MIXIA VILLAGE BRIDGE KIT LIST The design minimises the number of different element lengths required. The primary bridge structure can be constructed using only the following materials and tools:
The geometric locking arrangement of the poles has been designed such that no mechanical connections are required: the self-weight of the elements will lock the nodes together in direct bearing between the cross-poles. Members are all subject to bending moments and are simply supported at both ends, so that there is no transfer of moment between elements. The volcanic rock on both banks of the river provides ideal foundations for the arch. At these positions the frames will be recessed into thrust pockets that are formed in the rock.
The number and length of the bamboo elements governs the span of the structure. For this reason the design is appropriate for river crossings in any similar location, where a supply of suitable building materials is available.
8m long typical primary poles
The lightweight nature of bamboo means that individual elements can be manually handled down into the valley, without the need for lifting equipment or heavy plant. Its lightweight properties as well as its flexibility also make bamboo ideal for use seismic areas like the Mixia Valley.
The bridge design achieves a clear span over the river with springing points above the high water level. This means that there will be no need for large scale maintenance during or after the rainy season. The straight forward nature of the connections means that maintenance can be undertaken on visual inspection.
6m long primary end poles
The Yunnan Province is known as the Bamboo Kingdom, due to the amount and variety of bamboo species available in the region. As such a bamboo structure is well suited to this location.
The strength of the design is its simplicity. The frames can be easily fabricated using locally sourced materials (bamboo and rope). The design maximises the use of simple bearing connections, so that there is no need for a skilled labour force during construction.
4.5m long typical braces
An arch structure is proposed to create a clear span across the river using a concept which has been in existence for hundreds of years. Regular lengths of locally sourced bamboo pole will be arranged in four arch forms, and locked together with transverse cross poles. Lateral stability will be provided by diagonal bracing.
3.75m long cross poles
x2 3.25m long end braces
MIXIA VILLAGE BRIDGE PLAN
Construction would take place in the dry season when the river flow is at its minimum. Propping of the bridge is required in the temporary case which may be achieved with the use of a bamboo scaffold tower. Elements can be manually lifted into the positions shown on the sketches and would lock together. In-filling of the thrust pockets should not be completed until the bridge is fully erected so that rotation of the ends is not restricted.
FOUNDATION DETAIL Primary bridge structure
End sections of bamboo members to be grouted to provide additional strength where loads are transferred into the bedrock
Bridge structure to be fixed in position using quarried material to infill around primary members
Excavation in local bed rock on river bank to accommodate bridge structure
TYPICAL CONNECTION Members are to be lashed together for robustness purposes (omitted for clarity) Typical members forming primary bridge structure
Rope tightly bound around members to create guides, preventing slippage of interlocking members
Transverse member acts as a pin, locking primary connections and preventing rotation
Published on Jul 14, 2010