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Different commercial Finite Element Codes proved to be able to describe the mechanical behavior of masonry materials externally reinforced by means of Carbon Fiber Reinforced Polymers (CFRP); the behavior of fracturing materials, characterized by low tensile strength, with adhered strips can be reproduced relying on parameters based on fracture mechanics and the theories of adhesion.In this report the comparison is made of previous experimental test results with numerical analysis, carried out on masonry panels reinforced with CFRP strips and subjected to out of plane actions. The comparison is especially addressed to the evaluation of the post peak branch; in addition to the slopes of the diagram in the pre-critic phase, available kinematic ductility and energy shares both prior and after the peak load were considered in order to interpret the capability of the micro-mechanical model implemented in the FEM Code to account for the local phenomena influencing the interaction between masonry and FRP strengthening systems.

The conservation and the preservation of existing masonry buildings, most of them recognized as cultural heritage, require retrofitting techniques that should reduce the invasiveness and assure reversibility and compatibility with the substrate. In this perspective, the strengthening system should be able to improve the bearing capacity of the structural member and, at the same time, to assure mechanical and material compatibility. The use of Fabric Reinforced Cementitious Matrix (FRCM) composites is now recognized to be suitable for these purposes. Indeed, the inorganic matrix has comparable properties with respect to the existing historical mortars while the fabric has relevant tensile strength. At the same time, these systems assure satisfactory level of reversibility (or at least removability). In this scenario, the present research aims to investigate the FRCM-confinement of masonry columns focusing on the influence of specific parameters, still poorly investigated, in order to deeply understand their effect on the mechanical response. In particular, the experimental variables are: the type of masonry substrate (Tuff and clay brick with lime-based mortar), the type of FRCM system (glass dry mesh + lime-based mortar and steel mesh + lime-based mortar) and the number of plies (1, 2 and 3). In addition, a detailed experimental characterization of the utilized materials has been carried out, including bond tests between the reinforcement and the substrate. The results evidenced that the FRCM is an effective solution for masonry columns confinement once a proper design is performed, taking into account all involved parameters. The different strengthening systems exhibited different failure modes. Generally, a single ply of external reinforcement produced a negligible increase of bearing capacity. Both strengthening systems applied with multi-ply strengthening schemes produced a significant increase in terms of strength and ultimate axial deformation. This benefit was observed for both Tuff and clay masonry columns. Two available design-oriented formulas, reported in the Italian CNR (National Research Council) and ACI (American Concrete Institute) guidelines have been utilized, in order to further investigate their accuracy, mostly in the case of multi-layered reinforcement. The performed comparisons highlight that the two design relationships provide similar and accurate results when referred to the GFRCM (Glass-FRCM) system in 1- and 2-layer configurations, while the predictions appear conservative when 3 layers of GFRCM are utilized, for both masonry types. Considering the SRG (Steel Reinforced Grout) system, the results predicted by the two models are more scattered, mostly when the number of layers increases. In addition, the formulation proposed by CNR appears more accurate in the case of Tuff masonry while the ACI predictions are closer to the experimental results in the case of clay brick masonry.

The preservation and enhancement of traditional earthen masonry structures as well as the practice of new construction with raw earth material is nowadays matter of investigation. At this stage of research, experimental analysis needs to be supported by numerical analysis to corroborate and interpret results and, successively, to extend the analysis to more complex load conditions, tune design methods and define quick verification formulas for simple structures. For this reason, constitutive models provided by engineering simulation software for mechanical analysis, to describe low tensile strength materials, have been used to reproduce mechanical tests and have been compared. The arch was selected as the best case study to test the response of constitutive models suitable for a low tensile strength material and, in a successive stage of research, the efficiency and the modelling of reinforcement techniques.

The use of composite materials, in particular Carbon Fibre Composite Materials (CFRP), as reinforcement of both concrete and masonry structures is more and more widespread in the structural rehabilitation and retrofitting of existing buildings, thanks to their excellent mechanical performance combined with lightness and simplicity of application. Since the bond capacity of CFRP-to-masonry bonded joints, with respect to in-plane loads, is generally lower than the composite tensile strength, several methods have been proposed in the literature to increase their structural performance. Among these, CFRP spike anchors showed to be able to effectively increase strength and dissipative capability of CFRP reinforcement sheets. Nevertheless, their use in technical practice is discouraged by the lack of specific rules that adequately support designers. The development of predictive formulas, appearing necessary to bridge this gap, requires an extensive experimental database that highlights the peculiar characteristics of these reinforcements. As a contribution in this field, this paper presents an experimental program concerning the analysis of the mechanical behavior of this type of reinforcements applied to masonry structural elements loaded by out-of-plane actions. The experimental results showed that the effectiveness of such anchors strongly depends on the shape ratio of the specimens.

The use of composite materials, in particular Carbon Fiber Reinforced Polymers (CFRP), as reinforcement of masonry structures is more and more widespread in the structural rehabilitation and retrofitting of existing buildings. Several research findings reported in the literature demonstrated that externally bonded CFRP sheets can effectively increase the mechanical performance of masonry walls subjected to both in-plane and out-of-plane actions. Concerning the latter, most research activities refer to monotonic actions. Seeing the lack in the literature, the experimental program described in this paper is aimed to the analysis of the effects of load cycles in the out-of-plane behavior of reinforced masonry walls.

Carbon Fibers Reinforced Composite (CFRP) materials are widely used for structural rehabilitation and retrofitting of both masonry and concrete structures. Recent studies published in the literature are devoted to the analysis of novel methods to increase CFRP-to-substrate bond capacity. Among these, spike anchors demonstrated to be able to effectively increase both strength and ductility of CFRP reinforcement sheets. Since most of the literature in this field refers to CFRP-to-masonry reinforcements loaded by in plane actions, the experimental research described in this paper is devoted to the analysis of the effectiveness of spike anchors in CFRP reinforcements bonded to masonry structural elements loaded by out-of-plane actions.

In this paper the consequences of solar radiation on the behavior of laminated glass with PVB interlayer are experimentally evaluated. The experimental campaign reported is based on the repetition of four point bending tests in creep condition, on laminated glass beams while subjected to increasing exposition time to artificial solar radiation. In so doing, bending test in creep condition is used as a not destructive test to highlight the modification of interlayer coupling capability and the scattering of results due to specimens variability is avoided. The constitutive relations of material, based on linear viscosity and thermo-rheological simplicity, are calibrated on previous experiments in order to reproduce the behavior of blank specimens at different temperatures. The possibility of determining some damage parameters that account for the modification attained by interlayer while exposed to solar radiation, is investigated.

In this paper the experience is reported of the use of 3D printing for the dissemination of a cultural content. When Filippo Brunelleschi vaulted the dome of Santa Maria del Fiore in Florence without using any scaffolding, demonstrated the ability to control the constructive process in its structural essence. The comprehension of the static principles that stand at the base of the equilibrium of a circular dome are necessary to understand the work of the architect and the reason of the herringbone brickwork adopted. These principles can be easily explained, also to people who do not have any technical education, by means of a three dimensional model. A wood model realized by hand in the ’80 was reproduced in a smaller scale with 3D printing. The geometry of the model was easily reproduced with a parametric modelling software and was then elaborated to produce the geometric models for sintering polyamide voussoirs. A comparison is attempted between the cost of the two physical models in term of work time and print time, and a balance is made to highlight the value added to the production of such didactical models by the 3D printing process.

Mechanical properties of interlayer polymers are recognized to be essential for a correct design of laminated glass structures. Although several researches have been carried out on the consequences of weathering actions on a laminated glass, few quantitative data on the properties of polymers are available. The response of structures to a long duration load is therefore evaluated taking into account the effects of viscosity of the interlayer, but in the hypothesis that the interlayer material does not degrade over time. In this paper the results are reported of an experimental analysis of the thermo-viscoelastic properties of polyvinyl butyral used as interlayer of laminated glass, subjected to weathering actions (humidity, thermal cycles and UV radiation). The results were interpreted in the light of the connection between microstructure and rheology of polymers, and highlight two different damage mechanisms, promoted in different extents by the different weathering actions.

Fiber reinforced composite materials are widely used for structural rehabilitation and retrofitting of existing buildings; recent studies, devoted to Carbon Fiber Reinforced Polymers (CFRP) reinforcements of concrete structural elements [1–5], demonstrated that spike anchors are able to effectively increase the load carrying capacity and the ductility of CFRP bonded joints. However, application to masonry structures is disregarded by research since few experimental results are available. One of these, described in Refs. [6,7], compares the efficiency of a CFRP strengthening system provided with one or more CFRP spike anchors, also in dependence of some geometrical parameters; reinforcement sheets and spike anchors were applied only on the brick surface in order to evaluate the effects due to anchors only. In this paper the authors investigate the influence of mortar joints on the efficiency of anchored CFRP reinforcements on brick masonry. For this reason, an experimental campaign was planned on masonry pillars built with the same materials employed in Refs. [6,7], subjected to Near End Supported Single Shear Tests. Masonry pillars were built according to two different patterns, in order to detect the influence of both bed and perpend joints. The results are compared with results obtained from previous experimental campaign.

Current standards introduce different test methods to be used for the determination of the dynamic properties of polymers. Some of these have been applied in the last years for the evaluati...

The first results of an experimental campaign are reported that evaluates the efficiency of anchored CFRP reinforcements on brick masonry. Near End Supported Single Shear Tests were carried out on masonry pillars made according two different patterns, in order to detect the influence of both bed and perpend joints. The results are compared with results obtained from previous experimental campaign in which CFRP reinforcements were applied on “only brick” surfaces.

Fiber reinforced composite materials are widely used for structural rehabilitation and retrofitting of existing buildings. Failure of not anchored CFRP reinforcements, applied to both concrete and masonry, mainly occurs in the substrate or at the bonding surface, for load values lower than the tensile strength of the composite. Mechanical anchors can effectively increase the maximum load of this type of reinforcements. Particular attention should be paid to the design and sizing of mechanical anchors so that these can produce adequate increments of both strength and ductility of the reinforcement. At the moment there are no specific rules or reliable predictive formulas that adequately support designers in the design choices and sizing of anchors. Of course, these can be defined only after collection of an extensive experimental database that highlights the peculiar characteristics of these reinforcements also with reference to the substrate material. In this context, the present work describes the results of an experimental campaign carried out on brick specimens reinforced with CFRP strips, anchored to the substrate by CFRP spike anchors. Almost all research in the literature about this topic refers to the use of this reinforcement technique for concrete structural elements. Studies concerning masonry are limited: this work contributes to bridge part of this gap. Plane CFRP reinforcement strips generally exhibit brittle failure mode. The experimental campaign reported in this paper shows that properly designed mechanical anchors increase both the failure load and the ductility of the reinforcement.

This paper reports the results of an experimental campaign that aims at evaluating the capability of a composite made of jute fabric and stabilized earth matrix to act as a reinforcement of earth structures, and the analytical models able to interpret the results. Preliminary studies carried out in order to test adequate reinforcement systems for earthen structures, demonstrated that jute fabric applied with a stabilized earth plaster, among other natural fibers or systems, is able to develop exceptional adhesion and adequate stiffness. However, the collapse mechanisms observed seems to favor the rupture of reinforcement rather than the crisis of adhesion usually observed when dealing with artificial FRC reinforcements. It was necessary to step back to the theories of adhesion to plan the experimental analysis of the jute reinforcement for rammed earth structures. The poor material, the fact that adhesive and support are almost the same material (differing only for grain size, density and a small amount of gypsum), the difficulty in measuring fabric properties, strength and, most of all, local deformation and fracture energy in earthen materials, induced to define a specific procedure. The uncertainties connected to the determination of mechanical parameters were overcome both using statistical approach and numerical analysis of data, and reducing the number of parameters necessary to the analysis, that is turning to simple adhesion models.

Today, there is an increasing use of fiber reinforced polymer (FRP) composites in civil engineering as reinforcement of existing structures. In particular, FRP composites offer higher strength and Young’s modulus than traditional steel devices, also easy handling and installation, excellent resistance to corrosion and they can be plastered after application. When FRP wraps are used to confine compressed pillars, the effective contribution of the composite cannot be accurately evaluated because it begins to work as the stress state of the member grows. In the present paper, some theoretical relationships available in literature and in current international design guidelines, regarding the evaluation of confinement effect on wrapped concrete columns, are analyzed and compared with experimental test results. Based on these considerations, we propose a new formula that is in good agreement with the experimental test results that were produced for the purpose and reported both in the present paper and in a previously published research study. Although empiric, the proposed formula is able to reproduce the structural response of wrapped specimens and the failure mode as observed in the experimental tests.

Fibre-reinforced composite materials have gained an increasing success, mostly for strengthening, retrofitting, and repairing existing structures. However some problems may arise with the use of traditional FRP (Fiber Reinforced Polymer), particularly when the compatibility with the substrate and the reversibility of the intervention are required, as in case of cultural heritage buildings, or specific exposition conditions may compromise the long term effectiveness of the reinforcement, as in presence of high temperature and humidity. Starting from these considerations new composite materials are emerging as a more effective solution in certain fields of application and under specific service conditions; in this context, mortar-based composite systems, consisting of one or more layers of uni- or bi-directional fibre nets embedded in cement/lime-based matrix layers, can be used as reinforcement of both concrete and masonry structures. However, the research work dealing with these emerging materials and their performances when used as a strengthening system for existing structures is still limited. Both experimental and theoretical investigations are needed in order to deliver reliable design methodologies. In this work, a Round Robin Test aimed to the characterization of both bond with the existing substrate and tensile performance of glass fabric (in the form of grids) coupled with inorganic mortar matrices is presented. The investigation was conducted at fifteen laboratories involved in the RILEM Technical Committee 250-CSM (Composites for the Sustainable Strengthening of Masonry). With the aim of studying the bond behaviour between Fabric Reinforced Cementitious Matrix (FRCM) composites and masonry substrate, single and double lap shear tests were carried out on brick-masonry prisms. Results provide useful informations about the mechanical properties, the bond capacity and the failure mechanisms of different commercially available glass FRCM systems. Finally, critical aspects are underlined to address the progress of research work., info:eu-repo/semantics/publishedVersion

This research deals with the mechanical characterization of laminated glass beams (glass-interlayer-glass) subjected to bending, with the main purpose of evaluating the coupling that the interlayer is able to establish between the glass sheets; in fact, the interlayer provides the glass plies with the ability to work more or less jointly. Four-point-bending tests (constant load) were performed on glass beams laminated with different interlayer plastic sheets. Shear tests (constant load) were performed on laminated glass specimens to determine the viscosity properties of the interlayer, when laminated between glass sheets. The parameters of viscosity, determined by the shear tests, make it possible to reproduce the time-dependent behavior of the composite beam, both numerically and by means of a closed-form procedure. The experimental results were compared with those obtained with the theoretical model and with the numerical simulation. The comparison among the different polymer interlayers shows that they are able to influence differently the mechanical behavior of the laminated composite and that their performance degrades at different rates as a function of time.

Numerical procedures are developed for the homogenization and evaluation of the stress field in a composite as a consequence of the presence of embedded SMA (shape-memory alloy) wires. In particular, the elastic field developed at the end of the SMA wire self-strain process is studied, knowledge of which is necessary to evaluate the feasibility of such a hybrid composite. First, the numerical procedures are applied to the study of both a representative volume element (RVE) included in a theoretically infinite periodic medium and a RVE located near the medium free boundary, in order to evaluate the tangential stress field generated at the end of the fiber; then they are applied to the study of a plate able to bend after the effect of self-strain of the SMA wire. Observations are reported about the obtained results and about the similarities and the differences between the two problems.

Fiber-reinforced polymer (FRP) composites are more and more used in the building trade for the set up of reinforcing and repair devices. As known, FRP composites offer higher strength and Young modulus than traditional steel devices, but nowadays technologies are not able to produce pretension of the wrap in civil engineering strengthening applications. Moreover, when confining compressed masonry columns with FRP composites, the effective contribution of the composite cannot be accurately evaluated. In the present paper, some theoretical relationships available in literature are analyzed, regarding the evaluation of confinement effect on wrapped masonry columns. The reliability of these formulations is investigated, comparing the theoretical values with unixial and triaxial experimental test results; unixial tests were carried out both on plain and wrapped brick masonry samples. Experimental results are shown not to fit to the formulas of the literature and the reasons of the discrepancy were searched for...

A micromechanical model is proposed for determining the overall linear elastic mechanical properties of simple-texture brick masonry. The model, originally developed for long-fiber composites, relies on the exact solution due to Eshelby and describes brickwork as a mortar matrix with insertions of elliptical cylinder-shaped bricks. Macroscopic elastic constants are derived from the mechanical properties of the constituent materials and phase volume ratios. Conformity of the suggested model to real brickwork behavior has been verified by performing uniaxial compression tests on masonry panels composed of fired bricks and mud mortar. Composite masonry panels of varying phase percentages were then constructed and tested by replacing several of the fired bricks with mud bricks. Comparison of experimental results with theoretical predictions demonstrates that the model is suitable even in the presence of strongly differentiated phases, and is moreover able to predict different behavior as a function of phase c...

Many studies reported in the literature are able to demonstrate significant influence of weathering on physical and mechanical properties of PVB. In this paper, the results of these researches are compared and discussed. The effects of rheological parameters modifications on the coupling capability of laminated glass structural elements and on the mechanical response to loads are then evaluated through numerical analysis. Real structures are often exposed to direct sunlight or to temperature or humidity levels that can induce damage phenomena in the interlayer; the modification of mechanical coupling capability and of adhesion properties of interlayer that effectively take place in laminated glass structures have to be taken into account in the design process as they probably affect the behavior of the structure not only in the serviceability state but especially in the ultimate limit state., Challenging Glass Conference Proceedings, Vol. 5 (2016): Challenging Glass 5