Aim
To determine the structural resistance to wind of informal shelters, and how these can be improved, within the available constraints.
The approach
由各种INGO设计的庇护所均使用了两种本地竹子，并与电线和绳子绑在一起，塑料板形成了立面。这些“帐篷”结构不超出任何当前发布的代码或指导，因此必须从第一原则进行评估。它们还使用半熟练和未技能的劳动混合建造，因此工艺差异很大。Arup在以下阶段解决了此问题：
1. Define the problem and understand the constraints
- The team agreed a clear Memorandum of Understanding (MoU), outlining clearly each parties’ roles and responsibilities
- The team conducted a site visit, which involved meeting the various INGOs working in the camps, visiting the camps themselves and joining workshops with stakeholders involved in planning the shelter strategy. All of this was invaluable to understand the context on the ground, and could not have been replaced by remote working
- The team worked within the existing Shelter Sector framework and partners, which ensures that all relevant stakeholders, especially local government, are involved in the process
- The team questioned the stakeholders in order to better understand the wider context. Respectfully challenging the scope can be useful here, because in fast-moving humanitarian situations the bigger picture can rapidly change, and because structural engineering is often not an immediate priority. At the same time, bear in mind that clients will generally understand the context much better, and so be prepared to adapt
Constraints in the humanitarian and developing world are often very different from developed world contexts. Sometimes the obvious technical solution is not possible due to other factors such as local, national or international politics, material availability or skills gaps. It is essential to understand the wider situation, what decisions have been taken to date and why, what has or has not worked, and the long-term ways to engage with the community and “build back better/safer”.
Site visits are invaluable, but need to be done through experienced local partners who understand the context themselves. Ensure the project scope and roles and responsibilities are clearly outlined in an MoU or contract. Project should always be conducted with an appropriately experienced NGO or UN organisation on the ground, within all Cluster frameworks, and with government approval and support.
2. Information gathering
- The team requested as much information from the NGOs as possible, including a variety of photos of as-built elements and connections, in order to understand the variability of the builds
- In-house wind specialists conducted their own assessment of the wind hazard in the region, because the Bangladesh code was considered too conservative for the context of a refugee camp
- 该团队已经在竹子上已经有丰富的内部经验。此外，还对最近发表的测试数据进行了文献综述，以填补空白
- It was important to be aware of the many myths regarding bamboo construction, and therefore to be able to provide reliable guidance to the client
确保您对现场可用材料和技能的可用性和质量以及实际的自然危害（地震，风等）有详细的了解。不太可能提供一组详尽的信息，需要做出某些务实的假设。这些都应在当地背景下和关注的技术领域谨慎并与相关专家进行协商，例如自然灾害。如果没有合适的团队，请准备对项目拒绝，或者无法获得所需的信息。
3. Structural engineering
- A team with experience in low-tech contexts, bamboo and humanitarian work was assembled
- A significant amount of rapid ad hoc advice was provided, based on experience and good engineering judgement, especially when a detailed assessment or report was not required
- Simple hand calculations were considered the most appropriate, as they enabled the team to think through the load path and define element and connection capacities from first principles
- A realistic range of strengths for different failure modes was applied, taking into account local skills, tools and materials
- For the recommendations for improvements, no ‘alien’ technologies, methods or materials were proposed – this is widely considered good practice in the humanitarian and development sector
Materials, methods and quality may be non-standard or unfamiliar. Approach the problem from a first-principles perspective, striving for the same standards of engineering rigour as for any other project. Variations in workmanship and materials are best taken into account by varying the input assumptions and material factors of safety.
In humanitarian contexts it is often not possible to design code-compliant structures. This is not necessary a problem in itself, provided the client is aware of this and understands the risks. The goal of a structural engineer is to ensure the design is buildable, appropriate, works within the existing and future constraints, and if code-compliance cannot be met, then to simply be as strong as possible. Simple hand calculations are generally sufficient. Avoid reinventing the wheel with materials, designs and technologies, as bringing alien systems into developing contexts usually results in implementation failures and sometimes unsafe designs.
4. Testing
- For this project, a reasonable estimate could be made of all construction material properties for construction of the shelters, with the exception of the polypropylene rope, which could not be sourced with a definitive strength. Simple tests were devised to test the rope strength in service conditions
- Some on-site tests that had previously been conducted on other local materials by other parties were not representative, and this had to be explained to the client
Project-specific testing may be useful. Ensure the testing is representative of actual expected workmanship and raw materials, and rigorous enough to be useful. There is no point testing something built by a skilled team of builders with high quality materials, when the final product will be built by unskilled labourers using different materials.
5. Challenge myths and misconceptions in technical engineering issues
- Several misconceptions regarding bamboo were affecting the Shelter Cluster’s approach to the shelters. For example, some organisations considered that painting bamboo with bitumen and casting it in concrete would be durable (in practice this detail rots within a year). The client was informed about this bad practice, backed-up by reasons and evidence
As in any sector, myths and misconceptions of technical engineering issues are common in the humanitarian and developing world. Be prepared to gently and tactfully challenge these, drawing on evidence or physical demonstrations where appropriate.
6.原型
- 在现场测试了改进的设计，并寻求反馈，以了解建造它们的容易性以及如何使其更容易，同时仍然保持良好的工艺标准。
原型设计和基准construction quality is often essential where the design is non-typical and/or the system requires some upskilling of the local workers. Construction of prototypes should be representative of the final build quality. There is no point testing the ease of building something with a skilled team of builders when the final product will be built by unskilled labourers.
7. Reporting
- All assumptions were clearly communicated in a report
- Actual design life, required maintenance and design hazard were all communicated both in the report and verbally, ensuring the client fully understood these and their implications
- 该团队敏锐地意识到，将非正式庇护所与现代代码失败概率进行比较将表明，即使在低风中，所有庇护所都会失败。但是，实际上，考虑安全因素，这只会发生在其中一小部分。因此，向报告提供了减少的安全因素，以确保客户购买并理解含义
Reporting of the inputs, method and result to the client is key. Consider who the audience is: technical or non-technical, and potentially reading in a second language. Emphasis should be placed on areas in the design which may require maintenance, higher quality control, and items that could be vulnerable to poor workmanship.
显然可能沟通是很重要的design life that the structure might expect, what maintenance is required and what hazard it is designed for – this is often poorly done. The risk is passed on to an unwitting end user, who becomes unaware of the residual risks they face and the maintenance they need to undertake.
The proposals put forward and the wording need to be carefully considered, to ensure you get buy-in from all parties at different levels in order to push these proposals through the approval process followed by implementation. Additionally, consider carefully the wider political impact of a design or report, in case certain recommendations or descriptions of hazards may inadvertently drive the client or other stakeholders down less holistically appropriate strategies.
End result
The end outputs were detailed reports which were used by the clients to finalise the improved shelter design and in turn train local workers to implement the construction on a wider scale.
Note on environmental sustainability
在这种情况下，考虑环境可持续性至关重要，特别是考虑到气候紧急情况。因此，在可能的情况下，解决方案应最大程度地减少当地的环境破坏，并最大程度地利用更可持续的施工方法和技术。应考虑材料的整个生命周期和运输排放（因为对于运输到偏远位置的材料可能很重要）。
In this particular case, the only locally available construction material that was also affordable was bamboo, therefore there was no alternative but to use this. Bamboo as a natural material is typically very sustainable. Unlike timber, it can be harvested after 3-5 years (timber takes decades), and harvesting does not kill the plant, rather the plant simply sends up new shoots.
但是，据报道，孟加拉国和缅甸的许多竹种植园的巨大需求损害了收获的数量和质量，很可能导致大雨期间的地表水和侵蚀增加。在此案例研究中，短期内可能没有其他材料能够为这么多难民提供紧急庇护所。在人道主义的紧急情况下，有时必须做出我们可能不想或不允许在传统项目上进行的妥协，而直接的生命安全必须首先出现在其他考虑之前。此后，庇护所部门审查了他们的供应链，以鼓励以最可持续的方法收获种植园。
Key messages
When conducting structural engineering in a humanitarian or development context, ensure the following is considered by the design team:
- Ensure the wider situation is fully understood. A site visit is generally essential, and meeting the various stakeholders can provide a broad perspective
- Work with an appropriately experienced NGO or UN organisation on the ground, within all Cluster frameworks, and with government approval and support
- Involve the right team with humanitarian or development experience, and also experience of the materials being used. Be prepared to say no to the project if the right team is not available
- Ensure an appropriate contract or MoU is in place
- 谦虚和开放。尊重已经在上下文和地区工作的人以及当地建筑文化和传统的知识。请注意您要向的观众及其文化规范。如果需要，请寻求额外的技术支持
- Challenge myths and misconceptions in technical engineering issues
- Challenge the hazard data – the available published data may be out-of-date or incorrect. Consider comparing with other reliable sources
- Avoid importing ‘alien’ materials, technologies or skills – more often than not, these are not adopted, and can even result in a product worse than the community would have achieved without outside help
- 请注意设计或报告的更广泛影响，并确保措辞简单，清晰且适合观众。确保客户对措辞满意并充分理解建议
- Where work is pro-bono or paid, it must be undertaken with the same rigour
- Good quality high level advice at the appropriate time can have a very positive impact
References
1. Arup（2018）Arup Technical Guidance Note 01: Wind loading for the design of upgraded emergency shelters, mid-term shelters and community structures. Rohingya refugee camps, Cox’s Bazar Region.Version 1.0. Arup, London.
2. Arup (2018)ARUP技术指南注释02：在风载下紧急避难所的结构评估。罗兴亚难民营，考克斯的巴扎尔地区。Version 1.0. Arup, London.