Session 7
This presentation is the property of its rightful owner.
Sponsored Links
1 / 68

Session 7 PowerPoint PPT Presentation


  • 72 Views
  • Uploaded on
  • Presentation posted in: General

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.

Download Presentation

Session 7

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Session 7

Session 7

Guardrail End Treatments (Terminals)


Session 7 outcomes

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

Purpose of an End Treatment

If hit, minimize the damage to the vehicle and its occupants

Develop the necessary TENSION of the guardrail system


Session 7

7-4


Session 7

Results with a Stand-Up Blunt End


Cable barrier end treatment

Cable Barrier End Treatment

Use 350 accepted end treatment

(Large concrete block to develop tension, quick release to allow downstream release)


Session 7

350 Approved Generic Cable Terminal

(AASHTO RDG)


Weak post w beam terminals

Weak Post W-Beam Terminals

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


Session 7

(AASHTO RDG)


Session 7

Single Rail Buried-in-Backslope (BIB) Terminal


Session 7

V


Session 7

V


Session 7

Double Rail Buried-in-Backslope (BIB) Terminal


Session 7

Exposed Three Steel Post Anchor


Session 7

BIB Looking Across Roadway


Session 7

What do you see here?


Length of need lon for bib

Length of Need (LON) for BIB

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


Details for bib installation double rail

Details for BIB Installation(double rail)

  • Top of rail parallel to roadway

  • Anchorage: 50’ upstream of Point Of Effectiveness (POE), ONE FOOT under existing ground

  • 75’ minimum downstream of POE to hazard

  • Sharpest flare rate 12 ½:1 (high speed)


Session 7

V


Session 7

A Stand-Up End Treatment


Session 7

V


Session 7

7-22


Session 7

7-23


Session 7

Slot Guard Position

7-24


Session 7

7-25


Session 7

Available Runout - ???


Session 7

Recent Installation: Available Runout - ???

7-27


Session 7

V


Session 7

SKT (Sequentially Kinking Terminal)

7-29


Session 7

SKT Sequential Kinking Terminal

FHWA Acceptance Letter CC-61

Date; August 27, 1999

Test Level 3 Tangent Terminal

All Plug-Welded Steel Post Option

Plug-Welded Post Option


Session 7

SKT - Plug-Welded Post Option


Session 7

ET – Steel Post (SYTP) Option

7-33


Steel post sytp option close up

Steel Post SYTP OptionClose-up


Session 7

Typical State Standard for Parallel Terminal

7-35


Session 7

Typical Impact Head


Session 7

Impact Head and Rail – A Fatal Flaw


Session 7

Impact Head at Post 1

Improper Installation

or Application…


Session 7

MUST HAVE MANUFACTURER’S SHOP DRAWINGS AND INSTALLATION MANUAL TO INSTALL / INSPECT ANY OF THE PROPRIETARY END TREATMENTS


Characteristics of a breakaway cable anchorage bca

Characteristics of a Breakaway Cable Anchorage (BCA)

Transfer of rail tension to the foundation


Session 7

For Energy Absorbing Heads, the Cable Anchor Bracket MUST Release SKT

7-41


For energy absorbing heads the cable anchor bracket must release et

For Energy Absorbing Heads, the Cable Anchor Bracket MUST Release ET


Characteristics of a breakaway cable anchorage cont

Characteristics of a Breakaway Cable Anchorage (cont.)

Bearing plate

Proper orientation – needs to be restrained (nail or strap)

Must not be buried


Session 7

Bearing Plate on Steel Post

7-44


Characteristics of a breakaway cable anchorage cont1

Characteristics of a Breakaway Cable Anchorage (cont.)

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


Top of a steel post 1

Top of a Steel Post 1


Characteristics of a breakaway cable anchorage cont2

Characteristics of a Breakaway Cable Anchorage (cont.)

BUT…

Strut distributes tension between first TWO posts - type is inconsequential


Session 7

Characteristics of a Breakaway Cable Anchorage (cont.)

Cable – taut (no more than 1” uplift)


No obstacle less than 75 downstream from any terminal end delineator

No obstacle less than 75’ downstream from any terminal end (delineator)


Session 7

“Safety” Treatment for Median Structure


Session 7

V


Session 7

CAT(Crash Attenuating Terminal)

7-52


Session 7

Double Side Terminal in Median on Single Side Barrier


Session 7

Terminal Treatment with Curb


Session 7

Downstream End of Barrier

LENGTH OF NEED

7-56


Session 7

Downstream Terminal


Session 7

Grading


Session 7

AASHTO RDG


Stub height criteria

Stub Height Criteria

Stub

4” max.

5 feet

Figure 4.1 (AASHTO RDG)


Telltales of poor terminal grading

Telltales of Poor Terminal Grading

More than 1-2” of air under strut (ideal on the ground)

Soil plate showing

Tube/post more than 4” above ground


Session 7

Grading at Terminal

7-62


Session 7

Gap Between Guardrail Runs

7-63


Gaps in runs of barrier

Gaps in Runs of Barrier

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)


Session 7 review

Session 7 Review

Which of the following characteristics describe the BIB end treatment?

  • It will always work whenever and wherever it is hit

  • It is very inexpensive to install

  • It is less likely to get impacted because it is farther away from traffic

  • It can be installed on frontslopes as steep as 4:1


Session 7 review1

Session 7 Review

All of the energy-absorbing end treatments we have discussed are non-gating systems.

  • True

  • False


Session 7 review2

Session 7 Review

Desirable grading for all the end treatments include:

  • 6:1 grading in front of and extending at least 3’ behind post #1

  • 10:1 grading in front of and extending at least 6” behind post #1

  • 10:1 grading in front of and extending desirably 5’ behind post #1

  • Grading doesn’t affect the performance of the end treatment


Session 7 outcomes1

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


  • Login