|TO:||Bridge & Structures Office Design Staff|
|DATE:||December 4, 2001|
|SUBJECT:||LRFD Wingwall Design|
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)
Ft = transverse collision impact force, kips
Lt = longitudinal length of distribution of impact load, ft
H = height of traffic barrier, ft
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.
cc: J. Weigel, Bridge and Structures - 47340
F. Higgins, Bridge and Structres - 47340