Analysis of the low-cycle fatigue behaviour and corrosion phenomena on reinforcing bars of concrete structures in earthquake prone areas

In the present work, the combined effects of Low-Cycle Fatigue (LCF) action and corrosion phenomena on steel reinforcing bars were accurately investigated, aiming at the definition of the effective seismic mechanical capacity of steel bars in comparison to what required by real earthquake events. The ability of corroded specimens to still sustain the ductile demand (in terms of strain and dissipated energy) of seismic events was accurately investigated. The thesis was developed inside the widest framework of an European Research project, (Effects of Corrosion on Low-Cycle Fatigue (Seismic) Behaviour of High Strength Steel Reinforcing Bars, 2009), funded by the Research Fund for Coal and Steel. The necessity to investigate the ductile behaviour of steel reinforcing bars lies in the absence of detailed studies about the effective behaviour of rebars under seismic action, that is reflected in the lack of codified standards and procedures for the production control of the seismic behaviour of steel bars. In this context in fact, the revision of European standard EN10080 and in particular, Mandate M115 aims at the individuation of common procedures for the harmonization of the standards about reinforcing and pre-stressed steels for concrete. A detailed investigation of the effective mechanical capacity under cyclic-seismic action was carried out on a set of steel reinforcing bars representative of the actual European production: in particular, a preliminary protocol for the execution of LCF tests was elaborated taking into account the information actually provided by scientific literature and standards. The ductile capacity of steel reinforcements so evaluated was then compared to the effective ductility demand required by real earthquake, leading finally to the elaboration of a proposal for the assessment of the LCF behaviour of steel bars during the production process. More in details, the demand in terms of strain and dissipated energy density on steel reinforcing bars was evaluated through an accurate numerical analysis of the structural behaviour of r.c. case studies designed according to actual standards for constructions (Eurocode 8, Italian Standard D.M. 14/01/2008). Moreover, since the current scientific literature (Apostolopoulos 2006, Apostolopoulos and Papadakis 2008) evidenced that, in presence of aggressive environmental conditions, TempCore steel reinforcing bars generally exhibit a progressive damaging and a rapid decrease of the mechanical properties (i.e. strain, strenght and dissipative capacity), the experimental test campaign on rebars was consequently repeated on corroded steel reinforcements. The effects of corrosion on rebars were opportunely reproduced through the execution of accelerated corrosion tests in salt spray chamber following a suitably defined protocol. The analysis of the ductile capacity of corroded steel reinforcing bars allowed the assessment of the ability of corroded bars to still sustain the ductile requirements due to real seismic events

Mechanical performance of steel reinforcing bars in uncorroded and corroded conditions

The paper presents data coming from a wide experimental test campaign executed on different typologies of steel reinforcing bars representative of the actual European production scenario. Tensile and low-cycle fatigue tests have been executed to assess the mechanical performance of reinforcing bars under monotonic and cyclic/seismic conditions. The effects of exposure to aggressive environmental conditions have been reproduced through accelerated salt-spray chamber. Residual mechanical performance of corroded specimens has been analyzed as function of corrosion indicators such as mass loss and necking

Numerical modelling, analysis and retrofit of the historical masonry building "La Sapienza" in Pisa

The evaluation of the structural safety and seismic vulnerability of historical masonry buildings represents one of the most important problems affecting countries, like Italy, characterized by a wide cultural heritage whose original configuration shall be preserved against unexpected seismic events or insufficient maintenance. Recent earthquakes in the Italian regions (Umbria-Marche 1997, Molise 2002, L'Aquila 2009 and Emilia-Romagna 2012) evidenced the high vulnerability of historical masonry buildings, severely damaged in both their structural and not-structural components (i.e. walls, vaults, domes, arches, ornaments and others) and the following significant economic effort required for the execution of retrofit interventions. According to the actual Italian Standard for Constructions (D.M. 14/01/2008) and to the Guidelines provided by the Italian Ministry for Infrastructures for the evaluation and reduction of seismic risk on historical heritage (2010), a multi-level approach is generally adopted for the assessment of the structural safety and seismic vulnerability of ancient masonry buildings and for the design of retrofit interventions. In the present work, the above mentioned multi-level approach is applied to "La Sapienza" Palace in Pisa (Italy). The building, ancient seat of the University of Pisa, was subjected to a wide in situ structural survey and to experimental testing campaigns (including geotechnical analyses, mechanical characterization of materials, structural monitoring and other) allowing the elaboration of a reliable FEM model used for the execution of structural verifications and for the individuation of the main retrofit techniques able to preserve its original nature providing, at the same time, a sufficient margin of structural safety

Evaluation of structural safety and seismic vulnerability of historical masonry buildings: studies and applications in the Tuscany Region

Recent earthquakes in Italian regions evidenced the high vulnerability of historical masonry existing buildings: severe damages were revealed in structural and not structural elements with the following loss of lives and of significative examples of the Italian architectural tradition, often requiring a strong financial effort to be carried back to their ancient brightness. The majority of the Italian buildings' heritage is made up of masonry constructions with high architectural, historical and monumental impact, enlarged over the centuries without an organized scheme and consequently characterized by structural and not structural problems often increased by the loss of an accurate maintenance. The Italian Standards for Constructions and the guidelines provided by the Ministry for Infrastructures for the evaluation and reduction of seismic risk on historical heritage pay a lot of attention towards the vulnerability analysis of existing buildings, necessary for the elaboration of a project providing higher level of structural static and seismic safety without deleting the original nature of the building. In the present work, the structural analyses of two historical masonry buildings, Palazzo La Sapienza in Pisa and Palazzo Ducale in Massa are presented

Progetto preliminare di riqualificazione a scopi turistico portuali dell'area di Pertusola (La Spezia)

Oggetto della presente tesi è la riqualificazione dell’area di Pertusola, situata nel comune di Lerici, che ospitava, fino all’inizio degli anni ’80, il complesso industriale delle fonderie omonime. Nella suddetta zona è prevista la realizzazione di un porticciolo turistico e dei servizi ad esso connessi quali strutture ricettive, per il commercio, complessi residenziali, edifici per attività cantieristiche navali e nautiche in generale. L’elaborazione del progetto preliminare si è fondata su uno studio approfondito del territorio, delle sue origini storiche e delle modificazioni subite dall’area e dai fabbricati in essa presenti nel corso del XX secolo. La progettazione è stata condotta seguendo le prescrizioni del Piano Urbanistico Comunale del comune di Lerici, che prevede tra l’altro il recupero di due tra i capannoni industriali delle vecchie fonderie, tuttora esistenti, quale testimonianza storica di un importante episodio dell’economia locale. Nell’ambito del progetto generale è stato inoltre analizzato nel dettaglio il recupero dell’edificio un tempo adibito alla laminazione dello zinco ed oggi parzialmente dimesso ed in stato di degrado. Per tale edificio, composto a sua volta da tre blocchi, è stata condotta la verifica di sicurezza ai sensi del D.M. 14/01/2008, ed è stata proposta una possibile soluzione di adeguamento funzionale e strutturale

Dataset on the cyclic experimental behavior of Steel frames with Reinforced Concrete infill Walls

This paper presents the experimental data on the cyclic behavior of Steel frames with Reinforced Concrete infill Walls (SRCW). Two specimens, characterized by a different shear studs distribution, have been tested: the first one is provided with shear studs positioned only in the four corners of the steel frame; the second one presents shear studs all distributed along the perimeter of the steel frame except for the zone of the dissipative fuses. The overall setup, loading protocol, collapse mechanisms, force-displacement curves for both the whole system and the main single components are described for the two tested prototypes

Investigation on the seismic response of a large monumental complex

Historical masonry structures are characterised by a high level of seismic vulnerability, as demonstrated by recent and past seismic events. Monumental buildings, in particular, represent a very challenging topic. Their morphological evolution, characterised by transformations, aggregations and modifications developed over the centuries, have given rise to very complex structures that should be considered as structural aggregates rather than single buildings. The present paper briefly summarises the assessment of the structural performance of the monumental complex of the Certosa di Calci (Italy), by applying an in-depth multi-level and multi-disciplinary approach. The morphological evolution of the aggregate was studied by means of critical historical analysis enabling the identification of the structural units composing it. The complex was, besides, subjected to in-situ survey campaigns allowing an adequate knowledge level. Reliable FEM models were elaborated, and non-linear static pushover analyses were performed. The single structural units were initially studied as isolated buildings and then combined evaluating the influence of the in-aggregate behaviour on the overall structural response. Pushover analyses were performed for each evolution configuration, allowing results in terms of capacity curves, load factors and damage distribution. The methodology presented, although used for a specific case study, can be extended to other constructions characterised by similar complexity and features.Postprint (published version

Design and analysis of automated rack supported warehouses

Background: The lack of codified standards for the design of automated rack supported warehouses forced engineers to use personal experience and commonly accepted rules. Objective: This paper investigates the efficacy of applying Eurocodes’ rules for the design and analysis of automated rack supported warehouses. Structural performance, construction feasibility and economic effort are considered. Method: A typical case study building was designed following the two approaches proposed by Eurocodes: elastic and dissipative. Results: The satisfaction of the capacity design requirements, used for dissipative approach, was not always possible. Analyses showed the development of non-uniform collapse mechanisms and yielding patterns. Conclusion: Specific design rules and analysis techniques shall be developed accounting for the structural performance of automated rack supported warehouses

Experimental tests on real-scale EBF structures with horizontal and vertical links

The paper presents data achieved during an experimental test campaign executed on real-scale one storey/one bay EBF steel structures with vertical and horizontal links. Experimental tests were executed in displacement control by applying cyclic loading histories following ECCS45 protocol and constant amplitude-imposed displacements. Data provide indications concerning the energy dissipated by each prototype during tests, the corresponding shear force - angular distortion curves of the dissipative link and, besides, the force-displacement behavior of the steel prototypes until failure

PALAZZO LA SAPIENZA IN PISA: STRUCTURAL ASSESSMENT AND RETROFIT OF AN HISTORICAL MASONRY BUILDING IN ITALY

Palazzo La Sapienza, historical seat of the University of Pisa since the XVI century, represents one of the most important examples of the Tuscany cultural heritage, nowadays not in use due to several problems related to maintenance and structural deficiencies. The building, in its current form, is the result of several modifications, enlargements, elevations, connection with adjacent parts, resulting finally more similar to a “structural aggregate” - made up of single units connected together without specific scheme and organization - than to a single unitary building. After the earthquake of May 2012, the Palace was temporarily closed in relation to the ordinance issued by the Major’s Office and then subjected to wide in situ investigations aiming at analyzing in a very detailed manner all the criticisms related to structural, nonstructural, geotechnical and maintenance problems; the deep in situ survey campaigns allowed to reach a very deep knowledge of the building, of its progressive morphological evolution and of its actual condition, including problems not directly related to the structural condition but, as an example, to the instability and heterogeneity of the ground soil and of the foundation system. All the information so obtained allowed the execution of static and seismic vulnerability assessment – according to the actual prescriptions of Italian Standard for Constructions (D.M. 14/01/2008) – through the elaboration of complex global and local models and the final elaboration of an executive retrofit design comprehensive of local interventions on significant structural elements or subportions of the building. In the present paper, after a short description of the knowledge analysis of the building and of its safety verification, the retrofit executed to obtain a satisfying level of safety is presented