Search results for "Compres"
showing 10 items of 1107 documents
EXPERIMENTAL AND NUMERICAL EVALUATION OF THE MECHANICAL BEHAVIOUR OF GFRP SANDWICH PANELS
2007
This work deals with the analysis of the mechanical behaviour of a class of sandwich structures widely employed in marine constructions, constituted by fiber-glass laminate skins over PVC foam or polyester mat cores. In detail, a systematic experimental study and numerical simulations have shown that the theoretical prediction of the strength and the actual failure mechanism of these sandwich structures can be affected by significant errors, specially in the presence of prevalent shear loading. Moreover, because of the low shear stiffness and the elastic constants mismatch of the skins and core material, failure modes and strength are strongly influenced by eventual stresses orthogonal to t…
Analytical modelling of force transmission in axially loaded RC columns with indirectly loaded jackets
2019
Abstract Concrete and steel jacketing are common strengthening techniques for reinforced concrete (RC) columns subjected to axial loads. In the most of cases the external jacket is made leaving gaps between the strengthening layer and the slabs, avoiding to carry directly a portion of the load. In this way, the external jacket induces a confinement pressure on the inner column, and its beneficial effect is due to the increase of strength and ductility. However, shear stresses develop on the interface between the column and consequently, the external jacket can be considered indirectly loaded. It sustains a portion of the axial load, which depends by the value of the axial shortening, relati…
Measurement of Young's modulus of cementitious materials using an electro-optic holographic technique
2001
Abstract The electro-optic holographic technique has already been used to determine Young's dynamic modulus in homogeneous materials based on the resonance frequency of the analysed samples. This paper shows a modification of the determination method of this frequency that speeds up this process thus obtaining Young's modulus. Based on the visualisation of real time fringes drawn by exciting the rods at the 1000–10,000 Hz range, the proposed method allows us to determine their resonance frequencies. This procedure has been used in the analysis of non-homogeneous materials such as mortar and concrete. The results obtained by this method show good correlation with those determined by the conv…
Compressive behavior of short fibrous reinforced concrete members with square cross-section
2011
In the present paper a mechanical model to predict the compressive response of high strength short concrete columns with square cross-section confined by transverse steel is presented. The model allows one to estimate the equivalent confinement pressures exercised by transverse steel during the loading process taking into account of the interaction of the stirrups with the inner core both in the plane of the stirrups and in the space between two successive stirrups. The lateral pressure distributions at hoop levels are obtained by using a simple model of elastic beam on elastic medium simulating the interaction between stirrups and concrete core, including yielding of steel stirrups and dam…
Strength and ductility of R.C. columns strengthened with steel angles and battens
2012
Abstract In this paper the behaviour of R.C. members externally strengthened with steel angles and battens subjected to axial force and bending moment is analysed. A fibre model was utilised to predict the moment–curvature diagrams of the strengthened members on the basis of stress–strain curves of the constituent materials (confined concrete, steel bars and angles) recently derived by the author. The stress–strain curves utilised for compressed concrete were able to take into account the confinement effects induced by longitudinal (bars and steel angles) and transverse (stirrups and battens) steel reinforcements. Constitutive laws in compression for confined concrete and steel bars and ang…
Phase-matching measurements and Sellmeier equations over the complete transparency range of KTiOAsO_4, RbTiOAsO_4, and CsTiOAsO_4
2000
The sphere method is used for the direct measurement of sum- and difference-frequency generation phase matched in the principal planes of KTiOAsO4, RbTiOAsO4, and CsTiOAsO4, including the tuning curves of 1.064-µm-pumped OPO’s emitting between 3 and 5 µm. The nonlinear least-squares fitting of our experimental data leads to refined dispersion equations of the principal refractive indices; the resulting dual-oscillator form equations are valid over the complete transparency range of the three studied materials.
A critical plane approach based on energy concepts: application to biaxial random tension-compression high-cycle fatigue regime
1999
Abstract In this paper the energy parameter, defined for random loadings, is analysed. Under uniaxial loading this parameter distinguishes between the strain energy density for tension (positive) and the strain energy density for compression (negative). As a consequence, if there is no mean component in the random loading, we obtain a random history of strain (elastic and plastic) energy density with zero expected value. Under multiaxial loadings the normal strain energy density in the critical plane (i.e. the plane of the maximum damage) is understood as the energy parameter. The history of strain energy density is schematized with use of the rain-flow algorithm. Fatigue damage is accumula…
Overstrength requirements to avoid brittle shear failure in RC slender beams with stirrups
2020
Abstract In this paper, an analytical expression was derived for the prediction of shear strength of slender reinforced concrete (RC) beams with stirrups. Failure occurring in B and D regions of the beam was considered. An expression derived for the shear strength of the B region was based on a modified constant angle truss model. The analytical expression derived consisted of three terms. The first one was related to the concrete contribution expressed through the square root of cylindrical compressive strength, geometrical ratio of longitudinal bars, and depth to width ratio. The second one was relating to the shear force induced by yielding of stirrups to the inclination of the main crac…
Influence of FRP wrapping techniques on the compressive behavior of concrete prisms
2006
Abstract Results of an experimental investigation on the compressive behavior of concrete prisms with square cross-section, externally wrapped with carbon fiber reinforced plastic (CFRP) sheets are presented. The effects of the following parameters were analyzed: local reinforcement at the corners and continuous layers; horizontal and vertical discontinuous strips; number of continuous layers—length of specimens. An analytical model is proposed to determine the maximum bearing capacity of compressed concrete members with square cross-section and externally wrapped with FRP for the different configurations examined, and also able to consider the strength reduction with the length increase of…
Behaviour in compression of lightweight fiber reinforced concrete confined with transverse steel reinforcement
2004
Abstract The compressive behavior of lightweight fiber reinforced concrete confined with transverse reinforcement consisting of steel stirrups or spirals was analyzed. Pumice stone and expanded clay aggregates were utilized to decrease the weight of the composite; hooked steel fibers were also added. The investigation was carried out by testing cylindrical and prismatic specimens of different sizes in compression using an open-loop displacement control machine, recording the full load–deformation curves. The influence of the dimensions and shape on the bearing capacity and on the ductility of the specimens confined with transverse steel reinforcements was analyzed. The results show the poss…