Transition Design for Anchored to Rigid Barrier (405160-34)

Transition Design for Achored Temporary Barrier to Rigid Cconcrete Barrier (2011 LA/22)

Problem Statement

TTI recently develop a pinned down F-shape temporary concrete barrier system that provides limited lateral deflection (less than 6 inches) and can be used for bridge or roadway applications.  The design was developed for use on concrete pavements or bridge decks as thin as seven inches.  If this application is used on a road and bridge project, it is possible that this barrier section may be used during phased construction with a permanent concrete barrier section or in a permanent application when transitioning to a fixed concrete median barrier.   A transition design from the anchored precast concrete barrier to a permanent concrete barrier is needed to allow smooth redirection of impacting vehicle in this area. 

Background

In 2008, TTI developed a restrained F-shaped temporary concrete barrier design that was easy to install and minimized damage to the bridge deck or concrete pavements (Sheikh 2008). This restraint mechanism was developed for use on concrete bridge decks and pavements.  It used 1.5-inch diameter steel pins that were dropped into inclined holes cast in the toe of the barrier segments. The pins passed through the holes in the barrier and continued short distance into the underlying concrete pavement, thus locking the barrier in place. The pinned-down barrier successfully passed the National Cooperative Research Program (NCHRP) Report 350 Test Level 3 requirements. The maximum permanent and dynamic barrier deflections were 5.76 inches and 11.52 inches, respectively. There was no significant damage to the underlying concrete pavement. The design has now been adopted by some of the participating pooled-fund states and there is a desire to develop a transition for using the pinned down barrier with the rigid concrete barrier.

Among other anchored concrete barrier designs, Midwest Roadside Safety Facility (MwRSF) has developed a design for the F shape temporary concrete barrier along with various transition details.  In 2003, MwRSF developed a concrete bridge deck tie-down system for 12.5 ft long, F-shaped Kansas temporary barriers (Polivka 2003). Three anchor bolts were passed through the holes in the barrier and fastened to the bridge deck on the traffic side of the barrier. The maximum static and dynamic deflections were 3.5 in. and 11.3 in., respectively.  Later on in 2005, MwRSF developed an NCHRP Report 350 compliant tie down design for 12.5-ft long temporary concrete barriers with pin-and-loop type connection for use on asphalt pavements that are at least two inches thick (Bielenberg 2006). The barrier was installed at a 6-inch lateral offset from the edge of a ditch. This tie-down system used three 1.5-inch diameter steel pins that were driven down vertically through holes cast in each barrier segment. The pins were 3-ft long and pinned the barrier to the underlying asphalt ground.  The maximum static and dynamic deflections in the test were 11.1 inches and 21.8 inches, respectively.

In the same study, MwRSF developed a transition from the free-standing 12.5-ft long temporary concrete barrier to the anchored temporary concrete barrier design developed earlier in 2003.  The transition section comprised of four 12.5-ft long barrier segments in which steel pins were driven in through the holes in the barrier.  The number of pins in the transition barrier segments was gradually reduced to transition from the anchored to the free standing barrier. Barrier segments in the transition section of this design were placed on a 2-inch thick asphalt layer.  The barrier was installed at a 6 inch lateral offset from the edge of a ditch.  The maximum static and dynamic deflections in the test were 5.25 inches and 18.39 inches, respectively.

And more recently in 2009, MwRSF developed a transition design for attaching free-standing F-shape barrier to the rigid concrete barrier (Wiebelhaus et al., 2009).  This design employs the anchored barrier section developed by MwRSF earlier in 2005 and an intermediate section to transition from the free-standing to the rigid barriers.  At one end the anchored barrier segments connect to the free-standing barrier, and at other end they connect to a rigid concrete barrier.  A 42-inch tall single slope barrier was used as the rigid barrier system.  The number of pins in the anchored barrier segments was varied to gradually increase the lateral restraint of the barrier over four 12.5-ft long segments.  The anchored barrier segments were place on a 3-inch thick asphalt pad.  To reduce snagging of the vehicle while transitioning from anchored barrier to the rigid barrier, a nested 12-guage thrie beam section was used.  The rail segment was attached to the traffic side face of the rigid and the anchored barrier segments.

In 1999, California Department of Transportation (Caltrans) developed a pinning/staking configuration for its 20-ft long, NJ profile concrete barriers connected with a pin-and-loop type connection (Jewel 1999).  The configuration met NCHRP Report 350 evaluation criteria and consisted of four 1-inch diameter pins that were driven 16.5 inches vertically into the underlying asphalt pavement. Each barrier segment was pinned at its four corners. The barrier was tested in a median configuration and there was no ditch or slope behind the barrier. The maximum static and dynamic deflections of the system were 2.75 inches and 10 inches, respectively.

Objective

The objective of this research is to develop and crash test a transition design that can be used to transition from the pinned-down F-shape temporary concrete barrier placed on concrete to a permanent concrete barrier. The transition is to be developed for American Association of State Highway and Transportation Officials Manual for Assessment of Safety Hardware (MASH) test level 3 criteria, using the existing pinned F-shape temporary concrete barrier design to the extent possible.

Benefits

A successful transition detail can be applied in situations when the pinned-down barrier transitions to permanent concrete barrier.  The design will result in successful redirection of impacting vehicles in the transition zone as per the MASH test level 3 requirements. 

Products

TTI will provide composite video and photographic documentation of the crash test and a final report suitable for submittal to Federal Highway Administration (FHWA) documenting the research and/or testing performed.  Discussion needed to request FHWA’s acceptance of the concrete barrier system for use on the National Highway System will be provided. 

TTI will further provide drawings of the concrete barrier system and of each of the components of the system in the format required for inclusion in hardware standards documents of the AASHTO-ATRBA-AGC Task Force 13.

A copy of all deliverables will be provided for each participating member state.

Implementation

As stated above, TTI will provide all the supporting information and written discussion for submitting a request to FHWA for acceptance of the concrete barrier system for use on the National Highway System.

The research will provide information and documentation on testing of the concrete barrier system so that design and operational standards can be further reviewed and evaluated. Detailed engineering drawings that will facilitate development of standards sheets and specifications will be provided to each participating state.

Drawings provided for Task Force 13 documents will further support implementation of the research. 

Work Plan

The work plan for this research will comprise of three tasks as described below. 

Task 1: Conceptual Design

In this task, the researchers will evaluate rigid concrete barrier systems used by the participating pooled fund states to select a system that is most critical for the transition design. The researchers will develop conceptual designs of the transition based on evaluation of existing transition systems. The conceptual design will take into consideration compatibility with research being performed under Task Order LA/26 (to develop transition design for connecting anchored barrier to free-standing barrier).  The transition concept selected will be presented to the Task Order Technical Representative for approval before further design and development. 

Task 2: Finite Element Analysis

In this task, the researchers will develop full-scale finite element system model of the transition concept selected in Task 1.  Once the system model has been developed, the researchers will perform vehicular impact simulations using MASH TL-3 impact conditions (i.e. 2270-kg pickup vehicle, impacting at 100 km/h and 25-degrees) to evaluate the design’s performance.

Most longitudinal barrier transitions have two points of transition of the barrier’s lateral stiffness.  In this design, there will be a transition point when the vehicle approaches from the rigid barrier to the pinned-down barrier, and another transition point when the vehicle approaches from the pinned-down barrier to the rigid barrier.  Crash testing is generally required to demonstrate adequate performance of the transition at both of these locations.  However, it can be argued that due to the limited deflection of the pinned-down barrier observed in previous testing, this transition design will not result in excessive change in lateral barrier stiffness.  Thus the performance differences between the two transition points will not be too significant.  The researchers will however perform impact simulations to determine the critical impact point (CIP) for both transition locations (from rigid to pinned-down barrier and from pinned-down to rigid barrier) and then evaluate the most critical case.  Also based on this expectation, the researchers have budgeted only one crash test at the CIP determined to be most critical from the simulation analysis. It should be noted that if simulation results indicate significant differences in performance between transitioning from rigid to pinned-down and pinned-down to rigid barrier, additional crash test may need to be performed under a separate contract to evaluate both transition points. 

Task 3: Full-Scale Crash Testing and Final Report

Once the transition design has been finalized in Task 2, the researchers will perform test 3-21 of MASH (2270-kg vehicle, 100 km/hr, 25 deg).  TTI will construct the rigid concrete barrier for the testing.  The current proposal and budget do not include cost of manufacturing or purchasing temporary pinned-down concrete barrier needed for the testing.  The researchers are currently working on two other Pooled-fund Task Orders that will use the same concrete barrier design.  The researchers are hopeful that sufficient length of barrier segments will be salvaged from these Task Orders for use in this study.  If however, the barrier segments are severely damaged in the previous studies and are no longer usable, it is expected that one of the Pooled Fund states will provide the barrier for testing.

The test will be performed to verify simulation results. TTI will provide the test facility, test vehicle, instrumentation of the vehicle, high-speed film, video, still photographs, and a final report suitable for submittal to Federal Highway Administration (FHWA). 

____________________
[1] Sheikh, N.M., Bligh, R.P., and Menges, W.L. (2008). “Crash Testing and Evaluation of the 12 ft Pinned F-shape Temporary Barrier.” Texas Transportation Institute, College Station, Texas.
[2] Polivka, K.A., Faller, R.K., Rohde, J.R., Holloway, J.C., Bielenberg, B.W., and Sicking, D.L. (2003). “Development and Evaluation of a Tie-Down System for the Redesigned F-Shape Concrete Temporary Barrier.” Midwest Roadside Safety Facility, Nebraska.
[3] Bielenberg, B.W., Reid, J.D., Faller, R.K., Rohde, J.R., and Sicking, D.L. (2006). “Tie-downs and Transitions for Temporary Concrete Barriers.” Transportation Research Record, TRR 1984.
[4.] Wiebelhaus, M.J., Terpsma, R.J., Lechtenberg, K.A., Reid, J.D., Faller, R.K., Bielenberg, R.B., Rohde, J.R., and Sicking, D.L. (2009). “Development of Temporary Concrete Barrier to Permanent Concrete Median Barrier Approach Transition.” Draft Report to the Midwest State’s Regional Pooled Fund Program, Transportation Research Report No. TRP 03-208-09.
[5] Jewel, J., Weldon, G., and Peter, R. (1999). “Compliance Crash Testing of K-Rail Used in Semi-Permanent Installations.” Report No. 59-680838, Division of Materials Engineering and Testing Services, CALTRANS, Sacramento, CA.