Academic literature on the topic 'Masonry FRP strengthening arches and vaults'

The studies contained in the current literature particularly emphasize the importance of the role of the local bond mechanism on the global performance of fiber reinforced polymer systems (FRPs) employed for the strengthening and the rehabilitation of structures. Nevertheless, although several applications of FRPs involve curved masonry structures (arches, vaults, domes, etc.), the bond mechanism of FRPs applied on masonry samples with curved substrates is a topic still scarcely investigated and the actual guidelines do not provide specific design formulas. The aim of the present paper is to analyze the main features characterizing the bond behavior of FRPs externally applied to masonry specimens with a curved substrate configuration throughout a simple modeling approach based on the interface concept. Particular consideration is devoted to the development of suitable constitutive laws for the FRP/masonry interface. Considering case studies derived from the current literature, consisting of shear-lap bond tests of curved masonry specimens characterized by different curvatures of the bonded surface and different strengthening configurations, numerical analyses are carried out in order to emphasize the ability of the model to capture the bond behavior of FRP applied on curved masonry substrates.

Existing masonry and reinforced concrete structures are characterized by a wide use of structural and non-structural masonry members such as structural walls, infill walls, arches, vaults etc. All these members are characterized by high vulnerability when subjected to seismic events, since unreinforced masonry has a negligible tensile strength. The use of fiber reinforced polymers (FRP) composites has become a common practice and it represents a light-weight, easy, fast, and non-invasive solution for rehabilitation of existing masonry structures. Fabric reinforced cementitious matrix (FRCM) are relatively newly developed composite materials, representing a valid alternative to FRP in strengthening and retrofitting of existing reinforced concrete and masonry structures. Despite of the numerous advantages guaranteed by the inorganic matrix, the bond-behavior between the fibers and the embedding matrix is still under investigation. Different set-ups have been proposed in the literature to study the bond behavior of FRCM composites. Among them, single-and double-lap shear tests are the most commonly used. In this paper, the bond behavior of a polyparaphenylene benzobisoxazole (PBO) FRCM composite applied to masonry elements is studied using a bending and a single-lap shear test set-up. The bond capacities obtained by the two set-ups are analyzed and discussed.

Masonry buildings are prone to brittle collapses under seismic forces due to their fragility and low capacity to resist against cyclic actions. In most cases failures occur in forms of rigid collapses due to loss of equilibrium of entire structural parts, and this is due to low quality of structural detailing or horizontal forces due to vaults and arches that increase their intensity during earthquakes.The entire architectural heritage is represented by masonry construction, also in seismic areas, thus a mandatory issue consists of preserving the historical value against natural events such as earthquakes. In the last years new materials were employed as strengthening systems for structural purposes, and composite materials are those that have found a large field of application in this context. New structural solutions for seismic strengthening and retrofit are presented in the paper, with reference to real applications in which composite materials demonstrated to be effective solutions.The applications will be presented with reference to two historical masonry buildings, having different construction schemes; in which pre tensioned FRP wires were designed and applied as ties. The use of FRP wires for the first building was studied with reference to the existing cracking problems, which were investigated by means of non-destructive techniques, visual inspections and local destructive tests. The second case reports a study of seismic vulnerability for a large building used as theatre, in which a global analysis was accompanied by kinematic analyses that were run under linear and non- linear approaches. The results of the analyses allowed understanding the possible failure mechanisms that needed to be inhibited by an effective structural strengthening system. Also in this case the use of FRP pre-tensioned wires, about 40 m long, demonstrate to be the most effective structural device in terms of costs and speed of application.The seismic analyses (global and local) will be illustrated and discussed in the paper, with reference to the experimental tests that were necessary for the characterization of the material properties. The results will show how the presence of the FRP system is able to prevent possible collapses of the high walls that are present in the building.

Recent seismic events prompted research to develop innovative materials for strengthening and repair of both modern and historic masonry constructions (buildings, bridges, towers) and structural components (walls, arches and vaults, pillars, and columns). Strengthening solutions based on composite materials, such as the Fiber Reinforced Polymers (FRP) or the Fiber Reinforced Cementitious Matrix (FRCM), have been increasingly considered in the last two decades. Despite reinforcement made of short-fibers being a topic that has been studied for several years from different researchers, it is not yet fully considered for the restoration of the masonry construction. This work aims to experimentally investigate the enhancement of the mechanical properties of lime-based mortar reinforced by introducing short glass fibers in the mortar matrix with several contents and aspect ratios. Beams with dimensions of 160 mm × 40 mm × 40 mm with a central notch were tested in three-point bending configuration aiming to evaluate both the flexural strength and energy fracture of the composite material. Then, the end pieces of the broken beams were tested in Brazilian and compressive tests. All the tests were performed by a hydraulic displacement-controlled testing machine. Results highlight that the new composite material ensures excellent ductility capacity and it can be considered a promising alternative to the classic fiber-reinforcing systems.

The innovative technique here illustrated is the result of historical evolution of an ancient system of reinforcing tiled vaults belonging to the constructive Spanish tradition. Such a traditional technique consists in the lamination of flat rectangular tiles or thin bricks into thin vaults known as boveda tabicada. Since the use of modern technologies may improve the mechanical performance of the traditional materials, the core of the proposed strengthening system is based on the idea of combining the peculiar features of tabicada technique with the good tensile properties of composite materials. More in detail, it is possible to obtain reinforced masonry vaults or arches by overlapping different layers of tiles or thin bricks and laminates, embedded within an hydraulic mortar, so that the entire assembly may act as a single structural unit. Eighteen prototypes of tiled arches were tested under a monotonic vertical load applied at the keystone. The influence of the types of reinforcement, number of layers and properties of hydraulic mortar has been investigated. Laboratory outcomes are presented and discussed in the paper considering mechanical behavior of specimens and axial stress-axial strain relationships.

This paper examines the structural behavior of masonry arches strengthened at the intrados with fabric reinforced cementitions matrix (FRCM) composites. Textiles made of poliparafenilenbenzobisoxazole (PBO) and carbon fibers are considered. The experimental results are compared with those obtained on un-strengthened arches and arches strengthened with a carbon fiber reinforced polymer (C-FRP) composite. The tested arches are analyzed with the approach of the limit analysis of the collapse mechanisms.

Among masonry buildings characterized by a complex architecture, a significant portion is represented by heritage buildings. A significant seismic vulnerability is due to the presence of thrusting elements like as arches and vaults. Their ultimate capacity can be improved by means of several strengthening techniques. However the advantages of using Textile Reinforced Mortars (TRM) are well highlighted in the scientific literature.The present work focuses on ultimate behaviour of masonry barrel vaults, in the framework of incremental analysis, including the strengthening effect. The analytical model is compared in terms of ultimate capacity and failure mode with a full scale masonry barrel vault dynamically tested. After the first tests, the vault has been strengthened with Textile Reinforced Mortar (TRM) and tested again.

Cross vaults can be easily destabilised when their thrusts are not sufficiently contained by the stiffness of their lateral walls or systems of buttresses. A quarter-scale model from the aisles of Holyrood Abbey church in Edinburgh, which collapsed in 1768 due to excessive load from diaphragm walls that substituted the original roof trusses, demonstrated earlier the pattern of cracks that leads to failure under horizontal spread of supports. A recent model of this vault aimed to study the effects of applying Aramid fibre reinforcement against such failure exactly at the critical cracks, compared to other tests that studied arches or vaults under point load, reinforced continuously. The paper presents how the quality of certain areas of the fabric diverted failure from the longitudinal vertex merging with the detachment of the ribs, as originally observed. Moreover, the repair allowed the vault to resist 50% more spread of its supports, and failure occurred ultimately when new cracks formed in parallel to the repaired ones. The tests and repairs validate qualitative observations on crack patterns and failure of real cases and highlight the benefits and limitations when specific repairs are made instead of wholesome application of a reinforcing mesh at the extrados of vaults.

Given that a significant fraction of buildings and architectural heritage in Europe’s historical centers are masonry structures, the selection of proper diagnosis, technological surveys, non-destructive testing, and interpretations of crack and decay patterns is paramount for a risk assessment of possible damage. Identifying the possible crack patterns, discontinuities, and associated brittle failure mechanisms within unreinforced masonry under seismic and gravity actions allows for reliable retrofitting interventions. Traditional and modern materials and strengthening techniques create a wide range of compatible, removable, and sustainable conservation strategies. Steel/timber tie-rods are mainly used to support the horizontal thrust of arches, vaults, and roofs and are particularly suitable for better connecting structural elements, e.g., masonry walls and floors. Composite reinforcing systems using carbon, glass fibers, and thin mortar layers can improve tensile resistance, ultimate strength, and displacement capacity to avoid brittle shear failures. This study overviews masonry structural diagnostics and compares traditional and advanced strengthening techniques of masonry walls, arches, vaults, and columns. Several research results in automatic surface crack detection for unreinforced masonry (URM) walls are presented considering crack detection based on machine learning and deep learning algorithms. In addition, the kinematic and static principles of Limit Analysis within the rigid no-tension model framework are presented. The manuscript sets a practical perspective, providing an inclusive list of papers describing the essential latest research in this field; thus, this paper is useful for researchers and practitioners in masonry structures.

In the last two decades, FRP (Fibre-Reinforced Polymers) composite materials have been adopted for strengthening and repair of both modern and historic masonry constructions (buildings, bridges, towers) and structural components (walls, arches and vaults, piers and columns). Strengthening of masonry brick arches and vaults with FRP laminates can contribute significantly in the improvement of their structural capacity at a limit state, by activating local mechanisms both at material and interface levels, but also modifies the collapse mechanisms of the original structures, as the reinforcement prevents the typical brittle failure due to the formation of hinge-mechanisms. Despite the increasing number of specific studies on FRP reinforcement of masonry structures, investigations are still limited if compared to reinforced concrete applications. Moreover, few codes and recommendations are currently available. Starting from these points, the present work deals with experimental investigations on three local mechanisms involved by the collapse of FRP-reinforced masonry arches: the interface behaviour in the case of stresses normal to the surface (FRP detachment observed in structures with intrados reinforcement) has been investigated through the execution of a large number of combined tests on solid clay bricks (flexural, compressive, splitting and pull-off tests) aimed at experimentally calibrate possible correlations among the corresponding strength parameters and to observed possible influences of the fibres type and the presence of primer on the pull-off behaviour; the bond behaviour has been investigated by performing ten Double-lap Shear Tests on solid clay bricks, aimed at calibrating fracture energy value and bond-slip law for both carbon FRP and glass FRP reinforcement (moreover, a simple exponential-based bond-slip law has been proposed); the mixed-mode behaviour (fourteen tested samples) has been investigated by adapting a test setup developed for FRP applications on reinforced concrete, known as V-shape Peel Test, to clay substrate, in order to reproduce on a local scale the conditions related to the shear sliding failure of arches with extrados reinforcement. Finally, several case studies, concerning real-scale or scaled brick masonry arches and vaults reinforced at their intrados or extrados, have been collected from literature in order to compare the experimental results to the available interpretative models of the global behaviour of the structure at failure.<br>Negli ultimi due decenni, i materiali compositi FRP (Fibre-Reinforced Polymers) sono stati adottati anche nel rinforzo di costruzioni murarie sia moderne sia antiche (edifici, ponti, torri), nonché di vari elementi strutturali (pareti, archi e volte, pile e colonne). Il rinforzo di archi e volte in muratura con FRP può contribuire in modo significativo a migliorare la loro portanza in stato limite, attivando meccanismi locali a livello di materiali e interfaccia, ma comporta anche un cambiamento dei meccanismi di collasso della struttura originale, dal momento che il rinforzo impedisce la tipica rottura fragile causata dalla formazione di meccanismi a cerniera. Nonostante un crescente numero di studi riguardanti il rinforzo di strutture murarie con FRP, le indagini sono tuttavia ancora limitate, se confrontate con applicazioni su calcestruzzo armato. Inoltre, pochi codici e raccomandazioni sono attualmente disponibili. Partendo da questi punti, il presente lavoro affronta l'indagine sperimentale di tre meccanismi locali coinvolti nel collasso di archi rinforzati con FRP: il comportamento dell’interfaccia nel caso di tensioni normali alla superficie (distacco del composito osservato in strutture rinforzate all’intradosso) è stato investigato mediante l’esecuzione di un ampio numero di prove combinate eseguite su mattoni pieni in laterizio (prove a flessione, compressione, trazione indiretta e pull-off), allo scopo di calibrare sperimentalmente eventuali correlazioni fra i relativi parametri di resistenza e di osservare eventuali influenze del tipo di fibra e della presenza del primer sul comportamento nella prova di pull-off; il comportamento nel caso di azioni tangenziali è stato studiato mediante l’esecuzione di dieci Double-lap Shear Tests su mattoni pieni in laterizio, al fine di calibrare energia di frattura e legge bond-slip per rinforzo in fibra di carbonio e fibra di vetro (inoltre, è stata proposta una semplice legge bond-slip); il comportamento nel caso di azioni miste (quattordici prove eseguite) è stato investigato mediante l’adattamento di una prova sviluppata per applicazioni di FRP su calcestruzzo armato, nota come V-shape Peel Test, a mattoni in laterizio usati come substrato, allo scopo di riprodurre a scala locale le condizioni relative allo scorrimento a taglio sul giunto di archi con rinforzo estradossale. Infine, vari casi studio, riguardanti archi e volte in muratura, a dimensioni reali oppure scalate, sono stati raccolti da letteratura al fine di comparare i risultati sperimentali con i modelli interpretativi del comportamento globale della struttura a collasso attualmente disponibili.

Da alcune decine di anni i materiali compositi fibrorinforzati vengono diffusamente utilizzati nel campo dell’Ingegneria civile, sia per quanto riguarda la realizzazione delle strutture di nuove costruzioni, sia per quanto riguarda il consolidamento statico degli edifici esistenti o di parte di essi. Fino ad allora, tali materiali, innovativi sotto ogni punto di vista, a causa del loro elevato costo, erano riservati ad applicazioni relative all’Ingegneria aeronautica e spaziale, per le quali in effetti furono concepiti, all’automobilismo da competizione, alla nautica e al settore dei trasporti in genere. Successivamente, con la messa a punto di processi di produzione più economici della fibra di carbonio, la più diffusa sicuramente, come la laminazione e la pultrusione, gli FRP sono stati esportati anche ad altri campi applicativi, grazie ad una serie di vantaggi che essi offrono: la leggerezza, l’elevata resistenza, la buona rigidità, la economicità dovuta alla facilità di trasporto e montaggio, la bassa invasività, la rapidità del collocamento in opera e la reversibilità dell’intervento. Il settore edilizio vanta un rapido sviluppo applicativo di queste nuove tecnologie, e gli interventi finora realizzati dimostrano l’indubbia efficacia e riuscita delle operazioni; nello stesso tempo, però, le metodologie di calcolo non sono del tutto definite e testate e, cosa forse ancora più importante, non sono ancora state raccolte in adeguati corpi normativi. Inoltre, essendo materiali di nuova generazione, è incerto il loro comportamento nel tempo. Per questo i progettisti preferiscono ancora contare su materiali con proprietà decisamente note e costanti, piuttosto che su altri dotati di proprietà più elevate ma ancora poco conosciuti. Si assiste dunque ad una dicotomia tra la pratica applicativa, da una parte, ed i settori matematico-scientifico e normativo dall’altra. Si lavora e si utilizzano queste nuove tecnologie di indubbia efficienza, senza però avere un riscontro numerico né un supporto scientifico, e neppure un apparato normativo a tutela dei tecnici che ne fanno uso. Il presente lavoro, dunque, partendo dalla consultazione e dalle lettura critica di articoli tratti dalla letteratura tecnico-scientifica e dal Documento Tecnico del CNR DT200/2004, unico riferimento, almeno sul panorama italiano, ‘quasi’ normativo (o più correttamente insieme di raccomandazioni), vuole proporre e validare dei modelli numerici di calcolo per l’analisi di strutture voltate in muratura fibro-rinforzate.

Existing un-reinforced masonry buildings made of vaults, columns and brick and multi-leaf stone masonry walls, many of which have historical and cultural importance, constitute a significant portion of construction heritage in Europe and rest of the world. Recent earthquakes in southern Europe have shown the vulnerability of un-reinforced masonry constructions due to masonry almost total lack of tensile resistance. Composite materials offer promising retrofitting possibilities for masonry buildings and present several well-known advantages over existing conventional techniques. The aim of this work is to analyze the effectiveness of seismic-upgrading methods both on un-damaged (preventive reinforcement) and damaged (repair) masonry building. After a brief description of mechanical and physical properties of composite materials, three different applications have been addressed: in-plane reinforcement of masonry walls, extrados and intrados reinforcement of masonry vaults/arches and masonry column confinement with composite materials.

Existing un-reinforced masonry buildings made of vaults, columns and brick and multi-leaf stone masonry walls, many of which have historical and cultural importance, constitute a significant portion of construction heritage in Europe and rest of the world. Recent earthquakes in southern Europe have shown the vulnerability of un-reinforced masonry constructions due to masonry almost total lack of tensile resistance. Composite materials offer promising retrofitting possibilities for masonry buildings and present several well-known advantages over existing conventional techniques. The aim of this work is to analyze the effectiveness of seismic-upgrading methods both on un-damaged (preventive reinforcement) and damaged (repair) masonry building. After a brief description of mechanical and physical properties of composite materials, three different applications have been addressed: in-plane reinforcement of masonry walls, extrados and intrados reinforcement of masonry vaults/arches and masonry column confinement with composite materials.