Template > Response Spectrum AASHTO LRFD 2012

Generation of the elastic seismic response spectrum according to AASHTO LRFD 2012, 3.10

Setting

Description

Site Class

Site class according to Article 3.10.3.1 (A to F, where F can be used for any user-defined values for defining the Site Factors)

Coefficients

User input of the acceleration coefficients according to 3.10.2.1

Setting	Description
PGA (-)	Numerical value of the peak ground acceleration coefficient (dimensionless)
Ss (-)	Numerical value of the short-period spectral acceleration coefficient (dimensionless)
S1 (-)	Numerical value of the long-period spectral acceleration coefficient (dimensionless)

Site Factors

The site factors are automatically filled according to 3.10.3.2 from the selection of the Site Class and the input of the acceleration Coefficients.

Selecting Site Class F allows for any user-defined input for the Site Factors.

Setting	Description
Fpga (-)	Site factor for the peak ground acceleration coefficient PGA (dimensionless)
Fa (-)	Site factor for the short-period spectral acceleration coefficient Ss (dimensionless)
Fv (-)	Site factor for the long-period spectral acceleration coefficient S1 (dimensionless)

Design Values (non editable)

The design values describing the response spectrum are automatically calculated by multiplying the Coefficients with the Site Factors.

Setting	Description
As	Design value of the peak ground acceleration coefficient PGA (dimensionless)
Sds	Design value of the short-period spectral acceleration coefficient Ss (dimensionless)
Sd1	Design value of the long-period spectral acceleration coefficient S1 (dimensionless)

Output variable

Name of the variable that describes the response spectrum

The default name will be set up as LRFD12_Csm. A two-digit alpha-numeric suffix (Variable postfix) can be added to that name (e.g. in case that more than one response spectrum is generated to not overwrite the existing ones).

The variable (and the related variables, formulas and tables) is stored in Properties > Variables and can be used when defining the earthquake load (Schedule > Load Definition > Earthquake Load).

The variable describing the response spectrum will be given in terms of Csm (-) as a function of the period Tm (s).

Since Csm contains the ground acceleration related to the gravitation acceleration (ag/g), the ground accelerations value (g = 9.81 m/s2) must be considered when defining the vectors within the earthquake load definition; i.e.:

Csm (ag/g) [-] -> Earthquake load: Csm (ag/g) * g = Csm (ag) [m/s2]