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Humanitarian Engineering & Computing (HE&C).
Workshop to build bamboo ReciproBoo relief shelters.

22nd May 2014

This was an opportunity for students to get hands on experience building reciprocal frame roof relief shelters based on the ReciproBoo Shelter Kit (RSK). It was also the first time that these 4 pole reciprocal frame roof bamboo shelters had been built in the UK.

The shelters were well received by both staff and students. Reciprocal frame construction not only offers research and educational opportunities, but also a direct practical link to understanding the needs of families affected by a disaster.

The following report highlights the main differences between these shelters and the 5 shelters built at the workshop in Nepal.

S.Halbert
ReciproBoo Shelter

Bamboo shelter workshop report:

Materials:

Bamboo.

Moso bamboo imported from China and supplied
by UK Bamboo Supplies Limited.

Pre-cut to 2metre,3metre and 4 metre lengths.
Support poles and main ridge poles are 40 to 45mm diameter.
Frame poles and side ridge poles are 30 to 35mm diameter.

Ropes.
Locally sourced 3 ply 6mm diameter synthetic hemp.

Lashings.
Locally sourced 3 ply 3mm diameter jute twine.

Tarpaulin.
Standard triple laminated 6m x 4m relief tarpaulin, weight 4.5Kg.

Tools:

Shovel, Pick, Post Auger, Hacksaw, Knife, Mallet, Tape measure

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The emergency bamboo ReciproBoo Shelter Kit (RSK)

Assembly teams:

3 staff and 2 students.

Notes:
No previous experience lashing .
Limited knot tying skills.
Enthusiastic and hard working.

Double Elevated ReciproBoo Shelter (DERSK):

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The first 4 pole reciprocal frame is lashed together on top of two side poles

The assembly was essentially the same as for the original DERSK shelter in Nepal but with two important differences;

1. Side and lower ridge poles were used instead of ropes.

2. The main ridge pole was lashed to the side of the support poles instead of on top of the support poles.

Observations:

1.Reciprocal frame overlap.

Each reciprocal frame pole was marked at two points :
7cm and 90cm from one end (the frame crossover points).
This produced an inner frame measurement of 80cm.
The resultant frame was 3.35 metres square ( at its support points)

This compares to the Nepal frame with a 70 cm inner frame measurement that resulted in a frame 3.60 metres square.

Increasing the inner frame by 10 cms increases the sides of the frame by over 20cms.
This is important when estimating the roof frame size for a given size of tarpaulin.

In the field it is likely that the overlap will be estimated by eye; approximately one third of the length of the pole ( as for the steel shelter). The alternative for aid agencies would be to pre- mark poles to standardise shelter dimensions.

2. Using rigid side poles instead of ropes.

The Galway University research had shown that using rigid poles decreased the stress on the frame by up to 24%.
If available poles are therefore preferred to ropes.

However, it should be noted that this shelter required 60 metres of bamboo instead of the 36 metres used for the same dimension shelter in Nepal (ie 66% more bamboo). While the additional frame strength and support afforded to the tarpaulin should be the standard when resources allow, the additional bamboo weight and transport costs have to be taken into consideration by aid agencies in planning their response.

3. Lashing the main ridge pole to the side of the support poles .

This was the preferred option for this demonstration; it was simple and easier to cross lash the joints on the ground rather than work on step ladders.
We also tied a loop of twine,to further support the ridge pole, over the top of the support post into a pre-cut groove on the top of the support pole.

The alternative option to prevent
slippage of the frame down the
support poles would have been
to cut a " fish mouth" joint
(or "V") at the top of the support
pole to take the ridge pole as
at the Nepal workshop.

This is a joint that needs more work to standardise what is needed for a relief shelter.

4. Positioning of roof frames on the central ridge pole.

As for the double shelter in Nepal the two roof frames were located outside the support poles. This worked well for the first frame but, due to limited space, was more difficult for the second frame. Eventually it was decided to position the side poles on top of the second frame. While this created a good multiple pole joint for lashing purposes, the optimal order for laying these poles still needs to be determined ( ie should they reciprocally overlap or is this not necessary?)

5. Roof incline.

The above support position for the roof frame and higher outer support posts resulted in a lower roof incline than Nepal. Details of this will be included in a full assessment .
It should be noted that whereas the reciprocal frame can support the most weight in a horizontal plane, the wind uplift forces are higher.
The optimum incline for this type of roof needs to be determined.

6. Tarpaulins.

A single tarpaulin was positioned for demonstration purposes.
The reciprocal frames offer good anchor points for tarpaulins if side walls are to be built.

7. Overall build.

Considering this was a first time build for a team learning new skills the shelter was very good.
It provided good tarpaulin support with no noticeable deformation on loading and handling. Indeed the measurements between the support poles taken after the build ( see below) are remarkably uniform considering the slight ground slope.

Covered space = 20.1 square metres
( Sphere guidelines 3.5 square metres per person = close to a six person shelter).

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The main ridge pole is lashed to the support poles on the ground. This support frame is then lifted into its post holes.

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The two roof frames are lifted up and placed onto the main ridge pole.

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The frame is completed by lifting the two roof frames onto their lower support posts

Coventry Dims
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First tarpaulin in position

The emergency bamboo ReciproBoo Shelter Kit (RSK)

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Students working on the reciprocal frame layout

This shelter was deliberately built over a bank to begin demonstrating how the shelter can adapt to any terrain.

The assembly was essentially the same as for the original RSK shelters built in Nepal, but using locally sourced lashings and ropes.

This shelter requires only 7 bamboo poles; it is simply a 4 pole reciprocal frame roof lifted onto a 3 pole support frame.
Side ropes are used instead of bamboo poles.
No holes are required; the structure is simply attached to the ground by 4 bamboo stakes and 2 heavy guy ropes.

This emergency shelter is lightweight and very strong. Its ability to support branches, a mud covered bamboo lattice, reeds and even corrugated iron on its reciprocal frame make it much cooler than any tent (important to reduce dehydration).

On day two following a disaster, if bamboo is available, a family can start to upgrade this shelter to a full DERSK shelter above.

Observations:

1. Reciprocal frame overlap:

The two students were initially not given any instructions and had to figure out how to lay out a reciprocal frame. The concept does require some basic instruction when introduced to people for the first time; and being told to "overlap each pole in turn" is usually sufficient.. Pre-marking the poles with red and green spots (as for the steel RSK) would achieve the same result and also standardise the shelter size for given tarpaulins.

2. Attaching the base of the frame to the ground.

Bamboo stakes were initially driven into the ground next to the end of the frame pole.This made attaching the ends of the frame pole difficult. By moving the stake a few inches further up the pole it created a joint that was much easier to cross lash.

3. Attaching the side ropes.

The side ropes were attached between the ridge pole and anchoring stake on the ground. The synthetic hemp rope used was adequate but not as easy to tie knots with.

4. Attaching the support poles to the ridge pole.

In this build the frame was pre-lashed on top of the ridge pole. Consideration may be given to building a frame out of support poles and ridge pole on the ground and then lifting the frame onto it.

5. Tarpaulin support.

A larger tarpaulin was needed to further overlap the side ropes . A second tarpaulin could easily be attached to the frame to make an end wall.

6.Increasing available height on sloping ground.

On a steeper incline it would be advisable to cut back into the ground (providing water run off is channelled away from the shelter).

7. Distortion of central frame during building.

Due to the repeated handling during stake fixing and the sloping ground the students did not notice a rotational distortion of the central reciprocal roof frame that occured during the build. This could easily have been corrected before fixing the two lateral guy ropes.
Despite this distortion the shelter was functional and in no danger of collapse; yet another demonstration of the flexibility of this structure.

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The frame is lifted into position across the bank and secured to the ridge pole. Note the bamboo stake incorrectly placed at the very end of the frame pole.

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The RSK near to completion. Note the correctly located stake and lateral guy ropes.

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