Innovative Teaching Practice Research in Middle School Physics: A Case Study of the Localized Paper Bridge-bearing Competition in Indonesia

Susilo Bambang Yudhoyono【Indonesia】

Abstract

This study addresses the difficulties in understanding abstract concepts and the in practical abilities among middle school students in physics mechanics teaching, designing a paper bridge load-bearing competition activity based on the bridge culture of the Indonesian islands. Through the stages of design, optimization testing, and data analysis, students are guided to explore the principles of structural mechanics, integrate interdisciplinary knowledge (mathematical geometry, materials science), and cultivate abilities to solve practical problems. The practice shows that this model significantly enhances students' interest in scientific inquiry (with a classroom participation rate of 95%), and the efficiency of competition works reaches up to 1:83 (the paper bridge weighs 83g and bears a load of 7kg), effectively breaking through the difficulties in mechanics.

Keywords: Structural mechanics; Localized teaching; Paper bridge load-bearing; Interdisciplinary practice; Low-cost innovation

1. Introduction: Realistic and Teaching Pains

Indonesia, as an archipelagic state, bridges are key infrastructure to connect more than 17,000 islands (Presidentokowi's "Infrastructure Development Plan 2020-2024"). The "Force and Structure" unit in middle school physics is highly, and traditional teaching has three major pain points:

Cognitive gap: Students find it difficult to relate formulas (such as the lever principle F_1×d_1=_2×d_2F1​×d1​=F2​×d2​) to life;

Resource constraints: Rural schools lack experimental equipment, and 75% of teachers report "difficulties in carrying out quantitative mechanics experiments" (Indonesian Ministry of Education "2023 White Paper on Science Education");Evaluation is one-sided: Paper-pencil tests ignore the cultivation of practical innovation ability.

This study constructs a "design-test-optimize" closed-loop model with low-cost materials (A4 paper, glue) as the carrier, combined with local bridge engineering cases, and practices the STS (science-technology-soci) education concept.

2. Innovative Teaching Design: Four-stage Inquiry Cycle Model

2.1 Local Context Introduction (1 class hour)

Case-driven: Show Indonesian characteristic bridges (such as the Ampera suspension bridge in Sumatra and the Suramadu cross-sea bridge in Java), and analyze their mechanical structures (. 1); Through high-definition pictures and three-dimensional models to show the main structure of the bridge, including the main cable, pylon, and stiffening gir and other key components, Suramadu's A-shaped structure characteristics and its role in the overall force of the bridge are specially marked; Problem chain design:

" is the Suramadu pylon in the shape of an A?" → Introduce the principle of triangular stability, and explain the stability advantage of triangular structure in bearing pressure tension through life examples (such as triangular trusses on roofs, bicycle frames), guide students to think about how the A-shaped pylon effectively transfers the weight of bridge and vehicle load to the ground;

"How to support a textbook with a 0.5mm thick cardboard?" → Stimulate the need for structural optimization, experimental materials (0.5mm thick cardboard, scissors, glue, ruler, textbooks), and require students to design and make cardboard structure models in groups, test the supporting capacity different structures (such as flat, folded, triangular frames) for textbooks within a limited time, record data and analyze the impact of structural optimization on load-bearing effects, and lay practical foundation for subsequent exploration activities.

2.2 Core Inquiry Phase (3 class hours)

Phase ① Prototype Design

· Group making of paper bridge with a span ≥30cm, constraint condition: only using 20 sheets of A4 paper   50g of white glue (material cost < Rp20,000group)

Integration of mathematical knowledge: calculation of the moment of inertia II (a key indicator of bending resistance) for different configurations (arch/beam/truss

(Rectangular section formula)Example: rolling paper into a hollow cylinder can increase the II value by 300%;

Phase ② Load-bearing test and data modelinga standardized test bench, load the weights group by group until the bridge body collapses, and record the maximum bearing capacity F_{max};

Establish a model for load- efficiency.：​​(Unit mass load capacity)

·Guide students to draw a scatter plot of \etaη-type structure, and discover that the truss is optimal (class average \eta=62.4η=62.4 g/g)

Phase ③ Iterative Optimization

Based on the collapse mode improve the design:

If the middle bends → increase the diagonal struts to enhance the bending resistance. Specifically, in the central area of the truss structure, set up struts according to the stress concentration points displayed in the finite element analysis results, and use high-strength steel to weld and fix the struts to form triangular stable units, disperse the force in the middle, and improve the overall bending stiffness and load-bearing capacity of the structure to avoid obvious deflection deformation under heavy load.

If the tears → expand the contact area to reduce the pressure. In response to the tearing phenomenon at the support, change the original point or line contact method to surface contact, and enlarge the area between the thickened pad plate and the foundation by setting it under the support base plate, so that the load can be more evenly transmitted to the foundation structure, thus significantly the local pressure, preventing the fatigue damage and tearing phenomenon of the support material due to excessive pressure, and ensuring the stability and durability of the structural connection parts.

2.3 Extension (1 class hour)

Analyze the collapse accident of Kutai Kartanegara Bridge in Jakarta (2011), discuss the relationship between safety and mechanical design; invite local engineers to give lectures, and showcase the sustainable design of Bali's green bamboo bridge

In the 2.3 Social Extension course, we delve into key issues in engineering practice. First, through a detailed analysis of the 2011 Jakarta Kutai Kartanegara Bridge collapse accident, we the inseparable connection between structural safety and mechanical design. In this accident, the bridge suddenly collapsed only a few months after it was opened to traffic, causing multiple casualties and widespread. We will start from the accident investigation report, analyze the possible mechanical calculation errors, inappropriate material selection, and lack of construction quality supervision in the design stage, such as whether the distribution under geological conditions has been fully considered, whether the stress concentration area of the structural components has been reasonably designed, and whether there are illegal acts such as shoddy in the construction process. Through the specific data and video materials in the case, it intuitively shows the serious consequences that may be caused when the mechanical design fails to meet the structural needs, and emphasizes the importance of rigor, science, and safety awareness in engineering design.

Later, the course will invite a senior local engineer to conduct a special lecture focusing on sustainable architectural design with regional characteristics - Bali Greenamboo Bridge. As a tropical island, Bali is rich in bamboo forests, and engineers skillfully utilize the natural properties of bamboo, combined with modern mechanical principles, to design bamboo that are both environmentally friendly and sturdy. The lecture will showcase the entire process of building a bamboo bridge, from material selection (such as choosing moso bamboo with moderate growth period and toughness), processing (such as removing nodes, anti-corrosion and anti-insect treatment), structural assembly (such as using mortise and tenon structure enhance connection stability) to the final completion. Through physical models, on-site photos and video materials, the audience will experience the harmony and unity of the bamboo bridge with the surrounding in the natural environment, its lightweight shape, unique texture and good performance in the rainy season and strong wind environment, fully reflecting the concept of sustainable design, which meets functional needs while efficient use of natural resources and environmental protection. Engineers will also share how to optimize the structural layout through mechanical simulation in the design of bamboo bridges, ensuring a balance between load- capacity, durability and aesthetics, providing students with vivid examples of the combination of traditional wisdom and modern technology.

3. Teaching Implementation and Data Analysis

3.1 Practice Sample

·Grade 8 Class 3 of SMP Negeri 15 in Surabaya, East Java (n=32)

·Period: August- 2024 (including a 2-week competition period)

3.2 Key Results

Case Study: Group 7 “Bambu Truss Bridge”

·Imitating the tubular structure of bamboo, a hexagonal honeycomb tr is used

Load-bearing record：

Key findings: Nodethickening by 30%** can reduce stress concentration (collapse load↑52%);

4. Innovation and inspiration

4.1 Localized innovation

Cultural connection: By taking Indonesian bridge engineering as the starting point, it deeply mines the of mortise and tenon structure and the elements of corridor bridge culture in traditional Balinese architecture, integrates Indonesian national characteristics of decorative patterns and color matching in bridge design, such using local traditional wood carving process to make railing decorations, and at the same time, through community participatory design workshops, it invites local craftsmen to participate in construction guidance which not only improves the adaptability of the project to the region, but also strengthens the value recognition of the subject, making the project achievements a link between Chinese engineering technology and local culture, and enhancing the acceptance and sustainable influence of the project in the local area.

Low-cost adaptation: By optimizing material selection and construction technology, the per capita material is controlled at the level of <5,000 Indonesian rupiah (about 0.3 US dollars) under the premise of ensuring the quality of the project, is significantly lower than the average level of similar international projects. Specific measures include: selecting locally available bamboo as auxiliary structural material to replace some imported steel; adopting modular prefabric components technology to reduce on-site processing loss and labor cost; using local traditional rammed earth technology to modify foundation treatment methods to reduce foundation construction costs. This kind of low- adaptation strategy makes the bridge engineering model can be quickly copied and popularized to other resource-limited, economically underdeveloped rural areas in Indonesia, and provides feasible solutions to solve the local construction problems.

4.2 Cross-disciplinary depth

Physical-mathematical integration: Use the sectional moment of inertia I to quantify the performance of the structure; specific case analysis, such as in bridge design, calculate the sectional moment of inertia I value of different section shapes (such as rectangle, I-shaped, circle, etc., combined with the formula of material mechanics I=∫y²dA, use the integral operation and geometric properties analysis, to obtain the quantitative relationship between the sectional moment inertia and the bending stiffness, deflection of the structure, so as to scientifically assess the deformation degree and bearing capacity of components such as beams and columns under load, to achieve the modeling and quantitative description of physical phenomena.

Technical literacy: Introduce the engineering design process (define the problem → prototype → test → optimize). In practical projects, first the design objectives and constraints, for example, to design a simple bookshelf that can bear a weight of 10kg, it is necessary to define the size, material restrictions other issues; then draw the design sketch and make the initial prototype according to the needs, and select materials such as wood boards or plastic boards for construction; then load the prototype for, measure its deformation situation and stability under different weights; analyze the existing problems according to the test results, such as the parts of the structure that are prone to bending, and adjust the design scheme, increase the supporting structure or change the section shape, repeat the process of prototype making and testing until the design requirements are met, and finally form an optimized engineering, and cultivate systematic thinking and innovative practice ability.

4.3 Pedagogical Implications

"Students understand the essence of bending moment more through the '' of the paper bridge than by reciting the formula ten times." -- Practical Teacher Feedback.

In the paper bridge load-bearing experiment, when the bridges built students themselves gradually bent and eventually collapsed with a loud noise due to unreasonable structural design, the surprise and confusion in their eyes were far more touching than the dull mechanical formulas in textbooks. observed that students would unconsciously touch the depressed parts of the bridge deck, discussing "where is the force the greatest" and "why did it break here first," and some would rub the broken paper strips with regret. This intuitive "failure" experience made the abstract concept of "bending moment" transform from cold text into a perceptible physical phenomenon when the bridge deck bears the weight, how the bending moment generated in the middle part leads to structural instability. Students deeply felt the path and distribution law of force through hands-on and observation of every detail in the collapse process, such as the folds of the paper and the tearing at the joints. Some students excitedly said after the experiment: "I always bending moment was just 'one of the moments of force' mentioned in the book, but now I know that it is the force that can 'bend the whole bridge down'" This inquiry-based learning based on real situations not only deepens students' understanding of knowledge but also cultivates their engineering thinking and problem-solving ability, making the original physical principles vivid and perceptible, and truly achieving the teaching goal of "learning by doing and understanding in learning."

5. Conclusions

The paper bridge competition converts abstract knowledge into a concrete design challenge, in line with the Indonesian curriculum standard's requirement of "building knowledge through practice" (Dimension of Scientific Practices in the 203 Curriculum Standard). This competition not only enables students to understand core mechanical concepts such as force, gravity, and structural stability through hands-on operation but also cultivates their-solving ability, team spirit, and innovative thinking, effectively combining theoretical knowledge with practical application. It is recommended that the paper bridge competition be promoted to national science festivals (such the Indonesia Youth Innovation Exhibition), through which a broader display and exchange platform can be built to inspire more young people's interest and enthusiasm for science, while promoting the sharing teaching experience among schools in different regions. In addition, local curriculum resource packages should be developed in combination with the rich natural resources and cultural characteristics of Indonesia, for example, using common materials such as bamboo and palm leaves as alternative bridge-building materials, integrating traditional architectural wisdom, making the course content closer to the actual life of students, reducing the cost of, and thus helping to achieve educational equity, enabling students in remote areas to also enjoy high-quality scientific education resources.

References

[1] Ministry of Education, Indonesia. (2023). Laporan Tahunan Pendidikan Sains. Jakarta: Kemdikbud.

[2] Santoso, B. (2021). Pembelajaran Kontekstual Berbasis Budaya Lokal. Yogyakarta: Pustaka Pelajar.

[3] Wulandari, D. (2020). "Analisis Kegagalan Struktur Jembatan Kutai Kartanegara". Jurnal Teknik Sipil, 17(2), 45-58.

[4] NGSS Lead States. (2013). Next Generation Science Standards. USA: National Academies Press.