980164 “Development of a 100 Km/H Reusable High Molecular
Weight/High Density Polyethylene Truck Mounted Attenuator”
Abstract: This paper describes the development and full-scale crash
testing of a reusable truck mounted attenuator that dissipates kinetic energy
through the lateral deformation of a nested cluster of high molecular
weight/high density polyethylene (HMW/HDPE) cylinders. This 100 km/h impact
attenuation device, called the Vanderbilt Truck Mounted Attenuator (VTMA),
satisfies the crash testing requirements of National Cooperative Highway
Research Program (NCHRP) Report 350. It has been approved by the Federal Highway
Administration (FHWA) for use on the National Highway System under these NCHRP
Report 350 guidelines. Most impact attenuation devices currently employed
require the replacement of damaged structural components and spent energy
dissipating elements following an impact event. Conclusions: The VTMA is
a reusable and self-restorative truck mounted attenuator. It can dissipate large
amounts of kinetic energy, undergo significant deformations and strains without
fracturing, and then essentially regain its original shape and energy
dissipation potential upon removal of the load. The VTMA design was optimized
through finite element modeling using DYNA3D. This inexpensive modeling tool
resulted in a reduction in the number of expensive full-scale crash tests
required to develop the system. Computer modeling can optimize the probability
that a given full-scale crash test will be successful, removing the
"trial-and-error" approach to appurtenance design. More lives will be saved as
the resulting better understanding of the ways in which safety devices behave
under real-world impact conditions inevitably leads to more effective
designs.
John F. Carney III, Provost, WPI, 100 Institute Road, Worcester,
Massachusetts 01609-2280. Tel: (508) 831-5222 Fax: (508) 831-5774. e-mail: jfc@wpi.edu. Subhasish Chatterjee, Department Of
Civil And Environmental Engineering, Vanderbilt University, Nashville, Tennessee
37235. Tel: (615) 322-0055 Fax: (615) 322-3365. e-mail: shub@vuse.vanderbilt.edu. Richard B.
Albin, Washington State Department of Transportation, P.O. Box 47329, Olympia,
Washington 98504-7329. Tel : (360) 705-7269 Fax: (360) 705-6815, e-mail: albind@wsdot.wa.gov.
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980614 “Development of a Sequential Kinking Terminal for
W-Beam Guardrails”
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980626 “Roadside Safety Analysis Program (RSAP): A
Cost-Effectiveness Analysis Procedure”
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980765 “NCHRP Report 350 Compliance Testing of the BEST
System”
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980824 “Approach Guardrail Transition For Concrete Safety
Shape Barriers”
Abstract: W-beam guardrail has traditionally been the first choice for
use in protecting the motoring public from serious roadside hazards. One trouble
spot for this system has been the difficulty in safely treating the end of the
barrier. Early end treatment systems, including stand-up blunt ends and
turned-down terminals were inexpensive to build and maintain, but proved to be
dangerous for use on high-speed, high-volume roadways. This poor safety
performance ultimately lead the Federal Highway Administration (FHWA) ban future
use of these terminals on the National Highway System. Later terminal designs
were found to be difficult to install correctly, have compiled relatively poor
accident records, and/or have unfavorable aesthetics. .A new tangent
energy-absorbing w-beam guardrail terminal that meets NCHRP Report 350 criteria
has been developed. Conclusions: The terminal, designated the SKT-350,
dissipates the energy of an encroaching vehicle by producing a series of plastic
hinges in the w-beam as the terminal head is pushed down the guardrail. This
energy absorption concept allows for significantly lower dynamic forces on the
encroaching vehicle; reducing the vehicle damage, the weight of the terminal
head, the propensity for vehicle yaw and roll after impact, and the chances of
buckling in the w-beam section. In addition to these important safety
advantages, the terminal incorporates a unique cable anchor bracket that closely
resembles a BCT cable anchor and a novel foundation tube design that facilitates
the removal of broken posts during repair. Combining the features of reduced
forces and head weight, a simple cable box, and more economical soil tubes allow
the system to offer the advantages of both reduced cost and improved
performance.
Dean L. Sicking, John D. Reid, and John R. Rohde, Midwest
Roadside Safety Facility, University of Nebraska-Lincoln, W348 NH (0531),
Lincoln, NE 68588. Tel: (402) 472-9332 Fax: (402) 472-2022.
Abstract: Highway agencies are continually faced with decisions relating
to roadside safety, from the use and selection of specific roadside safety
features and appurtenances at spot locations and along highway sections to the
development of warrants and policies on a system-wide basis. When assessing the
use of roadside safety devices, an engineer has to weigh the relative benefits
and costs associated with the safety improvement. Many decisions are relatively
easy and are covered under established guidelines and warrants, such as the
American Association of State Highway and Transportation Officials (AASHTO)
Roadside Design Guide. For example, the need for breakaway sign and luminaire
supports along high speed facilities is well known, as is the importance of
appropriate approach guardrails and transition sections for bridge rails. This
paper presents brief descriptions of a new cost-effectiveness analysis program,
known as the Roadside Safety Analysis Program (RSAP), which was developed under
NCHRP Project 22-9. Conclusions: The RSAP program is an improvement over
existing cost-effectiveness analysis procedures for evaluation of roadside
safety improvements, such as the procedures in the 1977 AASHTO Barrier Guide and
the ROADSIDE program. The RSAP program improves on many of the algorithms in the
procedures and provides a user-friendly interface to facilitate easier use. The
program has undergone extensive testing and validation, including evaluation by
an independent reviewer. It is anticipated that the RSAP program will be
available to the public through the McTrans Center at the University of
Florida.
King K. Mak, Texas Transportation Institute, Texas A&M
University System, College Station, TX, Tel: 210-698-2068 Fax: 210-698-2068.
e-mail: king@tti3a.tamu.edu. Dean L.
Sicking, University of Nebraska, Dept. Of Civil Engineering, W348 Nebraska Hall,
Lincoln, NE 68588-0531. Tel: 402-472-9332 Fax: 402-472-8934. e-mail: dsicking@unlinfo.unl.edu. Karl
Zimmerman, 1711 Charles Street, Norman, OK 73069. Tel: 405-329-8684 Fax:
405-329-1349. e-mail: kzimman@concentric.net.
Abstract: An energy absorbing guardrail terminal was developed at the
Midwest Roadside Safety Facility in 1994 which met the safety criteria set forth
in NCHRP Report 230. This terminal, known as the Beam Eating Steel Terminal, or
BEST, relies on the cutting of steel W-beam to absorb the energy of impacting
vehicles. Since this time, a new set of safety standards has been developed to
replace those set forth in NCHRP Report 230. This new criteria is published in
NCHRP Report 350, with the most significant change being the replacement of the
4500 lb. sedan test vehicle with a 2000 kg 3/4 ton pickup. The new criteria
reflects the increase in popularity of pickups, vans, and sport utility vehicles
which have a significantly higher center of gravity than the sedans and small
cars which have been the standard for crash testing until now. In order to
insure that the BEST system would perform well under these new, and more
stringent, criteria the system was subjected to the matrix of full-scale vehicle
crash tests required by NCHRP Report 350. Several design changes were made to
the terminal system during this development to improve the performance of the
system. A series of full-scale vehicle crash tests was conducted.
Conclusions: Of the seven crash tests required by NCHRP Report 350, six
tests were successfully conducted on the system. The BEST guardrail terminal can
bring competition to the tangent energy absorbing guardrail terminal market.
Competition will not only drive the costs of guardrail terminals down, but it
will also allow some states that are precluded from making sole source purchases
to begin to use NCHRP 350 terminals. Therefore, the BEST system is believed to
offer the potential for significantly improving the safety of guardrail ends
across the nation.
Abstract: An approach guardrail transition, consisting of three-beam
guardrail, steel posts, structural tube spacer blockouts, and a New Jersey
connector plate, was developed and full-scale vehicle crash tested for use with
the New Jersey concrete safety shape barrier. Two full-scale vehicle crash tests
were performed according to TL-3 of NCHRP Report 350. Conclusions: The
first crash test, Test ITNJ-1, failed due to vehicle rollover as a result of
lower than expected post-soil forces which resulted in excessive barrier
deflections causing a higher than normal exit angle occurring simultaneously
with significant roll, pitch, and yaw angular motions. Based on knowledge gained
from test ITNJ-1, the approach guardrail transition system was redesigned. The
primary changes were to use longer posts and a stiffer NCHRP Report 350 crushed
limestone backfill. A second test, Test ITNJ-2, was performed on the modified
system and was determined to be acceptable according to the safety performance
criteria presented in NCHRP Report 350. Thus, an approach guardrail transition
for use with the New Jersey concrete safety shape barrier has been successfully
developed and meets current safety standards. It is believed that only minor
modifications to the new design will be required to accommodate the F-shape
concrete barrier. Additionally, it is believed that no further testing will be
required since the F-shape is considered to behave slightly better than the New
Jersey shape in crash testing (11-12).
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