Papers by Keyword: Fiber Reinforced Polymer (FRP)

Abstract: Excessive exploitation of fresh water and river sand has prompted researchers to investigate seawater sea sand concrete (SWSSC) as a viable alternative to traditional concrete in the construction sector. The mechanical properties of SWSSC columns are comparable to traditional concrete columns, and these properties can be further enhanced through confinement. Strengthening or retrofitting of SWSSC columns with Fibre reinforced polymer (FRP) sheets in a single-skin fashion is an effective and easy way to achieve this enhancement. This review summarizes the available literature on the experimental investigation performed to date on single-skin confined SWSSC columns using different types of FRP sheets under compressive loading. Full wrapping, partial wrapping, and non-uniform wrapping are the three wrapping strategies under this confinement scheme. Employed wrapping strategy, FRP material type, number of layers of FRP, cross-sectional shape of the columns, and concrete strength are the key parameters that influence the ultimate strength and ultimate strain of the confined specimens. The failure modes and stress-strain curve characteristics for the three wrapping strategies are discussed. Finally, some directions for future research work in this area are also proposed.

Abstract: Fiber Reinforced Polymer (FRP) has been used in construction as it is lightweight, has flexural strength, is more durable and resistant to corrosion, impact, and fire. Finite Element Analysis (FEA) is a modern technique to predict the tensile behavior and cracking pattern of structural members using nonlinear finite element analysis (NLFEA). In this current study, 11 specimens of Glass Fiber Reinforced Polymer (GFRP) reinforced concrete (RC) Beams with different reinforcement bars (#5, #6 and #8 bars) and spacing (30mm, 38mm and 50 mm) along with two different concrete strengths (Normal and high strength) were modelled to predict the flexural behavior, Moment deflection behavior and cracking pattern using ABAQUS 6.12. These specimens were modeled in ABAQUS using CDP Model and calibration was performed on basis of viscosity, dilation angle and meshing size. The outcomes of numerical modeling were compared with those of the experimental results. It has been shown that there is a slight disparity with very small differences between the experimental and numerical results.

Abstract: Large panel structures made of composites are common building units in aerospace industries. In order to increase the stiffness of such structures, the panel or skin is adhered to a flange and supported by a web. Such a stiffened panel is modeled as an arrangement of web, flange and panel with an interface between the flange and the panel. In this paper, three dimensional stress analysis of one such stiffened panel has been carried out using the finite element analysis. The geometric non-linearity has been assumed in the analysis. The effect of material anisotropy and the laminate stacking sequence on the stress components has been studied. Material Graphite Fiber Reinforced Polymeric (GFRP) composite has been used and, two different configurations were considered while the unidirectional prepregs were laid up in quasi-isotropic [0/0/0/0]₂ and cross-ply [0/90/90/0]₂. Subsequently, the coupled stress failure criterion has been used to predict the critical location of damage onset. When component damage indicator attained the value of 1.0, the component was considered to lose stiffness and structural integrity.

Abstract: This paper reports the findings from an analytical study into the influence of fiber reinforced polymer (FRP)-to-concrete interface gap and prestressed FRP tubes on strain reduction factor (k_ε) for concrete-filled FRP tube (CFFT) columns. A database that consists of a total of 45 aramid FRP- (AFRP) confined normal-and high-strength concrete (NSC and HSC) specimens with circular cross-sections is presented. All specimens were cylinders with a 152 mm diameter and 305 mm height, and their unconfined concrete strengths ranged from approximately 45 to 110 MPa. Analyses of the experimental databases that consisted of 22 specimens manufactured with FRP-to-concrete interface gap and a further 23 specimens prepared with lateral prestress is presented and discussed. Based on close examination of the hoop strain development on the FRP confining shell, expressions to predict strain reduction factors (k_ε) are proposed. The comparison of the proposed model predictions with the experimental test results of specimens prepared with an interface gap or prestressed FRP tubes shows good agreement.

Abstract: A set of individual URM walls as well as an assemblage of a three-storey URM hollow clay block masonry structure composed of two shear- and two cross-walls have been tested in original and strengthened state. As a method of strengthening, the coating of the walls, consisting of glass fiber reinforced polymer (GFRP) grid laid in fiber reinforced cementitious mortar matrix (sometimes called textile reinforced mortar), anchored to the walls with glass fiber anchors, has been used. All specimens were subjected to constant vertical load simulating the effect of gravity loads and cyclic horizontal displacements with step-wise increased amplitudes, induced either at the top of the walls or at the floor levels of the assemblage, simulating the effect of seismic loads.The observed behaviour and failure mechanisms were of the shear type. The results show that by the application of FRP reinforced coatings, the seismic performance of URM structures can be significantly improved. As the results of experiments indicate, the energy dissipation, displacement capacity and shear resistance of URM increase substantially. In this regard, adequate anchoring of coating to the masonry and into the r.c. floor structures is essential.

Abstract: The aim of the paper is to propose and assess the reliability of a modeling strategy which combines the homogenization of the masonry material and the use of zero-thickness interface elements. This strategy is specifically proposed for numerically investigating the structural response of FRP-reinforced curved masonry structures. Indeed, in order to consider the influence of the geometry curvature of the masonry substrate on the local bond behavior of the FRP-strengthening system, bond-slip laws which specifically account for the geometric curvature of the substrate are introduced at the FRP/substrate interface layer. Numerical analyses concerning masonry arches selected from the current literature are presented in the paper in order to assess the reliability of the proposed modelling approach.

Abstract: In the last decade, Fibre Reinforced Polymer (FRP) wrapping technique has become a common method to retrofit masonry piers or columns with poor structural performances. The passive confinement effect induced by the external wrap allows increasing the compressive strength and ductility of the member. Several studies highlighted as the efficacy of this technique is affected by several key parameters, including the shape of the transverse cross section, stress intensification at the strength corner of sharp sections, amount and mechanical properties of adopted composite. Despite this technique has been widely studied from both theoretical and experimental point of view, most of studies focused on short columns and little information is available on the influence of second order effects on its structural efficacy. This paper presents a simplified method able to assess the effect of FRP confinement on slender columns. A preliminary evaluation of the constitutive law in compression of FRP confined masonry is made and the best-fitting model is adopted to model masonry in compression. Sectional analysis is performed by including the tensile strength of masonry and considerations are made on the increase of ultimate moment and curvature. Finally, the effect of column slenderness is considered using a simple numerical procedure, making it possible to calculate the allowable slenderness ratios as a function of the maximum drift, taking into account both strength and stability.

Abstract: This article provides an overview of ACI 440.7R – Design Guide for Strengthening of Masonry with FRP Systems. ACI 440.7R was developed by the American Concrete Institute (ACI) Committee 440 and published in 2010. ACI 440.7R has recently revised to include new topics. This article provides an overview of the design methodologies recommended by ACI 440 for flexural and shear strengthening of masonry walls, confinement of masonry, and repair (“stitching”) of cracked masonry with FRP systems.

Abstract: The present paper deals with concept, prototyping and application of a tensioning system for FRP ties into masonry structures. The proposed system, based on the use of FRP strands instead of traditional steel ties, has the aim to produce a compression stress state on masonry walls where it is applied. Given the objective difficulty in tensioning a FRP strand, it was necessary to both characterize and prototype a suitable connection system between the strand and the pulling system. The experimental phase concerned both the manufacturing of the pulling system and the study of used materials, as well as the characterization of the impregnation technology of FRP ties. The above described system has been produced and used in the framework of the structural retrofitting of the “Real Albergo dei Poveri” building in Naples.

Abstract: Over the past two decades, composite materials, in forms of Fiber Reinforced Polymers (FRP), have been widely spread worldwide in the field of civil and monumental construction. Design guidelines and provisions were developed and provided by national and international institutions. In the last years, a new generation of materials, named Fabric Reinforced Cementitious Matrix (FRCM) were introduced as strengthening devices for concrete and masonry structures. Their application in the field of historical masonry has grown as a result of the recent Italian earthquakes. In this paper, starting from a retrospective on what has been done in recent years in the field of FRP applications, insights will be discussed for future research and applications of FRP and FRCM in heritage buildings. Some differences between FRP and FRCM materials will be highlighted, in terms of fiber-matrix interface and delamination mechanisms. The different micromechanical behavior in terms of fracture energy will be highlighted, and the macro-mechanical implications in terms of ductility will be pointed out, as a first attempt to quantify this complex problem. By considering the last innovative and pioneering applications of FRP/FRCM in heritage buildings, criteria for structural enhancement will be shown and discussed. This is done with a special focus on the ability, shown by these new technologies, to inhibit failure mechanisms in masonry artifacts.