Littérature scientifique sur le sujet « Reinforcement-masonry interface »

Development of pseudo interface element for modelling of reinforced brick masonryABSTRACTStrength of reinforced masonry is influenced by interfaces between brick, mortar and reinforcement. Experimental protocol has been defined to characterise the behaviour of reinforced brick masonry joint, with reinforcement steel embedded in cement mortar 1:6. This is applicable for low-strength, low-stiffness brick masonry found. Experimental investigations show that bond between masonry and steel is not perfect. Considering critical bond mechanisms, an attempt is made to put-forth a novel approach for development of a pseudo interface element representing three different materials (viz. brick, mortar and reinforcement) and two interfaces (reinforcement-mortar (RM) interface and brick-mortar (BM) interface). Principles of classical Reinforced Concrete (RC) design can therefore be directly applied to reinforced masonry with the introduction of the proposed pseudo interface element.Keywords: reinforced masonry joint; interface element; masonry reinforcement bond behavior; pseudo interface material; stiffness of interface elements. Desarrollo de un pseudo-elemento de interfaz para el modelado de mampostería de ladrillo reforzado RESUMENLa resistencia de la mampostería reforzada está influenciada por las interfaces entre el ladrillo, el mortero y el refuerzo. Se ha definido un protocolo experimental para caracterizar el comportamiento de la junta de mampostería de ladrillo reforzado, con acero de refuerzo incrustado en mortero de cemento 1: 6. Esto es aplicable para la albañilería con ladrillos de baja resistencia y baja rigidez encontrada. Las investigaciones experimentales demuestran que el vínculo entre la mampostería y el acero no es perfecto. Teniendo en cuenta los mecanismos de enlace críticos, se intenta presentar un nuevo enfoque para el desarrollo de un elemento de pseudo-interfaz que represente tres materiales diferentes (ladrillo, mortero y refuerzo) y dos interfaces (de refuerzo y mortero (RM) y de mortero (BM)). Por lo tanto, los principios del diseño de concreto armado (RC) clásico pueden aplicarse directamente a la mampostería reforzada con la introducción del pseudo-elemento de interfaz propuesto.Palabras clave: articulación de mampostería reforzada; elemento de interfaz; comportamiento de enlace de refuerzo de mampostería; pseudo-material de interfaz; rigidez de los elementos de la interfaz. Desenvolvimento de um elemento pseudo-interface para modelagem reforçada alvenaria de tijoloRESUMOA resistência de alvenaria reforçada é influenciada pelas interfaces entre o tijolo, argamassa e de reforço. Definido um protocolo experimental para caracterizar o comportamento da placa reforçada alvenaria de tijolo com aço de reforço embebido em argamassa de cimento 1: 6. Isso se aplica a alvenaria de tijolo com baixa resistência e baixa rigidez encontrados. A pesquisa experimental mostra que a ligação entre a alvenaria e aço não é perfeito. Dada a mecanismos de ligação crítica, tenta apresentar uma nova abordagem para o desenvolvimento de um elemento de pseudo-relação representando três diferentes materiais (tijolos, argamassa e reforço) e duas interfaces (reforço e argamassa (RM) e argamassa (BM)). Portanto, os princípios de concepção de betão armado (RC) pode ser aplicado directamente sobre a alvenaria reforçada clássico com a introdução do elemento pseudo-interface proposta.Palavras-chave: alvenaria armada conjunta; elemento de interface; vinculativo de reforço comportamento da alvenaria; material de pseudo-relação; rigidez dos elementos de interface.

The mechanical properties of masonry structural members strengthened by FRP (Fiber Reinforced Polymer) are affected by the bond strength of the reinforcement interface, in addition to the strength of the material FRP itself. This project is aimed at the new technology of Sprayed Fiber Reinforced Polymer Composites (SFRP), which is currently attracting attention. The bond strength between SFRP layer and masonry surface under high-humidity condition during strengthening construction and dry-wet cycle conditions after reinforcement were studied by experimental method. Different masonry substrates and different reinforcement methods were set as the test parameters. It is concluded that, compared with the currently used GFRP (Glass Fiber Reinforced Polymer) sheets reinforcement method, the SFRP reinforcement method has an significant improvement in the bond strength and the durability.

The need to guarantee higher safety levels of masonry structures under both short and long term conditions, have led to the use of new materials and technologies, in conjunction or in place of traditional ones. In this context, fiber-reinforced composite materials have gained an increasing success, mostly for strengthening, retrofitting and repair existing structures. As well known, the analysis of the interface performance of FRP (Fiber Reinforced Polymer) composites and masonry substrate is a critical problem as it influences the effectiveness of the technique. The present paper reports part of a large research project, still in progress, focused on the analysis of the bond performance between FRP sheet and different type of masonry substrates. The obtained experimental data were analysed in terms of bond strength and the kind of failure. The influence of the deformability of the strengthening material as well as the mechanical performance of the substrates are also discussed.

Autoclaved aerated concrete (AAC) masonry is widely used in civil construction but requires further investigation. Hence, this experimental study evaluated three types of interface treatment between the reinforced concrete structure and AAC masonry, in scale, after a uniaxial compression resistance test. The types of interface treatment considered are reinforcement with steel bars, with rough polymeric cementitious mortar, and without treatment. The maximum load capacity, displacements, and occurrence of cracks were analysed. The results showed that the maximum individual load capacity did not significantly differ among the examined groups. However, the analysis of the displacements and cracks showed that the group with steel reinforcement had the smallest displacements and largest cracks. This behaviour is owing to the greater solidarity of forces conferred by steel reinforcement.

We report on experimental and numerical investigations of textile reinforced mortar (TRM) strengthening systems, an innovative solution for reinforcing historical masonry structures. The experimental campaign presented in this paper is original and concerns two commercial TRM applications to single-leaf clay masonry panels. The proposed FE modelling is based on a multiscale approach with the possibility of simulating bed joints sliding and TRM-reinforcement debonding. This last phenomenon is frequently reported in the experimental literature and it has been observed also in our experimental tests. The numerical model is applied to study the behaviour of TRM reinforced masonry panels under diagonal compression tests.

The use of composites with cement matrix seems to acquire an increasing interest in applications to masonry structures, due to their low impact, and a deeper understanding of the mechanical interaction between support and reinforcement is certainly necessary. The effectiveness of these interventions strongly depends on the bond between strengthening material and masonry, on the fibers/matrix interface, as well as on the mechanical properties of the masonry substrate [1]. In this work the attention was focused on the possible improvement of the bond between FRCM and masonry by means of an inorganic primer, which can be spread on the ceramic support before the application of FRCM reinforcement. Two different kinds of brick were tested, in order to simulate more or less porous masonry supports. Results obtained showed that, independently on the kind of brick used (more or less porous) the presence of an inorganic primer always improves bond between masonry support and the cementitiuos matrix of FRCM. In fact, the cementitous matrix of FRCM has been studied and optimized in order to guarantee the best fibers/matrix interface, while it is not necessarily the best option for improving the adhesion with the masonry support. In particular, very effective seems to be the use of very fine inorganic particles (at nanometric scale), which proved to be able to assure the best results in terms of bond strength. Also the fresh consistence of the primer seemed to influence the final result.

ABSTRACT This work aims to study the behavior of the block/grout interface for concrete and clay block masonry. This was achieved by push-out and pull-out experimental tests including reinforcement bar in the latter one. The experimental result showed that there is a good bond between the concrete blocks internal faces and the grout, enough to prevent infill-slippage, and that the whole tensile strength of the usual reinforcement bars is achieved provided they are properly anchored. Nevertheless, for clay blocks there is a low bond between the clay blocks internal faces and the grout, allowing the infill-slippage before the reinforcement bars reach their yield stress.

An innovative approach is proposed to define the optimal fiber-reinforcement of in-plane loaded masonry walls, modeled as linear elastic no-tension (NT) bodies. A topology optimization formulation is presented, which aims at distributing a prescribed amount of reinforcement over the wall, so as to minimize the overall elastic energy of the strengthened element. Perfect bonding is assumed at the wall-reinforcement interface. To account for the negligible tensile strength of brickwork, the material is replaced by an equivalent orthotropic material with negligible stiffness along the direction (s) undergoing tensile principal stress (es). Compressive principal stresses in the reinforcement are not allowed. A single constrained optimization problem allows both the equilibrium of the NT body to be enforced, and the optimal reinforcing layout to be spotted out, without any demanding incremental approach. Some preliminary numerical examples are shown to assess the capabilities of the proposed procedure and to identify the optimal reinforcement patterns for common types of masonry walls with openings.

Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90° and 45° relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.

There is an emerging need to upgrade historic masonry buildings and infrastructures which are most vulnerable to earthquakes. An objective of a long-term research program at Perugia University, Italy was developing design criteria for masonry reinforcement using a new class of materials, using Composite Reinforced Mortars (CRM). These are typically made of fiberglass meshes embedded into a cementitious or lime mortar, which offers higher sustainability features, in terms of vapour permeability and compatibility with masonry, lower costs, and better performance at high temperatures, compared to more traditional steel rebar jacketing or epoxy-bonded composites. These design criteria have been based on a comprehensive experimental and numerical research plan that included a study of the influence of reinforcing material, coating and wall thickness, and associated masonry strength and elastic properties, and the interaction of different stress states on bond behavior at interface masonry-to-coating. A design equation suitable for ultimate load design has been developed. Finally, analytical models regarding the lateral capacity of shear walls are briefly discussed.

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.

<p>The majority of existing Unreinforced Masonry (URM) structures are prone to weathering and catastrophic events such as earthquakes. The repair and strengthening of unreinforced masonry is a challenging task mainly due to the poor connection between the new materials and the existing substrate. The applications of Fibre Reinforced Polymers (FRP) for the strengthening of URM show that premature de-bonding and failure of the strengthened elements may occur.</p><p>In the current study, the application of Ultra High Performance Fibre Reinforcement Concrete (UHPFRC) layers for the improvement of the structural performance of URM specimens made of engineering bricks has been examined. Different percentages of steel fibres have been used and layers have been cast in connection with the URM specimens. Additional provisions for the improvement of the connection between the UHPFRC and the bricks have also been examined. The effect of the thickness of the layers and the effect of the fibre percentage of the UHPFRC have been investigated via flexural out of plane tests. The load mid- span deflection results have been recorded alongside with the slip at the UHPFRC-to-bricks interface and the results show that the structural performance of the URM specimens can be significantly improved with the proposed technique.</p>