Designer Edition

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Designer Edition
Revised October 2002
The Virginia Department of Transportation
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COURSE GOAL

• You will gain the knowledge required to become
  proficient in guardrail design.

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COURSE OBJECTIVES

• You will be able to perform the following tasks
  at the
• end of this course

• correctly define and use guardrail terminology
• identify the different types of guardrail systems
• properly apply the current VDOT standards when
  designing guardrail system components
• state what are the new federal (NCHRP 350) and
  state policies and guidelines governing
  guardrail installation, replacement, and repair

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EXAMPLES

• Following are some examples to get you thinking
  about some of the real world situations out
  there that you may have to deal with on a
  project.
• We will discuss how to address some of these as
  we go through the training.

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Existing R/W
Side Road Connection
Problem --------Existing Br., No R /W What should
we do? Need to know design speed, Right of Way
available, what is the connection?
Solution---------Because of R/W, traffic, and
speed, the use of Chevrons as shown is the only
viable solution.
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12 6 LONG 2 in. HIGH CURB
50 FT. LONG 2 IN. HIGH CURB
200 ft. LON GR-2
GR-9
SPAN WIRE SIGNAL POLE
OFFSET PER MANUFACTURERS INSTALLATION
INSTRUCTIONS
W-BEAM END SECTION (BUFFERED)
APPLICABLE ONLY IF STANDARD CG-3 EXTENDS TO GR-9
TERMINAL
5 Ft.
12 6 for GR-9 Terminal 37 6 for GR-7
Terminal
5 Ft. curb trans
50 Ft.
Curb Trans
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After the fact request the plans did not call
for any protection of the signal pole. How do we
protect the signal pole?
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Solution was to place GR-2A around the pole, 25
of 2A on the run-on end of the pole and 25 on
the run-off end. On the approach side,
determine the LON (18 x 15 270) install MB-3
with a CAT 350 or Breakmaster 35 as terminal.
Radial GR-2A
25 GR-2A
25 GR-2
MB-3
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Narrow median Question the use of Barrier,
What type should be used, What is the speed and
accident history ?
AASHTO Roadside Design Guide recommendations for
flat medians that are wider than 50 ft..,
barrier is not warranted unless there is an
adverse accident history. This means that
barrier is recommended if the median width is
less than 50 ft.
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Guardrail used in narrow medians, remember height
of rail when protecting vehicles in opposite
lane.
H
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CAT used to terminate guardrail/Median Barrier
in narrow medians
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Bridge attachment for flared terminal wall
(Special design insertable sheet)
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This appears to have been old BCT
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Gore Area
FOA2
Northbound Ramp
D.I. 13 Ft Long
Direction of Traffic
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Southbound Ramp
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Abutment Bridge
D.I. 21 Ft Long
Maximum 45 Feet
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114 Ft
D.I. 19 FT Long
10 Feet
Photo Relative Positions to Sketch
Attachment Photo numbers are at approximate
location On sketch, arrow indicates direction of
Sight
Northern Va. Area - - Problem -- The following
pictures will show Gore area with multiple inlets
of various lengths. The gore area Tapers to a
very narrow width.
SolutionUse the GR-10 to span the inlets, with
double rails (type 3 can span up to 23), use a
Quadguard at the gore area. Do not use multiple
GR-7s or 9s.
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Use Fixed Object Attachment
21 Drop Inlet
Photo 1
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Photo 2
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Photo 3
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Photo 4
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Gore Area, because of width between two ramps a
Quadguard best suits.
Photo 5
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Rte. 81 project, gore area needs to be protected.
Off ramp has guardrail in the gore area.
Extend guardrail on both the mainline and ramps,
then use an appropriate terminal such as sand
barrels, Wide Quadguard, or if possible look at
filling the gore area to get a safe runout
distance.
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Rte. 81 going over, How do you protect the
area? If adequate room, extend guardrail, add
appropriate terminal, making sure the area behind
and beyond the terminal provides a safe run out
area with appropriate Length of Need protecting
vehicles from going into the roadway below.
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Problem - Gore area, steep drop off, very narrow
space between mainline and ramp.
Solution extend guardrail on mainline and ramp,
use attenuator such as sand barrels Quadguard, or
if possible fill in the gore area to get the
required Length of Need.
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Truck escape ramp, in checking all reference
materials could not find information stating
guardrail with appropriate terminals is required.
Keep ramp clear have required dimensions.
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Problem - Very narrow median,difference in
elevations paved ditch. Since this was a
guardrail upgrade project, no money to change
drainage or ditch area.
Recommended solution Place guardrail on high
side, bring rail off the bridge on runoff end and
then bring across the median, tie into back of
rail forming the MB-3 section extend so you can
get the length of need required then place a CAT
or transition the MB-3 to single GR-2 with
required length before you place a Standard GR-9.
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Problem Narrow median, guardrail needed.
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Transition this rail into the back creating a
median barrier on one side of the roadway.
Solution Remove turndown section, connect
guardrail from this end, connect with runoff end
from bridge in background, take existing rail
across ditch and tie rail into back side, run on
back side the entire length for opposing traffic.
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Problem terminals should not be back to back,
with narrow medians, keep GR on one side with an
extra rail on back side for runoff side.
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The distance between the arrows should be at
least 75. This site is being corrected.
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This is a GR-7 (FLEAT), with a 4 offset. This
location has a good run out area.
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FLEAT - the site preparation does not appear to
be adequate . With the FLEAT the rail will be
extruded out the front.
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This is on Rte. 100 Salem Dist. A new GR-6 was
installed because there is a deep cut area just
past the sign.
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The next four slides are an example of a typical
request for Bridge Guardrail Attachments.
Parallel roadways separated by a stream has
very short radius areas, parking area adjacent
to roadway and bridge.
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The need to maintain the parking space was an
issue. If you can get a usable radius, then turn
the guardrail away from all traffic.
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The shortest radius that we use on any bridge
attachment is 8-6, in this case you have to
worry, How do I terminate the guardrail? Need to
know the volume of traffic using both roadways.
If very low traffic, sometimes all you need to do
is delineate using Chevrons.
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No idea what the problems are, but I think a
torch should be used to improve this
picture. Total replacement of the bridge rail is
in order.