BACKGROUND

Currently, in the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS), the nominal flexural resistance of I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal is conservatively not allowed to exceed first yield at the strength limit state for the following reasons: 

• Such bridges typically experience significant differential vertical deflections at the cross-frames resulting in larger cross-frame forces in the elastic range. As interior-pier sections yield and begin to lose stiffness and shed their load, the forces in the adjacent cross-frames will increase. There is currently no established procedure to predict the resulting increase in the forces without performing a refined nonlinear analysis. 
• In horizontally curved bridges and severely skewed straight bridges with discontinuous cross-frames, significant lateral flange bending effects can occur. The resulting lateral bending moments and stresses are amplified in the bottom compression flange adjacent to the pier as the flange deflects laterally. There is currently no means to accurately predict these amplification effects as the flange is also yielding.
• Skewed supports also result in twisting of the girders, which is not recognized in plastic-design theory. The relative vertical deflections of the girders create eccentricities that are also not recognized in the theory.

Research is needed to address these load and resistance factor design (LRFD) issues to help state departments of transportation (DOTs) achieve more efficient designs and recognize improved accuracy in load ratings for existing bridges. 

OBJECTIVE

The objective of this project is to develop a methodology to determine the nominal flexural resistance beyond first yield at the strength limit state in I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal. 

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 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.

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.

PHASE I—Planning 

Task 1. Conduct a literature review of research and documents on the design and analysis of steel I-girder bridges relevant to this research. The review shall include published and unpublished documentation, past surveys, and research conducted through the NCHRP; the Federal Highway Administration; other national, state, and local agencies; international organizations; and industry groups.

Task 2. Identify and engage key stakeholders (e.g., AASHTO Technical Committee for Steel and Metal, state DOTs, consulting engineers, industry) to seek input on the state of the practice and to define practical and realistic I-girder bridge parameters.

Task 3. Based on the results of Tasks 1 and 2, identify knowledge gaps related to the project objective. These gaps should be addressed in the final product or the recommended future research, as budget permits.

Task 4. Propose the research plan to be executed in Phase II to achieve the project objective. At a minimum, the research plan shall include:

• An analytical investigative approach that considers the material and geometric non-linear responses of the structures.
• An examination of the AASHTO LRFD BDS requirements for the design, analysis, and load rating of I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal.
• A study of the effects of exceeding the moment at first yield at the strength limit state in (1) composite sections in negative flexure, or non-composite sections, with compact or noncompact webs and (2) composite sections in positive flexure that would otherwise qualify as compact sections. Include consideration of cross-frame forces, flange lateral bending moments and stresses (and the amplification of those moments and stresses as applicable), and torsional displacements of the girders.
• Developing recommendations for modifications of the existing steel girder design requirements, if needed.
• A list of design examples to demonstrate the results of the research.

Task 5. Prepare Interim Report No. 1, which documents Tasks 1 through 4 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 in person 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 6. Execute the research plan according to the approved Interim Report No. 1.

Task 7. Prepare draft language for consideration by AASHTO to incorporate the research results in the next update of the AASHTO LRFD BDS (herein called the AASHTO Deliverable).

Task 8. Prepare design examples according to the approved Interim Report No. 1.

Task 9. Prepare Interim Report No. 2, which documents Tasks 6 through 8 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 10. Revise the AASHTO Deliverable and the design examples developed in Phase II after consideration of the panel’s review comments.

Task 11. Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products” (see Special Note K for additional information).

Task 12. Submit the final deliverables including (1) the AASHTO Deliverable, (2) a final report that documents the entire research effort, (3) the design examples, and (4) the stand-alone technical memorandum, Implementation of Research Findings and Products.

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 $50,000.

SPECIAL NOTES

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

B. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs were revised in May 2024. Please take note of the new and revised text which is highlighted in yellow.

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 V 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 Contractors. The proposer recommended by the project panel will be required to submit an Investigator Conflict of Interest and Disclosure Form as a prerequisite for contract 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/7069 . 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; (5) how the proposer approaches inclusion and diversity in the composition of their team and research approach, including participation by certified Disadvantaged Business Enterprises; and, if relevant, (6) the adequacy of the facilities. A recommendation by the project panel is not a guarantee of a contract. 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 contract negotiations continue. 

Note: The proposer's approach to inclusion and diversity as well as participation by Disadvantaged Business Enterprises should be incorporated in Item 11 of the proposal.

H. Copyrights - All data, written materials, computer software, graphic and photographic images, and other information prepared under the contract and the copyrights therein shall be owned by the National Academy of Sciences. The contractor and subcontractors 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 contractor and subcontractors will not be allowed to sell the project material without prior approval by the National Academy of Sciences. By signing a contract with the National Academy of Sciences, contractors accept legal responsibility for any copyright infringement that may exist in work done for TRB. Contractors 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 Contractors.

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 Contractors 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 TRB Cooperative Research Program subawards (selected proposers are considered subawards to the National Academy of Sciences, the parent organization of TRB) 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) shall be subject to a maximum allowable indirect rate of 10% of Modified Total Direct Costs. Modified Total Direct Costs include all salaries and wages, applicable fringe benefits, materials and supplies, services, travel, and up to the first $25,000 of each lower tier subaward and subcontract. 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 and subcontract in excess of $25,000.

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 team proposes a Principal Investigator who is not an employee of the Prime Contractor, or if the Prime Contractor 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 Prime Contractor will ensure adequate communication and coordination with their Subcontractors 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.