1. Session 9 Guardrail Attachments to Bridge Ends
A very good bridge end connection on an APD Route in beautiful Easter KY

2. Common Deficiencies in Bridge Railings
Inadequate Dynamic Strength
Potential for Snagging
Use of “Safety” Walk
Inadequate Transition
What common problems do we see in railings? To much deflection in the approach rail. The open face causes wheel snagging. The safety walk isn’t really “safe” and often causes vaulting. The transition and structural connections are usually inadequate also.

3. Transitions Guardrail Deflects – Bridge Ends DONOT!!
Bridge End Connections are an example of a change in the type of Barrier Deflection Characteristics
Must Reduce the Deflection of the Guardrail before you reach the Bridge End from 3’ to Zero
Must have adequate Structural Connection
When there is a change in the type of barrier deflection characteristics, particularly when going to a stiffer system, a transition is required. The most common example of this situation is a semi-flexible (3’ deflection) approach barrier connected to a solid bridge end (0’ deflection).

4. Transition Considerations
Adequate structural connection to the bridge railing
Reduced post spacing and nested rail to increase stiffness gradually
Block outs and rub rails used to minimize snagging
The transition between the bridge rail and guardrail is critical. These features are key to a good design

5. How can you REDUCE DEFLECTION of Standard Strong Post W-Beam Guardrail
Normal Guardrail Post Spacing is 6’3”
Reduce Post Spacing to 3’ 1½” and reduce deflection by 50%
Nest the Guardrail (double thickness) and reduce deflection by 50%
Add a Guardrail panel to the back of the Post and reduce deflection by 50%
Add a Rub Rail and reduce deflection by nearly 50% & reduce snagging potential
Combine 2 of the above and reduce deflection by 75%
Remember this slide from the Guardrail Section??

6. How can you REDUCE DEFLECTION of Standard Strong Post W-Beam Guardrail
Spacing
Nested
At Bridge approaches deflection is reduced by reducing Post Spacing to 3’ 1 ½” and reducing again to 1’ 6 ¾”. Nesting (2 Ply) the rail. Also a rub rail is added to reduce deflection and help prevent the right front tire from snagging on the bridge end.

7. Gradually Increase Stiffness by Increasing the number of Post
The key to a successful transition design is to reduce the deflection of the approach guardrail uniformly until it is near zero at the end of the bridge.
This is usually done by using more posts spaced closer together, using longer post, nesting rail and adding rub rail.
Often, all of these changes are incorporated into a single transition design. It generally takes nearly 30’ of transition to go from 3’ to 0 deflection.

8. Rub Rail Components - Std Draw RBC & 003 “Guardrail Connection to Bridge End Type A and A-1 Components”
To keep the vehicle wheels away from the end of a rigid bridge railing, the rail must be positioned away from any likely snag points. Offset Blocks separate the guardrail from the guardrail posts, and with a w-beam, the lower rub rail keeps cars away from the lower face of the concrete parapet. The direction of the overlap where the w-beam is bolted to the terminal connector is also critical to minimize any snagging potential. Rub Rail Components - Std Draw RBC-002 & 003 “Guardrail Connection to Bridge End Type A and A-1 Components”
Rub
Rail
Not Island
Curb
Rub Rail

9. Standard Drawing RBC-001 Guardrail Connector to Bridge End Type A and A-1

10. Inadequate Structural Connection or Stiffening of Approach Rail

11. Adequate Structural Connection Terminal Sect No 2 Plate A & B
Terminal Section NO 2.and Connections completely through the concrete with a back up plate (Plate A)and beveled washers.
Use a similar plate for the rub rail connection (Plate B).
Rub Rail Components Plates see - Std Draw RBC-002 & 003 “Guardrail Connection to Bridge End Type A and A-1 Components”

12. Inadequate Reduction in Deflection and Structural Connection
Because of inadequate reduction in the deflection of the guardrail before it got to the bridge and because the structural connection to the bridge was inadequate - the combination resulted in a fatality.

13. Transition of Curb and Rub Rail to Bridge’s Safety Shape
Exit End of 2 Lane Bridge

14. Addition of a Spacer Tube
The last item that helps keep an impacting vehicle from coming in contact with the Bridge End is the Spacer Tube.

15. Combination of all of the Proceeding for a Successful Transition
Reduced post spacing
Nested – 2 Ply Rail
Rub Rail
Spacer Tube
Plates
Island Curb – Transition to Safety Shape

16. Std Draw RBC-001 Guardrail Connection to Bridge End Type A and A-1
Reduced Post spacing 3’1 ½” and 1’6 ¾”
2 - 8’ W8 x 21 steel post
25’ W-Beam Guardrail (Single Face) 2 Ply
C6x8.2 Rub Rail
6” ID x 9” Steel Spacer Tube
Island Curb
Curb Box Inlet Type B
Terminal Sect No 2 Std Draw RBR-010
Plate A & Plate B
Also Note 5 Island Curb

17. Curb Inlet Type B Should have Island Curb in Throat of the Inlet
Std Draw RBD-280
“Match Adjacent Curb”
Std Draw RBC-001 Note 5 “Island Curb”
Std Draw RBC-001 Note 5 calls for a “Island Curb” Transition from Island Curb Shape to Shape on Bridge within 7’ 3”. See previous slide for full note if needed.
Std Draw RBD-280 ‘
“Match Adjacent Curb”

18. Curb Inlet Type B Should have Island Curb in Throat of the Inlet
Lt Std Draw RBD-280 Curb Box Inlet Type B (Detail Drawing) “Match Adjacent Curb”
Rt Std Draw RDB-281 Curb Box Inlet Type B (Steel Drawing) "Island Curb Detail”

19. Type B Drainage Box As-Builts vs
Type B Drainage Box As-Builts vs. Std Draw Construction memo No 5-11 July 6, 2011
Have not been getting Island Curb on Type B Inlet therefore a Const Memo was Issued
See Std Draw RBC-001, RBD-280, RBD-281 Previous Slides
Corrective Actions:
Retrofit by extending the double ply rail from 25 linear feet to 50 linear feet
Replace the drain box top with the correct one

20. Std Draw RDB-280 Curb Box Inlet Type B 2012 Design Changed Detail to Show Island Curb instead of Std Curb
Our THANKS to Design for changing this detail to an Island Curb.
Changed to
Island Curb

21. Normally getting Standard Curb instead of Island Curb

22. What makes this a good Guardrail Connection to Bridge End? Q & A Time
Reduced post spacing
Nested – 2 Ply Rail
Rub Rail
Spacer Tube
Plates
Island Curb Transition the Safety Shape on the Bridge - But no Curb Box Inlet Type B