Leading Infrastructure Innovation

Bridge design and construction innovations are imperative as America aims to retain a quality infrastructure amid massive funding challenges. Industry leaders are answering this call by designing and constructing bridges that are more economical and durable, and longer lasting.

Aging Gracefully

One of the key innovations in the past few decades was the introduction of weathering steel. High-strength, low-carbon steel alloys form a thin, protective orange or brown patina when exposed to the atmosphere. Weathering steel is generally four to eight times more corrosion-resistant than traditional low-carbon steels. In locations where weathering steel is not a preferred option, such as in very wet environments, new paint innovations are helping to reduce long-term maintenance expenses. According to Conn Abnee, executive director of the National Steel Bridge Alliance, the new and improved paint systems have a 30 to 50-year life when three or four coats are applied.

HPS Gaining Ground

Another way that America’s transportation leaders are heeding this call for innovation is through the expanding use of high-performance steel (HPS). “Although HPS was originally conceived just a decade ago, it is achieving relative notoriety as the material-of-choice in bridge applications nationwide,” says Dan Snyder, manager of business development for the American Iron & Steel Institute’s transportation and infrastructure division.

Recent successes in HPS application have been documented by the state of New York. The New York State Thruway Authority (NYSTA) participated in a cooperative agreement with the Federal Highway Administration (FHWA) to evaluate and document the use of HPS70W on seven bridge structures. For each of these bridges, weld-procedure qualification tests and diffusible hydrogen tests were conducted prior to fabrication. Satisfied with the weld quality, NYSTA determined that the 40% higher yield strength of HPS70W over Grade 50W allowed engineers to design longer, shallower spans and added greater value when replacing simply-supported, multi-span structures with continuous-span structures. With little or no modification to the bridge approaches, vertical clearance could be increased and piers could be eliminated without adding to the depth of the girders.

According to AASHTO’s Guide for Highway Bridge Fabrication with HPS70W Steel, a significant advantage is the product’s enhanced weathering characteristics when compared against conventional 50W and 70W steels. Another attribute is enhanced toughness, allowing structures to effectively absorb and redistribute the impact of fatigue loads. A third feature is the steel’s weldability. The weld quality is improved because the carbon level in the new-generation steel is lower than in traditional steel and preheating requirements are significantly reduced. “HPS allows engineers to use thinner and smaller girders with greater strength,” states Abnee. “This allows for longer spans that are lighter to install and offer the same value as standard steel bridges.”

The Orthotropic Alternative

Another source of innovation is the increasing interest in orthotropic bridge sections as a bridge deck alternative. The term orthotropic refers to a design where a bridge deck is formed from a solid steel plate. This plate is then used typically as a top flange for the main girder, the transverse floor beam and the deck ribs. Abnee says that the design makes the structure easier to install, as evidenced by its widespread use in Asia. Yet he contends that the concept is not a mainstay in the U.S. today, primarily because the design is so precise that fabrication facilities in America are not equipped to accommodate the stringent tolerances. However, the concept is catching on and U.S. bridge fabricators are modifying their facilities to meet the need. For more information about the orthotropic alternative, visit www.orthotropic-bridge.org.

The Test of Time

As we face funding troubles and infrastructure decline, Abnee reminds us to keep one eye clearly focused on America’s rich history of quality bridge design. “We have over 100 bridges in this nation that are over 100 years old,” he says. And that is a tribute to the generations past that designed and constructed marvelous structures without the benefit of our modern tools and technologies. “With nothing more than a slide rule, knowledge and individual ingenuity, they made monuments,” adds Snyder.

The Texas Dept. of Transportation (TxDOT) recently investigated use of fiber-reinforced polymer (FRP) composite materials for highway structures. One concern was the relatively low modulus of FRP materials. Testing focused on development of a system combining FRP beams with a conventionally reinforced concrete deck. Molded Fiber Glass (MFG) teamed with TxDOT to develop this first-of-its-kind beam. Their effort resulted in production of 26 beams for the San Patricio County bridge. Testing was completed at the MFG Research Lab and the beams were produced at MFG’s Adelanto, CA, facility.

Viewpoints on Bridge Design & Construction

American Road & Transportation Builders Assn

David Bauer
Senior Vice President, Government Relations

America’s bridge network is deteriorating and needs urgent repair! According to the Federal Highway Administration, more than 160,000 U.S. bridges—nearly 30%—are classified as either structurally deficient or functionally obsolete.

These disturbing statistics further demonstrate the need for Congress to complete action on the reauthorization of the Transportation Equity Act for the 21st Century (TEA-21). This legislation presents the American people and congressional leaders with a simple choice—accept the status quo or begin taking steps to improve the nation’s highways and bridges. The House-passed reauthorization bill would provide a 6% increase in federal bridge investment between now and FY 2009. By comparison, the Senate-approved bill would provide a 51% increase—or nearly $33 billion—in new bridge funding over the same period.

As members of Congress continue to negotiate a final reauthorization measure, ARTBA believes the future of the nation’s bridges is one of the many reasons why retaining the Senate’s proposed highway, bridge and transit investment levels is clearly the right decision.
www.artba.org

DMJM+HARRIS

Ken Butler
Vice President, Bridge Principal

Some of the challenges the bridge industry faces are the design-build method of construction, ever-changing design codes, one-stop-shopping computer programs, increasingly tight budgets and a shortage of bridge engineers—not to mention an aging infrastructure, tremendous traffic congestion on our road systems, and uncertainty about the passage of a new transportation bill.

The design-build method of construction has provided a procurement method that can be advantageous to the owner, contractor and engineer. It is in the best interest of our industry to establish clear, fair and ethical standards so that there is proper balance between all parties.
Computer programs are becoming more and more sophisticated. Eventually, a design engineer will only need one program to perform all of the superstructure, substructure and foundation designs. We need to ensure, however, that our engineers are still trained in—and practice—classical methods of structural analysis. www.dmjmharris.com

CH2M HILL

Joseph Showers, P.E.
Chief Bridge Engineer

This is an exciting and challenging time for bridge engineers. As highway systems serve increasing volumes of traffic, and with the graying of our nation’s bridge inventory, a high percentage of bridges have become functionally or structurally obsolete.

Rehabilitating or replacing them often requires project teams to navigate a series of complex site, schedule and project constraints as well as addressing regulatory requirements and dealing with funding constraints.

In response, engineers have met these challenges through innovative approaches and technology applications, including alternative project delivery and the use of higher-performance construction materials to reduce maintenance costs. On our recent designs of long-span concrete bridges and urban freeway system interchanges, we have experienced the pride and satisfaction that comes with achieving truly community-sensitive solutions. Our design-build projects also continue to demonstrate the creative potential of genuinely collaborative relationships between designers and constructors that produce innovations in design, materials and methods, while saving clients time and money. www.ch2m.com

The Engineers’ Society of Western Pennsylvania

Thomas Leech, P.E., S.E.
Vice President, Gannett Fleming, Inc.
2004 IBC Chair

We live in an exciting time for bridge design and construction. Innovative uses of materials, well educated professionals, breakthroughs in computer-aided technologies, and skilled artisans in the construction industry have produced interesting and unique bridge structures throughout this country and the world. Conferences such as the annual International Bridge Conference in Pittsburgh, PA, highlight the achievements of the doers—the planners, designers and constructors of bridges. In this coming year, the Engineer’s Society of Western Pennsylvania celebrates its 125th anniversary, making this sponsoring society of IBC one of the oldest technical societies in our country.

Amid the excitement, there are many challenges which our industry faces. I offer the following challenges to all bridge planners and designers: Preserve our historic bridge treasures. Support innovative uses of materials and new technologies. Continually search for new and improved construction methods. And, design new structures with not only an eye to efficiency and economy, but also with an eye to context and proportion. www.eswp.com

International Bridge, Tunnel & Turnpike

Patrick Jones
Executive Director

Two of the biggest challenges facing public officials in America today are deteriorating roads and bridges and a lack of funding to pay for needed improvements. Based on recent studies by AASHTO and the U.S. Federal Highway Administration, we know we need to invest nearly $100 billion more per year in bridges and highways just to keep this infrastructure in its current condition. People across the nation are looking for answers.

The congestion, the public unrest, the lack of funding and the stark political reality have created a perfect storm for action on our nation’s bridge and highway infrastructure. Recent polls demonstrate that motorists prefer direct user fees, such as tolls and road pricing, instead of general taxation to fund bridge and highway improvements.

Toll roads can be built faster, more efficiently and are typically better maintained than taxpayer funded roads. Tolling is a real solution to American’s bridge and highway infrastructure crisis.
www.ibtta.org

Michael Baker Corporation

Jeff Campbell, P.E.
Director of Bridge Services

In today’s environment it is essential for bridge designers to forge closer relationships with all project stakeholders—from owners to environmental groups to the public at every level.

It’s a different world today than in decades past. Engineers must wear many hats. In particular, we need to be proactive leaders who sustain working partnerships with all stakeholder groups in a responsible manner. Whether a bridge is urban or rural, stakeholders abound, particularly in relation to environmental and aesthetics issues.

An important part of our job as engineering professionals is to educate stakeholders so they fundamentally understand why a design makes sense from functional, financial and aesthetic points of view. Public involvement makes a world of difference in the ultimate success of a bridge project. We must be in tune to changing times so we can build and maintain public trust and work in partnership with owners and users to tackle the important job of restoring and enhancing the country’s infrastructure. www.mbakercorp.com

Photo courtesy of © Bill Luken, Contractors Materials Co., Cincinnati, OH

The Concrete Reinforcing Steel Institute (CRSI) has modified its long-standing position on using welding as a means for assembling reinforcement for site-cast construction.

Traditionally, CRSI has strongly recommended that reinforcing bars be assembled with tie wire. At the same time, citing several sections of the ACI 318 building code, it has discouraged welding of crossing bars as a means for assembling reinforcement for site-cast, reinforced concrete construction becuase such welding of crossing bars could seriously affect the strength and ductility of the reinforcing bar.

In recent years, however, high-technology welding machines have become available. Welding machine technology from Europe now has impacted shop fabrication practices in the U.S. Several California fabricator/placer firms, as well as a few fabricators in other parts of the country, currently are using state-of-the-art welding machines to produce fusion-welded assemblies of reinforcing bars. Employing electric resistance, a fusion weld results from the fusion process that uses a combination of pressure and heat generated by electric impulses.

There are several advantages to using fusion shop-welded assemblies of reinforcing bars. First, it eliminates the time-consuming field placing and handling of small reinforcement elements such as stirrups and ties. Second, it results in very accurate positioning of stirrups or ties in the cage. Third, it provides for better overall dimensional control of the beam and column cages. Moreover, a large number of tensile and bend tests by independent labs have confirmed that controlled welding does not adversely affect the mechanical properties of the bars.

As a result of these findings and recognizing their benefits, CRSI has endorsed the use of fusion welding in the fabrication shop, while still recommending that field tack welding should not be permitted unless authorized by the architect/engineer. The institute also urges the use of shop-welded assemblies be permitted in higher-risk earthquake areas. Its Engineering Data Report, Number 53, Assembling Reinforcing Bars by Fusion Welding in the Fabricating Shop, reviews current code requirements, and new practices in welding reinforcing steel. It should be of interest to architects, engineers, contractors and others involved in the design and construction of cast-in-place steel reinforced concrete structures.

Design Data has over 20 years of experience in producing SDS/2 steel detailing software. Throughout its history Design Data has been an innovator in the steel industry, bringing new concepts to market. SDS/2 was the first product to automatically design connections inside the 3D model.

The new Version 7.0 exemplifies how innovation keeps customers on the leading edge of technology. SDS/2 provides the power of automatic connection design and erectibility checks along with the flexibility of creating unique parametrics and adaptive detailing.

The SDS/2 model can benefit all the steel parties. From the engineer’s office to the shop floor through erection, SDS/2 is providing a central model to collaborate and schedule time-critical projects.

The Alfred Zampa Memorial Bridge is a major suspension bridge that carries Interstate 80 between Crockett and Vallejo, CA. The structure includes 316 wire rope assemblies that suspend 24 orthotropic steel box girders The bridge required 18 main cable tie-down assemblies to deflect the twin, 20-in.-dia main cables. Wire Rope Corporation of America Inc. supplied the main cable suspenders and the main cable tie-down assemblies for this project.

A stretch of Texas’ State Highway 45 is expanding near Austin to serve commuters along a 10-mile corridor just north of the state capital. The roadway will grow from two to six lanes over a three-year construction period. Work began in 2002 and completion is slated for 2005.

To speed construction, the project was broken into segments. Archer Western Contractors and the joint venture of Zachry/Gilbert are each responsible for constructing a portion of the project.

The effort includes a series of highway bridges which were designed to retain a consistent aesthetic presence using an elastomeric liner that mimics the look of ashlar stone for all columns, walls and abutments. Symons Corporation provided the formwork for these bridges, but added an efficiency twist to the mix. “Generally, contractors buy their formwork and liner separately,” says Bill Moser, district sales manager in Dallas, TX, for Symons. “In this case, we attached the liner to the formwork at the factory, then shipped it in modular pieces that are bolted together on site.” This saved time and money and will help keep the fast-track project on course.

Demolition activities are under way on a 77-year-old concrete/structural steel bridge that crosses the Rockaway River and New Jersey Transit’s Morristown Line in Randolph and Rockaway Townships, NJ. The bridge will be replaced with a new, 12,600-sq-ft, five-span structure, consisting of precast/prestressed, reinforced, post-tensioned concrete box beams with a reinforced concrete deck. The four piers and two abutments will be cast-in-place reinforced concrete as well.

The New Jersey Department of Transportation awarded the $6.2-million construction contract to Northeast Remsco Construction of Toms River, NJ, in June, 2004 and anticipates completion by October, 2005.

One significant project challenge entails relocating overhead power lines through underground conduit to facilitate the removal and replacement of the structure. “We installed the casing pipe for the underground conduit by a combination of auger boring from one direction and pipe ramming from the other,” states Joseph Bonner, P.E., Northeast Remsco’s project engineer/manager. Once the overhead wires are installed through the new casing pipe, existing catenary wires that run the train will be removed from the existing structure and hung on newly-installed catenary structures.

The Chicago Dept. of Transportation (CDOT) is completing a $250-million, four-year renovation and reconstruction of the Chicago Skyway, a 7.8-mile elevated expressway. The project involves reconstruction of all overpasses and viaducts, modifications to toll plazas, reconstruction of the southern roadway, a new bridge deck, new lighting and replacement of deteriorated structural steel.

CDOT devised hydraulics-based steel replacement procedures to allow continuous live traffic loads on the bridge during reconstruction. Figure 1 shows a bottom chord replacement in progress. Here, a saddle is secured to each end of the chord section to be replaced. The chord tension is then transferred to eight Williams rods by means of eight Enerpac 150-ton, double-acting hollow plunger cylinders. The cylinders are supplied by an air-operated 10,000 psi pump, with needle valves used for load control.

Replacement of several dozen 40-ft box member chords involves splitting each along the top and bottom, replacing one half at a time, then installing cover plates on the top and bottom.