1,721,138 research outputs found
NTC2018: la nuova Norma Tecnica e le costruzioni in Cemento Armato
No full textLa parte delle Norme Tecniche riguardante il cemento armato dovrebbe essere oramai consolidata. In pratica ci sono invece ancora alcune novità significative.
La prima riguarda l’esplicita considerazione, per la prima volta, degli effetti del confinamento degli elementi.
Vengono, infatti, introdotte formulazioni specifiche per valutare gli effetti in termini di deformazioni ultime del calcestruzzo per tener consto delle staffe negli elementi di sezione rettangolare e circolare. Sarà così possibile valutare la duttilità degli elementi esplicitamente, aspetto determinante per quantizzare l’incremento della capacità specie per elementi presso-inflessi come i pilastri: era l’ultimo tassello che mancava al progettista per fare un calcolo completo non lineare; ed adesso l’allineamento con l’Eurocodice 8 è totale.
Un altro aspetto che indirettamente influenzerà in maniera significativa le valutazioni strutturali, in particolare in zona sismica, è l’introduzione di elementi di partizione “duttili”, per i quali il limite per gli spostamenti di piano passa da 0.5% a 0.75% dell’altezza di interpiano
Towards Earthquake Risk Reduction Solutions: Applications of Composite Materials and Future Challenges
No full textThe development of fast, sustainable, and integrated strengthening interventions with direct benefits in terms of earthquake risk reduction is a challenging task. It is nowadays crucial to develop performance-based solution to increase the capacity of existing structures, commonly affected by significant deterioration and designed without modern seismic design provisions. The use of composite materials and innovative solutions has experienced a continuous increase in the last decade in the Mediterranean area both for structural members upgrading and retrofit applications. Composite materials solutions with a low level of disruption and low impact represents the future for the retrofit of existing structures. They represent the most suitable option for local strengthening interventions on structural and nonstructural components of reinforced concrete (RC) existing structures exploiting the advantage of negligible modification in mass and lateral stiffness with the capability to meet requirements of fast, low impact and cost-effective interventions.
The paper presents different solutions based on the use of composite materials to prevent the most common brittle and premature failure modes in case of seismic actions. The innovative solutions layouts and design procedures as well as the experimental programs carried out by the research group of the Department of Structures for Engineering and Architecture of University of Naples Federico II on members or full-scale structures to validate their effectiveness are herein presented and briefly discussed. The experimental results show the high potential of composite materials in recovering and enhancing the capacity of RC members and reduce the damage to infills; they are applicable with a low impact or entirely from the exterior of the building and in combination with energy efficiency interventions
FRP-to-Concrete interface relationships under monotonic and cyclic actions
No full textExternal bonding of fibre reinforced polymer (FRP) composites has become a popular technique used worldwide for strengthening existing reinforced concrete (RC) structures.
Interaction phenomena having place at the FRP-to-concrete interface deeply affect the overall behaviour of RC beams externally strengthened by FRP. Consequently, several proposals
have been carried out for describing the relationship between FRP-to-concrete relative displacements and interface shear stress. The present paper is mainly devoted to comparing the effectiveness of different identification methods for shear-stress-relative-slips law throughout the FRP-to-concrete interface. Several experimental results (pull-out tests under monotonic and cyclic actions), both available in the scientific literature and carried out directly by the authors, are utilised with this aim. The first cyclic delamination tests, carried out by the authors, allow a preliminary investigation on the influence of cyclic external actions on the bond of FRP reinforcement to the concrete substrate
Effectiveness of design formulations for injected anchors in masonry elements
No full textThe paper is aimed to carry out a critical analysis of the available experimental results of pull-out tests related to several types of injected anchors in masonry elements. The database is also comprehensive of the results of some experimental pull-out tests directly carried out by the Authors. Both data on traditional steel bars and on anchors made by innovative materials embedded in several types of masonry made of natural stones and clay bricks are included in the database. Firstly, the main parameters influencing the experimental pull-out forces in the collected database were analyzed. Successively, the experimental values of the pull-out forces were compared with theoretical predictions provided by existing formulations and their reliability was discussed. Finally, regression analyses were carried out on the available database in order to assess new design formulations taking into account the main parameters influencing the performance of injected anchors
Census-based typological usability fragility curves for Italian unreinforced masonry buildings
Full text linkThe main vulnerability models available in the literature aim to develop damage fragility curves to estimate the damage level suffered by a building after a seismic event. However, recent earthquakes have highlighted the great importance of predicting the usability of residential buildings, i.e. the condition of a building being habitable or occupiable after a seismic event. The building usability performance can be used as an indicator for allocating economic funding after a seismic event because recent researches have demonstrated a stronger correlation between repair costs and usability assessment rather than between repair costs and structural damage. Therefore, this work focused on the development of census-based fragility curves for the preventive forecast of the usability of Italian unreinforced-masonry buildings. The proposed usability model was calibrated based on the 2009 L'Aquila earthquake database, including almost 60,000 unreinforced-masonry buildings, and this database was increased by adding data from the Italian census to account for uninspected constructions. Six typological classes were defined considering two parameters available both in the post-earthquake and Italian census databases: construction timespan and state of repair. Additionally, it was highlighted in which cases the number of stories was also relevant. The usability fragility curves were defined as a function of peak ground acceleration for two building usability states: partially unusable and unusable. The results confirmed that older buildings are more vulnerable and clearly pointed out the crucial role of the state of repair as a parameter influencing the building usability
Effectiveness of traditional strengthening measures on historic buildings: the seismic performance of Palazzo Comunale and Borgia fortress in Camerino after 2016-17 seisimic sequence
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