Note: Descriptions are shown in the official language in which they were submitted.
CA 02940944 2016-09-02
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GUARDRAIL SAFETY SYSTEM FOR DISSIPATING ENERGY TO
DECELERATE THE IMPACTING VEHICLE
This is a division of co-pending Canadian Patent Application No. 2,725,225
filed on
May 5, 2009.
TECHNICAL FIELD
The present invention relates generally to safety treatment for the ends of W-
beam
guardrails; and more particularly, to a tensioned guardrail terminal for
dissipating impact
energy of a car colliding with the end of the W-beam guardrail in an end-on or
re-directive
impact.
BACKGROUND
Along most highways there are hazards that can be a substantial danger to
drivers of
automobiles if the automobiles leave the highway. To reduce the severity of
accidents due
to vehicles leaving a highway, guardrails are provided. The guardrails are
installed such that
the beam elements are in tension to aid in re-directive type impacts.
Guardrails must be
installed, however, such that the terminal end of the guardrail facing the
flow of traffic is not
a hazard. Early guardrails had no proper termination at the ends, and it was
not uncommon
for impacting vehicles to become impaled on the guardrail causing intense
deceleration of
the vehicle and severe injury to the occupants. In some reported cases, the
guardrail
penetrated directly, into the occupant compartment of the vehicle fatally
injuring the
occupants.
Upon recognition of the problem of proper guardrail termination, guardrail
designs
were developed that used box beams and W-beams that allow tapering of the end
of the
guardrail into the ground. Such designs eliminate any spearing effect. While
these end
treatments successfully removed the danger of the vehicle being penetrated in
a head-on
collision, it was discovered that these end treatments operate in a ramp-like
fashion and may
induce launching of the vehicle causing it to become airborne for a
considerable distance
with the possibility of roll over.
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In search for better end treatments. improved energy absorbing end treatments
for
W-beam guardrail elements were developed. For example, an extruder terminal
was
developed and typically includes a bending structure that squeezes the
guardrail into a flat
plate and then bends it about a circular arc directed away from the impacting
vehicle.
Example extruder terminal products include the ET 2000TM and the ElPLUSTM
offered by
Trinity Highway Products. Other extruder terminal products include the SKI
350TM and
FLEAT 350TM offered by Road Systems, Inc.
All of these energy absorbing systems use a cable to connect the first w-beam
guardrail segment to the first post in the system. The cable provides tension
in the guardrail
beam element for a redirective hit along the length-of-need portion of the
guardrail. A
number of cable releasing posts have also been developed for use in these
terminals. The
cable release posts are intended to release the cable anchor and, thus,
release the tension in
the system when the post is impacted in either of a forward (end-on) or
reverse direction.
Such systems are not able to remain in tension during end-on and reverse-
direction type
impacts.
SUMMARY OF THE INVENTION
The present invention provides a new and improved end treatment for highway
guardrails.
In accordance with a particular embodiment of the present invention, there is
provided a terminal portion of a guardrail safety system comprising: a
terminal portion of a
guardrail beam comprising a downstream end and upstream end, the terminal
portion of the
guardrail beam sloping from a height appropriate for redirecting an errant
vehicle to a height
proximate the surface of the ground at an upstream end of the terminal
portion; a plurality of
support posts installed adjacent a roadway in spaced apart relation to one
another, the
plurality of support posts coupled to the terminal portion of the guardrail
beam; and a
terminal support post installed adjacent the roadway at an upstream end of the
end terminal,
the terminal support post coupled to an upstream end of the terminal portion
of the guardrail
beam by a resistive, tensile coupling that maintains tension in the terminal
portion of the
guardrail beam, the resistive, tensile coupling maintained between the
terminal support post
CA 02940944 2016-09-02
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and the guardrail beam during an end-on or re-directive impact by a vehicle,
the resistive,
tensile coupling released between the terminal support post and the guardrail
beam during a
reverse-direction impact.
Another exemplary embodiment provides a terminal portion of a guardrail safety
system comprising: a terminal portion of a guardrail beam; a terminal support
post coupled
to an upstream end of the terminal portion of the guardrail beam, the terminal
support post
comprising: a structural member having a longitudinal axis, the structural
member for
installing below grade adjacent the roadway; a connector assembly coupling the
terminal
portion of the guardrail beam to the structural member at an acute angle
relative to the
longitudinal axis of the structural member, the connector assembly comprising
an opening
through which the upstream end of the terminal portion of the guardrail beam
is disposed;
and wherein the coupling of the structural member and the terminal portion of
the guardrail
beam is maintained during an end-on or re-directive impact by a vehicle and is
released
during a reverse-direction impact.
A further exemplary embodiment provides a terminal portion of a guardrail
safety
system comprising: a terminal portion of a guardrail beam comprising a
downstream end
and an upstream end, the terminal portion of the guardrail beam sloping from a
first height
appropriate for redirecting an errant vehicle to a second height proximate the
surface of the
ground at an upstream end of the terminal portion; a plurality of support
posts installed
adjacent a roadway in spaced apart relation to one another, the plurality of
support posts
coupled to the terminal portion of the guardrail beam; and a terminal support
post coupled to
the upstream end of the terminal portion of the guardrail beam, the terminal
support post
comprising: a structural member having a longitudinal axis, the structural
member for
installing below grade adjacent the roadway; a connector assembly coupling the
terminal
portion of the guardrail beam to the structural member at an acute angle
relative to the
longitudinal axis of the structural member; and wherein the coupling of the
structural
member and the terminal portion of the guardrail beam is maintained during an
end-on or re-
directive impact by a vehicle and is released during a reverse-direction
impact.
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Technical advantages of particular embodiments of the present invention
include a
guardrail end treatment that may dissipate impact energy through the
compression of the W-
beam guardrail element. Thus, one advantage may be that the guardrail end
treatment is
energy absorbing. Another advantage may be that the end treatment forces the W-
beam
guardrail element through a flattening structure that squeezes the guardrail
into a relatively
flat plate. Specifically, the guardrail end treatment may dissipate impact
energy of a vehicle
colliding with an end of a guardrail by flattening a portion of the guardrail.
Still another advantage may be that an end of the W-beam guardrail element
extends
through the flattening structure and tapers to the ground. The W-beam
guardrail element
may be secured to the ground in tension. The components of the system that
provide the
tensile connection of the guardrail beam to the terminal support post may
enable the
guardrail beam to remain secured after an end-on or re-directive impact. Thus,
the system
may remain in tension during both types of impacts. Still another advantage
may be that the
tension is released when the system is impacted in the reverse direction near
the terminal
end, however. The releasing of tension in the guardrail element for reverse
direction
impacts prevents vehicle instability and excessive deceleration.
Technical advantages of particular embodiments of the present invention
include a
guardrail end treatment that dissipates impact energy through the compression
of a W-beam
guardrail element. Thus, one advantage may be that the guardrail end treatment
is energy
absorbing. Another advantage may be that the end treatment forces the W-beam
guardrail
element through a flattening structure that squeezes the guardrail into a
relatively flat plate.
Specifically, the guardrail end treatment may dissipate impact energy of a
vehicle colliding
with an end of a guardrail by flattening a portion of the guardrail.
Still another advantage may be that an end of the W-beam guardrail element
extends
through the flattening structure and tapers to the ground. The W-beam
guardrail element
may be secured to the ground in tension. The components of the system that
provide the
tensile connection of the guardrail beam to the terminal support post may
enable the
guardrail beam to remain secured after an end-on or re-directive impact. Thus,
the system
may remain in tension during both types of impacts. Still another advantage
may be that the
tension is released when the system is impacted in the reverse direction near
the terminal
CA 02940944 2016-09-02
end, however. The releasing of tension in the guardrail element for reverse
direction
impacts prevents vehicle instability and excessive deceleration.
Other technical advantages will be readily apparent to one skilled in the art
from the
following figures, descriptions and claims. Moreover, while specific
advantages have been
5 enumerated above, various embodiments may include all, some or none of
the enumerated
advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 illustrates a top view of an exemplary guardrail safety system that
incorporates certain aspects of the present invention;
FIGURE 2 illustrates a side view of a terminal portion of a guardrail system
that
incorporates certain aspects of the present invention;
FIGURE 3 illustrates a side view of an exemplary embodiment of an end
treatment
in the terminal portion of a guardrail system, in accordance with a particular
embodiment of
the present invention;
FIGURES 4A and 4B illustrate a side view and a profile view, respectively, of
a
modified guardrail beam that incorporates certain aspects of the present
invention;
FIGURES 5A-5C illustrates an exemplary weakened support post suitable for use
in
a guardrail safety system, in accordance with a particular embodiment of the
present
invention;
FIGURES 6A-6C illustrates another exemplary weakened support post suitable for
use in a guardrail safety system, in accordance with a particular embodiment
of the present
invention;
FIGURES 7A-7C illustrates an exemplary unmodified support post suitable for
use
in a guardrail safety system, in accordance with a particular embodiment of
the present
invention;
FIGURES 8A and 8B illustrate an exemplary embodiment of a terminal support
post
for use in a guardrail safety system, in accordance with a particular
embodiment of the
present invention;
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FIGURES 9A-9C illustrate various components of a resistive, tensile connection
for
connecting a guardrail beam to a terminal support post, in accordance with a
particular
embodiment of the present invention;
FIGURES 10A and 10B illustrate an exemplary resistive, tensile connection for
connecting a guardrail beam to a terminal support post, in accordance with a
particular
embodiment of the present invention;
FIGURES 11A and 11B illustrate an exemplary strut for use in a guardrail
safety
system, in accordance with a particular embodiment of the present invention;
and
FIGURE 12 illustrates an alternative embodiment of a resistive, tensile
connection
for connecting a guardrail beam to a terminal support post, in accordance with
a particular
embodiment of the present invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
Existing guardrail end treatments have proven to be unsafe for some collision
conditions that happen on the highway, sensitive to installation details,
and/or very costly.
However, the end treatment described below is a safety treatment for the ends
of a W-beam
guardrail that provides a higher level of performance over a wider range of
collision
conditions and reduces end treatment costs and the number of injuries and
deaths associated
with guardrail terminal accidents. The described system maintains the tension
in the
guardrail beam element during both end-on and re-directive type impacts. When
the system
is impacted in the reverse direction near the terminal end, however, the
anchorage system
may release to prevent vehicle instability or excessive deceleration.
FIGURE 1 illustrates a guardrail safety system 100 that incorporates certain
aspects
of the present invention. Guardrail system 100 may be installed adjacent a
roadway, to
protect vehicles, drivers and passengers from various obstacles and hazards,
and prevent
vehicles from leaving the roadway during a traffic accident or other hazardous
condition.
Guardrail systems that incorporate aspects of the present invention may be
used in median
strips or shoulders of highways, roadways. or any path that is likely to
encounter vehicular
traffic.
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Guardrail system 100 includes a guardrail beam 102 and support posts 104 that
anchor guardrail beam 102 in place along the roadway. In a particular
embodiment,
guardrail beam 102 may include multiple 12-gauge W-beam rail elements of a
length on the
order of approximately 12.5 feet or 25 feet. The guardrail beam sections may
be mounted at
a height of on the order of approximately 27 to 31 inches with rail splices
positioned mid-
span between the support posts 104. Guardrail beam 102 and the terminal end of
guardrail
beam 102, specifically, are illustrated in more detail in FIGURES 4A and 4B
and will be
described below.
Guardrail beam 102 is attached to support posts 104 with connectors that may
include, in particular embodiments, slotted countersunk bolts such as, for
example, 16 mm
(5/8-inch) diameter by 38 mm (1-1/2-inch) long flat slot machine screws.
Oversized
guardrail nuts may be used on the back side of the support post 104. Support
posts 104 may
be embedded in the ground, a concrete footing, or a metal socket. Support
posts 104 may be
made of wood, metal, plastic, composite materials, or any combination of these
or other
suitable materials. It is also recognized that each support post 104 within
guardrail system
100 need not necessarily be made of the same material or include the same
structural
features. Furthermore, the cross-section of support posts 104 may be any
engineered shape
suitable for releasably supporting guardrail beam 102. Such cross-sectional
shapes may
include, but are not limited to, square, rectangular, round, elliptical,
trapezoidal, solid,
hollow, closed, or open.
Guardrail system 100 is intended to keep errant vehicles from leaving the
roadway
during a crash or other hazardous situation. In many instances, guardrail 100
is installed
between a roadway and a significant hazard to vehicles (e.g., another roadway,
a bridge,
cliff, etc.). Therefore, guardrail system 100 should be designed to withstand
a significant
impact from a direction generally perpendicular to the roadway, without
substantial failure.
It is this strength that allows guardrail system 100 to withstand the impact,
and still redirect
the vehicle so that it is once again traveling generally in the direction of
the roadway.
However, testing and experience has continuously shown that guardrail systems
may
actually introduce additional hazards to the roadway and surrounding areas.
This is
particularly true with respect to vehicles that impact the guardrail system
adjacent its
CA 02940944 2016-09-02
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terminal section, in a direction generally parallel to the roadway. For
example, if the
guardrail system were rigidly fixed in place during a crash, serious injury
and damage may
result to the errant vehicle, its driver and passengers. Accordingly, many
attempts have been
made to minimize this added risk. Such methods generally include the use of
terminal
portions that are tapered from the ground up to effectively reduce the impact
of head on
collisions and to create a ramp-like effect that causes vehicles to go
airborne during a crash.
Other methods include breakaway cable terminals (BCT), vehicle attenuating
terminals
(VAT), SENTRE end treatments, breakaway end terminals (BET) and the breakaway
support posts of U.S. Patent No. 6,398,192 ("192 Patent"). Many-such
terminals, supports,
end treatments and the like are commercially available from various
organizations.
Examples include the HBA post by Exodyne Technologies and Trinity Industries,
and a
breakaway support post similar in configuration to that described in the '192
Patent.
Referring again to FIGURES 1 and 2, guardrail system 100 includes one terminal
post 106 and seven support posts 104. Collectively, this configuration forms a
terminal
section 108 of guardrail system 100. As shown, terminal section 108 is
employed in a
preferred embodiment as an end terminal for a conventional guardrail assembly
100.
Although FIGURE 1 is illustrated with dimensions and depicts one exemplary
embodiment, it is understood that the dimensions of guardrail system 100 may
vary
depending on the nature of the roadside hazard being shielded. As illustrated,
each terminal
section 108 has a length on the order of approximately 35 feet. However, the
dimensions of
terminal section 108 may vary as needed. Additionally, the length of the
length-of-need
portion of the system may of any appropriate length required by the conditions
of the
roadway.
Terminal section 108 may be installed either parallel to the roadway or at an
angular
departure from the roadway, as shown best in FIGURE 1. Additionally, while the
terminal
section 108 at one end of the guardrail safety system may be flared, the
terminal section 108
at the opposite end of the system may not be flared. in certain embodiments.
For example,
in the embodiment depicted in FIGURE 1, an upstream terminal section 108 is
flared while
a downstream terminal section 108 is not flared. Specifically, the upstream
terminal
sections 108 is flared away from the roadway in a substantially linear manner
while the
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downstream terminal section 108 remains substantially parallel to the roadway.
In other
embodiments, both terminal sections 108 may be flared or unflared in a similar
manner.
Additionally, it is recognized that other configurations may be used for
terminal sections
108. For example, one or both of terminal sections 108 may be installed at a
parabolic flare
away from the roadway. A parabolic flare may be accomplished by increasing the
offset of
each support post in a generally parabolic progression as the terminal portion
proceeds
upstream. Where incorporated, positioning of one or more of terminal sections
108 at a
flared or angular departure away from the roadway may permit the terminal
sections 108 to
perform a gating function by facilitating movement of the impacting vehicle to
the side of
the rail opposite the roadway as the vehicle progresses.
In a particular embodiment where terminal section 108 is linearly flared,
terminal
section 108 may be flared back at an angle of approximately 6 to 7 degrees
from the non-
terminal portion of the guardrail. Where support posts 104 of terminal section
108 are
spaced apart at intervals of approximately 75 inches, the most downstream post
104 of
terminal section 108 may be approximately 9 inches offset from a line tangent
to the non-
terminal portion of the guardrail, in a particular embodiment. Moving toward
the upstream
end of terminal section 108, the next four successive support posts 104 may be
19, 29.25,
39, and 48 inches offset from a line tangent to the non-terminal portion of
the guardrail, in
this embodiment. Terminal post 106, which may be positioned directly below
guardrail
beam 102, may be approximately 47 inches offset from a line tangent to the non-
terminal
portion of the guardrail, in the described embodiment.
As shown better in FIGURE 2, terminal section 108 includes an end treatment
110.
End treatment 110 includes a flattening chute 112 and a front striking plate
114. End
treatment 110 and flattening chute 112, specifically, is mounted onto a first
post 104 by
fasteners such as bolts. The purpose of end treatment 110 is to dissipate
impact energy of
the vehicle without creating a dangerous condition such as causing the vehicle
to roll-over or
allow the guardrail 102 to spear the vehicle or the occupant compartment of
the vehicle.
Guardrail beam element 102 feeds into an inlet 116 at a downstream end of
flattening chute 112. Guardrail beam element 102 is disposed within flattening
chute 112
and extends the length of flattening chute 112. Guardrail beam element 102
exits an outlet
CA 02940944 2016-09-02
118 at an upstream end of flattening chute 112. As will be described in more
detail with
regard to FIGURE 3, the dimensions of flattening chute 112 results in a
terminal portion of
the guardrail beam 102 tapering to the ground. The portion of guardrail beam
element 102
exiting outlet 118 is flattened vertically such that the terminal portion of
guardrail beam
5 element 102 resembles a stack of four flat plates.
A terminal post 106 secures the terminal end of guardrail beam element 102 to
the
ground and places guardrail beam element 102 in tension. As will be described
in more
detail with regard to FIGURES 8A and 8B and 10A and 10B, the coupling of
guardrail beam
element 102 to terminal post 106 enables guardrail beam element 102 to remain
secured in
10 tension to terminal post 106 after either of an end-on or re-directive
impact by a vehicle
leaving the roadway. However, the components effecting the tensile coupling
enables the
tension in guardrail beam element 102 to be released when the system is
impacted in the
reverse direction near the terminal end. The releasing of tension in the
guardrail element for
reverse direction impacts prevents vehicle instability and excessive
deceleration.
FIGURE 3 illustrates an exemplary embodiment of end treatment 110 in greater
detail. As described above, end treatment 110 includes a flattening chute 112
and a front
striking plate 114. Flattening chute 112 and front striking plate 114 are
coupled to an
extruder 120. Extruder 120 surrounds the upstream portion of guardrail beam
member 102
and is made up of an upper, U-shaped channel member 122 and a lower, U-shaped
channel
member 124, which are secured in a spaced relation to one another by strap
plates 126.
The vertical distance between channel members 122 and 124 is an appropriate
distance such that guardrail beam 102 is inserted into the channel created by
extruder 120.
For example, where guardrail beam 102 comprises a 12-gauge W-beam rail element
having
a vertical dimension of approximately 12.25 inches, the distance between the
top of channel
member 122 and the bottom of channel 124 may be approximately 14 inches, in a
particular
embodiment.
Front striking plate 114 is secured by welding to extruder 120 of end
treatment 110.
Front striking plate 114 may be vertically elongated, in particular
embodiments. Thus, front
striking plate 114 may extend both above and below extruder 120 to permit
front striking
plate 114 to be easily engaged by either the high bumper of trucks, SUV's, and
other taller
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11
vehicles and the low set bumpers of smaller cars impacting in a frontal
manner. Front
striking plate 114 is also positioned so as to engage the vehicle frame or
rocker panel to
reduce vehicle intrusion when the upstream end of end treatment 110 is
impacted by a
vehicle in a sideways manner.
Flattening portion 112, which is mounted to extruder 120, may be constructed
from
four metal plates, in a particular embodiment. The four metal plates may be
cut and/or bent
and then welded together to form the desired configuration. Alternatively,
flattening portion
112 may be formed from more than four pieces or from a single piece of metal
that is cut
and bent into the desired configuration. When flattening portion 112 is
assembled,
flattening portion 112 may form an enclosed structure that houses a terminal
portion of
guardrail beam 102.
In the illustrated embodiment, flattening portion 112 includes three sections.
The
most downstream portion of flattening portion 112 includes a throat 128. The
vertical
dimension of throat 128 is greater at the downstream end and decreases as it
approaches the
upstream end of end treatment 110. For example, in a particular embodiment,
the vertical
dimension of throat 128 may be approximately 14 inches wide at the downstream
end and
approximately 4.5 inches wide at the upstream end. The horizontal length of
throat 128 may
be within a range of approximately 11 to 13 inches.
In a particular embodiment, the slope of a lower edge 132 may be greater than
the
slope of an upper edge 130. The increased slope of lower edge 132 may aid in
the flattening
of guardrail beam 102 during an impact. For example, in a particular
embodiment, upper
edge 130 may slope upward at an angle of approximately 11 degrees from the
horizontal,
and lower edge 132 may slope downward at an angle of approximately 13 degrees
from the
horizontal. In still other embodiments, the slope of upper edge 130 and lower
edge 132 may
be substantially the same. Thus, in a particular embodiment, upper edge 130
and lower edge
132 may symmetrically mirror one another. In still other embodiments, one of
top edge 130
and lower edge 132 may be aligned with the horizontal (substantially parallel
with the
roadway) while the other of top edge 130 and lower edge 132 slopes upward or
downward,
respectively.
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12
A mid portion 134 extends from the upstream end of throat 128 and slopes
toward
the ground. Specifically, mid portion 134 is configured to transition
guardrail beam element
102 from a height above the ground level that is appropriate for redirecting
an impacting
vehicle (31 inches, in a particular embodiment) to a height that is proximate
the ground's
surface. Thus, mid portion 134 extends from a vertical distance associated
with throat 128
at a downstream end to approximately ground level at an upstream end. In a
particular
embodiment, where the horizontal length of mid portion 134 is approximately
18.75 inches,
mid portion 134 may slope at an angle of approximately 38 degrees from the
horizontal.
Mid portion 134 also provides a channel through which a terminal portion of
guardrail beam element 102 is disposed. In a particular embodiment, the
vertical dimension
of the channel within mid portion 134 may be approximately 4.5 inches (similar
to the width
of throat 128 at the upstream end). The dimensions of the channel within mid
portion 134
may remain substantially constant such that the vertical dimension of the
channel within mid
portion 134 at the downstream end is the substantially the same as the
vertical dimension of
the channel within mid portion 134 at the upstream end.
A third portion of flattening portion 1 12 includes outlet portion 136. Outlet
portion
136 extends from the upstream end of mid portion 134. Outlet portion 136 is
disposed
proximate the grounds' surface and is in substantial alignment with the
grounds' surface.
Outlet portion 136 also forms a channel through which the terminal end of
guardrail beam
element 102 exits the flattening chute 112. In a particular embodiment, the
vertical
dimension of the channel within outlet portion 136 may be approximately 4.5
inches (similar
to the vertical dimension of the channel within mid portion 134). The
dimensions of the
channel within outlet portion 136 may remain substantially constant such that
the vertical
dimension of the channel at the downstream end of outlet portion 136 is
substantially the
same as the vertical dimension of the channel at the upstream end of outlet
portion 136. In a
particular embodiment, the horizontal length of outlet portion 136 may be
approximately 5-7
inches.
As stated above with regard to Figure 2, guardrail beam member 102 is disposed
within and extends throughout the length of flattening portion 1 12.
Specifically, guardrail
beam member feeds into an inlet 116 at a downstream end of flattening chute
112.
= CA 02940944 2016-09-02
I 3'
Guardrail beam element 102 traverses the length of flattening chute 112 and
exits an outlet
118 at an upstream end of flattening chute 112. Thus, a terminal end of the W-
beam
guardrail element extends through the flattening structure. The slope of mid
portion 134
toward the ground in the upstream direction results in guardrail beam element
102 being
gradually transitioned toward the ground over the length of flattening portion
112. After
exiting the outlet 118, guardrail beam element 102 is secured to a terminal
post 106 at
ground level.
During an end-on or oblique end-on collision of a vehicle with front striking
plate
114, end treatment 110 may be displaced in a downstream direction and
downstream
portions of guardrail beam element 102 may be forced into the displaced end
treatment 110.
During such a collision, extruder 120 functions as a guide to guide guardrail
beam element
into flattening portion 112. Extruder 120 includes guides 138 that prevent
shaving of the
W-beam guardrail element 102 by ends of extruder 120 as extruder 120 moves
along the
length of the guardrail beam element 102 during a collision. The guides 138
accommodate
any irregularities or bumps in guardrail beam element 102 to ensure proper
feeding of
guardrail beam element 102 into flattening portion 112.
As end treatment 110 moves along guardrail beam element 102 and downstream
portions of guardrail beam element 102 are forced into flattening portion 112,
guardrail
beam element 102 is flattened vertically. Portions of guardrail beam element
102 exiting
outlet 118 of flattening portion 112 are flattened into what may appear to be
four vertically
stacked plates. For example, where the vertical dimension of guardrail beam
element 102 is
approximately 12.25 inches and throat portion 134 of flattening portion 112 is
approximately 4.5 inches, the vertical dimension of the flattened portion of
guardrail beam
element 102 may be less than approximately 4.5 inches. As this flattening
process occurs,
substantial energy is dissipated slowing the impacting vehicle.
To aid in initial flattening of guardrail beam element 102 for coupling to
terminal
support post 106, a terminal end of guardrail beam element 102 may be
modified.
FIGURES 4A and 4B illustrate a modified guardrail beam element 200 in
accordance with
one embodiment. As shown in FIGURE 4A, the guardrail beam element 200 includes
a
slotted zone 202 at the upstream end of the terminal portion of guardrail beam
element 200.
CA 02940944 2016-09-02
14
In a particular embodiment, slotted zone 202 comprises a series of slots
longitudinally
disposed in the guardrail beam element 200. The use of three slots has proven
effective in
testing models of guardrails constructed similar to guardrail safety system
100.
Slotted zone 202 may initiate at a terminal end 203 of guardrail beam element
200
and extend a desired distance downstream. The horizontal length of slotted
zone 202 may
vary depending on the horizontal length of end treatment 110. It may be
desirable for
slotted zone 202 to include the portion of guardrail beam element 200 that is
coupled to
terminal post 106 and the portion of guardrail beam element 200 that traverses
through
flattening portion 112. Generally, slotted zone 202 may extend from the
terminal, upstream
end of guardrail beam element 200 to some distance between the first and
second support
posts 104. Where, for example, the dimensions of the terminal section 108 of
guardrail
system 100 are similar to those illustrated in FIGURE 1, slotted zone 202 may
extend
approximately 80-85 inches from the terminal end of guardrail beam element
200.
The placement of the slots in slotted zone 202, according to a particular
embodiment,
may be better understood with reference to the cross-section for a typical W-
beam guardrail
200 as shown in FIGURE 4B. A valley 204 is positioned between upper and lower
peaks
206 and is formed at the intersections of inclined web portions 208. Edge
members 210
laterally out lie each peak 206. Highly preferred placement for the slots is
proximate each
peak 206 and the valley 204. Thus, in the illustrated embodiment of FIGURE 4A,
first and
second slots 212 are placed in the first and second peaks 206, respectively. A
third slot 214
is placed in valley 204.
Slots 212 and 214 should be of a size sufficient to enhance the ability of the
terminal
end of guardrail beam element 200 to be flattened. In a preferred embodiment,
the entire
vertical dimension of each peak 206 and valley 204 may be removed. Effective
sizes for
slots 212 have been found to be approximately 0.5 inches, as measured
vertically. An
effective size for slot 214 has been found to be approximately 0.75 inches, as
measured
vertically. Thus, in a particular embodiment, slots 212 may have a width on
the order of
0.5 inches and extend approximately 81-82 inches. Slot 214 may have a width on
the order
of approximately 0.75 inches and extend approximately 81-82 inches. The
provided
dimensions are for example purposes only. however. Any dimensions may be used
for slots
CA 02940944 2016-09-02
212 and 214 to enhance the ability of guardrail beam 200 to be flattened into
four vertically
stacked plates throughout the terminal end of guardrail beam element 200.
While guardrail beam 102 may include W-beam rail elements, it is generally
recognized that the illustrated guardrail beam 102 is merely an example of a
beam that may
5 be
used in a guardrail system. Guardrail beams 102 or portions of guardrail beams
102 may
include conventional W-beam guardrails, thrie beam guardrails, box beams, wire
ropes, or
other structural members suitable for redirecting an errant vehicle upon
impact. It is also
recognized that the configuration and dimensions of any of the above-described
elements
within guardrail system 100 may vary as desired.
10
Returning to FIGURES 1 and 2, following the initial end-on impact of a vehicle
with
end treatment 110 and the initiation of the displacement of end treatment 110
in a
downstream direction, the impacting vehicle and end treatment 110 may engage
one or more
support posts 104. Where the support posts 104 comprises steel yielding
support posts that
are modified at ground level, the impacted support posts 104 may release
guardrail beam
15
element 102 as they are impacted and bent toward the ground. Thus, support
posts 104 that
are impacted during the collision may be displaced, in certain embodiments,
such that they
do not pose a hazard to the impacting vehicle. Although guardrail beam 102 may
be
released from impacted support posts 104, portions of guardrail beam element
102
downstream from the impact may remain in substantially their original position
relative to
the ground's surface. Further, because guardrail beam 102 remains coupled to
terminal post
106 during an end-on or re-directive impact, guardrail beam 102 remains in
tension. This
extends the range of acceptable performance of guardrail safety system 100.
The tension in guardrail beam 102 may also be retained in this manner when
guardrail system 100 is subject to a re-directive impact in the length of need
portion of
guardrail system 100. For example, when an impacting vehicle traveling in a
direction
substantially parallel to the downstream direction of guardrail system 100
leaves the
roadway and impacts guardrail system 100, any support posts 104 impacted by
the vehicle
may operate to release guardrail beam element 102 as they are impacted.
Modified support
posts 104 may be bent toward the ground such that the support posts 104 are
displaced and
do not pose a hazard to the impacting vehicle. Because the tension in
guardrail beam 102 is
CA 02940944 2016-09-02
=
16
maintained, guardrail beam element 102 continues to operate to redirect the
vehicle back
onto the roadway even after one or more support posts are released from
guardrail beam
element 102.
FIGURES 5A-5C, 6A-6C, and 7A-7C illustrate example embodiments of support
posts that may be used in conjunction with guardrail system 100 of FIGURE 1.
Specifically,
FIGURES 5A-5C illustrate an exemplary weakened support post that may be used
as a first
support post 500 (after the terminal support post 106) in the terminal section
108 of
guardrail safety system 100. FIGURES 6A-6C illustrate an exemplary weakened
support
post 600 that may be used throughout terminal section 108 and other portions
of guardrail
safety system 100. FIGURES 7A-7C illustrate a standard line post 700 that may
be used in
certain portions of guardrail safety system 100. Although FIGURES 5A-5C, 6A-
6C, and
7A-7C illustrate three distinct embodiments, respectively, like reference
numerals have been
used to identify parts common to the three embodiments.
As illustrated, support posts 500, 600, and 700 include elongate, continuous
structural members and are each of a standard wide flange configuration. Each
support post
includes two flanges 502, that are generally parallel with one another, and in
spaced apart
relation from one another. A web 504 forms the coupling between flanges 502.
In a
preferred embodiment, flanges 502 include a generally identical configuration
of boltholes
506 and cutouts 508, therein.
With regard to the wide flange shape used as a guardrail post, the cross
section is
typically shaped like the letter "H". The cross section has two major axes for
bending. The
"weak" axis generally refers to a central axis that extends through the web
and is
perpendicular to the flanges. The "strong" axis generally refers to a central
axis that is
perpendicular to the web and parallel to the planes of the flanges. The weak
axis for a
conventional installation of guardrail extends generally transversely to the
road. The strong
axis extends generally along the roadway.
In the illustrated embodiment of FIGURES 5A-5C, 6A-6C, and 7A-7C the wide
flange is a standard W6x8.5, which is commonly used in fabricating support
posts for
guardrail installations. A standard W6x8.5 wide flange may have a nominal six-
inch depth
and weigh eight and one-half pounds per foot. In fact, one advantage of the
present
CA 02940944 2016-09-02
17
invention is the ability to re-use existing, standard equipment to fabricate,
modify, and
install support post 500, without substantial modification to the equipment.
Those of
ordinary skill in the art will recognize that wide flange beams may be
available in many
different sizes. For example, a wide flange having a six-inch depth and
weighing nine
pounds per foot may also be used. Such a wide flange is referred to as a W6x9
wide flange.
However, a W6x9 wide flange and a W6x8.5 wide flange are considered equivalent
in the
trade. The terms "W6x8.5 wide flange" and "W6x9 wide flange" are intended to
refer to all
sizes and configurations of guardrail posts that may be referred to as "W6x9"
by a person of
ordinary skill in the art. In addition, persons skilled in the art recognize
other names used for
wide flanges include but are not limited to "I-beam," "H-beam," "W-beam," "S-
beam," "M-
beam," or the term "shape" may be substituted for "beam."
Support posts 500, 600, and 700 have a length in a range of approximately 72
and 73
3/8 inches, in particular embodiments, and include an upper portion 510 and a
lower portion
512. A mid portion 514 couples upper portion 510 with lower portion 512. Upper
portion
510 includes two boltholes 506 that are adapted to receive connectors for the
installation of a
guardrail beam (e.g., guardrail beam 102) upon the support post. Lower portion
512 is
suitable for installation below grade, as part of a guardrail support system.
Bolt holes 506 include a standard configuration that allow for the
installation of
widely used guardrail beams, upon the respective support post. In general,
bolt holes 506
align with the center of the guardrail beam, and maintain the center of the
guardrail beam
approximately 30 inches above grade. However, the number, size, location and
configuration of boltholes 506 may be significantly modified, within the
teachings of the
present invention.
Support posts 500 and 600 are each modified to include a relatively "weak"
axis W,
and a relatively "strong" axis S. Support posts 500 and 600 are normally
installed along a
roadway such that weak axis W is generally perpendicular to the direction of
traffic, and
strong axis S is generally parallel to the direction of traffic. Accordingly,
support posts 500
and 600 are typically able to withstand a significant impact (e.g.. with a car
traveling at a
high rate of speed) about the strong axis S without substantial failure.
However, support
posts 500 and 600 are intentionally designed such that failure will more
readily occur in
CA 02940944 2016-09-02
18
response to an impact about the weak axis W. Stated differently, support posts
500 and 600
exhibit adequate strength in the lateral direction but sufficiently low
strength in the
longitudinal direction. Accordingly, if a vehicle impacts end treatment 110
"end-on",
support posts 500 and 600 will tend to fail (e.g., buckle), while allowing the
vehicle to
decelerate as it impacts consecutive support posts. However, if a vehicle
strikes guardrail
system 100 along the face of and at an angle to guardrail beam 102, support
posts 500 and
600 will provide sufficient resistance (strength) to redirect the vehicle
along a path generally
parallel with guardrail beam 102.
Mid portions 514 of support posts 500 and 600 include two cutouts 508, which
are
configured to further weaken the support posts about the weak axis W, to more
readily allow
for failure due to impact from a vehicle along that direction. Cutouts 508 are
positioned
within mid portion 514 to weaken the support posts about weak axis W, adjacent
grade
(when installed). This will accommodate failure of the support posts
approximately at
grade, allowing support posts 500 and 600 to "fold" over from the point of
failure, upward.
Since lower portion 512 is below grade, it is not expected that the ground, or
lower portion
512 of the support post will appreciably deflect during an impact.
Since cutouts 508 are intended to occur approximately at grade, and the center
of
bolt holes 506 are intended to occur 30 inches above grade, bolt holes 506
occur 30 inches
above cutouts 508, in the illustrated embodiment. It will be recognized by
those of ordinary
skill in the art that the size, configuration, location and number of bolt
holes, cutouts, and
their relationship with each other, may be varied significantly within the
teachings of the
present invention. The overall length of the support posts, and their
respective upper, lower
and mid portions may vary significantly, within the teachings of the present
invention. For
example, in other embodiments, cutouts 508 may occur below grade or above
grade. The
depth of cutouts 508 below grade should not exceed an amount that will prevent
the support
posts from failing at or near the location of cutouts 508. At some depth below
grade, the
surrounding earthen (or other) material will reinforce lower portion 512 of
the support posts
to an extent that will no longer accommodate such failure to occur.
The height of cutouts 508 above grade should not exceed a point at which the
support post will fail at cutouts 508, and leave a "stub" above grade which
can snag vehicles,
CA 02940944 2016-09-02
19
and otherwise cause excessive injury and/or excessive damage. Such a stub
could be
detrimental to the redirective effect of the guardrail system in which the
support post is
operating.
The vertical dimension of a cutout 508 is limited based upon the horizontal
dimension of cutout 508. For example, a ratio of the vertical dimension of any
particular
cutout may be equal to, or less than three times the horizontal dimension.
Alternatively, the
ratio may be limited to two times the horizontal dimension. In the illustrated
embodiments,
the ratio is 1:1, since cutout 508 is generally a circular opening in the
support post. The
smaller the vertical dimension of the cutout, the more precisely the designer
may dictate the
point of failure along the vertical length of support posts 500 and 600.
Various configurations of cutouts 508 are available to a designer of support
posts
500 and 600, in accordance with the teachings of the present invention. For
example, rather
than circular openings, cutouts 508 may comprise square, rectangular,
triangular, oval,
diamond shaped, or practically any other geometric configuration, and still
obtain some or
all of the benefits described herein.
The horizontal orientation of cutouts 508 within flanges 502 may also be
altered
significantly, within the teachings of the present invention. In the
illustrated embodiments
of FIGURES 5A-5C and 6A-6C, the centerline of cutouts 508 is located
approximately one
inch from the centerline of flanges 508. However, in alternative embodiments,
cutouts 508
may be located closer to such edges, or further from such edges. In one
embodiment,
cutouts 508 may be configured such that they extend all the way to the edge of
the flange,
such that there is a break in material beginning at the edge. In this manner,
a traditional
punch could be employed at the edge, to form a semi-circular opening that
extends to the
edge of the flange.
Alternatively, a sawcut could be employed from the outer edge of the flange,
and
extending inward, to form cutouts 508. In this manner, the sawcut would form
the starting
point of the likely point of failure along the weak axis of the support post.
Rather than a
sawcut, a similar configuration may include a slot in which the longest
dimension extends
horizontally through the flange. Such a slot may begin or terminate at the
edge of the
flange, or otherwise be disposed completely within the material of the flange.
CA 02940944 2016-09-02
As stated above, FIGURES 5A-5C specifically illustrate a guardrail support
post 500
that may be used as the first support post (after the terminal support post
106) in a guardrail
system 100. Where an end treatment such as end treatment 110 is incorporated
into
guardrail safety system 100, support post 500 may be modified to support an
end treatment
5 110. Specifically, support post 500 includes additional boltholes 520 and
522 for coupling
end treatment 110 to support post 500. In the particular illustrated
embodiment, boltholes
520 and 522 are slightly smaller than boltholes 506 and cutouts 508. It is
recognized,
however, that the provided dimensions of boltholes 520 and 522 are provided
for example
purposes only and may vary as appropriate for coupling the end treatment 110
to support
10 post 500. In contrast to support post 500, support posts 600 and 700 do
not include
additional boltholes 520 and 522 and, thus, are more appropriately used in
portions of the
guardrail system 100 that are not directly supporting end treatment 110.
Although W6x8.5 wide flanges are described above and illustrated within this
specification, it should be recognized by those of ordinary skill in the art
that practically any
15 size guardrail support post may be weakened as described above. The
size, weight and
configuration of the support post are just a few factors to be considered to
determine the
appropriate location of cutouts, to allow yielding along the weak axis while
maintaining
sufficient strength along the strong axis to redirect impacting vehicles.
Further, although it
may be desirable for at least a portion of the support posts in the guardrail
safety system 100
20 to include weakened support posts such as support posts 500 and 600 of
FIGURES 5A-5C,
supports posts may also include conventional, unmodified support posts or
other structural
members suitable for supporting a guardrail beam. FIGURES 7A-7C illustrate
such an
unmodified support post. Support post 700 does not include cutouts 508 and may
comprise
standard line posts such as unmodified W6x8.5 posts or any other support post
of an
appropriate size, weight and configuration.
Although certain of the support posts may be configured to release the
guardrail
beam element upon vehicular impact, it may be desirable for a terminal support
post to
remain coupled to guardrail beam even after an end-on or re-directive impact.
FIGURES
8A and 8B illustrate an example embodiment of a terminal support post 800 that
may be
used in conjunction with guardrail system 100 of FIGURE 1. Referring to FIGURE
1,
CA 02940944 2016-09-02
21
terminal support post 800 is the first terminal support post at the upstream
end of terminal
section 108. FIGURE 8 A is a side view of terminal support post 800, and
FIGURE 8B is a
front view of the same terminal support post 800.
In particular embodiments, terminal support post 800 is releasably coupled to
guardrail beam 102 such that guardrail beam 102 and provides positive
anchorage of
guardrail beam 102 to react to tensile loads on guardrail beam 102 to redirect
a vehicle
impacting laterally along the length of guardrail beam 102. Various components
are used to
effect the coupling of guardrail beam 102 to terminal support post 800 such
that guardrail
beam 102 remains coupled to terminal support post 800 when guardrail system
100 is struck
by an impacting vehicle in an end-on or re-directive type impact. As a result,
guardrail
beam element remains supported in tension even after such an impact. However,
when
guardrail system 100 is struck by an impacting vehicle in the reverse
direction, the tensile
coupling of guardrail beam 102 will be released from terminal support post 800
to prevent
vehicle instability and excessive vehicular deceleration.
In the illustrated embodiment, terminal support post 800 includes a structural
member 802 of an I-beam configuration. Structural member 802 includes a pair
of flanges
804 interconnected by a central web 806. In a currently preferred embodiment,
the beam
member 802 comprises a W6x15 steel post member. A pair of rectangular side
plates 808
are affixed opposite sides of structural member 802. Preferably, side plates
808 are secured
by welding to each of flanges 804.
A connector assembly is used to couple structural member 802 to the guardrail
beam
member. The connector assembly is configured such that the coupling of the
structural
member and the terminal portion of the guardrail beam is maintained during an
end-on or re-
directive impact by a vehicle. However, the connector assembly is configured
to release the
coupling during a reverse-direction impact. In a particular embodiment, the
connector
assembly comprises a plurality of stacked rectangular plates that are aligned
to receive the
terminal portion of the guardrail beam. For example, the connector assembly
may include a
stack of three plates: a flange plate 810, a keeper plate 816, and a washer
plate 824.
A flange plate 810 is secured between side plates 808. Flange plate 810 is
preferably
a unitarily formed piece that is secured by welding to structural member 802
and each side
CA 02940944 2016-09-02
22
plate 808. Flange plate 810, as best shown in FIGURE 9A, includes a
rectangular plate with
a V-shaped cut-out 812 at the center of an upper edge 813 of flange plate 810.
In the
illustrated embodiment, flange plate 810 has a length of approximately 5
inches and a width
of approximately 6 inches. The thickness of flange plate 810, as best shown in
FIGURE 8B,
may be approximately 1 inch.
V-shaped slot 812 is centered along the horizontal width of flange plate 810
and has
a vertical length of approximately 1 inch and a horizontal width of
approximately 1 3/4
inches. The rounded bottom 814 of V-shaped slot 812 has a diameter of
approximately 1
1/4 inches. However, the described and depicted dimensions of flange plate 810
are
provided for example purposes only. Although the depicted dimensions may be
appropriate
where structural member 802 includes a W6x15 steel post member, the dimensions
of flange
plate 810 may vary and may depend on size and dimensions of structural member
802.
Returning to FIGURE 8B, a keeper plate 816 is disposed adjacent to flange
plate
810. Similar to flange plate 810, keeper plate 816 is preferably a unitarily
formed piece. As
best shown in FIGURE 9B, keep plate 816 includes a rectangular plate with a
circular
shaped opening 818 proximate an upper edge 820 of keeper plate 816. In the
illustrated
embodiment, keeper plate 816 has a vertical length of approximately 3 1/8
inches and a
horizontal width of approximately 5 3/8 inches. Opening 818 is centered along
the
horizontal width of keeper plate 816 and has a center that is approximately
7/8 inch from
upper edge 820 of keeper plate 816. U-shaped opening 818 may have a diameter
of
approximately 1 1/4 inches. However, the described and depicted dimensions of
keeper
plate 816 are provided for example purposes only. Although the depicted
dimensions may
be appropriate where structural member 802 includes a W6x15 steel post member,
the
dimensions of keeper plate 816 may vary and may depend on size and dimensions
of
structural member 802 and flange plate 810.
Returning to FIGURE 8B, a washer plate 824 is disposed adjacent to keeper
plate
816. Similar to flange plate 810 and keeper plate 816, washer plate 824 is
preferably a
unitarily formed piece. As best shown in FIGURE 9C, washer plate 824 includes
a
rectangular plate with a U-shaped slot 826 at the center of the upper edge 828
of washer
plate 824. In the illustrated embodiment, washer plate 824 has a vertical
length of
CA 02940944 2016-09-02
23
approximately 4 1/8 inches and a horizontal width of approximately 5 1/2
inches. The
thickness of washer plate 824, as best shown in FIGURE 8B, may be
approximately 1/2
inch.
U-shaped slot 826 is centered along the horizontal width of washer plate 824
and has
a vertical length of approximately 1 1/4 inches and a horizontal width of
approximately
1 1/8 inches. The rounded bottom slot 826 has a diameter of approximately 1
1/4 inches.
However, the described and depicted dimensions of washer plate 824 are
provided for
example purposes only. Although the depicted dimensions may be appropriate
where
structural member 802 includes a W6x15 steel post member, the dimensions of
washer plate
824 may vary and may depend on size and dimensions of structural member 802.
Each of flange plate 810, keeper plate 816, and washer plate 824 include a
pair of
boltholes 830. In the illustrated embodiments, boltholes 830 are approximately
3/8 inches in
diameter. When assembled together, a bolthole 830 of each of flange plate 810,
keeper plate
816, and washer plate 824 are in general alignment with one another. A pair of
threaded
bolts 832 may be secured through boltholes 830 to secure flange plate 810,
keeper plate 816,
and washer plate 824 together. A washer 834 may be threaded onto the end of
each of the
threaded bolts 832 to hold the plates relative to each other.
As described above, the purpose of terminal support post 800 is to secure
guardrail
beam 102 in tension. FIGURES 10A and 10B illustrate an exemplary tensile
connection of a
guardrail beam 1000 to a terminal support post such as terminal support post
800 depicted in
FIGURES 8 A and 8B. Specifically, a compressed slotted guardrail beam 1000
similar to
those described above with regard to FIGURES 1, 2, and 4A-4B is coupled to a
connection
plate 1002.
In the illustrated embodiment, connection plate 1002 includes a pair of
boltholes
1004, which may be aligned with a pair of similar boltholes (not shown) in the
terminal end
of the compressed slotted guardrail beam 1000. A pair of threaded bolts 1006
may be
threaded through boltholes 1004 and similarly sized boltholes of guardrail
beam 1000 (not
shown) that are aligned with boltholes 1004. A threaded nut 1008 may secure
each
connection of bolts 1006 through connection plate 1002 and guardrail beam
1000. In a
particular embodiment, the boltholes 1004 and boltholes in guardrail beam 1000
may have a
CA 02940944 2016-09-02
24
diameter on the order of approximately 7/8 inch. In such an embodiment,
threaded bolts
1006 may include 2 1/2 x 3/4" GR. 5 bolts. However, it is recognized that
these sizes are
provided as examples only. Any appropriate size of boltholes and bolts may
used to secure
guardrail beam 1000 to connection plate 1002.
Connection plate 1002 is coupled to a threaded rod 1010. In a
particular
embodiment, threaded rod 1010 may be welded to connection plate 1002. As best
shown in
FIGURE 8B, threaded rod 1010 is threaded through V-shaped cutout 814 of flange
plate
810, circular opening 818 of keeper plate 816, and U-shaped cutout 826 of
washer plate 824.
A nut 836 is threaded on the end of threaded rod 101 to secure guardrail beam
1000 in
tension to terminal support post 800.
The presence of nut 836 prevents withdrawal of cable 1010 from the openings
formed by V-shaped cutout 814 of flange plate 810 and U-shaped cutout 826 of
washer plate
824. Since the opening of keeper plate 816 includes an enclosed circular
opening 818 rather
than an open cutout in the edge of the keeper plate 816, keeper plate 816
ensures that
threaded rod 1010 is properly in place. Keeper plate 816 also adds strength to
the tensile
connection of threaded rod 1010 to terminal post 800. Washer plate 824, which
functions as
a washer between bolt 834 and keeper plate 816, also adds strength to the
connection.
During an end-on or redirective impact to a guardrail system incorporating the
above-described features, the assembly described in FIGURES 8A-8B, 9A-9C, and
10A-
10B enables the tensile connection of guardrail beam 1010 to terminal support
post 800 to
remain intact. Because the guardrail beam 1010 remains in tension, guardrail
beam 1010 is
able to redirect the impacting vehicle. Column buckling of the system may be
eliminated
and an eccentric impacting vehicle may remain in the system longer during
deceleration.
In contrast, when a vehicle impacts the guardrail system in a reverse
direction, the
tensile connection of guardrail beam 1010 may be released. For example, the
reverse-
direction impact may cause the upper edge 820 of keeper plate 816 directly
above circular
opening 818 to be sheared. Threaded rod 1010 is then freed from the openings
formed by
V-shaped cutout 812, U-shaped cutout 826, and circular opening 818. Because
the tensile
connection in guardrail beam 1000 is released, guardrail beam 1000 may be
controllably
collapsed to prevent vehicle instability or excessive deceleration.
CA 02940944 2016-09-02
To further aid in the release of the tensile connection during a reverse-
direction
impact, a modified strut may be used to couple the terminal support post to
the first adjacent
support post. Such a strut is indicated as reference numeral 140 in FIGURE 2
and is
illustrated in more detail in FIGURES 11A and 11B. In the illustrated
embodiment, strut
5 140 includes a longitudinal beam member 1112 that has been modified to
include a strut
plate 1114. Longitudinal beam member 1112 may include have any appropriate
cross-
sectional shape. The length of longitudinal beam member 1112 is appropriate
for coupling
terminal support post 106 and the next adjacent support post 104. In a
particular
embodiment, longitudinal beam member 1112 may include a C-channel member
having a
10 width on the order of approximately 6 inches and a depth on the order of
approximately 2
inches.
As best shown in FIGURE 11B, strut plate 1114 is preferably a unitarily formed
piece that is secured by welding to longitudinal beam member 1112. Strut plate
1114
includes a rectangular plate with a U-shaped cut-out 1116 at the center of the
upper edge
15 1118 of strut plate 1114. In the illustrated embodiment, strut plate
1114 has a horizontal
dimension of approximately 10 inches and a vertical dimension of approximately
8 inches.
The thickness of strut plate 1114 may be approximately 1/4 inch. U-shaped slot
1116 is
centered along the vertical dimension of strut plate 1114 and has a vertical
dimension of
approximately 1 1/2 inch and a horizontal dimension of approximately 5 1/2
inches. The
20 rounded bottom 1120 of U-shaped slot 1116 has a diameter of
approximately 1 1/2 inches.
However, the described and depicted dimensions of strut plate 1114 are
provided for
example purposes only. The dimensions of strut plate 1114 and longitudinal
beam member
1112 may vary.
When a vehicle impacts the guardrail system in a reverse direction, strut 1112
and
25 strut plate 1114 may facilitate the release of the tensile connection
between the guardrail
beam and the terminal support post. Strut plate 1114 is positioned proximate
the outlet end
of flattening portion 112. Strut plate 1114 operates as a ramp to facilitate
the lifting of the
threaded rod coupled to the guardrail beam from the V-shaped cutout 814 of
flange plate
810, circular opening 818 of keeper plate 816, and U-shaped cutout 826 of
washer plate 824.
= CA 02940944 2016-09-02
26
Because the tensile connection in guardrail beam 1000 is released, strut 1112
and strut plate
1114 prevent instability or excessive deceleration of the impacting vehicle.
As described above, FIGURES 10A and 10B illustrate an exemplary tensile
connection of a guardrail beam to a threaded rod. FIGURE 12 illustrates an
alternative
embodiment of a tensile connection that may be used to couple a guardrail beam
to a
terminal post. In the illustrated embodiment, a slotted guardrail beam 1200
may be
modified similar to guardrail beam 200 of FIGURE 4A. Slotted guardrail beam
1200 is
modified at the terminal end 1202 and is coupled to a cable rod 1204. In a
particular
embodiment, slotted guardrail beam 1200 may be coupled to a pair of cable rods
1204.
Cable rods 1204 may traverse through a flattening portion 1206. Flattening
portion
1206 may be similar to flattening portion 110 of FIGURES 1-3. Accordingly, at
least a
portion of cable rods 1204 may traverse the length of flattening portion 1206
and exit an
outlet 1206 at an upstream end of flattening portion 1206. After exiting the
outlet 1206,
cable rods 1204 may be secured to a terminal post 106 at ground level using a
mechanism
similar to that described above with regard to FIGURES 8A-8B, 9A-9C, and 10A-
10B.
Technical advantages of particular embodiments of the present invention
include a
guardrail end treatment that dissipates impact energy through the compression
of a W-beam
guardrail element. Specifically, the guardrail end treatment may dissipate
impact energy of
a vehicle colliding with an end of a guardrail by flattening a portion of the
guardrail required
for deceleration of the impacting vehicle. Another advantage may be that the
end treatment
forces the W-beam guardrail element through a flattening structure that
squeezes the
guardrail into a relatively flat plate. In contrast to prior systems, the W-
beam guardrail
element may be flattened vertically rather than horizontally.
Still another advantage may be that a tensile and resistive coupling may be
provided
for connecting an end of the W-beam guardrail element to a terminal support
post. The
components of the system that provide the tensile connection of the guardrail
beam to the
terminal support post may enable the guardrail beam to remain secured after an
end-on or re-
directive impact. Thus, the system may remain in tension during both types of
impacts.
Still another advantage may be that the tension is released when the system is
impacted in
the reverse direction near the terminal end, however. The releasing of tension
in the
= CA 02940944 2016-09-02
27
guardrail element for reverse direction impacts prevents vehicle instability
and excessive
deceleration.
Although the present invention has been described by several embodiments,
various
changes and modifications may be suggested to one skilled in the art. It is
intended that the
present invention encompass such changes and modifications as fall within the
scope of the
present appended claims. For example, the features described above may be used
independently and/or in combination with each other or other design
modifications.
