Papers by Ciro Del Vecchio
Proceedings of SPIE - The International Society for Optical Engineering, 2004
The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) ar... more The two 911mm-diameter adaptive secondary (AS) mirrors for the Large Binocular telescope (LBT) are currently under construction. The design of the units has been based on the extensive experience made on the MMT adaptive secondary mirror during laboratory tests and telescope runs. Mechanics, electronics and control logic have been revised to improve performances and reliability. Each unit has 672 electro-magnetic force actuators. They control the figure of the Gregorian secondary 1.6mm-thick mirrors with an internal loop using the signal of co-located capacitive sensors. The improvement in the computational power of the on-board control electronics allows to use it as real-time computer for wavefront reconstruction. We present the progress of the final unit construction and the preliminary laboratory results obtained with a 45-actuator sub-system used to test the new features introduced in the electronics and mechanics of LBT adaptive secondary mirrors.
Proceedings of …, 1998
We present the result of electrical and optical measurements performed on a reduced size adaptive... more We present the result of electrical and optical measurements performed on a reduced size adaptive secondary prototype named P30. The design of this concave deformable mirror consists of a thin deformable glass shell whose figure is controlled by electromagnetic actuators and ...
Meccanica, 1988
Sommario E' stato sviluppato uno studio per determinare le caratteristiche di ten... more Sommario E' stato sviluppato uno studio per determinare le caratteristiche di tensione nella regione di collegamento fra due gusci cilindrici con assi ortogonali. Lo studio è basato sull'impiego delle formulazioni classiche della teoria dell'elasticità. L'analisi dello stato di tensione riguarda la zona prossima all'intersezione dei due gusci, con esclusione dei punti singolari. Tre gradi di approssimazione del modello analitico permettono
Meccanica, 1988
Sommario E' stato sviluppato uno studio per determinare le caratteristiche di ten... more Sommario E' stato sviluppato uno studio per determinare le caratteristiche di tensione nella regione di collegamento fra due gusci cilindrici con assi ortogonali. Lo studio è basato sull'impiego delle formulazioni classiche della teoria dell'elasticità. L'analisi dello stato di tensione riguarda la zona prossima all'intersezione dei due gusci, con esclusione dei punti singolari. Tre gradi di approssimazione del modello analitico permettono
Composite Structures, 2016
The design of an adaptive secondary mirror has to satisfy many requirements coming from different... more The design of an adaptive secondary mirror has to satisfy many requirements coming from different fields. The thin mirror must be actuated very precisely with a large bandwidth. The reference plate has to provide a high stability reference for the optical surfaces. The local seeing is not to be degraded by any significant thermal perturbation. In this article, the performances of a configuration with a single aluminum reference plate, that also provides the heat sink, are computed starting from the input power coming from the magnetic actuators, whose magnetic design has been revised.
ABSTRACT The paper presents results from numerical analyses of reinforced concrete (RC) elements ... more ABSTRACT The paper presents results from numerical analyses of reinforced concrete (RC) elements subjected to cyclic load. Many nonlinear numerical models have been proposed in literature to capture the cyclic behaviour of reinforced concrete (RC) elements. Depending on the expected level of accuracy and computational efficiency, numerical models employ differ-ent assumptions. These assumptions ultimately affect the stiffness, strength, energy dissipation capacities and hysteretic behaviours such as strength/stiffness degradation and pinching. All of these sensitively affect the dynamic response of a structure subjected to seismic load. The objective of this work is to investigate the effects of adopted numerical models on predicted seismic performances of RC structures. Three numerical elements that are widely used in re-search and practice are employed; fiber element in OpenSees, frame element in VecTor5, and continuum element in VecTor2. In an element level, the behaviour responses of the different numerical models are closely compared. A few representative experimental results from PEER Column Test Database are used to investigate the accuracy of each numerical model depending on the shear demand/capacity ratio of the columns. The paper concludes with a suggestion for the applicability of different numerical models for the seismic performance as-sessment.
Adaptive Optics and Applications, 1997
ABSTRACT Several load conditions, including gravity, effects of moments due to magnet decentering... more ABSTRACT Several load conditions, including gravity, effects of moments due to magnet decentering, and forces applied by the central restraining membrane, have been analyzed for the 632 mm diameter, 2 mm thick adaptive secondary mirror, being developed for the MMT Telescope. All these effects can be kept well within the optical specifications.
The structural damage of reinforced concrete (RC) or masonry constructions, is commonly, associat... more The structural damage of reinforced concrete (RC) or masonry constructions, is commonly, associated with nonlinear phenomena that make the analysis of the structural behavior a challenging task. This is even more difficult for shear critical structures. Furthermore , the severe cracking may be associated, in these cases, with an incipient collapse, due to the limited ductility of shear critical members. Advanced mechanical-based theories has been developed in order to accurately capture the post-cracking behavior of shear critical structural systems; although accurate, such theories required complex calculations that make their use not suitable for practical applications. Recent technological developments in computational capacity opened to the implementation of accurate and complex theories on the nonlin-ear behavior of RC structures in software suitable to accurately reproduce the nonlinear behavior of structural systems. Computer-aided nonlinear analyses are nowadays widespread i...
Advanced Technology Optical Telescopes V, 1994
Earthquake Engineering & Structural Dynamics, 2015
ABSTRACT The nonlinear behavior of reinforced concrete (RC) members represents a key issue in the... more ABSTRACT The nonlinear behavior of reinforced concrete (RC) members represents a key issue in the seismic performance assessment of structures. Many structures constructed in the 1980s or earlier were designed based on force limits; thus they often exhibit brittle failure modes, strength and stiffness degradation, and severe pinching effects. Field surveys and experimental evidence have demonstrated that such inelastic responses affect the global behavior of RC structural systems. Efforts have been made to consider the degrading stiffness and strength in the simplified nonlinear static procedures commonly adopted by practitioners. This paper investigates the accuracy of such procedures for the seismic performance assessment of RC structural systems. Refined finite element models of a shear critical bridge bent and a flexure-critical bridge pier are used as reference models. The numerical models are validated against experimental results and used to evaluate the inelastic dynamic response of the structures subjected to earthquake ground motions with increasing amplitude. The maximum response from the refined numerical models is compared against the results from the simplified static procedures, namely modified capacity spectrum method and coefficient method in FEMA-440. The accuracy of the static procedures in estimating the displacement demand of a flexurecritical system and shear-critical system is discussed in detail.
Major seismic events have shown the high vulnerability of existing RC structures, especially for ... more Major seismic events have shown the high vulnerability of existing RC structures, especially for those designed according to obsolete code provisions. Field surveys have identified the brittle failure modes of poorly detailed beam-column joints as one of the main cause of vulnerability. This encouraged the scientific studies to investigate their seismic behaviour and find reliable and cost-effective strengthening solutions. Experimental evidences demonstrated the effectiveness of fiber reinforced polymers (FRP) systems increasing the global seismic capacity of structural systems. However, even if a large number of experimental tests on beam-column subassemblies have been carried out, simple and generalized formulations able to predict the increase of shear strength provided by the FRP system are still lacking. This paper proposes a critical review of the existing capacity models for beamcolumn joints retrofitted with FRP systems basing on recent experimental findings. The outlined e...
ABSTRACT The paper presents results from numerical analyses of reinforced concrete (RC) elements ... more ABSTRACT The paper presents results from numerical analyses of reinforced concrete (RC) elements subjected to cyclic load. Many nonlinear numerical models have been proposed in literature to capture the cyclic behaviour of reinforced concrete (RC) elements. Depending on the expected level of accuracy and computational efficiency, numerical models employ differ-ent assumptions. These assumptions ultimately affect the stiffness, strength, energy dissipation capacities and hysteretic behaviours such as strength/stiffness degradation and pinching. All of these sensitively affect the dynamic response of a structure subjected to seismic load. The objective of this work is to investigate the effects of adopted numerical models on predicted seismic performances of RC structures. Three numerical elements that are widely used in re-search and practice are employed; fiber element in OpenSees, frame element in VecTor5, and continuum element in VecTor2. In an element level, the behaviour responses of the different numerical models are closely compared. A few representative experimental results from PEER Column Test Database are used to investigate the accuracy of each numerical model depending on the shear demand/capacity ratio of the columns. The paper concludes with a suggestion for the applicability of different numerical models for the seismic performance as-sessment.
Engineering Structures, 2015
ABSTRACT The high vulnerability of existing reinforced concrete (RC) structural systems is often ... more ABSTRACT The high vulnerability of existing reinforced concrete (RC) structural systems is often related to brittle failures of critical members. Field surveys and relevant scientific studies showed that unconfined and poorly detailed beam-column joints were not able to resist moderate-to-large seismic events. Several strengthening techniques have been proposed to improve the seismic capacity of existing RC beam-column joints. The effectiveness of composite materials, such as fiber reinforced polymer (FRP) systems, has been demonstrated by experimental tests on joint subassemblies and entire structural systems. This, along with the simplicity of installation, has strongly promoted the use of the composite material for seismic retrofit of RC structures. However, the large number of parameters affecting the mechanical behavior of FRP strengthened beam-column joints makes the development of reliable capacity models complex. In recent years several proposal have been advanced, but a simple and generalized formulation is still lacking. This paper presents a new strength capacity model to account for the strength increase provided by FRP systems in the seismic retrofit of poorly detailed corner joints. A large database of experimental tests has been analysed to assess the accuracy of the proposed model. The simple theoretical approach and the use of experimentally determined parameters make this model suitable for practical applications.
Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 2012
ABSTRACT The Visible and Near Infrared (VNIR) spectrometer of the EChO will cover the spectral ra... more ABSTRACT The Visible and Near Infrared (VNIR) spectrometer of the EChO will cover the spectral range between 0.55 and 2.50 μm. It has to be designed to assure a high efficiency over whole spectral range. It has to be able to observe stars with an apparent magnitude Mv= 9÷12 and able to see contrasts of the order of 10-4÷10-5 in order to measure characteristics of the exoplanets under investigation. VNIR would be a spectrometer in a cross-dispersed configuration by using a combination of a diffraction grating and a prism to spread the light in different wavelengths and in a useful number of orders of diffraction. It will use a Mercury Cadmium Telluride detector to satisfy the requirements of low thermal noise and the EChO system to operate at the working temperature of 40-45K. The instrument will be interfaced to the telescope optics by optical fibers to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench. The preliminary design of the instrument foresees a resolving power of about 330 with an entrance aperture of 2 arcsec.
Ground-based and Airborne Instrumentation for Astronomy, 2006
GIANO is a cryogenic cross-dispersed spectrometer whose optics consist of aspheric aluminum mirro... more GIANO is a cryogenic cross-dispersed spectrometer whose optics consist of aspheric aluminum mirrors, glass flats, cross-dispersing prisms and a grating fixed onto a ~1.5×1.0 m aluminum bench. The primary aim of the project is to achieve the highest possible image quality and spectral stability essential for precise radial velocity measurements. The instrument also includes other observing modes which are obtained by inserting a flat mirror or a prism at different positions in the optical path. This flexibility is achieved without affecting the stability and performances of the primary, high resolution mode. We describe here the cryo-mechanical design which has been optimized to these purposes.
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Papers by Ciro Del Vecchio