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P. To check stiffness of a structure per EC8

To review the stiffness of a structure per Eurocode 8 requirements, use the following procedure.

This set of checks is to enables you to judge whether the stiffness characteristics of the structure meet the recommendations set by EC 8. This implementation will:
  1. Display the center of mass and center of stiffness graphically for each floor to inform you of some inherent eccentricities and their variation along the height of the building.
  2. Calculate the total stiffness of every story in each direction and provide you with a ratio of the stiffnesses in the two directions. This aides you to judge whether the structure conforms to the condition in EC8 that the stiffness should be similar in both directions.
  3. Check to see if there are any soft stories in the structure and will highlight them in the GUI. A soft story is defined as a story that has a stiffness in a particular direction that is less than 70% of the stiffness of the story above.
Note: An example demonstrating a soft story is included as C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Eur\Eurocode8_TestGeo_stiff.std.
  1. Select the EC8 Stiffness page in the Earthquake page control bar. The center of mass and center of stiffness are drawn at each floor level.
  2. For a particular floor, you can expand the entry in the Floors dialog to review the location of these items. The selected floor and centers of mass or stiffness are highlighted in the view area.
  3. The stiffness ratios are reported in the Storey Stiffness table for each floor as well as for the total structure.
  4. Any soft stories detected by the program are listed in the Soft Storey table.
Note: The stiffness of only the vertical elements are considered while working out the total stiffness of a story in a particular direction as the seismic loads are primarily resisted by the vertical elements in a structure.