Search results for "Compres"
showing 10 items of 1107 documents
RC column externally strengthened with RC jackets
2013
In this paper the behaviour in compression of RC columns externally strengthened with concrete jacketing is analysed and a cross-section analysis of the jacketed member under axial load and bending moment is developed. The focus was to study the effect of confinement of concrete jacket on concrete core and the behaviour of compressed bars with buckling effects. Some other important aspects such as shrinkage, creep, old to new concrete surfaces and bond split effects were not included in the model because: the use of thick non-shrink grout jacket and a well-roughened surface of old-to-new concrete was supposed; long term effects were included though corrective coefficients for monolithic beh…
Compressive behaviour of concrete elliptical columns confined by single hoops
2007
The compressive behaviour of short concrete members having elliptical cross-sections and confined with single steel hoops is investigated. An analytical model is given for calculation of the stress-strain curves of compressed members also including the valuation of the ultimate stress corresponding to formation of a complete failure plane in the concrete core. The model is able to evaluate the confining pressure due to steel hoops referring to a fictitious reduced area of the confined core and to the effective stresses in the hoops, which are variable along the perimeter; moreover, it makes it possible to determine the maximum compressive strength and the corresponding strain of the confine…
Experimental performance evaluation of a vapour compression refrigerating plant when replacing R22 with alternative refrigerants
2011
Abstract This paper presents the results of an experimental analysis comparing the performance of a vapour compression refrigerating unit operating with R22, and its performance in comparison to a new HFC fluid, substituting the former according to Regulation No 2037/2000. In particular, the plant working efficiency was first tested with R22 and then with three new HFC fluids: R417A, R422A and R422D. The investigation verified that despite the case of substitution and the advantage of being able to continue to use mineral oil as a lubricant in the compressor, the performance with the new tested fluids did not result as efficient as when using R22.
An analytical approach for the evaluation of the optimal combustion phase in spark ignition engines
2009
It is well known that the spark advance is one of the most important parameters influencing the efficiency of a spark ignition engine. A change in this parameter causes a shift in the combustion phase, whose optimal position, with respect to the piston motion, implies the maximum brake mean effective pressure for given operative conditions. The best spark timing is usually estimated by means of experimental trials on the engine test bed or by means of thermodynamic simulations of the engine cycle. In this work, instead, the authors developed, under some simplifying hypothesis, an original theoretical formulation for the estimation of the optimal combustion phase. The most significant parame…
A Refined Model for Knock Onset Prediction in Spark Ignition Engines Fueled With Mixtures of Gasoline and Propane
2015
In the last decade, gaseous fuels, such as liquefied petroleum gas (LPG) and natural gas (NG), widely spread in many countries, thanks to their prerogative of low cost and reduced environmental impact. Hence, bi-fuel engines, which allow to run either with gasoline or with gas (LPG or NG), became very popular. Moreover, as experimentally demonstrated by the authors in the previous works, these engines may also be fueled by a mixture of gasoline and gas, which, due to the high knock resistance of gas, allow to use stoichiometric mixtures also at full load, thus drastically improving engine efficiency and pollutant emissions with respect to pure gasoline operation without noticeable power los…
Applicability of over-coring technique to loaded RC columns
2014
Stress determination is a very important step in the assessment of the safety of existing reinforced concrete structures. In rock mechanic this goal is achieved with the over-coring technique. The main idea behind such a technique is to isolate a material sample from the stress field in the surrounding mass and monitor its re-equilibrium deformation response. If the materials remains elastic, and elastic properties are known, stresses may be obtained from the corresponding measured strains. The goal of this paper is to evaluate if the over-coring technique is applicable to reinforced concrete members. The results of an experimental investigation on the behaviour of compressed concrete colum…
Stability analysis of clay brick masonry columns: numerical aspects and modelling strategies
2014
Stability analysis of masonry piers and columns is one of the most frequently treated subjects in the field of structural engineering. This attention is probably due to the challenge to solving the problem including different effects, which play an important role in evaluating the response of eccentrically-loaded columns. In this connection, accurate stability analysis of masonry piers and columns has to take into account the non-linear stress–strain law of masonry in compression, the limited tensile strength, the induced slenderness due to crack formation and geometrical non-linearity. Different theoretical models and numerical approaches were developed in the past to analyze the combined …
LPV Model Identification For The Stall And Surge Control of a Jet Engine
2001
Abstract The problem of identifying discrete-time Linear Parameter Varying (LPV) models of non-linear or time-varying systems for gain scheduling control is considered assuming that inputs, outputs and the scheduling parameters are measured, and a form of the functional dependence of the coefficients on the parameters is known. The identification procedure is applied to the controlled model of compressors for jet engines. The model is controlled in order to avoid rotating stall and surge. Aim of the present paper is to identify the LPV model based on the nonlinear model of compressors in order to design a robust gain scheduling predictive controller.
Simplified flexural response of steel-fiber reinforced concrete beams
2008
In the present paper, an analytical model is proposed that is able to determine the flexural response of supported beams under four-point bending tests. Cases of normal strength reinforced concrete beams with longitudinal bars in the presence of reinforcing hooked steel fibers and transverse stirrups are considered. A simplified analytical model is presented that is able to calculate the load-deflection curves and the maximum and ultimate deflections occurring in the case of shear or flexure failures. In the case of shear failure, the maximum shear strength of the beams is evaluated by using a recent analytical expression proposed by the author able to account for the shear-to-moment intera…
Los hábitos lectores en inglés de futuros maestros: Implicaciones didácticas
2014
Se presenta un estudio exploratorio y descriptivo sobre los hábitos lectores en inglés de estudiantes universitarios españoles para detectar cuáles son las áreas de atención prioritaria para poder seguir un Grado en inglés según el EEES. Se midió el nivel de inglés mediante el Oxford Online Placement Test. Se evaluaron los hábitos lectores y el tipo de materiales académicos que los estudiantes leen en inglés mediante un cuestionario. Gran parte de la muestra se encontraba en los niveles elementales e intermedios de dominio del inglés. Un porcentaje muy elevado de estudiantes declaró no tener el hábito de leer en inglés y leer solo materiales académicos obligatorios. Sin embargo, existe una …