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

Adaptation of river channels to a wetter or drier climate: Insights from the Lower Pilcomayo River, South America

Climate change has a direct influence on both hydrology and floodplain vegetation of water courses, which are key players in river morphodynamics. The river system response to climate change is complex and the effects of non-linear interactions between alterations in water, sediment and vegetation remain incompletely understood. Which of these components becomes dominant in shaping the river channel when climate becomes drier or wetter? To answer this question, we investigate the cross-sectional response of sand-bed rivers to climate change focusing on channel width and depth, which respond directly to changes in boundary stresses. Thanks to the exceptional availability of long time-series of daily discharge and cross-sectional profiles, the Pilcomayo River is an ideal living lab for this investigation. We constructed a two-dimensional model of the river using the open-source state-of-the-art, structured Delft3D code. The highly dynamic behaviour and quick morphological adaptation of the Pilcomayo allowed reducing the period of time covered by the simulations because the river cross-section adapts its morphology to a new value of the water discharge within hours or days, which is crucial for modelling investigations. Calibration and validation were successfully performed by comparison with historical data. We considered several scenarios representing current, dryer and wetter climates. The results show that a dryer climate reduces the river channel depth and enlarges the width. A wetter climate increases the channel depth but produces negligible widening. Vegetation, sparser with a drier climate and denser with a wetter climate, is found to control the channel width. This analysis is unique and shows which alterations can be expected in alluvial sand-bed rivers with natural vegetated banks due to climate change

Development of preliminary assessment tools to evaluate debris flow risks

In the framework of the IMPRINTS European Research Project (FP7), a toolbox for fast assessment of debris flow hazard has been developed. The aim of this toolbox is to implement different existing models inside a common package useful for a fast evaluation of potential hazard. The initiation and propagation of the debris flow is included. One of the requirements of the projects is to define different scenarios with different detail levels in data input. As an example of this, the results could be obtained just using topographical data or improve accuracy by adding geological and hydrological data.Postprint (published version

Expression of auxin-binding protein1 during plum fruit ontogeny supports the potential role of auxin in initiating and enhancing climacteric ripening

Auxin-binding protein1 (ABP1) is an active element involved in auxin signaling and plays critical roles in auxin-mediated plant development. Here, we report the isolation and characterization of a putative sequence from Prunus salicina L., designated PslABP1. The expected protein exhibits a similar molecular structure to that of well-characterized maize-ABP1; however, PslABP1 displays more sequence polarity in the active-binding site due to substitution of some crucial amino-acid residues predicted to be involved in auxin-binding. Further, PslABP1 expression was assessed throughout fruit ontogeny to determine its role in fruit development. Comparing the expression data with the physiological aspects that characterize fruit-development stages indicates that PslABP1 up-regulation is usually associated with the signature events that are triggered in an auxin-dependent manner such as floral induction, fruit initiation, embryogenesis, and cell division and elongation. However, the diversity in PslABP1 expression profile during the ripening process of early and late plum cultivars seems to be due to the variability of endogenous auxin levels among the two cultivars, which consequently can change the levels of autocatalytic ethylene available for the fruit to co-ordinate ripening. The effect of auxin on stimulating ethylene production and in regulating PslABP1 was investigated. Our data suggest that auxin is involved in the transition of the mature green fruit into the ripening phase and in enhancing the ripening process in both auxin- and ethylene-dependent manners thereafter

T-REX Operating Unit 3

OU3 is one of the six Operating Units of the Progetto Premiale T-REX. It is focused on the development of adaptive optics instrumentation for the European Extremely Large Telescope. The main activities of OU3 are the MAORY adaptive optics module, the MICADO infrared camera, the characterisation and forecast of atmospheric parameters for the E-ELT site and general developments for future adaptive optics systems. <P /

MAORY: adaptive optics module for the E-ELT

MAORY is one of the four instruments for the E-ELT approved for construction. It is an adaptive optics module offering two compensation modes: multi-conjugate and single-conjugate adaptive optics. The project has recently entered its phase B. A system-level overview of the current status of the project is given in this paper

EXPERIMENTAL STUDY ON THE LATERAL THRUST GENERATED BY CORE BUCKLING IN BOLTED-BRBs

The paper presents the results of cyclic loading tests on all-steel buckling-restrained braces (BRBs), with the aim of investigating the contact phenomena and the associated lateral thrust occurring when the inner core of a BRB, after buckling, comes into contact with the external restraining case. A special test set-up was employed to detect the shape and extension of the contact zones, as well as the local contact pressures. Attention was focused on the role of certain key parameters governing the high-mode plastic buckling of the core, such as the size of the gap between the core and the restraining members, the stiffness of the containing case, and the cyclic loading history. The results show that the value of the lateral thrust generated by the core during its high-mode buckling increases, possibly up to very high values, with the gap/core thickness ratio, the axial core strain, and the cumulated plastic deformation of the core. The results might be a useful tool both to validate analytical expressions and numerical models for the assessment of the lateral thrust. Moreover, test results on full-size all-steel bolted BRBs showed that the design of the containment profiles and relevant connections cannot be made without an accurate estimate of the lateral thrust exerted by the buckled core under the adopted loading conditions