1200 New Jersey Ave., SE

Washington, D.C. 20590

FHWA: HSST: WLongstreet: ms: x60087:3/29/11

File: h://directory folder/HSST/ B219_PA Steel Post for Underground 

Structures.docx 

cc: HSST Will Longstreet 

In Reply Refer To: 

HSST/B-219 

Mr. Mark R. Burkhead

Standards and Criteria Engineer 

Pennsylvania Department of Transportation 

Roadway Quality Assurance Division 

400 North Street, 7th Floor 

Harrisburg, PA 17120 

Dear Mr. Burkhead: 

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: W6 x 8.5 Steel Guiderail Post over Ground Structures 

Type of system: Permanent Guiderail Component 

Test Level: National Cooperative Highway Research Program (NCHRP) Report 350 

 Test Level 3 (TL-3)

Testing conducted by: Texas Transportation Institute (TTI) 

Date of Request: December 28, 2010 

Drawing Designator: SGR04-d 

You requested that we find this system acceptable for use on the NHS under the provisions of 

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. 

Decision

The following device was found acceptable, with details provided below: 

• W6 x 8.5 Steel Guiderail Post over Ground Structures 

Description

The Pennsylvania Department of Transportation (PennDOT) currently specifies W6 x 8.5 Steel 

Guiderail Post over Ground Structures detail in their existing construction standards. The detail 

includes the W6 x 8.5 steel post (post) positively anchored to a 4 ft x 4 ft x 8 in thick reinforced 

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concrete footing (R.C. footing). The current standard detail shows the R.C. footing is placed at a 

minimum depth of 6 in in compacted soil over the top of the R.C. footing. The post were welded 

to 12 in x 12 in x 3/4-in thick base plate, anchored to the R.C. footing with four (4) 7/8-in 

diameter A325 bolts cast within the R.C. footing. These anchor bolts are 8 in in length and are 

embedded a minimum of 6 in into the R.C. footings. Concrete compressive strength tests 

performed the day of the testing yielded an average compressive strength of 3669.0 psi. 

Details of this system are provided as enclosure to this correspondence.

Crash Testing

The proposed PennDOT W6 x 8.5 Steel Guiderail Post over Ground Structures (system) was 

analyzed at the test facilities at the TTI Proving Grounds Riverside Campus. Two pendulum 

tests were performed on the system. One test specified the standard R.C. footing and one test 

specified a proposed 5 ft x 5 ft x 8 in depth R.C. footing section. The objective of the pendulum 

test is to document the impact performance of the system and assess the potential for meeting the 

recommended safety performance guidelines set forth in the NCHRP Report 350 for TL-3. 

The following full-scale pendulum tests were performed on two R.C. footing designs. The post 

was loaded in bending about the strong axis. 

I. 4 ft x 4 ft x 8 in Thick R.C. Footing

The pendulum bogie, traveling at an impact speed of 21.5 mph (34.6 kph), impacted the 

guardrail post with the centerline of the pendulum nose aligned with the centerline of the steel 

post. The height of the nose was measured at 20.5 inches. At 0.020 s, the steel post began to 

deform, and at 0.032 s, the concrete footing began to lift up in the soil. The pendulum bogie 

lost contact with the steel post at 0.144 s, and exit speed at loss of contact was 7.8 mph. The 

base of the pendulum contacted the steel post at 0.332 s, and then loses contact with the steel 

post at 0.398 s. At 0.537 s, the base contacted the steel post again, and at 0.562 s, the 

pendulum went over the steel post. Maximum deflection of the steel post during the test was 

29.1 inches, and the final deformation of the post was approximately 6.5 inches. The footing 

was moved as a result of the pendulum impact on the post. The leading edge of the footing 

(traffic face edge) was uplifted and came to rest approximately 6.0 inches above the grade 

surface. After the test, no visible distress was observed in the concrete footing, post base 

plate, or anchor bolts. Maximum rise of the nose of the pendulum during the test was 

23.6 inches, and maximum crush of the honeycomb nose of the pendulum was 10.7 inches. 

Longitudinal occupant impact velocity was 20.7 ft/s (6.3 m/s), longitudinal ridedown 

acceleration was -2.9 g, and maximum 50-ms average was -8.5 g. Change in velocity at loss 

of contact was 20.1 ft/s (6.1 m/s). 

II. 5 ft x 5 ft x 8 ins Thick R.C. Footing: 

The pendulum bogie, traveling at an impact speed of 21.6 mph (34.7 kmh), impacted the 

guardrail post with the centerline of the pendulum nose aligned with the centerline of the steel 

post. The center height of the nose was 20.5 inches above finished grade. At 0.005 s, the 

steel post began to deform, and at 0.046 s, the concrete footing began to lift up in the soil. The 

pendulum bogie lost contact with the steel post at 0.155 s, and exit speed at loss of contact 

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was 8.5 mph. At 0.260 s, the concrete footing began to rotate, and at 0.352 s, the base of the 

pendulum contacted the post. The pendulum bogie came to rest on top the steel post at 

0.994 s. Maximum dynamic deflection of the steel post during the test was 20.0 inches, and 

the final deformation of the steel post was approximately 12.25 inches. The footing was 

moved as a result of the pendulum impact on the post. The leading edge of the footing 

(traffic face edge) was uplifted and came to rest approximately 3.0 inches above the grade 

surface. After the test, no visible distress was observed in the concrete footing, post base 

plate, or anchor bolts. Maximum rise of the nose of the pendulum during the test was 

24.1 inches, and maximum crush of the honeycomb nose of the pendulum was 10.1 inches. 

Longitudinal occupant impact velocity was 24.6 ft/s (7.5 m/s), longitudinal ridedown 

acceleration was -3.6 g's, and maximum 50-ms average was -8.7 g's. Change in velocity at 

loss of contact was 19.2 ft/s (5.9 m/s).

In addition to these pendulum tests, a further comparison was made between the posts and 

concrete foundations tested for this project to standard W-beam guardrail line posts embedded in 

the NCNRP Report 350 strong soil (strong soil). Two pendulum tests were performed on 

W6 x 8.5 steel posts embedded approximately 43.4 inches in strong soil (TTl Project Number

220547). For both tests, the center height of the pendulum was 18.0 in above grade. The force 

versus displacement curves for both posts tested for this project compared very closely to the 

force versus displacement curves for the same steel posts embedded in strong soil. 

Testing details of this system are provided as enclosure to this correspondence. 

Findings

The analysis of the systems described herein is as follows: 

A. The 5 ft x 5 ft footing rotated approximately 6 degrees from the pendulum impact. The 

dynamic rotation of the post was approximately 30 degrees. Plastic failure occurred in 

the W6 x 8.5 steel posts for this design tested. No distress was observed in the anchor 

bolts or concrete. The Occupant Risk Value Impact Velocity, longitudinal direction is 

24.6 ft/s (7.5 m/s). The Ridedown Acceleration for longitudinal direction is -3.6 g, with a 

maximum change in velocity of 19.2 f/s. 

B. The 4 ft x 4 ft footing rotated approximately 15 degrees from the pendulum impact. The 

dynamic rotation of the post was in excess of 30 degrees. Plastic failure occurred in the 

W6 x 8.5 steel posts for this design tested. No distress was observed in the anchor bolts 

or concrete. The Occupant Risk Value Impact Velocity, Longitudinal direction is 

20.7 ft/s (6.3 m/s). The Ridedown Acceleration for Longitudinal direction is -2.9 g, with 

a maximum change in velocity of 20.1 f/s. 

The posts anchored to the footings exhibited greater strength than those tested in strong soil over 

0 to 2 ft of displacement. The dynamic rotation of 5 ft x 5 ft R.C. footing was approximately 

30 degrees, and greater than 30 degrees for the 4 ft x 4 ft R.C. footing tested for this project. The 

dynamic rotation of the 4 ft x 4 ft R.C. footing and post was deemed undesirable since the 

footing came to rest approximately 6 in above grade surface. 

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Based on the results of this testing, the researcher recommended the W6 x 8.5 steel post 

anchored to the 5 ft x 5 ft R.C. footing for use in cases where a single post in a guardrail length 

of need interferes with an underground obstruction. The researcher further recommends a 

full-scale crash test be performed to validate the performance where multiple posts in succession 

anchored to shallow 5 ft x 5 ft concrete footing as tested herein is required. 

FHWA therefore concurs with recommendation of 5 ft x 5 ft x 8 in R.C. footing system as 

described in the request above and detailed in the enclosed drawings is acceptable for use on the 

NHS under the range of conditions tested, when such use is acceptable to a highway agency. 

Please note the following standard provisions that apply to FHWA letters of acceptance: 

• This acceptance is limited to the crashworthiness characteristics of the system 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 FHWA and the 

NCHRP Report 350. 

• To prevent misunderstanding by others, this letter of acceptance is designated as number 

 B-219 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, 

Michael S. Griffith 

Director, Office of Safety Technologies 

Office of Safety 

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Page 18 of 23 2010-12-02 

Table D1. Summary of results for pendulum test 405160-12 P1. 

0.000 s 

General Information 

 Test Agency .............................. Texas Transportation Institute 

 Test No. ............................................................. 405160-12 P1 

 Date ....................................................................... 2008-09-17 

Test Article 

 Type ........................ Steel Posts over Underground Structures 

 Installation Height (m) ............................................ 28.5 inches 

 Material of Key Element............................... W6x8.5 steel post 

Soil Type .................. 60-inch Concrete footing in Standard Soil 

Test Vehicle 

 Type ................................................................................ Bogie 

 Designation .............................................................. Pendulum 

 Test Inertia Mass ........................................................... 839 kg 

Impact Conditions 

 Speed ........................................................................ 21.6 mi/h 

 Angle ............................................................................ 90 deg 

Occupant Risk Values 

 Impact Velocity 

 Longitudinal direction ................................. 24.6 ft/s (7.5 m/s) 

 Ridedown Accelerations 

 Longitudinal direction .................................................. -3.6 g’s 

Maximum Change in Velocity .................................... 19.2 ft/s 

0.146 s 

0.289 s 

0.434 s 

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