111,975 research outputs found
Experimental analysis on the time-dependent bonding of FRP laminates under sustained loads
No full textFiber reinforced composite materials are frequently used in the rehabilitation or upgrading of existing structures. From a design point of view, current international guidelines on FRP strengthening applications do not give rules based on rigorous approaches to evaluate the reliability and durability of strengthening interventions with respect to long-term behavior. In order to give a contribution on this topic, the authors have carried out a creep experimental program on retrofitting systems, either of carbon or glass fibers and subject to different stress values in regime of constant temperature. The tests have been carried out by means of a dedicated test device that provided a pure bending stress state in the strengthened beam, being the external loads held constant over time. In this paper the results of their investigation and critical analysis are presented. © 2012 Elsevier Ltd. All rights reserved
Effects of recycled PET fibres on the mechanical properties and seawater curing of Portland cement-based concretes
No full textThis paper deals with an experimental study on the mechanical properties of recycled polyethylene terephthalate fibre-reinforced concrete (RPETFRC) and its durability in an aggressive seawater environment. A Portland limestone cement-based concrete with a 0.38 water/cement ratio is used to cast cubic and prismatic specimens, in association with two different PET fibres obtained through extrusion of recycled PET flakes (R-PET). Some of these specimens were conditioned in the Salerno harbour seawater for a period of 6/12 months. Compressive strength and four-point bending tests are performed in order to investigate the mechanical properties of such RPETFRCs. Comparison of the present results and those in the literature for air-cured RPETRCs highlights the influence of the analysed R-PET fibres on the mechanical properties of concretes showing different water/cement ratios and binders. The given results for seawater-cured specimens demonstrate that such a curing condition slightly modifies the first-crack strength and markedly reduces the toughness of the RPETFRCs examined in the present work. © 2014 Elsevier Ltd. All rights reserved
Kroton e il suo territorio tra VI e V secolo a. C. : aggiornamenti e nuove ricerche : atti del Convegno di studi, Crotone, 3-5 marzo 2000
No full textEffectiveness of the confinement of underdesigned columns using Composites
No full textEdited by Bruno, Spadea and Swamy. Cosenz
Macro-scale analysis of local and global buckling behavior of T and C composite sections
No full textBuckling modes of pultruded Fiber Reinforced Polymer (FRP) beams are analyzed in this paper. The study is performed on the basis of two mechanical models recently proposed by the authors with regard to global and local buckling of composite thin-walled beams. These models are developed within the theory of small strains and moderate rotations and they take into account the contribution of shear deformation. The constitutive law here adopted is based on the homogenization of the material properties at the macro scale level. With regard to local stability, the junctions are considered as semi-rigid connections, whose stiffness is strongly influenced by the microstructure of the material. A discussion on the effects of the beam geometry and on the failure modes is presented. They may consist in local or global buckling as well as in material failure. Further, the global buckling may be torsional or lateral. The discussion is supported by non-dimensional diagrams which can be useful in design involving "T" and "C" sections subject to axial and bending loads. © 2013 Elsevier Ltd. All rights reserved
Local buckling analysis of pultruded frpthin-walled beams and columns
No full textIn this paper a mechanical model capable to predict the local buckling of pultruded FRP thin-walled beams and columns, taking into account the shear deformability of composite materials, is presented. The model is based on the individual analysis of buckling of the components of FRP profile, assumed as elastically restrained transversely isotropic plates. The analysis is developed within the field of small strains and moderate rotations
Pre-buckling imperfection sensitivity of pultruded FRP profiles
No full textThis paper presents a geometrically non-linear one-dimensional model suitable for analyzing thin-walled fiber-reinforced polymer profiles, which accounts for the effect of manufacturing imperfections. The kinematic model is developed under the hypotheses of small strains and moderately large rotations of the cross-sections, and is able to take into consideration the contribution of shear strains and the effects related to warping displacements. The aim of the study is to develop a proper tool to analyze the pre-buckling behavior of such beams, since current approaches based on two-dimensional finite element method analysis demand significant computational efforts to be applied to real structures. The numerical results underline the effectiveness of the proposed mechanical model in analyzing case studies of technical interest in Civil Engineering, and the relevant influence of geometrical imperfections on the structural performance of FRP components with regard to serviceability design requirements
Buckling failure modes of FRP thin-walled beams
No full textA study on buckling phenomena in pultruded Fiber Reinforced Polymer (FRP) beams, based on two mechanical models recently formulated by the authors with regard to composite thin-walled beams, is presented in this paper. Global buckling behavior is analyzed by means of a one-dimensional model in which cross-section torsional rotation is divided into two parts: the first one, associated with Vlasov's axial warping, the second one, associated entirely with shear strains. The study of local behavior is based on the individual buckling analysis of the components of FRP profile, assumed as elastically restrained transversely isotropic plates. Both mechanical models take into account, within the field of small strains and moderate rotations, the contribution of shear deformation in the kinematic hypotheses. Design charts suitable to evaluate the buckling load of FRP "I" beams with either narrow or wide flanges are obtained and presented in this paper. © 2012 Elsevier Ltd. All rights reserved
Local buckling behavior of FRP thin-walled beams: A mechanical model
No full textA mechanical model able to predict the local buckling of pultruded FRP thin-walled beams and columns, taking into account the shear deformability of composite materials, is presented in this paper. The model is based on the individual analysis of the buckling of the components of the FRP profile, assumed as elastically restrained transversely isotropic plates. The analysis is developed within the hypotheses of small strains and moderate rotations. © 2012 Elsevier Ltd
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