Reinforced Concrete Columns Confined with FRCM: Experimental Performances скачать в хорошем качестве

Reinforced Concrete Columns Confined with FRCM: Experimental Performances

Presented by Salvatore Verre, University of Calabria Fabric Reinforced Cementitious Matrix (FRCM) composites have the potential to improve the structural performances of concrete columns. As demonstrated by experimental investigations available in the technical literature, in fact, the FRCM confinement gives evidence of a remarkable increase of both strength and ductility of the existing concrete columns. Many parameters, both geometrical and mechanical, affect the performances of FRCM confined reinforced concrete columns: among those the fabric and matrix type, the confinement ratio (i.e. the number of FRCM layers), the FRCM configuration, the concrete strength, the shape of the section and the load eccentricity. The variability of these parameters and the wide variety of FRCM systems available on the market, make difficult the development of general design models. Some available design models, such as those proposed in Code provisions (ACI 549, fib, Italian Code, etc.,) in some cases are not able to well predict the structural response of FRCM confined reinforced concrete columns. At the same time, numerical models are, often, not reliable and complex from a design point of view. Accurate and detailed analyses are, then, needed to overcome these difficulties, improve the knowledge of the structural behavior of FRCM confined concrete columns and allow to define reliable design models. In the paper, the behavior of FRCM confined concrete columns is analysed both experimentally and theoretically. An experimental investigation was conducted on FRCM confined reinforced concrete columns with square cross section (10 columns, 800 mm height with 150x150 mm cross section). Parameters investigated were the number of confining FRCM layers, the type of fabric (PBO and steel), the type of mortar (cement-based and lime-based), the eccentricity values of the compression load, the internal steel reinforcement. The obtained results in terms of failure modes, axial capacity, longitudinal and transversal strain, were presented and discussed. These results together with other experimental results available in the literature were collected in order to define semi-empirical relationships able to predict the strength and strain values of FRCM confined reinforced concrete columns. Then results of the comparison between experimental results and predictions of the proposed model and other analytical models (Code models, other proposed models available in the literature) are, then, presented and discussed. The behavior of FRCM confined reinforced concrete columns is, also, analyzed through a numerical model founded on a Finite Element procedure, developed through Abaqus CAE 6.14. At this aim, available experimental results were used for the calibration regarding different types of matrix for FRCM-confinement. The model was performed by using the Plastic (P) and the Concrete Damage Plasticity (CDP) material constitutive laws. The FRCM-confined system was preliminary modeled as a homogenous elastic material until failure. The procedure is based on the macro-model approach in order to simulate the non-linear structural behavior of the reinforced concrete columns. A cohesive model and a bi-linear local bond-slip law are adopted to simulate the FRCM-to-concrete interface. The model accuracy is assessed by the comparison between numerical predictions and experimental results obtained by tests carried out on FRCM confined reinforced concrete columns.