Teaching Structural Analysis through design, building and testing

Teaching Structural Analysis through design, building and testing M. Solís, A. Romero, P. Galvín Escuela Técnica Superior de Ingenieros, Universidad de Sevilla, Camino de los Descubrimientos s/n, 41092, Sevilla, Spain [email protected], [email protected], [email protected] Abstract This paper presents the results of an innovative teaching experience in the area of structural analysis in the Mechanical Engineering course of the Universidad de Sevilla, Spain. The teaching methodology used is aimed at motivating students to learn by promoting the design, calculation, building and testing of structures. This method not only trains students to make calculations but also develops skills that allow them to understand how structures function. The project includes subjects taught in the third and fifth year of the course. In their third year, students begin their structural training with the subject Structural Analysis, in which they learn the basics by designing, building and testing balsa wood structures. Students have access to computer software to optimize the design of their models before building and testing them in the laboratory. After this first approach to Structural Analysis, students receive training on more advanced concepts. A few examples of such concepts are the dynamic behavior of structures and instabilities in specific types of structures such as plates and laminar structures and in structural materials such as steel and concrete. Before completing their studies, students are exposed to a project-based teaching methodology again in the subject Experimental Structural Analysis. In this subject, students deal with similar projects to those they will face as professionals after graduating. This paper explains the advantages of this methodology for teaching in engineering. INTRODUCTION At the School of Engineering of the Universidad de Sevilla, students learn Structural Analysis between the third and fifth year of the Mechanical Engineering course. In third year, all the students of the course learn the basics of the subject; in fourth and fifth year, students who have chosen to specialize in Structural Analysis gain greater knowledge about the behavior of structures. An innovative teaching experience for this course was launched some years ago to motivate students to learn by promoting the design, calculation, building and testing of structures. Similar innovative teaching approaches have been also previously established in other institutions (Glynn and Fergusson 1994; Romero and Museros, 2002; Hadim and Esche 2002; Elazouni and Raslan 2003; Unterweger 2005). This not only trains students to make calculations but also develops skills that allow them to understand how structures function. The innovative teaching experience has been set up before the new European Higher Education Area (EHEA) was established in the School of Engineering of the Universidad de Sevilla. It was originally promoted by the authors, but after two years it was proposed as an innovation project according to the Teaching Methodologies Renew Program of the Universidad de Sevilla. This Program supplied funding for acquiring new teaching facilities (laptops, digital drawing tablets) and the fungible goods for the experimental tests (steel bars, sand, cement, wires, strain gages, etc.). The new EHEA teaching methodology, applied to practical lessons, require not only an increase in human resources but also an increase in teaching expenses. As regards the use of new Information and Communication Technologies, the virtual teaching platform of the Universidad de Sevilla is used. This kind of e-learning platforms is used by many institutions for online teaching and learning. The virtual platform is useful to help students and teachers share information, assess knowledge, manage discussion forums, etc., but does not replace on-site teaching and learning. In the subjects dealt with in this paper, all the documents used in the teaching are available to students on the platform. The platform is also used to include a description of the practical classes, audiovisual materials, questions for students to assess their own knowledge on the subjects and other documents of interest. The new teaching experience has been introduced in two different subjects of the course, so it is only partially applied during the course. These kind of new teaching methodologies help students to acquire practical knowledge by themselves, so they are especially suitable for engineering education. However, their overall implementation into a whole engineering course exhibits several drawbacks that should be considered. Traditional teaching and lecturing is necessary to avoid skipping fundamental knowledge and to acquire it hierarchically when necessary. An interesting dissertation about benefits and drawbacks of partially and overall implementation of these methodologies can be found in the work of Perrenet et al (2000). There are also examples of partially introduced PBL to some Mechanical Engineering subjects (Hadim and Esche 2002), and how it reduces the amount of traditional lecturing, moving topics from traditional learning to PBL. This paper describes the contents, purpose, methodology and results of this innovative teaching in Structural Analysis and Experimental Structural Analysis subjects at the Universidad of Sevilla, which corresponds to third and fifth year of Mechanical Engineering course, respectively. The introduction of this kind of teaching serves as a basis for the implementation of new teaching methodologies that prepare students for lifelong learning, according to the new European Higher Education Area: problem and project-based learning (PBL), cooperate learning, cognitive apprenticeship, learning how to learn, and promoting transversal skills such as work in a team and writing and oral communication abilities (Hadim and Esche 2002; Dunlap and Grabinger 2003; Frank et al 2003). STRUCTURAL ANALYSIS SUBJECT: PRACTICAL CLASSES AND PROBLEM-BASED LEARNING In third year of the Mechanical Engineering course, students learn the basic concepts of Structural Analysis, including the flexibility and stiffness methods and how to use them to calculate the displacements and stresses structures undergo when they are subjected to their design loads. Before this new teaching experience was introduced, students who passed this subject seemed to be ready to start to study more complex issues such as instabilities and dynamics and to understand the formulation of the finite element model. However, students did not have the impression that the knowledge they had gained would be useful to design, analyze and build a real structure. To change this perception, two series of practical classes were introduced: a computer class and a laboratory class. In the computer class, students use a computer program to analyze the steel frame of an industrial building using the stiffness method. In the laboratory class (Fig. 1), students test and measure displacements and stresses in a small steel truss when it is subjected to a known force. Moreover, students compare the data measured experimentally with the values they can predict when using the Structural Analysis methods they have learnt. This shows them that the actual behavior of the structure matches the theoretical concepts they learned earlier. However, to further complete the teaching, a third practical class was introduced. In this class, students have to design, analyze, build and test a structure made of wooden popsicle sticks. Each group of two students is only required to fulfill a certain objective with the structure. The rest of the parameters are free and designed by the students themselves. For example, the first year this methodology was used, the building had to bridge a span of 50 cm (Fig.2), and a point load is applied at the middle of the span. The second year, a 50cm long cantilever type structure had to bear a load located at its free end point (Fig. 3). The third year, the structure had to cover a square space of 400x400mm, simply supported at its four corners, and a uniform load was applied over the structure (Fig. 4). Similar PBL experiences have been developed using either wooden sticks, cardboard or even realistic structural elements for a real structure. There are also interesting previous experiences that are limited to the design and analysis stages of an engineering project, including the analytical and numerical approach of the problem but not the building stage (Hadim and Esche, 2002). This PBL makes students face the kind of problems they may encounter when they design a structure as professionals. These problems range from not having all the data available to how to join bars correctly to prevent the joints from being the weakest points in the structure. At this stage of their training, students are not familiar yet with the instability problems structures may have. Yet, they have to solve problems with bars whose compression stress can cause buckling and that require sections with a greater radius of gyration to avoid buckling. They also have to deal with the three dimensional nature of the structure, despite they have analyzed a simplified two dimensional model of the structure, as it is usual in a professional design. Therefore, they have to introduce additional bars in order to avoid an unstable response due to the effects of geometric and load irregularities. Each group of two students analyzes, builds and tests the structures, with the continuous assistance of the teachers of the subject, which fosters technical discussions. Once the students agree on the type of structure they want to design to solve the problem, they start to make their calculations, which sometimes force them to change the type of structure they had planned. Once they have designed and analyzed the structure, they are provided with the building materials: wooden sticks, glue and, for those who need them, wires that are used as tie rods in the structures. The mechanical properties of such materials are available and the students also have the choice of performing a bending test or compression test on any type of bar they design. The material in the laboratory is available to the students for building the structure. Once the structure is ready, students have to submit a report on the project explaining the design, calculation and building process. They estimate the breaking load of the structure based on the results obtained with a computer program using the stiffness method. The report has to be defended in front of the teachers of the subject before the test that will lead the structure to collapse. The practical class assessment is determined by the design of the structure, the ratio between the breaking load and the weight of the structure, and the ratio between the actual breaking load and that predicted by the students according to their calculations. With this PBL methodology, students apply prior knowledge and acquire new knowledge that would be otherwise out of the scope of the subject. They also get some additional and important skills, such as knowledge management, and a social constructivism learning approach (Krajcick et al 1999; Frank et al 2003) is also achieved. Each group of two students designs, analyzes and builds their own structure, but knowledge and information is not only shared between those two students but also between other groups. There are spontaneous technical discussions between different groups of students, and teachers are usually required to take part in them, although teachers usually encourage students to discuss between them and try to solve the technical difficulties following their own criteria, giving them as less information as possible to avoid erroneous conclusions. The accuracy and depth of the explanations given by teachers to each group depends on the requirements and the level of knowledge reached by the group. Therefore, students learn how to identify available information, select useful information and store it, develop knowledge from the information given and transfer it when necessary. Overall, participation of students in this practical class also provides them with valuable training in additional skills such as project and time management since the process of designing and building the wooden structure is quite similar to a small-scale real engineering project. In addition, the written report and its oral presentation help students improve their written and oral communication skills. It must be pointed out that this PBL methodology also implies a considerable teaching load for teachers. An average time of 3 hours of assistance is required for each group of students, who ask teachers for help as they need it. Structures are tested at the end of the year; each test takes about half an hour. These scheduled tests are currently the only amount of time that is officially recognized as a teaching work, since assistance to students is officially considered as part of the general support time that teachers must devote to all their students. This means that, overall, teachers must currently spend extra time equivalent to 50% of officially recognized time. Fortunately, this situation will be at least partially corrected with the new EHEA, which promotes and recognizes this kind of teaching methodology and the student support it requires. Results of surveys conducted by the Universidad de Sevilla on this subject in 2009 and 2010 are included in Table 1. Results of the subject Structural Analysis are compared to those of the overall subjects of the Structural Analysis Department, the whole Mechanical Engineering course and the whole University. It can be observed that the evaluation of the subject is satisfactory when compared to other subjects. Unfortunately, no results prior to the implementation of the PBL methodology are available to analyze the change brought about by this methodology in students’ perception of the subject. In 2010, the evaluation of the subject was less favorable, especially in aspects related to office hours and organization of the subject. This was due to the fact that there were fewer human resources for that year and teachers had to spend too much time preparing and organizing the practical lessons of the subjects Structural Analysis and Experimental Structural Analysis. Thus, it was difficult for them to assist all the students as they required. Fortunately, additional human resources are available for year 2011 and better programming and schedules have been designed by learning from previous experience, so better results than those of 2010 are expected. These results suggest that this kind of teaching requires a special dedication to lectures, office hours, practical lessons and close contact with students, hence why teaching evaluation results are more sensitive to the available human resources than classical teaching. Results obtained with this PBL methodology have been very good. Although PBL may not improve exam scores, an increase was observed both in the rate of students that passed the exam and the exam scores of the students that participated in the PBL methodology, which is optional for them for now. The PBL methodology may not be suitable for every student (Rosenfeld and Rosenfeld 1999). Therefore, the practical class may give students with lower grade results in regular studies the opportunity to improve Grade Point Average (GPA), whereas it does not affect negatively the GPA of students with usual higher grade results. Table 2 includes pass rates and GPA for students that participated and did not participate in the PBL approach. GPA was evaluated from 5 to 10 points, with 5 points meaning passing the exam. Data correspond to the years the authors have been involved in this subject (2008 to 2011). The PBL methodology was first introduced in 2009. The table shows that exam scores remained similar for students that did not participate in the third practical lesson, whereas much better results were observed for students that took part in it. Moreover, students participating in the project get involved to such an extent that many of them feel encouraged to specialize in Structural Analysis. This encouraging effect has also been noticed in previous PBL teaching experiences (Frank et al 2003). In their specialization in fourth and fifth year, students learn the dynamic behavior of structures and instabilities, specific types of structures such as plates and laminar structures, and structural materials such as steel and concrete. Finally, before completing their Mechanical Engineering studies, students are exposed again to a project-based teaching methodology in the subject Experimental Structural Analysis. EXPERIMENTAL STRUCTURAL ANALYSIS Various teaching and assessment systems have been used in the subject Experimental Structure Analysis since it was included in the curriculum. Yet, it has always focused on PBL methodology. It is a last-year subject aimed to teach specialized practical knowledge, based on the concepts learned earlier in other subjects of the same area of knowledge. This prior knowledge and the maturity of students in the final years of the course make it easier to implement the teaching methodology of the subject. Moreover, the in-person 45 hours of the subject are divided into 15 hours of theoretical classes and 30 hours of practical classes which are organized for groups of a maximum of four students. This experimental and practical teaching approach is suitable for applying PBL. The teaching methodology used has always been similar. Yet, there have been changes in the organization of the work students have to do, with variations in the approach and the assessment methods. These changes have been aimed at enhancing the achievement of the objectives planned but are also necessary to keep teachers stimulated and motivated, even though these changes require an additional effort from them. There are approximately 3 practical lessons that change from one year to another, and it is estimated that nearly 30 hours are needed for a teacher to appropriately set up a new practical lesson. Preparation work includes acquiring the necessary materials (sensors, software, wires, probes, etc.), developing the necessary software applications, performing trial tests, analyzing the experimental results and finally setting the objectives and planning the activities for the practical lesson when performed by the students. Changes in the practical lessons from one year to another also prevent students from copying materials, results and experiences from students of previous years, which would hamper the development of the subject and undermine the credibility of students’ work. Initially, students in the practical class had to prepare a short research project on the behavior of a single structural element during the school year: reinforced concrete beams externally strengthened with strips of Carbon Fiber Reinforced Polymer (CFRP, Fig. 5). The work included various types of tests, instruments, and so on. The purpose of this methodology was to get students to complete a long-term project during the whole school year applying prior and new knowledge to study and analyze a new problem for them and draw conclusions about it. This involved facing situations of uncertainty and risking making mistakes in a new endeavor. At the end of the year, students had to present a written report on the work performed and present it publicly in front of the teachers. This original approach received great interest and made it possible to organize the content of the subject, a complex task given that it was the first time it was going to be taught. Changes in the practical class were subsequently made to obtain better performance, motivation and learning in students. A series of independent practical assignments were chosen to reward regular work by the students, illustrate theoretical contents and consolidate the most important ideas related to the subject. This change also addressed the students’ request to have greater order and regularity in the work performed during the year, which implied having ongoing assessment. Various practical exercises have been performed over the years. In the practical classes, each student develops his or her skills in the laboratory. The aim is to deal with most of the elements one may face in experimental structural analysis: programming languages (LabView and Matlab), functioning and use of sensors (displacement sensors, strain gages, accelerometers, geophones, laser vibrometers), characteristics and setup of data acquisition systems and testing machines, test design and assembly, and even participation in tests on real structures (dynamic behavior of bridges, vibration from rail and road traffic, etc.). As an additional activity, there are field visits to companies and facilities related to the structures insofar as possible. Some of the contents of the different practical lessons that have been done in the subject are listed below: Installation of strain gages on steel and concrete specimens (Fig.6 and Fig. 7) Assessment of the constitutive law of concrete, steel, marble, polymers, etc, through tensile or compression tests, measuring strains with strain gages and displacement sensors. Analysis of the operation of displacement sensors and calibration according to a reference sensor. Analysis of the operation and use of a universal testing machine, simplified calibration of displacement and force measurements. Analysis of the flexural behavior of concrete beams, CFRP reinforced concrete beams and steel beams, including displacements, strains, curvatures and bending moments (Fig. 7). Experimental analysis of a truss, measuring strains, displacements and forces Use of accelerometers and geophones. Obtaining accelerations from velocities through integration of filtered acceleration signals. Modal analysis of concrete and steel beams Vibration based damage detection in a steel beam with a simulated crack Modal analysis of a simple structure (steel beam) under a moving load (Fig. 8) Operational modal analysis of one of the bridges crossing the Guadalquivir River, Fig. 9 and. 10 Analysis of natural frequencies and mode shapes of progressively cracked reinforced concrete beams (Fig. 11) To date, the subject includes twelve laboratory work sessions conducted in small groups of a maximum of four students. This is essential for successful involvement of students in the laboratory work and understanding of the contents taught. After this, each group of four students is divided into two groups of two, so each pair of students prepares reports on the work performed every week, and the contents of these reports are orally presented and discussed with the rest of the students. Before the oral presentation, they must send an electronic version of the written report to the teachers. At the beginning of the school year, teachers give students a model outline for the reports. This outline consists of the following items: introduction, fundamental or theoretical aspects, experimental setup, results, discussion and conclusions. From that point, the contents and style of the written reports are designed by each group of students, according to the experimental data and notes that they take during the practical lessons. For the oral presentations, a projector and a blackboard are available to the students. Each group of two students has 15 minutes for the presentation, and 5 additional minutes are allocated for answering questions from teachers or for discussion with the rest of the students. During these oral sessions, teachers give students advice about the contents and style of the written reports and oral presentations. The order in which the groups make their presentations is changed from one week to another, so no group benefits from systematically speaking before or after another group. Hence, the practical classes, preparation of reports and oral presentation of the work done are aimed at strengthening students’ skills in oral and written expression, teamwork, analysis, synthesis, self-criticism and knowledge management, apart from the learning of contents directly related to the subject. The subject is therefore divided into several small inquiry-based learning units (Tamir 1990, Frank et al 2003), in which students are supported by teachers and their teammates to solve and interpret a real problem by themselves, once the problem is outlined in a practical class. Although assessment is ongoing, students also have a written exam, which includes questions on the theoretical content of the subject and the work performed in the practical sessions. The exam is usually simple (the theoretical content of the subject is not long or complicated) and only takes one hour. The grade obtained in the exam represents 30 percent of the final grade; the remaining 70 percent is given by the grade obtained in the practical exercises. The assessment of the subject also includes a self-assessment system to verify the degree of agreement between the grades given by the teachers and those proposed by the students. In this self-assessment system, students propose a grade for themselves and the rest of their fellow students in the practical classes, whose work they are very familiar with. The result of this self-assessment experience has been positive, with deviations typically less than one point compared to the grades proposed. Grades given by teachers in the practical sessions usually match those proposed by the students. There are plans to use the self-assessment system so that students can qualify the grades in the near future; the aim is to use grades given by students to modify those proposed by teachers, rewarding students who have worked the most and penalizing those who have worked less, according to the students’ criteria. Eight years after this subject with this PBL methodology was first introduced, results can be considered excellent, with high ratings from students and teachers. Surveys have been conducted at the end of each academic year on the quality of the teaching (organization of the subject, theoretical and practical contents, assessment system, teacher assessment, etc.) and the evaluation of the subject from students is excellent. Table 3 includes a summary of the results of the surveys. Each item of the table is rated by each student from 0 (worst) to 10 (best). The table includes the corresponding average value obtained for each item and for each year. According to the surveys, students spend around 60 hours to prepare the reports (5 hours each report) and 10 hours to prepare the written exam. That makes a total of 115 hours, including the attendance to in-person classes. This a slightly bigger amount of the estimated dedication of 87.5-105 hours according to the European Credit Transfer and accumulation System (ECTS) established in the Universidad de Sevilla. Nevertheless, results of the surveys show that students welcome this type of learning, even if it requires greater effort and dedication from them. CONCLUSIONS This paper presents the results of an innovative teaching experience in the area of structures in the Mechanical Engineering course of the Universidad de Sevilla. The teaching methodology used is aimed at motivating students to learn through practical experiences that introduce cross-cutting issues in the training of students. Students respond very positively to this kind of teaching. Teachers feel motivated and satisfied with the use of these new methodologies, in spite of the time it takes to put them into practice. Moreover, teachers receive continuously new ideas; they also become lifelong learners and enjoy a better working environment with students (Krajcick et al 1999). Applied teaching methodologies are also appropriate in the European Higher Education Area. However, given the effort this type of methodologies requires from teachers, they can only be implemented in small groups of students. This is the case of Experimental Structural Analysis, a last-year subject, but not of Structural Analysis, a compulsory subject, where it was only possible to implement this methodology as voluntary additional work. To generalize this type of methodology as compulsory work, it would be necessary to increase the human and economic resources available to teach the subject. Such an increase would be fully justified considering the improvement in the quality of teaching provided by these experiences. However, a suitable proportion of traditional lecturing should be kept to hierarchically acquire the necessary fundamental knowledge in depth (Perrenet et al 2000). REFERENCES Aparicio, A.C. and Ruiz-Teran, A.M. (2007). "Tradition and Innovation in Teaching Structural Design in Civil Engineering." J.Profl.Issues in Engrg.Educ.and Pract., 133(4), 340-349. Dunlap, J.C. and Grabinger, S. (2003). "Preparing Students for Lifelong Learning: A Review of Instructional Features and Teaching Methodologies." Performance Improvement Quarterly, 166-25. Elazouni, A.M. and Raslan, M.S. (2003). "Footbridge: Project to Implement Management Functions at AASTMT." J.Profl.Issues in Engrg.Educ.and Pract., 129(1), 44-51. European Commision (2004). European credit transfer and accumulation system (ECTS). Key features, Office for Official Publications of the European Communities, Luxembourg. Galvín, P. and Domínguez, J. (2007). "Dynamic analysis of a cable-stayed deck steel arch bridge." J. Const. Steel Res., 63(8), 1024-1035. Hadim, H. A. and Esche, S.K. (2002), “Enhancing the engineering curiculum through project-based learning.” Proc. 32nd ASEE/IEEE Frontiers in Education Conference, ASEE/IEEE, Boston. Frank, M., Lavy, I. And Elata, D. (2003), “Implementing the Project-Based Learning Approach in an Academic Engineering Course.” International Journal of Technology and Design Education, 13, 273–288. Glynn, E.F. and Fergusson, W.B. (1994). "Innovative Introduction to Civil Engineering Curriculum." 16 Fig. 5. Placing the layer of carbon fiber on the reinforced concrete beams 17 Fig.6. Placing a strain gage on a concrete test specimen 18 Fig.7. Placing strain gages on a steel beam and its subsequent bending test 19 Fig.8. Identification of the modal parameters of a structure under the effect of a moving load 20 Fig. 9. Dynamic identification of a real structure with GPS-synchronized accelerometers 21 Fig.10. Measuring vibrations caused by road traffic on a bridge 22 Fig.11. Applying damage detection techniques to CFRP reinforced concrete beams with external reinforcements 23 Tables Subject Department Course University 2009 2010 2009 2010 2009 2010 2009 2010 Organization of teaching, contents and objectives of the subject 4,67 3,96 3,84 3,75 3,74 3,69 3,83 3,80 Teaching assistance in office hours 4,87 4,00 3,74 3,67 3,76 3,66 3,84 3,79 Schedule of office hours 4,67 3,50 3,43 3,44 3,45 3,35 3,60 3,57 Clarity of the lectures and explanations 4,75 4,03 3,55 3,54 3,53 3,49 3,67 3,66 Interest of the teacher about the understanding of the students 4,81 4,43 3,61 3,59 3,60 3,52 3,74 3,72 Use of realistic applications to explain the subject 4,69 4,23 3,67 3,64 3,71 3,65 3,84 3,82 The teacher gives useful and helpful information when students ask for it 4,75 4,43 3,81 3,79 3,87 3,80 3,94 3,91 The teacher promotes good work environment in the classroom 4,75 3,80 3,31 3,30 3,29 3,24 3,56 3,56 The teacher motivates the students 4,56 3,69 3,28 3,28 3,19 3,16 3,41 3,42 The teacher is respectful towards the students 4,81 4,27 4,11 4,14 4,21 4,15 4,26 4,25 Assessment methodology and criteria 3,94 3,48 3,45 3,34 3,28 3,23 3,51 3,54 Overall evaluation of the teacher 4,69 4,03 3,62 3,57 3,57 3,52 3,72 3,71 Table 1. Results of surveys for performed by the Universidad de Sevilla for Structural Analysis subject. Each item is rated by each student from 0 (worst) to 5 (best). 24 Year Without PBL With PBL Pass rate GPA 5-7 GPA 7-9 GPA 9-10 Pass rate GPA 5-7 GPA 7-9 GPA 9-10 2008 42 85 13 1 -- -- -- -- 2009 40 70 19 4 63 53 41 4 2010 46 91 9 0 71 47 38 16 2011 36 91 9 0 55 52 41 7 Table 2. Percentage of pass rates and different GPA ranges for students that participate and do not participate in the PBL approach. 25 Year 2003 2004 2005 2006 2007 2008 2009 2010 2011 Nº. Students 16 6 22 38 20 16 16 16 8 Subject contents 7,9 8,7 8,7 8,1 8,2 7,9 8,7 8,4 8,5 Organization 8,2 9,5 8,8 8,6 8,4 8,6 8,9 8,2 8,8 Interest of class 8,8 9,3 8,7 7,5 8,5 7,6 8,3 8,2 8,9 Assessment system 8,9 8,8 8,3 8,1 8,6 8,4 8,1 7,8 8,0 Clarity of the explanations of the teacher 8,9 9,0 8,5 8,3 8,7 8,9 9,2 8,7 9,3 Overall assessment of the teacher 9,0 9,7 8,9 8,7 8,7 8,9 9,4 9,0 9,3 Overall assessment of the subject 8,3 9,0 8,5 8,2 8,6 8,5 8,8 8,3 8,3 Table 3. Survey results for the subject Experimental Analysis of Structures. Each item is rated by each student from 0 (worst) to 10 (best)