Civil Engineering

Summary

Civil engineering is the branch of engineering concerned with the design, construction, and maintenance of fixed structures and systems, such as large buildings, bridges, roads, and other transportation systems, and water supply and wastewater treatment systems. Civil engineering is the second oldest field of engineering, with the term civil initially used to differentiate it from the oldest field of engineering, military engineering. The major subdisciplines of civil engineering are structural, transportation, and environmental engineering. Other areas of specialization include geotechnical, hydraulic, construction, and coastal engineering.

Definition and Basic Principles

Civil engineering is a broad engineering field, encompassing subdisciplines ranging from structural engineering to environmental engineering, some of which have become separate engineering fields. For example, while environmental engineering is included as an area of specialization within most civil engineering programs, many colleges offer separate environmental engineering degree programs.

Civil engineering, like engineering in general, is a profession with a practical orientation and an emphasis on building things and making things work. Civil engineers use their knowledge of the physical sciences, mathematics, engineering sciences, and empirical engineering correlations to design, construct, manage, and maintain structures, transportation infrastructure, and environmental treatment equipment and facilities.

Empirical engineering correlations are equations, graphs, or nomograms based on experimental measurements and give relationships among variables of interest for a particular engineering application. Such correlations are important in civil engineering because usable theoretical equations are not available for all necessary calculations. For example, the Manning formula is an experimental description of the average velocity of a liquid flowing in an open channel, based on the volumetric flow rate, the slope of the channel, the depth of the liquid, and the size, shape, and material of the bottom and sides of the channel. Rivers, irrigation ditches, and concrete channels used to transport wastewater in treatment plants are examples of open channels. Similar empirical relationships are used in transportation engineering, structural engineering, and other specialties within civil engineering.

Background and History

Civil engineering is considered the second oldest field of engineering. The term civil engineering came into use in the mid-eighteenth century and initially referred to any practice of engineering by civilians for nonmilitary purposes. Before this time, most large-scale construction projects, such as roads and bridges, were done by military engineers. Early civil engineering projects were in areas such as water supply, roads, bridges, and other large structures—the same type of engineering work that exemplifies civil engineering in modern times.

Although the terminology did not yet exist, civil engineering projects were carried out in early times. Examples include the Egyptian pyramids (about 2700–2500 BCE), well-known Greek structures such as the Parthenon (447–438 BCE), the Great Wall of China (220 BCE), and the many roads, bridges, dams, and aqueducts built throughout the Roman Empire.

Most existing engineering fields split off from civil engineering or one of its offshoots as new fields emerged. For example, mechanical engineering emerged in the early nineteenth century due to the increased use of machines and mechanisms.

How It Works

In addition to mathematics, chemistry, and physics, civil engineering extensively uses principles from several engineering science subjects—engineering mechanics (statics and strength of materials), soil mechanics, and fluid mechanics.

Engineering Mechanics—Statics. As implied by the term statics, this area of engineering concerns objects that are not moving. The fundamental principle of statics is that any stationary object must be in static equilibrium. That is, any force on the object must be canceled out by another force that is equal in magnitude and acting in the opposite direction. There can be no net force in any direction on a stationary object because if there were, it would not be stationary. The object in static equilibrium could be an entire structure or any part of a structure, down to an individual member in a truss. Calculations for an object in static equilibrium are often done using a free-body diagram, which is a sketch of the object showing all the external forces acting on it. The principle used for calculations is that the sum of all the horizontal forces acting on the object must be zero and the sum of all the vertical forces acting on the object must also be zero. Working with the forces as vectors helps to find the horizontal and vertical components of forces acting on the object from some direction other than horizontal or vertical.

Engineering Mechanics—Strength of Materials.  This subject is sometimes called mechanics of materials. Statics works only with forces external to the body that are in equilibrium, but the strength of materials uses the same principles and considers internal forces in a structural member. This determines the required material properties to ensure that the member can withstand the internal stresses that will be placed on it.

Soil Mechanics. Knowledge of soil mechanics is needed to design the foundations for structures. Any structure resting on the earth is supported by the soil beneath it. A properly designed foundation will provide adequate long-term support for the structure above it. Inadequate knowledge of soil mechanics or foundation design may lead to something such as the Leaning Tower of Pisa. Topics in soil mechanics include the physical properties of soil, compaction, distribution of stress within soil, and water flow through soil.

Fluid Mechanics. Fundamental principles of physics are used for some fluid mechanics calculations. Examples are conservation of mass (called the continuity equation in fluid mechanics) and conservation of energy (called the energy equation or the first law of thermodynamics). Some fluid mechanics applications, however, use empirical (experimental) equations or relationships. Calculations for flow through pipes or flow in open channels, for example, use empirical constants and equations.

Knowledge from Engineering Fields of Practice. In addition to these engineering sciences, a civil engineer uses accumulated knowledge from the civil engineering areas of specialization. Some important fields include hydrology and hydrogeology, geotechnical engineering, structural engineering, transportation engineering, and environmental engineering. In each of these fields are theoretical equations, empirical equations, graphs or nomograms, guidelines, and rules of thumb that civil engineers use for designing and constructing projects related to structures, roads, stormwater management, or wastewater management, for example.

Civil Engineering Tools. Several tools available for civil engineers to use in practice are engineering graphics, computer-aided drafting and design (CAD), surveying, and geographic information systems (GIS). Engineering graphics (engineering drawing) has been a mainstay in civil engineering since its inception, used for preparing and interpreting plans and drawings. Most of this work has come to be done using CAD. Surveying is a tool that has also long been a part of civil engineering. From laying out a road or a building foundation to measuring the slope of a river or a sewer line, surveying is useful for many civil engineering fields. Civil engineers often work with maps, and GIS, a much newer tool than engineering graphics or surveying, makes this type of work more efficient.

Codes and Design Criteria. Much of the work done by civil engineers is either directly or indirectly for the public. Therefore, in most fields of civil engineering, work is governed by codes or design criteria specified by some state, local, or federal agency. For example, federal, state, and local governments have building codes; state departments of transportation specify design criteria for roads and highways; and wastewater-treatment processes and sewers must meet federal, state, and local design criteria.

Applications and Products

Structural Engineering. Civil engineers design, build, and maintain many and varied structures. These include bridges, towers, large buildings (skyscrapers), tunnels, and sports arenas. Some of the civil engineering areas of knowledge needed for structural engineering are soil mechanics, geotechnical engineering, foundation engineering, engineering mechanics (statics and dynamics), and strength of materials.

When the Brooklyn Bridge was built over the East River in New York City (1870–83), its suspension span of 1,595 feet was the longest in the world. It remained the longest suspension bridge in North America until the Williamsburg Bridge was completed in New York City in 1903. The Brooklyn Bridge joined Brooklyn and Manhattan and helped establish the New York City Metropolitan Area.

The Golden Gate Bridge, which crosses the mouth of San Francisco Bay with a main span of 4,200 feet, had nearly triple the central span of the Brooklyn Bridge. It was the world's longest suspension bridge from its completion in 1937 until 1964, when the Verrazano-Narrows Bridge opened in New York City with a central span 60 feet longer than the Golden Gate Bridge.

Japan's Akashi Kaikyō Bridge, which crosses the Akashi Strait between Honshu and Awaji Island, became the world's longest suspension bridge upon its completion in 1998. It has a single suspended span of 6,532 feet and a total length of 12,831 feet.

One of the most well-known early towers illustrates the importance of good geotechnical engineering and foundation design. Italy's famous Tower of Pisa, commonly known as the Leaning Tower of Pisa, started to lean to one side very noticeably while still under construction, which lasted from 1173 until 1372. Its height of about 185 feet is not extremely tall compared to towers built later, but it was impressive when it was built. It has an extreme tilt—more than five meters off perpendicular—because it was built on rather soft, sandy soil with a foundation that was not deep enough or spread out enough to support the structure. Despite this, the Tower of Pisa has remained standing for more than six hundred years.

Another well-known tower, the Washington Monument, was completed in 1884. At 555 feet in height, it was the world's tallest tower until the Eiffel Tower, nearly 1,000 feet tall, was completed in 1889. The Washington Monument remains the world's tallest masonry structure. The Gateway Arch in St. Louis, Missouri, is the tallest monument in the United States, at 630 feet.

The 21-story Flatiron Building opened in New York City in 1903 and was one of the first skyscrapers. It is 285 feet tall and its most unusual feature is its triangular shape, which was well suited to the wedge-shaped piece of land on which it was built. The 102-floor Empire State Building, completed in 1931 in New York City with a height of 1,250 feet, earned the title of the world's tallest building at that time, outdoing the Chrysler Building, which was still under construction, by 204 feet. The Sears Tower (now the Willis Tower) in Chicago is 1,450 feet tall and was the tallest building in the world when it was completed in 1974. Since its construction, several taller buildings have been constructed including the Burj Khalifa in Dubai, which is a record-breaking 2,722 feet high.

Some interesting examples of tunnels go through mountains and under the sea. The Hoosac Tunnel, built from 1851 to 1874, connected New York State to New England with a 4.75-mile railway tunnel through the Hoosac Mountain in northwestern Massachusetts. It was the longest railroad tunnel in the United States for over fifty years. Mont Blanc Tunnel, built between 1957 and 1965, is a 7.25-mile-long highway tunnel under Mont Blanc in the Alps that connects Italy and France. The Channel Tunnel, one of the most publicized modern tunnel projects, spans 31 miles beneath the English Channel to connect Dover, England, and Calais, France.

Transportation Engineering. Civil engineers also design, build, and maintain various transportation projects, such as roads, railroads, and pipelines.

Many long, dramatic roads and highways have been built by civil engineers, ever since the Romans became the first builders of an extensive network of roads. The Appian Way is the best known of the many long, straight roads built by the Romans. Construction on the project was started in 312 BCE by the Roman censor Appius Claudius Caecus. By 244 BCE, it extended about 360 miles from Rome to the port of Brundisium in southeastern Italy. The Pan-American Highway, often billed as the world's longest road, connects North America and South America. The original Pan-American Highway ran for more than 15,500 miles, from Texas to Argentina. It later extended from Prudhoe Bay, Alaska, to the southern tip of South America, with a total length of nearly 30,000 miles.

The US interstate highway system was the world's biggest earthmoving project. Started in 1956 by the Federal Highway Act, it grew to cover a total distance of nearly 47,000 miles. This massive highway construction project transformed the American system of highways and had major cultural impacts.

The building of the First Transcontinental Railroad, completed in 1869, was a major engineering feat. The railroad extended nearly 2,000 miles, connecting San Francisco to the existing East Coast network in Council Bluffs, Iowa. Logistics was a major part of the project, with the need to transport steel rails and wooden ties at great distances. An even more formidable task was the construction of the Trans-Siberian Railway, the world's longest railway. It was built between 1891 and 1904 covering 5,900 miles across Russia, from Moscow in the west to Vladivostok in the east.

The Denver International Airport, which opened in 1993, was a very large civil engineering project. This airport covers more than double the area of all of Manhattan Island.

The first oil pipeline in the United States was a five-mile-long, two-inch-diameter pipe that carried 800 barrels of petroleum per day. Pipelines have become much larger and longer since then. The Trans-Alaska Pipeline System, with 800 miles of 48-inch diameter pipe, can carry 2.14 million barrels per day. At the peak of construction, 20,000 people worked twelve-hour days, seven days a week.

Water Resources Engineering. Another area of civil engineering practice is water resources engineering, with projects such as canals, dams, dikes, and seawater barriers.

The oldest known canal still in operation is China's Grand Canal, constructed between 485 BCE and 283 CE. The Grand Canal is more than 1,000 miles long, although its route has varied because of several instances of rerouting, remodeling, and rebuilding. The 363-mile-long Erie Canal was built from 1817 to 1825 to connect Albany and Buffalo across New York, thus overcoming the Appalachian Mountains as a barrier to trade between the eastern United States and the newly opened western United States. The economic impact of the Erie Canal was tremendous. It reduced the cost of shipping a ton of cargo between Buffalo and New York City from about $100 per ton (over the Appalachians) to $4 per ton (through the canal).

The Panama Canal, constructed from 1881 to 1914 to connect the Atlantic and Pacific Oceans through the Isthmus of Panama, is only about 50 miles long, but its construction presented major challenges because of the soil, the terrain, and the tropical illnesses that killed many workers. Upon its completion, the Panama Canal reduced the travel distance from New York City to San Francisco by about 9,000 miles.

When the Hoover Dam was completed in 1936 on the Colorado River at the Colorado-Arizona border, it was the world's largest dam, at a height of 726 feet and crest length of 1,224 feet. The technique of passing chilled water through pipes enclosed in the concrete to cool the newly poured concrete and speed its curing was developed for the construction of the Hoover Dam and is still in use. The Grand Coulee Dam, in the state of Washington, was the largest hydroelectric project in the world when it was built in the 1930s. It has an output of 10,080 megawatts. The Itaipu Dam, on the Parana River along the border of Brazil and Paraguay, is also one of the largest hydroelectric dams in the world. It began operation in 1984 and is capable of producing 13,320 megawatts.

Dikes, dams, and similar structures have been used for centuries for protection against flooding. The largest sea barrier in the world is a 2-mile-long surge barrier in the Oosterschelde estuary of the Netherlands, constructed from 1958 to 1986. Called the Deltawerken (Delta Works), this project was intended to reduce the danger of catastrophic flooding. The impetus that brought this project to fruition was a catastrophic flood in the area in 1953. A major part of the barrier design consists of sixty-five huge concrete piers, weighing 18,000 tons each. These piers support tremendous 400-hundred-ton steel gates to create the sea barrier. The lifting and placement of these huge concrete piers exceeded the capabilities of any existing cranes, so a special U-shaped ship was built and equipped with gantry cranes. The project used computers to help in the guidance and placement of the piers. A stabilizing foundation used for the concrete piers consists of foundation mattresses made up of layers of sand, fine gravel, and coarse gravel. Each foundation mattress is more than 1 foot thick and more than 650 feet by 140 feet, with a smaller mattress on top.

Careers and Course Work

A bachelor's degree in civil engineering is the requirement for entry into this field. Registration as a professional engineer is required for many civil engineering positions. In the United States, a graduate from a bachelor's degree program accredited by the Accreditation Board for Engineering and Technology is eligible to take the Fundamentals of Engineering exam to become an engineer in training. After four years of professional experience under the supervision of a professional engineer, one is eligible to take the Professional Engineer exam to become a registered professional engineer.

A typical program of study for a bachelor's degree in civil engineering includes chemistry, calculus and differential equations, calculus-based physics, engineering graphics/AutoCAD, surveying, engineering mechanics, strength of materials, and perhaps engineering geology, as well as general education courses during the first two years. This is followed by fluid mechanics, hydrology or water resources, soil mechanics, engineering economics, and introductory courses for transportation engineering, structural engineering, and environmental engineering, as well as civil engineering electives to allow specialization in one of the areas of civil engineering during the last two years.

A master's degree in civil engineering that provides additional advanced courses in one of the areas of specialization, a master's degree in business administration (MBA), or an engineering management master's degree complements a bachelor's of science degree and enables the holder to advance more rapidly. A master's of science degree would typically lead to more advanced technical positions, while an MBA or engineering management degree would typically lead to management positions. The need for graduate work grew more important in the 2010s due to new standards known as the Body of Knowledge that have become increasingly significant in civil engineering.

Anyone aspiring to a civil engineering faculty or research position must obtain a doctoral degree. To properly prepare for doctoral-level study, any master's-level study should pursue a research-oriented master of science degree rather than a master's degree in engineering or a practice-oriented master of science degree.

Social Context and Future Prospects

Civil engineering projects typically involve basic infrastructure needs such as roads and highways, water supply, wastewater treatment, bridges, and public buildings. These projects may be new construction or repair, maintenance, or upgrading of existing highways, structures, and treatment facilities. The buildup of such infrastructure since the beginning of the twentieth century has been extensive, leading to a continuing need for the repair, maintenance, and upgrading of existing structures. In the early twenty-first century, civil engineers have also been increasingly needed for work on renewable energy projects such as wind farms and solar arrays and the construction of new waste treatment plants and other water systems.

Demand for civil engineering can also be affected by shorter-term social or political trends or other forces. For example, a government may invest more in infrastructure at various times, as in the case of the $1.2 trillion infrastructure bill signed into law by President Joe Biden in 2021. Such legislation can help create many new civil engineering jobs.

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