Youll be introduced to the three basic standard guardrail systems in this chapter:

1
Standard Guardrail Systems

• Youll be introduced to the three basic standard
  guardrail systems in this chapter
• Weak Post
• Strong Post
• W-beam Median Barrier
• Youll learn about each systems dimensions,
  characteristics, and design and installation
  standards.

2
CHAPTER 3 OBJECTIVES

• You will be able to perform the following tasks
  after finishing this chapter
• identify the three basic types of guardrail
  systems
• describe general dimensions, characteristics, and
  standards for each of the three basic systems

3
WEAK POST CABLE SYSTEM(STD. GR-3)

• Critical dimensions

31/2"
3"

• The top cable must be a minimum of 27 inches and
  a maximum of 28 inches from the ground line.
• The cables must be spaced as illustrated.
• The top of the post must be 35 inches above the
  top of the soil plate. The bottom of the post
  must be 28 inches below the top of the soil plate.

3"
31/2"
27" min. 28" max.
35"
Ground Line
28"
8"24"1/4" Soil Plate
INTERMEDIATE POST DETAIL 501.07
4
WEAK POST CABLE SYSTEM(STD. GR-3)

• The dynamic deflection for Standard GR-3 is 11
  feet.
• The terminals on a cable rail system shall be
  fitted with turnbuckles and spring compensators
  to maintain and adjust desired cable tensioning
  for the expected temperature range. See VDOT
  Specifications for proper tensioning
  requirements.

TYPICAL INSTALLATION 501.06
5
WEAK POST CABLE SYSTEM(STD. GR-3)

• Note the turnbuckle on the terminal end for
  adjusting the tension in the cable.

• Remember, the dynamic deflection is 11 feet.

6
WEAK POST W-BEAM SYSTEM(STD. GR-8, 8A, 8B AND 8C)
12 Backup Plate Each Post
Back of Rail Single round washer and double nut
connection
Front of Rail 2 Square Washer
5/16" Carriage Bolt and Nut
32 1/4"
This is an existing GR-8, the new design will
have the splice joint between posts.

• The height of this system must be 32 1/4 inches
  as measured from the ground line or the shoulder
  slope extended (see Chapter 4).

TYPICAL INSTALLATION 501.14
7
WEAK POST W-BEAM SYSTEM(STD. GR-8, 8A, 8B AND 8C)
TYPICAL INSTALLATION POST SPACING 501.14
8
LAPPING WITH W-BEAM SYSTEM

• Critical points to consider when lapping
  sections
• On roads with one-way traffic

• Lap all W-beam panels in the direction of the
  traffic. The upstream panel should always
  overlap the downstream panel, including
  terminal connectors at fixed object attachments
  and end sections on trailing end terminals.

Lap in Direction of Traffic
On roads with two-way traffic

• Laps on the right side of traffic are to be in
  the direction of traffic. In other words, the
  laps are to be towards the downstream end of the
  guardrail.

9
STRONG POST, BLOCKED-OUTW-BEAM SYSTEM (STD. GR-2)

• Three critical points

• The maximum dynamic deflection for Std. GR-2 is 3
  feet for both steel and wood posts.
• The post spacing is the same for both steel and
  wood posts.
• The top of the W-beam must be measured from the
  ground line or the shoulder slope extended (see
  Chapter 4).

GR-2 (6' - 3" POST SPACING) 501.04
10
STRONG POST, BLOCKED-OUTW-BEAM SYSTEM (STD.
GR-2A)

• Two critical points

• The maximum dynamic deflection for Std. GR-2A is
  2 feet for both steel and wood posts no test
  data are available to determine an exact
  measurement.
• The post spacing is the same for both steel and
  wood posts.

GR-2A (3' - 11/2" POST SPACING) 501.04
11
STRONG POST, BLOCKED-OUTW-BEAM SYSTEM (STD. GR-2)
2
1
Two problems need to be corrected

• 1. This section of rail uses rectangular washers.
  These washers can only be used on the last 50
  feet of GR-2 trailing end sections.

2. The steel blockouts are no longer acceptable,
and need to be replaced with wood blockouts (when
repair or replacement is being done)..
12
STRONG POST, BLOCKED-OUT W-BEAM SYSTEM (STD.
GR-2, 2A)

• Two key points

• Steel blockouts are no longer acceptable.
• See VDOT Standards for optional 6" 6" routed
  blockouts for use in repair work.
• No rectangular washers shall be used other than
  on the last 50 feet on trailing run-off ends
  for anchorage without cables.

STEEL POST 501.05
13
STRONG POST, BLOCKED-OUT W-BEAMMEDIAN BARRIER
(STD. MB-3)

• Standards for rail height, post lengths,
  blockouts, washer requirements, post spacing and
  lapping are the same as that for single rail
  W-beam guardrail.
• There should be a 4 foot minimum offset from the
  face of guardrail to the edge of the pavement.

STEEL POST 501.41
14
WEAK POST W-BEAMMEDIAN BARRIER (STD. MB-5)

• Standards for rail height, post lengths, washer
  requirements, post spacing and lapping are the
  same as that for single rail W-beam guardrail.
• There should be a 7 foot minimum offset from the
  edge of the pavement.

Support Bolt to belocated under both Rail Beams.
32 ¼ above ground

• Notes
• Standard MB-5 post spacing is 12' - 6"
• Standard MB-5A post spacing is 6' - 3"
• Standard MB-5B post spacing is 3' - 11/2"
• Standard MB-5 deflection is 8' - 0"

TYPICAL INSTALLATION 501.42
15
SUMMARYSTANDARD GUARDRAIL SECTIONS

• Four summary points are

• Tension is the primary contributor to guardrails
  redirection capability. Strong posts provide
  significant contribution so soil resistance must
  be developed.
• Minimum post length shall be 6 feet for the
  strong post system.
• Median barriers (Std. MB-3 and MB-5) can be hit
  from either side.
• Apply principles of standard guardrail (Std. GR-2
  and GR-8).

16
SELF-CHECK QUESTIONS

• 1. The two main types of guardrail systems are
  _____ post and _____ post.
• 2. The two main types of rails used in guardrail
  systems are _____ and _____ .
• 3. Posts are typically spaced _____ apart in a
  strong post guardrail system.
• 4. In general, the installation height of
  Standard GR-2 and Standard GR-3 is _____ to _____
  above ground level.

17
ANSWERS

• 1. The two main types of guardrail systems are
  strong post and weak post.
• 2. The two main types of rails used in guardrail
  systems are cable and W-beam.
• 3. Posts are typically spaced 6' 3" apart in a
  strong post guardrail system.
• 4. In general, the installation height of
  Standard GR-2 and Standard GR-3 is 27" to 28"
  above ground level.

18
SELF-CHECK QUESTIONS(cont.)

• 5. Minimum post length for Standard GR-2 is
  _____ feet.
• 6. For weak post guardrail installations, the top
  of the rail is _____ above ground level.

19
ANSWERS

• 5. Minimum post length for Standard GR-2 is 6
  feet.
• 6. For weak post guardrail installations, the top
  of the rail is 32 1/4" above ground level.