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Response spectra

Basic definition

Name​

The name is used only as a label for the response spectrum.

Spectrum type​

The user has a choice of the type of spectrum to use. This can be code defined to one of

  • ASCE 7-05
  • ASCE 7-10
  • AS 1170-2007
  • Eurocode 8 : 1994
  • Eurocode 8 : 2003 (draft)
  • Eurocode 8 : 2004
  • FEMA 356
  • GB 50011-2001
  • GB 50011-2010
  • IBC 2000
  • IBC 2006 (ASCE 7-05)
  • IBC 2009 (ASCE 7-05)
  • IBC 2015 (ASCE 7-10)
  • IS 1893 (Part 1) : 2002
  • Ordinanza PCM 3274
  • NBCC 2015
  • UBC 1994
  • UBC 1997

or

  • User defined

Depending on the spectrum type a different set of information is required to define the spectrum. The spectra are defined via the Response Spectrum Wizard.

Response spectrum wizard​

The wizard takes the user through the following steps.

  • Select spectrum type

For code spectra

  • Code specific data to define spectrum
  • Derived code specific values
  • Damping associated with the spectrum
  • Spectrum values

For user defined spectra

  • Spectrum values

Damping​

CQC and other double sum combination methods require a damping value to establish the coupling coefficients between modal responses. The default option is constant 5% damping, but this can be changed to code specified damping, modal damping values or a table of damping values.

No adjustment from code
Newmark-Hall : 50th percentile
Newmark-Hall : 84th percentile
ISO 19901-2ln⁡(100/η)/ln⁡(20)\ln( 100 / \eta) / \ln (20)
Eurocode 810/(5+η)\sqrt{10/(5+\eta)}