This month’s newsletter includes information about:
- NSBA Issues Guidance on Fit of Skewed and Curved Steel Girder Bridges
- Webinar: Prefabricated Steel Girder Bridge Deck Units
- LRFD Simon Update
- Surface Preparation of Weathering Steel
- Alexander D. Wilson Named Recipient of 2014 SMDI/AASHTO Richard S. Fountain Award
- Transportation Research Board Issues New Research Request for Proposals
NSBA Issues Guidance on Fit of Skewed and Curved Steel Girder Bridges
A free new document titled “Skewed and Curved Steel I-Girder Bridge Fit,” developed by the NSBA Technical Subcommittee, provides designers with guidance on determining the appropriate fit for skewed and curved steel I-girder bridges.
"Fit decisions are made on every steel bridge, and sometimes this decision has a significant impact on constructability or loads,” said Ronnie Medlock, P.E., vice president of technical services at High Steel Structures in Lancaster, Penn. (an AISC/NSBA member and AISC certified fabricator), and head of the NSBA Technical Subcommittee. “The summary raises awareness about the importance of fit, describes how fit comes to play in I-girder bridge construction and provides guidance on how to handle fit, especially for skewed and curved I-girder bridges."
As roadway alignments and interchanges become more complex, steel girders are the preferred solution for skewed and curved bridges required to accommodate the roadway. However, the design and detailing of these bridges must recognize and allow for change of shape of the steel girders, as dead load is incrementally applied during the process of construction.
This document discusses the issue and offers recommendations to ensure a trouble-free project. It includes information on effects of twisting girders as well as detailing of cross bracing and diaphragms when differential deflection is present in the I-girders.
The document is available for free downloading at www.steelbridges.org/bridgefit.
The Weaver Road Bridge in Douglas County, Ore. Photo: Courtesy of OBEC Consulting Engineers
Webinar: Prefabricated Steel Girder Bridge Deck Units
On November 4 come learn about the use of prefabricated steel girder bridge decks, presented by the Accelerated Bridge Construction University Transportation Center (ABC-UTC). The presentation, offered as part of ABC-UTC’s new in-depth webinar series, focuses on the use of prefabricated steel girders in the Massachusetts I93FAST14 project. The program is broken up into six modules with each module focusing on a specific aspect of the project. Module topics range from planning and preliminary design to design detailing of the superstructure to the construction of the project.
In 2011 the Massachusetts Department of Transportation effectively used Prefabricated Steel Girder Bridge Deck Units to replace 14 interstate bridges in a 10-week period in their I93FAST14 project. Employing simply supported, light weight steel girder bridge deck units, connected by a field cast link slab over the piers, allowed three-span bridges to be replaced during weekend closures.
Registration for this 4-hour webinar on November 4 is limited.
LRFD Simon Update
With NSBA's continued commitment to supporting the bridge design community, we are pleased to announce that we will be releasing an update to LRFD Simon later this year. This new version will include the following key enhancements:
7th Edition AASHTO Specification Support
Internally Calculated Distribution Factors
Deck Pour Analysis
Web Depth Optimization
New Design/Analysis Tutorial
Assortment of Fixes
All existing registered users will be notified when this final release is available for download. If you are not an existing user and wish to be notified, please visit the NSBA Steel Bridge Suite Registration and Request page and register.
Beta Test Participation
As Beta versions become available, we would appreciate your time helping us “kick the tires” and providing us with feedback as we move toward a final release. If you are interested in participating in the Beta evaluation of this new LRFD Simon version, please send an email request to firstname.lastname@example.org.
About LRFD Simon
LRFD Simon is NSBA’s complimentary software for preliminary steel plate and box girder design. Simon has a long history of serving as a key tool in helping bridge engineers efficiently design and analyze steel bridges. With its re-launch in 2012, Simon was updated to support the AASHTO LRFD Design Specification and was given a new user-friendly interface. Resources and tools like LRFD Simon are an integral part of assisting designers to more rapidly evaluate design alternatives and make more educated decisions that will hopefully result in more economical steel designs and an overall better end product for owners.
Surface Preparation of Weathering Steel
Recently the question was raised about the required level of surface preparation for weathering steel girders. State DOTs require painted steel to receive an SSPC-SP10 surface preparation. However, SSPC-SP10 surface preparation, among other things, is time consuming, expensive and overkill for most weathering steel girders, this according to fabricators with weathering steel experience.
So what is the proper level of surface preparation for weathering steel? In states that have issued requirements, they suggest an SSPC-SP6. This provides a starting point, but what if the project is in a state where requirements have yet to be determined?
First and foremost, speak with a fabricator with knowledge of weathering steel. If one is not known, contact an NSBA Regional Director (visit the NSBA website homepage www.steelbridges.org and scroll down to the bottom of the page).
Beyond that, follow this list of guidelines:
To achieve a class B faying surface, an SSPC-SP6 surface preparation is required.
Without surface preparation, weathering steel is unlikely to develop a uniform patina due to the presence of mill scale. While not structurally detrimental, it may be considered aesthetically displeasing.
Consider the economics of the project:
- A weathering steel bridge in a low-traffic volume area may not require the same aesthetic considerations as a high-volume bridge. Therefore, forgoing surface preparation would make the project more economically friendly.
- Consider surface preparation on the fascia girders only. The surface condition of interior girders are difficult for the motorist passing underneath to see.
For additional information, check out the AASHTO/NSBA collaboration design guide S2.1-2008 Steel Bridge Fabrication Guide Specifications.
Photo: Courtesy of Indiana Steel & Engineering Corp.
Alexander D. Wilson Named Recipient of 2014 SMDI/AASHTO Richard S. Fountain Award
The Steel Bridge Task Force of the Steel Market Development Institute (SMDI), a business unit of the American Iron and Steel Institute (AISI), and the AASHTO (American Association of State and Highway Transportation Officials) Technical Committee for Structural Steel Design have named Alexander D. Wilson, Manager of Customer Technical Services for ArcelorMittal USA, as the recipient of the 2014 Richard S. Fountain Award.
Named for the founder of the Steel Bridge Task Force, the Richard S. Fountain Award recognizes leadership in steel bridge research and outstanding efforts to advance AASHTO specifications. Wilson received the award at the meeting of the Steel Bridge Task Force, which was held on August 7, 2014 in Denver, Colo. The award was presented by Gregory R. Perfetti, Chairman of the AASHTO T-14 Steel Bridge Structures Committee and State Bridge Design Engineer, Structure Design Unit, North Carolina Department of Transportation; and Dennis Mertz, Ph.D., professor in the Civil and Environmental Engineering Department at the University of Delaware.
To read the full story click here.
Transportation Research Board Issues New Research Request for Proposals
The Transportation Research board has issued and RFP for NCHRP 14-35 Acceptance Criteria of Complete Joint Penetration Steel Bridge Welds Evaluated Using Enhanced Ultrasonic Methods. The objectives of this research are to: (1) develop guidelines to evaluate complete joint penetration welds in steel bridges based on updated acceptance criteria and (2) develop proposed modifications to BWC. The deadline for request for proposals is November 18, 2014 for project consideration.
Background on the Project
Inspection of welds in steel bridges is necessary to ensure the quality of workmanship during the fabrication and construction process and later on when the bridge is in service. There are two non-destructive evaluation (NDE) methods for evaluation of complete joint penetration (CJP) welds in steel bridges: radiographic (RT) and ultrasonic (UT). Recent advances in enhanced ultrasonic methods, including the development of phased-array ultrasonic technology (PAUT), allow for efficient detection and characterization of flaws with the option of automated data collection and imaging. Criteria for categorizing weld discontinuities as acceptable or unacceptable are codified in the AASHTO/AWS D1.5M/D1.5: Bridge Welding Code (BWC). However, these acceptance criteria do not reflect full use of the capability of enhanced ultrasonic testing methods, and furthermore are not based on the effect of weld discontinuities on bridge performance (e.g., resistance to fatigue and fracture). In addition, some weld discontinuities that are not allowed according to BWC are potentially not harmful and may not decrease service life. An updated acceptance criteria based on enhanced ultrasonic testing methods for evaluation of CJP welds in steel bridges is needed for fabricators and bridge owners.
For additional information on the project click here.