Precast Concrete Barrier Profiles / Curve Accommodation
Currently the J-J Hooks connections are approved for use with either the New Jersey Shape or F-Shape with a 24" wide base under NCHRP 350, Test Level 3 and accepted by the FHWA for use on all federal aid projects. Some states have modified the standard dimensions of New Jersey and F shape barriers, making precast barrier profiles in those states unique. J-J Hooks are also approved for the Constant-Slope Profile in selected states. MASH Test Level 3 J-J Hooks Bolt-down and Pin-down Barriers are currently undergoing approval processes across North America. For updated information on these and additional profile approvals, please contact Easi-Set at (540) 439-8911.
J-J Hooks concrete barriers are available in 8-foot, 10-foot, 12-foot, 20-foot and 30-foot sections based on state/provincial requirements. 20-foot (6.1m) and 30-foot sections are approved with additional reinforcing. Transition Sections, Bridge Barriers, and other special designs are available in some locations.
This design, known as the "New Jersey Type" or “Jersey Walls”, was developed by the New Jersey State Highway Dept. This barrier type has the ability to:
- Absorb the impact of a moving vehicle.
- Slow down the impacting vehicle quickly.
- Guide the vehicle back into its original line of travel while the operator retains control depending on impacting angle of vehicle.
These characteristics are the result of the following primary features:
- A large mass of reinforced concrete that absorbs impact and resists penetration through a controlled deflection of the barrier.
- A gently sloped ramp, which tends to raise the impacting vehicle. Contact with the undercarriage causes the vehicle to slow down rapidly, while being returned safely to its original line of travel.
Naturally, as with any other type of barrier, some vehicular damage can be expected as a result of a vehicle/barrier collision. This fact has led to much research on various profiles.
The F-Shape is a later generation of the safety shape that is intended to further limit vehicle damage. The lower sloped face redirects vehicles under low-impact conditions. During moderate to severe impacts, some energy is dissipated when the vehicle is lifted off the pavement. The F-Shape reduces this lift, which promotes better vehicle stability while maintaining vehicle redirection. In crash tests, the F-Shape has proven to be more successful in preventing rollover of smaller vehicles. The F-Shape has been found to be more effective overall than the Jersey Shape barrier in some instances.
The F-Shape is more commonly used for permanent concrete barriers. However, a few states use this shape for portable concrete barriers and it is under consideration by several others.
This barrier profile was developed because of the need for a more
consistent performance than a vertical-face concrete wall. Constant-Slope
barriers and vertical concrete walls facilitate resurfacing because
their performance is unaffected by the thickness of asphalt overlay. This
is particularly advantageous when constructing barriers on curved ramps.
Texas utilizes their Constant-Slope barrier for both permanent and temporary installations. Texas Constant-Slope barriers have been NCHRP 350, Level 4 crash tested. The tests indicate that the performance of the Texas Constant-Slope Barrier is comparable to the Jersey Shape. The Texas Constant-Slope barrier hasn't been crash-tested with tractor-trailers or other heavy vehicles.
The table below shows the minimum achievable radius correspondent to barrier length. The maximum angle between barriers is approximately 7 degrees.
- 8-foot barrier, 51 pieces, 68' radius
- 10-foot barrier, 51 pieces, 84' radius
- 12-foot barrier, 51 pieces, 100' radius
- 20-foot barrier, 51 pieces, 165' radius
- 30-foot barrier, 51 pieces, 246' radius