Teaching experience of basic engineering course in architectural engineering direction?
First, several key issues in teaching
(A) the importance of conceptual design
As the carrier of buildings, foundation soil has the characteristics of three phases, fragmentation (discontinuous medium) and natural variability (inhomogeneity, anisotropy, structure and time-space variability). In addition, the diversity of superstructure and the uncertainty of geotechnical parameters lead to the complexity and uncertainty of foundation problems. Therefore, conceptual design is a necessary and important way to ensure basic safety. The conceptual design of foundation is to comprehensively apply the basic concepts of soil mechanics, structural mechanics, geotechnical properties, scientific laws of geological evolution, the influence of groundwater, the characteristics of various construction technologies, the characteristics of various structural systems, the interaction between foundation and foundation, local experience and economic level to the foundation design. Conceptual design runs through the whole process of basic design. The construction of Xi Wild Goose Pagoda in Shaanxi Province embodies the wisdom of the ancients to solve complex problems with simple concepts. For example, the ancients used the method of "piling soil" to build towers. Compared with the current method of preloading foundation, the load and range of pile soil are much greater than the weight of tower. After clearing the soil, the bearing capacity and deformation of the foundation after preloading can generally meet the requirements. The foundation of the tower is semicircular, similar to the base of the "tumbler". It has the function of automatic rectification, which embodies human wisdom. The design of six stone pillars in Athens adopts a conceptual improvement scheme, and the shapes of the pillars are carved into slim girls. The flower basket on the girl's head is adopted at the top of the column, which not only plays the role of column cap, but also realizes the beautification function. The shoulder hair of the column is used to transfer the load to the part with smaller trunk section, that is, the neck of the human body, which not only increases the aesthetic feeling but also avoids the sudden change of stiffness. The lower part of the column is supported by girls wearing long skirts, and the legs are bent, which not only increases the cross-sectional area of the column, but also increases the stability. It is precisely because the ancients skillfully combined the concepts of aesthetics and mechanics with conceptual design that architecture stood for thousands of years. Use basic concepts to guide the concrete calculation of foundation, understand the applicable conditions of mathematical model, understand the consistency between assumed conditions and actual projects, and understand the limitations and possible deviations of calculation methods. Use basic concepts and experience to analyze and judge the calculation results. Reasonable judgment of calculation results is very important for the safety of engineering, such as the settlement calculation of buildings. There are many factors affecting settlement, and some factors such as load and superstructure stiffness can be accurately considered. Some factors such as foundation stiffness and soil properties are inaccurate, and some factors such as construction period, construction technology and construction sequence are not easy to consider. The rationality and accuracy of the calculation results depend on the comprehensive concept and experience. This concept is used to judge whether the settlement distribution and settlement difference are reasonable, and the existing engineering experience is used to judge the accuracy of the calculated values. Through the detailed description of typical conceptual designs such as Big Wild Goose Pagoda and ancient Greek stone pillars, teachers guide students to understand the characteristics of basic engineering design, not blindly believe in calculation, and realize the importance of accurate basic concepts and rich engineering experience to basic engineering design.
(2) Characteristics of bearing capacity of natural foundation
Foundation soil is a kind of large deformation material. When the load increases, the compactness of foundation soil increases with the corresponding increase of foundation deformation. When the deformation is stable, the internal friction angle, cohesion and gravity of the foundation soil are improved to varying degrees, and the bearing capacity of the foundation is gradually improved, so it is difficult to define a real "limit value". On the other hand, the use of buildings has functional requirements, and often the foundation bearing capacity still has potential to be tapped, and the deformation has reached or exceeded the limit value of normal use. Therefore, the foundation design adopts the principle of normal use limit state, that is, according to deformation control design [2]. It can improve the bearing capacity of foundation. For concrete or steel bars, each strength grade has a certain standard value and design value, but the bearing capacity of foundation soil is not the engineering characteristic index of soil, and the bearing capacity of foundation soil with the same index may vary greatly. There are many factors that affect the bearing capacity of foundation soil, which are not only related to the soil quality and buried depth order of the soil layer, but also closely related to the shape, size, buried depth, stress of the foundation, adaptability of the superstructure to deformation, fluctuation of groundwater level and regional experience. The bearing capacity of foundation increases with the increase of buried depth, and the bearing capacity can be modified in depth. The bearing capacity of foundation increases with the increase of basement width and changes with different soil quality. In saturated soft soil, it is impossible to improve the bearing capacity of foundation by increasing the size of foundation, but for sandy soil, the internal friction angle is not zero, and increasing the width of foundation can improve the bearing capacity of foundation. At this time, the width can be used to correct the bearing capacity. Through classroom comparative analysis, students have a thorough understanding of the concept of foundation bearing capacity, which lays the foundation for foundation design.
(3) Selection of basic scheme
The foundation scheme has a decisive influence on the safety, cost and construction of building projects. The determination of basic scheme is a complex technology, which needs comprehensive analysis and judgment. First of all, we need to know the environment around the site and the stability of the site, because once the site has problems, the damage to the building is devastating. Secondly, it is necessary to understand the distribution and engineering properties of foundation soil, investigate the existing buildings and equipment pipelines around the site, investigate the local similar engineering data, and consider the seismic factors such as the overall instability of foundation soil caused by sand liquefaction and the earthquake settlement of soft soil foundation. Finally, the groundwater situation, the change of groundwater level and the influence of construction projects with underground structures on foundation safety are analyzed. The corrosion of groundwater affects the durability of concrete, destroys the strength of foundation soil, forms soil holes, causes surface collapse and affects the stability of construction sites; Confined water in groundwater may damage the foundation pit and foundation, causing great losses to the project; In the alpine region, seasonal frozen soil causes frost heave and thaw settlement of foundation soil, which endangers the safety and normal use of buildings. Foundation is the carrier of the whole superstructure and serves it. The foundation scheme should consider the form of superstructure, load characteristics, stiffness characteristics, local construction conditions and comprehensive economic comparison, and finally determine the foundation treatment method, key control points of deformation and foundation form, so that students can understand the importance and complexity of determining the foundation scheme and realize that only excellent schemes can become excellent designs.
Second, the engineering example analysis
Case 1: The Leaning Tower of Pisa in Italy was built in 1 173. When it was built to about 29m, it stopped because of obvious inclination. After returning to work in 1994, it was completed in 6 years, reaching 48m. 1360 resumed, 10 completed, with 8 floors and a tower height of 55m. At present, the settlement on the north side is above 1m, the settlement on the south side is nearly 3m, the settlement difference between the north and south ends is 1.80m, and the center of the tower top deviates from the center line by 5.27m, with an inclination of 5.50. This project is a typical example of building inclination caused by uneven settlement of foundation. Case 2: Transcom Barn, Canada, with a plane size of 23.5m×59.4m, a height of 3 1m and a volume of 36500m3, has a reinforced concrete raft foundation with a thickness of 0.6m and a buried depth of 3.6m, and a soft clay layer with a thickness of 19 165438+. When the granary filled with millet reached 87.7% of the rated volume, it was found that the granary sank. Within 24 hours, the west section sank by 8.8 m, the east end rose by 1.5m, and the dip angle was nearly 270. The upper barn was intact. Case 3: The central hall of Shanghai Industrial Exhibition Hall is a frame structure, with a box foundation and a buried depth of 7.27 m. The exhibition halls on the two wings are strip foundations, and the foundation is highly compressible muddy clay. The exhibition hall was started on 1954, and the average settlement of the foundation measured at the end of that year was 60cm. 1957, the maximum settlement around the central hall reached 146.55cm. The properties of these three foundations, the causes of these three foundation accidents and the corresponding treatment methods were discussed in the lecture. When talking about the leaning tower of Pisa, the students were in high spirits, and put forward a series of questions such as why the leaning tower of Pisa is leaning, whether it will continue to sink, and how to deal with it. The causes of inclination are analyzed. The bearing layer of the foundation is silty sand, and there are silt and clay layers below it. The foundation compression layer is uneven, resulting in inclination. Now it sinks every year1mm. Treatment measures:1838 ——1839 excavation of annular foundation pit for unloading; 1933 ——1935 foundation pit waterproof treatment and foundation ring grouting reinforcement; 1July, 1992, the tower was reinforced, and the foundation was treated by weighing method and soil borrowing method, and several treatment methods were summarized. In the second case, the actual bearing capacity of the foundation is less than the basement pressure, and the barn gene overload leads to strength failure and slippage. Treatment method: More than 70 concrete piers supporting bedrock were added under the granary, and the granary was gradually rectified with 388 50t jacks and supporting system. Case 3 is caused by the high compressibility of soft soil. Excessive deformation of foundation seriously affects the normal use of structure. According to the observation and analysis of Soviet experts, Professor Chen Xizhe and Professor Chen Liangsheng from Tsinghua University, it is considered that the cracks can be used continuously after being repaired. 1September 1979, the cumulative average settlement of the central hall reached 160cm. During the 22 years from 1957 to 1979, the settlement was only about 20cm, indicating that the settlement has stabilized. However, due to the serious foundation subsidence, the outdoor water, electricity and heating pipes connected inside and outside the building are broken. In addition, from the dribs and drabs of life, stimulate students' interest in learning courses. For example, when it comes to the "crossing" function of the foundation, it is not easy to walk directly through the swamp (silt or muddy soil) or lay straw bags, but it can be solved by putting a plank. Why is this happening? Ask questions, let students discuss, and then analyze and summarize. Through the above guidance, students can realize the importance of basic engineering, and naturally the basic problems are reduced to two major problems: strength and deformation. Starting from practical engineering, questions are raised, and heuristic teaching is adopted to inspire students to think and explore independently, so that students can seek answers, pay attention to cultivating students' independent thinking ability, master the basic methods and thinking rules for solving practical problems in basic engineering, establish a set of logical thinking methods and thinking methods suitable for them, and then change "passive acceptance" into "active learning" to improve students' learning ability, innovation ability and ability to analyze and solve problems.
Third, the cultivation of engineering consciousness.
(A) to improve teachers' engineering awareness and professionalism
Basic engineering is both theoretical and practical, so teachers should pay attention to integrating theory with practice in class. On the one hand, teachers are required to have profound basic theoretical knowledge and professional knowledge, on the other hand, teachers are required to have practical engineering experience, otherwise the teaching process can only be scripted, students' learning enthusiasm is poor, and the teaching effect is not good. To this end, the teachers of the School of Civil Engineering of this school have also made attempts and efforts in the following aspects. (1) Young teachers participate in the "Overseas Training Program for Professional Teachers in Colleges and Universities" jointly organized by the National Scholarship Fund Committee and the University of California, San Diego (UCSD). Through half a year's training and study in English language ability, professional course teaching, classroom activities and professional teaching research, they absorb multi-cultures, learn the latest scientific and technological achievements of developed countries, strengthen their professional and language skills, promote the reform process of higher education in the western region, and improve the ability of education in the western region to connect with the world. (2) Young doctors who are studying and just graduated are required to work in the laboratory for one year, participate in the teaching and scientific research in the laboratory, and strengthen the practical ability of young teachers. (3) In summer, send young teachers to the Project Department of the Engineering Bureau for on-site training in turn to improve the engineering practice ability. (4) 50% of the teachers in the Department of Architectural Engineering of the College have passed the national first-class registered structural engineer examination, and are fully familiar with the relevant national, industrial and even regional codes through review, so as to achieve mastery in teaching. Teachers who have obtained qualification certificates are generally technical consultants of enterprises, and they also cultivate and enhance their practical ability while cooperating. In addition, young teachers actively participate in engineering survey, design and construction, which further improves teachers' engineering literacy, and gradually forms a team of teachers with advanced educational concepts, solid professional knowledge and rich engineering experience, ensuring the cultivation of students' engineering awareness in all aspects of teaching. In the teaching process, some contents about practice in the national question bank for practitioners such as "geotechnical engineer" and "structural engineer" are appropriately introduced. Through classroom analysis and explanation, boring courses will not be boring, and you can get twice the result with half the effort.
(2) Strengthen practical teaching and cultivate students' engineering awareness.
A relatively stable practice base is the basis for implementing the practice content and ensuring the practice effect. At present, the School of Civil Engineering of our school has jointly established practice bases inside and outside the school with a large number of enterprises and institutions, such as some national railway bureaus, the First Railway Survey and Design Institute, some engineering bureaus of China Railway Group, companies affiliated to Gansu Construction Engineering Corporation, Lanzhou Zhonghe Real Estate Development Co., Ltd., Gansu Survey Institute of China Railway First Hospital Group, school design institutes and supervision companies. In addition, students are encouraged to contact the proposed employment unit for production practice on the premise of ensuring safety and completing internship tasks. Cooperate with the implementation of the training plan for outstanding engineers, sign cooperation agreements with China Railway 21st Bureau, China Railway Northwest Research Institute, Lanzhou Railway Design Institute and other units to build a national engineering practice education center and further expand the practice base. Through close cooperation with the teaching practice base, students are led to visit various representative projects in Lanzhou, such as foundation pit excavation and foundation pit support of high-rise residential buildings in urban areas, and several meters long supporting piles, prestressed anchor rods and soil nailing walls are set up; In collapsible loess foundation, soil and lime-soil compaction piles are used to eliminate the collapsibility of foundation soil, so that the project manager at the construction site can form on-site teaching, introduce the construction process, problems in construction and countermeasures, and make students form perceptual knowledge of foundation pit engineering. After visiting various shallow foundation forms on the spot, the overlapping method of foundation reinforcement and superstructure is clarified, which makes students clear the applicable conditions, basic structure and reinforcement requirements of various foundations. In the teaching of pile foundation, by visiting the piling site, we can understand the types and characteristics of piles, pile spacing, pile diameter, application scope, piling technology and pile quality inspection. Through on-the-spot observation, students' interest in learning this course is increased, their engineering consciousness is cultivated, and their understanding of civil engineering specialty is deepened. Since 20 12, the school has set up open experimental projects every year, with students actively participating, and each group of students is led by a teacher. Students' practical ability and innovative ability are cultivated through training such as selecting topics, searching materials, making experimental plans, experiments and calculation and analysis. In the teaching process of basic engineering, according to the lecture progress, the design block diagram is given with the topics of "design of reinforced concrete strip foundation under wall", "design of reinforced concrete independent foundation under column" and "design of pile foundation". According to the given geological conditions, students are required to complete the design of three foundations. In addition, students who have a good grasp of the situation can further request to learn PKPM, JCCAD and other software to compare and analyze the hand calculation results. Through the comprehensive training of large-scale homework, students' understanding of book knowledge is strengthened, and the whole design process and corresponding structural requirements of typical shallow foundation and deep foundation are mastered skillfully, so that students can review the past and learn new things in the design process. In the teaching of foundation engineering for many years, through the discussion of several key issues such as conceptual design, foundation bearing capacity and foundation scheme selection, students can clear their minds and master the design principles. Through the analysis of engineering cases, students can deeply understand the importance of basic engineering and master the basic methods and thinking rules of analyzing and solving practical problems of basic engineering. By urging teachers to improve their engineering literacy, we can ensure that students' modern engineering consciousness is cultivated in all directions inside and outside the class and inside and outside the school. Through practical teaching links such as experience, practical training and comprehensive training, students' engineering awareness and practical ability have been cultivated, and the satisfaction rate of employers has been significantly improved.
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