1,721,141 research outputs found
Cyclic behavior of FRP-wrapped columns under axial and flexural loadings
No full textThe behavior of r.c. columns wrapped by composite material sheets (FRP) under axial force and cyclic bending is studied. Cyclic constitutive laws for confined and unconfined concrete in compression, for concrete under tension and for steel reinforcing bars are introduced. Numerical results are in good agreement with experimental tests. Hysteretic dissipated energy for cyclic bending is also estimated. Wrapping with FRP is shown to be very effective, increasing significantly ductility of columns under bending
Erratum: Assessment of a bond strength model for FRP reinforcement externally bonded over masonry blocks (Compos. Part B: Eng. (2014) 61 (147-161) DOI: 10.1016/j.compositesb.2014.01.028)
No full text[No abstract available
Un'indagine sperimentale sull'aderenza placca-calcestruzzo nel rinforzo di elementi strutturali con materiali compositi
No full textNella presente memoria vengono descritti i risultati di una campagna sperimentale rivolta allo studio della delaminazione tra calcestruzzo
e placche in materiale composito. Sono state condotte prove di trazione su placche in fibra di carbonio incollate su prismi in
calcestruzzo. A partire dai valori di deformazione rilevate mediante estensimetri disposti lungo la placca, è stata ricavata la tensione
tangenziale media tra due successivi punti di misura e il corrispondente scorrimento placca-calcestruzzo. Questi dati sono stati utilizzati
per calibrare una legge di interfaccia non lineare. I risultati sono risultati in buon accordo con quelli ottenuti mediante un modell
Destructive and minor destructive tests on masonry buildings: Experimental results and comparison between shear failure criteria
No full textIn this paper, an extensive experimental campaign conducted on existing masonry buildings is presented. The main objective of this activity was to study the shear behaviour of masonries constituted by clay bricks and lime-based mortar evaluating the most suitable techniques applicable to get reliable information on the material mechanical properties. Minor destructive tests (MDT) and destructive tests (DT) were performed on eight masonry buildings, damaged by the 2012 Emilia earthquake (Italy). The tests results are here presented and discussed, focusing on the strength parameters obtainable from each test type and on the definition of appropriate failure domains. The strength predictions are finally compared with the outcomes of full-scale destructive tests
Experimental Study on Masonry Panels Strengthened by GFRP: The Role of Inclination between Mortar Joints and GFRP Sheets
No full textFor the shear strengthening of masonry walls, different configurations for FRP sheets are currently used in real application, such as vertical, horizontal or diagonal strips. In the last configuration the FRP sheet is inclined with respect to the direction of mortar joints. In the experimental campaign presented in this paper, it is investigated whether the FRP-masonry bond could be affected by this inclination. In order to analyze this issue, three different typologies of masonry panels (with
different textures) retrofitted by FRP sheets, inclined of 45 degrees with respect to the vertical axis of the specimen, are subjected to single-lap shear tests. Results of shear tests are presented in terms of maximum debonding forces, force-elongation curves, failure modes and strain profiles along the specimens. The use of Digital Image Correlation (DIC) technique allowed to obtain complete strain maps on the surface of the specimens tested, with the purpose of investigating possible variations in
the strain field within the bonded area
Non linear dynamic analysis of a reinforced concrete frame retrofitted with FRP
No full textIn seismic zones, some building could need a retrofitting. The fibre-reinforcement polymer/plastic (FRP) is a product that is possible to use as a retrofitting techniques. There are different types of FRP, and it is possible use them with different thickness. Then, the engineer needs simulate in a software different design of retrofitting to choose the best. He can select several methodologies of structural analysis. The non linear dynamic analysis is one methodology that can be more convenient for rehabilitation projects. Then it is necessary to study the possibility of the current software to simulate structures retrofitted with FRP. In this paper the non linear analysis of reinforcement concrete (RC) structures retrofitted with FRP, are considered. A frame that will be tested in a shaking table is studied without and with FRP. The inputs for the dynamic analysis are twelve real acelerogramas, that have different level of power. The software used permits consider non linear models, and a model for concrete with FRP. Several parameters of responses are evaluated. In the conclusions, the considerations about the non linear analysis for this type of structures are given
EFFECT OF MATRIX ON BOND BETWEEN FRCM AND MASONRY
Full text linkFiber Reinforced Cementitious Matrix (FRCM) composite materials. Bi-directional carbon and glass grids were applied by using cementitious mortar or natural hydraulic lime mortar. Tests on bricks were carried out first without surface preparation and then after treating them with sandblasting, in order to investigate possible improvements on the maximum debonding force after increasing adhesion between matrix and substrate. The study is focused on the analysis of the influence of different properties of the matrix on bond between FRCM and masonry. The effect of an adhesion promoter, developed in order to improve the adhesion between fibers and matrix and to limit the possible slip between them, was investigated. All the samples were subjected to single-lap shear tests until failure. The use of Digital Image Correlation (DIC) technique allowed to obtain complete displacement and strain maps on the surface of the specimens tested. The experimental results show good performance of CFRCM and GFRCM strengthening systems in combination with the adhesion promoter
Assessment of a bond strength model for FRP reinforcement externally bonded over masonry blocks
No full textAccording to recent design Codes and Recommendations, verification against debonding is imperative in the design of strengthening interventions with Fiber Reinforced Polymers (FRP). In FRP – reinforced masonry elements, debonding at reinforcement extremities (end debonding) must be avoided by limiting the maximum force achievable by the strengthening system. This paper proposes design criteria against debonding in masonry elements externally strengthened by FRP sheets. Results of more than 250 bond tests, reported in the literature and carried out over different masonry supports, clay bricks and natural stones, are collected and examined. Formulas for fracture energy of interface bond law and debonding load are assessed starting from the experimental database. In order to provide design formulas according to the Partial Safety Factor Method for Ultimate Limit State verification, mean and characteristic values of the debonding load are determined through statistical methods
Uni-axial Compressive Tests on Masonry Columns Confined by FRP and FRCM
Full text linkMany old masonry buildings, particularly in seismic regions without any provision for earthquake loading, are particularly vulnerable. This makes brick masonry structures unsafe and requires economical, safe and fast refurbishment measures. Traditional techniques, that were largely used and investigated in the past, may be inadequate in seismic areas where the added mass could generate a significant extra weight that induce an increase of the seismic actions. Moreover, when it is necessary to preserve the historical value of architectural heritage, the reversibility, compatibility and sustainability of the intervention could become critical for the selection of the most appropriate strengthening technique. Several investigations have shown that the use of Fiber Reinforced Polymers (FRP) materials on masonry structures can be effective for different purposes. On the other hand, few studies on masonry columns confined with Fiber Reinforced Cementitious Matrix (FRCM) are available in literature. In the present paper an experimental campaign devoted to analyse the effectiveness of different reinforcement typologies on square masonry columns built with clay bricks and cementitious mortar, in particular FRP and FRCM, will be reported. Two different configurations of the reinforcing system will be investigated: carbon or glass fibers, with organic or inorganic matrix, applied as external reinforcement along the perimeter of the masonry columns in the form of continuous and discontinuous wrap. The specimens were subjected to uni-axial compressive test until failure. The obtained experimental results showed an increment in the load bearing capacity of reinforced columns
IN SITU DIAGONAL COMPRESSION TESTS ON MASONRY PANELS STRENGTHENED BY FRP AND FRCM
Full text linkIn this paper, the results of a research project carried out on existing masonry walls belonging to the barn of a rural building struck by the 2012 Emilia earthquake are presented. The aims of the experimental campaign performed in situ were: to evaluate the actual shear capacity of existing double-leaf masonry walls, to quantify the improvements obtained by reinforcing the existing walls through FRP (Fiber Reinforced Polymers) or FRCM (Fiber Reinforced Cementitious Matrix) and to compare the effectiveness of the strengthening solutions in terms of structural performances. In particular, scrupulous attention was made on the selection of the masonry walls to be tested in order to consider the same masonry typologies with a similar level of material degradation. The specimens were isolated from the remaining masonry walls, in order to leave the panels undisturbed, and subjected to diagonal compression test, which allowed to characterize the mechanical properties of some typical masonry walls of the area and to evaluate the contribution of the proposed reinforcements. The experimental work allowed an evaluation of the shear strength and the failure mode in case of unidirectional (FRP) or bidirectional fiber (FRCM) reinforcements applied on masonry panels. The results of the tests on the reinforced panels showed a less brittle failure and a significant increase of shear strength and displacements with respect to the unreinforced masonry wall
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