This chapter provides an outline of the definitions, standards, and procedures you need to know when

1
GuardrailTerminals

• This chapter provides an outline of the
  definitions, standards, and procedures you need
  to know when selecting the necessary type
  terminals.
• The chapters topics are
• Weak Post Terminals
• Strong Post Terminals
• Gaps Between Guardrail Runs

2
CHAPTER 9 OBJECTIVES

• You will be able to perform the following tasks
  after finishing this chapter
• list the methods for terminating a guardrail
  system
• describe the standards for these methods
• list the reasons for selecting a given type of
  terminal

3
GUARDRAIL TERMINALS

• The main purposes of a terminal are to help
• reduce serious injuries to a vehicle's occupant
• and minimize vehicle damage.
• You will ensure a terminal will achieve this by
• installing it as tested and approved under NCHRP
  350 test criteria
• developing the necessary tension at the end of
  the system to redirect a vehicle or absorb energy

4
CURRENT WEBSITES

• All currently approved guardrail terminals can be
  found on these websites which cover NCHRP 350
  requirements
• http//Virginiadot.org/business/locdes/nchrp350-in
  dex.asp
• http//safety.fhwa.dot.gov/programs/roadside_hardw
  are.htm
• Manufacturers specific products with detailed
  descriptions and specifications are linked
  through the FHWA site.

5
WEAK POST CABLE SYSTEM(STD. GR-3 TERMINAL)
PLAN VIEW
ELEVATION

• The cables are tapered down to the ground at both
  ends and anchored in a concrete deadman under the
  current standard. The cables are preferably
  anchored in a back slope.
• The location of the terminal should be determined
  by the LON procedure.
• If the anchor is to be buried in the back slope,
  the full height of the barrier should be carried
  75 feet upstream of the hazard before flaring
  beyond the ditch line and tying into the concrete
  deadman.

CABLE GUARDRAIL TERMINAL 501.06
6
WEAK POST CABLE SYSTEM(STD. GR-3 TERMINAL)

• Constant tension is maintained in the cable
  system with springs as part of one anchor, and
  with turnbuckles to adjust the tension based on
  the ambient temperature at installation as
  required by VDOT specifications.

7
WEAK POST W-BEAM SYSTEM(STD. GR-8, TYPE II
TERMINAL)

• There is no NCHRP 350 approved run-on terminal
  for the weak post W-beam system (Std. GR-8) at
  this time.
• This turned-down anchorage which develops the
  necessary tension may be used on run-off
  locations for one-way traffic.
• Run-on conditions must include a strong post
  terminal and 50 feet of Std. GR-2 to transition
  to the weak post W-beam system.

TYPE II TERMINAL TREATMENT (RUN-OFF ANCHORAGE)
501.15
8
WEAK POST W-BEAM SYSTEM(STD. GR-8, TYPE II
TERMINAL)
This is the old GR-8 No picture was available for
the new installation
9
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• Use this standard when the front slope is 41
  Max. or flatter.
• Burying the guardrail end in a back slope is the
  most desirable method for terminating the
  guardrail system. The end cannot be hit directly
  if it is buried.

TERMINAL TREAMENT FOR W-BEAM GUARDRAIL 501.09
10
New GR-6 with Double Rail
11
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• When burying a terminal, you must

• provide the necessary anchorage to develop the
  required tension forces
• place it deep enough ( minimum) so that the end
  of the rail will not become exposed

• 1 foot

The next two slides show anchorage methods.
TERMINAL TREAMENT FOR W-BEAM GUARDRAIL 501.09
12
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• This anchoring method uses three 6 foot steel
  posts, spaced at 3' 1½" intervals, as the end
  anchor. Each post is attached to the guardrail
  by four bolts. Additionally, each post has bolted
  or welded steel plates attached.

END ANCHORAGE (POST) 501.10
13
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• This anchoring method uses concrete deadman,
  measuring 3' 2' 2', as the end anchor. The
  guardrail is attached to the deadman through a
  terminal connector by bolt anchors, which are
  either cast in-place or drilled.
• The end anchor must have a minimum of 1 foot of
  cover. The cover must be compacted on the same
  plane as the normal ground slope. No mounds or
  bubbles can be present after the ground has
  been tamped.

END ANCHORAGE (CONCRETE) 501.10
14
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• The height of the rail should be measured from
  the graded shoulder extended, when there is a
  ditch at the bottom of the front slope.
• The maximum distance from the ground line to the
  bottom of the W-beam rail is 18 inches.

TERMINAL TREATMENT FOR W-BEAM GUARDRAIL 501.09
15
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)
REMEMBER
The GR-6 can be installed using the TOP RAIL only
if the slopes and ditch dimensions warrant this.

• A bottom rail shall be added to the system when
  the height between the ground line and the bottom
  of the top rail exceeds 18 inches.

• Taper both W-beam rails down to maintain the 18
  inch height if the clearance under the bottom
  rail exceeds 18".

TERMINAL TREATMENT FOR W-BEAM GUARDRAIL 501.09
16
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• The posts must be 8 feet long when a bottom rail
  is used.

• The maximum exposure between the bottom rail and
  the groundline is 18 inches.

TERMINAL TREATMENT FOR W-BEAM GUARDRAIL 501.09
17
STRONG POST W-BEAM SYSTEM(STD. GR-6 BURIED IN
BACK SLOPE TERMINAL)

• Regardless of whether one or two rails are used,
  the flare must not cross the ditch bottom until
  it has extended a minimum of 75 feet upstream
  from the beginning of the hazard being shielded,
  or the cut to fill slope transition.

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IMPROPERLY INSTALLED EXAMPLE(STD. GR-6)

• This system has an improperly installed single
  rail GR-6 cut slope terminal. The end of the
  rail is exposed a vehicle would be speared if
  the end were hit directly. The standard calls
  for the rail to be anchored in the slope by
  having at least two posts buried a minimum
  of one foot in the ground.

19
See the results of a build up and a rain storm
soon there after. This terminal should have been
extended and buried deeper as the standards
indicate. NO MOUNDS keep the slopes the same.
20
(No Transcript)
21
Not a good example of the GR-6 installation. The
slope does not exist.
22
This location is not a good candidate for a GR-6.
Embankment not adequate, To me the GR should have
been extended to get the proper LON then install
a GR-9. They are trying to create an area that
does not exist.
23
IMPROPERLY INSTALLED EXAMPLE (STD. GR-6)

• The end of this terminal is buried under a
  bubble of soil. This mound of soil was piled on
  the terminal in order to meet the specification
  that the terminal be buried under a minimum of
  1 foot of soil. Bubbles or mounds are not
  acceptable. The soil can sluff down the slope
  or erode over time, thus exposing the terminal.

24
STRONG POST W-BEAM SYSTEMSITE PREPARATION
A key component to proper installation of
guardrail terminals is proper site preparation
25
STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)

• This terminal configuration is one which flares
  the end of the terminal away from the normal
  line of the barrier.
• Only a flare of 4 feet is acceptable under
  current standards.

BREAKAWAY CABLE TERMINAL 4' FLARE 501.11
26
This is a GR-7 Slotted Rail Terminal.
27
STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)
FLEAT
SRT-350

• A vehicle hitting the end of a flared terminal,
  either head-on or at an angle, will break away
  the end and pass through the guardrail with
  little absorption of energy.

• The FLEAT, however, absorbs the energy of a
  head-on impact.

• It is, therefore, imperative that a large run out
  area free of hazards be available downstream from
  the beginning of the terminal.

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STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)
Proper Delineation

• This run out area would desirably be as long as
  250 feet and as wide as 40 feet, but at least the
  width of the design clear zone.

• There should be no obstacle within 75 feet of the
  beginning of the terminal.

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IMPROPERLY INSTALLED EXAMPLE(STD. GR-7)

• The guardrail's stand up trailing terminal on the
  other side of the median ends 12' 6" from the
  beginning of the flared terminal. This placement
  could result in a vehicle that crashes through
  the flared terminal possibly being speared by
  the stand up trailing terminal.

12' 6"
30
STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)

• These terminal systems are proprietary
  (patented). The manufacturers installation
  instructions must be followed precisely, as
  tested and approved.

• Each system uses a breakaway cable anchoring
  system to develop the terminal tension.
• Specific product details are available on the
  manufacturer's web site.

31
IMPROPERLY INSTALLED EXAMPLE(STD. GR-7)

• This GR-7 terminal had been damaged and repaired.
  However, the replacement terminal does not have
  the proper 4 foot parabolic flare.

32
STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)

• The offsets are measured from a tangential line
  extended from the end of the guardrails standard
  section if the terminal is on the inside of the
  curve.

BREAKAWAY CABLE TERMINAL 4' FLARE 501.13
33
STRONG POST W-BEAM SYSTEM(STD. GR-7 FLARED
TERMINAL)

• The offset will be held at the standard section
  offset if the resulting curve is so sharp as to
  make the offset less than the standard section
  offset.

BREAKAWAY CABLE TERMINAL 4' FLARE 501.13
34
GR-9 terminal used without having to add site
preparation for GR-7
35
GR-9 with good runout area, but the approach area
with curb should be clearer.
curb
36
STRONG POST W-BEAM SYSTEM(STD. GR-9 PARALLEL
TERMINAL)
Cable Assembly
Length of Need
Offset Strut
Bearing Plate
Cable Anchor
Guardrail Exit Slot (Away from Traffic)
Begin Typ. Guardrail
Guardrail Extruder
6'- 3"
6'- 3"
6'- 3"
50'
Pay Limits GR-9 Terminal
Traffic

• These terminals are straight systems that may be
  placed parallel with the roadway.

ALTERNATE BREAKAWAY CABLE TERMINAL NO FLARE
501.18
37
(No Transcript)
38
STRONG POST W-BEAM SYSTEM(STD. GR-9 PARALLEL
TERMINAL)

• For small angle impacts, these systems are
  designed to allow a vehicle striking the
  terminal at a small angle to be brought to a
  controlled stop through absorption of the
  impacts energy.

• The vehicle will pass through this system with
  little absorption of energy and little speed
  reduction in higher angle end impacts.

39
STRONG POST W-BEAM SYSTEM(STD. GR-9 PARALLEL
TERMINAL)

• Some parallel systems use a large impact head at
  the terminals beginning which protrudes in front
  of the guardrail. The head may be offset from 1
  to 2 feet. This offset, however, must be
  installed over a 50 foot straight line flare.

40
STRONG POST W-BEAM SYSTEM(STD. GR-9 PARALLEL
TERMINAL)

• GR-9 parallel terminals can be offset up to two
  feet over the entire 50 foot length of the
  terminal. This flare is only on the first 25
  feet, which may cause the terminal to kink since
  the impact head will have to change direction
  midway at the break point of the offset.

25'
41
STRONG POST W-BEAM SYSTEM(STD. GR-9 PARALLEL
TERMINAL)

• These terminal systems are proprietary
  (patented). The manufacturers installation
  instructions must be followed precisely, as
  tested and approved.

• There should be no hazard within the first 75
  feet of this system as measured from the
  terminals beginning.
• Specific product details are available on the
  manufacturer's web site.

42
STRONG POST W-BEAM SYSTEM(TERMINALS FOR CURBED
SECTIONS)

• There are currently no terminals approved for use
  in conjunction with curbs.
• Two recommended methods for installing
  terminals on high speed roadways with curbs
  are
• to lower the curb
• to taper back from the curb

43
STRONG POST W-BEAM SYSTEM(TERMINALS FOR CURBED
SECTIONS)

• Method 1
• Lower the curb to 2 inches of height or less
  for approximately 50 feet in advance of the
  terminalsend so that the vehicle is at the
  appropriate height when contact is made.

• For parallel terminals the 2 inch height should
  be carried an additional 12 feet beyond the
  terminals upstream end and the terminals end
  should be offset 1 foot to keep the impact head
  behind the curbs face.
• The 2 inch height should be carried 37 feet
  beyond the terminals upstream end in flared
  terminals.

44
STRONG POST W-BEAM SYSTEM(TERMINALS FOR CURBED
SECTIONS)

• Method 2
• Taper the guardrail back from the curbs face on
  a 251 taper for 50 feet. Raise the rails
  height an amount equal to the curbs height. Use
  a crashworthy terminal based on this line of 251
  extended.

45
Mountable Curb Transition from 4 inches to 2
inches Height at Terminal End
46
STRONG POST W-BEAM SYSTEM(TRAILING END)

• The trailing, or downstream, end of a guardrail
  system is not likely to be hit by traffic if it
  is outside the clear zone.

• The necessary tension of the system needs to be
  developed at the trailing end by using
  rectangular washers only on the last 50' of
  guardrail.

47
STRONG POST W-BEAM SYSTEM(BREAKAWAY CABLE
ANCHORAGE)

• Terminal systems with exposed ends, such as the
  Std. GR-7 and GR-9, use an anchored cable to
  develop the tension required to handle
  downstream impacts.

• The terminals vertical end is broken away upon
  end-on impacts, thus allowing the vehicle to
  continue downstream.

48
WEAK POST W-BEAM SYSTEM (TRAILING END TERMINALS)

• Turned-down terminals that develop the necessary
  tension may be used.
• The full capability of the guardrail system must
  be available at the end of the hazard.
• This system may be used to terminate a guardrail
  which is outside the clear zone for opposing
  traffic where there is still some likelihood of
  an opposing traffic hit.

Old GR-8 installation
New design
TYPE II TERMINAL TREATMENT (RUN-OFF ANCHORAGE)
501.15
49
WEAK POST W-BEAM SYSTEM (TRAILING END TERMINALS)

• The weak post turned-down terminal Std.GR-8, Type
  II with full anchorage is acceptable as the
  trailing end on a weak post guardrail system.

TYPE II TERMINAL TREATMENT (RUN-OFF ANCHORAGE)
501.15
50
GAPS BETWEEN GUARDRAIL RUNS
Eliminate Terminals
ConnectGuardrail

• Eliminate the terminals and connect the two runs
  when the end of one guardrail run terminates
  within 200 feet of the beginning of the next
  downstream run of the same type of guardrail and
  there is no obvious reason for the gap.

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SUMMARYAPPROACH TERMINALS

• Gaps of less than 200 feet between successive
  runs of guardrail should be closed

• Terminals must provide two functions
• Develop the required tension
• Minimize injury severity for end impacts
• New installations of turndowns are acceptable for
  weak post systems only under low speed run-off
  conditions (45 mph or less)

52
SUMMARYAPPROACH TERMINALS(cont.)

• Buried in back slope (Std. GR-6) is most
  desirable since

• It cannot spear
• It is farther from the travel way
• Generally will not be gotten behind (no LON
  calculation)
• The maximum exposure between the bottom rail and
  the ground is 18 inches
• Provide tension anchor

53
SUMMARYAPPROACH TERMINALS(cont.)

• Proprietary flared terminal (Std. GR-7)

• Allows a vehicle to pass on through for end
  impacts
• Must have adequate runout area behind

54
SUMMARYAPPROACH TERMINALS(cont.)

• Proprietary parallel terminal (Std. GR-9)

• Bring low angle impacting vehicles to a
  controlled stop
• Higher angled impacts pass on through
• If terminal includes an impact head, its
  desirable to have straight flare of 2 feet (at
  least 1 foot minimum)

55
SUMMARYAPPROACH TERMINALS(cont.)

• All remaining hardware after posts break away
  must not exceed 4 inches projection in a 5 feet
  chord

56
SUMMARYTRAILING END TERMINALS

• Tension in standard section must be carried
  beyond the point of need

• The end of the hazard for one direction travel
• The LON for two direction roadway
• Weak post W-beam (Std. GR-8) may use a turndown

57
7 SELF-CHECK QUESTIONS

• 1. Define terminal.
• 2. One function or purpose of a terminal is to
• a. mark the end of the clear zone
• b. hold a delineator
• c. minimize personal injuries and damage to a
  vehicle

58
ANSWERS

• 1. Define terminal.
• The end of the guardrail system.
• 2. One function or purpose of a terminal is to
• c. minimize personal injuries and damage to a
  vehicle

59
7 SELF-CHECK QUESTIONS(cont.)

• 3. The currently approved method for terminating
  a cable system is to
• a. anchor the cables in a concrete deadman
• b. weld the cables together and bolt to the
  ground
• c. taper the cables into a final post

60
ANSWER

• 3. The currently approved method for terminating
  a cable system is to
• a. anchor the cables in a concrete deadman

61
7 SELF-CHECK QUESTIONS(cont.)

• 4. The best way to terminate a strong post system
  is to
• a. cap the rail
• b. wrap the rail around the post
• c. bury the end in a cut slope
• 5. Why is this method the best method?

62
ANSWERS

• 4. The best way to terminate a strong post system
  is to
• c. bury the end in a cut slope
• 5. Why is this method the best method?
• Because nothing is exposed nothing can be hit.

63
7 SELF-CHECK QUESTIONS(cont.)

• 6. You must provide a minimum of _____ of cover
  when burying a beam. You cant _____ or ____ the
  dirt over the rail.
• 7. Why must you anchor and bury the rail deep?
  Why cant you just cover it with dirt?

64
ANSWERS

• 6. You must provide a minimum of 1 foot of cover
  when burying a beam. You cant bubble or mound
  the dirt over the rail.
• 7. Why must you anchor and bury the rail
  deep?Why cant you just cover it with dirt?
• You must anchor and bury the rail in order to
  get the necessary tension. Mounded dirt could
  erode or sluff off over time the end could
  become exposedand become a hazard.