Saturday, March 27, 2010

civil engineering profession

新japaneseoldman乱Civil engineering is a professional engineering disciplinethat deals with the design, construction and maintenance of the physicaland naturally built environment, including works such as bridges, roads, canals, dams and buildings.[1][2][3]Civil engineering is the oldest engineeringdiscipline after military engineering,[4]and it was defined to distinguish non-military engineering frommilitary engineering.[5]It is traditionally broken into several sub-disciplines including environmental engineering, geotechnical engineering, structural engineering, transportationengineering, 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 frommunicipal through to federal levels, and in the private sector fromindividual homeowners through to international companies.[citation needed]

[edit]History of the civilengineering profession

新japaneseoldman乱Engineering has been an aspect of life since thebeginnings of human existence. The earliest practices of Civilengineering may have commenced between 4000 and 2000 BC in AncientEgypt and Mesopotamia when humans started to abandon a nomadicexistence, thus causing a need for the construction of shelter. Duringthis time, transportation became increasingly importantleading to the development of the wheel and sailing. The construction of Pyramids in Egypt (circa 2700-2500 BC) might be consideredthe first instances of large structure constructions. Other ancienthistoric civil engineering constructions include the Parthenonby Iktinosin Ancient Greece (447-438 BC), the AppianWay by Roman engineers (c. 312 BC), the Great Wall of China by General MengT'ien under orders from Ch'in Emperor ShihHuang Ti (c. 220 BC)[6]and the stupas constructed in ancient SriLanka like the Jetavanaramaya and the extensive irrigationworks in Anuradhapura. The Romans developed civilstructures throughout their empire, including especially aqueducts, insulae, harbours, bridges,dams and roads.

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

The Archimedes screw wasoperated by hand and could raise water efficiently.

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

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

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

The first private college to teach Civil Engineering in the UnitedStates was Norwich University founded in 1819 byCaptain Alden Partridge.[9].The first degree in Civil Engineering in the United States was awardedby Rensselaer PolytechnicInstitute 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 scienceof civil engineering

Pontdu Gard, France, a Romanaqueduct built circa 19 BC.

Civil engineering is the application of physical and scientificprinciples, and its history is intricately linked to advances inunderstanding of physics and mathematicsthroughout history. Because civil engineering is a wide rangingprofession, including several separate specialized sub-disciplines, itshistory is linked to knowledge of structures, materials science, geography,geology,soils, hydrology,environment, mechanicsand other fields.

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

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

[edit] The civil engineer

[edit] Education and licensure

The Institution of Civil Engineersheadquarters in London

Civil engineers typically possess an academic degree with a major in civil engineering. Thelength of study for such a degree is usually three to five years and thecompleted degree is usually designated as a Bachelor of Engineering, though someuniversities designate the degree as a Bachelor of Science. The degree generally includes unitscovering physics,mathematics,project management, design andspecific topics in civil engineering. Initially such topics cover most,if not all, of the sub-disciplines of civil engineering. Students thenchoose to specialize in one or more sub-disciplines towards the end ofthe degree.[13]While an Undergraduate (BEng/BSc) Degree will normally providesuccessful students with industry accredited qualification, someuniversities offer postgraduate engineering awards (MEng/MSc) whichallow students to further specialise in their particular area ofinterest within engineering.[14]

In most countries, a Bachelor's degree in engineering represents thefirst step towards professional certification andthe degree program itself is certified by a professional body.After completing a certified degree program the engineer must satisfy arange of requirements (including work experience and exam requirements)before being certified. Once certified, the engineer is designated thetitle of Professional Engineer (in the UnitedStates, Canada and South Africa), Chartered Engineer (in most Commonwealthcountries), CharteredProfessional Engineer (in Australiaand New Zealand), or European Engineer (in much of the European Union). There are international engineeringagreements between relevant professional bodies which are designed toallow engineers to practice across international borders.

The advantages of certification vary depending upon location. Forexample, in the United States and Canada "only a licensed engineer mayprepare, sign and seal, and submit engineering plans and drawings to apublic authority for approval, or seal engineering work for public andprivate clients.".[15]This requirement is enforced by state and provincial legislation suchas Quebec'sEngineers Act.[16]In other countries, no such legislation exists. In Australia, statelicensing of engineers is limited to the state of Queensland.Practically all certifying bodies maintain a code of ethics that they expect allmembers to abide by or risk expulsion.[17]In this way, these organizations play an important role in maintainingethical standards for the profession. Even in jurisdictions wherecertification has little or no legal bearing on work, engineers aresubject to contract law. In caseswhere an engineer's work fails he or she may be subject to the tortof negligence and, in extreme cases, the charge of criminal negligence.[citation needed] Anengineer's work must also comply with numerous other rules andregulations such as building codes and legislation pertainingto environmental law.

[edit] Careers

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

[edit] Sub-disciplines

In general, civil engineering is concerned with the overall interfaceof human created fixed projects with the greater world. General civilengineers work closely with surveyors and specialized civil engineers tofit and serve fixed projects within their given site, community andterrain by designing grading, drainage, pavement, watersupply, sewer service, electric and communications supply, and landdivisions. General engineers spend much of their time visiting projectsites, developing community consensus, and preparing construction plans.General civil engineering is also referred to as siteengineering, a branch of civil engineering that primarily focuses onconverting a tract of land from one usage to another. Civil engineerstypically apply the principles of geotechnical engineering, structuralengineering, environmental engineering, transportation engineering andconstruction engineering to residential, commercial, industrial andpublic works projects of all sizes and levels of construction.

[edit] Coastal engineering

Coastal engineering is concerned with managing coastal areas. In somejurisdictions the terms sea defense and coastal protection are used tomean, respectively, defence against flooding and erosion. The termcoastal defence is the more traditional term, but coastal management hasbecome more popular as the field has expanded to include techniquesthat allow erosion to claim land

Building construction for several apartment blocks

[edit] Constructionengineering

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

[edit] Earthquake engineering

Earthquake engineering covers ability of various structures towithstand hazardous earthquake exposures at the sites of theirparticular location.

Earthquake-proof and massive pyramid El Castillo, Chichen Itza

Earthquake engineering is a subdiscipline of the broader category of Structural engineering. The mainobjectives of earthquake engineering are:[citation needed]

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

Earthquake engineering structure does not necessarily mean "extremelystrong" or "expensive", e.g., El Castillo pyramid at Chichen Itza shownabove.[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] Environmentalengineering

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, andthe remediation of contaminated sites,due to prior waste disposal or accidental contamination. Among thetopics covered by environmental engineering are pollutant transport, water purification, waste water treatment, airpollution, solidwaste treatment and hazardous waste management. Environmental engineers can be involved withpollution reduction, green engineering, and industrial ecology. Environmental engineering also dealswith the gathering of information on the environmental consequences ofproposed actions and the assessment of effects of proposed actions forthe purpose of assisting society and policy makers in the decisionmaking process.

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

[edit] Geotechnicalengineering

Geotechnical engineering is an area of civil engineering concernedwith the rock and soil thatcivil engineering systems are supported by. Knowledge from the fields ofgeology,material science and testing, mechanics,and hydraulics are applied by geotechnical engineersto safely and economically design foundations, retaining walls, and similar structures. Environmentalconcerns in relation to groundwaterand wastedisposal have spawned a new area of study called geoenvironmentalengineering where biology and chemistryare important.[18][19]

Some of the unique difficulties of geotechnical engineering are theresult of the variability and properties of soil. Boundary conditions are often welldefined in other branches of civil engineering, but with soil, clearlydefining these conditions can be impossible. The material properties andbehavior of soil are also difficult to predict due to the variabilityof soil and limited investigation. This contrastswith the relatively well defined material properties of steel and concreteused in other areas of civil engineering. Soil mechanics, which define the behavior of soil, iscomplex due to stress-dependent material propertiessuch as volume change, stress–strain relationship, and strength.[18]

[edit] Water resourcesengineering

Water resources engineering is concerned with the collection andmanagement 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 engineeringrelates to the prediction and management of both the quality and thequantity of water in both underground (aquifers) and above ground (lakes, rivers, andstreams) resources. Water resource engineers analyze and model verysmall to very large areas of the earth to predict the amount and contentof water as it flows into, through, or out of a facility. Although theactual design of the facility may be left to other engineers. Hydraulicengineering is concerned with the flow and conveyance of fluids,principally water. This area of civil engineering is intimately relatedto the design of pipelines, water distribution systems, drainage facilities(including bridges, dams, channels, culverts,levees, storm sewers), and canals. Hydraulic engineersdesign these facilities using the concepts of fluid pressure, fluidstatics, fluid dynamics, and hydraulics,among others.

[edit] Materials engineering

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

Materials engineering also consists of protection and prevention likepaints and finishes. Alloying is another aspect of materialengineering, combining two different types of metals to produce astronger metal.

[edit] Structural engineering

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 theforces and stresses which arise within that structure due to thoseloads, and then designing the structure to successfully support andresist those loads. The loads can be self weight of the structures,other dead load, live loads, moving (wheel) load, wind load, earthquakeload, load from temperature change etc. The structural engineer mustdesign structures to be safe for their users and to successfully fulfillthe function they are designed for (to be serviceable). Due tothe nature of some loading conditions, sub-disciplines within structuralengineering have emerged, including wind engineering and earthquake engineering.

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

[edit] Surveying

An all-female surveying crew in Idaho, 1918

Surveying is the process by which a surveyor measures certaindimensions that generally occur on the surface of the Earth. Surveyingequipment, such as levels and theodolites, are used for accuratemeasurement of angular deviation, horizontal, vertical and slopedistances. With computerisation, electronic distance measurement (EDM),total stations, GPS surveying and laser scanning have supplemented (andto a large extent supplanted) the traditional optical instruments. Thisinformation is crucial to convert the data into a graphicalrepresentation of the Earth's surface, in the form of a map. Thisinformation is then used by civil engineers, contractors and evenrealtors to design from, build on, and trade, respectively. Elements of abuilding or structure must be correctly sized and positioned inrelation to each other and to site boundaries and adjacent structures.Although surveying is a distinct profession with separate qualificationsand licensing arrangements, civil engineers are trained in the basicsof 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 mostCommonwealth countries land surveying is considered to be a distinctprofession. Land surveyors are not considered to be engineers,and have their own professional associations and licencingrequirements. The services of a licenced land surveyor are generallyrequired for boundary surveys (to establish the boundaries of a parcelusing its legal description) and subdivision plans (a plot or map basedon a survey of a parcel of land, with boundary lines drawn inside thelarger parcel to indicated the creation of new boundary lines androads).

Construction Surveying

Construction surveying is generally performed by specialisedtechnicians. Unlike land surveyors, the resulting plan does not havelegal status. Construction surveyors perform the following tasks:

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

[edit] Transportationengineering

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

[edit] Municipal orurban engineering

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

[edit] See also

Associations

[edit] References

  1. ^The American Heritage Dictionary of the English Language, FourthEdition. Houghton Mifflin Company, 2004. [1] (accessed:2007-08-08).
  2. ^"History and Heritage of CivilEngineering". ASCE. http://live.asce.org/hh/index.mxml?versionChecked=true. Retrieved 2007-08-08.
  3. ^"Institution of Civil EngineersWhat is Civil Engineering". ICE. http://www.ice.org.uk/downloads//little_book_full_colour.pdf. Retrieved 2007-09-22.
  4. ^ abc"What is Civil Engineering?". TheCanadian Society for Civil Engineering.http://whatiscivilengineering.csce.ca/civil1.htm. Retrieved 2007-08-08.
  5. ^ ab"Civil engineering". Encyclop?diaBritannica. http://www.britannica.com/eb/article-9105844/civil-engineering. Retrieved 2007-08-09.
  6. ^ abcOakes, WilliamC.; Leone, Les L.; Gunn, Craig J. (2001), Engineering Your Future,Great Lakes Press, ISBN 1-881018-57-1
  7. ^The Architecture of the ItalianRenaissance 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 ofProfessional 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 StructuralEngineering". 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". QuebecStatutes and Regulations (CanLII). http://www.canlii.org/qc/laws/sta/i-9/20050616/whole.html. Retrieved 2007-08-11.
  17. ^"Ethics Codes and Guidelines". OnlineEthics Center. http://onlineethics.org/CMS/profpractice/ethcodes.aspx. Retrieved 2007-08-11.
  18. ^ abMitchell, James Kenneth (1993), Fundamentals of Soil Behavior (2nded.), John Wiley and Sons, pp 1–2

Hydraulic Radius for Uniform Open Channel Flow

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One of the parametersneeded in order to make use of the Manning equation for open channelflow 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 inManning equation calculations is covered in the first article of thisseries, 'Introduction to the Manning Equation for Open ChannelFlow Calculations' and the hydraulic radius and use of the Manningequation for a circular pipe are covered in 'How to Use the Manning Equation for Storm SewerCalculations.'

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

新japaneseoldman乱

Rectangular ChannelThesimplest open channel flow cross section for calculation of hydraulicradius is a rectangle. The depth of flow is often represented by thesymbol, y, and b is often used for the channel bottom width, as shown inthe 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 wettedperimeter. From the diagram it is clear that A = by and P = 2y + b, sothe hydraulic radius is: RH = by/(2y + b) for an open channelflow through a rectangular cross section.

新japaneseoldman乱

A trapezoid shape issometimes used for man made channels and the cross section of naturalstream channels are often approximated by a trapezoid area. The diagramat the right shows a trapezoid and the parameters typically used for itsshape and size in open channel flow calculations. Those parameters,which are used to calculate the trapezoid area and wetted perimeter, arey, the liquid depth; b, the bottom width; B the width of the liquidsurface; λ, the wetted length measured along the sloped side; and α, theangle of the sloped side from vertical. The side slope is usuallyspecified as horiz:vert = z:1.

The cross sectional area of flowis 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 thediagram.

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

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

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

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

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

TriangularCross Section

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

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

The wettedperimeter 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}

Aboutthe Author

Dr. Harlan Bengtson is aregistered professional engineer with 30 years of university teachingexperience in engineering science and civilengineering. He holds a PhD in Chemical Engineering.

RelatedReading

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

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