Structural engineering: Difference between revisions

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[[File:Tour Eiffel Wikimedia Commons.jpg|thumb|upright|The [[Eiffel Tower]] in Paris is a historical achievement of structural engineering.]]

'''Structural engineering''' is a sub-discipline of [[civil engineering]] in which [[structural engineer]]s are trained to design the 'bones and musclesjoints' that create the form and shape of human-made [[Structure#Load-bearing|structures]]. [[Structural engineers]] also must understand and calculate the [[structural stability|stability]], strength, [[structural rigidity|rigidity]] and earthquake-susceptibility of built structures for [[building]]s<ref>[http://www.fao.org/docrep/015/i2433e/i2433e04.pdf FAO online publication] {{webarchive|url=https://web.archive.org/web/20161119191121/http://www.fao.org/docrep/015/i2433e/i2433e04.pdf |date=2016-11-19 }}</ref> and [[nonbuilding structure]]s. The structural designs are integrated with those of other designers such as [[architects]] and [[Building services engineering|building services engineer]] and often supervise the construction of projects by [[contractors]] on site.<ref name = IStructE/> They can also be involved in the design of machinery, medical equipment, and vehicles where structural integrity affects functioning and safety. See [[glossary of structural engineering]].

Structural engineering theory is based upon applied [[physics|physical laws]] and [[empirical]] knowledge of the structural performance of different materials and geometries. Structural engineering design uses a number of relatively simple structural concepts to build complex [[structural system]]s. Structural engineers are responsible for making creative and efficient use of funds, structural elements and materials to achieve these goals.<ref name="IStructE">{{cite web|url = http://www.rmg-engineers.com/what-is-a-structural-engineer/|title = What is a structural engineer|access-date = 2015-11-30|date = 2015-11-30|website = RMG Engineers|url-status = live|archive-url = https://web.archive.org/web/20151208052438/http://www.rmg-engineers.com/what-is-a-structural-engineer/|archive-date = 2015-12-08}}</ref>

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[[File:Pont du Gard BLS.jpg|thumb|[[Pont du Gard]], France, a [[Ancient Rome|Roman]] era aqueduct circa 19 BC]]

Structural engineering dates back to 2700 B.C.E. when the step pyramid for Pharaoh [[Djoser]] was built by [[Imhotep]], the first engineer in history known by name. Pyramids were the most common major structures built by ancient civilizations because 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 size in proportion to increased loads).<ref name = Saouma/>

The structural stability of the pyramid, whilst primarily gained from its shape, relies also on the strength of the stone from which it is constructed, and its ability to support the weight of the stone above it.<ref name=Fonte>{{cite report|title=Building the Great Pyramid in a Year: An Engineer's Report |author=Fonte, Gerard C. A.|publisher=Algora Publishing: New York|pages=34}}CV</ref> The limestone blocks were often taken from a quarry near the building site and have a compressive strength from 30 to 250 MPa (MPa = Pa × 10⁶).<ref>{{cite web|url=http://www.stanford.edu/~tyzhu/Documents/Some%20Useful%20Numbers.pdf|title=Some Useful Numbers on the Engineering Properties of Materials (Geologic and Otherwise)|publisher=Stanford University|access-date=2013-12-05|url-status=dead|archive-url=https://web.archive.org/web/20120616163119/http://www.stanford.edu/~tyzhu/Documents/Some%20Useful%20Numbers.pdf|archive-date=2012-06-16}}</ref> Therefore, the structural strength of the pyramid stems from the material properties of the stones from which it was built rather than the pyramid's geometry.

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[[File:Sir Isaac Newton by Sir Godfrey Kneller, Bt.jpg|thumb|upright| [[Isaac Newton]] published ''[[Philosophiae Naturalis Principia Mathematica]]'', which contains his [[Newton's laws of motion|laws of motion]].]]

[[File:Leonhard Euler 2.jpg|thumb|upright| [[Leonhard Euler]] developed the theory of [[buckling]] of columns.]]

* 1452–1519 [[Leonardo da Vinci]] made many contributions.

* 1638: [[Galileo Galilei]] published the book ''[[Two New Sciences]]'' in which he examined the failure of simple structures.

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* 1941: [[Alexander Hrennikoff]] solved the discretization of plane elasticity problems using a lattice framework.

* 1942: [[Richard 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 and Deflection of Complex Structures" introduces the name "[[finite-element method]]" and is widely recognized as the first comprehensive treatment of the method as it is known today.

===Structural failure===

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[[File:Bolt-in-shear.svg|thumb|Figure of a [[Screw|bolt]] in [[shear stress]]. Top figure illustrates single shear, bottom figure illustrates double shear.]]

Structural engineering depends upon a detailed knowledge of [[applied mechanics]], [[materials science]], and [[applied mathematics]] to understand and predict how structures support and resist self-weight and imposed loads. To apply the knowledge successfully a structural engineer generally requires detailed knowledge of relevant empirical and theoretical [[design codes]], the techniques of [[structural analysis]], as well as some knowledge of the [[corrosion]] resistance of the materials and structures, especially when those structures are exposed to the external environment. Since the 1990s, specialist software has become available to aid in the design of structures, with the functionality to assist in the drawing, analyzing and designing of structures with maximum precision; examples include [[AutoCAD]], StaadPro, [[Computers and Structures|ETABS]], Prokon, Revit Structure, Inducta RCB, etc. Such software may also take into consideration environmental loads, such as earthquakes and winds.{{cn|date=February 2024}}

==Profession==

{{Main|Structural engineer}}

Structural engineers are responsible for engineering design and structural analysis. Entry-level structural engineers may design the individual structural elements of a structure, such as the beams and columns of a building. More experienced engineers may be responsible for the structural design and integrity of an entire system, such as a building.{{cn|date=February 2024}}

Structural engineers often specialize in particular types of structures, such as buildings, bridges, pipelines, industrial, tunnels, vehicles, ships, aircraft, and spacecraft. Structural engineers who specialize in buildings oftenmay specialize in particular construction materials such as concrete, steel, wood, masonry, alloys, and composites,.{{cn|date=February and may focus on particular types of buildings such as offices, schools, hospitals, residential, and so forth.2024}}

Structural engineering has existed since humans first started to construct their structures. It became a more defined and formalized profession with the emergence of architecture as a distinct profession from engineering during the industrial revolution in the late 19th century. Until then, the architect and the structural engineer were usually one and the same thing – the master builder. Only with the development of specialized knowledge of structural theories that emerged during the 19th and early 20th centuries, did the professional structural engineers come into existence.{{cn|date=February 2024}}

The role of a structural engineer today involves a significant understanding of both static and dynamic loading and the structures that are available to resist them. The complexity of modern structures often requires a great deal of creativity from the engineer in order to ensure the structures support and resist the loads they are subjected to. A structural engineer will typically have a four or five-year undergraduate degree, followed by a minimum of three years of professional practice before being considered fully qualified.

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[[File:Burjdubaiaug92007.jpg|thumb|upright|[[Burj Khalifa]], in [[Dubai]], the [[world's tallest building]], shown under construction in 2007 (since completed)]]

Structural building engineering includes all structural engineering related to the design of buildings. It is a branch of structural engineering closely affiliated with [[architecture]].

Structural building engineering is primarily driven by the creative manipulation of materials and forms and the underlying mathematical and scientific ideas to achieve an end that fulfills its functional requirements and is structurally safe when subjected to all the loads it could 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.

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

===Mechanical structures===

The principles of structural engineering apply to a variety of mechanical (moveable) structures. The design of static structures assumes they always have the same geometry (in fact, so-called static structures can move significantly, and structural engineering design must take this into account where necessary), but the design of moveable or moving structures must account for [[Fatigue (material)|fatigue]], variation in the method in which load is resisted and significant deflections of structures.

===Mechanical engineering structures===

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

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==Structural elements==

{{main|SpaceStructural frameelement}}

[[File:Bending.svg|thumb|right|A [[statically determinate]] simply supported beam, bending under an evenly distributed load]]

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===Columns===

{{Main|Column}}

Columns are elements that carry only axial force (compression) or both axial force and bending (which is technically called a beam-column but practically, just a column). The design of 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. Its capacity depends upon its geometry, material, and the effective length of the column, which depends upon the restraint conditions at the top and bottom of the column. The effective length is <math>K*l</math> where <math>l</math> is the real length of the column and K is the factor dependent on the restraint conditions.

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

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{{Main|Plate (structure)}}

Plates carry bending in two directions. A concrete flat slab is an example of a plate. PlatesPlate arebehavior understoodis bybased usingon [[continuum mechanics]], but. dueDue to the complexity involved they are most often designedanalyzed using a codifiedfinite empirical approach, or computerelement analysis.

They can also be designed with yield line theory, where an assumed collapse mechanism is analyzed to give an upper bound on the collapse load. This technique is used in practice<ref>{{cite web |title=Assessment of a Pair of Reinforced Concrete Roof Slabs |url=http://www.ramsay-maunder.co.uk/downloads/precast_roof_slabs.pdf |website=Ramsay-Maunder.co.uk |publisher=Ramsay Maunder Associates |date=2011 |access-date=2022-03-08 }}</ref> but because the method provides an upper-bound (i.e. an unsafe prediction of the collapse load) for poorly conceived collapse mechanisms, great care is needed to ensure that the assumed collapse mechanism is realistic.<ref>{{cite web |url=http://www.ramsay-maunder.co.uk/downloads/l_shaped_landing.pdf |title=Reappraisal of a Simply Supported Landing Slab |website=Ramsay-Maunder.co.uk |publisher=Ramsay Maunder Associates |url-status=live |archive-url=https://web.archive.org/web/20160304071038/http://www.ramsay-maunder.co.uk/downloads/l_shaped_landing.pdf |date=2011 |archive-date=2016-03-04 |access-date=2022-03-08 }}</ref>

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===Shells===

{{Main|Thin-shell structure}}

{{See also|Gridshell|Space frame}}

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 pure compression.

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{{Main|Structural material}}

Structural engineering depends on the knowledge of materials and their properties, in order to understand how different materials support and resist loads. It also involves a knowledge of [[Corrosion engineering]] to avoid for example galvanic coupling of dissimilar materials.

Common structural materials are:

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* [[List of bridge disasters]]

* [[List of structural engineers]]

* [[List of structural engineering software]]

* [[Mechanical engineering]]

* [[Nanostructure]]

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==References==

* Hibbeler, R. C. (2010). ''Structural Analysis''. Prentice-Hall.

* Blank, Alan; McEvoy, Michael; Plank, Roger (1993). ''Architecture and Construction in Steel''. Taylor & Francis. {{ISBN|0-419-17660-8}}.

* Hewson, Nigel R. (2003). ''Prestressed Concrete Bridges: Design and Construction''. Thomas Telford. {{ISBN|0-7277-2774-5}}.