78,828 research outputs found
Structural behaviour of Gerber half-joints subjected to steel corrosion
No full textThe Gerber half-joints assessment is today a topical problem since they are widespread in the infrastructure heritage of different countries. These structural elements are often affected by chloride corrosion phenomena due to their positioning under the deck joint. The paper presents some of the results of a wide research survey, developed at the Laboratory of the University of Rome Tor Vergata, aimed at evaluating their behavior when subjected to corrosion decay, up to failure, through experimental tests and analytical models. The experimental behavior of the specimens, designed with different criteria, and subjected to different degree of accelerated corrosion, is discussed. An accurate design phase of the specimens was followed, based on typical Strut and Tie models, to obtain peculiar and different failure mechanisms, involving both brittle and “ductile” crises. Particular care was devoted to the corrosion process, suitably calibrated for providing different degradation scenarios. The obtained results are analyzed and discussed in terms of load-displacement curves and cracking pattern, underlying the influence of corrosion on the failure mechanism. The experimental outcomes show that both design details and reinforcement corrosion could compromise the strength and ductility requirements of the elements and need to be accounted for in analytical and numerical structural assessment of existing corroded Gerber half-joints
Safety assessment of existing post-war reinforced concrete bridges. The case study of ‘Gerber girders' bridges in Italy
No full textThe interest in the structural maintenance design of existing bridges of the Italian road network is nowadays growing, due to the need to overcome structural inadequacies and/or degradation phenomena. In this framework, the new "Guide-lines for risk management, safety assessment and monitoring of existing bridges" outline the required procedures and tools, identifying the most critical issues of the different bridges’ structural typologies, including Gerber girders in reinforced concrete bridges. A safety assessment of Gerber bridges is thus mandatory as for the presence of joints which do not comply with current design practice and codes as for the occurrence of aging-related decay phenomena, e.g. due to water infiltration. In this context, a novel cross-disciplinary procedure for the assessment of Gerber bridges is here presented, giving an insight on the so-called ‘knowledge phase’. Firstly, the paper analyses the introduction and diffusion of this structural typology in Italy, giving a classification of existing Gerber bridges and focusing on their recurrent degradation phenomena. Finally, a discussion on historical sources which can be used to draw useful information, e.g. construction history surveys, archival drawings, calculation manuals and codes, is presented
Experimental evaluation of the corrosion influence on the structural response of Gerber half-joints
No full textThe assessment of the Gerber half-joints (or saddles), widespread in the infrastructure heritage of different countries, is nowadays a topical problem since they are often affected by chloride corrosion phenomena due to their positioning under the deck joint. In this paper, the influence of steel rebar corrosion on the experimental response of Gerber half-joints is experimentally analysed and discussed. In particular, four elements were cast in Laboratory of University of Rome “Tor Vergata” two of which subjected to accelerated corrosion, and then tested up to failure. The specimens were designed with typical strut and tie models, with the aim of achieving different failure modes governed by the concrete crush or by the tensile rebar breaking. Particular care was devoted to the corrosion process, in order to simulate decay scenarios typical of these structures. The experimental outcomes, expressed in terms of load–displacement curves, crack patterns and failure mechanisms show that also medium-slight degree of pitting corrosion can cause great reductions in capacity and ductility of the saddles, modifying, in addition, their failure mechanism. Finally, from the experimental outcomes, the sensitivity of these peculiar structures, not only to the corrosion amount, but also to its spatial distribution among the different steel rebars, and its morphology (pitting or uniform corrosion) is clearly underlined. As a consequence, the necessity to accurately and properly account for the corrosion phenomenon in the structural assessment is remarked
The Benefits of Being Economics Professor A (and not Z)
No full textAlphabetic name ordering on multi-authored academic papers, which is the convention in the economics discipline and various other disciplines, is to the advantage of people whose last name initials are placed early in the alphabet. As it turns out, Professor A, who has been a first author more often than Professor Z, will have published more articles and experienced afaster growth rate over the course of her career as a result of reputation and visibility. Moreover, authors know that name ordering matters and indeed take ordering seriously: Several characteristics of an author group composition determine the decision to deviate from the default alphabetic name order to a significant extent.performance measurement, incentives, economists, name ordering
Final word on Jersey Dutch
No full textIn this article, William Z. Shetter compares and contrasts the dialects that developed between different Dutch colonies in the New World. He explores in-depth the nuances of Jersey Dutch, and provides theories to explain how Dutch and colonial languages blended. The article is reprinted from American Speech, December 1958, Volum XXXIII, No. 4
Safety Assessment of Existing Post-War Reinforced Concrete Bridges. The Case Study of ‘Gerber Girders’ Bridges in Italy
No full textThe interest in the structural maintenance design of existing bridges of the Italian road network is nowadays growing, due to the need to overcome structural inadequacies and/or degradation phenomena. In this framework, the new "Guide-lines for risk management, safety assessment and monitoring of existing bridges" outline the required procedures and tools, identifying the most critical issues of the different bridges’ structural typologies, including Gerber girders in reinforced concrete bridges. A safety assessment of Gerber bridges is thus mandatory as for the presence of joints which do not comply with current design practice and codes as for the occurrence of aging-related decay phenomena, e.g. due to water infiltration. In this context, a novel cross-disciplinary procedure for the assessment of Gerber bridges is here presented, giving an insight on the so-called ‘knowledge phase’. Firstly, the paper analyses the introduction and diffusion of this structural typology in Italy, giving a classification of existing Gerber bridges and focusing on their recurrent degradation phenomena. Finally, a discussion on historical sources which can be used to draw useful information, e.g. construction history surveys, archival drawings, calculation manuals and codes, is presented
Energy balance and cancers
No full textEnergy balance results from the exact equilibrium between caloric intake and caloric expenditure. A caloric intake larger than caloric expenditure results in overweight, even obesity, but other determinants, like hormonal dysfunction and/or genetic traits may play a part in obesity syndrome. Obesity, and even overweight, have been recognized as risk factors for the development of cancers. Human epidemiological studies, which have tended to establish the nature of the relationship between energy balance and cancer, are summarized first, with the influence of the various factors which act both on obesity and on cancer risk. Among these factors are the macronutrients responsible for the caloric intake, and some lifestyle factors (physical activity, drinking habits and tobacco use). Second, the animal studies help to distinguish between different relevant factors, and to understand some of the underlying mechanisms. However, the insulin-resistance syndrome, which appears to underlie the relationship between obesity and hormone-dependent cancers, and possibly colon cancer, is only relevant to human physiology because hormonal alterations are part of it. Prevention of hyperinsulinemia, insulin resistance and the accompanying visceral obesity appears to be a major public health task for the prevention of cancers
Experimental evaluation of the non-linear nehavior of existing GerberhHalf-joints in presence of corrosion
No full textThe gerber half-joints assessment is today a topical problem since these are widespread in the italian infrastructure heritage. These elements, classified as “critical” by the recent italian guidelines (LG20), are often affected by chloride corrosion phenomena due to their positioning under the deck joint. The research program, aimed at evaluating the non-linear behaviour of gerber half-joints, includes the cast of sixteen specimens, which were designed and tested until failure according to different design models, reinforcement amount, and increasing corrosion levels of the reinforcement. This paper presents the first results of two un-corroded and two corroded specimens. The experimental outcomes show that both design details and reinforcement corrosion could compromise the strength and ductility requirements of the saddles. Furthermore, the authors believe that the results can represent a strong scientific reference for the analytical and numerical structural assessment of existing corroded gerber half-joints
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
On Gerber-Shiu functions and optimal dividend distribution for a Lévy risk-process in the presence of a penalty function
No full text09.02.15 KB. Ok to add working paper to Spiral, author hold copyrightThis paper concerns an optimal dividend distribution problem for an insurance
company which risk process evolves as a spectrally negative L\'{e}vy process
(in the absence of dividend payments). The management of the company is assumed
to control timing and size of dividend payments. The objective is to maximize
the sum of the expected cumulative discounted dividend payments received until
the moment of ruin and a penalty payment at the moment of ruin which is an
increasing function of the size of the shortfall at ruin; in addition, there
may be a fixed cost for taking out dividends. A complete solution is presented
to the corresponding stochastic control problem. It is established that the
value-function is the unique stochastic solution and the pointwise smallest
stochastic supersolution of the associated HJB equation. Furthermore, a
necessary and sufficient condition is identified for optimality of a single
dividend-band strategy, in terms of a particular Gerber-Shiu function. A number
of concrete examples are analyzed
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