Memorandum

 The design of bridge wingwalls should be in accordance with the requirements of the AASHTO-LRFD Specifications Table A13.2-1 “Design Forces for Traffic Railings”.  The design shall be based on the extreme-event-II limit state with transverse truck collision force of 54 kips distributed over 3.5 ft (TL-4 design force for 34 in. single slope and 32 in. type-F traffic barriers commonly used in WSDOT bridges).  This results in a wall thickness of 12 in. for 15 ft wingwalls and 20 ft wingwalls associated with both L-shaped and stub abutments.  The reinforcing bar size and spacing are detailed in the wingwall standards with reinforcement placed in the horizontal and vertical directions.  The flexural moment at the traffic barrier to wingwall connection may be taken as:

                               (Flexural moment per foot)

      Where: 

Ft =      transverse collision impact force, kips

L_t =      longitudinal length of distribution of impact load, ft

H =      height of traffic barrier, ft

 Background:

The traffic barrier and wingwall connection is not crash tested yet.  The current wingwall standards conform to the LFD specifications. However, for consistency in design with other bridge components, wingwalls should be designed in accordance with the requirements of the AASHTO LRFD Specification Table A13.2-1. The yield line theory as specified in AASHTO LRFD Specifications article A13.3 is primarily for traffic barrier on bridge deck slabs and is not applicable to traffic barrier on wingwall. 

  Standard plans for wingwalls are now available in M:/BRIDGELIB/Master6/Standards\Walls\Wing Walls and will be soon published in the BDM.

  If you have any questions, please contact Gary Battin at 705-7188 for standard plans and Bijan Khaleghi at 705-7181 for other issues.

JK:dm

BK

cc:              J. Weigel, Bridge and Structures - 47340

                  F. Higgins, Bridge and Structres -  47340