COMPLIANCE TESTING OF IOWA’S SKID-MOUNTED SIGN DEVICE

A wide variety of traffic control devices are used in work zones, some of which are nont ormally found on the roadside or in the traveled way outsideofthe work zones. These devices are used to enhance the safety of the work zones by controlling the traffic through these areas. Due to the placement of the traffic control devices, the devices themselves may be potentially hazardous to both workers and errant vehicles. The impact performance of many work zone traffic control devices is mainly unknown and to date limited crash testing has been conducted under the criteria of National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The objective of the study was to evaluatethe safety performance of existing skid-mounted sign supports through full- scale crash testing. Two full-scale crash tests were conducted on skid-mounted sign supports to determine their safety performance according to the Test Level 3 (TL-3) criteria set forth in the NCHRP Report No. 350. The safety performancevaluations indicate that these skid-mounted sign supports did not perform satisfactorily in the full-scale crash tests. The results of the crash tests were documented, and conclusions and recommendations pertaining tothe safety performance of the existing work zone traffic control devices were made

DEVELOPMENT OF A TL-3 F-SHAPE TEMPORARY CONCRETE MEDIAN BARRIER

A temporary concrete median barrier (CMB) was designed and tested for compliance under the Test Level 3 (TL-3) guidelines specified in the Recommended Procedures for the Safety Performance Evaluation of Highway Features, National Cooperative Highway Research Program (NCHRP) Report No. 350. The barrier is built to the new metric standards and has a traditional pin and loop configuration for interconnection. The objective of this research project was to develop and evaluate a standardized, temporary concrete barrier design while addressing the concerns for safety, economy, structural integrity, constructability, ease of installation, and maintenance. The resulting F-shape barrier segment is 3,800-mm long, a length that reduced the number of connections while limiting the weight of the barriers to ease handling. Full-scale crash testing demonstrated several critical design features. First, the connections need to be tight initially as practicable to limit deformation and rotation of the barriers,. Secondly, the pin needs to restrain the longitudinal barrier forces. Full-scale compliance testing of the final design demonstrated that the barrier was capable of successfully redirecting the 2000-kg vehicle. The vehicle demonstrated significant roll after contact with the barrier, which is evidenced in a majority of other concrete barrier tests. This barrier provides economical work zone protection applicable in a variety of situations, where TL-3 test criteria is warranted

Crash-Tested Bridge Railings for Timber Bridges

Bridge railing systems in the United States historically have been designed on the basis of static load criteria given in the AASHTO Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989 AASHTO published Guide Specifications for Bridge Railings, which gives the recommendations and procedures to evaluate bridge railings by full-scale vehicle crash testing. In 1993 NCHRP published Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, which provides criteria for evaluating longitudinal barriers. From these specifications, a cooperative research program was initiated to develop and crash test several bridge railings for longitudinal wood decks. The research resulted in the successful development and testing of five bridge railing systems for longitudinally laminated wood bridge decks in accordance with the AASHTO Performance Level 1 and Performance Level 2 requirements and the Test Level 4 requirements of NCHRP Report 350

SAFETY PERFORMANCE EVALUATION OF MICHIGAN’S 4X5 PORTABLE SIGN SUPPORT

A wide variety of traffic controlling devices are used in work zones, some of which are not normally found on the roadside or in the traveled way outside of the work zones. These devices are used to enhance the safety of the work zones by controlling the traffic through these areas. Due to the placement of the traffic control devices, the devices themselves may be potentially hazardous to both workers and errant vehicles. The impact performance of many work-zone traffic control devices is mainly unknown and to date limited crash testing has been conducted, under the criteria of National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The objective of the study was to evaluate the safety performance of Michigan’s existing work-zone traffic control device through full-scale crash testing. A total of two full-scale crash tests were conducted on one 4-ft by 5-ft portable tall-mounted, rigid rectangular-shaped plywood panel sign support to determine its safety performance according to the Test Level 3 (TL-3) criteria set forth in the NCHRP Report No. 350. Neither of impacts on the tall-mounted, rigid panel sign supports resulted in acceptable safety performances. Following the analysis of these crash tests as well as the test results from other testing programs, it has been found that slight variations in design features of the work-zone traffic control devices can lead to very different performance results. Therefore, extreme care should be taken in applying crash test results from one work-zone traffic control device to similar work- zone traffic control devices with slight variations. The results of the crash tests were documented, and conclusions and recommendations pertaining to the safety performance of the existing work-zone traffic control devices were made

On two intrinsic length scales in polymer physics: topological constraints vs. entanglement length

The interplay of topological constraints, excluded volume interactions, persistence length and dynamical entanglement length in solutions and melts of linear chains and ring polymers is investigated by means of kinetic Monte Carlo simulations of a three dimensional lattice model. In unknotted and unconcatenated rings, topological constraints manifest themselves in the static properties above a typical length scale $dt \sim 1/\sqrt{l\phi}$ ($\phi$ being the volume fraction, $l$ the mean bond length). Although one might expect that the same topological length will play a role in the dynamics of entangled polymers, we show that this is not the case. Instead, a different intrinsic length de, which scales like excluded volume blob size $\xi$, governs the scaling of the dynamical properties of both linear chains and rings.Comment: 7 pages. 4 figure

STATIC TESTS ON COLLAPSING GUARDRAIL DESIGNS

A modified turned-down guardrail terminal which uses retrofit clips to hold up the guardrail has been in use on Nebraska Highways for several years. During this time, the Nebraska Department of Roads has become aware of a problem with this design. After being exposed to temperature fluctuations and vibrations from passing traffic the retrofit clips expand and the guardrail drops to the ground. Twelve different designs were tested on an actual guardrail field installation and a design consisting of strategically placed shear bolts was recommended

Railing Systems for Use on Timber Deck Bridges

Bridge railing systems in the United States have historically been designed based on static load criteria given in the AASHTO Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989, AASHTO published the Guide Specifications for Bridge Railings, which gave the recommendations and procedures to evaluate bridge rails by full-scale vehicle crash testing. In 1993, the National Cooperative Highway Research Program (NCHRP) published Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, which provided criteria for evaluating longitudinal barriers. Based on these specifications, a cooperative research program was initiated between the University of Nebraska-Lincoln and the Forest Products Laboratory, and later the FHWA, to develop and crash test 11 bridge rails for wood deck bridges. The research that resulted in successful development and testing of 11 bridge railing systems for longitudinally and transversely laminated wood bridge decks in accordance with AASHTO Performance Level 1 and 2 (PL-1 and PL-2) requirements and Test Levels 1, 2, and 4 (TL-1, TL-2, and TL-4) requirements of NCHRP Report 350 are described here

FULL-SCALE VEHICLE CRASH TEST ON THE IOWA STEEL TEMPORARY BARRIER RAIL

One full-scale vehicle crash test was conducted on the Iowa Steel Temporary Barrier Rail. Test 15-1 was conducted with at 5,500 pound vehicle at 22.5 degrees and 60.6 mph. The overall test length of the barrier was 200 feet. The barrier was shop fabricated and transported to the test site in 20 foot length sections. The cross-section of the barrier consisted of two stacked steel HP 14x73 (A36) shapes with the edges of the flanges placed back to back and held together by welded steel straps spaced 5 feet on centers. The inside box section between the HP shapes was filled with concrete. The height of the barrier was 29 inches. The 20 foot length sections were bolted together at the test site. The location of the vehicle impact was 100 feet from the end of the barrier installation. This was also the location where two sections were bolted together. The test was evaluated according to the safety criteria in NCHRP 230 and also in the AASHTO guide specifications, performance level 2. The safety performance of the Iowa Steel Temporary Barrier Rail was determined to be satisfactory

EVALUATION OF AN EXISTING STEEL POST ALTERNATIVE FOR THE THRIE BEAM BULLNOSE GUARDRAIL SYSTEM

Recently, the Minnesota Department of Transportation (MnDOT) funded a research project through the Midwest States Regional Pooled Fund to evaluate an existing steel post alternative for the thrie beam bullnose barrier system previously developed at the Midwest Roadside Safety Facility (MwRSF). MnDOT had an interest in the replacement of the wooden breakaway posts used in the current bullnose system with proprietary breakaway steel posts. The research project consisted of evaluation of current breakaway steel post designs, investigation and selection of a candidate post design, and full-scale testing of the bullnose system with a steel post alternative. The full-scale testing was to consist of two tests conducted according to the evaluation criteria of NCHRP Report 350: 1) Test 3-38, an impact of a 2000P vehicle on the Critical Impact Point (CIP) of the system at a speed of 100 km/h and an angle of 20 degrees, and 2) Test 3-31, an impact of a 2000P vehicle with the center of the vehicle aligned with the center of the nose of the system at a speed of 100 km/h and an angle of 0 degrees. The evaluation of the steel post alternative for the bullnose system project has been completed. A steel post alternative was selected followed by two full-scale crash tests. Unfortunately, both crash tests failed as the vehicle in each test ramped up the guardrail and vaulted the system. This letter summarizes the work completed