1,721,030 research outputs found
La copertura del rischio di interesse del debito
No full textIl capitolo si propone di descrivere le caratteristiche tecniche dei prodotti derivati più comunemente utilizzati nelle operazioni di sviluppo immobiliare per coprire e gestire il rischio di interesse, con particolare riferimento alla copertura del rischio di interesse del debito a tasso variabile effettuata mediante interest rate swaps. interest rate collar e interest rate ca
A mechanical innovative approach for studying the buckling behavior of composite beams
Full text linkIn this paper a geometrically nonlinear model for studying the lateral global buckling problem of a generic thin-walled composite beams is presented. The model is based on a full second-order deformable beam theory and accounts for axial, flexural, shear, torsional and warping displacements as well as web/flange distortional ways of deformation. Governing nonlinear equations are derived from the Principle of Virtual Displacements. The first numerical results for thin-walled open GFRP profiles under flexural/torsional loads are presented
Debonding evolution in nonlinear FRP-retrofitted RC beams with cohesive T interface
Full text linkA novel semi-analytical formulation of the governing equations of an FRP retrofitted reinforced concrete beam under bending, based on the concept of moment-curvature, is presented and it is applied to compute the complete nonlinear load-deflection curve, FRP-concrete interfacial shear stress, the FRP laminate strain and the debonding load of statically determinate RC beams retrofitted by an adhesively bonded FRP laminate. The beam may be subjected to any loading, including uniformly distributed or discrete point load(s). The governing equations satisfy the equilibrium and strain compatibility requirements of the beam but slip at the FRP-concrete interface is permitted. A novel procedure for constructing the full nonlinear moment-curvature relationship of beams undergoing interfacial slip is presented in detail, but it is shown that practically a trilinear relationship is satisfactory for obtaining an accurate estimate of the beam deflection and stresses. The robustness and accuracy of the method are demonstrated by analyzing several beams tested by other researchers under uniformly dis- tributed load or four-point bending, with remarkably close agreement between the experimental and corre- sponding computed values
A nonlinear semi-analytical model for predicting debonding of FRP laminates from RC beams subjected to uniform or concentrated load
No full textA semi-analytical model is developed to determine in FRP retrofitted reinforced concrete (RC) beams the interfacial shear and peeling stresses, the FRP laminate and the RC section strain and stresses at all loading stages up to failure. The FRP is assumed to be externally bonded to the beam but can undergo slip and relative vertical displacement at its interface with the concrete. The model is developed by satisfying the requirements of equilibrium and strain compatibility while concurrently allowing for interfacial deformations. FRP is treated as a linear elastic, steel as elasto-plastic strain hardening and concrete as fully nonlinear material in compression and tension, including tension stiffening. The governing equations are formulated as two second order differential equations with their dependent variables being the strain in the FRP and the relative normal displacement of the interface. The equations are solved for discrete states (uncracked, cracked, yielded) experienced by the RC section and their associated level of interfacial slip. The model results are compared with available experimental results for several beams retrofitted with carbon FRP or steel reinforced polymer (SRP) laminates subjected to either four point bending or simulated uniform load, with satisfactory agreement between them
Modifications of standard GFRP sections shape and proportions for improved stiffness and lateral-torsional stability
Full text linkIn this paper the results of a comprehensive numerical investigation regarding the axial–flexural–torsional response of pultruded slender beams is presented. The goal is to propose GFRP standard cross-sections of such proportions and shapes that would possess improved strength, stability and deformational characteristics compared to the corresponding existing sections whose proportions are
generally based on standard steel sections. As GFRP sections are thin-walled but are significantly less stiff than similar steel sections, the study focuses on enhancing their appropriate stiffness and buckling
strength. The novel and efficient numerical model used in this investigation was developed by the writers and can be used to trace the complete pre-buckling geometrically nonlinear response of any GFRP or steel
thin-walled member with open or closed cross-section. The bucking load is computed by the asymptotic value of the load–displacement curve. Members with I-, L-, T- and box sections are analyzed, considering
different loading and boundary conditions. It is demonstrated that due to their unsuitable proportions, available standard GFRP sections do not have adequate stiffness and buckling strength. Consequently,
recommendations are made for new sectional proportions and modified shapes, and some graphical results are presented to demonstrate how the results of the proposed method could be utilized in
practical design situations. The superiority of the proposed sections is quantified by an efficiency factor, defined in terms of ratio of strength gain to material volume increase
Pre-buckling behavior of composite beams: a mechanical innovative approach
Full text linkIn this paper a geometrically nonlinear model for studying the lateral global buckling problem of a generic thin-walled composite beam is presented. The model is based on full second-order deformable beam theory and accounts for axial, flexural, shear, torsional and warping displacements. Moreover, the web/flange junctions are supposed to be deformable. Governing nonlinear equations are derived from the principle of virtual displacements. Initial numerical results, obtained by means of a finite element approximation, deal with open cross-section composite profiles under flexural/torsional loads, making it possible to identify the relevance of connection stiffness over the pre-buckling range of the mechanical response. Comparisons with numerical and experimental results available in the literature are also discussed
A COMPARISON BETWEEN COMPOSITE AND STEEL BEAMS IN THE FLEXURAL-TORSIONAL EQUILIBRIUM PROBLEM
Full text linkIn this paper the first results of a comprehensive numerical investigation regarding the flexural–torsional response of pultruded slender beams is presented. The goal of the re-search is to propose GFRP standard cross-sections of such proportions and shapes that would possess improved strength, stability and deformational characteristics compared to the corresponding existing sections whose proportions are generally based on stan-dard steel sections. As GFRP sections are thin-walled but are significantly less stiff than similar steel sections, the study focuses on enhancing their appropriate stiffness and buckling strength. The novel and efficient numerical model used in this investigation was developed by the writers and can be used to trace the complete pre-buckling geo-metrically nonlinear response of any GFRP or steel thin-walled member with open or closed cross-section. The bucking load is computed by the asymptotic value of the load-displacement curve. It is demonstrated that due to their unsuitable proportions, available standard GFRP sections do not have adequate stiffness and buckling strength. Consequently, relative to I- cross section only recommendations are made for new sectional proportions and modified shape. The superiority of the proposed section is quantified by an efficiency factor, defined in terms of ratio of strength gain to material volume increase
Beam-to-column adhesive connection between GFRP profiles
No full textThe feasibility of adhesively bonded connections in FRP frame structures
is explored, for the first time, as an alternative to bolted
connections. In particular, the influence of seat angles on the failuire
load is analyzed experimentally. Three full-scale GFRP beam-column are
tested and their failure mode, strength and rotational stiffness are
investigated. A single pultruded GFRP I-profile is used for the two
members. The beam-column assembly forms an inverted L-shape frame,
with the column being fixed at the bottom and attached to the beam
near the top. The beam, acting as a cantilever, is loaded by a point load
near its free end, which subjects the connection to bending and shear.
The test results reveal that increasing the stiffness of the seat angles
there is a less abrupt fall of the load after the peak. Anyway, the
connection can have at least the same strength as the corresponding
bolted connection, irrespective of whether GFRP or steel bolts are used
to make the connection, hence the current prohibition against the use
of adhesive beam-column connections in GFRP frame structures may be
unjustified
LATERAL BUCKLING PROBLEM: MODIFICATIONS OF STANDARD GFRP SECTIONS SHAPE AND PROPORTIONS
Full text linkIn this paper the first results of a comprehensive numerical investigation regarding the flexural–torsional response of pultruded slender beams is presented. The goal of the research is to propose GFRP standard cross-sections of such proportions and shapes that would possess improved strength, stability and deformational characteristics compared to the corresponding existing sections whose proportions are generally based on standard steel sections. As GFRP sections are thin-walled but are significantly less stiff than similar steel sections, the study focuses on enhancing their appropriate stiffness and buckling strength. The novel and efficient numerical model used in this investigation was developed by the writers and can be used to trace the complete pre-buckling geometrically nonlinear response of any GFRP or steel thin-walled member with open or closed cross-section. The bucking load is computed by the asymptotic value of the load-displacement curve. It is demonstrated that due to their unsuitable proportions, available standard GFRP sections do not have adequate stiffness and buckling strength. Consequently, relative to T-cross section only recommendations are made for new sectional proportions and modified shape. The superiority of the proposed section is quantified by an efficiency factor, defined in terms of ratio of strength gain to material volume increase
Biblioteche e intelligenza artificiale: dalle {Linee} guida {IFLA} al problema dell’agency
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