bluuebunny/crossref_metadata_2025 huggingface dataset:
Reducing Seismic out of Plane Vulnerability of Masonry Church Façades through Optimization of Capacity Spectrum by Tie Rods
Authors: Baraccani Simonetta , Dan Giorgio , Di Tommaso Angelo , Trombetti Tomaso
Published: August 2019

The analyses of the structural damages detected on the Italian churches after the recent earthquakes (Emilia 2012, Umbria-Marche 2016) highlighted the high vulnerability to the overturning of the façades. The façades collapse mechanisms are strongly dependent on the connection details between orthogonal masonry walls, the windows, the construction techniques and the possible restraining horizontal elements, such as tie-beams, bi-lateral connected roof, etc. Several studies focus on the evaluation of vulnerability of the church façades using different approaches, from global analyses (FEM and /or Discrete Element Methods) of the entire building, to local analyses (linear and non-linear kinematic approaches). The aims of the present paper is to use the method based on capacity spectra to evaluate the vulnerability of the church facades and the optimization of specific devices as tie-rods to improve their seismic behavior. The non-linear approach is now accepted by several standards regarding the evaluation of risks of collapse mechanisms for masonry walls of the facades. Appropriate devices have been considered in order to calibrate the capacity curve and to optimize the interventions. The out of plane rotation of blocks can be modified with various elasto-perfect-plastic tendons with appropriate retentions (while composite materials could be used to preserve integrity of blocks). The tendons can be allocated in proper location and the length of each calibrated to best determine their stiffness. This procedure have been here applied to the study of the façade of Aula Magna S. Lucia of the Bologna University, considering also the problem of the interaction with the structure of the roof.
Tracking Modal Parameter Evolution of Different Cultural Heritage Structure Damaged by Central Italy Earthquake of 2016
Authors: Ribilotta Elisa , Giordano Ersilia , Ferrante Angela , Clementi Francesco , Lenci Stefano
Published: August 2019

The preliminary results of an ambient-vibration based investigation conducted on a large sample of historic masonry towers in the Marche region (Central Italy) are presented, with a focus on the belfry of Collegiata of Santa Maria in Visso (Italy). The assessment procedure includes full-scale ambient vibration testing, modal identification from ambient vibration responses, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. As the most doubtful parameters, the modulus of elasticity of the masonry is adjusted to achieve the experimental results with numerical model by simple operations.
Numerical Modelling of the Experimental Response of SRG Systems
Authors: Malena Marialaura , Sangirardi Marialuigia , Roscini Francesca , de Felice Gianmarco
Published: August 2019

Modern repairing and retrofitting methods for existing structures make use of composite materials, consisting of high strength textiles and a matrix, which can be either polymeric or inorganic. These kinds of techniques have been largely applied to masonry structures, since they significantly improve structural performance with a small increase of weight and a minimum invasiveness. However, the application of organic gluing agents on masonry has revealed some well-known drawbacks, which are almost all overcome resorting to inorganic matrixes, namely cement or lime mortars. An entire class of composites is thus identified as TRM (Textile Reinforced Mortars) or FRCM (Fibre Reinforced Cementitious Matrices). Among them, Steel Reinforced Grout (SRG) are characterized by Ultra High Tensile Strength Steel (UHTSS) cords embedded in mortar matrix and their use to improve the structural performance of existing historical masonry buildings is becoming more and more diffused. Qualification tests and acceptance criteria for SRG have just been defined. Nonetheless, numerical simulation of current available test procedures is mandatory to identify peculiar aspects of the response that at a following stage become an integral part of large scale models, when entire reinforced structures or portions need to be analysed. To this end, this work presents the numerical modelling of two different direct tensile tests on SRG systems: the Clamping-grip setup (RILEM Technical Committee 232-TDT 2016) and the Clevis-grip setup (ICC-ES AC434 2016). Numerical models able to replicate experimental tests and catch fundamental differences in their failure mechanisms are present
Preliminary Results on the Tensile Capacity of Steel Anchors in Brick Units of Different Materials
Authors: Chen Peng Zhen , Finelli Francesco , Franzoni Elisa , Gentilini Cristina , Sansone Gabriele
Published: August 2019

High strength steel bars are widely used for the strengthening of masonry buildings, in particular to improve the connection between different structural elements, such as orthogonal walls and multi-leaf walls. A particular type of steel connector is the twisted bar, which due to its particular shape works as a self-threading screw, anchoring to the support material without any binder. The effectiveness of such technique mainly relies on the bond between the bar and the substrate, where adhesion, mechanical interlocking and friction play an important role. In this paper, a preliminary experimental study on pull-out behavior of twisted steel connectors inserted in brick units of different materials that can be commonly found in existing masonry buildings in Italy and in Europe is presented. Additionally, mechanical characterization of the materials is conducted to understand the influence of the compression strength and elastic modulus on the adhesion between the connector and the substrate. Preliminary results show that the pull-out response strongly depends on the mechanical properties of the substrate material.
On the Use of Digital Image Correlation (DIC) for Evaluating the Tensile Behaviour of BFRCM Strips
Authors: D'Anna Jennifer , Amato Giuseppina , Chen Jian Fei , Minafò Giovanni , La Mendola Lidia
Published: August 2019

Fibre Reinforced Cementitious Matrix (FRCM) composites are becoming largely adopted for retrofitting masonry structures. These materials offer several advantages in comparison to Fibre Reinforced Polymer (FRP) composites, such as good resistance to fire and high temperatures, vapour permeability, possibility to be applied on wet surfaces, higher compatibility with the masonry substrate. However, the tensile behavior of FRCM materials is more complex compared to FRP composites, due to the limited tensile strength of the cement-based matrix. For this reason, FRCM materials require appropriate tensile characterization and, in this context, the use of non-conventional measurement systems, such as the Digital Image Correlation (DIC), can offer numerous advantages. This work presents an experimental study on the application of the DIC technique for the tensile characterization of Basalt Fibre Reinforced Cementitious Matrix (BFRCM) strips. Tensile tests were carried out on three series of specimens reinforced with one, two or three layers of basalt grid in order to investigate the effect of the reinforcement ratio on the tensile response of the composite strips. The test setup and the calibration of the DIC analyses are discussed. It is shown as the DIC allows obtaining detailed information on the tensile response, including the evaluation of the full strain field on the surface of the BFRCM strips and the location of cracks. Results are discussed also in terms of stress-strain curves and failure modes.
Composite Materials with Natural Fiber NFRC on Inorganic Matrix for Seismic Reinforcement of Masonry Structures
Authors: La Tegola Antonio , Mera Walter
Published: August 2019

Composite materials with carbon, aramidic, glass and lately basalt fibers with a polymeric or cementitious matrix FRP or FRC, are frequently used for the seismic reinforcement of masonry buildings. The fibers of such composites are synthetic, and they have high mechanical characteristics. However, their cost is very expensive and do not belong to the eco compatible products. Moreover, for the making of these fibers an elevated amount of energy is needed for reaching the temperature relative to the production process.An alternative to the use of such fibers may be recurring to natural eco compatible fibers for which the cost is much lower, and they do not need a special processing. Using such fibers in an inorganic cementitious matrix, an improvement of the mortar or of the plaster quality is obtained, giving to them also an adequate ductility.In order to make the composite material, short fibers immersed in the cementitious mortar are used; the composite material can be represented using the acronym NFRC (Natural Fiber Reinforced Composite).Among the different types of fibers that can be used, there is the short fibers derivate from the bamboo plant that are available under the form of yarns or threads.The scope of this paper consists in the definition of the optimal volumetric ratio for the NFRC composite, and the length of the fiber compatible with the workability and the resulting mechanical characteristic.
Confinement of Masonry Columns with PBO and Basalt FRCM Composites
Authors: Ombres Luciano , Iorfida Antonio , Verre Salvatore
Published: August 2019

A new generation of composite materials in the form of Fiber Reinforced Cementitious Matrix (FRCM) was recently used to strengthen the masonry structures. Six small scale masonry columns were tested under monotonic concentric load until collapse; three columns were confined with PBO (short of polyparafenilenbenzobisoxazole)-FRCM jackets, two with basalt–FRCM jackets while an unconfined column was used as a control specimen. The masonry columns investigated have a rectangular cross section 250x250 mm among the overall length equal to 770 mm, and the corners were rounded to a radius of 20 mm. The analysis was conducted varying the confinement ratio i.e. the number of fabric layers for each FRCM system. Obtained results allow evidencing the effectiveness of the confinement and the effect n-layer on the structural response of the masonry columns.
Discontinuous CFRP-Jacketing of Masonry Columns
Authors: Lerna Michele , Micelli Francesco , Cascardi Alessio , Aiello Maria Antonietta
Published: August 2019

Existing masonry columns are often susceptible to cracking due to overloading. Moreover, their fragility under earthquakes’ forces is of particular concern in seismic-prone regions. In order to mitigate these structural deficiencies, Fiber Reinforced Polymers (FRPs) are commonly used for external confinement. Full-jacketing, by means of FRP-wrapping is recognized to be very effective in improving the load bearing capacity and the ductility of masonry columns. Unfortunately, long-term effects seem to be detrimental for the masonry core, since its breathability is obstructed by the polymeric resin. Thus, a discontinuous application of the FRP-confinement appears to be more indicated in stone-masonry columns, allowing the humidity cycles to recur. On the other hand, the discontinuous wrapping negatively affects the confinement effectiveness, since both confined and unconfined masonry regions participate in the bearing capacity. In this sense, the present research is aimed to study the discontinuous confinement of half-scale masonry columns by means of Carbon-FRP strips. Unconfined and confined specimens were tested under uniaxial compression. The CFRP-confinement was studied by investigating the lateral strain in the confined and unconfined portions of the specimens. The results are reported and discussed in the paper in terms of failure modes, axial stress-strain and axial stress versus lateral strain relationships. The outcomes are reasonably convenient for a proper analytical interpretation of the phenomenon.
Structural Repointing of Masonry Structures
Authors: Gonzalez-Libreros Jaime , D'Antino Tommaso , Focacci Francesco , Carloni Christian , Pellegrino Carlo
Published: August 2019

Existing masonry structures are often in need of strengthening due to the limited masonry tensile strength and consequent occurrence of cracks, which can lead to collapse of the structure. To control the cracking phenomena and increase the load associated with a certain collapse mechanism, structural repointing by means of reinforcing bars inserted in the mortar bed joints can be employed. Fiber reinforced polymer (FRP) bars have been used for repointing due to their high tensile strength and good resistance to corrosion. Although structural repointing is a well-known and diffused strengthening technique, limited research is available in the literature and reliable analytical models to compute the structural capacity of repointed members are missing. In this paper, experimental results of masonry members strengthened with structural repointing found in the literature are analyzed and discussed to provide indications on the contribution of repointing in the masonry strength and identify mechanical models able to predict the failure load of repointed masonry members.
An Experimental Investigation on Pull-Off Tests Conducted on FRP Composites Applied to Brick Units
Authors: Ghaemi Mahdi , Di Tommaso Angelo , Gentilini Cristina
Published: August 2019

In the present study, a series of pull-off tests is performed to determine the bonding properties of fiber reinforced polymer (FRP) composites applied to a brittle substrate. Pull-off test is simple, fast and cheap and it is generally employed to evaluate the bond strength between the composite and the substrate. It is a procedure that can be easily performed on-site for checking the quality of the reinforcement adhesion.A steel composite made of a unidirectional steel fabric embedded in an organic matrix (bi-component epoxy resin) was applied to the surface of fired-clay bricks. A shallow core perpendicular to the surface was realized in the test specimen, leaving the core attached to the brick. A steel dolly was glued to the external surface of the core using epoxy adhesive. A loading device was employed to apply the tensile force until failure. The effects of moisture presence on the substrate and shape of the cores on the pull-off strength were investigated.
Mechanical Behaviour of Masonry Panels Strengthened by Flax TRM Systems
Authors: Ferrara Giuseppe , Caggegi Carmelo , Gabor Aron , Martinelli Enzo
Published: August 2019

Among the existing techniques to retrofit and reinforce masonry elements, the use of Textile Reinforced Mortar (TRM) composite systems represents these days an efficient and compatible solution. Aiming to improve the sustainability of these composite systems, the efficiency of plant fibres as reinforcement fabric of TRMs is analysed in the present study. Specifically, relying on previous works concerning the mechanical characterisation of the system on a local scale, it proposes an experimental analysis on a greater scale of investigation. Clay bricks masonry panels (1 x 1 x 0,12 m3) strengthened by a Flax-TRM system (hydraulic lime-based matrix) were subjected to diagonal compression tests. Two strengthening configurations characterized by one and two layers of flax fabric were tested. The reinforcement was applied all over the surface of both the panel sides. The response of the externally strengthened walls is examined and compared herein with that of unstrengthened walls. The results show that the reinforcing system strongly influences the performance of the walls by conferring them a post-peak behaviour totally absent in the brittle response typical of unstrengthened walls. In terms of peak load, an increase of the 118% and 136% is observed respectively in panels externally strengthened with one and two layers of textile, with respect to the unstrengthened walls. The experimental study confirms a considerable potential in the use of plants fibres as reinforcement of TRM composite systems for the strengthening of masonry elements and paves the way for further investigation aimed to improve their mechanical behaviour.
Numerical and Theoretical Models for NFRCM-Strengthened Masonry
Authors: de Carvalho Bello Claudia Brito , Baraldi Daniele , Boscato Giosuè , Cecchi Antonella , Mazzarella Olimpia , Meroi Emilio , Aldreghetti Ivano , Costantini Giorgio , Massaria Lorenzo , Scafuri Vincenzo , Tofani Italo
Published: August 2019

The shear behavior of masonry strengthened with natural fabric-reinforced cementitious matrix (NFRCM-strengthened masonry) is investigated through two different numerical models: a multi-layer model considering masonry and reinforcement as different materials and a multi-step homogenized model, where reinforced masonry is considered as a whole. The approaches are compared by performing nonlinear numerical pushover analysis with an increasing shear action applied to the panels. The parametric analysis shows the capacity and limits of both continuous diffused models – defined as a multi-or a single layer - to represent reinforced masonry in-plane behavior.
The Effects of Strengthening the AAC Walls Using Glass Mesh Arranged in Different Configurations
Authors: Kałuża Marta , Kubica Jan
Published: August 2019

The usage of AAC (Autoclaved Aerated Concrete) blocks for the construction of new masonry structures, particularly low-rise residential buildings, has become very popular in Poland. It provides an uncomplicated erecting method, which is characterized by thin bed joints and unfilled head joins, but at the same time, makes these walls very sensitive to any internal tensile stresses, causing damage with varying intensity. To avoid premature cracking, leading to a brittle failure of existing walls, an external strengthening can be an acceptable and effective solution. Taking into account that AAC units are a natural material, the application of a FRCM system (instead of FRP) is more suitable here. This system uses a mineral-based matrix that provides congenial compatibility with a masonry substrate.This study presents an analysis of the influence of superficial strengthening on the behaviour and deformability of masonry walls made of AAC blocks. A typical glass mesh (most often used in thin external plastering) and mineral mortar dedicated to renovation works are used as strengthening materials. The specimens are strengthened unilaterally (two types) or bilaterally and are subjected to diagonal compression according to the RILEM 76-LUM standard. The consecutive work stages, shear strains and modes of failure are described and discussed.
Local FRP-Reinforcement of Clay Hollow Block Panels under Shear Loading
Authors: Borri Antonio , Corradi Marco , Sisti Romina , Molinari Alessio , Quintaliani Chiara
Published: August 2019

The use of clay hollow blocks is common for new constructions in many parts of Europe. The results of 8 full-scale shear tests of block-masonry panels (dimensions 1.60x0.90x0.25 m) are reported in this paper. Non-defective and defective wall panels were tested in shear in the laboratory. Typical failure modes are investigated, not previously reported in the scientific literature. Test results show that the lateral load capacity of the panels is highly affected by construction defects. Furthermore, CFRPs were used in this research as local reinforcement (repair) in the area around the cracks previously opened in the masonry material. The lateral capacity for CFRP-repaired panels was restored to the original value of non-defective panels, indicating that the CFRP-repair of cracked panels is viable solution. An explanation for this phenomenon is suggested, which indicates that the high tensile strength of CFRPs can be effective in repairing cracked block-masonry. It is also argued that this large stress level of the CFRPs leads to a premature tensile CFRP crisis or a splitting failure of the blocks’ shells.
Mechanical Characterization of SRG Composites According to AC434
Authors: Campanini Davide , Hadad Houman A. , Carloni Christian , Mazzotti Claudio , Nanni Antonio
Published: August 2019

In the last decades, technologies and materials such as fiber reinforced polymer (FRP) have been used to strengthen different types of existing structures. More recently, composites have been developed consisting of reinforcement fabrics embedded in an inorganic mortar. These composites are known as fabric reinforced cementitious matrix (FRCM), when the fabric is made of aramid, glass, basalt, polyparaphenylene benzo-bisoxazole (PBO) or carbon fibers, and steel reinforced grout (SRG), when the fabric is made of twisted high-strength steel cords. In the United States, the characterization of FRCM/SRG systems is conducted in accordance to Acceptance Criteria AC434. According to AC434, the tensile properties of FRCM/SRG are obtained through a direct tensile test on coupons using clevis grips.The objective of this research is to discuss the applicability of the AC434 test method to determine the mechanical properties of SRG as a function of the length of the anchoring plates. SRG panels were cast and stored in a humidity chamber. After a 28-day curing period, they were cut to size and metal plates of different lengths adhered to their extremities. Results show that not all the assumptions currently made in AC434 are applicable to this type of composite. The experimental response was characterized by a trilinear stress-strain behavior. Furthermore, the cracked modulus calculated based on stress values between 60 and 90% of the ultimate stress does not accurately represent reality. Re-evaluation of this provision is of importance since the cracked modulus is used in design.
Mechanical Behavior and Failure Modes of Two Different Steel-FRCM Systems on Masonry Substrate: Experimental Investigation
Authors: Bencardino Francesco , Nisticò Mattia , Ombres Luciano , Verre Salvatore
Published: August 2019

The results of single-lap shear tests, carried out on specimens with Steel Fabric Reinforced Cementitious Matrix (S-FRCM) composite strips bonded to masonry units, are presented in this paper. The S-FRCM composite system represents a newly developed promising technique for strengthening the masonry structures. The S-FRCM composite was comprised of steel fiber strip embedded within two layers of inorganic matrix. Two kinds of steel fibers can be used: ultra-high tensile strength steel galvanized micro-cords and/or stainless steel strands. The main differences between the two fibers are: E modulus with a ratio of 2.58 and tensile strength with a ratio of 2.04. This experimental investigation was carried out in order to obtain the information on the fundamental behavior of the bond between masonry and the two types of S-FRCM composites, which is the critical phenomenon in structural strengthening applications due to a slip of the fibers and fracture of the external matrix layer at the fiber-matrix interface. The results were analyzed and showed in terms of failure modes, failure loads, load-global slip curves, and other parameters.
Structural Behavior of Small-Scale Masonry Panel with Fiber Reinforced Mortar under Compressive Load
Authors: Bencardino Francesco , Cecchi Antonio , Franceschi Massimiliano , Nisticò Mattia , Ombres Luciano , Verre Salvatore
Published: August 2019

The use of fiber reinforced mortar for structural retrofitting/new construction of masonry structures has become increasingly popular in the last years. A preliminary study on the mechanical performances under compression of masonry panels is performed by selecting three different mortar types. The panels were composed of mortar and clay bricks; the mortars adopted are the following: i) commercial type mortar, ii) traditional mortar and iii) traditional mortar with the addition of a cellulose-based industrial non-hazardous waste. In particular, the study proposes the use of deink paper sludge as mortar filler as an example of sustainable end-of-life reuse. Using the collected experimental results involving the mortars and clay brick form a regression analysis on compressive strengths was performed in order to evaluate the influence of the deink paper sludge on the compressive behavior of the panel.
Shear Capacity of Masonry Panels Reinforced with Inorganic Strengthening Systems
Authors: Del Zoppo Marta , Maddaloni Gennaro , Balsamo Alberto , di Ludovico Marco , Prota Andrea
Published: August 2019

Unreinforced masonry buildings are particularly vulnerable to brittle failures during seismic events due to the poor in-plane shear capacity of masonry walls. The use of strengthening solutions with polymeric matrices is not often recommended for masonry buildings, due to breathability issues, and the adoption of inorganic matrices is sometimes considered preferable. In this paper, the use of inorganic composite materials for improving the in-plane shear capacity of tuff masonry walls is investigated. The experimental data from 83 diagonal compression tests carried out at the University of Naples Federico II in recent years have been collected and the main results are herein discussed to outline the main features of different strengthening techniques with inorganic composite materials such as Reinforced Plaster (RP), Composite Reinforced Mortar (CRM) and Fabric Reinforced Cementitious Matrix (FRCM).
On the Lateral Capacity of Reinforced Masonry Members Using Combined Retrofitting Methods
Authors: Borri Antonio , Sisti Romina , Corradi Marco
Published: August 2019

Historic walls were designed in the past to withstand vertical compressive loads. However, during seismic events, walls withstand lateral loads and their response is usually unsatisfactory. Reinforcement is often needed and several retrofitting methods have been proposed in the last decades. This paper analyses and compares the strength results of several experimental campaigns, recently carried out by the authors, with the specifications and mechanical properties suggested by the new (2018) Italian Seismic Code. Two retrofitting methods are considered: grout injections, alone, and in combination with jacketing. The effect of combined retrofitting methods was also investigated in this paper with the aim at studying the limitations of the actual Italian Building Code for interventions on listed buildings. Shear tests were carried out on-site and the effectiveness of the two retrofitting methods was discussed.
Assessment of 3D Linear Elastic Masonry-Like Vaulted Structures
Authors: Briccola Deborah , Bruggi Matteo , Taliercio Alberto
Published: August 2019

A novel approach is adopted to assess the static behavior of vaulted structures, such as cantilevered masonry stairs, assuming a linear elastic no-tension material model. Masonry is substituted by an equivalent orthotropic material whose elastic properties vary locally and with a negligible stiffness where tensile strain occurs. In order to recover a tension-free state of stress, an energy-based minimization procedure is carried out to establish the distribution and the orientation of the equivalent material for a given compatible load. The capability of the approach in defining purely compressive stress solutions in masonry walls under dead load and both in-plane and out-of-plane live loads has already been assessed. A meaningful application to a cantilevered masonry stair is here presented; the results are in good agreement with those available in the technical literature on historical masonry constructions.
Experimental Assessment of Geopolymer Grouts for Stone Masonry Strengthening
Authors: Baltazar Luis G. , Henriques Fernando M.A. , Temporão Diana , Cidade Maria Teresa
Published: August 2019

Grout injection is a useful repair and strengthening technique to intervene in old masonry buildings. Until now, a very limited amount of work has been reported on the potential of geopolymers for consolidation of old stone masonry walls. In the last decades there has been several research initiatives focus on the development of materials involving a higher volume of supplementary cementitious materials that substitute the traditional binders. Geopolymers that were developed as a part of these efforts, can not only reduce the dependence on traditional binders, but also potentially present materials with less environmental impacts and improved performance. This study investigates the fresh and hardened properties of grouts composed of natural hydraulic lime (NHL) and geopolymer. The experiments were conducted using a geopolymer made of fly ash, sodium hydroxide and water. The effects of the replacement of NHL by the fly ash-based geopolymer (at the dosages of 0, 20, 50, 80 and 100%) on the rheological parameters, stability, water absorption, compressive strength and durability were investigated. The results showed that the geopolymer-based grout has several advantages regarding the mechanical strength, durability and fresh stability, but the improvement of their rheological performances proved to be a challenging task. Overall, the findings of this study will be useful in assessing the design of grouts incorporating alternative binders and consequently contribute to the improvement of the grouting technique.
Stress Redistribution in Glass Fibers of G-FRCM Composites
Authors: D'Antino Tommaso , Poggi Carlo
Published: August 2019

Fiber reinforced cementitious matrix (FRCM) composites are increasingly adopted as a strengthening technique for existing masonry structures. Among the different fibers that can be employed in the reinforcing open-mesh textiles, which are embedded within cement- and lime-based matrices, glass fibers are gaining popularity due to their low price and promising performances observed so far. However, the stress redistribution between the glass fiber filaments within the textile is often uneven, which strongly affects the performance of the FRCM when subjected to external forces. In this paper, the stress redistribution between the glass fiber filaments is studied on the basis of tensile tests on a glass fiber textile left bare and impregnated with organic and inorganic matrices. The parameters studied are the fiber textile tensile strength and elastic modulus. Different systems, including the digital image correlation (DIC) technique, were employed to measure the specimen tensile strain. The results obtained shed light on the tensile strength of the glass textile, which is a key parameter in the design of glass FRCM strengthening.
Diagonal Compression of Masonry Walls Strengthened with Composite Reinforced Mortar
Authors: D'Antino Tommaso , Carozzi Francesca Giulia , Poggi Carlo
Published: August 2019

The use of inorganic matrix composites to strengthen and retrofit existing masonry and concrete structures has been gaining increasing interest in the last years. Among them, composite reinforced mortar (CRM) systems are a promising solution to increase the shear and flexural capacity of masonry panels. CRMs are comprised of a relatively thin inorganic matrix layer reinforced with a bi-dimensional grid made with high-strength fibers impregnated with an organic matrix. They are compatible with the substrate due to the use of inorganic matrix, have good durability and high-strength-to weight ratio due to the use of reinforcing composite materials. CRM systems are still in their infancy and limited research is available in the literature. In this paper, masonry walls constructed with historical bricks typical of the north of Italy were strengthened with a CRM system including a glass composite grid and a lime-based mortar and were subjected to diagonal compression. Three walls were strengthened with the CRM and one was used as a control specimen. The results obtained showed that the CRM system significantly increased the shear strength of the masonry panels subjected to diagonal compression.
Experimental Shear Behaviour of Rammed Earth Strengthened with a TRM-Based Compatible Technique
Authors: Romanazzi Antonio , Van Gorp Michiel , Oliveira Daniel V. , Silva Rui A. , Verstrynge Els
Published: August 2019

Earthen constructions are spread worldwide, not only as architectural heritage but also as new buildings, in which a total of around one fourth of the global population is estimated to live in. Among the different raw earth techniques, rammed earth was widely used to build vernacular dwellings in different regions. Despite the raising awareness for the high seismic hazard, recognized seismic vulnerability and high seismic exposure associated with earthen structures, the reduction of their seismic risk has been a topic insufficiently addressed. In general, the seismic vulnerability of rammed earth structures is due to poor connections between structural elements (walls and floors), high self-weight and low strength of the material. Hence, a TRM-based strengthening technique is proposed to improve their seismic capacity. To estimate the enhancement of the in-plane performance achieved with the TRM, an experimental program was conducted. Rammed earth wallets were tested under diagonal compression considering their unstrengthened and strengthened condition. The TRM strengthening was performed by embedding a glass fibre mesh (GRE) or a nylon mesh (NRE) in a compatible earth-based mortar. In general, the proposed TRM-based strengthening seems to improve the shear behaviour of rammed earth by enhancing the shear strength and promoting stress distribution after cracking, while no significant influence on the shear modulus of rammed earth seems to occur.
Grout Injection Effect on the Shear Behavior of FRCM Strengthened Stone Masonry Panels
Authors: Ferretti Francesca , Incerti Andrea , Tilocca Anna Rosa , Mazzotti Claudio
Published: August 2019

During the last decades, several seismic phenomena have shown the high vulnerability of existing stone masonry structures subject to horizontal actions. Innovative composite materials, such as Fiber Reinforced Cementitious Matrix (FRCM), can be adopted for the retrofitting of masonry structures. The use of these innovative FRCM systems is usually combined with a more traditional retrofitting technique: grout injection. It allows to restore or improve the transversal connection between wall leaves, ensuring a monolithic behavior of the structural element. The objective of this research was to analyze the effect of the quality of the grout injection on the shear response of FRCM strengthened stone masonry panels. Results from an experimental campaign, where stone masonry specimens were subject to diagonal compression tests, are therefore presented in this paper. Two samples were subject to grout injection and one of them was strengthened with Steel Reinforced Grout (SRG). Comparisons between the experimental results showed that grout injection alone, if correctly executed, could determine a significant improvement in the shear capacity of masonry panels. The application of the FRCM strengthening system could further enhance the behavior of the samples, especially influencing the failure mode. Comparisons with analytical formulations for the evaluation of the capacity of strengthened walls are also presented.
AE Characterization of Brick Masonry Walls Mechanical Behavior: The Case-Study of Alessandria and Boves Barracks
Authors: Viale Nicola , Accornero Federico , Lacidogna Giuseppe , Ventura Giulio
Published: August 2019

IIn the present study, Acoustic Emission (AE) monitoring technique is applied in order to characterize the brick masonry of two important military buildings located in Northern Italy: the barracks of Alessandria and Boves. The internal brick masonry walls of the two barracks object of the study are tested by two double flat-jack systems, in order to analyze the compressive strength of the structural material. Flat-jack testing is a versatile and powerful technique that provides significant information on the mechanical properties of historical constructions. The first applications of this technique on some historical monuments clearly showed its great potential. The flat-jack test method is only slightly destructive, and when double jacks are used, this test works according to the same principle as a standard compressive test. The difference is that it is performed in situ and the load is applied by means of two flat-jacks instead of the loading platens. During the tests, the stress-strain relationship of the masonry is determined by gradually increasing the pressure applied by the flat-jacks in the course of three loading-unloading cycles. Moreover, AE technique is coupled to the flat-jack testing, in order to assess the extent of damage in the masonry texture. Thus, AE technique makes it possible to highlight critical phenomena and fracture mechanics scale effects in the masonry by identifying the critical conditions, not entrusted to an analysis of the loading process (compression or shear), rather depending primarily on the distribution and evolution of crack patterns.
A Fe Model for TRM Reinforced Masonry Walls with Interface Effects
Authors: Gulinelli Pietro , Aprile Alessanda , Rizzoni Raffaella , Grunevald Yves Henri , Lebon Frédéric , Lovisetto Roberto , Tralli Sergio
Published: August 2019

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.
AE Damage Assessment in the Bell Tower of the Turin Cathedral
Authors: Manuello Amedeo , Masera Davide , Carpinteri Alberto
Published: August 2019

Historical churches, masonry towers and bell towers are structures subjected to high risk, due to their age, elevation and low base area on height ratio. In this work, an innovative monitoring technique for structural integrity assessment of historical buildings is reported. At the same time, the emblematic case study of the Turin Cathedral Bell tower is presented. The damage evolution in the tall masonry structure is described by the evaluation of the cumulative number of AE and by different parameters able to predict the time dependence of damage. In particular, since environmental disturbances have been minimized, and instrumental noises have been filtered out. The b-value analysis shows a downward trend to values compatible with the growth of localized macro-cracks at the base of the tower. These results seem to be in good agreement with the numerical analysis. Extension to longer monitoring periods and, later, investigation of different segments are strongly recommended to assess the stability of the monument.
Health Monitoring of Medieval Masonry Towers by an Acoustic Emission Approach
Authors: Lacidogna Giuseppe , Niccolini Gianni , Carpinteri Alberto
Published: August 2019

Non-destructive tests were performed to assess cracking evolution in two medieval masonry buildings, Sineo and Asinelli towers rising respectively in the Cities of Alba and Bologna, in Italy. As regards the case study of Alba, in situ compressive flat-jack tests on small-sized elements of the tower were conducted in conjunction with acoustic emission (AE) monitoring. At the same time, crack patterns taking place in large volumes of the tower were likewise monitored through the AE technique.As for the case study of Bologna, a masonry wall of the Asinelli tower was monitored during a period of intense seismic activity. The observed correlation between the AE activity in the monitored structural element and local earthquakes points out a significant dependence of deterioration processes in the tower on the action of nearby earthquakes.In both cases, the trends of two evolutionary parameters, the b-value and the natural time (NT) variance κ1, were derived from the AE time series to identify the approach of the monitored structures to a critical state in relation to the earthquake occurrence.
Fatigue Analysis of FRP Strengthened Masonry by Acoustic Emission Monitoring
Authors: Grazzini Alessandro , Lacidogna Giuseppe
Published: August 2019

The safety work of historical and monumental building heritage requires the use of innovative materials compatible with the high architectural value. The Fiber Reinforced Polymers (FRP) represent a valid alternative to traditional ones, and the carbon fiber sheets are very light and easy to glue to the masonry structures. However, the durability of the application of FRP sheets is still uncertain in the long time behavior, especially with regard to cyclic fatigue loads such as seismic ones. In this work an experimental analysis on a set of strengthened masonry walls under fatigue tests (loading and freezing-thawing test) has been carried out in order to evaluate creep effects. During cyclic tests in the laboratory it was possible to monitor the damage pattern through the acoustic emission (AE) technique. The AE monitoring is useful to estimate the amount of energy released from fracture propagation in the adherence surface between masonry and FRP sheet. The different phases of damage evolution are recognized through the analysis of AE data over time. In particular, the time dependence of AE counting number is useful to indicate the beginning of the unstable damage growth and predicts the possible failure of the specimens at the 80% of the test duration. Furthermore, a sudden decay in the AE frequency is detected during the last phase of the fatigue tests. These results illustrate the applicability and the advantages of AE technique for the monitoring of long-term damage growth in strengthened masonry.
Influence of Long-Time Work of 19th Century Modern-Type Roof Construction on Technical Condition of Vaults of Gothic Church
Authors: Ałykow Krzysztof , Napiórkowska-Ałykow Magdalena
Published: August 2019

The gothic church (1384) placed near historical Silesian-Saxon border in Lubań/ Poland was rebuild in 19th century, following the conservator’s doctrine their time, for purification the architectonical style. The gothic nave became new neo-gothic vaults and roof with modern wooden-steel carpenter construction. After a 100 years of rebuilding the nave, it was started to be visible damages caused by rheological processes in steel bars of modern roof construction as a cracks in the walls and both vaults, original gothic in presbyteries and 19th century in nave.
Structural Behaviour of Masonry Vaulted Staircases Using Limit Analysis: The Case Study of the Bell Tower of Santa Maria Delle Vigne
Authors: di Napoli Beatrice , Calderini Chiara , Rossi Michela , Vecchiattini Rita , Portioli Francesco , Cascini Lucrezia , Battini Carlo
Published: August 2019

The present study concerns the structural analysis of the masonry vaulted stairs of the Santa Maria delle Vigne bell tower in Genoa (Italy). The vaulted staircase systems are fully analysed in terms of technological and constructive details. The 3D geometric models are defined from laser scanner data. The structural analyses were carried out by using both the equilibrium limit analysis and a static incremental FEM analysis. Despite the efficacy of classic equilibrium methods in analysing arched and vaulted structures is largely proved in literature, this study demonstrates that vaulted staircase systems often collapse because of compressive failure of masonry before losing stability.
Damage Assessment of San Francesco Church in Amandola Hit by Central Italy 2016-2017 Seismic Event
Authors: Giordano Ersilia , Ferrante Angela , Ribilotta Elisa , Clementi Francesco , Lenci Stefano
Published: August 2019

Italy is a high seismic risk country since 1900 more than 30 earthquakes with magnitude greater than Mw=5.8 have occurred, and the last one is the Central Italy seismic sequence. The first shock occurred in the 24 August (Mw=6.2) followed by another stronger quake in the 30th October (Mw=6.5). It hit the regions of Marche, Umbria, and Abruzzo heavily causing many deaths, injuries and extensive damages on the cultural heritage. This paper analyses the church of San Francesco in Amadola, located in the Marche region that has been considered condemned for the severe damages reported after these earthquakes. The church is globally analyzed by the application of nonlinear static analysis on a Finite Element Model where the nonlinearity of masonry is taking into account with a proper constitutive law. The study wants to prove how global analysis combined by the local analysis can reproduce the behavior of this structure during a quake, showing that it can repeat the real damages produced by earthquakes.
Post-Cracking B-FRCM Strengthening of a Traditional Anti-Seismic Construction Technique (Casa baraccata): Extensive Experimental Investigations
Authors: Tiberti Simone , Scuro Carmelo , Porzio Saverio , Milani Gabriele , Olivito Renato S.
Published: August 2019

In the framework of the Mediterranean cultural heritage, the term “fictile tubule” identifies a peculiar type of brick, characterized by a cylindrical shape and a hollow core. Its unique geometry and characteristics rank it among the first hollow clay bricks in history. The large-scale production of fictile tubules allegedly began in the Roman provinces of Northern Africa during the 2nd Century A.D., where they were employed for building vaulted and domed structures without the need of centrings. Over the following Centuries, the construction technique of fictile tubules embedded in mortar was constantly refined and improved. This led to an extensive use of such technique in several buildings - as part of different structural elements (vaults, domes, floors, walls) - all over the Mediterranean area, and especially in Southern Italy. In 1909, after the disastrous earthquake in Messina and Reggio Calabria, Calabrian engineer Pasquale Frezza devised and patented an anti-seismic construction system which evolved the technology of casa baraccata. Frezza’s take on this traditional Calabrian way of erecting buildings involved the use of a specific type of fictile tubule, named carosello, alternated with common bricks in masonry walls, which are then encased in a timber frame. This paper presents an investigation on the structural behavior of Frezza’s evolution of casa baraccata, aimed at its possible revival as a relevant anti-seismic construction technique. Two specimen walls with dimensions equal to 60×60×15 cm3 are built according to Frezza’s patent and experimentally examined through a diagonal compressive test at the Civil Engineering Laboratory of University of Calabria. For the first specimen wall the test is carried out until failure to identify the collapse load. Conversely, for the second specimen wall the test is halted immediately after the formation of the first vertical cracks. The specimen is subsequently repaired using B-FRCM (Basalt Fiber-Reinforced Cementitious Matrix) as reinforcement, and the diagonal compressive test is repeated, this time until failure. The results in terms of collapse load and shear strength for both specimens are then compared and critically discussed, highlighting the increased load-bearing capacity of the wall built according to Frezza’s patent and reinforced with B-FRCM.