This category covers general contractors primarily engaged in the construction of bridges; viaducts; elevated highways; and highway, pedestrian, and railway tunnels. General contractors engaged in subway construction are classified in SIC 1629: Heavy Construction, Not Elsewhere Classified. Special trade contractors primarily engaged in guardrail construction or installation of highway signs are classified in SIC 1611: Highway and Street Construction, Except Elevated Highways.
234120 (Bridge and Tunnel Construction)
According to the U.S. Census Bureau's Statistical Abstract of the United States, in 2000 there were 906 bridge, tunnel, and elevated highway construction contractors, down from 1,171 in 1997. These firms employed more than 39,000 people. The value of state and local government construction in 2001 totaled $1 billion for tunnels and $10.2 billion for bridges. According to the U.S. National Bridge Inventory, in 2002 there were 617,935 bridges in the United States. Of this total, 266,476 were on county roads, and 144,917 were on state highways. Interstates supported approximately 60,000 bridges. The number of structurally deficient bridges totaled 82,636, and the number of functionally obsolete totaled 79,869.
Roughly 25 percent of the money spent on highway construction in the United States is used for bridge, tunnel, and elevated highway construction, with the remainder spent on "flatwork," such as highways and interstates. The vast majority of the construction work performed by industry firms in 1992 (72 percent) was for bridge and elevated highway construction, while tunnel construction composed only about 12 percent of industry construction. The remaining 17 percent of the industry's construction work encompassed highway, street, and related facilities construction; sewage treatment and water treatment plant construction; and sewer, water main, and related facilities construction. In 1992, 884 industry establishments specialized in bridge and elevated highway construction, while only 122 firms specialized in tunnel construction.
Like general contractors in residential and building construction, general contractors in the bridge, tunnel, and elevated highway construction industry generally assume responsibility for managing an entire construction project, but they may subcontract all or part of a project to various subcontractors. The design and construction of some construction projects may be awarded to a prime contractor and several subcontractors or to a single prime contractor, or the project may be awarded to two or more firms operating in a joint venture. Contractors bid on jobs based on estimates, and the difference between the lowest and highest bids depends on the accuracy of the estimates made of the job's cost. For example, the six bids received by the Florida Department of Transportation in 1994 for the construction of a bridge—a $7 million project—differed by only several hundred thousand dollars. Boston's mammoth Central Artery/Tunnel Project (known as "the Big Dig") involved more than 200 design and construction contracts encompassing tens of thousands of intercontract and intracontract dependencies. Typically, bid prices for highway construction projects tend to go up, as the number of bidders declines on any given project.
In cost-reimbursement contracts, builders were paid for justifiable costs incurred during the project, while fixed-price contracts required builders to absorb any cost overruns themselves. Incentive and performance-based construction contracts rewarded contractors who completed projects by prescribed deadlines or ahead of schedule.
Any construction projects using federal funds were required by law to be awarded on the basis of competitive bids, except in the case of emergencies or if the highway agency could demonstrate a more cost-effective way of assigning contracts. Government agencies also considered service, contractor guarantees, past experience with particular contractors, and options offered by individual bidders when evaluating bids. In order to avoid the appearance of relying on "sole sourcing" for public construction projects, some government agencies wrote project specifications in language general enough to attract several potential bidders. Some government public works agencies held "pre-bid" conferences with prospective contractors to make possible the dissemination of information on a project. Such conferences enabled local contractors or experts with specialized knowledge to add input that could help either the agency formulate specifications on the job or assist contractors in modifying their bids.
In the 1990s federal highway and public works agencies increasingly involved themselves in the execution of construction projects. Known as "partnering," this trend changed the way bridge, tunnel, and elevated highway construction projects were conducted. In the early 1990s, the distinction between private and public construction—at one time determined by which sector paid for the construction work—was determined by which sector owned the project. Industry projects were funded by a combination of federal and state funds. In a typical example from the early 1990s, the Federal Highway Administration (FHWA) paid 80 percent for a cable-stayed bridge across the Mississippi River, while the Illinois Department of Transportation paid the remaining 20 percent.
Driven by their need to find alternative funding sources, a growing number of public agencies developed new financing strategies, such as public-private joint ventures, that allowed state agencies to take advantage of bond market investment funds. The 1991 federal transportation bill also enabled private construction firms for the first time to operate toll collection facilities, while they repaired bridges, tunnels, or highways in order to finance their work without having to invest as much of their own capital up front.
By the early 1990s, 89 percent of state highway agencies were using some form of "team building" or partnering process, and 85 percent incorporated partnering directly into their construction projects. Private and public partnering took several forms, including committing to a joint-mission statement or project charter, reaching agreements on quantifiable objectives of performance, creating an issue-resolution "ladder" to streamline decision making, and jointly developing team-building and problem-solving skills to enhance "team" productivity. An advantage of public-private partnering is that it allows private contractors to review a construction project with a state administrator and, if necessary, adjust a project's specifications, so that contractor capabilities and project requirements meshed.
Almost 67 percent of the value of all industry construction work in 1997 was new construction, with the remainder divided between additions, alterations, and reconstruction—which accounted for 26 percent of the value of the industry's construction work—and maintenance and repair, which represented almost 7 percent.
The public-private partnership funding mechanism flourished in the late 1990s, as construction costs continued to spiral upward, and resistance increased to full public funding of transportation projects. In 1999 Bechtel Group and Kiewit Pacific entered into a contract with the state of Washington, forming a nonprofit corporation to finance and build a companion bridge to the existing Tacoma Narrows bridge. This new bridge is the first major suspension bridge to be constructed in the United State since the 1970s.
The public-private agreement is also an excellent way for a community to acquire a much larger dollar value of improvements for a given amount of public money. This improves the transportation infrastructure and provides many more jobs than a project built solely with public money. In addition to the $350 million used to build the bridge, the state of Washington will invest another $350 million for approaches to the new bridge and to Interstate 5.
Although public-private partnerships have been successful in smoothing the resistance to new bridge and highway projects, it is usually necessary for these new facilities to charge tolls. This presents another avenue of resistance to highway improvements. In addition to the new Tacoma Narrows suspension bridge, Washington State had five other projects on its wish list; these projects failed to go forward because of resistance from antitoll activists.
Although ancient Roman techniques for constructing stone bridges were sophisticated, it was not until the principles of physics were applied to bridge construction in the nineteenth century that bridge building made the transition from craft to a technical and scientific profession. In 1816 the first suspension bridge in the world was constructed over the Schuykill River near Philadelphia by U.S. builders. American bridge construction firms erected the country's first iron arch bridge in Pennsylvania between 1836 and 1839, the first all-metal truss bridge in 1840, the first iron girder railroad bridge in 1845, and the first U.S. bridge with concrete piers or foundations in 1848. In the mid-1850s wrought iron began to replace stone in some bridges, increasing their length and durability, and private U.S. firms began to manufacture "proprietary" bridges to be marketed to railroads and government agencies, a practice that continued until the turn of the century. After 1856 the invention of the Bessemer process for producing steel by reducing the carbon content of iron made possible the incorporation of steel into bridge construction. In 1855 John Roebling designed the first stiffened suspension bridge in Niagara Falls, New York, and 28 years later introduced the use of high-strength steel wire in the supporting cables of the famous Brooklyn Bridge. Civil engineering bridge science came into its own in the 1880s, when poor bridge design and cheap building materials led to rail bridge collapses that called attention to the need for systematic analysis of bridge design and construction methods. In the United States, a premium was placed on inexpensive design, which led to the predominance of the simple triangulated truss design (first used with wooden bridges and later for iron bridges).
Although systematic tunneling for military and other purposes dates back at least to the Roman Empire, the first tunnel in the United States was the Erie Canal, constructed between 1817 and 1825. Because early locomotives did not have the power to climb steep slopes, blasting tunnels through mountains was a necessity. The first such railroad tunnel, constructed for the Allegheny Portage Railroad in Pennsylvania, was completed in 1832 and extended the distance record for rail tunnels from 850 feet to four miles. By 1850, 29 railway tunnels had been built in the United States using only picks, shovels, and explosives. The first steam-operated percussion rock drill was patented in 1849. Compressed air percussion drills came into use in 1851.
Nitroglycerin first was used for blasting purposes in the construction of the Hoosac Tunnel in Massachusetts in the mid-1850s, but by 1865 the excavation of a single cubic yard of rock still required almost four man-hours of labor. The invention of a stable form of nitroglycerin, dynamite, in 1869 made the construction of tunnels for such historic rail lines as the Union-Pacific transcontinental route more practicable. The first underwater railroad tunnel was constructed in 1890, connecting Michigan and Ontario, Canada, and in the same year the first underwater tunnel for horse-drawn carriages was built in Chicago. Although few early tunnels had any linings at all, when used, linings consisted of cast iron rings. This lining method was gradually replaced by such early tunnel-lining materials as timber, brick, and mortar. Tunneling technology was greatly advanced with the development of the Greathead "shield" excavator around the turn of the century, which used air pressure to hold back walls of water, so workers could tunnel underwater.
In 1956 President Dwight Eisenhower initiated a mammoth federally funded program to create a national interstate highway system, later named the Dwight D. Eisenhower System of Interstate and Defense Highways. The system offered industry firms enormous new revenue sources in the construction of bridges, tunnels, and elevated highways. By the mid-1990s, the system, renamed the National Highway System (NHS), encompassed more than 225,000 miles of roads nationwide.
The longest railroad tunnel in North America, measuring 7.7 miles, was constructed in the state of Washington in 1929. As the century progressed, new tunneling techniques began to see wider application. For example, the immersed tube tunnel, also known as the build-and-sink method, enabled underwater tunnels to be built from the surface by lowering prefabricated sections into trenches excavated from the river floor. The first such tunnel was built under the Detroit River between 1906 and 1910 and a second on the West Coast in 1925. In the second half of the twentieth century, tunneling methods, materials, and excavating tools continued to evolve in sophistication and versatility, culminating in the construction of the Channel Tunnel (Chunnel) between Great Britain and France in the 1980s and 1990s. Although the construction of the Chunnel required no radical new departures in tunneling science, its sheer scale, expense, and technical success made it perhaps the single most important tunneling project in history. The engineering success of the tunnel (though marred by its great expense and a major tunnel fire in 1996) led some engineers in the mid-1990s to explore the idea of tunnels connecting Russia and Alaska across the Bering Straits and Morocco and Spain across the Straits of Gibralter.
About 25 percent of the value of highway construction consisted of bridges, overpasses, and tunnels in 1993, while flatwork (primarily roads) accounted for the remaining 75 percent. According to a U.S. Department of Transportation report on the status of the nation's highways, bridges, and transit systems, $49.9 billion was required to maintain the condition and performance of the nation's highways and bridges in 1994. In 1991 it was estimated that approximately 72 percent of existing U.S. bridges were built before 1935, and estimates of the nation's roughly 575,000 bridges that were structurally or functionally deficient in the early 1990s ranged from 14 to 40 percent, with those in New York in most need of repair. In addition, the Federal Highway Administration estimated that another 21 percent of U.S. bridges were not only deficient but obsolete, leaving a grand total of 225,000 to 231,000 below-par bridges nationwide. Roughly 42 percent of the backlog for bridge rehabilitation in the early 1990s involved pavement costs, and the remaining 58 percent was for constructing additional capacity. By 1996 the estimated cost of upgrading the backlog of deficient U.S. bridges had risen to about $72 billion. By 1998 the value of new construction for highways, including elevated highways and bridges, was expected to increase to almost $39 billion.
Perhaps the largest single bridge, tunnel, and elevated highway construction project in the United States in the mid-1990s was the $7.7 billion Central Artery/Third Harbor Tunnel project in Boston, which consisted of an immersed three-quarter-mile tube tunnel and elevated highway system designed to connect several Boston neighborhoods with the rest of the city. With roughly 22 percent finished by mid-1996, the project was expected to be completed in 2004. A total of 100 contractors, subcontractors, and government agencies were involved in the Boston project, led by the Bechtel Group and Parsons Brinckerhoff.
Other major U.S. construction projects in the mid-1990s included the widening of the George P. Coleman Bridge in Virginia (the second-largest double-swing span bridge in the world) by Tidewater Construction; the construction of the Des Plaines River section of Chicago's deep tunnel and reservoir plan by Kenny Construction, Kiewit Construction Group, and J. F. Shea; the completion of the Cumberland Gap Highway Tunnel project between Kentucky and Virginia (including two-lane tunnels and seven roadway bridges); and a $3 billion deep tunnel wastewater collection, treatment, and disposal system in Singapore by CH2M Hill and Parsons Brinckerhoff. In the mid-1990s New York City mayor Rudolf Guiliani began pushing the construction of a multibillion dollar water tunnel to supplement New York's water supply.
In November 1995 President Clinton signed the National Highway System Designation Act of 1995, which injected an additional $5.4 billion into the federal contribution set aside for the NHS. By one estimate each $1 billion of federal highway aid created roughly 7,900 fulltime, on-site construction jobs in the United States. One provision of the act also raised the maximum federal share for toll project funding to 80 percent, up from a variable 50 to 80 percent previously.
The Intermodal Surface Transportation Efficiency Act (ISTEA)—an annually budgeted omnibus transportation legislation package—and FHWA funds accounted for a large percentage of the revenues of industry firms. In 1991 ISTEA provided $130 billion in transportation funding. In mid-1998 President Clinton signed a funding bill that was a follow-up to the 1991 ISTEA legislation. Called the "Transportation Equity Act for the 21st Century" (TEA-21), it provides $217 billion through the year 2003 for all types of surface transportation. It is the largest public works legislation in U.S. history. Since it was signed into law, implementation of the act was passed to each state's transportation agency along with the state's share of the funding. The state is responsible for parceling out its share of the funds for use in highway, bridge, and tunnel projects. The transportation industry is watching carefully how the money is distributed and how well transportation contractors and government are prepared to fill the transportation needs of the century.
States have received this funding with mixed blessings. For instance, California's share of the TEA-21 funding is more than $14 billion; this money filled a large void in funding caused by the voters' rejection of $4 billion in transportation bond issues in the late 1990s. Although Illinois's allocation is expected to be $5.3 billion, the state ranks first in truck traffic, yet it only has the sixth highest level of funding in the TEA-21 package. New York's $8 billion allocation is music to the state's ears—with this money New York will be able to complete even the smaller projects that usually get pushed aside when transportation priorities are assigned.
Of the more than 600,000 bridges in the United States, 45 percent are under the financial jurisdiction of state governments, and 38 percent are controlled by county authorities. The remainder are maintained by cities, and a small number are under the control of other agencies. The development, construction, and maintenance of these bridges, along with the handful of tunnels in the United States, are dependent on the funding priorities of local, state, and federal legislative bodies. The sluggish economy of the early 2000s pushed many state governments, in particular, to the brink of financial disaster. With the coffers nearing empty, new and upgraded bridge and tunnel projects were stalled.
In April 2003 the Bush administration proposed the Safe and Flexible Transportation Efficiency Act of 2003 (SAFETEA) to replace TEA-21. Whereas TEA-21 authorized $218 billion over six years, SAFETEA would provides a modest increase to $247 billion. At the same time the Senate Budget Committee was proposing a spending level of $311.5 billion, and the House Transportation and Infrastructure Committee was looking at an even higher appropriation of $375 billion. In May the new highway funding plan was worked out to approximately $320 billion, which becomes effective in October 2003. A portion of the funding will go toward upgrading and building new tunnels and bridges to attempt to ease historically high traffic congestion levels. New projects will likely include new bridges to serve the ports of Charleston, South Carolina, and New Orleans.
The leading bridge-building firms in 2002 were Peter Kiewit Sons, Inc. (with $3.7 billion in sales), Granite Construction ($1.8 billion), and Skanska USA ($1.4 million). Peter Kiewit Sons was formed in the 1880s by a Dutch immigrant brick maker, and under the founder's son the firm built dams, power plants, and canals during the New Deal and highways after World War II. In the mid-1990s Kiewit formed a joint venture with the Bechtel Group called United Infrastructure Co. to design, build, finance, and operate private toll roads, bridges, water pipelines, and treatment facilities.
The bridge, tunnel, and elevated highway industry encompasses a wide diversity of engineering specializations. A typical advertisement placed in the jobs section of the World Wide Web site of Road and Bridges (a leading industry trade magazine), for example, called for an "engineering project analyst" to join up with a state's department of transportation and "assist in contracting for engineering consultant services for highway design projects." His or her responsibilities included determining fees and statistical measures and assisting in the development of agreements with consulting engineers. In addition to requiring state licensure as an engineer, the job required "experience in planning and design of highway improvement projects and knowledge of state government procurement practices." The pay range was $41,800 to $54,725. For an annual salary between $45,470 and $64,230, an engineering design manager for a municipal construction agency might be required to review private construction development projects, resolve right-of-way issues (i.e., legal arrangements allowing highway projects to be built on specified lands), and oversee municipal permit work.
Structural engineers might be called on to design multispan concrete bridges; to have expertise in designing drilled piers, analyzing soil reports, and driving piles, caissons, abutments, and mats for bridge foundations; and to have experience drafting plans and sections with computer-aided design (CAD) software. With a B.S. degree and two years of specific experience, an entry-level engineer who qualified for this position might expect to be paid at least $35,000 per year. The majority of the states in the country did not require engineers to possess a degree to practice the profession in the mid-1990s.
Project managers for a freeway construction firm could be expected to prepare design reports, environmental assessments, traffic management analyses, or bridge condition reports and be able to assume overall control of a project involving professionals from several firms. Geotechnical engineers conducted soil analyses to determine the suitability of a site for heavy construction foundations. Other engineers were required to have experience in traffic-flow theory and related modeling software, and to have thorough knowledge of such industry manuals as the Highway Capacity Manual. A senior bridge and highway engineer acted as a technical reviewer for quality assurance of bridge and highway designs, plans and construction documents, and condition inspection procedures and reports.
Project schedulers are generally required to utilize such project scheduling software systems as Primavera System Inc.'s P3, and to have experience analyzing the impact of change orders, tracking delays, and scheduling large, complicated, heavy construction projects. So-called special trade contractors perform such tasks as painting and electrical work, and general superintendents directed all functions of large construction operations according to established schedules and procedures. Estimators gather basic data on proposed construction projects from engineering or architectural plans and site inspection, and computed the cost of construction, factoring in profit and overhead. Other integral industry positions included expediters, materials purchasing agents, marketing managers, drafters, construction inspectors, job-site safety directors, office managers, and foremen.
Construction occupations in the bridge, tunnel, and elevated highway industry were similar to positions in the construction industry as a whole but also included mining industry-related positions, such as mining or tunneling machine operators and drainage constructors. The most important construction occupations included electricians, cement masons, painters, reinforcing ironworkers, structural ironworkers, heavy construction and highway laborers, crane operating engineers, operating engineers of light equipment, operating engineers of heavy equipment, sheet metal workers, and carpenters.
Union efforts in the 1990s to increase membership levels in the heavy construction and highway industries included strategies carried out by the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO) and its building and construction trades department to challenge contractors on their compliance with environmental regulations, membership campaigns targeting specific corporations, political pressure, and agreements for union-only representation in major government and private projects. Highway and heavy construction work, such as bridge, tunnel, and elevated highway construction, has historically been one of the most dangerous occupations in the United States. In the early 1990s, the National Transportation Safety Board (NTSB) issued reports calling for safeguards in highway construction sites, such as separating traffic lanes in detoured highway construction areas and redesigning highway work zones. Another area of concern stemmed from the unique hazards associated with working in confined spaces, such as sewer and tunnel construction projects. Historically, about 50 workers per year died in confined space construction accidents and another 5,000 suffered serious injuries. In 1993 the Occupational Health and Safety Administration (OSHA) issued new rules governing the safety of workers in confined spaces, requiring employers to warn employees about potential hazards, provide them with protective and emergency equipment, and ensure they follow specific procedures before entering confined work spaces.
Beginning in the early 1970s, the world's construction industry became increasingly international in scope, and early on U.S. contractors dominated the global scene. In 1992 U.S. firms were awarded about 49 percent of all international construction contracts, including contracts awarded to foreign subsidiaries of U.S. firms. Beginning at least in the 1980s, however, U.S. construction firms began to fall behind Japanese and European contractors in the development of new construction technologies and building methods, and by 1992 were losing market share in international contracts at a rapid clip. By one estimate, U.S. firms were 10 years behind the pace in construction technology and took twice as long on average as the Japanese to erect a structure. And according to a study by the U.S. Department of Commerce, American construction firms could no longer bring either "strong technological or management advantage" to the bidding process for international infrastructure contracts.
Construction firms in Japan—the world's largest market at $700 billion in 1995—were the world leaders in the use of high-performance steel, automated equipment, and intelligent buildings and systems, and European firms were the leaders in high-performance asphalt, tunneling, high-speed rail work, and marine construction. The leading U.S. construction firm with more than 50 percent of its revenues from transportation construction work (including bridges, tunnels, and elevated highways) was Kiewit Construction Group of Omaha, Nebraska (52 percent), which, however, only ranked 59th worldwide in 1995 revenues.
In the mid-1990s the largest foreign construction firms with more than 50 percent of their revenues deriving from transportation construction work were Bouygues SA of France, Toa Corporation of Japan, China Railway Construction Corporation, China Harbor Engineering Co., and Ret-Ser Engineering Agency of Taiwan. Although lagging in the global bridge, tunnel, and elevated highway market, U.S. construction firms in general continued to be the leaders in the Middle East, Latin America, and Canada.
The most promising international markets for industry firms during the early 1990s were located in developing countries, where anticipated transportation infrastructure needs were estimated to cost as much as $100 billion a year. Nations in the Far East and Pacific Rim, particularly Vietnam, Cambodia, and China, were expected to be the site of much of the international bridge and tunnel industry's most significant projects in the 1990s and beyond. In the mid-1990s an increasing number of major international infrastructure projects were being developed on a "build-own-operate-transfer" (BOOT) basis. In BOOT contracts, which were invented by the Turkish government in the 1980s, the construction firm not only performed the construction work but also operated the finished facility until it became profitable, at which point it transferred ownership to the local government. Another international trend that had just begun to have an effect on the bridge, tunnel, and elevated highway industry was the privatization of international infrastructure work, especially in developing countries with little capital to spend on huge projects. In these arrangements, the builder itself offered to supply the project funding—for a power plant or toll road, for example—and expected to recoup its investment from the income generated by the project when it was operational.
Of the 50 largest U.S. construction contractors in the mid-1990s, the vast majority earned significant portions of their business from international work. Although U.S. construction firms did not have a strong presence in international transportation construction work in the mid-1990s, several major U.S. construction firms did a substantial amount of transportation construction work overseas (which in addition to bridges, roads, and tunnels included airports, canals, locks, marine facilities, dredging work, and railroad construction). Kiewit Construction Group, for example, derived 36 percent of its revenues—its largest segment—from transportation-related construction projects. Morrison Knudson of Boise, Idaho, derived 35 percent of its total market from such construction work, and the Parsons Corporation and Ellis-Don Construction Inc. derived 12 and 22 percent, respectively, of their revenues from international transportation projects.
Innovations in bridge, tunnel, and elevated highway construction technology in the 1990s occurred in three broad areas: improvements in construction materials, improvements in construction tools and equipment, and wider use of sophisticated engineering and management computer software and automation technologies.
Materials. Although steel has been a highly popular material for bridge and tunnel construction and continued to prove its usefulness in new weathered and improved grades, industry researchers in the 1990s continued to look for other suitable materials. One such alternative was aluminum, which the American Association of State Highway and Transportation (AASHT) officials began recommending as a practical substitute for steel girders and subfloors in bridges. Because of its light weight, anticorrosive properties, and favorable weight-to-strength ratio, aluminum was also used for bridge decks in place of other construction materials.
Although steel has been used almost exclusively as the material for liner plates along the walls of tunnels, plastic polymers offered cost savings in construction time, labor, and equipment in certain tunneling operations. Similarly, the search for alternatives to the traditional welded wire highway concrete reinforcement led to the development of fiber-reinforced concrete, using acrylic, nylon, carbon, and polyethylene materials among others to create stronger, more sound, and cheaper concrete reinforcing materials. Another reinforcement alternative, glass-fiber-reinforced concrete, was also comparatively inexpensive and offered versatility and light weight. Concrete reinforcement using steel fiber has been in use since the late 1950s and was also gaining wider use as an alternative to traditional reinforcing materials in the early 1990s. Plates made of carbon steel were also introduced as a reinforcing element in highway and bridge construction. Other innovations in bridge, tunnel, and elevated highway construction materials included the use of electrical current—called cathodic protection—to counter corrosion of concrete by road salts, as well as new technology for making and installing buried segmental precast arch structures for use in road and rail bridges and tunnels.
Between 1988 and mid-1993, the FHWA's Strategic Highway Research Program developed 130 products aimed at improving highway construction and operation methods, including new pavement engineering techniques and concrete and asphalt with enhanced performance characteristics. By 1996 more than 100 case studies reporting the program's development of successfully implemented technologies had been documented. These included a new road-surfacing material known as Superpave, spray-injection technologies for filling potholes, bridge management software, and concrete anticorrosion technologies. Similarly, the FHWA's Geotechnical Research program developed improvements for bridge foundations, retaining walls, and embankments and maintained experimentation sites for assessing new methods for quantifying the properties and behavior of soils to predict their suitability for highway and bridge construction.
According to a July 1999 article in ENR , a leading industry journal, cable-stays and composites represent the future of bridge-building materials. Bridges will last longer and will require less maintenance. In the traditional suspension bridge, thick cables are strung from the support towers, and the bridge deck hangs from smaller cables attached to the thicker cable. Cable-stayed bridges are similar, except that the cables that hold the bridge deck are attached directly to the support towers. Along with new technology in the manufacture and composition of the towers and cables, it is believed that bridges of the future will also have traffic monitoring and de-icing systems to help with operation and maintenance.
Equipment. Among the many advances in bridge, tunnel, and elevated highway construction equipment in the 1980s and 1990s was the increased use of highway and bridge surface groovers and grinders using diamond-tipped saw blades to cut grooves into pavement for vehicle traction and water drainage. Also utilized more frequently was an underground excavating machine for cutting two-lane road arch tunnels through hard granite. The machine formerly had been used only in underground mining, offering an alternative to drilling and breaking rock by hydraulic wedge or nonexplosive demolition.
Software and Automation. The introduction of engineering/design and project management software had a profound effect on the way bridge, tunnel, and elevated highway construction firms conducted their business. Among the advantages such packages offered were the capability to produce clean and accurate technical drawings by users without drafting skills, correct and replot drawings in a fraction of the time required by manual methods, quickly optimize designs to explore alternative approaches to a project, and better understand a project's total design features through three-dimensional visualization and imaging features.
On the project management and administrative side of construction operations, software programs like "Auto Project" or Primavera's P3 facilitated easy scheduling and project monitoring, time/cost trade-off analyses, and customized reports. Packages like "WinEst" provided building construction estimating features for the Windows operating system and allowed construction managers to create detailed project estimates. Quick scheduling also was completed with Critical Path Method software programs to monitor the progress of individual contracts and an entire construction project.
In the 1990s Japanese firms began dominating the global construction market by integrating automated construction systems and robotics into their construction projects. Systems like Obayashi Corporation's Automated Building Construction System enabled structures to rise up in half the time as traditional methods. Automated machines delivered the building materials, from columns and beams to floor panels and interior fittings, to the floor under construction, which was enclosed in a climate-controlled "factory-like" environment. Robots then precisely positioned the materials at their appropriate points on the construction floor, and automatic welding machines welded the columns and beams. When the floor was finished, an integrated hydraulic system lifted the entire "shop" up one level to start the process anew. Such systems not only shortened construction schedules by allowing around-the-clock construction, they ensured that the structure was of uniform quality and reduced labor costs and construction site injuries. Using such technologies, by the mid-1990s the Japanese construction firms had become the world's most competitive.
As in many other U.S. industries, the emergence of the Internet and the World Wide Web in the mid-1990s gave industry firms new opportunities to market themselves inexpensively through company Web sites and links to construction industry organizations, journals, and databases. By mid-decade the construction industry was also experimenting with processing federal construction grants remotely through the Web.
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