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TMT CAD model. The structures supporting the science instruments on the Nasmyth platforms are not shown.
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This paper documents the methods used for the seismic design and analysis of the Thirty Meter Telescope (TMT)2. The seismic analysis includes response spectrum and nonlinear time history methods. Several seismic restraint design options are considered, both linear and nonlinear, and the seismic performance is presented for these options. The paper...
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Structures consisting of concrete and steel parts, which are irregular in damping ratios are
investigated. This investigation is a code-based seismic design of such structures. Several practical
difficulties encountered, due to inherent differences in the nature of dynamic response of each part, and the
different damping ratios of the two parts. Th...
Citations
... Last but not least, site accessibility and seismic hazard parameters are also important considerations. The seismic hazard in particular, can play a crucial role in construction, operational as well as survival conditions of telescope both in structure and cost (e.g Tsang et al. 2008;Eff-Darwich et al. 2010;Usuda et al. 2014;Sugimoto et al. 2022). ...
A multiparameter analysis was conducted to e v aluate the impact of meteorological parameters, night sky brightness and seismic hazards on proposed sites for the new optical/infrared Egyptian astronomical telescope. The European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) data set is used to obtain the following meteorological parameters: total cloud co v erage fraction, precipitable water vapour, relative humidity, wind speed and direction, and air temperature. To estimate the aerosol optical depth, we used the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). Light pollution o v er the candidate sites was measured using the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band. In order to assess the seismic hazards for the candidate sites, the seismic input in terms of maximum acceleration and response spectra was computed using a physics-based ground motion approach to assess the seismic hazards and, consequently, the designation of a seismic-resistant structure for the proposed sites. Of the seven nominated sites, two sites are found to have the best measurements and might be considered as future sites for the new Egyptian astronomical telescope. The first site is located in the south of the Sinai peninsula, while the second site is located in the Red Sea mountains region.
... The working frequency of the TMT machine is 2 Hz. 27 To ensure a normal operation of the instrument and avoid any structural damage caused by resonance with the TMT machine, the fundamental frequency of the WFOS structure should not be less than two times that of the TMT machine. In summary, the following factors need to be mainly considered during design of the WFOS supporting structure: ...
Aiming at the issues of heavy weight and insufficient structural performance of optical instrument supporting structures in extremely large telescopes, the Wide-Field Optical Spectrograph (WFOS) of the Thirty Meter Telescope (TMT) was taken as a case to study. In order to develop lightweight structures which satisfies the design requirements for mass and stiffness, a design scheme of cylindrical composite shells supporting structure was proposed and their finite element models were developed. A size optimisation and a ply sequence optimisation of the composite structure were carried out. The structures before and after optimisation were evaluated from the aspects of mass, displacement, failure index and fundamental frequency. After the optimised design, the mass of the optimised WFOS cylindrical composite shell structure is reduced to approximately 50%, but its maximum displacement (0.513 mm) and fundamental frequency (8.275 Hz) are nearly unchanged. The study indicates that a cylindrical composite shell structure is an efficient structural form for large optical instruments.
... A comprehensive seismic analysis work is underway to support the seismic restraint design. The detailed description of the seismic analysis and design can be found in a related paper in this conference by Tsang et al [9] . ...
The Thirty Meter Telescope (TMT) project has revised the reference optical configuration from an Aplanatic Gregorian to a Ritchey-Chrétien design. This paper describes the revised telescope structural design and outlines the design methodology for achieving the dynamic performance requirements derived from the image jitter error budget. The usage of transfer function tools which incorporate the telescope structure system dynamic characteristics and the control system properties is described along with the optimization process for the integrated system. Progress on the structural design for seismic considerations is presented. Moreover, mechanical design progress on the mount control system hardware such as the hydrostatic bearings and drive motors, cable wraps and safety system hardware such as brakes and absorbers are also presented.
The Thirty Meter Telescope (TMT) Project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. TMT is a partnership between the University of California, Caltech, and the Association of Canadian Universities for Research in Astronomy (ACURA). The $80 million TMT design and development phase is fully funded and Preliminary Design is in progress. An additional $300 million has been pledged towards early TMT construction which will commence in 2009. We include a high level description of the design of the telescope and its planned adaptive optics and science instrumentation. The schedule of key milestones for completing the design and construction is summarized.
An analysis of the impact of seismic and volcanic activity has been carried out at selected astronomical sites, namely the
observatories of El Teide (Tenerife, Canary Islands), Roque de los Muchachos (La Palma, Canary Islands), Mauna Kea (Hawaii)
and Paranal (Chile), and the candidate site of Cerro Ventarrones (Chile). Hazard associated with volcanic activity is low
or negligible at all sites, whereas seismic hazard is very high in Chile and Hawaii. The lowest geological hazard in both
seismic and volcanic activity is found at Roque de los Muchachos observatory, on the island of La Palma.
The VST (VLT Survey Telescope) is a wide field survey telescope going to be commissioned at Cerro Paranal (Chile). Due to
the geological nature of the area, telescopes in Chile can be submitted to unpredictable and sometimes severe earthquake conditions.
The commonly used response spectrum analysis has proven to be not suitable to evaluate the behavior of the VST telescope during
an earthquake, due to the high number of devices with a nonlinear force–displacement characteristic in the primary mirror
cell. Therefore, a nonlinear transient analysis based on a mixed Finite Element-Simulink approach has been carried out. A
linear Finite Element (FE) model of the telescope has been developed and exported to Simulink, using a space state model representation.
Then all nonlinear devices have been properly modeled and artificial accelerograms based on seismic history of the site have
been applied. The paper focuses on the Simulink model, while giving an overview of the whole procedure.
KeywordsTelescope–Finite elements–Earthquake analysis–Matlab
