Mr. Leo Colussi Profile

Leo Colussi

at Cimolai SpA

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Proceedings Article | 13 December 2020 Presentation + Paper

ELT design progress: the Dome structure

Leo Colussi, Marco Mattietto, Riccardo Terrassan, Marco Colussi, Stefano Stanghellini, Maximilian Kraus

Proceedings Volume 11445, 1144509 (2020) https://doi.org/10.1117/12.2562591

KEYWORDS: Domes, Telescopes, Structural design, Control systems, Large telescopes, Optical telescopes, Earthquakes, Aerodynamics, Cladding

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The Dome of the Extremely Large Telescope (ELT) is under construction at Cerro Armazones, in the Chilean Andes. It is constituted by a concrete pier, with an 86 m diameter concrete wall, and a rotating enclosure on it; the maximum height is about 80 m. The Dome will protect the 40 m class optical telescope, inside it, and must withstand wind speeds of over 40 m/s, as well as strong earthquakes. The whole structure is seismically isolated at the base, for an overall seismic mass of about 35000 t. The rotating enclosure main elements are a truss steel structure, having a base ring and a series of arch girders. It has a hemispherical shape to enhance the aerodynamic behavior and it weighs close to 6500 t. Two slit doors allow the telescope observation, guaranteeing a 42 m wide and 64 m long opening. The enclosure’s Azimuth Rotation Mechanism is constituted by 36 trolleys, installed on the top beam of the concrete pier, on a diameter of 86 m. Cladding covers the Dome structure and it is designed in order to provide proper thermal insulation and to withstand the harsh environmental site conditions. A windscreen, made of four permeable panels, having 42 m span and 10 m height each, protects the Telescope during observation and controls the airflow around it, together with a series of 89 louvers, placed both on the rotating and the fixed part of the Dome. In the Auxiliary Building, which is a ring surrounding the pier, technical rooms to operate and maintain the telescope are hosted. A custom HVAC system controls the temperature with a ±2 °C precision inside the Telescope chamber having about 300000 m3 volume.

Proceedings Article | 13 December 2020 Presentation + Paper

Performance analysis overview for the main structure of the Extremely Large Telescope

Marco Colussi, Leo Colussi, Nathalie Ninane, Jonathan Verspecht, Babak Sedghi, Michael Mueller

Proceedings Volume 11450, 114500R (2020) https://doi.org/10.1117/12.2562512

KEYWORDS: Large telescopes, Telescopes, Mathematical modeling, Vibrometry, Servomechanisms, Finite element methods, Infrared telescopes, Optical instrument design, Resistance, Modeling

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The Extremely Large Telescope (ELT) is the largest optical and infrared telescope being planned and constructed at the present time. Its resolution overtakes current limits of performance for large telescopes, as well as current levels for all the engineering fields involved in the design and realization of the telescope. The design of the ELT Main Structure (MS) is supported by exhaustive performance and resistance analyses, which have now largely been completed. A Finite Element Model (FEM) of the MS has been created to analyse the telescope behaviour against all the significant actions, among which gravity, wind, seism, thermal, manufacturing and alignment tolerances can be mentioned. The model is characterized by several millions of degrees of freedom and it includes the Telescope pier and foundation, as well as the seismic isolation system and the natural soil. A detailed Computational Fluid Dynamic (CFD) model has been produced and validated with the support of a wind tunnel test campaign. Several cases of telescope orientation and Altitude configuration, wind velocities and turbulence intensities have been analysed. A State Space model has been set-up to perform the Servo analysis of the Azimuth and Altitude axes. Frictions and motor disturbances, encoders quantization, loops sampling and latencies have been considered, to assess tracking, slewing and offsetting performances and to assess the structural behaviour and the wind rejection. Finally, a comprehensive mathematical model of Dome, MS and soil has been set-up to perform the vibration analysis of the whole observatory. The purpose of this paper is to provide an overview of the generated models, the performed analyses and the most significant obtained results.

Proceedings Article | 13 December 2020 Poster + Presentation + Paper

ELT design progress: The main structure

Leo Colussi, Marco Colussi, Gianmarco Franceschini, Pascal Martinez, Maximilian Kraus

Proceedings Volume 11445, 114455G (2020) https://doi.org/10.1117/12.2562429

KEYWORDS: Structural design, Telescopes, Optical instrument design, Large telescopes, Mid-IR, Mirrors, Buildings

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The Main Structure (MS) of the Extremely Large Telescope (ELT) is a 40 m class optical, near and mid-infrared telescope, under construction at Cerro Armazones, in the Chilean Andes. The MS is characterized by an Alt-Azimuth mounting weighting about 3700 t. It is divided in three major sub-systems: the Azimuth tracks, fixed to a concrete pier, which sustain the whole telescope weight; the Azimuth Structure, which allows the rotation around the vertical axis and sustain the Altitude Structure; the Altitude Structure, which allows the rotation around the horizontal axis. The MS consists in a steel space-frame structure, highly optimized to guarantee dynamical requirements and system level performances in general, not least pointing stability and tracking capabilities, reducing the rotating mass as much as possible. A fundamental design constraint has been the need for minimizing repeatable and non-repeatable deflections, particularly for the Altitude Structure, that hosts the segmented M1 mirror unit and all the main optics. Care has also been taken to guarantee survival conditions, particularly in the design of an effective seismic isolation system, capable to adequately limit Hosted Units (HU) accelerations and deformations. Finally, the major design challenge, in general, has been the need to design the system, having its overall dimensions and masses characteristics of large civil structures, like modern steel buildings and sports arenas, in order to be compatible with the strict requirements typical of extremely high precision machines and telescopes.

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