Session 7. Guardrail End Treatments (Terminals). Session 7 Outcomes. Describe the Tests Required for Acceptance Explain How the Various Systems Function Describe How a Breakaway Cable Anchorage Functions Identify the Aspects of Proper Site Grading. Purpose of an End Treatment.
Guardrail End Treatments (Terminals)
If hit, minimize the damage to the vehicle and its occupants
Develop the necessary TENSION of the guardrail system
Use 350 accepted end treatment
(Large concrete block to develop tension, quick release to allow downstream release)
There is no approved approach terminal
Solution – use 50’ of standard strong post W-beam next to strong post terminal (with transition if necessary)
Downstream, run-off side – can use turndown to develop tension
If backslope is very steep (1:1 or steeper), anchor the barrier in as short a distance as possible; a rock anchor may be appropriate.
If backslope is 2 1/2:1 or flatter, calculate using AASHTO procedure or LON = 450 – 15 x OFF, where OFF is the lateral distance from the Edge of Travel Way (EOTW) to the toe of backslope.
Min 75’ (excluding #1 above)
Suggestion: Do not use BIB when backslope is 2 1/2:1 or flatter if toe of slope is less than 20’(?) from edgeline
FHWA Acceptance Letter CC-61
Date; August 27, 1999
Test Level 3 Tangent Terminal
All Plug-Welded Steel Post Option
Plug-Welded Post Option
Transfer of rail tension to the foundation
Proper orientation – needs to be restrained (nail or strap)
Must not be buried
Develop soil resistance to tension
For Wood Posts - Short Wood Post Set in short tubes with soil plates or in long tubes
For Steel Posts – per Manufacturer’s Specifications
Top of Post 1 MUST Separate from Base
Strut distributes tension between first TWO posts - type is inconsequential
Cable – taut (no more than 1” uplift)
LENGTH OF NEED
Figure 4.1 (AASHTO RDG)
More than 1-2” of air under strut (ideal on the ground)
Soil plate showing
Tube/post more than 4” above ground
Generally, if there is less than 200’ between successive runs of guardrail and no obvious reason for the break, the barrier is made continuous. (Check with maintenance)
Which of the following characteristics describe the BIB end treatment?
All of the energy-absorbing end treatments we have discussed are non-gating systems.
Desirable grading for all the end treatments include: