1,720,982 research outputs found
Analytical model based on artificial neural network for masonry shear walls strengthened with FRM systems
No full textIn the future Fiber Reinforced Polymer (FRP) materials will be considered a common strengthening
system for civil structures thanks to several research efforts made in the last decades. For those applications
in which FRP materials show some restrictions such as, above all, the incompatibility with
heritage buildings, a new generation of fibrous materials has been developed. Researchers have investigated
Fiber Reinforced Mortars (FRM) as external structural and seismic reinforcement. One of the most
attractive applications of these materials is related to the in-plane shear strength of masonry walls.
In this scenario, an analytical model based on Artificial Neural Network (ANN) is proposed and discussed
in respect of the geometrical and mechanical variables that control the mechanical problem. An
ANN is presented in the paper by showing its possible productive application in the civil engineering
field. The proposed model seems able to predict the shear strength of FRM strengthened masonry; the
approach is considered efficient since it includes both a theoretical method and a large test calibration,
illustrated herein. Thanks to a quite small input database of laboratory results, ANN seems able to
provide a theoretical solution to the problem with accuracy and precision
Unified model for hollow columns externally confined by FRP
No full textNowadays, the employment of Fibre Reinforced Polymer (FRP) composites in civil engineering field has
been successfully experienced. Different potential applications of solid concrete-filled FRP tubes are
exploitable in marine piles, overhead sign structures, poles and posts, bridge columns and piers, girders,
large pipes and tunnels (mainly circular cross-section). This technique is also used for the confinement of
masonry columns, typically encountered in monuments and historical buildings (both rectangular and
circular cross-section); hence the need of providing formulas for the design of an appropriate strengthening.
Several analytical models are available in the scientific literature for assessing the increase of
strength and ductility of concrete or stone solid elements externally confined with FRP or for hollow columns
internally steal enclosed and externally FRP-confined but, there is still a lack of research about hollow
columns only externally confined. The presence of an empty core implies a different stress state in
the inner cylindrical surface with respect to the outer one. Inwards deformations are more significant
and this behaviour is not taken into account by available models.
The present study aims to illustrate a detailed summary of the existing analytical models and to provide
a unified procedure for concrete and masonry hollow columns valid for both circular and square
cross-sections. An iterative method that updates the geometrical parameters according to step-by-step
uniaxial compressed column is shown in order to capture the real deforming behaviour of the compressed
solid. This analytical approach has two important implications: the first is the ability of calculating
the stress state of the column and of the external FRP reinforcement at each step; the second is that of
theorizing a procedure, which is independent on the type of material used for the column. The outputs of
the proposed method are then compared with experimental results currently available in the scientific
literature. A good matching is obtained between the available experimental results and the analytical
predictions in term of axial stress–strain curves
DIAGONAL COMPRESSION TESTING OF TUFF MASONRY PANELS STRENGTHENED WITH INORGANIC-BASED SYSTEM: AN EXPERIMENTAL INVESTIGATION
No full textA significant portion of the structures around the world is made of clay- and tuff-based masonry. These structures are very vulnerable against earthquakes, so their seismic performances need to be improved. In the last two decades, the Fabric Reinforced Cementitious Matrix (FRCM) system was largely used for strengthening of historical masonry structures in alternative for the fiber-reinforced polymer (FRP). In the FRCM-category there is now a composite that includes steel fabric with within an inorganic matrix, namely the Steel Reinforced Grout (SRG). The herein reported experimental campaign was focused on a set of seven small square masonry walls (410x410mm and a thickness of 130 mm) with
SRG-retrofitting, while an unreinforced masonry (SC) wall was tested as a control specimen, all the specimens were tested under diagonal compression load. The investigated parameters were the type of reinforcement (FRCM and SRG) and the number of fabric layers (from 1 to 3 layers)
REHABEND 2016 Euro-American Congress - “Construction Pathology, Rehabilitation Technology and Heritage Management"
No full textInnovative materials such as Fiber Reinforced Polymer (FRP) have been widely used for the seismic upgrade and reparation for a couple of decades. This testifies the effectiveness of such techniques, especially when they apply to vulnerable masonry structures. In this study, the seismic upgrade of a large building, used as a theatre in the south of Italy, is illustrated. After a seismic analysis based on the study of the collapse mechanisms of the masonry walls, a strengthening program was individuated and successfully applied in-situ. The analysis was conducted with reference to the local mechanisms that can be activated by the seismic acceleration in the considered site. The kinematic analysis was performed as linear and non-linear. In the first case, the control parameter is represented by the minimum value of the seismic acceleration that can be supported by the excited sub-structure. When a non-linear analysis is implemented, the controlling parameter is the maximum displacement that guarantees the ultimate equilibrium configuration. It will be shown how the linear analysis may be more conservative with respect the non-linear one. Once the seismic vulnerability was quantified in terms of acceleration and displacement, an innovative strengthening system was designed. The seismic upgrade was evaluated by the comparison with respect the un-reinforced state of the construction. In order to avoid out of plain failure mechanisms, an active confinement was designed by using pre-tensioned carbon-aramid fiber wires, anchored trough steel plates to the masonry substrate. Four tensioned CFRP-AFRP (Carbon FRP – Aramid FRP) wires were placed along three sides of the building at different levels; each of them had a length of about 40 meters. The installation of the wires, the anchoring system and the tensioning procedure will be illustrated in the paper. The choice of composite materials allowed this type of innovative technique, by guaranteeing a high durability, speed of installation and safe operations in elevation. The conclusions will show how the designed strengthening technique is able to preserve the stability of the structure and improve its performance in case of seismic events, with no impact on the architectural aesthetics of the building. The intervention can also be considered removable according to the ISCARSAH’s recommendation
FRCM-confined masonry columns: experimental investigation on the effect of the inorganic matrix properties
No full textNowadays, the strengthening and the retrofitting are crucial issues in the civil engineering challenge for structural conservation. Innovative techniques, using fiber reinforced polymers (FRPs) composites, have been proven to be very effective in a wide range of applications. However, the organic matrix appears to be inadequate because of its difficult reversibility, especially when referring to historical masonry buildings. In this perspective, a new generation of strengthening systems has been studied, known as fabric reinforced cementitious matrices (FRCMs). They generally consist in a dry fabric-based reinforcement (typically an open-grid or a textile) embedded in an inorganic matrix. The present paper reports and analyses the experimental results on FRCM-confined masonry columns subjected to centred compression test. The main goal of this research consists in evaluating the role of the inorganic matrix in determining the effectiveness of FRCM-confinement. For this purpose, three different inorganic matrices, having different compressive strength, have been considered and used for confining a poor-quality masonry column. The different increases of the axial strength, due to the differences of the compressive strength of the matrices of the FRCM-system, have been assessed. Finally, the experimental results have been compared with the theoretical predictions obtained from the application of an analytical model, available in the literature
Open issue for confinament of masonry colun with frcmsystem: Theoretical and experimental investigation
No full textThe Fabric Reinforced Cementitious Matrices (FRCMs) are promising solution for the confinement of masonry column because they demonstrated strengthening effectiveness and, at the same time, compatibility with historical substrates. Nevertheless, the matrix is responsible of the stress-transfer from the structural element to the fabric-reinforcement. So, in case of poor-quality mortar, the effectiveness of the strengthening can be limited or even compromised. For this reason, few studies have been targeted to this aspect in the recent past; while theoretical studies are still limited.
The present paper refers to the results of an experimental and analytical investigation on FRCM confined clay brick masonry. A series of small-scale masonry columns were tested under monotonic centred load until collapse. The varied parameters were: the number of confining layers (i.e. 1, 2 and 3) and the confinement configuration (i.e. continuous and discontinuous).
The aim of the research consists of strengthening the knowledge in the field of FRCM-confinement in order to provide a contribution in developing accurate analytical design-oriented formulas. At this scope, some analytical models, available in the technical literature and proposed for national Guide Lines, were also adopted for predicting the herein reported experimental results. The outcomes evidenced that the number of FRCM-layers is a crucial parameter for the accuracy of the forecasts
Seismic upgrade of masonry buildings by using innovative active FRP-Technique
No full textInnovative materials such as Fiber Reinforced Polymer (FRP) have been widely used for the seismic upgrade and reparation for a couple of decades. This testifies the effectiveness of such techniques, especially when they apply to vulnerable masonry structures. In this study, the seismic upgrade of a large building, used as a theatre in the south of Italy, is illustrated. After a seismic analysis based on the study of the collapse mechanisms of the masonry walls, a strengthening program was individuated and successfully applied in-situ. The analysis was conducted with reference to the local mechanisms that can be activated by the seismic acceleration in the considered site. The kinematic analysis was performed as linear and non-linear. In the first case, the control parameter is represented by the minimum value of the seismic acceleration that can be supported by the excited sub-structure. When a non-linear analysis is implemented, the controlling parameter is the maximum displacement that guarantees the ultimate equilibrium configuration. It will be shown how the linear analysis may be more conservative with respect the non-linear one. Once the seismic vulnerability was quantified in terms of acceleration and displacement, an innovative strengthening system was designed. The seismic upgrade was evaluated by the comparison with respect the un-reinforced state of the construction. In order to avoid out of plain failure mechanisms, an active confinement was designed by using pre-tensioned carbon-aramid fiber wires, anchored trough steel plates to the masonry substrate. Four tensioned CFRP-AFRP (Carbon FRP – Aramid FRP) wires were placed along three sides of the building at different levels; each of them had a length of about 40 meters. The installation of the wires, the anchoring system and the tensioning procedure will be illustrated in the paper. The choice of composite materials allowed this type of innovative technique, by guaranteeing a high durability, speed of installation and safe operations in elevation. The conclusions will show how the designed strengthening technique is able to preserve the stability of the structure and improve its performance in case of seismic events, with no impact on the architectural aesthetics of the building. The intervention can also be considered removable according to the ISCARSAH’s recommendations
Modeling of Steel-Reinforced Grout Composite System-To-Concrete Bond Capacity Using Artificial Neural Networks
No full textRemovable/Reversible Solutions for the FRP-Confinement of Historical Masonry Columns
No full textThe retrofitting of historical masonry is often limited by strict rules of reversibility and aesthetical impacts. In this scenario, the use of fibers reinforced polymers (FRPs) is generally forbidden because of the epoxy-based matrix is glued on the substrate, even if their effectiveness is largely proved. Since the reversibility of the intervention is one of the most relevant aspects in the field of cultural Heritage, further research aiming to the optimal compromise between safety and conservation is still needed. The present research aims to experimentally demonstrate two methods oriented to the removability of the FRP-confinement of masonry columns. The first consists of a liquid adhesion-inhibitor applied by brush before the hand lay-up installation of the FRP-wrapping. Alternatively, a MylarTM layer placed between the substrate and the FRP-jacket was experienced to fully-eliminate the bond between jackets and core substrate. Pure compression tests were performed in order to check the mechanical effectiveness of the proposed techniques. After testing the FRP-jacket was removed in order to observe the substrate conditions in terms of detachment of material and/or discoloration. The main results are herein discussed demonstrating the validity of the proposals for two different types of masonry (i.e. tuff and limestone)
Open issue for confinament of masonry colun with frcmsystem: Theoretical and experimental investigation
No full textThe Fabric Reinforced Cementitious Matrices (FRCMs) are promising solution for the confinement of masonry column because they demonstrated strengthening effectiveness and, at the same time, compatibility with historical substrates. Nevertheless, the matrix is responsible of the stress-transfer from the structural element to the fabric-reinforcement. So, in case of poor-quality mortar, the effectiveness of the strengthening can be limited or even compromised. For this reason, few studies have been targeted to this aspect in the recent past; while theoretical studies are still limited. The present paper refers to the results of an experimental and analytical investigation on FRCM confined clay brick masonry. A series of small-scale masonry columns were tested under monotonic centred load until collapse. The varied parameters were: the number of confining layers (i.e. 1, 2 and 3) and the confinement configuration (i.e. continuous and discontinuous). The aim of the research consists of strengthening the knowledge in the field of FRCM-confinement in order to provide a contribution in developing accurate analytical design-oriented formulas. At this scope, some analytical models, available in the technical literature and proposed for national Guide Lines, were also adopted for predicting the herein reported experimental results. The outcomes evidenced that the number of FRCM-layers is a crucial parameter for the accuracy of the forecasts
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