Gravity Analysis Parameters

Gravity analysis is a simplified analysis. By deducing the flow paths of loads it lets you determine how vertical loads are transmitted from the top to the foundation of the model.

To perform the gravity analysis of a model, specify the following parameters:

• Live load reduction code. Select one of the following options:
  • Do not reduce

    If you select this option, the live load reduction is not calculated and the Live load type option is disabled.

  • NBC of Canada
  • ASCE/SEI 7
  • IBC.
• Live load type

  Select a live load type that best matches live load cases in the analyzed model. The live load type determines the live load reduction scheme assumed in the analysis.

  If you selected the NBC of Canada code, the following live load types are available:

  • Reducible A

    The live load reduction pattern is assumed for the tributary area A > 80m2. Code reference: NBCC 2010, section 4.1.5.8.(2)

  • Reducible B

    The live load reduction pattern is assumed for the tributary area B > 20m2. Code reference: NBCC 2010, section 4.1.5.8.(3)

  • Irreducible

    Live load reduction is not performed for this load type. This is a default setting if you select NBC of Canada.

  If you selected the ASCE/SEI 7 code, the following live load types are available:

  • Reducible

    The basic live load reduction scheme is assumed. Loads that exceed 100 psf (4.79 kN/m2) are reduced as heavy loads. Code reference: ASCE/SEI 7‑10, section 4.7.2.

  • Storage

    The heavy live load reduction scheme is assumed, regardless of the actual load value. Code reference: ASCE/SEI 7‑10, section 4.7.4.

  • Roof

    The roof live load reduction scheme is assumed. Code reference: ASCE/SEI 7‑10, section 4.8.2.

  • Irreducible.

    Live load reduction is not performed for this load type.

  If you selected the IBC code, the following live load types are available:

  • Reducible.

    The basic live load reduction scheme is assumed. Loads that exceed 100 psf (4.79 kN/m2) are reduced as heavy loads. Code reference: IBC 2012, section 1607.10.1.

  • Storage.

    The heavy live load reduction scheme is assumed, regardless of the actual load value. Code reference: IBC 2012, sections 1607.10.1.2 and 1607.1.3.

  • Roof.

    The roof live load reduction scheme is assumed. Code reference: IBC 2012, section1607.12.2.1.

  • Irreducible.

    Live load reduction is not performed for this load type.

• Wall load dispersion angle

  This is an angle of dispersion of a concentrated load from the vertical. It may vary from 0 to 60 degrees. This value is common for all solid walls in a model.