Bridge Railing Research for Local Bridges

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Steven Byrd
6 years ago
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Safety Facility University of Nebraska-Lincoln

1 Bridge Railing Research for Local Bridges Scott Rosenbaugh Research Engineer Midwest Roadside Safety Facility University of Nebraska-Lincoln 2017 Nebraska Bridge Conference Kearney, NE

2 Background and Scope Bill LB960 : Transportation Innovation Act County bridge match assistance program to aid in replacing deteriorated bridges NDOR wants to ensure safe rails installed with new bridges Crashworthy Bridge Railing Rural, 2-Lane Bridges Vehicles / Day 2

3 Existing Bridge Rails Installations 3

4 Rural Bridge Rails No Anchorage no rail tension Blunt Rail Ends spearing No Length of Need hazard not protected Large Posts snagging potential 4

5 Anchorage Guardrail Performance Mechanisms Post bending / rotating Rail tension, membrane action 5

6 Guardrail Anchorage 6

7 Anchorage Failure Good Anchorage Anchorage Failure 7

8 Guardrail Anchorage Anchorage Required to Develop Tension in Rail and Membrane Action Typical Cable Anchorage Anchor Cable Breakaway Posts Strut Steel Foundation Tubes 8

9 Guardrail Ends Rounded Ends are Not Crashworthy Untreated Ends Will Spear Vehicle 9

10 Guardrail Spearing Vehicles 10

11 Guardrail Spearing Vehicles 11

12 Guardrail Ends Safe Installations Place away from road (outside clear zone) Utilize crashworthy end treatments 12

13 Length of Need 13

14 No Length of Need Hazard Not Protected 14

15 Vehicle-Post Snagging Vehicle Bumper and/or Tire High Magnitude Forces and Accelerations 15

16 Vehicle-Post Snagging W6x9 Posts 16

17 Vehicle-Post Snagging W6x9 Posts W6x15 Posts 17

5 @75 c-c Many bridge rails utilizing larger posts

18 Vehicle-Post Snagging Generally not an issue with standard guardrail posts and spacing W6x9 or c-c Many bridge rails utilizing larger posts W6x20, W6x25, W8x24 Without blockouts Likely snag hazards 18

19 Rural Bridge Rails No Anchorage no rail tension Blunt Rail Ends spearing No Length of Need hazard not protected Large Posts snagging potential 19

20 NDOR Project, NTRC No. SG-05 Title Cost Efficient, TL-2 Bridge Rail for Low Volume Roads Objective Develop an Optimized Bridge Railing MASH TL-2 compliant Side mounted posts Minimize costs (material and labor) Prevent deck damage during impacts Minimize length of need 20

21 MASH* TL-2 Impact Conditions *Manual for Assessing Safety Hardware (MASH) Test No Vehicle 1100C Small Car 2270P Pickup Truck Speed (mph) Angle (deg)

22 MGS Bridge Rail MASH TL-3 W-Beam Rail Side-Mounted Sockets S3x Non-Blocked 22

23 MASH Test 3-11: 62 mph & 25 23

24 MASH Test 3-10: 62 mph & 25 24

25 MGS Bridge Rail Welded Standoff Plates - Better Fit in Socket - Post Tearing - Prevent Snag 25

26 MGS Bridge Rail 12 Backup Plates (W-beam) at all posts Prevents Rail Tearing 26

27 MGS Bridge Rail MASH TL-3 Weak Posts S3x5.7 Limit load into deck Reduces snag risks Rapid Repairs Sockets undamaged during impacts Pull out damaged posts and drop in new ones Directly Connects to Adjacent MGS No need for approach transition 27

28 NDOR TL-2 Bridge Rail Based TL-3 MGS Bridge Rail W-beam Guardrail w/ 12 Backup Plates S3x5.7 Posts increase spacing to 75 Directly Connects to Adjacent MGS Applicable for C.I.P. or Precast Decks Post-to-Deck Attachment - TBD 28

29 Schedule (Tentative) Project Began February 2017 Post Attachment Designs May 2107 Component Testing August 2017 Full-Scale Testing December 2017 Length of Need Analysis March 2017 Project Closes August

30 Questions 30

Guardrail Design. Licking County Engineer s Office April 16, 2014

Guardrail Design. Licking County Engineer s Office April 16, 2014 Roadside Design Guardrail Design Licking County Engineer s Office April 16, 2014 Roadside Design National Roadside Fatalities (Most Harmful Event) Other 20% Trees 50% Barriers 8% Utility Embankment and