In this experiment, we will

1, in the form of group activities, to cultivate students' cooperative spirit and orderly working ability; Cultivate students' sense of cooperation and competition through activities such as finished product display and competition;

2. In the production process, cultivate the spirit of not being afraid of difficulties, not sticking to the rules and daring to innovate.

3. Learn production technology and understand the function of the main structure of the bridge. Through the design and manufacture of paper bridges, we can know that the strength of materials is related to their geometric shapes.

4. Learn to think independently in various load-bearing experiments and paper bridge design.

5. Cultivate students' ability to cooperate with others in research.

6. Improve the skills, techniques and appreciation of creating models through the modeling design of bridges.

7. Learn simple technical design.

Activity content

Design and Manufacture of Paper Bridge

background material

1, knowledge background:

(1) pressure and pressure

Know the concept of pressure, pressure refers to the force that presses vertically on the surface of an object.

Understand the concept of pressure, which is the pressure on an object per unit area.

The pressure of solid is related to the stress area, and the cross-sectional area has a direct influence on the pressure. The larger the cross-sectional area, the smaller the pressure.

⑵ Arch bridge: A box of matches can be held up by a piece of paper and arched, indicating that the object arched upward can bear the external pressure best, and its strength is greater than that without arch. The matchbox is pressed on the paper arch bridge, giving the paper arch a static external force, which is different from the impact force of bullets on armored vehicles. The ability of paper arch bridge to resist static external force is called static strength.

Our ancestors discovered this characteristic of arched objects a long time ago and applied it to buildings. Most of the tombs of the Eastern Han Dynasty excavated in various places have "arch" structure, which shows that the arch-building technology in China was quite popular 1000 years ago.

The oldest stone arch bridge in existence is Zhao Zhouqiao in China. Zhao Zhouqiao was designed and supervised by Li Chun, a stonemason in Sui Dynasty. It was built in 6 16 AD and has a history of 1300 years. This stone bridge spans the south river of Zhao County, Hebei Province, and its mouth is curved, just like a rainbow across the river. In the long years, Zhao Zhouqiao has withstood the shaking of earthquakes, the impact of floods and the crushing of chariots and horses, and still stands on the Weihe River. (Photo 1) Zhao Zhouqiao not only has a big arc arch, but also has four small arches on the bridge shoulder. When flash floods break out, small arches can drain away floods. Zhao Zhouqiao's secret lies in the arch. Scientific and technical personnel and workers in China inherited and developed the tradition of arch bridge architecture, and created hyperbolic arch bridges by using modern strength theory and engineering. The shape of hyperbolic arch bridge looks no different from that of ordinary hollow arch bridge. But if you walk under the bridge, you will find that its belly is concave, which seems to be made up of fenders of several bicycles. It's really an arch in the arch. The advantages of this kind of bridge are low cost, large load, convenient construction and material saving. The highway approach bridge of the majestic Nanjing Yangtze River Bridge is this kind of hyperbolic arch bridge. (Figure 2)

Hyperbolic arch can bear more load than single arch, mainly because hyperbolic arch arches not only in one direction, but also in the other direction perpendicular to it. The fender of a bicycle is this kind of hyperbolic arch. When stressed, the force is transmitted more evenly along the two arches; When a local stress is too large, the double-arch can quickly adjust its balance by itself, so that the whole double-arch will not be destroyed by local stress.

Arch structures can be used to build bridges, and another important purpose is to build dams. Especially the hyperbolic arch dam, because the water pressure on the vault can be transmitted to the river bank evenly, the stability can be maintained by the solid embankment. Compared with the gravity dam which is completely balanced by its own weight, it can not only reduce the volume and save materials, but also has certain elasticity, adaptability to local deformation of the foundation and good seismic performance.

There is a "double arch bridge" on our feet, which means that people with normal arches can distinguish three arches: two longitudinal arches and one transverse arch.

(3) The history and development status of bridges:

In ancient China, natural materials such as wood, stone, rattan, bamboo and even leather were used to build bridges. After the appearance of forged iron, a simple iron cable bridge appeared. Their strength is very low. Wood, rattan, bamboo and bark are perishable, and most of the ancient bridges that can be preserved so far are stone bridges. The famous stone bridges in ancient China are: Zhaozhou 1 Anji Bridge in Hebei, Lugou Bridge in Beijing and Anping Bridge in Quanzhou.

During the period of 1900- 1949, the bridge construction in China was almost at a standstill, especially in China. Among them, the representative bridge is the Qiantang River Bridge in Hangzhou, which was designed and built in 1943 by Mr. Mao Yisheng, a bridge engineering expert of the older generation in China. (Figure 3)

Qiantang River Bridge is located near Pagoda of Six Harmonies, the gate of Hangzhou. This is the first double-deck highway and railway bridge designed and supervised by China engineers. The whole bridge length is1453m, the main bridge length is1072m, and the approach bridges on both sides are 38 1 m.. 1931111held a groundbreaking ceremony and 1935 was opened to traffic. This modern steel bridge has made outstanding contributions to the communication between the North and the South, and it also marks that China has entered a new stage of building bridges with steel.

At the same time, foreign bridges have far surpassed China, steel technology reached its peak, and the first suspension bridge construction climax appeared. The famous bridges are: new york Washington Bridge built at 193 1, San Francisco Bridge built at 1937 and Sydney Steel Arch Bridge built at 1932.

From 1950 to 1978, the bridge construction in China experienced two historical periods: arduous pioneering and tortuous development. Wuhan Yangtze River Bridge (Figure 4) and Nanjing Yangtze River Bridge have been completed and opened to traffic.

Nanjing Yangtze River Bridge, located in Nanjing, Jiangsu Province, is an important milestone in bridge construction in China. The main bridge is a continuous truss bridge with a length of1.576m.. Nanjing Yangtze River Bridge is a Yangtze River Bridge built entirely by its own technical strength and domestic materials. Therefore, its completion marks that China's bridge construction technology has entered a new level and stage of independence.

At the same time, foreign bridges show a new trend of diversification and their respective capabilities. Cable-stayed bridge has become the main bridge type, and Japan and Denmark have also begun to implement grand cross-sea engineering plans.

1979- 1999, in this short twenty years, China's modern bridge industry has made remarkable achievements and quickly caught up with the advanced level of bridge construction in the world. Shanghai nanpu bridge, Yangpu Bridge and Xupu Bridge have established the world status of Chinese bridges. Five suspension bridges were built at the same time: Shantou Bay Bridge with a span of 452 meters, Humen Bridge with a span of 888 meters in Guangdong, Xiling Yangtze River Bridge with a span of 900 meters, Jiangyin Yangtze River Bridge with a span of 1385 meters, and Haicang Bridge with a span of 648 meters in Xiamen, which indicates that China is moving towards the world bridge kingdom.

In terms of modern bridge construction technology, China has become one of the advanced countries in the world.

At present, China has been able to skillfully build long-span and deep-water foundation bridges, and the bridge construction technology ranks among the top in the world. According to Huang Zhendong, Minister of Communications, China has made technological breakthroughs and development in the construction of prestressed concrete beam bridges, various arch bridges, cable-stayed bridges and suspension bridges. China has successively built Jiangyin Yangtze River Bridge, Humen Bridge, Wanxian Yangtze River Bridge, Nanjing Second Yangtze River Bridge and other major projects with high technical content and influence in the world. Jiangyin Yangtze River Bridge, with a main span of1.385m, is the longest span bridge built in China in the 20th century, ranking fourth among similar cable-stayed suspension bridges in the world. The design and construction of the super-long reinforced concrete arch bridge of Wanxian Yangtze River Bridge is an international innovative technology and won the first prize of national scientific and technological progress in 2000. The complete set of construction technology of Humen Bridge won the second prize of national scientific and technological progress in 2000.

The adoption of new technology, new technology and new equipment ensures the rapid development of bridge construction in China. By the end of last year, there were 240,000 highway bridges with 8.65 million linear meters in China, including extra large bridges 1 139 and bridges 1274 1 seat. These bridges are beautiful in shape, beautiful and practical, and have become a local landscape.

As a span structure, the bridge has various shapes, which are mainly influenced by its span, materials, loads and construction methods, and of course, people's ideology or aesthetic tendency. Just some outstanding bridge engineers, who used their deep understanding of engineering structure to design many great bridges boldly, persistently and creatively, such as the anti-suspension bridge, curved cable-stayed bridge, span beam bridge and prestressed steel bridge designed by Lin Tongyan.

2. Methodological background:

(1) manufacturing method and requirements of paper bridge:

The production time is 35 minutes.

The strength of the bridge (between two piers) shall not be less than 15cm, and the width of the bridge shall not be less than 5cm.

The bridge has strong bearing capacity and is firm (subject to the weight of heavy objects).

(2) Scientific research methods:

(1) Show students all kinds of bridge objects, such as I-beams and angle steel (as shown in the figure), so that students can understand that by changing the shape of paper, the strength of soft paper can be increased and it can bear a certain weight. Students do their own experiments to find more ways to increase the load-bearing capacity of paper by changing the shape of paper, and cultivate students' ability of exploration, observation and analysis; Initially train students to abstract and summarize the essential attributes of common things, and form the ability of generalization, reasoning, induction and synthesis of scientific concepts.

② Students look for information or consult teachers and parents about "the relationship between object shape and strength" and scientific principles, and collect and consult information and pictures about bridge design and modeling. Train students to learn to collect, sort out and initially use all kinds of information, and carry out investigation and research purposefully. The collected data and information will be accumulated, classified and kept, and the concept of information accumulation will be established.

③ Students work in groups. All activity groups are required to cooperate closely according to the drawings and production requirements designed by the group to complete the production of the paper bridge. In the production process, pay attention to using "recording paper" (or data table provided by the teacher) to record relevant data. Make students learn the scientific methods to deal with observation and production results.

④ Each activity group shows its own work, and each group chooses a classmate to talk about the feeling of design and production. Cultivate students' ability to fully express observation results, production process and finished product description in language.

(3) the formation of scientific behavior habits:

① Develop students' awareness of learning, master good reading skills and form the habit of reading consciously after class by independently completing independent learning activities such as finding materials and preparing design drawings.

(2) The activity group cooperates to make the paper bridge, so as to cultivate students' team spirit of unity and cooperation.

(3) Pay attention to recording data in production and develop good scientific behavior habits.

3. Keywords: pressure, pressure, static strength and bearing capacity

Design concept

(a) Feasibility of the activity and reasons for its success:

1.

The choice of activity content conforms to students' existing knowledge structure and cognitive level, and pays attention to cultivating students' comprehensive knowledge and ability to solve practical problems. In the activity, they comprehensively used the knowledge and ability of physics, mathematics, geometry, fine arts, handicrafts and so on.

2. The choice of activity content has certain scientific and technological content, and the organic combination of research, experiment and production is helpful to cultivate students' scientific and technological awareness, scientific methods and scientific exploration spirit.

3. The activity process design highlights the student-centered teaching process, inspires students to learn independently and explore actively, and gives full play to students' initiative and creativity in learning.

4. According to the activity content, determining the activity form and carefully designing the activity process are the keys to the success of an activity class.

5. Choosing appropriate activities can effectively stimulate students' interest in learning and maintain a good learning state.

6.

Adequate preparation before class is the premise and guarantee of a good activity class, including: activity plan design, data collection, teachers' pre-class experiments, research, production, teaching AIDS, data equipment preparation (video, projector, etc. ).

(2) Main points of activities:

1. The activities are in groups, and the whole class is divided into several activity groups (4 people in each group) to carry out activities in the form of competitions.

2. Teachers guide students to carry out experiments on the strength and bearing capacity of paper, determine the purpose of the experiment, and prepare for the design of paper bridge.

3. Before class, students are required to collect pictures of bridges and mechanics of materials, and study and design the production drawings of paper bridges in class.

4. Make the paper bridge according to the design drawings. When finished, the group will be displayed and compared.

5. Paper bridge identification requirements and standards:

① Production time: 35 minutes (30 minutes)

(2) pier span 20-25cm, bridge deck width 5-7cm( 10).

(3) The bridge has strong bearing capacity and is firm (subject to the weight of heavy objects). If the span is large, you can add points as appropriate.

(4) Beautiful shape of the bridge (30 points)

Implementation conditions

1. Student sports equipment

(1) material: several pieces of octagonal paper, four pieces of octagonal paper for each bridge.

(2) Appliances: scissors, paste, pencils, erasers, rulers, compasses, triangles, etc.

⑶ Erection: books, cartons or wooden blocks, etc. Students can choose at will.

2. Teaching AIDS and equipment

(1) balance, weight, stone, etc.

(2) A video recorder, a TV set and a physical projector.

3. Site requirements

Group activities in ordinary classrooms

4. Human resources of lecturers

Activity process

(1) Activity 1: Explore the relationship between the shape of paper and the weight it bears (or the strength test of paper) Activity time: 45 minutes.

1. Import:

Through audio-visual demonstration, show students various objects used for bridges, such as I-beam and angle steel (as shown in the figure), so that students can understand that by changing the shape of paper, the strength of soft paper can be increased and it can bear a certain weight. Inspire and guide students to explore and find more ways to increase the load-bearing capacity of paper by changing the shape of paper.

2. Development of activities

(1) Teachers patrol students' experimental process and give random guidance.

(2) Ask students to express the production plan clearly in different forms such as words, charts and so on.

⑶

Make the satisfactory design pattern into a "bridge deck" with a width of not less than 5 cm and a length of not less than 15 cm, and measure its bearing capacity. Select the "bridge deck" with the largest load in the group and try to analyze the reasons for the largest load (books, cartons or wooden blocks as erection objects are freely selected by students)

(4) Presentation and communication of achievements

Choose a classmate from each group, report and show the group's achievements, and the group will supplement them. Choose the best design scheme.

3. Arrange the tasks after this activity and the contents of the next activity:

(1) After the activity, look for information or ask teachers and parents about "the relationship between object shape and intensity" and scientific principles.

⑵ According to the experimental method of this activity and the research of related materials, the structural modeling of paper bridge is preliminarily conceived.

(3) Collect and consult information and pictures about bridge design and modeling. Draw a sketch of the design of the paper bridge.

(2) The second activity: paper bridge design activity time: 45 minutes.

1. Import:

The teacher set the predetermined goal of the activity.

(1) By exchanging information with students, students can better understand the relationship between the shape and strength of objects;

⑵ Enlighten students' thinking by showing the obtained materials and sketches of paper bridges.

2. Activities:

⑴

First, please look at some pictures of bridges. This lesson requires each group to study the design scheme of paper bridge and draw drawings according to each student's ideas and collected data and pictures. (The design time is 30 minutes. )

(2) Students start group activities (teachers patrol)

3. Overview of activities:

In class, the students designed the pattern of the paper bridge, and the imperfections need to be further revised, especially how to improve the bearing strength of the bridge deck needs further research and exploration, and spare time should be used to do exercises to prepare for the next class.

(3) The third activity: making a paper bridge. Activity time: 45 minutes.

Before class, students need to prepare corresponding materials and appliances according to the plan of designing bridges by the group.

1. video import: show the activity process of the first two classes.

2. Activities:

In the last class, paper bridge design, each group completes drawing. This lesson needs activities.

According to the drawings designed by this group, the team cooperated closely with the production requirements and completed the production of the paper bridge.

3. Activity requirements and evaluation rules: (teacher-student evaluation)

(1) The production time is 35 minutes (30 minutes). If it is not completed within the specified time, this item is not allowed to score.

(2) Span (10 point)

(3) Bearing capacity (30 points)

(4) Modeling (30 points)

5] Creativity

[6] spirit of cooperation

2. Exhibition of works:

Select several groups that have finished making paper bridges to show their works, and send a classmate from each group to talk about the feelings of design and production.

◇ Activity summary:

(1) Summarize the student activities.

⑵ In the activity, students' innovative ability and learning attitude of being brave in exploration and serious study are affirmed.

(3) Encourage students to seriously study scientific and cultural knowledge, master various abilities and become cross-century talents.

◇ Activity evaluation and summary

1. Student self-evaluation, teacher summary.

2. Ask students to talk about the design ideas, production methods and production experience of the works.