Anchored Temporary Concrete Barrier on Asphalt and Soil (405160-25)

Anchored Temporary Concrete Barrier for use on Asphalt and Soil (405160-25)

Problem Statement

Texas Transportation Institute (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. By keeping the same barrier design and making modifications to the drop-pins, it may be possible to extend the use of this pinned barrier on asphalt pavement and soil base.

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 (1). 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. This design was developed for the pooled fund states and had the primary objective of being use on thin concrete decks. The design has now been adopted by some of the participating states and there is a desire to extend the restraint design for use on asphalt and soil, while keeping the same barrier design.

In 2003, Midwest Roadside Safety Facility (MwRSF) developed a concrete bridge deck tie-down system for 12.5 ft long, F-shaped Kansas temporary barriers (2). 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 inches and 11.3 inches, respectively.

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 (3). 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. Since the barrier was placed on a 2-inch asphalt layer in the test, this design cannot be used directly on soil without further testing. Furthermore, the asphalt pavement needs to be at least 2 inches thick.

In this same study, MwRSF also 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.

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 (4). 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 modify the anchor design of the previously developed F-shaped pinned-down concrete barrier and extend its use on asphalt pavement and soil base. The new design will be developed using component level testing, FE analysis, and full-scale crash testing. The design will be required to meet AASHTO MASH test level 3 criteria.

Benefits

The new design will provide an option to restrain temporary concrete barrier on roadway surfaces other than concrete (i.e. asphalt and soil). It is expected that the final design will allow the states to use existing inventories of the pinned-down concrete barrier for this application.

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.

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

As described in previous sections, this new design is intended to be an extension of the existing design developed by the researchers for use on concrete deck or pavement. Thus the researchers will try to maintain as many features from the previous design as possible. Unless it is determined that some modification is necessary for a successful design, the researchers will use the previously developed barrier design without modifications. The anchorage of the barrier will be modified by changing the depth of the drop-pins in soil. The researchers will evaluate the appropriate depth of the drop-pins needed to restrain the barrier on soil by using a series of subcomponent level pendulum testing and simulation analysis. A full-scale crash test will be performed in the end as a final validation of the design.

The objectives of this research require that the final design of the pinned-down barrier be usable on both asphalt and soil. Among these, the use on soil is more critical in terms of lateral barrier deflections. Anchor design that works successfully on soil should perform better on asphalt layer. This is because the asphalt layer is generally stronger than soil and provides greater lateral resistance to the displacement of the inclined pins that lock the barrier in place. Thus the researchers will focus on restraining the barrier on soil. The final design however will be usable for both soil and asphalt surfaces.

The details of the work plan are described in the tasks below.

Task 1: Pendulum Testing for Pin Pullout Response

In this task, the researchers will conduct a series of pull-tests to determine the response of the inclined steel pins embedded in soil. The pins will be embedded to different depths and will be pulled by applying a lateral dynamic load using a drop pendulum. A load cell will be used to determine the lateral load applied on the pins. The lateral movement of the pins will also be measured. A total of three tests will be performed.

Task 2: Simulation Analysis for Calibrating Soil Response

In this task, the researchers will develop finite element models of the pendulum tests conducted in Task 1. By simulating the pull tests with pins at various embedment depths, the researchers will calibrate properties of the soil material model and ensure that the soil-pin interaction is adequately captured by the model. LS-DYNA finite element analysis package will be used for performing all simulations in this research.

Task 3: Simulation Analysis of Full-scale Barrier System

Using the validated soil-pin model from Task 2, the researchers will develop a full-scale model of the pinned-down barrier installation on soil. The model will include a 100-ft long installation and an impact simulation will be performed with MASH test level 3 conditions (i.e. 2270-kg pickup vehicle, impacting at 100 km/h and 25-degrees). Based on feedback from the pooled-fund states, the design will be developed for placing the barrier adjacent to a 1.5H:1V slope at a lateral offset of 1-ft from the slope breakpoint. The results of the simulation analysis will be used to evaluate the performance of the barrier for a given depth of the restraining drop-pins. The depth of the pins may be increased or decreased until desirable lateral deflection is achieved. If adequate anchoring cannot be achieved using two pins per barrier, additional pins may be added to the design.

Task 4: Full-Scale Crash Testing and Final Report

Once the anchorage design has been finalized in Task 3, the researchers will perform test 3-11 of MASH (2270-kg vehicle, 100 km/hr, 25 deg). The test will be performed to verify simulation results. It is argued that this is the critical test for this design and the test with smaller 1100-kg vehicle is not needed. Due to higher impact energy, the test with the 2270-kg pickup truck will result in greater lateral deflection and help evaluate connection strength and the tendency of the barriers to rotate. An impact resulting from the lighter 1100-kg passenger car under same impact speed and angle will not result in any increase in lateral deflection of the barrier nor will it impart a higher force on the barrier to evaluate connection strength and barrier rotation. Thus the test will be conducted with the 2270-kg pickup only.

Waskey Bridge, which is a concrete barrier manufacturer in Louisiana, has agreed to donate 12.5-ft long concrete barrier segments for this research. TTI will arrange for shipping the barriers from the manufacturer to its testing facility under this contract. In the event that Waskey Bridge is unable to donate the barriers, additional funds will be needed to construct the barriers for testing.

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.) 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.