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                Safety Eligibility Letter B-180
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-180
                          **Date:**
            09/08/2008
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            MWRSF
                          **Device Description:**
            CMB Tiedowns and Transitions
                          **View PDF:**
            b180.pdf (2.73 MB)
    
    Safety Eligibility Letter B-180

			 
			**Download Version**PDF [2.73 MB]
			
			DOT logoU.S. Department of Transportation**Federal Highway Administration**
			1200 New Jersey Ave. S.E.Washington, D.C. 20590
			September 8, 2008
			In Reply Refer To: HSSD/B-180
			
			Mr. Bob Bielenberg  
		    Research Associate Engineer  
		    Midwest Roadside Safety Facility  
		    University of Nebraska â€“ Lincoln  
		    P.O. Box 880529
Lincoln, NE 68588-0529
			Dear Mr. Bielenberg:
			This letter is in response to your request for the Federal Highway Administration (FHWA)  acceptance of a roadside safety system for use on the National Highway System (NHS).
			Name  of system:Tie-down system for temporary concrete barrier on asphaltTransition system for temporary concrete barrier on asphaltType of system:Portable concrete F-Shape barrierTest Level:NCHRP Report 350 Test Level 3 (TL-3)Testing conducted by:Midwest Roadside Safety Facility (MwRSF)Test Sponsors:Florida Department of Transportation and the Midwest States Pooled Fund ProgramDate of request:January 30, 2008You requested that we find this system acceptable for use on  the NHS under the provisions of the National Cooperative Highway Research  Program (NCHRP) Report 350 "Recommended Procedures for the Safety Performance  Evaluation of Highway Features."
			**Requirements**Roadside safety systems should meet the  guidelines contained in the NCHRP Report 350. FHWA Memorandum "ACTION:  Identifying Acceptable Highway Safety Features" of July 25, 1997, provides further  guidance on crash testing requirements of longitudinal barriers. You have also chosen to anticipate the  adoption of the Manual on  Assessing Safety Hardware-2008 (MASH08), an option that FHWA has  offered with the understanding that additional testing may need to be done if  changes to the test criteria are made before MASH08 is formally adopted.
			**Description** Your request covers two applications of  portable F-shape concrete barriers on asphalt pavements. The barrier used was  the Kansas  F-shape temporary concrete barrier that was developed for bolting through to  concrete roadways. The barrier segments  were 3.81 m (12.5 ft) long and 813 mm (32 in) tall with three 51 mm  (2.0 in) diameter holes cast on each side in the toe of the barrier. Additional steel reinforcement was required  around the holes to provide sufficient resistance and containment for the  retainer bolts. As seen in the drawings  enclosed for reference, adjacent barriers were joined using a pin and loop  connection comprised of three sets of rebar loops – two at the top of one  barrier meeting one on the top of the other barrier, and vice-versa on the bottom. This detail provided double shear at two  locations on each pin, eliminating the need for a retainer bolt at the bottom  of the pin.
			The first application was placement of  the barrier near the edge of an asphalt pavement adjacent to a drop off. To limit deflection and rotation of the  barrier 38.1 mm (1. 5 inch) diameter steel pins were inserted through the  tie-down holes in the traffic side face of the barrier and driven through the  asphalt pavement. Steel plates are  welded near the top of the pins to help constrain the barrier upon impact. The system was crash tested on a 51 mm (2 in)  thick asphalt pad. The second application was a transition  between a free-standing Kansas  F-shape temporary barrier on asphalt pavement, and a rigid concrete barrier. The transition used four barrier units and 38.1  mm (1.5 inch) diameter pins. The first  unit in the transition had one pin at the down stream end. The second unit had pins installed in the two  outside hole locations. The final two  units had all three pins installed. All  pins were installed in the traffic side face of the barrier. In addition, nested 12 ga thrie beam was  bolted across both sides of the barrier at the joint between the pinned  barriers and the rigid barrier to reduce the potential for vehicle snagging at  the joint.
			**Crash  Testing** One NCHRP Test 3-11 using the 2000P  vehicle was conducted on each application.  The test data summary sheets are enclosed for reference. The FTB-1 was the test of the tie-down  design, and FTB-2 was the test of the transition. In test FTB-1 the asphalt pavement fractured  when the barrier was struck, leading to a maximum dynamic deflection of 554 mm  (21.8 in) and a permanent set of 283 mm (11.1 in).
			In test FTB-2 the impact point was  evaluated using finite element analysis, and it was determined that the  critical impact point was just upstream of the joint between the first two  pinned barriers (the first having one pin in the downstream hole only, and the  second barrier having pins at the two ends.) Because of the known stiffness of the next two  barriers anchored with three pins, it was determined that the connection  between the last two pinned barriers and the rigid concrete barrier would not  require a separate crash test. Upon  impact the vehicle was redirected with the right rear tire and the pickup truck  box landing on the top of the barrier on the traffic side before exiting the  system. The maximum permanent set and  dynamic barrier deflections were measured to be 133 mm (5.25 in) and 467 mm  (18.375 in), respectively.
			Results of FTB-1 and FTB-2 met the test  and evaluation criteria in NCHRP Report 350 for Test 3-11.
			**Findings** You asked for acceptance of both the tie-down system for  F-shape temporary concrete barriers on asphalt pavements and the approach  transition between free-standing temporary concrete barriers and rigid concrete  barrier. The tie-down system for F-shape  temporary concrete barriers on asphalt pavements was tested with the back face  of the barriers positioned 0.15 m (6 in) from the edge of a vertical drop-off  in order to represent a worst case impact scenario. You also requested that the tie-down system  be accepted for both installations adjacent to a drop-off as tested and  installations on standard asphalt paved surfaces. This request is based on the successful  results from the dynamic component testing, computer simulation modeling of the  barrier system, and full-scale vehicle crash testing of both the tie-down and  approach transition designs. We concur  in these requests.
			The tie-down system for temporary concrete barrier on  asphalt and transition system for temporary concrete barrier on asphalt  described above and detailed in the enclosed drawings are acceptable for use on  the NHS under the range of conditions tested, when such use is acceptable to a  highway agency.
			In your original letter requesting acceptance MwRSF also  noted some specific recommendations for the tie-down and transition regarding  the use of the system near a drop-off. You  also made a recommendation regarding the use of the tie-down and transition  with other barrier designs. We concur  that these recommendations should be included in the letter.
			"It should also be noted that the tie-down and transition  systems described herein were designed for use with the Kansas F-shape temporary concrete barrier  system, and therefore, they should not be used with other temporary barrier  systems or joint connections without further study. Although it is very likely  that this tie-down system can be adapted to other approved temporary barrier  systems, it is necessary to utilize some criteria to aid in that  determination. They are as follows:
			Joints between barrier segments must have comparable or  greater torsional rigidity about the longitudinal barrier axis when compared to  that of the as-tested configuration.
				 Alternative barrier segment lengths would be acceptable  as long as they are at least 3.81-m (12.5 ft) long and utilize  an equivalent or greater number of anchors per foot of barrier length. With shorter barrier lengths, it is believed  that additional barrier rotation will occur due to the greater number of  joints, thus resulting in the propensity for increased climbing and rollover.
				 Alternative barrier segments should have comparable  mass per unit length.
				 Alternative barrier segments should have equal or  greater reinforcement than the F-shape barrier described herein. This reinforcement recommendation is to  include the longitudinal steel, shear stirrups, and containment steel bars  surrounding the anchor boxes used with the vertical anchor rods.
				 The shape of alternative barrier segments may require  further study. Past research has shown  that the F-shape provides slightly improved results over those observed using  the New Jersey  shape barrier. Therefore, further study  may be needed to assure safe performance when applying the designs to other  barrier shapes."Please note the following standard  provisions that apply to the FHWA letters of acceptance:
            This acceptance is limited to the  crashworthiness characteristics of the systems and does not cover their  structural features, nor conformity with the Manual on Uniform Traffic Control  Devices.
              Any changes that may adversely  influence the crashworthiness of the system will require a new acceptance  letter.
              Should the FHWA discover that the  qualification testing was flawed, that in-service performance reveals  unacceptable safety problems, or that the system being marketed is  significantly different from the version that was crash tested, we reserve the  right to modify or revoke our acceptance.
              You will be expected to supply  potential users with sufficient information on design and installation  requirements to ensure proper performance.
              You will be expected to certify to  potential users that the hardware furnished has essentially the same chemistry,  mechanical properties, and geometry as that submitted for acceptance, and that  it will meet the crashworthiness requirements of the FHWA and the NCHRP Report  350.
              To prevent misunderstanding by others,  this letter of acceptance is designated as number B-180 and shall not be reproduced  except in full. This letter and the test  documentation upon which it is based are public information. All such letters and documentation may be  reviewed at our office upon request.
            This acceptance  letter shall not be construed as authorization or consent by the FHWA to use,  manufacture, or sell any patented system for which the applicant is not the  patent holder. The acceptance letter is  limited to the crashworthiness characteristics of the candidate system, and the  FHWA is neither prepared nor required to become involved in issues concerning  patent law. Patent issues, if any, are  to be resolved by the applicant.Sincerely yours,
						Signature of David A. Nicol
						David A. Nicol, P.E.Director, Office of Safety DesignOffice of SafetyImage of Triton Barrier®TL-1 Section, TRI White or Orange
			Images of crash resultsGeneral InformationTest AgencyE-TECH Testing Services, Inc.Test DesignationNCHRP 350 Test 1-11Test No.01-4318-001Date8/28/07Test ArticleTypeEnergy Absorption Systems. Inc.TRITON BARRIER TL-1 SystemInstallation Length29.7 m - (15) sections total, pinned and freestandingSize and/or dimension and material of key elementsPolyethylene Plastic sectionLength -  1981 mmWidth - 533 mmHeight - 813 mmMass - 45 kg (empty)/595 kg (full)Foundation and AnchoringPortland Cement Concrete, clean and dry, unanchoredTest VehicleTypeProduction ModelDesignation2000PModel1988 Chevrolet C2500 PickupMass (kg)Curb1939Test inertial1994DummyN/AGross Static1994Impact ConditionsSpeed (km/h)51.6Angle (deg)25Impact Severity (kJ)36.6
					Exit ConditionsSpeed (km/h)N/AAngle (deg)N/AOccupant Risk ValuesImpact Velocity (m/s)x-direction5.0y-direction0.7Ridedown Accelerations (g's)x-direction-3.9y-direction-2.6European Committe for Normalization (CEN) ValuesTHIV (km/h)18.4PHD (g's)4.5ASI0.3Post-Impact Vehicular Behaviour (deg - rate gyro)Maximum Roll Angle32.4Maximum Pitch Angle-11.8Maximum Yaw Angle25.4Test Article Deflection (m)Dynamic2.7Permanent2.7Vehicle Damage (Primary Impatc)ExteriorVDSLFQ-2CDC11FLEW2InteriorVCDIAS0000000Maximum Deformation (mm)N/A**Figure 1. Summary of Results - TRITON BARRIER TL-1 Test -1-4318-001** U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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