In dynamical systems instability means that some of the outputs or internal states increase with time, without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior.
61-431: In structural engineering , a structural beam or column can become unstable when excessive compressive load is applied. Beyond a certain threshold, structural deflections magnify stresses , which in turn increases deflections. This can take the form of buckling or crippling. The general field of study is called structural stability . Atmospheric instability is a major component of all weather systems on Earth. In
122-484: A Civil Engineer , but some states require licensure specifically for structural engineering, with experience specific and non-concurrent with experience claimed for another engineering profession. The qualifications for licensure typically include a specified minimum level of practicing experience, as well as the successful completion of a nationally-administered 16-hour exam, and possibly an additional state-specific exam. For instance, California requires that candidates pass
183-443: A chartered engineer ). 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. The forces which parts of a machine are subjected to can vary significantly and can do so at
244-741: 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 tension part must be able to adequately resist the tension. A truss is a structure comprising members and connection points or nodes. When members are connected at nodes and forces are applied at nodes members can act in tension or compression. Members acting in compression are referred to as compression members or struts while members acting in tension are referred to as tension members or ties . Most trusses use gusset plates to connect intersecting elements. Gusset plates are relatively flexible and unable to transfer bending moments . The connection
305-516: A catenary in two directions. 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: Structural engineer Structural engineers analyze, design, plan, and research structural components and structural systems to achieve design goals and ensure
366-708: A four or five-year undergraduate degree, followed by a minimum of three years of professional practice before being considered fully qualified. Structural engineers are licensed 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 degree course they have studied and/or the jurisdiction they are seeking licensure in, they may be accredited (or licensed) as just structural engineers, or as civil engineers, or as both civil and structural engineers. Another international organisation
427-634: 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. These works can require mechanical structural engineering: Aerospace structure types include launch vehicles, ( Atlas , Delta , Titan), missiles (ALCM, Harpoon), Hypersonic vehicles (Space Shuttle), military aircraft (F-16, F-18) and commercial aircraft ( Boeing 777, MD-11). Aerospace structures typically consist of thin plates with stiffeners for
488-439: A master's degree, or two years after receiving a Ph.D. degree. Most US states do not have a separate structural engineering license. In 10 US states, including Alaska, California, Hawaii, Illinois, Nevada, Oregon, Utah, Washington, and others, there is an additional license or authority for Structural Engineering, obtained after the engineer has obtained a Civil Engineering license and practiced an additional amount of time with
549-421: 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
610-494: A national exam, written by the National Council of Examiners for Engineering and Surveying (NCEES), as well as a state-specific exam which includes a seismic portion and a surveying portion. In most states, application for license exam is requires four years of work experience after the candidate graduated from an ABET-accredited university and passing the fundamentals of Engineering exam, three years after receiving
671-407: A number of relatively simple structural concepts to build complex structural systems . Structural engineers are responsible for making creative and efficient use of funds, structural elements and materials to achieve these goals. Structural engineering dates back to 2700 B.C. when the step pyramid for Pharaoh Djoser was built by Imhotep , the first engineer in history known by name. Pyramids were
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#1732781070594732-427: A patient's medical state. Monitors may measure patient vital signs and other parameters including ECG , EEG , blood pressure, and dissolved gases in the blood; diagnostic medical equipment may also be used in the home for certain purposes, 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
793-519: A series of failures involving box girders which collapsed in Australia during the 1970s. 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 ,
854-821: A structural engineer include buildings, towers, stadiums, and bridges. Other structures such as oil rigs, space satellites, aircraft, and ships may also be designed by a structural engineer. Most structural engineers are employed in the construction industry, however, there are also structural engineers in the aerospace, automobile, and shipbuilding industries. In the construction industry, they work closely with architects , civil engineers , mechanical engineers , electrical engineers , quantity surveyors , and construction managers . Structural engineers ensure that buildings and bridges are built to be strong enough and stable enough to resist all appropriate structural loads (e.g., gravity, wind, snow, rain, seismic ( earthquake ), earth pressure, temperature, and traffic) to prevent or reduce
915-479: A structure to move freely with the ground. Civil structural engineering includes all structural engineering related to the built environment. It includes: The 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 the UK, designs for dams, nuclear power stations and bridges must be signed off by
976-453: A subject's postural sway should be altered. Joint stability can be enhanced by the use of an external support system, like a brace, to alter body mechanics. The mechanical support provided by a brace provides cutaneous afferent feedback in maintaining postural control and increasing stability. Structural engineering Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design
1037-461: Is IABSE(International Association for Bridge and Structural Engineering). The aim of that association is to exchange knowledge and to advance the practice of structural engineering worldwide in the service of the profession and society. 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
1098-409: Is a complex non-linear relationship. A beam may be defined as an element in which one dimension is much greater than the other two and the applied loads are usually normal to the main axis of the element. Beams and columns are called line elements and are often represented by simple lines in structural modeling. Beams are elements that carry pure bending only. Bending causes one part of the section of
1159-406: Is a profession subject to licensure. Licensed engineers may receive the title of Professional Engineer, Chartered Engineer, Structural Engineer, or other title depending on the jurisdiction. The process to attain licensure to work as a structural engineer varies by location, but typically specifies university education, work experience, examination, and continuing education to maintain their mastery of
1220-542: Is constructed, and its ability to support the weight of the stone above it. 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 × 10 ). 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. Throughout ancient and medieval history most architectural design and construction were carried out by artisans, such as stonemasons and carpenters, rising to
1281-515: Is equivalent to any of the eigenvalues of the state matrix having either real part greater than zero, or, for the eigenvalues on the imaginary axis, the algebraic multiplicity being larger than the geometric multiplicity. The equivalent condition in discrete time is that at least one of the eigenvalues is greater than 1 in absolute value, or that two or more eigenvalues are equal and of unit absolute value. Fluid instabilities occur in liquids , gases and plasmas , and are often characterized by
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#17327810705941342-418: Is needed to ensure that the assumed collapse mechanism is realistic. 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. Arches carry forces in compression in one direction only, which
1403-738: 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. The structural design for a building must ensure that the building can stand up safely, able to function without excessive deflections or movements which may cause fatigue of structural elements, cracking or failure of fixtures, fittings or partitions, or discomfort for occupants. It must account for movements and forces due to temperature, creep , cracking, and imposed loads. It must also ensure that
1464-416: 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
1525-418: Is usually arranged so that the lines of force in the members are coincident at the joint thus allowing the truss members to act in pure tension or compression. Trusses are usually used in large-span structures, where it would be uneconomical to use solid beams. Plates carry bending in two directions. A concrete flat slab is an example of a plate. Plates are understood by using continuum mechanics , but due to
1586-473: Is why it is appropriate to build arches out of masonry. They are designed by ensuring that the line of thrust of the force remains within the depth of the arch. It is mainly used to increase the bountifulness of any structure. Catenaries derive their strength from their form and carry transverse forces in pure tension by deflecting (just as a tightrope will sag when someone walks on it). They are almost always cable or fabric structures. A fabric structure acts as
1647-521: The construction industry showed that structural engineers in the UK earn an average wage of £35,009. The salary of structural engineers varies from sector to sector within the construction and built environment industry worldwide, depending on the project. For example, structural engineers working in public sector projects earn on average £37,083 per annum compared to the £43,947 average earned by those in commercial projects. Certain regions also represent higher average salaries, with structural engineers in
1708-478: The gravitational potential cause changes in the density that reinforce the original perturbation. Such instabilities usually require that the motions of stars be highly correlated, so that the perturbation is not "smeared out" by random motions. After the instability has run its course, the system is typically "hotter" (the motions are more random) or rounder than before. Instabilities in stellar systems include: The most common residual disability after any sprain in
1769-416: The 'bones and joints' that create the form and shape of human-made structures . Structural engineers also must understand and calculate the stability , strength, rigidity and earthquake-susceptibility of built structures for buildings and nonbuilding structures . The structural designs are integrated with those of other designers such as architects and building services engineer and often supervise
1830-665: The 1970s. The history of structural engineering contains many collapses and failures. Sometimes this is due to obvious negligence, as in the case of the Pétion-Ville school collapse , in which Rev. Fortin Augustin " constructed the building all by himself, saying he didn't need an engineer as he had good knowledge of construction" following a partial collapse of the three-story schoolhouse that sent neighbors fleeing. The final collapse killed 94 people, mostly children. In other cases structural failures require careful study, and
1891-619: The Civil Engineering license. The scope of what structures must be designed by a Structural Engineer, not by a Civil Engineer without the S.E. license, is limited in Alaska, California, Nevada, Oregon, Utah, and Washington to some high importance structures such as stadiums, bridges, hospitals, and schools. The practice of structural engineering is reserved entirely to S.E. licensees in Hawaii and Illinois. The United Kingdom has one of
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1952-927: The United States, there have been discussions in the structural engineering community about the knowledge base of structural engineering graduates. Some have called for a master's degree to be the minimum standard for professional licensing as a civil engineer. There are separate structural engineering undergraduate degrees at the University of California, San Diego and the University of Architecture, Civil Engineering, and Geodesy , Sofia, Bulgaria. Many students who later become structural engineers major in civil, mechanical, or aerospace engineering degree programs, with an emphasis on structural engineering. Architectural engineering programs do offer structural emphases and are often in combined academic departments with civil engineering. In many countries, structural engineering
2013-542: The body is instability. Mechanical instability includes insufficient stabilizing structures and mobility that exceed the physiological limits. Functional instability involves recurrent sprains or a feeling of giving way of the injured joint. Injuries cause proprioceptive deficits and impaired postural control in the joint. Individuals with muscular weakness, occult instability, and decreased postural control are more susceptible to injury than those with better postural control. Instability leads to an increase in postural sway,
2074-409: The column. The effective length is K ∗ l {\displaystyle K*l} where l {\displaystyle l} 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
2135-441: The complexity involved they are most often designed using a codified empirical approach, or computer 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 but because the method provides an upper-bound (i.e. an unsafe prediction of the collapse load) for poorly conceived collapse mechanisms, great care
2196-443: The construction of projects by contractors on site. 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 physical laws and empirical knowledge of the structural performance of different materials and geometries. Structural engineering design uses
2257-602: The design is practically buildable within acceptable 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 be extremely complex and often requires a large team to complete. Structural engineering specialties for buildings include: Earthquake engineering structures are those engineered to withstand earthquakes . The main objectives of earthquake engineering are to understand
2318-481: The design lifetime. The education of structural engineers is usually through a civil engineering bachelor's degree, and often a master's degree specializing in structural engineering. The fundamental core subjects for structural engineering are strength of materials or solid mechanics , structural analysis (static and dynamic), material science and numerical analysis . Reinforced concrete , composite structure , timber, masonry and structural steel designs are
2379-584: The examination result. The candidate can register at the Engineering Council UK as a Chartered Structural Engineer once he or she has been elected as a Chartered Member. Legally it is not necessary to be a member of the IStructE when working on structures in the UK, however, industry practice, insurance, and liabilities dictate that an appropriately qualified engineer be responsible for such work. A 2010 survey of professionals occupying jobs in
2440-429: The external surfaces, bulkheads, and frames to support the shape and fasteners such as welds, rivets, screws, and bolts to hold the components together. A nanostructure is an object of intermediate size between molecular and microscopic (micrometer-sized) structures. In describing nanostructures it is necessary to differentiate between the number of dimensions on the nanoscale. Nanotextured surfaces have one dimension on
2501-648: The general structural design courses that will be introduced in the next level of the education of structural engineering. The structural analysis courses which include structural mechanics , structural dynamics and structural failure analysis are designed to build up the fundamental analysis skills and theories for structural engineering students. At the senior year level or in graduate programs, prestressed concrete design, space frame design for building and aircraft, bridge engineering, civil and aerospace structure rehabilitation and other advanced structural engineering specializations are usually introduced. Recently in
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2562-672: 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. 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 may specialize in particular construction materials such as concrete, steel, wood, masonry, alloys and composites. Structural engineering has existed since humans first started to construct their structures. It became
2623-461: The interaction of 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 pyramid at Chichen Itza shown above. One important tool of earthquake engineering is base isolation , which allows the base of
2684-474: The loss of life or injury. They also design structures to be stiff enough to not deflect or vibrate beyond acceptable limits. Human comfort is an issue that is regularly considered limited. Fatigue is also an important consideration for bridges and aircraft design or for other structures that experience many stress cycles over their lifetimes. Consideration is also given to the durability of materials against possible deterioration which may impair performance over
2745-438: The measurement of the time and distance a subject spends away from an ideal center of pressure . The measurement of a subject's postural sway can be calculated through testing center of pressure (CoP), which is defined as the vertical projection of center of mass on the ground. Investigators have theorized that if injuries to joints cause deafferentation , the interruption of sensory nerve fibers, and functional instability, then
2806-478: The micrometer range. The term 'nanostructure' is often used when referring to magnetic technology. Medical equipment (also known as armamentarium) is designed to aid in the diagnosis, monitoring or treatment of medical conditions. There are several basic types: diagnostic equipment includes medical imaging machines, used to aid in diagnosis; equipment includes infusion pumps, medical lasers, and LASIK surgical machines ; medical monitors allow medical staff to measure
2867-422: 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). The structural stability of the pyramid, whilst primarily gained from its shape, relies also on the strength of the stone from which it
2928-508: The nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes 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 between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) often are used synonymously although UFP can reach into
2989-542: The oldest professional institutions for structural engineers, the Institution of Structural Engineers . Founded as the Concrete Institute in 1908, it was renamed the Institution of Structural Engineers (IStructE) in 1922. It now has 22,000 members with branches in 32 countries. The IStructE is one of several UK professional bodies empowered to grant the title of Chartered Engineer ; its members are granted
3050-411: The people responsible for maintaining a facility's medical equipment. Any structure is essentially made up of only a small number of different types of elements: Many of these elements can be classified according to form (straight, plane / curve) and dimensionality (one-dimensional / two-dimensional): Columns are elements that carry only axial force (compression) or both axial force and bending (which
3111-451: The professional structural engineers come into existence. 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
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#17327810705943172-470: The results of these inquiries have resulted in improved practices and a greater understanding of the science of structural engineering. Some such studies are the result of forensic engineering investigations where the original engineer seems to have done everything in accordance with the state of the profession and acceptable practice yet a failure still eventuated. A famous case of structural knowledge and practice being advanced in this manner can be found in
3233-407: The role of master builder. No theory of structures existed, and understanding of how structures stood up was extremely limited, and based almost entirely on empirical evidence of 'what had worked before' and intuition . Knowledge was retained by guilds and seldom supplanted by advances. Structures were repetitive, and increases in scale were incremental. No record exists of the first calculations of
3294-445: The safety and comfort of users or occupants. Their work takes account mainly of safety, technical, economic, and environmental concerns, but they may also consider aesthetic and social factors. Structural engineering is usually considered a specialty discipline within civil engineering , but it can also be studied in its own right. In the United States, most practicing structural engineers are currently licensed as civil engineers , but
3355-424: The shape that form; they are studied in fluid dynamics and magnetohydrodynamics . Fluid instabilities include: Plasma instabilities can be divided into two general groups (1) hydrodynamic instabilities (2) kinetic instabilities. Plasma instabilities are also categorised into different modes – see this paragraph in plasma stability . Galaxies and star clusters can be unstable, if small perturbations in
3416-476: The situation varies from state to state. Some states have a separate license for structural engineers who are required to design special or high-risk structures such as schools, hospitals, or skyscrapers. In the United Kingdom, most structural engineers in the building industry are members of the Institution of Structural Engineers or the Institution of Civil Engineers . Typical structures designed by
3477-536: The strength of structural members or the behavior of structural material, but the profession of a structural engineer only really took shape with the Industrial Revolution and the re-invention of concrete (see History of Concrete ). The physical sciences underlying structural engineering began to be understood in the Renaissance and have since developed into computer-based applications pioneered in
3538-413: The subject. Professional Engineers bear legal responsibility for their work to ensure the safety and performance of their structures and only practice within the scope of their expertise. In the United States, persons practicing structural engineering must be licensed in each state in which they practice. Licensure to practice as a structural engineer usually be obtained by the same qualifications as for
3599-729: 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, ETABS , Prokon, Revit Structure, Inducta RCB, etc. Such software may also take into consideration environmental loads, such as earthquakes and winds. Structural engineers are responsible for engineering design and structural analysis. Entry-level structural engineers may design
3660-399: The theory of dynamical systems , a state variable in a system is said to be unstable if it evolves without bounds. A system itself is said to be unstable if at least one of its state variables is unstable. In continuous time control theory , a system is unstable if any of the roots of its characteristic equation has real part greater than zero (or if zero is a repeated root). This
3721-495: The title of Chartered Structural Engineer . The overall process to become chartered begins after graduation from a UK MEng degree, or a BEng with an MSc degree. To qualify as a chartered structural engineer, a graduate needs to go through four years of Initial Professional Development followed by a professional review interview. After passing the interview, the candidate sits an eight-hour professional review examination. The election to chartered membership (MIStructE) depends on
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