Saturday, March 27, 2010

civil engineering profession

Civil engineering is a professional engineering discipline that deals with the design, construction and maintenance of the physical and naturally built environment, including works such as bridges, roads, canals, dams and buildings.[1][2][3] Civil engineering is the oldest engineering discipline after military engineering,[4] and it was defined to distinguish non-military engineering from military engineering.[5] It is traditionally broken into several sub-disciplines including environmental engineering, geotechnical engineering, structural engineering, transportation engineering, municipal or urban engineering, water resources engineering, materials engineering, coastal engineering,[4] surveying, and construction engineering.[6] Civil engineering takes place on all levels: in the public sector from municipal through to federal levels, and in the private sector from individual homeowners through to international companies.[citation needed]

[edit] History of the civil engineering profession

The Falkirk Wheel in Scotland.

Engineering has been an aspect of life since the beginnings of human existence. The earliest practices of Civil engineering may have commenced between 4000 and 2000 BC in Ancient Egypt and Mesopotamia when humans started to abandon a nomadic existence, thus causing a need for the construction of shelter. During this time, transportation became increasingly important leading to the development of the wheel and sailing. The construction of Pyramids in Egypt (circa 2700-2500 BC) might be considered the first instances of large structure constructions. Other ancient historic civil engineering constructions include the Parthenon by Iktinos in Ancient Greece (447-438 BC), the Appian Way by Roman engineers (c. 312 BC), the Great Wall of China by General Meng T'ien under orders from Ch'in Emperor Shih Huang Ti (c. 220 BC)[6] and the stupas constructed in ancient Sri Lanka like the Jetavanaramaya and the extensive irrigation works in Anuradhapura. The Romans developed civil structures throughout their empire, including especially aqueducts, insulae, harbours, bridges, dams and roads.

Until modern times there was no clear distinction between civil engineering and architecture, and the term engineer and architect were mainly geographical variations referring to the same person, often used interchangeably.[7] In the 18th century, the term civil engineering began to be used to distinguish it from military engineering.[5]

See also: History of structural engineering
The Archimedes screw was operated by hand and could raise water efficiently.

The first self-proclaimed civil engineer was John Smeaton who constructed the Eddystone Lighthouse.[4][6] In 1771 Smeaton and some of his colleagues formed the Smeatonian Society of Civil Engineers, a group of leaders of the profession who met informally over dinner. Though there was evidence of some technical meetings, it was little more than a social society.

In 1818 the Institution of Civil Engineers was founded in London, and in 1820 the eminent engineer Thomas Telford became its first president. The institution received a Royal Charter in 1828, formally recognising civil engineering as a profession. Its charter defined civil engineering as

the art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states, both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation and docks for internal intercourse and exchange, and in the construction of ports, harbours, moles, breakwaters and lighthouses, and in the art of navigation by artificial power for the purposes of commerce, and in the construction and application of machinery, and in the drainage of cities and towns.[8]

The first private college to teach Civil Engineering in the United States was Norwich University founded in 1819 by Captain Alden Partridge.[9]. The first degree in Civil Engineering in the United States was awarded by Rensselaer Polytechnic Institute in 1835.[10] The first such degree to be awarded to a woman was granted by Cornell University to Nora Stanton Blatch in 1905.[citation needed]

[edit] History of the science of civil engineering

Pont du Gard, France, a Roman aqueduct built circa 19 BC.

Civil engineering is the application of physical and scientific principles, and its history is intricately linked to advances in understanding of physics and mathematics throughout history. Because civil engineering is a wide ranging profession, including several separate specialized sub-disciplines, its history is linked to knowledge of structures, materials science, geography, geology, soils, hydrology, environment, mechanics and other fields.

Throughout ancient and medieval history most architectural design and construction was carried out by artisans, such as stone masons and carpenters, rising to the role of master builder. Knowledge was retained in guilds and seldom supplanted by advances. Structures, roads and infrastructure that existed were repetitive, and increases in scale were incremental.[11]

One of the earliest examples of a scientific approach to physical and mathematical problems applicable to civil engineering is the work of Archimedes in the 3rd century BC, including Archimedes Principle, which underpins our understanding of buoyancy, and practical solutions such as Archimedes' screw. Brahmagupta, an Indian mathematician, used arithmetic in the 7th century AD, based on Hindu-Arabic numerals, for excavation (volume) computations.[12]

[edit] The civil engineer

[edit] Education and licensure

Main article: Civil engineer
The Institution of Civil Engineers headquarters in London

Civil engineers typically possess an academic degree with a major in civil engineering. The length of study for such a degree is usually three to five years and the completed degree is usually designated as a Bachelor of Engineering, though some universities designate the degree as a Bachelor of Science. The degree generally includes units covering physics, mathematics, project management, design and specific topics in civil engineering. Initially such topics cover most, if not all, of the sub-disciplines of civil engineering. Students then choose to specialize in one or more sub-disciplines towards the end of the degree.[13] While an Undergraduate (BEng/BSc) Degree will normally provide successful students with industry accredited qualification, some universities offer postgraduate engineering awards (MEng/MSc) which allow students to further specialise in their particular area of interest within engineering.[14]

In most countries, a Bachelor's degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience and exam requirements) before being certified. Once certified, the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa), Chartered Engineer (in most Commonwealth countries), Chartered Professional Engineer (in Australia and New Zealand), or European Engineer (in much of the European Union). There are international engineering agreements between relevant professional bodies which are designed to allow engineers to practice across international borders.

The advantages of certification vary depending upon location. For example, in the United States and Canada "only a licensed engineer may prepare, sign and seal, and submit engineering plans and drawings to a public authority for approval, or seal engineering work for public and private clients.".[15] This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act.[16] In other countries, no such legislation exists. In Australia, state licensing of engineers is limited to the state of Queensland. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion.[17] In this way, these organizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence.[citation needed] An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.

[edit] Careers

There is no one typical career path for civil engineers. Most engineering graduates start with jobs of low responsibility, and as they prove their competence, they are given more and more responsible tasks, but within each subfield of civil engineering, and even within different segments of the market within each branch, the details of a career path can vary. In some fields and firms, entry-level engineers are put to work primarily monitoring construction in the field, serving as the "eyes and ears" of more senior design engineers; while in other areas, entry-level engineers end up performing the more routine tasks of analysis or design and interpretation. More senior engineers can move into doing more complex analysis or design work, or management of more complex design projects, or management of other engineers, or into specialized consulting, including forensic engineering.

[edit] Sub-disciplines

In general, civil engineering is concerned with the overall interface of human created fixed projects with the greater world. General civil engineers work closely with surveyors and specialized civil engineers to fit and serve fixed projects within their given site, community and terrain by designing grading, drainage, pavement, water supply, sewer service, electric and communications supply, and land divisions. General engineers spend much of their time visiting project sites, developing community consensus, and preparing construction plans. General civil engineering is also referred to as site engineering, a branch of civil engineering that primarily focuses on converting a tract of land from one usage to another. Civil engineers typically apply the principles of geotechnical engineering, structural engineering, environmental engineering, transportation engineering and construction engineering to residential, commercial, industrial and public works projects of all sizes and levels of construction.

[edit] Coastal engineering

Main article: Coastal management

Coastal engineering is concerned with managing coastal areas. In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defence against flooding and erosion. The term coastal defence is the more traditional term, but coastal management has become more popular as the field has expanded to include techniques that allow erosion to claim land

Building construction for several apartment blocks

[edit] Construction engineering

Main article: Construction engineering

Construction engineering involves planning and execution of the designs from transportation, site development, hydraulic, environmental, structural and geotechnical engineers. As construction firms tend to have higher business risk than other types of civil engineering firms, many construction engineers tend to take on a role that is more business-like in nature: drafting and reviewing contracts, evaluating logistical operations, and closely-monitoring prices of necessary supplies.

[edit] Earthquake engineering

Main article: Earthquake engineering

Earthquake engineering covers ability of various structures to withstand hazardous earthquake exposures at the sites of their particular location.

Earthquake-proof and massive pyramid El Castillo, Chichen Itza

Earthquake engineering is a sub discipline of the broader category of Structural engineering. The main objectives of earthquake engineering are:[citation needed]

Snapshot from shake-table video [2] of testing base-isolated (right) and regular (left) building model
  • Understand interaction of structures with the shaky ground.

Earthquake engineering structure does not necessarily mean "extremely strong" or "expensive", e.g., El Castillo pyramid at Chichen Itza shown above.[original research?]

Now, the most powerful and budgetary tool in earthquake engineering is base isolation which pertains to the passive structural vibration control technologies.[citation needed]

[edit] Environmental engineering

Main article: Environmental engineering
A filter bed, a part of sewage treatment

Environmental engineering deals with the treatment of chemical, biological, and/or thermal waste, the purification of water and air, and the remediation of contaminated sites, due to prior waste disposal or accidental contamination. Among the topics covered by environmental engineering are pollutant transport, water purification, waste water treatment, air pollution, solid waste treatment and hazardous waste management. Environmental engineers can be involved with pollution reduction, green engineering, and industrial ecology. Environmental engineering also deals with the gathering of information on the environmental consequences of proposed actions and the assessment of effects of proposed actions for the purpose of assisting society and policy makers in the decision making process.

Environmental engineering is the contemporary term for sanitary engineering, though sanitary engineering traditionally had not included much of the hazardous waste management and environmental remediation work covered by the term environmental engineering. Some other terms in use are public health engineering and environmental health engineering.

[edit] Geotechnical engineering

A slab-on-grade foundation
Main article: Geotechnical engineering

Geotechnical engineering is an area of civil engineering concerned with the rock and soil that civil engineering systems are supported by. Knowledge from the fields of geology, material science and testing, mechanics, and hydraulics are applied by geotechnical engineers to safely and economically design foundations, retaining walls, and similar structures. Environmental concerns in relation to groundwater and waste disposal have spawned a new area of study called geoenvironmental engineering where biology and chemistry are important.[18][19]

Some of the unique difficulties of geotechnical engineering are the result of the variability and properties of soil. Boundary conditions are often well defined in other branches of civil engineering, but with soil, clearly defining these conditions can be impossible. The material properties and behavior of soil are also difficult to predict due to the variability of soil and limited investigation. This contrasts with the relatively well defined material properties of steel and concrete used in other areas of civil engineering. Soil mechanics, which define the behavior of soil, is complex due to stress-dependent material properties such as volume change, stress–strain relationship, and strength.[18]

[edit] Water resources engineering

See also: Hydraulic engineering
See also: Hydrology
Hoover dam

Water resources engineering is concerned with the collection and management of water (as a natural resource). As a discipline it therefore combines hydrology, environmental science, meteorology, geology, conservation, and resource management. This area of civil engineering relates to the prediction and management of both the quality and the quantity of water in both underground (aquifers) and above ground (lakes, rivers, and streams) resources. Water resource engineers analyze and model very small to very large areas of the earth to predict the amount and content of water as it flows into, through, or out of a facility. Although the actual design of the facility may be left to other engineers. Hydraulic engineering is concerned with the flow and conveyance of fluids, principally water. This area of civil engineering is intimately related to the design of pipelines, water distribution systems, drainage facilities (including bridges, dams, channels, culverts, levees, storm sewers), and canals. Hydraulic engineers design these facilities using the concepts of fluid pressure, fluid statics, fluid dynamics, and hydraulics, among others.

[edit] Materials engineering

Main article: Materials science

Another aspect of Civil engineering is materials science. Material engineering deals with ceramics such as concrete, mix asphalt concrete, metals Focus around increased strength, metals such as aluminum and steel, and polymers such as polymethylmethacrylate (PMMA) and carbon fibers.

Materials engineering also consists of protection and prevention like paints and finishes. Alloying is another aspect of material engineering, combining two different types of metals to produce a stronger metal.

[edit] Structural engineering

Main article: Structural engineering
Burj Khalifa, the world's tallest building, in Dubai
Suspension bridge between two brick built towers, over a wooded gorge, showing mud and water at the bottom. In the distance are hills.
Clifton Suspension Bridge, designed by Isambard Kingdom Brunel, in Bristol, UK

Structural engineering is concerned with the structural design and structural analysis of buildings, bridges, towers, flyovers, tunnels, off shore structures like oil and gas fields in the sea, and other structures. This involves identifying the loads which act upon a structure and the forces and stresses which arise within that structure due to those loads, and then designing the structure to successfully support and resist those loads. The loads can be self weight of the structures, other dead load, live loads, moving (wheel) load, wind load, earthquake load, load from temperature change etc. The structural engineer must design structures to be safe for their users and to successfully fulfill the function they are designed for (to be serviceable). Due to the nature of some loading conditions, sub-disciplines within structural engineering have emerged, including wind engineering and earthquake engineering.

Design considerations will include strength, stiffness, and stability of the structure when subjected to loads which may be static, such as furniture or self-weight, or dynamic, such as wind, seismic, crowd or vehicle loads, or transitory, such as temporary construction loads or impact. Other considerations include cost, constructability, safety, aesthetics and sustainability.

[edit] Surveying

Main articles: Surveying and Construction surveying
An all-female surveying crew in Idaho, 1918

Surveying is the process by which a surveyor measures certain dimensions that generally occur on the surface of the Earth. Surveying equipment, such as levels and theodolites, are used for accurate measurement of angular deviation, horizontal, vertical and slope distances. With computerisation, electronic distance measurement (EDM), total stations, GPS surveying and laser scanning have supplemented (and to a large extent supplanted) the traditional optical instruments. This information is crucial to convert the data into a graphical representation of the Earth's surface, in the form of a map. This information is then used by civil engineers, contractors and even realtors to design from, build on, and trade, respectively. Elements of a building or structure must be correctly sized and positioned in relation to each other and to site boundaries and adjacent structures. Although surveying is a distinct profession with separate qualifications and licensing arrangements, civil engineers are trained in the basics of surveying and mapping, as well as geographic information systems. Surveyors may also lay out the routes of railways, tramway tracks, highways, roads, pipelines and streets as well as position other infrastructures, such as harbors, before construction.

Land Surveying

In the United States, Canada, the United Kingdom and most Commonwealth countries land surveying is considered to be a distinct profession. Land surveyors are not considered to be engineers, and have their own professional associations and licencing requirements. The services of a licenced land surveyor are generally required for boundary surveys (to establish the boundaries of a parcel using its legal description) and subdivision plans (a plot or map based on a survey of a parcel of land, with boundary lines drawn inside the larger parcel to indicated the creation of new boundary lines and roads).

Construction Surveying

Construction surveying is generally performed by specialised technicians. Unlike land surveyors, the resulting plan does not have legal status. Construction surveyors perform the following tasks:

  • Survey existing conditions of the future work site, including topography, existing buildings and infrastructure, and even including underground infrastructure whenever possible;
  • Construction surveying (otherwise "lay-out" or "setting-out"): to stake out reference points and markers that will guide the construction of new structures such as roads or buildings for subsequent construction;
  • Verify the location of structures during construction;
  • As-Built surveying: a survey conducted at the end of the construction project to verify that the work authorized was completed to the specifications set on plans.

[edit] Transportation engineering

Main article: Transport engineering

Transportation engineering is concerned with moving people and goods efficiently, safely, and in a manner conducive to a vibrant community. This involves specifying, designing, constructing, and maintaining transportation infrastructure which includes streets, canals, highways, rail systems, airports, ports, and mass transit. It includes areas such as transportation design, transportation planning, traffic engineering, some aspects of urban engineering, queueing theory, pavement engineering, Intelligent Transportation System (ITS), and infrastructure management.

[edit] Municipal or urban engineering

Main article: Urban engineering

Municipal engineering is concerned with municipal infrastructure. This involves specifying, designing, constructing, and maintaining streets, sidewalks, water supply networks, sewers, street lighting, municipal solid waste management and disposal, storage depots for various bulk materials used for maintenance and public works (salt, sand, etc), public parks and bicycle paths. In the case of underground utility networks, it may also include the civil portion (conduits and access chambers) of the local distribution networks of electrical and telecommunications services. It can also include the optimizing of garbage collection and bus service networks. Some of these disciplines overlap with other civil engineering specialties, however municipal engineering focuses on the coordination of these infrastructure networks and services, as they are often built simultaneously, and managed by the same municipal authority.

[edit] See also

Engineering portal
Associations

[edit] References

  1. ^ The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. [1] (accessed: 2007-08-08).
  2. ^ "History and Heritage of Civil Engineering". ASCE. http://live.asce.org/hh/index.mxml?versionChecked=true. Retrieved 2007-08-08.
  3. ^ "Institution of Civil Engineers What is Civil Engineering". ICE. http://www.ice.org.uk/downloads//little_book_full_colour.pdf. Retrieved 2007-09-22.
  4. ^ a b c "What is Civil Engineering?". The Canadian Society for Civil Engineering. http://whatiscivilengineering.csce.ca/civil1.htm. Retrieved 2007-08-08.
  5. ^ a b "Civil engineering". Encyclopædia Britannica. http://www.britannica.com/eb/article-9105844/civil-engineering. Retrieved 2007-08-09.
  6. ^ a b c Oakes, William C.; Leone, Les L.; Gunn, Craig J. (2001), Engineering Your Future, Great Lakes Press, ISBN 1-881018-57-1
  7. ^ The Architecture of the Italian Renaissance Jacob Burckhardt ISBN 0-8052-1082-2
  8. ^ "Institution of Civil Engineers' website". http://www.ice.org. Retrieved 2007-12-26.
  9. ^ "Norwich University Legacy Website"
  10. ^ Griggs, Francis E Jr. "Amos Eaton was Right!". Journal of Professional Issues in Engineering Education and Practice, Vol. 123, No. 1, January 1997, pp. 30–34. See also RPI Timeline
  11. ^ Victor E. Saouma. "Lecture notes in Structural Engineering". University of Colorado. http://ceae.colorado.edu/~saouma/Lecture-Notes/se.pdf. Retrieved 2007-11-02.
  12. ^ Algebra with arithemtic and mensuration by Henry Thomas Colebrook, http://books.google.com/books?id=A3cAAAAAMAAJ&printsec=frontcover&dq=brahmagupta
  13. ^ Various undergraduate degree requirements at MIT, Cal Poly, Queen's and Portsmouth
  14. ^ ,"CITE Postgrad". http://www.uel.ac.uk/cite/programmes/postgraduate/index.htm.
  15. ^ "Why Should You Get Licensed?". National Society of Professional Engineers. http://www.nspe.org/lc1-why.asp. Retrieved 2007-08-11.
  16. ^ "Engineers Act". Quebec Statutes and Regulations (CanLII). http://www.canlii.org/qc/laws/sta/i-9/20050616/whole.html. Retrieved 2007-08-11.
  17. ^ "Ethics Codes and Guidelines". Online Ethics Center. http://onlineethics.org/CMS/profpractice/ethcodes.aspx. Retrieved 2007-08-11.
  18. ^ a b Mitchell, James Kenneth (1993), Fundamentals of Soil Behavior (2nd ed.), John Wiley and Sons, pp 1–2
Posted by at 1 comment:

Hydraulic Radius for Uniform Open Channel Flow

Introduction

One of the parameters needed in order to make use of the Manning equation for open channel flow calculations is the hydraulic radius of the channel cross section. Common shapes for open channel cross section include rectangle, trapezoid, triangle and circle.

The use of hydraulic radius in Manning equation calculations is covered in the first article of this series, 'Introduction to the Manning Equation for Open Channel Flow Calculations' and the hydraulic radius and use of the Manning equation for a circular pipe are covered in 'How to Use the Manning Equation for Storm Sewer Calculations.'

This article will cover rectangle, trapezoid and triangle shapes for an open channel cross section. Hydraulic radius is defined as the cross sectional area of flow divided by the wetted perimeter, so the calculation of rectangle and trapezoid area and triangle area will be included along with the perimeter for each.

Rectangular Cross Section

Rectangular ChannelThe simplest open channel flow cross section for calculation of hydraulic radius is a rectangle. The depth of flow is often represented by the symbol, y, and b is often used for the channel bottom width, as shown in the diagram at the left. From the hydraulic radius definition: RH = A/P, where A is the cross sectional area of flow and P is its wetted perimeter. From the diagram it is clear that A = by and P = 2y + b, so the hydraulic radius is: RH = by/(2y + b) for an open channel flow through a rectangular cross section.

Trapezoidal Cross Section

A trapezoid shape is sometimes used for man made channels and the cross section of natural stream channels are often approximated by a trapezoid area. The diagram at the right shows a trapezoid and the parameters typically used for its shape and size in open channel flow calculations. Those parameters, which are used to calculate the trapezoid area and wetted perimeter, are y, the liquid depth; b, the bottom width; B the width of the liquid surface; λ, the wetted length measured along the sloped side; and α, the angle of the sloped side from vertical. The side slope is usually specified as horiz:vert = z:1.

The cross sectional area of flow is the trapezoid area: A = y(b + B)/2, or Trapezoidal Channel

A = (y/2)(b + b + 2zy), because B = b + 2zy, as can be seen from the diagram.

Simplifying, the trapezoid area is: A = by + zy2.

The wetted perimeter is: P = b + 2λ, but by Pythagoras Theorem:

λ2 = y2 + (yz)2, or λ = [y2 + (yz)2]1/2, so the wetted perimeter is:

P = b + 2y(1 + z2)1/2, and the hydraulic radius for a trapezoid is:

RH = (by + zy2)/[b + 2y(1 + z2)1/2]

Triangular Cross Section

Triangular ChannelA triangular open channel cross section is shown in the diagram at the left. The diagram shows the typical case, where the two sides are sloped at the same angle.There are less parameters needed for the triangule area than for the trapezoid area. The parameters, as shown in the diagram are: B, the surface width of the liquid; λ, the sloped length of the triangle side; y, the liquid depth measured from the vertex of the triangle; and the side slope specification, horiz:vert = z:1.

The triangle area is: A = By/2, but the figure shows that B = 2yz, so the triangle area becomes simply: A = y2z.

The wetted perimeter is: P = 2λ with λ2 = y2 + (yz)2. This simplifies to: P = 2[y2(1 + z2)]1/2

The hydraulic radius is thus: RH = A/P = y2z/{2[y2(1 + z2)]1/2}

About the Author

Dr. Harlan Bengtson is a registered professional engineer with 30 years of university teaching experience in engineering science and civil engineering. He holds a PhD in Chemical Engineering.

Related Reading

Open Channel Flow Measurement 1: Introduction to the Weir and Flume - Open channel flow measurement is usually done with a weir or a flume. The weir or flume causes a change in water depth that correlates with water flow rate. Common open channel flow meters are the sharp crested weir (v notch weir and rectangular weir), broad crested weir, and Parshall flume

Open Channel Flow Basics 2: Supercritical Flow - Supercritical flow is open channel flow with high flow velocity and depth less than critical depth. Subcritical flow has a low flow velocity and depth that is deeper than critical depth. The Froude number will be greater than one for supecritical flow and less than one for subcritical flow.

Uniform Open Channel Flow and the Manning Equation
The Manning equation is widely used for uniform open channel flow calculations with natural or man made channels. The Manning equation is used to relate parameters like river discharge and water flow velocity to hydraulic radius, and open channel slope, size, shape, and Manning roughness.
Posted by at 1 comment:
Subscribe to: Posts (Atom)