Earthquake safety system design for a telescope primary mirror

Perrotta, Francesco

doi:10.1117/12.789088

Cited by 2 publications

(5 citation statements)

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“…As can be seen, mirror displacements are less that 3 mm along X direction and less than 1 mm along Y: the astatic levers system makes the mirror very dynamically stable along Y. The results are in good agreement with those computed with a simpler approach [10]. Another result are the maximum forces exerted by each radial safety device during the earthquake event, shown in Fig.…”

Section: Simulation Resultssupporting

confidence: 82%

“…These are the modes corresponding cumulatively to more than 90% of modal masses along z, x, y direction, giving a response up to 150 Hz. According to Paranal response spectrum, Maximum Likely Earthquake (MLE) highest significant frequency is about 40 Hz [10].…”

Section: Space State Transformationmentioning

confidence: 99%

“…It this context, it has been assumed that no damage can be acceptable for the primary mirror of the VST, even in case of Maximum Likely Earthquake, the most severe earthquake considered in the design phase [10]. Independently of the actual safety/restraint system introduced for the primary mirror, the study of the performances of a telescope structure under seismic loads can be essentially performed using one of the following approaches, in order of complexity, (1) equivalent static procedure, (2) Response Spectrum Analysis (RSA), (3) time history (transient) linear and nonlinear analysis.…”

mentioning

confidence: 99%

“…A preliminary RSA followed by simplified transient computations has been carried out for the VST [10]. After the evaluation of results, the need for a more detailed and comprehensive analysis has arisen.…”

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confidence: 99%

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A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

Perrotta

Schipani

2011

Exp Astron

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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 ElementSimulink 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.

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Section: Simulation Resultssupporting

confidence: 82%

Section: Space State Transformationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

Perrotta

Schipani

2011

Exp Astron

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“…This has also been done initially for the VST telescope. However, after careful examination of RSA results and the implementation of a simplified nonlinear transient model [2] , it has been decided to perform a nonlinear transient analysis of the whole telescope with the aim to clarify some aspects of VST telescope peculiar dynamics not well represented by linear procedures.…”

Section: Introductionmentioning

confidence: 99%

The VST telescope primary mirror safety system: simulation model and mechanical implementation

et al. 2010

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The VST telescope is a wide field survey telescope being installed at Cerro Paranal (Chile). Due to the geological nature of the area, telescopes in Chile are always submitted to unpredictable and sometimes severe earthquake conditions. In order to clarify some aspects of VST telescope seismic behavior not well represented by linear procedures like Response Spectrum Analysis, a transient nonlinear analysis of the whole telescope has been foreseen. A mixed approach Finite Element -Matlab-Simulink has been introduced and a linear FE model of the telescope has been developed, with all nonlinear devices sources modelled as linear elements. The FE model has been exported to Simulink, using a space state representation. In Simulink all nonlinearities are appropriately modeled and a base excitement corresponding to accelerograms compliant with Paranal MLE response spectrum is applied. Resulting force-time histories are then applied to a detailed finite element model of mirror, to compute stress field. The paper describes both Simulink and mirror FE analysis, giving also an overview of the actual safety system mechanical implementation, based on analysis results.

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Earthquake safety system design for a telescope primary mirror

Cited by 2 publications

References 0 publications

A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

The VST telescope primary mirror safety system: simulation model and mechanical implementation

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