This month’s newsletter includes information about:
- This Month's MSC Article - Are You Sure That's Fracture Critical?
- Restoration of a National Historic Landmark: the Eads Bridge over the Mississippi River at St. Louis.
- States approve over $18 Billion in Spending in 2014.
- New I-25 Paseo Overpass will Glow
- Infographic Examines Bridge Technology throughout History.
- Mark your Calendar for these Upcoming Events.
This Month's MSC Article - Are You Sure That's Fracture Critical?
ONE OF THE MOST NOTEWORTHY bridge failures in the United States occurred in 1967, when the Point Pleasant Bridge over the Ohio River (also known as the Silver Bridge) collapsed, resulting in 46 deaths.
The collapse was due to brittle fracture of one of the eyebars that formed the suspension system of the bridge. The subsequent failure investigation revealed that the fracture was due to brittle propagation of a tiny crack in the eyebar. Because the fracture toughness of the eyebar was extremely low, a relatively small crack led to a brittle fracture of the eyebar, which in turn led to the collapse of the bridge.
This collapse was the catalyst for many changes in material specifications, design, fabrication and shop inspection of steel bridges. These requirements are codified in the AASHTO Bridge Design Specifications and the AASHTO/AWS D1.5 Bridge Welding Code (AWS) and are applied to tension members whose fracture could lead to bridge collapse. (Another bridge incident—the failure of a pin-and-hanger assembly, which triggered the collapse of one span of the Mianus River Bridge in 1983—served as the impetus for enhanced field inspection requirements for these same members.)
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This article originally appeared in the January issue of Modern Steel Construction.
Restoration of a National Historic Landmark: the Eads Bridge over the Mississippi River at St. Louis.
The Eads Bridge is a unique bridge utilizing materials and designs to meet the requirements of the time to not impede riverboat traffic. A combined road and railway bridge, the design was an evolution based on a river of competing interests including Chicago versus St. Louis; truss versus arch; steel versus cast iron and wrought iron (though all three were used in construction); local bridge companies and other considerations. It was designed and built by Captain James B. Eads. Construction began in 1867 and the bridge opened in 1874. Four sets of ribbed steel arch spans were supported by two shore abutments and two mid-river piers; this was an innovative design for the time. It is also the first true use of structural alloy steel in a major bridge project. At its opening in June, 1874, it was the longest arch bridge in the world at 6,442 feet (1,964 meters).
Despite multiple maintenance painting projects during its 140 year life span, all steel coating systems inevitably reach the end of their protective service life. Since the bridge’s initial construction, coatings for steel and their associated application techniques have made quantum leaps in durability and sustainability. Much of the existing paint contained lead and thus, containment of residues from its removal was critical to avoid contamination of the Mississippi River. Corrosion observed included general rusting, pitting, pack rust, lamellar rust and loss of cross section of many key structural elements. Recognizing the importance of preserving this still functioning national landmark led to the first full repaint of the bridge since its construction.
A joint venture was formed to tackle this important project. A local bridge construction firm was responsible for the assessment of the condition of the steel, wrought iron and cast iron as well as the identification of the elements that required replacement. All of the track stiffeners were replaced by those fabricated by Missouri Fabricators (an AISC Member and AISC Certified fabricator). Thomas Industrial Coatings and later ERAValdivia Contractors were responsible for containment, soluble salt remediation, removal of existing paint via abrasive blasting and high pressure water blasting, proper disposal of residues, application of a zinc-rich primer and one or two topcoats. The project required extensive rigging custom designed for the arched configuration of four spans and to accommodate river traffic and variable heights off the water due to fluctuations in river level. Spent abrasives were collected on working barges that had to be coordinated with river levels and commercial traffic. The MetroLink light rail system as well as the roadway remained active throughout the project though reduced to traffic on the north or south sides of the bridge.
Carboline Company has been involved with the analysis including metallurgical analysis of the steel, wrought iron and cast iron components of the structure for the selection of the corrosion resistant coatings for 12 years prior to the commencement of painting in 2013. The specification of the coating system to provide long-term corrosion protection and optimal aesthetics (resistance to fading and chalking) was initially based on the state department of transportation for bridges. Ultimately, however, the specification was written to emulate the detailed evaluation and choice of a zinc rich primer, optional intermediate coat and hybrid polysiloxane finish similar to that chosen by the Wisconsin Department of Transportation for the Marquette Interchange in downtown.
The structural integrity of the Eads Bridge after 140 years of little maintenance speaks well for the design of Captain Eads that evolved during the construction using that relative unknown: steel. Replacement of steel components as needed and the application of a high performance coating system will do justice to that legacy.
Roger Tegtmeyer is the Global Business Development Manager for Carboline in Belleville, Ill. He can be contacted at RTegtmeyer@carboline.com.
The historic Eads Bridge across the Mississippi in St. Louis prior to re-coating. Photo credit: Carboline
States approve over $18 Billion in Spending in 2014.
States approved over $18 billion in transportation funding plans and signed into law more than 20 bills to support transportation infrastructure throughout 2014, according to a recent report from ARTBA’s Transportation Investment Advocacy Center. Of those measures, 11 states passed transportation funding bills, with both Rhode Island and New Hampshire approving state gas tax increases. Statewide ballot measures to increase funding were approved by voters in three states—Texas, Rhode Island, and Ohio—while ballot measures to create transportation fund “lockboxes” successfully passed in two states—Maryland and Wisconsin. Looking forward to 2015, there are over 20 transportation funding bills awaiting action from state lawmakers.
Read the report.
This article originally appeared on the ARTBA website.
New I-25 Paseo Overpass will Glow.
If there’s one thing drivers can be thankful for this holiday weekend, it’s that the Paseo del Norte interchange rebuild is just about a month from completion. And if there’s one thing Black Friday shoppers can appreciate, it’s how nice it’s been wrapped up for the public.
That’s because a lot more goes into a modern road project than industrial gray concrete.
William Hutchinson is the landscape architect for the New Mexico Department of Transportation. He says the department works to ensure projects have a “sense of place” and “relate to that place.”
“They may not make sense somewhere else, but they make sense right there,” he says.
And so the $93 million Paseo rebuild is cast in colors that mimic the sun hitting the Sandia Mountains and motifs that celebrate the Albuquerque International Balloon Fiesta an exit to the north.
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The balloon motif on the northbound I-25 to westbound Paseo del Norte flyover seen against the Sandia Mountains on Tuesday. (Dean Hanson/Albuquerque Journal)
Infographic Examines Bridge Technologies throughout History
Ohio University’s Russ College of Engineering and Technology has created an infographic on bridge construction techniques and technologies throughout history, comparing historic bridge designs with contemporary ones - from clapper bridges made of stone slab to modern-day steel suspension bridges - and examining the people and cultures they connect.
Check out the infographic at http://engineering.online.ohio.edu/civil/bridges-infographic/.