📚 Case Study Practical Exercise: Year 7 CCEA Engineering | 案例分析实战演练：7年级CCEA工程
In this case study, we will work through a typical Year 7 engineering design challenge set by CCEA. You are asked to design, build and test a model bridge that can span a 30 cm gap and support a 500 g mass. Through this practical exercise, you will apply the full engineering design process and learn key principles of structures, materials and teamwork.
在这个案例分析中，我们将完整体验一项典型的CCEA七年级工程设计挑战。任务要求你设计、制作并测试一座能够跨越30厘米间隙并承重500克的模型桥。通过这一实战演练，你将应用完整的工程设计流程，并学习结构、材料及团队合作的关键原理。
1. Understanding the Design Brief | 理解设计概要
The first step is to read the design brief carefully. You must bridge a 30 cm gap using only 30 plastic straws and adhesive tape. The bridge must support a 500 g weight without collapsing.
第一步是仔细阅读设计概要。你必须只用30根塑料吸管和胶带跨越30厘米的间隙。桥梁必须能承受500克重量而不倒塌。
Key constraints include the limited number of materials and the requirement that the bridge rests on the edges of the gap without being attached to the floor.
关键限制包括材料数量有限，以及桥梁必须放置在间隙的边缘上，不能固定在地板上。
2. Research and Investigation | 研究与调查
Before starting to build, you need to research how real bridges work. Look at beam bridges, truss bridges and arch bridges. Notice that many strong structures use triangles to prevent deformation.
在动手建造之前，你需要研究真正的桥梁如何工作。观察梁桥、桁架桥和拱桥。注意许多坚固的结构都使用三角形来防止变形。
Investigate the properties of your materials: straws are light and flexible but can buckle under compression; tape can join straws but has limited strength in tension.
调查你的材料特性：吸管轻巧柔韧但受压时容易弯曲；胶带可以连接吸管，但抗拉强度有限。
3. Generating Initial Ideas | 产生初步想法
Sketch at least two different bridge concepts. One could be a simple beam bridge reinforced with straws underneath; another could be a truss bridge with side frames made of triangles.
至少画出两种不同的桥梁概念草图。一种可以是下方用吸管加固的简单梁桥；另一种可以是侧面框架由三角形构成的桁架桥。
Label the parts and think about where the load will be applied. The goal is to distribute the force evenly across many straws.
标注各部分，并思考荷载将加在哪里。目标是让力均匀分布在许多吸管上。
4. Selecting the Best Solution | 选择最佳方案
Compare your ideas against the design criteria: span, load capacity, material limit, and ease of construction. A truss design is often stronger because triangles convert bending forces into tension and compression along the members.
将你的想法与设计标准进行对比：跨度、承载能力、材料限制以及施工难度。桁架设计通常更坚固，因为三角形能将弯曲力转化为杆件内的拉力和压力。
Choose the design that you predict will perform best, and justify your choice with reasoning.
选择你预测性能最佳的设计，并用理由说明你的选择。
5. Planning and Materials | 规划与材料
Count exactly how many straws and how much tape you need for each component. A full-length straw is about 20 cm, so you may need to join straws to make longer beams.
精确计算每个部件需要多少根吸管和多少胶带。一根完整的吸管长约20厘米，因此你可能需要连接吸管来制作更长的梁。
Draw a scaled plan of your bridge with dimensions. This helps to avoid wasting materials.
按比例绘制你的桥梁图纸并标注尺寸。这有助于避免浪费材料。
6. Building the Prototype | 制作原型
Cut straws to the required lengths and join them with tape to form the truss sides. Then connect the two sides with cross members to make a 3D structure.
按所需长度剪裁吸管，用胶带连接形成桁架的侧面。然后用横向构件连接两侧，制成三维结构。
Remember to reinforce joints, as they are often the weakest points. Use multiple wraps of tape or gusset plates made from straw segments.
记得加固节点，因为它们通常是最薄弱的地方。可多缠几圈胶带或使用吸管段制作的角板进行加固。
7. Testing the Structure | 测试结构
Place the bridge across the 30 cm gap and gradually apply the load. Start with a small mass and increase until you reach 500 g or failure occurs.
将桥放在30厘米间隙上，逐渐施加荷载。从小质量开始，逐渐增加，直到达到500克或发生破坏。
Observe how the bridge deforms. Do straws bend, twist or snap? Note which joints fail first. This data is vital for improvement.
观察桥梁如何变形。吸管是弯曲、扭转还是断裂？记录哪些节点首先失效。这些数据对改进至关重要。
8. Evaluating and Improving | 评估和改进
After testing, evaluate your design against the original criteria. Did it support 500 g? Did it span the gap without touching the bottom? If not, identify weaknesses.
测试后，对照原始标准评估你的设计。它是否承受了500克？是否跨越间隙而不触及底部？如果没有，找出薄弱环节。
Propose improvements: you might add more triangles, use different jointing methods, or change the shape of the deck. Sketch a revised design.
提出改进建议：可以增加更多三角形，使用不同的连接方法，或改变桥面的形状。画出修改后的设计草图。
9. Real-World Connections | 现实世界联系
Engineers use similar processes when designing real bridges like the Foyle Bridge in Northern Ireland. They test small-scale models and use computer simulations to predict behaviour.
工程师在设计现实中的桥梁（例如北爱尔兰的福伊尔桥）时，也会使用类似的流程。他们测试小比例模型，并使用计算机模拟来预测性能。
Understanding forces – tension, compression, shear and bending – is essential. A truss bridge makes efficient use of materials by carrying loads along straight lines.
理解力——拉力、压力、剪切和弯曲——至关重要。桁架桥通过沿直线传递荷载，从而高效利用材料。
10. Safety Considerations | 安全考虑
During construction, always handle scissors and cut straws carefully. Avoid touching sharp edges of tape dispensers. Work in a tidy space to prevent accidents.
在建造过程中，要始终小心使用剪刀和剪断吸管。避免触碰胶带切割器的锋利边缘。在整洁的环境中工作以防止事故。
When testing, ensure that the mass is placed gently and that the bridge is stable on the supports to avoid sudden collapses that could cause injury.
测试时，确保轻轻放置重物，并且桥梁在支座上稳固，以避免突然倒塌可能造成的伤害。
11. Teamwork and Communication | 团队合作与沟通
If working in a team, divide roles: one person measures and cuts, another assembles, and a third records results. Clear communication ensures everyone understands the plan.
如果以团队形式工作，可以分配角色：一人测量和切割，一人组装，另一人记录结果。清晰的沟通可确保每个人都理解计划。
Use correct engineering vocabulary, such as ‘tension member,’ ‘compression member,’ ‘deck,’ and ‘abutment.’ This helps to think like an engineer.
使用正确的工程词汇，例如“受拉杆件”、“受压杆件”、“桥面”和“桥台”。这有助于像工程师一样思考。
12. Conclusion: Key Takeaways | 总结：关键要点
This case study illustrates the iterative nature of engineering: design, build, test, evaluate, and improve. Every failure is a learning opportunity.
本案例分析说明了工程迭代的本质：设计、制作、测试、评估和改进。每一次失败都是学习的机会。
You have applied scientific principles such as forces and material properties in a practical context. These transferable skills will help you in all technology subjects.
你已经在实际情境中应用了力和材料性质等科学原理。这些可迁移的技能将有助于你在所有技术类学科中学习。
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