-dependent phenomena is presented, for the case of complex sequences in which delayed restraints and removal of pr…
Effect of degradation on the structural behaviour of an existing cantilever reinforced concrete bridge in Southern Italy
2021
The performance of cantilever reinforced concrete bridges is fundamental topic in assessment and retrofit of Italian infrastructures, because the static scheme of the so-called “Gerber bridges” was very popular between 50’s and 70’s of XX Century. Many of them present severe damage due to the drainage of the deck waters inside the joint and to the consequent degradation of Gerber saddles. Furthermore, the state of corrosion of the reinforcements together with the actual degree of freedom of internal constraints, often partially blocked due to degradation and subsequent maintenance over time, modify the structural behaviour and the performance both in terms of service and ultimate limit stat…
Safety assessment in N-M-V interaction of prestressed concrete elements subject to degradation of the reinforcements
2021
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…
CONCEPTUAL DESIGN OF BOWSTRING BRIDGES WITH STRESS RIBBON TIE
2011
In this paper the conceptual design of tied-arch bridges is examined. A proposal for a particular kind of bowstring bridges, with an upper deck and a stress ribbon footbridge placed between the arch footings is discussed. The double structure allows to avoid horizontal forces into foundations when functional requirements lead to differentiate pedestrian and road traffic. After a general discussion about classical tied-arches, the main parameters involved in the design of the proposed solution are discussed and a case-study is presented.
Degradation and rehabilitation of Gerber saddles of concrete bridges
2022
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…
Michelangelo Blasco versus Ferdinando Fuga: una nuova attribuzione per il ponte sul Milicia in Sicilia
2015
The finding at the National Library of Spain of an eighteenth-century engraving of the bridge over the river Milicia, along the coast to the east of Palermo, is a chance not only to shed light on the complex history of the design and construction of one of the main Sicilian bridges, but also to attribute the real paternity rather than to the famous architect Ferdinando Fuga to the lesser-known military engineer, serving the Austrian Crown, Michelangelo Blasco, whose long and successful career is reconstructed: from Sicily, through Milan, Wien and Lisbon, to the uncharted territory of Brazil.