BACKGROUND

The current American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS) Article 4.6.2.2.2 provides approximate live load distribution factors (LLDFs) for line girder analysis of steel I-girder bridges and other beam-slab bridge types. Some of these provisions and specifically Article 4.6.2.2.2d, which covers LLDFs for exterior girders, are based on limited research, and various designers and owners have questioned their accuracy. The LLDFs in Tables 4.6.2.2.2b-1 and 4.6.2.2.2d-1 were developed assuming the presence of only end cross-frames and ignoring parapet stiffness. In addition, recent innovations in steel I-girder bridge design are facilitating the use of “lean-on bracing” framing systems on straight bridges with or without skew, which feature far fewer diaphragms or cross-frames than were traditionally used. Thus, the applicability of current AASHTO provisions is unknown. Research is needed to investigate the appropriateness of the current LLDFs for straight steel I-girder bridges using either traditional framing or lean-on bracing framing. 

OBJECTIVE

The objective of this research is to evaluate the accuracy of the moment and shear LLDFs provisions for girders in straight steel I-girder bridges with composite concrete deck when using line girder analysis methods.

Accomplishment of the project objective will require at least the following tasks.

TASKS

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 subaward 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.

Note: Proposers shall include the schedule for each phase in their research plans. The sequencing of tasks and deliverables (such as technical memorandums or summary reports) shall be structured for delivery in quarterly progress report submissions. An in-person interim meeting, to be held in Washington, DC, should follow the submission of the first interim report.

PHASE I—Planning

Task 1. Conduct a literature review of research and documents on the analysis of steel girders relevant to this research. The review shall include published and unpublished documentation and research conducted by the NCHRP; Federal Highway Administration; other national, state, and local agencies; and international organizations.

Task 2. Synthesize the results of the literature review to identify knowledge gaps related to the research objective. These gaps should be addressed in the final product or the recommended future research, as budget permits.

Task 3. Propose the research plan to be executed in Phase II to achieve the research objectives. At a minimum, the research plan shall include:

• An analytical modeling study.
• A field measurement program for use in validating the proposed analytical modeling study. Include measurements of strains (e.g., stiffness contribution and fatigue) in cross frames.
• Evaluation of various parameters including but not limited to
  • Barrier rail stiffness.
  • Diaphragm and cross frame types.
  • Lean-on bracing framing system.
• Evaluation of the applicability of AASHTO BDS Article 4.6.2.2.
• A risk-based approach to determine if the design of cross frames for fatigue is warranted.
• Sensitivity analysis on the parameters used to calculate LLDFs. Consider the use of multivariate approach, if appropriate. If not, propose alternate approach.
• Development of modifications of the existing steel girder analysis requirements, if needed. At a minimum, it shall include:
  • Potential revisions to the AASHTO LRFD BDS LLDFs for steel I-girder bridges.
  • Potential revisions to the AASHTO LRFD BDS provisions regarding the need for evaluating fatigue in cross-frame members in straight steel I-girder bridges.
  • The impact of any proposed modifications on other AASHTO specifications.
• A list of LLDFs examples to demonstrate the results of the research. Include a comparison with the existing specifications.

Task 4. Prepare Interim Report No. 1 that documents Tasks 1 through 3, includes the data archiving and sharing plan (see Special Note O), and provides an updated work plan for the remainder of the research. The updated plan must describe the process and rationale for the work proposed for Phases II and III.

Note: Following a 1-month review of Interim Report No. 1 by the NCHRP, the research team will meet with the project panel to discuss the interim report. Work on Phase II of the project will not begin until authorized by the NCHRP.

PHASE II—Execution

Task 5. Execute the research plan according to the approved Interim Report No. 1.

Task 6. Prepare draft language for consideration by AASHTO to incorporate the research results in the next update of the AASHTO LRFD BDS (herein called AASHTO Deliverable).

Task 7. Prepare LLDFs examples according to the approved Interim Report No. 1.

Task 8. Prepare Interim Report No. 2 that documents Tasks 5 through 7 and provides an updated work plan for the remainder of the research. The updated work plan must describe the process and rationale for the work proposed for Phase III.

Note: Following a 1-month review of Interim Report No. 2 by the NCHRP, the research team will meet with the project panel to discuss the interim report. Work on Phase III of the project will not begin until authorized by the NCHRP.

PHASE III—Final Products

Task 9. Revise the AASHTO Deliverable and the LLDFs analysis examples developed in Phase II after consideration of the panel’s review comments.

Task 10. Submit the final deliverables including (1) the AASHTO Deliverable, (2) a final report that documents the entire research effort, (3) LLDFs analysis examples, and (4) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” See Special Note K for additional information.

Note: Following receipt of the draft final deliverables, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the final deliverables. The budget for Phase III shall be $75,000.

SPECIAL NOTES

A. The research team should anticipate making two presentations to appropriate technical committees at AASHTO meetings.

B. Revisions to the Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs are highlighted in yellow within that document.

C. Proposals must be submitted as a single PDF file with a maximum file size of 10 MB. The PDF must be formatted for standard 8 ½” X 11” paper, and the entire proposal must not exceed 60 pages (according to the page count displayed in the PDF). Proposals that do not meet these requirements will be rejected. For other requirements, refer to chapter IV of the instructions.

D. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs have been modified to include a revised policy and instructions for disclosing Investigator Conflict of Interest. For more information, refer to chapter IV of the instructions. A detailed definition and examples can be found in the CRP Conflict of Interest Policy for Subawardees. The proposer recommended by the project panel will be required to submit an Investigator Conflict of Interest and Disclosure Form as a prerequisite for subaward negotiations.

E. Proposals will be rejected if any of the proposed research team members work for organizations represented on the project panel. The panel roster for this project can be found at https://www.mytrb.org/OnlineDirectory/Committee/Details/7233. Proposers may not contact panel members directly; this roster is provided solely for the purpose of avoiding potential conflicts of interest.

F. Proprietary Products - If any proprietary products are to be used or tested in the project, please refer to Item 6 in the Information and Instructions for Preparing Proposals.

G. Proposals are evaluated by the NCHRP staff and project panels consisting of individuals collectively knowledgeable in the problem area. The project panel will recommend their first choice proposal considering the following factors: (1) the proposer's demonstrated understanding of the problem; (2) the merit of the proposed research approach and experiment design; (3) the experience, qualifications, and objectivity of the research team in the same or closely related problem area; (4) the plan for ensuring application of results; and, if relevant, (5) the adequacy of the facilities. A recommendation by the project panel is not a guarantee of a subaward. The National Academy of Sciences (NAS - the contracting authority for the National Academies of Sciences, Engineering, and Medicine) will conduct an internal due diligence review and risk assessment of the panel’s recommended proposal before subaward negotiations continue.

H. Copyrights - All data, written materials, computer software, graphic and photographic images, and other information prepared under the subaward and the copyrights therein shall be owned by the National Academy of Sciences. The subawardee and lower-tier subawardees will be able to publish this material for non-commercial purposes, for internal use, or to further academic research or studies with permission from TRB Cooperative Research Programs. The subawardee and lower-tier subawardees will not be allowed to sell the project material without prior approval by the National Academy of Sciences. By signing a subaward with the National Academy of Sciences, subawardees accept legal responsibility for any copyright infringement that may exist in work done for TRB. Subawardees are therefore responsible for obtaining all necessary permissions for use of copyrighted material in TRB's Cooperative Research Programs publications. For guidance on TRB's policies on using copyrighted material please consult Section 5.4, "Use of Copyrighted Material," in the Procedural Manual for Subawardees.

I. The text of the final deliverable is expected to be publication ready when it is submitted. It is strongly recommended that the research team include the expertise of a technical editor as early in the project timeline as possible. See Appendix F of the Procedural Manual for Subawardees Conducting Research in the Transportation Research Board’s Cooperative Research Program for technical editing standards expected in final deliverables.

J. Proposals should include a task-by-task breakdown of labor hours for each staff member as shown in Figure 4 in the Information and Instructions for Preparing Proposals. Proposals also should include a breakdown of all costs (e.g., wages, indirect costs, travel, materials, and total) for each task using Figures 5 and 6 in the brochure. Please note that selected proposers are considered subawards to the National Academy of Sciences, the parent organization of TRB. TRB Cooperative Research Program subawards must comply with 2 CFR 200 – Uniform Administrative Requirements, Cost Principles, and Audit Requirements for Federal Awards. These requirements include a provision that proposers without a federally Negotiated Indirect Costs Rate Agreement (NICRA) or audited indirect rates shall be subject to a maximum allowable indirect rate of 15% of Modified Total Direct Costs (de minimis rate). Modified Total Direct Costs include all salaries and wages, applicable fringe benefits, materials and supplies, services, travel, and up to the first $50,000 of each lower-tier subaward. Modified Total Direct Costs exclude equipment, capital expenditures, charges for patient care, rental costs, tuition remission, scholarships and fellowships, participant support costs and the portion of each lower-tier subaward in excess of $50,000.

K. The required technical memorandum titled “Implementation of Research Findings and Products” should (a) provide recommendations on how to best put the research findings/products into practice; (b) identify possible institutions that might take leadership in applying the research findings/products; (c) identify issues affecting potential implementation of the findings/products and recommend possible actions to address these issues; and (d) recommend methods of identifying and measuring the impacts associated with implementation of the findings/products. Implementation of these recommendations is not part of the research project and, if warranted, details of these actions will be developed and implemented in future efforts.

The research team will be expected to provide input to an implementation team consisting of panel members, AASHTO committee members, the NCHRP Implementation Coordinator, and others in order to meet the goals of NCHRP Active Implementation: Moving Research into Practice, available at http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP_ActiveImplementation.pdf

L. If the subawardee is proposed to conduct less than 50% of the total effort (by time or budget), then section five of the proposal should include (1) a justification of why this approach is appropriate and (2) a description of how the subawardee will ensure adequate communication and coordination with their lower-tier subawardees throughout the project.

M. All budget information should be suitable for printing on 8½″ x 11″ paper. If a budget page cannot fit on a single 8½″ x 11″ page, it should be split over multiple pages. Proposers must use the Excel templates provided in the Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs.

N. The National Academies have an ethical and legal obligation to provide proper attribution whenever material from other sources is included in its reports, online postings, and other publications and products. TRB will review all Cooperative Research Programs draft final deliverables using the software iThenticate for potential plagiarism. If plagiarized text appears in the draft final deliverable, the research team will be required to make revisions and the opportunity to submit future proposals may be affected.

O. To ensure that data produced under this project are accessible, a data archiving and sharing plan shall be prepared by the agency performing research. The plan must be submitted with Task 4 and shall include a description of expected activities, schedules, limitations, milestones, and required resources. Researchers should describe briefly the expected schedule for data production and archive in the NCHRP permanent repository, the format of the final dataset, the documentation to be provided, and whether or not any analytic tools and/or results also will be provided. The plan must include a description of the actions planned to ensure quality. Moreover, the plan must specify the resources required to archive and distribute the data expected to be obtained in the course of performing the research. In general, public release of data will not occur before full review and approval by the NCHRP project panel.

The data archiving and sharing plan must include the following sections:

• Background and significance.
• Expected data formats.
• Description of data archiving and quality assurance plan.
• Description of data sharing plan.
• Schedule for data archiving and public release of data.
• Milestones for the implementation of the plan.
• Resources and budget.