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

Inter-sectorial collaboration in networks: A Boundary Object approach to wine routes

Wine routes are used to enhance food and wine tourism development but, despite academic research devoted to studying them has increased over time, the emergent perspective interpreting wine routes as “Boundary Objects” deserves further research. This study aims to develop a framework rooted in the concept of “Boundary Objects”. To achieve this objective, a qualitative research was carried out on the Cannonau wine route (Sardinia, Italy). Our findings present a “comprehensive” framework, showing how different types of inter-organizational partnerships under the threats of different external and internal factors can shape a “Boundary Object”. Although this research is based on a top-down wine route and on a limited number of interviews, this is the first attempt to apply concepts specifically developed within Boundary Objects literature in the study of wine routes. Managers of similar types of wine routes should make sure that clear boundaries and shared goals are agreed among stakeholders. Future research should analyse other constructs developed within Boundary Objects literature in order to fully understand the contribution of Boundary Objects to the literature on networks in tourism

Laboratory prototype for the demonstration of sodium laser guide star wavefront sensing on the E-ELT

The new class of Extremely Large Telescopes (ELT) relies on Sodium Laser Guide Stars (LGS) to improve the Adaptive Optics performance in terms of correction quality and sky coverage. The time instability and the vertical extension of the atmospheric Sodium layer density have a potential significant impact on the wavefront sensing accuracy. We describe a laboratory prototype which has been developed with the goal to investigate specific algorithms for wavefront sensing with these artificial sources under different conditions of sodium layer density profile, parallactic effects due to laser launch geometry and atmospheric turbulence. The prototype can emulate realistic elongated spots on the focal plane of a Shack-Hartmann wavefront sensor (SHWFS), including their intensity variations due to the time variability of the Sodium density vertical profile. In addition, multiple LGSs can be simulated, one at a time, and a two-layer atmospheric turbulence model is available. Herein we report the verification of prototype performances, including optical performance, accuracy of emulated Sodium density profiles and atmospheric turbulence features. <P /

Modelling the multi-conjugate adaptive optics system of the European Extremely Large Telescope

MAORY is the Multi-Conjugate Adaptive Optics Module for the E-ELT. The baseline design assumes six sodium Laser Guide Stars and three Natural Guide Stars for wavefront sensing. Three deformable mirrors, including the telescope adaptive mirror M4, are optically conjugated to different altitudes in the atmosphere to achieve compensation of the atmospheric turbulence effects over an extended Field of View. In preparation for the project phase-B we are analyzing different critical aspects of such a system. We are developing a versatile and modular end-to-end simulation code that makes use of GPUs to obtain high-fidelity modelling of the system performance and, in parallel, a semplified code for the analysis of the effects induced by the temporal variation of the sodium layer where the artificial laser guide stars are generated. An overview of the work in progress will be given. <P /

Possible application of FPGA to the MAORY Real Time Computer

MAORY is the post-focal Adaptive Optics module for the European Extremely Large Telescope first light. The baseline of MAORY is to rely upon the use of multiple Laser Guide Stars (6), multiple Natural Guide Stars (3) for wavefront sensing and multiple Deformable Mirrors (DM) for correction (M4/M5, that are part of the telescope, and 2 post focal DMs). The Real-Time Computer is a key sub-system of MAORY. It must collect the measurements from various sensing devices and drive several thousands actuators within high demanding latency requirements dictated by the system performance needs. The FPGA technology has been widely diffused in Real Time Systems due to its low latency and high determinism. Performance evaluation of this technology for the wavefront sensors images calibration and processing is in progress

Numerical simulations of MAORY MCAO module for the ELT

MAO (MAORY Adaptive Optics) is the a developed numerical simulation tool for adaptive optics. It was created especially to simulate the performance of the MAORY MCAO module of the Extremely Large Telescope. It is a full end-to-end Monte-Carlo code able to perform different flavors of adaptive optics simulation. We used it to investigate the performance of a the MAORY and some specific issue related to calibration, acquisition and operation strategies. As, MAORY, MAO will implement Multi-conjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The implementation of the reference truth WFS completes the scheme. The simulation tool implements the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and use libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code

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