Contents

•1Structural Engineer (Professional)

•2History of Structural Engineering

•3Timeline

•3.1Structural failure

•4Specializations

•4.1Building structures

•4.2Earthquake engineering structures

•4.3Civil engineering structures

•4.4Mechanical structures

•4.5Aerospace structures

•4.6Nanoscale structures

•4.7Structural Engineering for Medical Science

•5Structural elements

•5.1Columns

•5.2Beams

•5.3Trusses

•5.4Plates

•5.5Shells

•5.6Arches

•5.7Catenaries

•5.8Structural engineering theory

•5.9Materials

Structural engineering

Structural engineers are most commonly involved in the nonbuilding structures[1] but they canalso be involved in the design of machinery, medical equipment, vehicles or any item wherestructural integrity affects the item's function or safety. Structural engineers must ensure theirdesigns satisfy given design criteria, predicated on safety (i.e. structures must not collapsewithout due warning) or serviceability and performance (i.e. building sway must not causediscomfort to the occupants).

Structural engineering theory is based upon appliedphysical laws and empirical knowledge ofthe structural performance of different materials and geometries. Structural engineeringdesign utilizes a number of simple structural elements to build complex structural systems.Structural engineers are responsible for making creative and efficient use of funds, structuralelements and materials to achieve these goals.[1]

Structural engineering deals with the making of complex systems like theInternational SpaceStation, seen here from the departing Space ShuttleAtlantis.

Structural Engineer

Structural engineers are responsible for engineering design and analysis. Entry-levelstructural engineers may design the individual structural elements of a structure, for examplethe beams, columns, and floors of a building. More experienced engineers may beresponsible for the structural design and integrity of an entire system, such as a building.

Structural engineers often specialize in particular fields, such as bridge engineering, buildingengineering, pipeline engineering, industrial structures, or special mechanical structures suchas vehicles, ships or aircraft.

Structural engineering has existed since humans first started to construct their own structures.It became a more defined and formalised profession with the emergence ofthearchitecture profession as distinct from the engineering profession during the industrialrevolution in the late 19th century. Until then, the architect and the structural engineer wereusually one and the same - the master builder. Only with the development of specialisedknowledge of structural theories that emerged during the 19th and early 20th centuries did theprofessional structural engineer come into existence.

The role of a structural engineer today involves a significant understanding of both static anddynamic loading, and the structures that are available to resist them. The complexity ofmodern structures often requires a great deal of creativity from the engineer in order toensure the structures support and resist the loads they are subjected to. A structural engineerwill typically have a four or five year undergraduate degree, followed by a minimum of threeyears of professional practice before being considered fully qualified. Structural engineers arelicensed or accredited by different learned societies and regulatory bodies around the world(for example, the Institution of Structural Engineers in the UK). Depending on the degreecourse they have studied and/or the jurisdiction they are seeking licensure in, they may beaccredited (or licensed) as just structural engineers, or as civil engineers, or as both civil andstructural engineers. Another international organisation is IABSE (International Association forBridge and Structural Engineering).[2] The aim of that association is to exchange knowledgeand to advance the practice of structural engineering worldwide in the service of theprofession and society.

Structural engineers investigating NASA's Mars-bound spacecraft, thePhoenix Mars Lander

History of Structural Engineering

Structural engineering dates back to 2700 B.C.E. when the steppyramid for Pharaoh Djoser was built by Imhotep, the first engineer in history known byname. Pyramids were the most common major structures built by ancient civilizationsbecause the structural form of a pyramid is inherently stable and can be almost infinitely

scaled (as opposed to most other structural forms, which cannot be linearly increased in sizein proportion to increased loads).[3]

However, it's important to note that the structural stability of the pyramid is not primarily aresult of its shape. The integrity of the pyramid is intact as long as each of the stones is ableto support the weight of the stone above it.[4] The limestone blocks were taken from a quarrynear the build site. Since the compressive strength of limestone is anywhere from 30 to 250MPa (MPa = Pa * 10^6), the blocks will not fail under compression.[5] Therefore, thestructural strength of the pyramid stems from the material properties of the stones from whichit was built rather than the pyramid's geometry.

Throughout ancient and medieval history most architectural design and construction wascarried out by artisans, such as stone masons and carpenters, rising to the role of masterbuilder. No theory of structures existed, and understanding of how structures stood up wasextremely limited, and based almost entirely on empirical evidence of 'what had workedbefore'. Knowledge was retained by guilds and seldom supplanted by advances. Structureswere repetitive, and increases in scale were incremental.[3]

No record exists of the first calculations of the strength of structural members or the behaviorof structural material, but the profession of structural engineer only really took shape withtheIndustrial Revolution and the re-invention of concrete (see History of Concrete).The physical sciences underlying structural engineering began to be understood inthe Renaissance and have since developed into computer-based applications pioneered inthe 1970s.[6]

Timeline

1452–1519 Leonardo da Vinci made many contributions

•1638: Galileo Galilei published the book "Two New Sciences" in which he examined thefailure of simple structures

Galileo Galilei published the book "Two New Sciences" in which he examined the failure of

simple structures

•1660: Hooke's law by Robert Hooke

•1687: Isaac Newton published "Philosophiae Naturalis Principia Mathematica" whichcontains theNewton's laws of motion

Isaac Newton published "Philosophiae Naturalis Principia Mathematica" which containstheNewton's laws of motion

•1750: Euler–Bernoulli beam equation

•1700–1782:Daniel Bernoulliintroduced the principle of virtual work

•1707–1783:Leonhard Eulerdeveloped the theory of buckling of columns

Leonhard Euler developed the theory of buckling of columns

•1826: Claude-Louis Navier published a treatise on the elastic behaviors of structures

•1873: Carlo Alberto Castigliano presented his dissertation "Intorno ai sistemi elastici", whichcontains his theorem for computing displacement as partial derivative of the strain energy.This theorem includes the method of least work as a special case

•1874: Otto Mohr formalized the idea of a statically indeterminate structure.

•1922: Timoshenko corrects the Euler-Bernoulli beam equation

•1936: Hardy Cross' publication of the moment distribution method, an important innovation inthe design of continuous frames.

•1941: Alexander Hrennikoff solved the discretization of plane elasticity problems using alattice framework

•1942: R. Courant divided a domain into finite subregions

•1956: J. Turner, R. W. Clough, H. C. Martin, and L. J. Topp's paper on the "Stiffness andDeflection of Complex Structures" introduces the name "finite-element method" and is widelyrecognized as the first comprehensive treatment of the method as it is known today

Structural failure

The history of structural engineering contains many collapses and failures. Sometimes this isdue to obvious negligence, as in the case of the Pétionville school collapse, in which Rev.Fortin Augustin "constructed the building all by himself, saying he didn't need an engineer ashe had good knowledge of construction" following a partial collapse of the three-storyschoolhouse that sent neighbors fleeing. The final collapse killed 94 people, mostly children.

In other cases structural failures require careful study, and the results of these inquiries haveresulted in improved practices and greater understanding of the science of structuralengineering. Some such studies are the result of forensic engineering investigations wherethe original engineer seems to have done everything in accordance with the state of theprofession and acceptable practice yet a failure still eventuated. A famous case of structuralknowledge and practice being advanced in this manner can be found in a series of failuresinvolving box girders which collapsed in Australia during the 1970s.

Specializations

Building structures

Structural building engineering includes all structural engineering related to the design ofbuildings. It is the branch of structural engineering that is close toarchitecture.

Structural building engineering is primarily driven by the creative manipulation of materialsand forms and the underlying mathematical and scientific ideas to achieve an end whichfulfills its functional requirements and is structurally safe when subjected to all the loads itcould reasonably be expected to experience. This is subtly different from architectural design,which is driven by the creative manipulation of materials and forms, mass, space, volume,texture and light to achieve an end which is aesthetic, functional and often artistic.

The architect is usually the lead designer on buildings, with a structural engineer employed asa sub-consultant. The degree to which each discipline actually leads the design dependsheavily on the type of structure. Many structures are structurally simple and led byarchitecture, such as multi-storey office buildings and housing, while other structures, suchas tensile structures, shells and gridshells are heavily dependent on their form for theirstrength, and the engineer may have a more significant influence on the form, and hence

much of the aesthetic, than the architect.

The structural design for a building must ensure that the building is able to stand up safely,able to function without excessive deflections or movements which may cause fatigue ofstructural elements, cracking or failure of fixtures, fittings or partitions, or discomfort foroccupants. It must account for movements and forces due to temperature, creep, crackingand imposed loads. It must also ensure that the design is practically buildable withinacceptable manufacturing tolerances of the materials. It must allow the architecture to work,and the building services to fit within the building and function (air conditioning, ventilation,smoke extract, electrics, lighting etc.). The structural design of a modern building can beextremely complex, and often requires a large team to complete.

Structural engineering specialties for buildings include:

•Earthquake engineering

•Façade engineering

•Fire engineering

•Roof engineering

•Tower engineering

•Wind engineering

Earthquake engineering structures

Earthquake engineering structures are those engineered to withstand earthquakes.

Earthquake-proof pyramid El Castillo, Chichen Itza

The main objectives of earthquake engineering are to understand the interactionof structures with the shaking ground, foresee the consequences of possible earthquakes,and design and construct the structures to perform during an earthquake.

Earthquake-proof structures are not necessarily extremely strong like the El Castillo pyramidat Chichen Itza shown above. In fact, many structures considered strong may in fact be stiff,which can result in poor seismic performance.

One important tool of earthquake engineering is base isolation, which allows the base of astructure to move freely with the ground.

Civil engineering structures

Civil structural engineering includes all structural engineering related to the built environment.It includes:

• Bridges• Dams• Earthworks• Foundations• Offshore

structures• Pipelines

• Power stations• Railways• Retaining structures and walls• Roads• Tunnels• Waterways• Water and wastewater

infrastructureThe structural engineer is the lead designer on these structures, and often the sole designer.In the design of structures such as these, structural safety is of paramount importance (in theUK, designs for dams, nuclear power stations and bridges must be signed off by a charteredengineer).

Civil engineering structures are often subjected to very extreme forces, such as largevariations in temperature, dynamic loads such as waves or traffic, or high pressures fromwater or compressed gases. They are also often constructed in corrosive environments, suchas at sea, in industrial facilities or below ground.

Mechanical structures

Principles of structural engineering are applied to variety of mechanical (moveable)structures. The design of static structures assumes they always have the same geometry (infact, so-called static structures can move significantly, and structural engineering design musttake this into account where necessary), but the design of moveable or moving structuresmust account for fatigue, variation in the method in which load is resisted and significantdeflections of structures.

The forces which parts of a machine are subjected to can vary significantly, and can do so ata great rate. The forces which a boat or aircraft are subjected to vary enormously and will doso thousands of times over the structure's lifetime. The structural design must ensure thatsuch structures are able to endure such loading for their entire design life without failing.

These works can require mechanical structural engineering:

•Boilers and pressure vessels

•Coachworks and carriages

•Cranes

•Elevators

•Escalators

•Marine vessels and hulls

Aerospace structures

Aerospace structure types include launch vehicles, (Atlas, Delta, Titan), missiles (ALCM,Harpoon),Hypersonic vehicles (Space Shuttle), military aircraft(F-16, F-18) and commercialaircraft (Boeing 777, MD-11). Aerospace structures typically consist of thin plates withstiffeners for the external surfaces, bulkheads and frames to support the shape and fasteners

such as welds, rivets, screws and bolts to hold the components together.

Nanoscale structures

A nanostructure is an object of intermediate size between molecular and microscopic(micrometer-sized) structures. In describing nanostructures it is necessary to differentiatebetween the number of dimensions on the nanoscale. Nanotextured surfaces have onedimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1and 100 nm.Nanotubes[disambiguation needed] have two dimensions on the nanoscale, i.e.,the diameter of the tube is between 0.1 and 100 nm; its length could be much greater. Finally,spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles(UFP) often are used synonymously although UFP can reach into the micrometre range. Theterm 'nanostructure' is often used when referring to magnetic technology.

Structural Engineering for Medical Science

Medical equipment (also known as armamentarium) is designed to aid in the diagnosis,monitoring or treatment of medical conditions. There are several basictypes: Diagnostic equipment includes medical imaging machines, used to aid in diagnosis ;equipment includes infusion pumps, medical lasers and LASIK surgical machines ; Medicalmonitors allow medical staff to measure a patient's medical state. Monitors may measurepatient vital signs and other parameters including ECG, EEG, blood pressure, and dissolvedgases in the blood ; Diagnostic Medical Equipment may also be used in the home for certainpurposes, e.g. for the control of diabetes mellitus. A biomedical equipment technician (BMET)is a vital component of the healthcare delivery system. Employed primarily by hospitals,BMETs are the people responsible for maintaining a facility's medical equipment.

Structural elements

Any structure is essentially made up of only a small number of different types of elements:

•Columns

•Beams

•Plates

•Arches

•Shells

•Catenaries

Many of these elements can be classified according to form (straight, plane / curve) anddimensionality (one-dimensional / two-dimensional):

One-dimensional Two-dimensional

straight

curve plane curve

(predominantly) bending beamcontinuousarch

plate, concreteslab

lamina,dome

(predominant) tensilestress

rope,tie

Catenary shell

(predominant)compression

pier, column Load-bearing wall

Columns

Columns are elements that carry only axial force - compression - or both axial force andbending (which is technically called a beam-column but practically, just a column). The designof a column must check the axial capacity of the element, and the buckling capacity.

The buckling capacity is the capacity of the element to withstand the propensity to buckle. Itscapacity depends upon its geometry, material, and the effective length of the column, whichdepends upon the restraint conditions at the top and bottom of the column. The effectivelength is where is the real length of the column.

The capacity of a column to carry axial load depends on the degree of bending it is subjectedto, and vice versa. This is represented on an interaction chart and is a complex non-linearrelationship.

Beams

A beam may be defined as an element in which one dimension is much greater than the othertwo and the applied loads are usually normal to the main axis of the element. Beams andcolumns are called line elements and are often represented by simple lines in structuralmodeling.

•cantilevered (supported at one end only with a fixed connection)

•simply supported (supported vertically at each end; horizontally on only one to withstandfriction, and able to rotate at the supports)

•fixed (supported at both ends by fixed connection; unable to rotate at the supports)

•continuous (supported by three or more supports)

•a combination of the above (ex. supported at one end and in the middle)

Beams are elements which carry pure bending only. Bending causes one part of the sectionof a beam (divided along its length) to go into compression and the other part into tension.The compression part must be designed to resist buckling and crushing, while the tensionpart must be able to adequately resist the tension.

Trusses

A truss is a structure comprising two types of structural elements; compression members andtension members (i.e. struts and ties). Most trusses use gusset plates to connect intersectingelements. Gusset plates are relatively flexible and minimizebending moments at theconnections, thus allowing the truss members to carry primarily tension or compression.

Trusses are usually utilised in large-span structures, where it would be uneconomical to usesolid beams.

Plates

Plates carry bending in two directions. A concrete flat slab is an example of a plate. Plates areunderstood by using continuum mechanics, but due to the complexity involved they are mostoften designed using a codified empirical approach, or computer analysis.

They can also be designed with yield line theory, where an assumed collapse mechanism isanalysed to give an upper bound on the collapse load (see Plasticity). This technique is usedin practice [7] but because the method provides an upper-bound, i.e. an unsafe prediction ofthe collapse load, for poorly conceived collapse mechanisms great care is needed to ensurethat the assumed collapse mechanism is realistic.[8]

Shells

Shells derive their strength from their form, and carry forces in compression in two directions.A dome is an example of a shell. They can be designed by making a hanging-chain model,which will act as a catenary in pure tension, and inverting the form to achieve purecompression.

Arches

Arches carry forces in compression in one direction only, which is why it is appropriate to buildarches out of masonry. They are designed by ensuring that the line of thrust of the forceremains within the depth of the arch. It is mainly used to increase the bountifulness of anystructure.

Catenaries

Catenaries derive their strength from their form, and carry transverse forces in pure tensionby deflecting (just as a tightrope will sag when someone walks on it). They are almost alwayscable or fabric structures. A fabric structure acts as a catenary in two directions.

Materials

Structural engineering depends on the knowledge of materials and their properties, in order tounderstand how different materials support and resist loads.

Common structural materials are:

•Iron: Wrought iron, Cast iron

•Concrete: Reinforced concrete, Prestressed concrete

•Alloy: Steel, Stainless steel

•Masonry

•Timber: Hardwood, Softwood

•Aluminium

•Composite materials: Plywood

•Other structural materials:Adobe, Bamboo, Carbon fibre, Fiber reinforced

plastic,Mudbrick, Roofing materials