American Association of
State Highway and Transportation Officials
Special Committee on
Research and Innovation
FY2023 NCHRP PROBLEM
STATEMENT TEMPLATE
Problem Number:
2023-C-08
Problem Title
Field
Studies of Steel Girder Fit-up
Background Information and Need For Research
The fit
condition of a steel I-girder bridge refers to the deflected geometry
associated with a specific load condition in which the cross-frames or
diaphragms are detailed to connect to the girders. With respect to vertical
deflection, girders experience three conditions from inception to fabrication
to completion of the bridge in place in the field: No-Load (NL), Steel Dead
Load (SD), and Total Dead Load (TDL). As
such, there are three fit conditions for steel girder bridges: : No-Load Fit
(NLF), Steel Dead Load Fit (SDLF), and Total Dead Load Fit (TDLF). Consideration of the fit condition is
important because the appropriate fit decision can provide significant benefit
to the constructability and the overall performance of the bridge system (1).
The AASHTO LRFD Bridge Design Specifications (Article 6.7.2) specify that the
fit condition of the cross-frames or diaphragms should be clearly stated in the
contract documents for straight I-girder bridges with skewed supports, and
horizontally curved I-girder bridges with or without skewed supports. If the appropriate fit condition is not
selected, the bridge could be subjected to problems during erection and
construction. It could also result in
systems that have errors in final steel vertical profile and cross-slope or
other long-term problems.
Past
studies of steel girder fit up have been only analytical. The project will
include field measurements of existing steel girder systems to determine the
condition of the girders relative to the design. Researchers will compare the
field results to the fit condition that the girders were fabricated to. If necessary, current guidelines will be
revised based on these field studies, and/or new guidelines on the best
detailing practices impacting girder fit-up can also be established.
Tom
Macioce of PennDOT and current Chair of AASHTO COBS Technical Committee T-14
has noted that if appropriate fit condition is not selected, the bridge could
be subjected to problems during erection and construction. It could also result
in systems that have errors in final steel vertical profile and cross slope,
bearing performance, or other long-term problems.
How is this problem statement related
to the strategic plan or research agenda of an AASHTO Committee(s) and/or
Council(s)?
|
Objective |
How this Proposed Research Responds |
|
1.
Maintain and Enhance a Knowledgeable Workforce |
The research findings would increase the
overall knowledge of steel I-girder fit condition. It would also enhance the
already analytical studies by conducting field measurements of existing
bridges. |
|
2.
Maintain and Enhance AASHTO Specifications |
The research findings could be implemented
into the AASHTO LRFD Bridge Design Specifications and/or the AASHTO LRFD
Bridge Construction Specifications. |
|
3.
Accelerate Bridge Delivery and Construction |
With a streamlined fit condition detailing
guide, designers, fabricators, and contractors will work more efficiently and
consistently. Proper fit type
selection will help to eliminate project delays that occur when girders do
not fit together. |
|
4.
Optimize Structural Systems |
The research could potentially benefit steel
I-girder bridges by enhancing constructability and long-term performance. |
Literature Search Summary
The
authors of this RNS document are not aware of any other similar research
underway.
Research Objective
The
objective of this research project is to investigate the condition of steel
girders in the field that were originally detailed for different fit conditions
and compare analytically.
Task 1 Literature Review
Task 2 Finite Element Analysis
Task 3 Existing Bridge Selection
The research team would prepare a list of potential bridge candidates to perform
the field testing on. The research team
would obtain fabrication shop drawings for each bridge selected.
Task 4 Field Measurements of
selected bridges
Task 5 FE Model Calibration and
Parametric Studies The research team would calibrate the FE Model based on
the field results from Task 4. The
research team would perform parametric studies, using finite element analysis,
to investigate the different results of girder fit condition. The team will include different girder sizes
and spans, horizontal curvature, skew angle, and other design variables in
their study.
Task 6 Review Existing Guidelines
and Develop New Guidelines The research team will review existing guidelines
(Ref 1) regarding steel bridge fit and offer revisions if necessary, or if
required, develop new guidelines for choosing the best detailing method for
steel girders.
Task 7 Develop Specification
Language The research team would review all results and propose
revisions/additions to the AASHTO LRFD Bridge Design Specification if their
recommendations differed from current practice.
Task 8
Final Report The research team would submit all research findings,
guidelines, and specification language for final review.
Urgency and Potential Benefits
This
research priority is high. The potential users of this research would be the
bridge engineering and construction community.
This project will provide a foundation to base an engineers decision on
girder-fit up and potentially have a positive impact on steel bridge
constructability. It will also provide
an assessment of long-term behavior of the girders as a function of the
as-built condition. This work is applicable to all DOTs, even states where
concrete bridges are common. Steel
bridges are often selected for complex situations such as curved bridges and
bridges with high skews. Proper
management of girder fit-up will help to eliminate problems and address common
misconceptions on complex steel bridge construction.
Implementation Considerations
The
implementation of this research can take several forms including developing a separate
guideline document or adding provisions for the AASHTO LRFD Bridge Design and
Construction Specifications.
The most
logical location to implement this research results is within existing steel
bridge guidelines that are published by the ASHTO/NSBA Steel Bridge
Collaboration. One potential document
that this information could be added to is Guideline G12.1 Guidelines to Design
for Constructability and Fabrication.
Using this AASHTO document, states can modify their design and
construction specifications to address this issue.
This
research would be of interest to several AASHTO COBS Technical Committees
including Committee T-4 Construction and T-14 Steel Bridges.
Recommended Research Funding and Research
Period
The
research effort is anticipated to last 36 months. The research effort is anticipated to cost
$500,000.
PROBLEM STATEMENT AUTHOR(s): For each author,
provide their name, affiliation, email address and phone.
Jamie
Farris, PE; Texas Dept. of Transportation; Jamie.Farris@txdot.gov
Brandon
Chavel; National Steel Bridge Alliance; chavel@aisc.org
Potential Panel Members: For each panel
member, provide their name, affiliation, email address and phone.
Members of T-14 and AKB20, Authors of
the statement
Person Submitting The Problem Statement: Name, affiliation,
email address and phone.
Jamie
Farris
512-788-4932
Jamie.farris@txdot.gov
Affiliation (limited to): Texas DOT