Masonry columns strengthened with Steel Fabric Reinforced Cementitious Matrix (S-FRCM) jackets: Experimental and numerical analysis

The structural performances of masonry columns confined with Fabric Reinforced Cementitious Matrix (FRCM) is analysed, both experimentally and theoretically, in this paper. The analysis refers to clay brick masonry columns confined with a steel-FRCM strengthening system made by steel fiber sheets with an inorganic matrix. An experimental investigation on steel-FRCM confined clay brick masonry columns having an overall height of 770 mm with rectangular cross-section 250 × 250 mm was carried out. Columns were tested under axial and eccentric load until collapse. The test parameters considered in this study were the number of confining layers and the load eccentricity. In addition, a numerical 3D model was calibrated by both results of the experimental tests of this work and results available in the literature. A numerical model was realized by the commercial code Abaqus, based on the macro-model approach in order to simulate the non-linear structural behaviour of masonry columns. The outcome of this investigation allows to evaluate the influence of considered parameters on the effectiveness of the confinement both in terms of strength and ductility

Analysis of the behavior of FRCM confined clay brick masonry columns

The behavior of FRCM (Fabric Reinforced Cementitious Mortar) confined clay brick masonry columns is analyzed in this paper. The results of an experimental investigation conducted on small-scale columns made by clay brick masonry confined with steel-FRCM (or Steel Reinforced Grout, SRG), PBO (poly-paraphenylene-benzo-bisoxazole) FRCM and basalt-FRCM, tested under monotonic compressive load, are described and discussed. Tests were conducted on thirteen prismatic columns; eleven columns (two unconfined and nine confined) were tested under concentric load while an eccentric load was applied on two confined columns. For each confinement system, the parameters investigated were the 'confinement ratio', the 'load eccentricity' and the 'overlap configuration of the fiber fabrics'. FRCM confinement improved the structural response of masonry columns in terms of ultimate strength, ultimate strain and ductility. Some models from the literature were also examined to evaluate their applicability in predicting the axial capacity of confined columns

Structural Performances of Concrete beams with Hybrid (Fiber-Reinforced Polymer-Steel) Reinforcements

The paper analyzes the structural behavior of concrete beams reinforced with hybrid fiber-reinforced polymer (FRP)-steel reinforcements. The analysis refers to concrete beams reinforced with FRP rebars placed near the outer surface of the tensile zone, with low cover thickness values, and steel rebars placed at the inner level of the tensile zone, with high cover thickness values, able to protect the steel from the corrosion. Such reinforcement allows one to optimize the structural behavior of beams and guarantees a good level of ductility and rigidity. Results of an experimental and theoretical investigation are presented and discussed. Significant features of the structural behavior regarding deflection, curvature, ductility, crack width, and spacing are pointed out. Ultimate and serviceability conditions are examined, highlighting the influence of mechanical and geometrical parameters affecting the behavior of hybrid reinforced-concrete beams

Influence of the Strengthening Configuration on the Shear Capacity of Reinforced Concrete Beams Strengthened with SRG (Steel-Reinforced Grout) Composites

In this paper, the influence of the strengthening configuration on the structural response of U-wrapped SRG (Steel-Reinforced Grout) shear-strengthened reinforced concrete beams was analyzed both experimentally and theoretically. The parameters varied were the ratio sf/wf, sf being the distance between two consecutive U-shaped strips and wf the width of the strips, and the number of steel fabric layers (one and two). Two series of real-scale beams, eleven beams in total with one un-strengthened and ten strengthened, were tested up to failure (the results obtained in the first series of tests were reported in a previously published paper). The obtained results highlighted that the debonding phenomena, which occurred for all the examined strengthening configurations, strongly affected the shear capacity of strengthened beams. An analytical model found based on the “effective strain” of the SRG strips was developed to predict the shear capacity of SRG shear-strengthened reinforced concrete beams. Two analytical relationships were proposed to evaluate the “effective strain” of the SRG strips: The first one was based on a statistical analysis of results obtained by tests on FRCM (Fabric-Reinforced Cementitious Mortar) and SRG shear-strengthened reinforced concrete beams, while the second was developed through the results of single lap direct shear tests performed on SRG-to-concrete joints. The effectiveness of the proposed analytical methods was evaluated through the comparison of their predictions and available experimental results

Structural behaviour of fabric reinforced cementitious matrix (FRCM) strengthened concrete columns under eccentric loading

The structural behaviour of eccentrically loaded reinforced concrete columns with rectangular cross sections strengthened with a cement based composite materials wrapping system, is analysed in the paper, both experimentally and analytically. The main issues focussed in the paper were: i) the effectiveness of the cement based wrapping systems to improve the strength of the reinforced concrete columns, ii) the influence of the load eccentricity and the reinforcement ratio on the structural response of wrapped columns, iii) the prediction, by an analytical procedure, of the structural behaviour of wrapped columns. A total of 8 reinforced concrete columns with end corbels, wrapped with fabric meshes of PBO (short of Polypara-phenylene-benzo-bisthiazole) fibers embedded into a cement based matrix (PBO-FRCM system), were tested varying both the reinforcement ratio, ρf, and the eccentricity-to-section height ratio (e/h). The influence of mechanical and geometrical parameters on the structural response of wrapped columns was analysed in terms of failure modes, strength and ductility. To predict the structural response of wrapped columns, a non linear second-order analysis that takes into account the changes in geometry caused by lateral deformations is, also, developed. Theoretical results were compared with experimental ones to validate the effectiveness of the proposed procedure

Experimental and numerical investigation on the steel reinforced grout (Srg) composite-to-concrete bond

In the paper, the bond between a composite strengthening system consisting of steel textiles embedded into an inorganic matrix (steel reinforced grout, SRG) and the concrete substrate, is investigated. An experimental investigation was carried out on medium density SRG specimens; direct shear tests were conducted on 20 specimens to analyze the effect of the bond length, and the age of the composite strip on the SRG-to-concrete bond behavior. In particular, the tests were conducted considering five bond length (100, 200, 250, 330, and 450 mm), and the composite strip’s age 14th, 21st, and 28th day after the bonding. Test results in the form of peak load, failure modes and, bond-slip diagrams were presented and discussed. A finite element model developed through commercial software to replicate the behavior of SRG strips, is also proposed. The effectiveness of the proposed numerical model was validated by the comparison between its predictions and experimental results

Cracking and deformability analysis of reinforced concrete beams strengthened with externally bonded carbon fiber reinforced polymer sheets

The paper is devoted to the cracking and deformability analysis of steel reinforced concrete beams strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. A theoretical nonlinear model, derived from a cracking analysis founded on slip and bond stresses, is adopted. The model takes into account both the tension stiffening effects of the concrete and the force transfer between the concrete and the CFRP sheet at the interface. A local bond-slip law—defined by experimental tests, carried out on concrete specimens strengthened with CFRP sheets—is adopted in the model. The slip between the concrete and the traditional steel bars is also considered. Theoretical predictions, in terms of crack width, curvature, and deflections, are compared with available experimental results and predictions of traditional models, usually adopted for design purposes. Obtained results are presented and discussed