Footfall analysis

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Use Footfall analysis to evaluate vibration response of structures subjected to walking-induced dynamic loading.

• Top of substructure – elevation below which masses are ignored in the eigenfrequency calculation used by footfall analysis
• Setup… – opens the Footfall analysis options dialogue

Footfall analysis options

The options are arranged into three sections: Method, Frequency data, and Fourier coefficients.

Method

• Method – drop-down menu with three choices. The layout of the dialogue changes depending on the selected option:

  • Self excitation – uses individual walker parameters
  • Full excitation – uses the same input fields as Self excitation
  • Rhythmic crowd load – replaces the input fields with a load case table

When Self excitation or Full excitation method is selected, these options become available:

• Number of footsteps – number of steps considered in the excitation
• Walker’s mass – mass of the person causing the vibration
• Frequency weight – weighting function used in comfort evaluation (for example Wg)

When Rhythmic crowd load method is selected, these options are replaced with a table.

• Load cases table – lists all load cases in the model
• Sel – select which load cases participate in the rhythmic crowd excitation

Frequency data

• Minimum frequency – start of the frequency range
• Maximum frequency – end of the frequency range
• Frequency steps – number of steps between minimum and maximum frequency
• Cut-off eigenfrequency – limit above which eigenmodes are ignored
• Damping factor – structural damping expressed as a percentage

Fourier coefficients

• Fourier coefficients – drop-down menu selecting the source of harmonic coefficients. The available options are:
  • User defined coefficients – enables a table where harmonic values can be entered manually
  • SCI P354 table 3.1 – uses predefined coefficients
  • SCI P354 formula 20 – uses formula-based coefficients
  • The Concrete Centre table 4.3 – uses predefined coefficients
  • According to Danish Annex – shows additional parameters for the Danish national annex ([G1]DS/EN 1990 DK NA:2024)

When User defined coefficients is selected:

• H / Coeff. table – manually enter harmonic numbers and their corresponding coefficients

When SCI P354 formula 20 is selected:

• Number of walkers – numeric field defining the number of walkers used in the formula

When According to Danish Annex is selected:

• Effective number of people – numeric field defining the number of people generating the excitation
• Activity – choose the type of activity for the excitation
  • Possibility to move about freely
  • Reduced possibility to move about
  • Walking