The first is the North Queensferry Lighthouse. The North Queensferry Lighthouse is the smallest building in the world. This is a lighthouse in Scotland. Established in 18 17. The lighthouse is only 1 1 foot high and can only accommodate two people. Although the area is small, it has various functions. This lighthouse used to be a lighthouse for ships to sail.
The second building is Portland Steel Building. The steel structure building is located at the triangle intersection in downtown Portland, Oregon, USA. This building was built in 19 16, covering an area of less than one acre. Even today, it is a commercial building. It is protected by the national historical site registration, so it needs maintenance and painting every few years. It looks like new.
The last building is Turin Primary School. Turin Primary School, located in Turin, Italy, is the smallest school in Italy. There is only one student in the teaching building, but there are 15 staff. This student can be said to have a good allocation of resources.
2. Portland lighthouse introduction pictures
A lighthouse is a high-rise building structure, or contains a lighthouse, which is used to guide ships at sea. Lighthouse has a similar meaning: the top of a volcano; In ancient times, sailors led sailors to find that they were built on the top of the mountain by fire. Due to the quality of modern equipment and products, the lighthouse was built on the top of the mountain and launched into the water. There are eight beautiful lighthouses in the world.
1- Coquille River Lighthouse in Oregon, USA
2- Prince Edward Island-Covehead Harbor Lighthouse, Canada
3- North Wales Coastal Lighting Lighthouse
Portland headlights, Cape Elizabeth, Maine
5- Kibei Wharf Lighthouse is a typical red tower in Lake Michigan.
Lighthouse in Havana harbor, Cuba
7- Aquinas Lighthouse on the central coast of Oregon
8- Ethanol Point Lighthouse-Elliot Bay at the south entrance of Seattle.
3. Portland attractions
About 278 kilometers.
It usually takes only three hours to drive there. Portland is the largest rose city in America. It is a city in the northwest of the United States next to Seattle. Because of its maritime climate, the climate in Portland, USA is very suitable for growing roses, which is why Portland is called the City of Roses.
Since the distance between Seattle and Portland is only a few hours, tourists from all over the world will include Portland in their travel plans. This is also the reason why Portland's American tourism industry has always been at the forefront of the United States.
Portland and Seattle (villa) can be said to be the two most important cities in the northwest of the United States. Their economy has developed rapidly and they have always been in a leading position in tourism. So many tourists travel to Seattle and Portland. And the distance between Seattle and Portland is not particularly far. Many people who come to Seattle will go to Portland to enjoy its unique rose scenery.
Seattle is a very beautiful low-altitude city. It is this special geographical environment that makes Seattle's ancient glaciers and active volcanoes complement each other. Seattle has beautiful green hills and lakes, and the climate here is extremely humid and pleasant, with almost four seasons like spring. Such scenery is hard to see in the United States or other places, and it is also an incredible place in Seattle.
4. Introduction of tourist attractions in Portland
At the mouth of the wide Columbia River, we enjoyed the Pacific Ocean. (Diary of Lewis and Crabbe) This is also the first time that the US government has completed its expedition to the Pacific Ocean. )
The beauty of Oregon is not limited to downtown Portland. During this trip to the northwest of the United States, I was deeply impressed by the waterfall scenery along the Columbia Canyon, which amazed me. Another nickname for Colombia is the Great River, the West River or the Oregon River. It is also the longest river in the Pacific Northwest of North America, with a total length of more than 2,000 kilometers, ranking fourth among American rivers. The main highway along the Columbia River is Highway 84, but Highway 30 parallel to this highway is the famous Guanpu Highway. This trip with Bao Shu took us nearly a day to see six waterfalls and two scenic spots (one for you to see Columbia Canyon and the other for you to see Mount Hood), which made us remember the Columbia Canyon vividly. There are eight scenic spots from east to west here. At the end of the article, I will share other pearls that I don't have, because I didn't have a chance to see my tree treasure.
5. Kingsport Lighthouse
Robert Pattinson, born in May 1986 in London, England, is an English actor.
In 2004, Robert Pattinson played a supporting role in the TV movie The Ring of Nibelungen. In 2005, he played cedric diggory in the film Harry Potter and the Goblet of Fire. Since 2008, he has played the vampire edward cullen in the film Twilight. 20 10 Robert Pattinson starred in his first producer film, Remember Me. 20 1 1 year, his cooperative work "Tears of Elephants" with reese witherspoon was released. In 20 12, bel ami, which he collaborated with uma thurman, and Metropolis, which was directed by david cronenberg, were released one after another.
20 15 starred in the movie "the desert queen". 20 16 starred in the movie "Lost in Z City". Starring in the movie "Good Times". In 2000, he was the guest of the 75th Golden Globe Awards. In 2005, she starred in the film "The Lighthouse". In 2005, she starred in the film Tenet. On September 4th, 2008, Robert Pattinson was diagnosed as COVID-19 positive.
6. Appearance of Portland Lighthouse
Structural engineering is the pillar of human civilization. The earliest structure of human beings was probably to build nests and holes under natural conditions, and later it developed into building houses for itself. As early as 3,000 years ago in China, the book Zhou Li recorded the shapes of various buildings. In the Han Dynasty, Wang Yanshou's Kao Gong Ji said, so we checked its architecture and structure. Special structural terms have emerged.
With the development of human civilization, there are more and more structures built by human beings, and they are becoming more and more complicated. Behind the building structure are roads and bridges, vehicles and boats, water conservancy, machinery, aircraft, rockets, weapons, chemical equipment, power transmission and other structures.
The temple of the goddess of Athens in the Acropolis was built in 438. C this is a typical example of ancient Greek architecture.
With the diversification and complexity of structural types, the concept of structure is also expanding. At present, the so-called structure refers to all the solid components and objects in its system that can bear a certain load. In a broader sense, all solid components and natural objects of the system that bear a certain load, such as roots, stems and leaves of plants, bones, blood vessels, crust and rock masses of animals, can also be regarded as structures.
The development of structure is closely related to structural materials and structural mechanics. The former can be regarded as the hardware of structural engineering, while the latter can be regarded as the software developed by structural engineering.
Whether in the east or the west, before steel and concrete were used as the main building materials, stones, wood and bricks were used as building materials for the longest time. Specifically, the West uses stones as building materials, while China and other eastern countries use bricks and wood as building materials. The wood structure is neither fire-resistant nor corrosion-resistant, so the ancient buildings in China have a long history.
Sakyamuni Tower of Yingfo Palace Temple in the County (A.D. 1056)
1774, the British engineer J. Smeaton used lime when building a lighthouse at sea. It is very effective to use clay sand mixture as foundation. 1824, British stonemason J. Aspdim (1779-1885) obtained a patent for burning cement, which is called Portland cement because it is very similar to the local stones in Portland. The cement plant was established in France on 1840 and in Germany on 1855 respectively. 1970, everyone in the world uses 156 kg of cement every year.
/kloc-After the middle of the 0/9th century, steel-making technology became popular, so steel was widely used in structures. 1859, Britain built the world's first steel ship. 1846, Britain built the Brittany Railway Bridge in North Wales (1846, iron pipe). 1873, Albert suspension bridge across the Thames was built in England, with a maximum span of 384 feet.
Brittany Bridge (1846, iron pipe)
After cement, steel and other modern materials. For human beings, the form and speed of structure are complex.
Structural mechanics has always been the theoretical basis of structural design. It is based on classical mechanics, elastic mechanics, plastic mechanics, elastic body vibration and wave theory and elastic body equilibrium stability theory.
/kloc-structural mechanics research before 0/9th century
In the history of structural mechanics research, the earliest research is statics, because in the era when masonry and wood are the main structural materials, the main problem encountered is structural balance. Later, it developed into a study of strength.
The earliest structural element studied by human beings is beam. Leonardo da vinci studied and discussed the load that a column can bear in his manuscript. Galileo mentioned and investigated the bearing capacity of fixed-end cantilever beam in Luling Photoelectricity Fu (1638). The coefficients of Galileo's results obtained by Eddm and Edm Edme Mariotte are incorrect, because their cross-sectional equilibrium conditions are incorrect. Jacob Bernoulli (1654- 1705) studied the S-shaped beam theory now known as Bernoulli.
The second important element of structural mechanics. Gustav robert kirchhoff (1824- 1887) published an important paper on the plate problem in 1850, which corrected the previous mistakes about the boundary conditions of the plate problem. Kirchhoff deduces the boundary conditions of the plate by using the virtual displacement principle, and points out that only two boundary conditions are needed to solve the plate problem. He correctly solved the vibration problem of a circular plate. When establishing the equation of the plate problem, he assumed that:
The straight line perpendicular to the middle plane during deformation keeps a straight line, and it is also perpendicular to the middle plane after deformation;
Elements in a surface do not stretch when deformed.
This hypothesis of simplifying plate problems is still used today, and it is called straight normal hypothesis, also known as Kirchhoff hypothesis. 1888, the Englishman Augustus Edward Hofrov (1863- 1940) deduced the equilibrium equation of elastic thin shells by using Kirchhoff hypothesis. So far, this hypothesis is called Kirchhoff-Love Hypothesis.
The actual engineering structure is often not a single component, but a complex component system. Early precision solid mechanics was studied on a single component, such as the bending of beams and the torsion of columns. Later, with the development of modern industry, it is more and more necessary to study complex structural systems. When the early statics was mature, there was a study of multi-component static equilibrium. Now, with the help of deformation mechanics, the multi-component internal force and deformation analysis of deformed solids are naturally put on the agenda.
The content of structural mechanics is very extensive, such as suspension bridge, arch, truss, beam, elastic foundation, retaining wall and so on. His application involves railway, highway, shipbuilding, machinery, water conservancy and other engineering departments. Therefore, with the development of modern industry, its content is gradually enriched.
1. continuous beam theory
Naville was the first scholar who really studied continuous beams. In his paper 1825, he first gave a three-moment equation to deal with this problem. But not anymore. The current form of the real three-moment equation was put forward by Claperon (1799- 1864) when he rebuilt a bridge near Paris in 1849, and it was not published as a paper until 1857. In 1855, Tao Bo's paper first mentioned the three-moment equation.
2. Maxwell and his research on trusses.
In 1864, Maxwell summarized his general conclusions about truss research. He has been able to distinguish between statically indeterminate truss and statically indeterminate truss. For statically indeterminate truss, Maxwell simplified the method of calculating truss internal force by graphic method on the basis of predecessors. For statically indeterminate truss, Maxwell derived a general method to solve statically indeterminate structure from energy method. About 10 years later, his method was sorted out by O. Mohr (1835-1918) and the standard form was given. This is a common force method at present, also called Maxw.
3. Castigliano theorem
A. Castigliano (1847- 1884) is an Italian engineer. 1873, his engineer thesis was officially published in 1875. This paper contains the classical contents of structural mechanics, such as Descartes theorem and unit load method.
His theorem is that if deformation can be written as a function of generalized force,
Pi (I = 1, 2, n) is a generalized external force, then there is
Progress of structural mechanics in the 20th century
At the end of 19, the force method for solving statically indeterminate structures was established. The deformation method for statically indeterminate rigid frame structures was first proposed by AxelBendixen in 19 14 at the beginning of the 20th century. When this method was used to solve many unknown problems, HardyCross put forward a successive approximation method called relaxation method in 1930s. This method soon spread in the United States.
With the development of human civilization, the structure has become more and more complex. Since the beginning of this century, more and more complex structural problems have been put forward from the aspects of architecture, shipbuilding, aviation, bridges, vehicles, hoisting machinery, dams, tunnels and underground structures. Their strength needs to be analyzed.
In order to analyze these complex structures, people have to introduce a series of assumptions to simplify the structure. This simplification is too rough at present, but it is a transitional means between dealing with simple structure and meeting the computer age.
For example, the arch dam is a complex structure, and to analyze it accurately, it is necessary to solve the equation of the shell with variable thickness, which is a very complicated calculation work. 1929, the United States adopted an arch beam. In this method, the dam is divided into several arches in the horizontal direction and several beams in the vertical direction, and then the load distribution method is used to gradually approximate the solution. After the advent of computer, the arch beam method has been eliminated, but it did play an important role in history.
The complexity of the structure develops in two directions. On the one hand, the components are very simple, such as beams and rods, but they form an increasingly complex system with hundreds of unknowns. On the other hand, complex components, plates, shells and their combined systems have been developed. Shell theory was established in the period of love, and there was a big development stage in the 1930s and 1940s. At this time, a number of new problems have been put forward and solved, such as stability problems, nonlinear plate and shell problems, general theoretical problems of plate and shell, etc.
Pakovic (1887- 1946), an outstanding Russian engineer, published a two-volume dialogue on two new disciplines in 1947, which is a summary of the research results of complex structures in the early 20th century.
Development of computational mechanics
Human beings have a long history of studying computing tools, from several chips, abacus, hand-cranked computers and electric computers to thousands of years now. 1945 The electronic computer born in the United States is not only a revolution of computing tools, but also a great revolution that affects the whole science and technology.
The earliest design scheme of electronic computer ENIAC was put forward by J.W. Mauchly (1907-1980). The chief engineer of the research team is eckert (J.P.Eckert, 19 19-). At the end of 1945, ENIAC declared it complete.
Once the computer came out, it received people's enthusiastic attention and continuous improvement. It has gone through four generations: from 1945 to 1958. The first generation is electron tubes, from 1959 to 1963, the second generation is transistors, and from 1964 to the early 1970s, the third generation is integrated circuits, 77. Especially since the mid-1970s, microprocessors have greatly improved the performance of computers, and computers have become popular because of their low prices. According to statistics, since the birth of the first computer in 1945, the performance of the computer has doubled every 18 months, and the price has dropped by half every 18 months.
In history, all kinds of tools invented by human beings are designed to lengthen human organs, such as telescopes and microscopes, and lengthen people's eyes. The computer is an extension of the human brain. So people call computers computers. From principle, design, manufacture to application, computer has formed a huge new discipline group, which is computer science.
At the beginning of the 20th century, Jia, a famous British mechanic, summed up the law of mechanical development at the beginning of his famous book "Ship Structural Mechanics", and thought that there were fewer and fewer theorems and the calculation became more and more complicated. It means that some narrow theorems are contained by some generalized theorems, and the calculation formula is more and more complicated. So the biggest difficulty in mechanical research is the slow calculation speed. The slow calculation speed of cutting tools has become the bottleneck of mechanical research and development.
The original intention of Americans to invent electronic computer is to solve the typical complex mechanical problem of calculating trajectory. The appearance of computers has brought great changes to mechanics. Structural analysis, trajectory calculation, aerodynamic calculation, numerical weather forecast, seepage and groundwater movement law, orbit calculation in celestial mechanics and other increasingly complex issues. You can give it to the computer for calculation.
After the computer appeared, the research methods of mechanics increased from theory and experiment to theory, experiment and calculation. The powerful power of computers has eliminated some outdated methods that are not suitable for computers, developed new calculation methods that adapt to the characteristics of computers, and discovered many new phenomena with the help of computers, such as strange attractor and chaos.
The term computational mechanics appeared in the late 1950s. It is a new subject to solve mechanical problems, explore mechanical laws and process mechanical data by computer research. Computational mechanics is an interdisciplinary subject of mechanics, mathematics and computer science.
In the early days after the invention of computers, computers only used the speed of computers to solve mechanical problems or other problems. The next problem is that the workload of the program will make me unable to adapt to the high speed of the computer. A computer needs hundreds of workers to write programs to input data. Therefore, writing programs has become the bottleneck of rational use of computers. People have come up with many ways to solve this difficulty. Symbol assembly language, FORTRAN language, ALGOL language, etc. Since the 1950s, the software industry has appeared one after another and developed rapidly, just to solve this problem.
The emergence and development of finite element method is the most successful method to solve mechanical problems and save program manpower by computer. Its appearance also marks the formation of computational mechanics as an independent branch of mechanics.
Although the idea of finite element method can be traced back to earlier, for example, some people say that the idea of finite element was put forward by American R.Courant in the 1940s, some people say that it was put forward by Canadian J.L.Synge in the 1940s, some people even say that the finite element method is included in Euler's broken line method, and some people say that Liu Hui's arc cutting method is the finite element method of the Eastern Han Dynasty. Of course, these statements are not completely unreasonable. Because the idea of finite element method is indeed partly related to the work of the above-mentioned people. However, we should know that the finite element method is closely related to computers.
In fact, in the mid-1950s, a group of people all over the world were considering using computers to solve structural mechanics and continuum problems. For example, argyris, a Greek who worked in Britain and Germany in 1956, M.J.Turner, R.W.Clough and Martin in the United States in 1956, and vlaSOV () in the Soviet Union, so it is hard to say that the idea of finite element is an invention of one person and the product of a worldwide trend of thought.
However, an important event in the development history of finite element method is the doctoral thesis "Theory of Mathematical Elasticity" written by E.L.Wilson( 1930-) of the University of California, Berkeley, USA, which completed the first universal program for solving plane elasticity problems in the world in 1963. The purpose of this program is to use it to solve any plane elasticity problem without programming. As long as the necessary geometric, material and load data describing the problem are input according to the instructions, the machine can calculate and output the calculation results as required.
Once the program of finite element method was put into production, it immediately showed its incomparable superiority. In the field of elasticity, only complex function method and plane photoelasticity method are used to deal with plane problems. Compared with the finite element method, these two methods gradually withdrew from the historical stage.
Wilson later did a lot of meaningful research on the finite element program system. He compiled a program SAP (Structural Analysis Program) for various elements of finite element. Under his guidance, his graduate students wrote a nonlinear structural analysis program NONSAP. 198 1 year, he was the first to write the program SAP8 1 for the microprocessor.
SAP program was transplanted and modified by Qu Shengnian, Deng Chengguang and Wu Liangzhi, and SAP8 1 program was expanded and modified by Yuan, forming an independent version of SAP84. These two projects have played an important role in China. Non-SAP has been improved by Bathe in the United States, forming a nonlinear analysis program ADINA with world influence.
Subsequently, the finite element software for structural analysis developed rapidly. Software and software system, including two-dimensional element, three-dimensional element, beam element, rod element, plate element, shell element and fluid element, can solve various complex coupling problems of elasticity, plasticity, rheology, fluid, temperature field and electromagnetic field, and appear constantly. In 10 years, the production and sales of finite element software have formed a new social industry with considerable scale, and the use of finite element method to solve practical problems has been rapidly popularized in engineering and technical departments.
The finite element analysis of two-dimensional structures is the first paper that mentioned finite element at the American civil society electronic computing conference held in Pittsburgh in 1960. After that, a large number of finite element papers, collections and monographs emerged, and special academic conferences were held continuously. New elements and solvers are constantly proposed, including isoparametric elements, high-dimensional elements, nonconforming elements, quasi-conforming elements, hybrid elements, spline elements, boundary elements, penalty elements and so on. There are solutions such as bandwidth and variable bandwidth elimination method, super matrix method, wavefront method, substructure method, subspace iteration method, and pre-and post-processing research such as automatic grid generation. These works have greatly strengthened the problem-solving ability of finite element method and made it possible for finite element method to solve problems. The finite element method in plane stress analysis published by 1988 is a summary of the development of finite element method.
Several research directions that should be paid attention to
With the rapid development of computational mechanics and inspired by his success, some scholars have made overly optimistic estimates of the achievements of computational mechanics. For example, 20 years ago, some people in America said that in 10, wind tunnels would be replaced by computers. After 20 years, computers cannot replace any wind tunnel. Generally speaking, most problems that can be approximated by linear theory can be solved by computers, but for those mechanical problems that are essentially nonlinear, computers can hardly do anything at present.
Teacher Qian Xuesen said that mechanics is a century-old scientific and technological problem that uses computer calculation to answer all macro questions, and the calculation method is very important; Another auxiliary means is clever experiment. If 90% of linear problems can be solved by computers and 10% can be solved by experiments, then the situation is just the opposite in the field of nonlinearity. Therefore, computational mechanics has made efforts in two aspects since its birth. On the one hand, for linear problems, it is mainly to expand the scale of solving problems; On the other hand, for nonlinear problems, efforts are being made to find calculation methods.
In recent years, solving nonlinear problems has become the main direction of computational mechanics. It seems that Qian Xuesen's point of view is already a reality for linear problems in macro-problems, but for nonlinear problems in macro-problems, this can only be regarded as the direction of computational mechanics, and we should be prepared to go a long way.
Since 1960s, nonlinear terms have been gradually incorporated into the finite element program of structural analysis. For example, discussing the plastic properties of structural materials is called physical nonlinearity, and discussing the correction caused by large structural deformation is called geometric nonlinearity. The initial calculation scheme adopts the load increment method.
Since the late 1960s, people have found some problems in solving practical problems. When the load reaches the maximum, the computer always overflows and stops. This problem has puzzled people for many years, and it was not solved until the late 1970s and early 1980s. 197 1 year, American scholar G.A.Wempner and Dutch scholar E.Riks put forward the methods to solve this problem in theory respectively. In the early 1980s, people realized this method through programming. This method was later called arc length method.
After the computer entered the historical stage, it first combined with structural analysis in mechanics to form computational mechanics. At this time, the problems of structural optimization and structural control are put forward. That is to say, under the given load and functional requirements, we can find the optimal structural form and structural parameters with the help of computers, or find the optimal control force under certain external force conditions, so that the internal force or displacement of the structure can meet the requirements. In recent years, a kind of material, called electro-rheological material or intelligent material, has appeared which can quickly produce strain response under the excitation of electrical signals. When this material is applied to a structure, given a certain electrical signal, the structure can respond quickly. This structure is also called intelligent structure. The research of intelligent structure is an important research direction in recent years.
Structural optimization design is an important nonlinear research field in computational mechanics. Its main purpose is to find the optimal parameters of the structure under a series of conditions (also called constraints). Usually this kind of problem is nonlinear and requires a lot of calculation, so it can only be solved by computer. Under the vigorous advocacy, organization and promotion of Professor Qian Lingxi (19 16-), Cheng Gengdong and Zhong Wanxie of Dalian University of Technology have made some important achievements, and the research on structural optimization has developed well in China.
After solving the nonlinear problem, there is also a divergence problem. In the general finite element program, the structural stability problem usually boils down to an eigenvalue problem, which is based on linear theory. When solving with nonlinear programs, it is often impossible to move forward because of bifurcation. This is because the degradation of the overall stiffness matrix of the structure at the bifurcation point will never be solved again.
In order to overcome this difficulty, people have developed a series of static bifurcation and hopf bifurcation methods for the equilibrium solution of high-dimensional systems, but it can not be said that it has been completely solved in practice. For an overview, please refer to the Handbook of Finite Element Methods co-authored by Wu and Su Xian (Science Press, 1994). So far, it is still a difficult problem to calculate homoclinic orbits and heteroclinic orbits of high-dimensional systems and the transformation of high-dimensional systems into chaos.