Aim
To determine the structural resistance to wind of informal shelters, and how these can be improved, within the available constraints.
The approach
The shelters designed by the various INGOs all used two local species of bamboo, tied together with wire and string, with plastic sheeting forming the façade. These “tent-like” structures fall outside any current published code or guidance, and so had to be assessed from first principles. They are also built using a mixture of semi- and un-skilled labour, so the workmanship varied greatly. Arup approached this problem in the following stages:
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 All of this was invaluable to understand the context on the ground, and could not have been replaced by remote working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
- The team already had extensive in-house experience in bamboo already. In addition, a literature review of recently published test data was conducted in order to fill in the gaps
- 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
Ensure that you have a detailed understanding of the availability and quality of the materials and skills available on site, as well as the actual natural hazards (earthquakes, winds, etc). An exhaustive set of information is unlikely to be available and certain pragmatic assumptions will need to be made. These should be taken with care and in consultation with relevant experts both in the local context and the technical field of concern eg natural hazards. Be prepared to say no to a project if the right team isn’t available, or the information required cannot be obtained.
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. Prototypes
- The improved designs were tested on site and feedback sought on how easy it was to build them, and how this could be made easier whilst still maintaining good standards of workmanship.
Prototyping the design and benchmarking 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
- The team were acutely aware that comparing the performance of informal shelters to modern code probabilities of failure would demonstrate that all shelters would fail under even low winds. However, in practice considering factors of safety this would only occur for a small proportion of them. Therefore, reporting was presented with reduced factors of safety, ensuring the client bought into this and understood the implications
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.
It is important to communicate clearly the likely 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
Consideration of environmental sustainability is essential in these contexts, particularly given the climate emergency. Therefore where possible, solutions should minimise local environmental damage, and maximise the use of more sustainable construction methods and techniques. Consideration should be given to both the whole lifecycle of the materials and transport emissions (since emissions may be significant for materials transported to remote locations).
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.
However, it was reported that the massive demand for bamboo damaged many bamboo plantations in Bangladesh and Myanmar, which reduced the quantity and quality of the harvest, and could well lead to some increased surface water and erosion during heavy rains. In this case study there was probably no alternative material in the short term able to provide emergency shelter to so many refugees. In humanitarian emergencies, sometimes one must make compromises that we may not want to or are not allowed to make on conventional projects, and immediate life safety must come first before other considerations. The Shelter Sector has since reviewed their supply chain to try to encourage plantations to be harvested in the most sustainable methods possible.
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
- Be modest and open. Respect the knowledge of those already working in the context and region, and the local building culture and traditions. Be aware of the audience you are presenting to and their cultural norms. Seek out additional technical support if required
- 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
- Be aware of the wider impact of a design or report, and ensure the wording is simple, clear and appropriate for the audience. Ensure the client is happy with the wording and fully understands the recommendations
- 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 Technical Guidance Note 02: Structural assessment of emergency shelters under wind loading. Rohingya refugee camps, Cox’s Bazar Region. Version 1.0. Arup, London.