Segmental Concrete Bridges a Major 21St Century Alternative by Clifford L

construction issues Segmental Concrete Bridges A Major 21st Century Alternative By Clifford L. Freyermuth

Segmental concrete bridge construction range up to nearly 300 feet in height, and the to accommodate spans ranging from 95 feet began with the use of cast-in-place cantilever bridge deck is 880 feet above the Colorado to 205 feet, and horizontal curve radii as short technology for the Lahn Bridge at Balduin- River. The Hoover Dam Bypass Bridge is as 212 feet. Roadway widths varied from 22 stein in Germany in 1950-1951. Glued match scheduled for completion in June 2008. feet to 96 feet. For this project, the segmental — cast joints for precast segmental construc- These bridges clearly refl ect the use of low bid was $79.3 million, saving the Massa- tion were fi rst used for the Choisy Le Roy segmental concrete bridge technology for chusetts Turnpike Authority in excess of $27 Bridge in France in 1962. structures that would have been built with million over the lowest steel alternate bid. In the U.S., precast segmental construction structural steel in the U.S. 30 years ago. Seven Segmental concrete bridges have also com- was fi rst used for the John F. Kennedy factors have contributed to growth in the use peted successfully on smaller projects against Memorial Causeway in Corpus Christi, Texas of segmental technology for major bridge alternates with prestressed concrete© beams or in 1972. In 1974, the Pine Valley BridgeCopyright projects in the U.S. and around the world: bulb tees. In 1997, the approximately $20 cast-in-place balanced cantilever bridge was 1. Competitive initial cost. million bid for the segmental alternate for constructed in California. 2. Low maintenance costs. the Sailboat Bridge in Oklahoma was $1.1 From these beginnings, both precast and 3. Speed of construction. million lower than the lowest bid for a bulb cast-in-place segmental concrete bridge con- 4. Safety under extreme events. tee superstructure. The Sailboat Bridge fea- struction have grown to become a major 5. Industrialization of the con- tured twin precast concrete segmental bridg- component of the bridge construction in- struction process. es with spans of about 122 feet and a total dustry in nearly all parts of the world. Two 6. Innovations in construction equipment. length of 3,044 feet. The roadway width of current projects which refl ect this growth in 7. Aesthetic appeal. each bridge is 41 feet 3 inches. The bridges the U.S. are the San Francisco-Oakland East feature an as-cast riding surface with epoxy Bay Skyway Bridge (Skyway Bridge) (Figures joints between segments. 1 and 2), and the Hoover Dam Bypass Bridge (Figure 3). At $1.047 billion, the contract Low Maintenance Costs for the Skyway Bridge was the fi rst Caltrans Possibly one of the best measures of dur- project that cost in excess of 1 billion dollars. ability and related maintenance cost is the The contract includes the construction of National Bridge Inventory data, which is twin 85.3 feet wide precast segmental bridges based on bridge inspection reports by per- across Oakland Bay for a total length of sonnel from State Departments of Trans- 13,776 feet. Typical span lengths are 525 feet, portation compiled by the Federal Highway and segmentSTRUCTURE weight ranges from 500 to 800 Administration (FHWA). A 1997 article tons. The use of these very heavy segments by FHWA engineers indicated that about was possible due to water transportation from 110,000 of the 470,000 bridges on the the casting yard in Stockton, California. Figure 2: Segment Erection, San Francisco-Oakland magazineFederal Highway System were structurally Bids were received on the Hoover Dam East Bay Skyway Bridge Construction. Photo courtesy defi cient. While steel bridges represent about Bypass Bridge on September 16th, 2004 with of Kiewit/Flatiron/Manson, A Joint Venture. 40 percent of the overall bridge total, they a low bid of $114,000,000.00. At 1,090 feet, Competitive Initial Cost include about 60 percent of the structural- the segmental concrete arch span will be the The record of the past thirty years clearly ly defi cient bridges. The number of bridges fourth largest concrete arch in the world when indicates that segmental concrete bridges have with structural defi ciencies associated with completed. The precast segmental columns often been selected as a result of competitive various materials and various bridge ele- bids against alternatives using other materials ments is shown in Figure 5. (The S/A term and methods. This is not to imply that segmental concrete bridges are always the most economical alternative. However, the suc- cess rate of segmental bridges in competitive bids has been suffi cient to establish the basic economy of segmental construction. In this context, many segmental bridges were selected through alternative bids for the Boston Cen- tral Artery Project, although major bridges in the northeast U.S. have traditionally utilized steel as a construction material. One example is the I-93 Viaducts and Ramps shown in Figure 1: San Francisco-Oakland East Bay Skyway Figure 4. This project includes 520,000 square Bridge Construction. Photo courtesy of Kiewit/ Figure 3: Hoover Dam Bypass Bridge. Drawing Flatiron/Manson, A Joint Venture. feet of bridge deck. The erection methods had courtesy of T.Y. Lin International. STRUCTURE magazine • October 2005 25 rapid construction speed with respect to possible alternatives for the same site constraints. The Victory Bridge over the Raritan River in New Jersey provides a current example of speed of construction for precast segmental bridges (Figure 6). The Victory Bridge incor- porates twin southbound and northbound bridges, each 3,971 feet in total length. The southbound bridge was opened to traffi c just 15 months after the Contractor received Figure 4: Boston Central Artery/Tunnel, I-93 notice to proceed. After demolition of the ex- Viaducts and Ramps. Photo courtesy of Figg isting bridge with a swing span that opened an Engineering Group. average of 1,100 times a year, the northbound bridge was erected in just nine months. The in Figure 5 refers to structural adequacy.) new bridge features a United States record for Defi cient bridges in the S/A category have a the 440 foot fully match cast precast concrete very low load rating. Only 3 percent of the segmental main span. The bridge also incor- 110,000 structurally defi cient bridges (about porates precast piers as tall as 100 feet that 3,300 bridges) utilized prestressed concrete, were erected in a single day, and the use of an © and there are no known structurally defi cientCopyright integral concrete wearing surface cast with the segmental bridges. Although most segmental segments. Main span pier segments are 21 feet bridges are less than 30 years old, the National deep and weigh 128 tons. By casting them in Bridge Inventory data indicates that bridges halves, the same erection equipment could be built by other materials and methods do ex- used for both pier and typical segments. Erec- Figure 6: Victory Bridge, New Jersey. hibit structural defi ciency at earlier ages. tion of two 3971 foot long bridges over water Photo courtesy of Figg Engineering Group. Due to longitudinal and transverse pre- with pier heights ranging to 100 feet, and a stressing, segmental concrete bridge decks are main span of 440 feet, in a total of 24 months virtually crack-free, which provides greatly of external and internal tendons, is used. refl ects the construction speed possibilities of enhanced durability in aggressive environ- However, this research does indicate that use ments. Additional corrosion protection in precast segmental bridges. of all external tendons provides somewhat areas where deicer chemicals are used can be more ductility than results with use of internal economically provided by an additional inch Safety under Extreme Events tendons. Further, since external tendons or inch and a half of concrete cover over top Research at the University of California, San remain elastic (stressed below the yield point) slab reinforcement placed at the time the seg- Diego, undertaken in reference to design of in an earthquake, there would be very little ments are cast. The use of integral overlays the San Francisco-Oakland East Bay Bridge residual defl ection following a seismic event, also eliminates the delamination problems (Figure 10) has confi rmed that the strength and and the damage to the superstructure that have sometimes occurred with bonded ductility of segmental superstructures, and would be signifi cantly less than would result concreteSTRUCTURE overlays. monolithic superstructure-pier connections, when internal tendons were used. In the greatly exceeds the demand of the design superstructure-pier seismic test depicted in Speed of Construction earthquake. This result applies regardless of Figure 7, cracking was confi ned to the pier, Construction speed varies for different types whether external (within the cell of the box and the superstructure remained uncracked. of segmental bridges,magazine but in most cases all girder) or internal (within the concrete cross This result refl ects the strong beam, weak types of segmental construction offer relatively section) post-tensioning tendons, or a mixture column seismic design philosophy.

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Figure 5: FHWA Data on Structurally Deﬁ cient Bridges on the Figure 7: Segmental Superstructure-Pier Seismic Test at the Federal Highway System - 1997 University of California, San Diego, 2004

26 STRUCTURE magazine • October 2005 tural damage. Winds and storm surges asso- Industrialization of the ciated with Hurricane Ivan did infl ict signifi - Construction Process cant damage on bridges utilizing other types of construction. The Interstate 10 bridge in The inherent economy of segmental concrete Pensacola is now being replaced. bridges is, to a signifi cant degree, the result of the industrialization of the construction process. One precast segment is normally produced each day from short-line casting forms. While there are minor variations in segments, the procedure remains basically the same from day to day. After a short learning

Figure 8: Mobile Segment Erection Device, Dallas High Five Interchange, 2002-2004. Photo courtesy of Parsons. The exceptionally severe 2004 hurricane season demonstrated the ability of segmental © concrete bridges to withstand extreme windCopyright loads. Hurricane Ivan came ashore on the Figure 9: Articulated Erection Gantry for use on Gulf coast near Mobile, Alabama and Pen- Curved Alignment. Skytrain Millenium Line, sacola, Florida with winds up to 130 miles per Vancouver, British Columbia. hour and storm surges as high as 30 feet. Five At the time of producing this article for major segmental and concrete cable-stayed publication, the available information bridges stood strong with no structural dam- indicates that four major segmental and age despite a direct hit from Hurricane Ivan. cable-stayed bridges performed very well and Other segmental and cable-stayed Florida Figure 10: San Francisco-Oakland East Bay Skyway were, for practical purposes, undamaged bridges also withstood winds associated with Bridge Segment Erection Device. Photo courtesy of []by Hurricane Katrina. Kiewit/Flatiron/Manson, A Joint Venture. hurricanes or tropical storms without struc-

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STRUCTURE magazine • October 2005 27 forming, transporting and erecting segments. The availability of this specialized equipment increases the speed of construction and provides additional economies in construction. However, more sophisticated equipment is expensive and may only be feasible for large projects. An inventory of used equipment is available from suppliers which may be more appropriate for more moderate sized projects. Aesthetic Appeal Figure 11: Broadway Bridge in Daytona Beach, Florida. Photo courtesy of Figg Engineering Group. Segmental concrete bridges have been widely recognized, and have received many awards, for curve, construction crews become highly ef- their inherent aesthetic appeal. The Broadway ﬁ cient in producing segments. The major con- Innovations in Bridge in Daytona Beach, Florida shown in struction effort is transferred from the bridge Construction Equipment Figures 11 & 12 is an example of the aesthetic site to the “factory” environment of the casting Growth in the construction of segmental potential of segmental concrete bridges. yard. For cast-in-place segmental bridges, the bridges has led to innovations and reﬁ ne- Conclusion construction process is similar but it takes ment of construction equipment. A mobile © place at the bridge site. Copyrightrubber-tired segment erection device de- Over the past thirty years, segmental con- While the time required for construction veloped for construction of the Dallas High crete bridges have become a primary alterna- of a typical segment (usually about 5 days) Five Interchange in 2002-2004 is shown in tive for the construction of major bridges in is much longer than precast segmental con- Figure 8. An articulated overhead gantry for the U.S. The applicable span range for vari- struction, this should be considered in the use on curved alignment is shown in Figure ous types of segmental bridges extends from context of the longer span lengths for which 9. Self launching erection devices were de- 100 feet to at least 1,500 feet for segmental cast-in-place balanced cantilever construc- veloped for lifting the 750 ton segments of cable-stayed bridges. The factors discussed tion is used (usually for spans of 350 feet or the San Francisco-Oakland East Bay Skyway above that have led to the dramatic growth more). At the beginning of superstructure Bridge (Figure 10). experienced in use of segmental bridges are construction, there is a learning curve for the Growth in the use of segmental bridges considered to provide the basis for continued construction crew which results in a much in the U.S., and worldwide, has accelerated growth in construction of segmental concrete slower pace of construction. development of specialized equipment for bridges in the 21st century.▪ STRUCTURE magazine www.structuremag.org For Advertiser Information, visit Information, Advertiser For

Figure 12: Broadway Bridge in Daytona Beach, Florida. Photo courtesy of Figg Engineering Group.

Clifford L. Freyermuth is Manager of the American Segmental Bridge Institute. He may be contacted by email at [email protected].

28 STRUCTURE magazine • October 2005