Engineering Studies

• Civil engineering involves the design and management of infrastructure such as dams, bridges, roads, and sewerage systems
• Early civil developments


  • The first bridges were logs or vines thrown across streams
  • 6,000 BC - earliest known roads in Jericho are animal paths adapted by humans
  • 4,000 BC earliest constructed roads are stone-paved in Iraq and timber in England
  • 2,000 BC - first water systems using pressured pipes in ancient Greece
  • 1300 BC one of the first stone arch bridges, the Arkadiko Bridge, is built in Greece
  • 600 BC-200 AD - Romans mainly build circular arch bridges of stone
• Middle Ages civil developments

  • Drawbridges and beam bridges begin being built from wood
  • Decline in quality of water from pollution and waste in streets
  • In the 12th century, street paving becomes a respectable trade in Western Europe as cities are seeing a revival
• Middle Ages to present civil developments

  • Mid-1700s - London has over 50 km of water mains made from wood, cast iron, and lead pipes
  • 1797 - first cast iron bridge is built in England
  • 1816 John McAdam revolutionises road design from masonry construction to the use of a thin layer of compacted aggregate to support traffic
  • 1849-reinforced concrete is invented, and steel becomes mass-produced
  • 1883 - Brooklyn bridge in New York is world's first steel-wire suspension bridge
• Benefits of bridges and roads

  • Opens up inaccessible areas for agriculture, mining, and trade
  • Improves the living standards of isolated inhabitants
  • Faster travel - extra infrastructure can reduce congestion and thus limit accidents
  • Bridges provide better defence for towns
  • More economical travel reduces cost of goods and services
• Costs of bridges and roads

  • High initial costs burden taxpayers, whilst toll bridges present an ongoing cost
  • Bridges are prone to use by people contemplating suicide
  • Traffic accidents and roadkill present a threat to life
  • Some bypassed communities lose business, tourists, and facilities
• Benefits of water distribution systems

  • Improved sanitation results in less transmission of disease
  • Sustains human life by providing drinking water and water to cook food in
  • Allows for irrigation of crops and mass production of food
• Costs of water distribution systems

  • Cost of installation and maintenance can be a burden
  • Broad availability may encourage wasteful usage and result in a scarcity of available fresh water
• Early materials used in civil structures

  • Vines and ropes - used for basic suspension
  • Wood - easy to collect, cut, and join, although it is combustible and decays
  • Mud and straw used to make earliest bricks
  • Stone and bricks - high compressive strength (forces easily understood), abundant, easily cut and joined, durable
  • Cement and concrete - developed by Romans to join bricks
• 18th and 19th century materials used in civil structures


  • Cast iron replaced stone and wood for its good compression (although it is prone to fatigue and corrosion), which was then replaced by steel
  • High tensile steel - used in cables for suspension bridges
  • Steel reinforced concrete - used widely in bridges to improve tensile strength
• 20th and 21st century materials used in civil structures

  • More steel varieties, such as stainless steel (which is produced through the addition of chromium)
  • Prestressed concrete
  • Composites such as high strength polymeric concrete
• Early construction processes


  • Timber formwork used to build stone structure such as the pyramids and circular arch bridges
  • Water channels were cut out of stone, brick, rubble, and concrete. The ancient Persians used gravity to distribute the water through slightly sloping tunnels
  • Levers, wedges, and human muscle used to position stone blocks and beams for bridges
• 18th and 19th century construction processes

  • Standardised and prefabricated elements were joined with simple connections in the USA due to the lack of skilled carpenters in the second half of the 18th century
  • Riveting used to join metal members in bridges; later replaced by bolts and welding
  • Thomas Telford's process for road building
  • John McAdam's process for road building
• 20th and 21st century construction processes

  • Modern bridges are constructed using piling rigs to drive concrete piles into the earth
  • Concrete pavers were developed in WWII by the Americans and are used today in road construction
  • Tendons are pretensioned or post-tensioned using hydraulic jacks in order to increase concrete's tensile strength
  • GPS and laser surveying techniques position and align bridge components
  • Robotics is an essential aspect of 'trenchless technology, used today to replace or repair water and sewerage pipes without the need to dig a trench
• Advantages of materials used in civil structures

  • Concrete is made from a near unlimited natural resource
  • Mining of concrete materials has minimal environmental impact
  • Use of composites and advanced materials result in better structure and less materials required
  • Recycled rubber tyres used for retaining walls and in crumbed rubber asphalt to increase its durability
  • Glass can be crushed and added to asphalt to increase the density of pavements and provide improved skid resistance for vehicles
• Disadvantages of materials used in civil structures

  • Use of large quantities of natural resources for civil infrastructure
  • Storage of bridge materials on site can disturb natural environment
  • Materials like hydraulics, oils, greases, bitumen, and paint can pollute
  • Large portions of forest have to be cleared for all major road and damming projects
• Truss basics


  • A truss is a rigid triangular framework of timber or metal members which is used in bridges and other large civil structures to support heavy loads without contributing too much weight
  • In Engineering Studies, we will only be considering two-dimensional representations of trusses, and all external forces acting on the trusses will be static (that is, non-moving) point loads
  • The joints connecting each member in the trusses we are studying can be considered as hinges or pin joints
  • There are three different types of supports which trusses can be mounted upon: roller joints, pin joints, and fixed joints
• Redundant members


  • A redundant member is a slender constituent piece of the truss which is neither in tension nor compression since it sustains no load and is not actually necessary for support
  • There are three cases in which a redundant member can be identified: if a joint connects two members only where the angle between the members is not 180°, if a joint connects two collinear members where one is zero force, or if a joint connects three members where two are collinear
• Zero force member

  • If this joint connects two members only, where the angle between the members is not 180°, then both members are zero force
  • If this joint connects two members only which are collinear and one member is zero force, then the other member must also be zero force
  • If this joint connects three members only and two of the members are collinear, then the third member is zero force
• Compressive force


  If the force solved for is pointing away from the joint in question, then the member which it belongs to is in compression and will therefore point away from the opposite joint as well
• Tensile force


  If the force solved for is pointing towards the joint in question, then the member which this force belongs to is in tension and will therefore point towards the opposite joint as well
• Shear force


  Sliding of one part of a material in one direction, whilst an adjacent part is pushed in the opposite direction
• Bending moment


  The reaction induced in a beam caused by an external shear force acting perpendicular to the beam which results in a bend
• Cantilevered beam


  • Supported at only one end and overhangs
  • Bending moment reaction is generated at the support it does have, which impacts the bending moment diagram
• Drawing shear force diagram and bending moment diagram for a cantilevered beam

  1. Apply the equilibrium of moments to solve for the bending moment at the support

  2. This bending moment does not factor into the shear force diagram
• Uniformly distributed load (UDL)

  • Load of consistent magnitude spread equally across an element like a beam or slab
  • Shear force diagram has angled lines, bending moment diagram has curved lines
• Neutral axis


  • Fibre between the top fibres in compression and the bottom fibres in tension where the stress is zero
  • Further from the neutral axis, the more intense the stress induced
• Shear, compressive, and tensile stress

  • Stress is force per unit area, measured in Pascals
  • Tensile and compressive stress have area measured perpendicular to force
  • Shear stress has area measured parallel to force
• Stress/strain diagram


  Elastic range, proportional limit, yield strength, ultimate tensile strength, breaking strength, toughness, proof stress
• Hooke's law


  Within elastic range, extension is proportional to applied load
• Young's Modulus


  Measure of gradient of straight-line proportion of stress/strain graph, equal to stress divided by strain, in Pascals
• Factor of safety


  Applied to design calculations to increase safety and reduce risk of failure
• Other parts of the graph to understand

  • Ultimate tensile strength (UTS): the maximum stress that can be produced in a material without failure occurring
  • Breaking strength: the point at which a material fails
  • Toughness: how much energy a material can absorb
  • Proof stress: indicates the amount of stress that a metal experiences at a particular point of total strain
• Factor of safety


  How much stronger a system is than it is actually required to be for the conditions it is operating under
• Allowable stress


  The greatest stress load which the structure is allowed to support once the factor of safety is factored in
• Yield strength

  The stress which the structure only just cannot support in actuality
• Ultimate tensile strength


  The stress which the structure only just cannot support in actuality (for brittle materials)
• Tensometer

  Used to stretch a metal sample to breaking point to measure its properties
• Universal testing machine


  Can test both tensile and compressive strength
• Transverse bend/beam testing


  Measures the flexural strength or modulus of rupture (surface stress in a beam at failure) in relatively flexible materials like wood or brittle materials like ceramic