Design Memorandum



TO:                  All Design Section Staff

FROM:            Bijan Khaleghi
DATE:             January 18, 2007
SUBJECT:       Simplified Wind Load


For the usual girder and slab bridges with less than 30 ft height above ground, the following simplified wind pressure on structure (WS), could be used in lieu of the general method described in LRFD Article 3.8.1.2:

  • 0.05 kip per square foot, transverse
  • 0.012 kip per square foot, longitudinal

Both forces shall be applied simultaneously.

For the usual girder and slab bridges with less than 30 ft height above ground, the following simplified wind pressure on vehicle (WL), could be used in lieu of the general method described in LRFD Article 3.8.1.3:

  • 0.10 kip per linear foot, transverse
  • 0.04 kip per linear foot, longitudinal

Both forces shall be applied simultaneously.


Background

The current LRFD wind load determination on structures and on vehicles is tedious and cumbersome. The simplifications to wind load on structures and on vehicles are taken from the AASHTO Standard specifications Article 3.15.2.1.3. However the maximum span length limit of 125 ft. is not carried from the AASHTO Standard Specifications to the proposed revisions. This simplified approach has been safely used for wind load determination over the years.

If you have any questions regarding this design issue, please contact Chyuan-Shen Lee at 705-7441 or Bijan Khaleghi at 705-7181.


cc:   Mohammad Sheikhizadeh, Bridge Construction - 47354

       F. Posner, Bridge and Structures – 47340