The 20th century represented a dramatic evolution in steel bridge technology. The first half of that century featured some of the most spectacular bridges of our time, as many of the major physical obstacles to transporting people and goods were spanned.
The second half of that century featured another dramatic evolution of our highway system as the population expanded and the automobile became a way of life. On June 29, 1956, President Dwight D. Eisenhower signed into law the Federal-Aid Highway Act, which gave birth to the country’s 41,000-mile interstate highway system. Thus began the building of a highway network and its many bridges, linking primary urban centers.
Through this period, the evolution in design codes, bridge types, materials and construction methods was amazing. This article chronicles some of the highlights in the history of steel bridges and concludes with a brief look forward.
Suspended in air
The first quarter of the 20th century saw suspension bridges dominate the very long spans. In the second quarter, the spans increased monumentally from the 1,850-ft range (Ambassador was a world record in 1929) to the 4,200-ft Golden Gate in 1939.
The suspension bridge era effectively ended with the 4,260-ft Verrazano-Narrows span in 1964, which was eight years after the interstate era began.
Truss thrust, arch ahead
During the early 20th century trusses began to shed some of the ornamentation associated with bridge construction in the previous century. Some of the classic trusses and arches of the century were opened to traffic: the Bayonne, the first Carquinez, Clifton (first arch over the Niagara Gorge), Columbia River at Longview and the Yaquina Bay bridges.
Two similar long-span cantilevered truss bridges opened in 1955 and 1956: the Tappan Zee, across the Hudson River in New York City, and the Richmond-San Rafael across San Francisco Bay.
Other important steel truss and arch bridges include:
- 1957: The Kingston-Rhinecliff Bridge opened across the Hudson River in New York City. It was the first bridge to use a series of continuous trusses totaling 5,200 ft in length.
- 1958: The Greater New Orleans Bridge, which spanned the Mississippi River, was completed. Its 1,575-ft cantilevered truss main span set a record at the time. These truss and arch bridges were nearly the last of the long spans to use hot-driven rivets as more affordable and versatile welding and high-strength bolting technologies forced their demise.
- 1959: The Bureau of Reclamation constructed a true deck arch over the Colorado River in Glen Canyon, Ariz. The arch ribs are steel trusses supported by concrete skewbacks embedded in the canyon walls. The arch spans 1,028 ft and the deck is 700 ft above the river.
Extending family
New bridge designs came on the scene during the 1960s and 1970s. Steel-tied arches surpassed trusses in popularity for two reasons:
1. They were more aesthetically appealing; and
2. Contractors were developing economical methods for erecting tied arches.
At the same time, steel box girder bridges were introduced as a viable alternative to conventional plate girders. Important research into the design and behavior of box girder bridges demonstrated the inherent economy and performance of a multibox torsional section for bridges on curved and tangent alignments.
The Coronado Bay Bridge in San Diego, which opened to traffic in 1969, is arguably one of the most important examples of a steel box girder bridge. The 2.12-mile bridge has a vertical clearance of about 200 ft. It features beautiful curves and impressive towers. The bridge’s braces and stiffeners are contained within a box girder, ensuring a smooth exterior.
Thanks to new and improved designs, materials and construction methods, many records were set during these two decades. They include:
- 1962: The Lewiston-Queenston deck arch opened. Positioned near the mouth of the Niagara River, the bridge links New York and Ontario, Canada. At 1,000 ft it was the world’s longest fixed or true arch;
- 1962: A plate girder bridge was built across the Mississippi River between Wisconsin and Minnesota. It features a main span of 450 ft, tying the record for the longest girder span;
- 1962: The California Division of Highways designed and constructed a true deck arch near Santa Barbara in Cold Springs Canyon. The 700-ft arch ribs are welded, rectangular box sections and the spandrel columns are square, welded tubes supporting the concrete deck;
- 1970: A pedestrian crossing in Wisconsin became the nation’s first cable-stayed bridge;
- 1973: The second Gov. William Preston Lane Jr. Bridge opened over the Chesapeake Bay near Annapolis, Md. The centerpiece is the 2,914-ft suspension bridge with a 1,600-ft main span, which was built with preassembled, parallel wire cable strands;
- 1972: Two through-tied arches, placed in tandem, are featured in a bridge across the Mississippi River at Memphis, Tenn. Each through-tied arch is 900 ft long;
- 1972: The first vehicular cable-stayed bridge in the U.S. was constructed in Sitka, Ala. It has a main span of 450 ft;
- 1973: The Fremont Bridge in Portland, Ore., set a U.S. record for tied-arch spans at 1,255 ft. This record span is likely to stand for all time since the more economical cable-stayed bridges are now the standard;
- 1974: The Delaware River’s Commodore Barry Bridge set a new length record for a cantilevered truss span. The main span is 1,644 ft. The total length of the bridge is 13,912 ft. This span also is likely to stand as an all-time record because cable-stayed bridges for this span length are far more economical; and
- 1977: The span-length world record for arch bridges was broken when the New River Gorge Bridge opened in West Virginia.
At 876 ft, it is the highest bridge above water in this country.
Cable stayed, cable tradition
Cable-stayed bridges dominated the late 20th century. This design used concrete for shorter spans and composite steel and concrete for longer spans. Bridge highlights from these two decades include:
- 1983: The Hale Boggs Bridge in Luling, La., boasts a 1,222-ft-long main span;
- 1987: The Weirton-Steubenville Bridge over the Ohio River was constructed with a main span of 820 ft. It features a concrete deck acting compositely with steel-edge girders; and
- 1992: The I-526 Cooper River Truss Bridge at Charleston, S.C., was a departure from traditional truss design. The truss structure is a 1,600-ft, continuous three-span, parallel-chord warren truss with no vertical members or sway bracing. Unlike previous truss designs, this bridge provides clean lines and an open view to users.
In the 1990s, high-performance steel was introduced as a joint effort between the Federal Highway Administration and the U.S. steel industry.
This new steel offered many grades (strength levels) with very good ductility and enhanced corrosion resistance.
Although there are various serviceability issues to be resolved, high-performance steel appears to be the steel of choice for the 21st century. The economy and performance of girder bridges using high-performance steel continues to evolve with longer spans and fewer joints and bearings, as well as enhanced durability with the advent of more advanced deck systems.
In 2003 the Third Carquinez Bridge opened, replacing the original bridge built in 1927. The bridge features a closed-cell, orthotropic steel deck, air-spun cables and concrete towers.
This is just the second suspension bridge constructed in the U.S. since the Verrazano-Narrows Bridge connected Brooklyn and Staten Island in 1964.
Spanning ahead
Our infrastructure has evolved into something larger than what many envisioned in 1956. It has become part of our urban environment, a national asset and a vital basis for local and national economies.
The next 50 years will no doubt expand our capabilities even further. Advanced materials, innovative concepts and longer spans are just some of the advances we can expect.
Innovations: form and materials
Innovative bridges are about structural form. Innovative forms take advantage of advanced materials. Bridge engineers continue to combine materials to create more efficient and economical forms. For example, high-strength steel strand turns concrete into a “new material,” providing better stiffness, strength and serviceability.
Longer spans
Senior practitioners in the long-span business think suspension spans and cable-stayed spans can increase significantly before reaching their limitations.
Rapid construction
Nothing could be more productive than a simple, mass-produced bridge component that can be readily fabricated in a controlled environment and rapidly assembled onsite or at difficult sites with limited access.
Integrated delivery
Bridge owners and designers should “manage” risk by “minimizing” it with the right design and construction solutions, rather than spreading the damage around (as underwriters do). This demands an integrated delivery program that includes:
- Design development by the owner and the engineer;
- Final design and a comprehensive, independent peer review by qualified designers; and
- Construction engineering by pre-qualified contractors.
Economics and risk
When a contractor can control and manage his own risk, the result can be significant savings to the owner. This is one benefit of design-build. Integrated delivery systems mean we can minimize risk and deliver bridges cheaper, faster and better.
Value
In the next 50 years, as bridge designs continue to evolve, so should our definition of value. It should represent more than the lowest initial cost. Value should stand for longer life expectancy, enhanced constructability and aesthetics and reduced maintenance.
Price is a vice president at HNTB Corp., Chicago. He leads HNTB’s bridge engineering practice in the Great Lakes region.
