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The most recent design strategies welcome the adoption of innovative techniques for seismic energy input mitigation, aiming to achieve high dissipation capacity, prevent the structure from collapse and ensure the serviceability of the construction. Friction damper devices have been widely adopted in framed steel structures for decades, while their introduction in different structural types is still under investigation. This paper presents the outcomes of innovative research supported by the industry and conducted on beam-to-column connections of RC structures in which the beams are Hybrid Steel-Trussed Concrete Beams (HSTCBs) and the columns are classical RC pillars. An innovative solution, recently patented, has been found for the mitigation of the effects of seismic cyclic actions on small-sized beam-column joints, typically characterised by a large amount of longitudinal reinforcement due to the small effective depth of the beam. This paper collects the main featuring steps of the innovative research, which has led to the patented solution. The calculation procedure for designing the proposed connection is shown, and the validation through 3D finite element modelling is described. For the structural analysis of the joint, several monotonic and cyclic simulations have been carried out with the scope of investigating different design moment values. The finite element results proved that the patented solution is effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by a flexural behaviour dominated by wide and stable hysteresis loops.

The use of Fabric Reinforced Cementitious Matrix (FRCM) composites for structural retrofit has seen an increased interest among the scientific community, during the last decade. Various studies have revealed their effectiveness as external retrofitting technique of masonry elements, offering numerous advantages respect to the well know Fibre Reinforced Polymer (FRP) in terms of compatibility with masonry support, reversibility of intervention and sustainability. Despite the growing use, the characterization of FRCM mechanical behaviour is still an open issue, due to numerous uncertainties involved in test set-up adopted and fibre-mortar combination. The proposed experimental study aims to investigate the tensile and shear bond behaviour of Basalt-FRCM for strengthening calcarenite masonry elements. Calcarenite is a natural stone with sedimentary origin and it is widely present in existing buildings of the Mediterranean areas. Direct tensile tests are performed on two types of Basalt-FRCM coupons, with cement-based and lime-based mortar, adopting two different test-set-up based on clamping and clevis grip methods. Moreover, double shear bond tests are carried out to evaluate the adhesion properties of the two types of Basalt-FRCM with calcarenite support. Experimental outcomes are compared in terms of stress-strain curves, evaluating the influence of mortar grade and test set-up on the mechanical performances of Basalt-FRCM composites. The comparisons provide information about the mechanical stress transfer phenomena that occur at the fibre-to-matrix and FRCM-to-substrate interface level and the failure modes.

Low-damage design of structures in seismic-prone areas is becoming an efficient strategy to obtain "earthquake-proof" buildings, i.e. buildings that, even in the case of severe seismic actions, experience a low or negligible amount of damage. Besides the safeguard of human lives, this design strategy aims also to limit the downtime of buildings, which represents a significant source of economic loss, and to ensure an immediate occupancy in the aftermath of an earthquake. In this context, focusing on moment-resisting frames (MRFs), several solutions have been developed for the beam-to-column connections (BCCs) of steel and precast/prestressed concrete structures, but very few for cast-in-situ reinforced concrete (RC) structures. This paper focuses on a recently-proposed friction-based BCC for MRFs made with hybrid steel-trussed concrete beams (HSTCBs). The latter are made by a spatial lattice built using V-shaped rebars and a steel bottom plate, which eases the introduction of a friction dissipative device. HSTCBs are usually characterized by a small effective depth, which leads to a large amount of longitudinal rebars. The latter, together with a small-sized beam-column joint, make it potentially subjected to severe damage, which reduces its dissipative capacity. The shear force acting on the joint can be reduced by endowing the BCC with a friction device, with the aim of increasing the lever arm of the bending moment transferred between beam and joint, preventing the latter from damage. To evaluate the mechanical performance of the above connection, two experimental programs have been carried out at the Structures Laboratory of the University of Palermo. The first one focused on the characterization of the friction properties of two different materials (thermal sprayed aluminum and brass), by means of a linear dissipative device subjected to cyclic load. The second one tested a beam-to-column subassembly endowed with the recently-proposed connection in which the dissipative device was made with the best performing friction material tested before. The results of the cyclic tests are presented and commented, showing the promising performance of such connection in providing a low-damage behavior and a satisfactory dissipative capacity.

The structural assessment of existing historical structures is a complex task due to the inner main difficulty in making up reliable models for structural analysis, able to include mechanical and geometrical nonlinearities, existing damage, complex configurations and arrangements of materials. This task becomes more difficult in mixed RC-masonry structures, which structural modelling can be particularly tough due to the different connections and interactions between structural members and materials. This paper presents the case study of a multi-storey mixed Reinforced Concrete (RC)- masonry historical structure, namely the former mill “Molino-Pastificio Soresi” building, located in Partinico (Sicily—Italy). It is shown as it is possible to obtain an accurate and detailed representation of the building, as well as a reliable structural model. The assessment of the seismic vulnerability from the global point of view of the considered case study is carried out through a multidisciplinary approach based on four stages: (1) historic analysis and study of the relevance of the building; (2) geometrical survey and photographic documentation; (3) structural identification and materials; (4) BIM implementation and structural modelling.

Fabric Reinforced Cementitious Matrix (FRCM) materials are increasingly common for strengthening existing masonry structures. Their popularity is due to their many advantages with respect to resin-based composites, especially when applied to stone supports. The constitutive behaviour of FRCM materials is defined by the combination of their tensile response and the bond behaviour with the masonry support, both depending on complex stress transfer mechanisms between matrix and fabric, especially in the post-cracking stage. This paper presents a numerical study which aims to predict the mechanical behaviour of FRCM systems through simple 2D models of truss elements and non-linear springs to simulate the fabric-to-matrix and composite-to-substrate interaction. The comparisons between results of numerical approach and experimental responses showing that the proposed methodology is an effective and easy tool to predict the mechanical behaviour of FRCM composites.

This paper presents a critical review of the most established analytical models for the prediction of the compressive strength of FRP and FRCM-confined masonry columns. In particular, two types of fibres are analysed, i.e. glass and basalt. A wide dataset available in the literature is used for the application of the analytical models and for the development of parametric analyses useful for the critical comparison of FRP vs. FRCM confinement technique and glass vs. basalt fibres to be adopted as reinforcement of masonry substrate. The effects of stiffness and strength of the reinforcement, the number of reinforcing layers, the compressive strength of masonry and the cross-section shape are investigated.

In recent decades, many concrete bridges, built in the 60s and 70s of the 20th Century with a Gerber-girder scheme, show severe damage of the saddles due to concrete degradation and reinforcement corrosion. On the basis of the recent Ministerial Guidelines for the assessment of existing bridges, it is necessary to evaluate the state of the Gerber saddles in a large number of bridges on both main and secondary roads. To do this, it is necessary to apply flexible assessment procedures that can be adapted to several situations and that allow a speedy assessment of the intervention priorities. The methodologies of intervention represent the crucial point for a rapid rehabilitation of these infrastructures. In this paper, on the basis of some case-studies, assessment and strengthen-ing methodologies are proposed that can be applied to different real cases, in consideration of the budget available, with the aim of drafting an operative list of priorities and improving as many bridges as possible, currently in service

Many existing reinforced concrete bridges exhibit behaviour at the Service Limit State and the Ultimate Limit State which can be considered unsatisfactory with respect to the current provisions of Codes, but which are actually deficiencies deriving from obsolete calculation methods, structure age, material degradation, diffuse or localized corrosion and increased loads. Among these, cantilever bridges with half-joints may present a decrease in global safety coefficients for the most stressed current sections of the deck or in the local ones, that affect the performance of elements sensitive to degradation, such as Gerber saddles. In these cases, simple strengthening interventions through external prestressing that reduce the tensile stress in concrete areas subject to cracking, as well as the deformability of the points that have accumulated displacements over time (due to creep or degradation), can often be implemented without the need to recourse to interventions of greater impact, obtaining an improvement in the structural behaviour or a variation of the static scheme that improves the overall performance. This is the case of a concrete Niagara-type cantilever bridge with half-joints, designed and built in the 60s in southern Italy by Riccardo Morandi, presented here as a case-study, which does not show a very high or widespread state of decay but rather a slight insufficiency of some elements, in particular related to the cantilever bridge behaviour. A methodology is proposed for the safety assessment of these bridges and a solution for improving performance through minimal rehabilitation interventions with the introduction of external prestressing. The results of the analysis in the present state, the deficiencies found as well as the possible level of increase in the safety coefficients at ULS with the proposed intervention are presented.

Segmental bridges built by cantilevering with in-situ casting in the ‘60s-‘80s of the XX Century present a central hinge on the main span or a central simply supported span between the two cantilevers (drop-in span). Due to time-dependent phenomena like creep of concrete and to unexpected loss of prestressing, several bridges of this typology show an abnormal deflection at hinges causing discomfort of traffic as well as insufficiencies of checks at Service and Ultimate Limit States. Moreover, these bridges are today at the end of their nominal service life, impacting significantly on Italian road network. A methodology for retrofitting these bridges by partial recovering of deflection and overall strengthening is proposed through the application of additional prestressing, especially in segmental bridges with variable box cross-section. The proposed solution supplies a global rehabilitation strategy aiming to improve the performance of the bridge, providing robustness and increasing of the service life.

Fabric Reinforced Cementitious Matrix (FRCM) composites are widely seen as offering advantages in structural retrofitting of existing buildings. In spite of their reputed effectiveness, FRCM systems typically suffers from several drawbacks related to the mechanical characterization due to complex stress transfer mechanicisms that can develop at fiber-matrix and FRCM-substrate interface. Numerous experimental studies focus on this topic, but few numerical studies are addressed to better understand the variables involved in the problem. This paper aims to propose a simple 1D numerical model to predict the shear bond behaviour of FRCM applied on concrete substrate, providing support to deduce reliable criteria for design procedures.

Internal prestressing with bonded tendons suffers corrosion of wires and bond deterioration due to the bad infill of grouted sheaths. Many bridge girders show this state through cracking, deflections and in the worst cases, sudden failures. In Italy these are common situations, and the internal tendon corrosion is among the major causes of bridge degradation and damage, especially for grouted post-tensioned tendons. This paper presents the analysis of failure of prestressed cross-sections considering shear and flexure in the case of bond deterioration due to corrosion of internal post-tensioned tendons. The structural behaviour is analysed for different typologies of bridge deck composed of prestressed beams with bonded tendons. The rate of corrosion is correlated to the bond deterioration and the consequences on the ultimate shear-flexure domains are discussed, giving indications to the engineer on the assessment of existing damaged bridges for safety evaluations

The performance of cantilever reinforced concrete bridges is fundamental topic in assessment and retrofit of Italian infrastructures, because the static scheme of the so-called “Gerber bridges” was very popular between 50’s and 70’s of XX Century. Many of them present severe damage due to the drainage of the deck waters inside the joint and to the consequent degradation of Gerber saddles. Furthermore, the state of corrosion of the reinforcements together with the actual degree of freedom of internal constraints, often partially blocked due to degradation and subsequent maintenance over time, modify the structural behaviour and the performance both in terms of service and ultimate limit states. This paper presents a case study of a reinforced concrete bridge with a three-span cantilever scheme, designed in southern Italy by Riccardo Morandi, in which this problem led to a difficult assessment of the actual performance of the bridge. The on-site static and dynamic investigations and the bridge modelling in its current condition, taking into account the effects of degradation in the Gerber saddles, made it possible to evaluate the state of the bridge after more than 60 years from construction

Fibre Reinforced Cementitious Matrix (FRCM) composites have been proved to be a suitable strengthening material for masonry structures in the last years. Moreover, basalt fibres are increasingly used as reinforcement of composites as a more sustainable alternative to glass fibres. The goal of this work is to investigate the effectiveness of basalt FRCM to confine masonry circular columns. A total of eighteen clay brick masonry cylinders were tested in compression. The specimens were cored from two different masonry assemblies and wrapped with one or two layers of BFRCM composite. The stress-strain curves and the gains of strength and strain capacity of confined cylinders compared to the control specimens are reported together with a description of the failure modes.

On Italian roads, a lot of reinforced concrete bridges were built in the 1950’s and 1960’s for short spans, before the advent of prefabricated structures. Many of these bridges, sited on principal or secondary roadways, show the effects of corrosion of reinforcements and high levels of damage, leading to the likelihood of achievement of the Ultimate Limit State, below the required performances of serviceability, especially in the case of Gerber saddles having strongly corroded reinforcements. Different case studies of bridges sited in Southern Italy (Sicily) are shown, allowing engineers to classify the main effects of damage in corroded structures with the Gerber static scheme (cantilever girder bridges), for a first application of the new Italian Bridge Assessment and Maintenance Guidelines. The case studies are illustrated, and the structural implications are discussed, providing indications for treating the common cases of bridges with Gerber saddles

Aiming at evaluating the seismic vulnerability of the old town of Caltabellotta, first the main characteristics of the new survey cards CARTIS for the structural typology characterization recently developed, and the bases of the macroseismic method for seismic vulnerability and fragility curve estimation, are briefly summarized. Then, the main typological and structural characteristics of the house typology in the historic centre of Caltabellotta are described, providing a synthetic estimate of the vulnerability and highlighting the probability of reaching predetermined levels of damage in relation to the intensity of the expected earthquake (fragility curves). This information, combined with the seismic hazard maps of the territory made available by the New Technical Construction Standards, allow to present damage distribution scenarios. Finally, the results of the prediction of exposure and seismic vulnerability for the houses in the historic centre of Caltabellotta are compared, obtained with databases of different levels of accuracy. In particular, the results obtained on the basis of the estimation of the characteristics and the distribution of the typologies derived from the use of the CARTIS cards at sector scale are compared, also highlighting the degree of reliability of the results obtained on the basis of interviews with several technicians operating in the area, with those obtained through an expeditious survey from the outside of the construction features on a house scale.

In the last thirty years, Hybrid Steel-Trussed Concrete Beams (HSTCBs) have been widely used in civil and industrial constructions and, therefore, their mechanical performance must be evaluated with the aim of guaranteeing adequate dissipation of the seismic energy particularly in the beam-to-column joints. However, one of the most frequent peculiarities of HSTCBs is that of using their own steel joist to cover large spans with reduced depth and, in the case of traditional beam-to-column connections, this requires large amount of steel reinforcement inside the panel zone, often made with large diameter rebars. These characteristics make both the panel zone and the beam end potentially vulnerable to the effects of the cyclic actions induced by the earthquake and dramatically reduce the dissipative capacity of the entire structure. For this purpose, this study investigates the possibility of introducing friction damper devices in the HSTCB-to-column joint of framed structures in seismic areas. The use of friction dampers prevents damage to the structural elements, improves the expected performance and limits damage to the panel zone. The feasibility study is conducted through the development of design criteria for the dimensioning of the device and numerical validation of the proposed solution.

In this work a feasibility study on the use of friction devices within beam-to-column joints of RC structures is conducted. The connection is made between RC columns cast in-situ and semi-prefabricated steel-concrete beams, named Hybrid Steel-Trussed-Concrete Beams (HSTCBs). Nowadays, HSTCBs are widely adopted in civil and industrial buildings and, therefore, it is required to evaluate their compliance with the capacity design criteria and their seismic energy dissipation capability. However, the design of the reinforcement of such beams usually lead to the adoption of large amount of steel within the panel zone which becomes potentially vulnerable to the effects of seismic cyclic actions and dramatically reduce the dissipation capacity of the entire structure. Therefore, the introduction of friction dampers in the HSTCB-to-column joints is investigated in order to evaluate the ability of the device in preventing the main structural elements from damage and limiting the cracking of the panel zone, thanks to the increase of the bending moment lever arm, which reduces the shear forces in the joint. The feasibility study is firstly conducted through the development of design criteria for the pre-dimensioning of the device and, successively, the proposed solution is validated through the generation of finite element models.

The aim of this work is to compare the seismic response of RC frames built using Hybrid Steel-Trussed Concrete Beams (HSTCBs) whether or not equipped with friction damper devices installed at the beam-to-column joints. Due to their small depth-to-span ratios, HSTCBs usually lead to a large amount of rebar within the beam-column joint, potentially reducing its cyclic performance. Therefore, the adoption of a friction system at the beam-tocolumn joint provides two main advantages, i.e. limiting the shear forces, and thus the potential damage, in the panel zone thanks to the increasing of the bending moment lever arm, and assigning to the device the task of dissipating the incoming seismic energy, thus preventing damage to the end sections of the beams. The seismic response of traditional and innovative r.c. frames is computed by means of non-linear time history analysis, taking into account the degrading phenomena, both in terms of stiffness and strength, which are observed in beam-column joints when subjected to cyclic actions. The cyclic behaviour of the beam-column joint of the traditional frame is tuned on the results of cyclic test on a full scale beam-column joint subassembly. The results highlight that RC frame endowed with friction devices provide structural performance consistent with design forecasts, i.e. beam end sections with a nearly-elastic behaviour, panel zones which experience negligible level of damage, comparable values of both maximum interstorey drift ratio and amount of energy dissipated with respect to traditional frame.

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.

The hybrid steel trussed concrete beams represent a structural solution widely adopted in the industrial constructions thanks to the numerous advantages due to their use, such as economic convenience, high performances and constructional speed de-riving from the partial prefabrication process and from the self load-carrying capacity of the beam in the first operative phase, prior to the in-site casting of concrete. The hybrid steel trussed concrete beams examined in the present study are constituted by two prin-cipal components, i.e. a steel joist with inclined rebars, realized in industry, which is welded to a smooth steel plate and then embed-ded within the concrete material cast in situ. The proposed study concerns the modeling of the shear behavior of these beams provid-ing a synthesis of the most relevant scientific contributions currently available in the technical literature regarding both analytical and numerical models for the prediction of the shear resistance of the beam.

An experimental campaign of three-point bending tests on specimens of Hybrid Steel Trussed Concrete Beams (HSTCBs) is presented. The scope of the experiments is the evaluation of the shear strength in the structural typology object of study. Two series of specimens are tested, subjected to positive and negative bending moment, respectively, with the aim to reproduce, in the first case, the condition in the midspan of a beam belonging to a framed structure and, in the second case, the behavior of the beam next to the column where the sign of the bending moment is reversed. The obtained experimental results are interpreted by means of an analytical model for the prediction of the shear resistance, taking into account the peculiarities of the tested beams typology.

Results of experimental investigation on cyclic behavior of beam-column joints made up of hybrid steel trussed concrete beams connected to reinforced concrete columns are presented. Specimens are representative of joints in framed structures subjected to seismic actions designed according to current Italian technical standard codes. The aim of the experimental testing was to verify strength capacity and ductility of the connection, focusing both the global behavior and the force transmission mechanisms between steel truss and concrete in the region close to the beam-column joint.

The model for the evaluation of shear resistance of reinforced concrete member provided with transverse web reinforcement, derived by Nielsen (1999) on the basis of the variable inclination stress field approach, is generalized here to predict the shear strength of r.c. beams equipped with two sets of differently-inclined transversal web reinforcement and longitudinal skin reinforcement. Numerical analyses emphasize the efficiency of double inclined web transverse reinforcement in providing shear strength to beams.

Si indaga sul comportamento sismico di travi prefabbricate reticolari miste, non autoportanti in prima fase, nelle quali il traliccio prefabbricato è costituito da un piatto inferiore di acciaio tipo S355, ed un corrente superiore realizzato con barre di acciaio da cemento armato di tipo B450C, collegate da un anima costituita da barre sagomate a V rovescia inclinate. Vengono mostrati i risultati di una prova a flessione su tre punti su un campione rappresentativo di una coppia di travi convergenti a un nodo, collegate ad un pilastro in c.a. con connessione gettata in opera. La prova è stata condotta con più cicli di carico a momento positivo, di cui uno di grande ampiezza e uno successivo a momento negativo fino a rottura. L’impiego di estensimetri disposti sugli elementi del traliccio metallico e sulle barre di armatura di continuità al nodo, prima della realizzazione del getto di completamento di calcestruzzo, ha permesso di rilevare con accuratezza i contributi di resistenza e rigidezza forniti nelle sezioni sede di formazione della cerniera plastica. I risultati sperimentali vengono interpretati mediante un modello a fibre a plasticità diffusa adottando una discretizzazione in grado di cogliere l’ampiezza della cerniera plastica e di evidenziare la sezione a partire dalla quale il piatto metallico è in grado di fornire contributi resistenti.

Composite materials have been widely used for strengthening weak masonry buildings. Particularly, wrapping with fibre reinforced polymer (FRP) composites has become a common method for strengthening masonry members primarily subjected to compressive static loads or seismic actions. More recently, in an effort to alleviate some drawbacks associated with the use of FRP materials, fibrereinforced cementitious matrix (FRCM) composites have received a lot of interests for external strengthening of historical masonry structures. It is used as an alternative to FRP in situations where these composites have shown some disadvantages or their use is banned. This paper presents a literature review on the mechanical characterisations of FRCM composites for structural retrofitting. Recent experimental results of tensile and bond tests are discussed, highlighting the roles of the different parameters affecting the mechanical performance, e.g. type of fibre, clamping method. This review aims to form the base for a new experimental investigation on the compressive behaviour of FRCM and FRP wrapped masonry specimens.

The use of composite materials for retrofitting of masonry structures has received great attention during the last two decades. For masonry buildings there are several advantages in using composite materials. Traditional techniques that were largely used and investigated in the past, may be inadequate in seismic areas where the added mass could increase seismic actions. Moreover, for historical and architectural heritage structures, the compatibility, sustainability and reversibility of the intervention is a key factor for the selection of the most appropriate strengthening system. Many investigations have shown that fibre reinforced polymers (FRP) can be effectively used to induce a passive confinement action on masonry columns and improve the axial capacity and ductility of the structural members. This paper presents the results of an experimental study on the compressive behaviour of clay brick masonry cylinders reinforced with basalt fibre reinforced polymer (BFRP) grids. The main aim of this study is to assess the effectiveness of the BFRP wraps on the strength and ductility of masonry columns. Twelve clay brick masonry cylinders, cored from masonry walls and columns, were reinforced using either one or two layers of BFRP grids. Two different arrangements were used for producing the cylinders in order to investigate the effect of vertical joints on the response of masonry cylinders. The basalt grid had a cell size of 6x6 mm. After a preliminary experimental study aimed at characterizing the mechanical properties of bricks, mortar and basalt grid, the cylinders were tested under uniaxial compression loading. The test results showed a strength increase between 30% and 38% for cylinders wrapped with one layer and between 69% and 71% for those wrapped with two layers of BFRP grids.

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.

Many historical cities enjoy the presence of masonry buildings with inestimable historical, artistic and cultural value. Old masonry buildings often suffer structural deficiencies, design faults and materials aging process. In recent years, many researchers focused their attention on the opportunities that structural health monitoring (SHM) can ensure for the health state of existing masonry structures, where damage can be difficult to be promptly predicted, pontentially causing abrupt collapses, with high risks for the community. This paper presents an experimental study on the effectiveness of two types of stress sensor for SHM of new masonry elements. Ceramic piezoelectric sensors and capacitive sensors were installed in mortar joints of two series of specimens made of calcarenite stone masonry and clay brick masonry. All specimens were tested under uniaxial compression with displacement control, to assess the effectiveness of sensors in recording pressure variation within the different types of masonry and therefore testing their potential use for SHM applications. Even though both the ceramic and capacitive sensors were designed as stress sensors for concrete structures, their installation within mortar joints provided a good response, based on the comparison with standard measurement devices. Results demonstrate the suitability of the sensors even for SHM of masonry structures.

The lack of maintenance of roadway concrete bridges built from the Second World War until the 70 s of the 20th century has led in recent years to an ever-increasing request for safety assessments. When bridge performance in terms of Serviceability Limit State (SLS) and Ultimate Limit State (ULS) has to be evaluated, in-situ visual inspections and load tests for safety and maintenance assessment have to be coupled with structural analysis. In order to identify a sound bridge structural model and to assess the actual conservation state, more refined models than those usually considered for section and reinforcement design should be used to reproduce the results of load tests and perform global and local safety checks in the structural elements. These needs are exemplified here through an assessment of the performance at SLS and ULS of a three-span cantilever reinforced bridge designed by Riccardo Morandi in Southern Italy. The central beam between the cantilevers is prestressed with bonded tendons while the side spans are made of ordinary reinforced concrete. Critical aspects of the bridge behaviour together with deficiencies due to deterioration and lack of maintenance over time, in service life, are investigated. The results of a structural assessment performed with Finite Element models are presented, through a comparison between different approaches and grades of structural analysis and through validation with in-situ investigations. Safety assessment of the half-joint is focused comparing the results obtained from strut-and-tie models supplied by Eurocodes and specifically developed for the case-study, considering the actual arrangement of the Gerber saddle. The results of this study show that a safety assessment of half-joints based on the literature and code models can lead to unreliable evaluations and that only global and local FE models validated through in-situ investigations allow the engineer to perform a reliable evaluation of safety in existing bridges.

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of FRCM strengthening systems, however a simple and reliable procedure is still missing. In this paper, two simplified numerical models are proposed to simulate the tensile and shear bond behavior of FRCM composites. Both models take advantage of truss and non-linear spring elements to simulate the material components and the interface. The proposed approach enables us to deduce the global mechanical response in terms of stress-strain or stress-slip relations. The accuracy of the proposed models is validated against the experimental benchmarks available in the literature.