Lapped joints of bars in bundles

The approach of European and North American Design Code rules for design of lapped joints of reinforcing bars within a bundle differ markedly, with the former permitting the same or shorter laps with respect to laps of individual bars, while the other requires longer laps. This paper reports an experimental in- vestigation to evaluate performance of lapped joints in which individual reinforcing bars within a bundle of two or three bars are lapped. The results show that it is not necessary to increase lap lengths of individual bars within a bundle, and that failure is less brittle where lap joints confined by links are staggered longitudinally, whether the lap is between individual bars or is of one bar in a pair or bundle. The outcome does, however, question the validity of the reductions permitted in EC2 for staggering laps, and suggests that it would be prudent to suspend use of the α6 reduction factor for proportion of bars lapped at a section pending more tho- rough investigatio

Is fiscal consolidation self-defeating? A Panel-VAR analysis for the Euro area countries

This paper studies the effects of fiscal consolidation on the debt-to-GDP ratio of 11 Euro area countries. Using a quarterly fiscal Panel VAR allows us to trace out the dynamics of the debt-to-GDP ratio following a fiscal shock and to disentangle the main channels through which fiscal consolidation affects the debt ratio. We define a fiscal consolidation episode as self-defeating if the debt-to-GDP ratio does not decrease compared to the pre-shock level. Our main finding is that when consolidation is implemented via a cut in government primary spending, the debt ratio, after an initial increase, falls to below its pre-shock level. When instead the consolidation is implemented via an increase in government revenues, the initial increase in the debt ratio is stronger and, eventually, the debt ratio reverts to its pre-shock level, resulting in what we call self-defeating austerity

Influence of the relative rib area on bond behaviour

Steel-to-concrete bond is a basic aspect of the behaviour of reinforced concrete structures both at serviceability and ultimate states. When bond rules were originally developed, experimental results were mainly obtained on normal- strength concrete and a minimum relative rib area (bond index) was required by building codes to ensure good bond properties. The arrival into the market of high-performance concrete and newer structural needs may require different bond indexes. In the present paper, the experimental results of pull-out tests on short anchorages are presented. Several pull-out tests on ribbed bars, embedded in cubes of normal- and high-strength concrete with a concrete cover of 4.5 times the bar diameter, were carried out in order to better understand the influence of the relative rib area and bar diameter on the local bond behaviour, as well as on the splitting crack width generated by the wedging action of ribs. A total of 96 tests were performed on machined bars of three different diameters (12, 16 and 20 mm) with a bond index ranging from 0.040 to 0.105. The results of 55 pull-out tests on commercial hot-rolled ribbed bars of four different diameters (12, 20, 40 and 50 mm) are also presented to confirm that the bond response also depends on bar diameter (size effect). Experimental results provide information concerning the influence of the relative rib area on bond strength and on the bursting force due to the rib’s wedge action. As the minimum measured bond strength of rebars was always markedly greater than the minimum bond strength required by building codes even when low bond indexes were adopted, the test results point out the possibility of reducing the minimum value of the relative rib area required by Eurocode 2 without limiting the safety coefficient of bond. The reduction also allows a higher structural ductility that can be achieved due to a greater strain penetration of the rebars from concrete cracks

Costo del seguro en accidentes de tránsito : conductores responsables

Fil: Casparri, María Teresa. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto de investigaciones administrativas, contables y matemáticas; Argentina.Fil: Metelli, María Alejandra. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Departamento de Matemática; Argentina.Muchos de los vehículos que circulan diariamente en nuestro país no están asegurados. la importancia de\ncontar con un parque vehicular asegurado no radica solamente en poder afrontar las consecuencias\neconómicas de los siniestros, sino que además las compañías aseguradoras están en condiciones de\nconstruir una base de datos a partir de la cual se pueda penalizar a aquellos conductores que presenten\nmayor siniestralidad y bonificar a quienes no sufran accidentes por su culpa. De este modo, los mismos\nasegurados verían el modo de lograr un mejor precio y, automáticamente, se verían obligados a cumplir\ncon las normas de tránsito

Von Bezold assimilation effect reverses in stereoscopic conditions

Lightness contrast and lightness assimilation are opposite phenomena: in contrast, grey targets appear darker when bordering bright surfaces (inducers) rather than dark ones; in assimilation, the opposite occurs. The question is: which visual process favours the occurrence of one phenomenon over the other? Researchers provided three answers to this question. The first asserts that both phenomena are caused by peripheral processes; the second attributes their occurrence to central processes; and the third claims that contrast involves central processes, whilst assimilation involves peripheral ones. To test these hypotheses, an experiment on an IT system equipped with goggles for stereo vision was run. Observers were asked to evaluate the lightness of a grey target, and two variables were systematically manipulated: (i) the apparent distance of the inducers; and (ii) brightness of the inducers. The retinal stimulation was kept constant throughout, so that the peripheral processes remained the same. The results show that the lightness of the target depends on both variables. As the retinal stimulation was kept constant, we conclude that central mechanisms are involved in both lightness contrast and lightness assimilation

Experimental Results on Staggered Lapped Bars in FRC

The paper presents experimental results on lap splices in fiber reinforced concrete (FRC). Four point bending tests were carried out on several full-scale beams with all or part of the longitudinal reinforcement lap spliced at mid-span. The beams were reinforced with either 16 mm or 20 mm diameter rebars and included various lap splices configurations varying the percentage of lapped bars. The behaviour of lapped bars in FRC with a volume content of steel hooked fibres equal to 0.5% was investigated. The results show that the post-peak behaviour of FRC can enhance the strength of staggered lapped splices as well as it can reduce their brittleness, thus allowing a reduction of lap length when only a portion of bars at a section are lapped. The results show also the benefits on the durability of concrete members due to the capability of the fibres to markedly reduce the splitting cracks along the splice at service loadings

Experimental and Numerical Analysis on the Core Lateral Thrust in Bolted BRBs

The paper aims at presenting numerical and experimental results on the lateral thrust exerted by the inner core of a buckling restraining brace (BRB) when, after buckling in compression, it arrives into contact with the external restraining case. The BRB consisted of a plate core restrained by bolted U- shaped member, thus allowing an easy assembly of the BRB, as well as the inspection and the substitution of its core after a seismic event [1, 2]. The results of six tests on BRBs having a plate core with a cross section of 5x50 mm2 and a dissipative length of 560 mm are shown. The gap dimension was varied between 0.25 and 0.70 mm. Cyclic displacements of increasing amplitude were applied to the core up to a steel strain of 2%, adopting the loading history prescribed by AISC standards [3]. The instrumented bolts connecting the restraining elements and a thin tactile pressure sensor placed within the gap allowed to steadily monitor both the lateral thrust and the buckling shape of the plate core during the experiment. The results showed that the lateral thrust increased linearly with the gap dimension, thus confirming the trend provided by the analytical formulation proposed by Genna and Gelfi [4]. As reported in Table 1, for a maximum axial force of about 110 kN, the value of the transverse thrust ranged from 36.5 kN in the specimen 1 with a gap of 0.25 mm to 86.6 kN in the specimen 3 with a gap of 0.70 mm. Furthermore, the specimens 6, without stiffening plates in the web of the restraining U- profiles, showed the significant role of the local transverse deformation on the value of the lateral thrust, which was twice the thrust of the specimen 1, characterized by the same gap of 0.25 mm but with a stiffened case. The experimental results allowed to validate a non-linear 3D Finite Element model performed with the code ABAQUS [5]. The numerical analyses accurately predicted the cyclic behaviour of the tested BRBs in term of axial load, buckling shape of the core and lateral thrust action. The difference between the measured thrust and the calculated thrust at the end of the loading history (steel strain c=2%) ranges between -8% to +17%, while the 2D plane stress model proposed in [6] overestimated the lateral thrust of +85%, owing to the inability of the 2D model to describe the local transverse deformations of the case