BACKGROUND
A combination of limited prefabricated barrier systems and the new Manual for Assessing Safety Hardware (MASH) crash testing requirements is limiting the full adoption of accelerated bridge construction (ABC) techniques by state departments of transportation (DOTs).
Precast concrete barriers were previously crash tested to requirements levels published in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. Some of these barriers were evaluated for test level (TL) 3. However, state DOTs are moving to higher level designs with TL 4 becoming more common and some state DOTs are moving to TL 5.
An ongoing pooled-fund research project TPF-5(367): Evaluation and Full Scale Testing of Concrete Prefabricated Bridge Rails (https://www.pooledfund.org/Details/Study/619)
is MASH crash-testing a precast barrier system. However, with different agencies using different barriers (F shape, single slope, etc.), a need exists for additional barrier system designs that meet the current MASH barrier design/testing provisions. In addition to accommodating accelerated construction schedule, the desired prefabricated barrier systems need to include durable connection details.
OBJECTIVE
The objective of this research is to identify, develop, and MASH crash-test durable prefabricated versions of existing MASH or NCHRP Report 350 compliant barriers.
RESEARCH PLAN
Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective.
The research plan should (1) include a kick-off teleconference with the research team and NCHRP convened within 1 month of the contract’s execution; (2) address how the proposer intends to satisfy the project objectives; (3) be divided logically into detailed tasks necessary to fulfill the research objectives and include appropriate milestones and interim deliverables; and (4) incorporate opportunities for the project panel to review, comment on, and approve milestone deliverables.
Accomplishment of the project objective(s) will require at least the following tasks.
PHASE I – Planning
Task 1. Conduct a literature review of relevant domestic and international research and current state of practice related to crash-tested barriers including previous systems, connection details, long-term durability, and materials. Include current work on prefabricated concrete barriers, with or without crash testing, connection details, and materials.
Task 2. Survey the current prefabricated barrier needs of state DOTs and other owner agencies via a questionnaire. This will include, but not limited to, the commonly used shapes, connection details, test levels for the designs, and long-term durability concerns. The research team shall obtain approval from NCHRP prior to sending the survey.
Task 3. Synthesize Tasks 1 and 2 information with focus on ABC applications and identify a minimum of three non-proprietary prefabricated concrete barriers for further evaluation and testing in Phases II and III. In the performance of this task, considerations shall be given to barriers that:
- Accommodate various geometric configurations such as vertical curves, horizontal curves, and variable cross slopes;
- Accommodate tolerances;
- Feature long-term durable connections (e.g., stainless steel, durable grouts, etc.); and
- Accommodate accelerated construction schedules (e.g., operational in under 12 hours).
Task 4. Develop a methodology for conducting the evaluation of the selected barriers. At minimum, the proposed methodology shall include details about:
- Barrier designs (several may be similar but designed for different test levels). The design portion of the process shall address the deck connection, barrier to barrier connections, variable geometry, long-term durability, and tolerances;
- Finite element analysis of connections to gain the most accurate assessment of the potential connection performance. Barrier system includes connection to deck and connection between barrier segments;
- Numerical modeling simulation;
- Impact and component tests on selected prototype designs;
- Refinement of designs and calibration of models and determination of critical impact points;
- Crash testing of concrete barrier-deck system(s) based upon American Association of State Highway Transportation Officials (AASHTO) MASH criteria;
- Number of railings to be tested (based on the available budget); and
- Preliminary design concepts of the proposed railing systems (a minimum of five). NCHRP will select a minimum of three design concepts to be developed in Phases II and III.
Task 5. Prepare Interim Report No. 1 that documents Tasks 1 through 4, includes the data archiving and sharing plan (see Special Note B), and provides an updated work plan from the proposal for the remainder of the research no later than 6 months after contract award. Railings identified and the methodology proposed in Tasks 3 and 4, respectively, will be subject to NCHRP approval. The updated work plan must describe the process and rationale for the work proposed for Phases II and III.
PHASE II— Barrier Design and Component Testing
Task 6. Conduct the analytical modeling simulation according to the approved Interim Report No.1.
Task 7. Perform component testing as needed.
Task 8. Finalize design details for the barrier systems.
Task 9. Finalize the crash testing program.
Task 10. Prepare Interim Report No. 2 that documents Tasks 6 - 9 and provides an updated work plan for the remainder of the research no later than 16 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phase III.
PHASE III— Full-Scale Crash Testing and Final Deliverables
Task 11. Perform one full-scale crash test of a barrier-deck system approved by NCHRP. Based on the test result, validate the proposed design concepts for the other barrier systems and propose any needed changes. Submit a task report for NCHRP review and approval.
Task 12. Perform the remaining full-scale crash tests after NCHRP approval of Task 11.
Task 13. Prepare final deliverables including: (1) a conduct of research that documents the entire research effort, (2) design details and drawings of the developed barrier systems, and (3) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” See Special Note E for additional information. The draft deliverables are due no later than 3 months after approval of Phase III.
STATUS: Research in Progress
