KEYWORDS: Telescopes, 3D modeling, Finite element methods, Systems modeling, Buildings, Fluctuations and noise, Motion models, Astronomical telescopes, Astronomy, Thirty Meter Telescope
Telescope-Enclosure-Soil Interaction could result in additional telescope movement due to two main sources: (i)
enclosure windshake and (ii) vibrations of machinery located at enclosure, summit and utility facilities. To analyze and
minimize these vibrations, a novel FE model was developed based on existing FE models for the TMT enclosure and
telescope structures. This integrated structural model adequately represents propagation of vibrations from the source to
the telescope structure through surrounding soil/rock region. The model employs 3-D linear-elastic harmonic analysis
using commercial FE code ANSYS. Special attention was devoted to adequate modeling of reflecting and non-reflecting
boundary conditions. Based on the FE model developed, we examined the effects of soil/rock stiffness and damping
upon telescope vibrations and, ultimately, seeing quality. The effects of location, intensity and spectral content of main
sources of machinery vibrations were also investigated.
KEYWORDS: Telescopes, Optical instrument design, Earthquakes, Mirrors, Systems modeling, Space telescopes, Astronomy, Finite element methods, Complex systems, Thirty Meter Telescope
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
addresses several issues specific to large optical telescope seismic design and analysis: generation of appropriate
response spectra and time histories; use of operational and survival level earthquakes; selection of damping coefficients;
use of reduced degree of freedom models and their calibration with more detailed models; and local response spectra for
telescope-mounted systems.
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