| 6. Demo constructions | |
| List of figures in section 6 | |
| Fig. 6.1.1 | A photograph of the school building with bamboo mat |
| boards | |
| Fig. 6.1.2 | Interior of the school building, shelves of plastered half split |
| bamboos below the window level | |
| Fig. 6.1.3.a | A photograph of the interior of the school building, gable |
| wall from inside | |
| Fig. 6.1.3.b | A photograph of the interior of the school building, landings |
| of the Twin arch supported A frame | |
| Fig. 6.1.4 | A sketch of the 7.3m Span A frame supported by the twin |
| bamboo arches vertically separated by ferro cement bands | |
| with three vertical bamboo ties and Centre 2 cross GI wire | |
| ties | |
| Fig.6.1.5 | A photograph of the school building: Plastering of the half |
| split bamboo that make up the gable walls | |
| Fig. 6.2.1 | A view of the small house with ferro cement band twin |
| bamboo arch supported A frames | |
| Fig. 6.2.2 | A view of the small house with ferro cement band twin |
| bamboo arch supported A frames | |
| Fig. 6.2.3 | An inside view of the A frames supported by Twin arches |
| with ferro cement band ties | |
| Fig. 6.2.4 | A plan of the small house with ferro cement band twin |
| bamboo arch supported A frames and bamboo mat boards as | |
| roof | |
| Fig. 6.3.1 | A plan of the small house with near horizontal roof |
| Fig. 6.3.2 | A view of the small house with near horizontal roof of light |
| weight cellular concrete from the top of a building on the | |
| south | |
| Fig. 6.3.3 | A view of the small house with near horizontal roof from |
| the north-east | |
| Fig. 6.3.4 | A view of the small house with near horizontal roof during |
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| construction | |||
| Fig. 6.3.5 | Floor plan | of the small house with near horizontal roof | |
| Fig. 6.4.1.a | An interior | view | of the small house with thatched roof |
| over bamboo bows | |||
| Fig. 6.4.2 | A view of the small house with thatched roof from the north | ||
| Fig. 6.4.3 | A view from the east of the small house ready to on the | ||
| thatch for the roof | |||
| Fig. 6.4.4 | A plan of the small house with thatched roof | ||
| Fig. 6.5.1 | A view of the 30m long sheds from east | ||
| Fig. 6.5.2 | A view of the two long sheds from the south | ||
| Fig. 6.5.3.a | An interior view | of the long shed with vertically separated | |
| twin bamboo arches with bamboo ties and ferro cement | |||
| band ties | |||
| Fig. 6.5.3.b | An interior view of the long shed: landings of the bows | ||
| with ferro cement band ties | |||
| Fig. 6.5.3.c | An interior view of the long shed : 3 ties for each bow | ||
| between the horizontal tie and lower arch – enables one to | |||
| use the space between the horizontal ties and roof bottom as | |||
| a huge storage area | |||
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6.1 7.3 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a primary school building in HET campus.
Size of the building: **10.6 m long and 7.3m wide** Figs. 6.1.1 to 6.1.3 show the photographs of the building.
Fig. 6.1.1 A photograph of the school building with bamboo mat boards
Fig. 6.1.2 Interior of the school building, shelves of plastered half split bamboos below the window level
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Fig. 6.1.3.a A photograph of the interior of the school building, gable wall from inside.
Fig. 6.1.3.b A photograph of the interior of the school building, landings of the Twin arch supported A frame
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Columns:
There are three columns separated by 3.6 m in the central part of each long wall Each of the columns is of 2m high spun cement pipe of outer dia 30cm and inner dia 26 cm. Only 1m of the pipe stands above the floor level while the rest goes down into the foundation and elevation of close to 45 cm.. It is filled with sand cement mortar all the way to the top but for the last 30cm. A 10cm x 10cm cross section RCC garden post is put into the spun pipe from the top to a depth of 30 cm and the inside of the pipe is completely grouted with cement concrete.
Arch foundations:
In the space between the columns is built an arch with RR masonry except for the last 15cm which is of brick masonry. This is referred to as arch foundation.
Walls:
The long walls: These are built with fly ash bricks to a thickness of 22.5cm up to the lentil level and 10cm thickness for about 75cm above the lentil level.
The short walls: These are 10 cm thick single brick walls that meander providing cup boards two on either side of the black board in the North side wall and three on the South side wall up to the lentil level or the black board level.
Above that it is a a single brick 10cm thick wall. All the walls are plastered on both sides.
Lentil tie beam cum sun shade:
On three sides around the building, a single thin beam of thickness 5cm and width of 110cm is casted out of which we get sun shades to a width of 45cm on the out side of the walls and 55cm wide slabs on to the inside of the walls to act as luggage storage bin. The fourth side(North facing short wall) has a big black board and hence the lentil beam does not have either the projection into the room or sun shade out side. The steel reinforcement is 6 nos of 6mm dia steel rods along the length and 8 mm dia steel rods in the transverse direction every 20 cm.
There is another thin RCC tie at the top of the wall linking the steel rods that come out of the top of the RCC garden posts through two 6mm dia steel rods.
The twin vertically separated twin bow arches supporting the ‘A’ frames:
The ‘A’ frames are supported by the twin vertically separated bamboo arches with ferro cement band ties with a span of 7.3m(24 ft) which are described earlier in section 5.5. These are further strengthened by three vertical ties of half split bamboos that go up all the way from bottom horizontal tie to the A frame sides at the top. Two cross GI wire ties from center of the horizontal tie to ferro cement band ties at the quarter span points further reinforce the frame.
A sketch of the ‘A’ frame supported by the bamboo arches is shown in Fig. 6.1.4.
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Ferroceemnt band ties
Bamboo
Brick walls
GI wire ties
Fig. 6.1.4 A sketch of the 7.3m Span A frame supported by the twin bamboo arches vertically separated by ferro cement bands with three vertical bamboo ties and Centre 2 cross GI wire ties.
Note: The two bamboos in the middle of the 2 GI wire ties are used to twist the GI wires, originally in the form a loose loop, locally called “Bisi”. Upon twisting, the GI wire loop reduces in length and becomes tight.
The advantage is that holes and bolts & nuts are not necessary. Traditionally the coconut fibre ropes are used for the purpose. With time, if the tie becomes loose, then the bamboo is twisted a little further to make the tie tight.
In all, 10 such A frames are used out of which 8 are evenly spaced in the centre with about 1.15m spacing while the last one on either side rest directly over the short walls.
The large ferro cement band ties at the ends of the A frames rest on the brick work that is raised from the lentil beam slab that projects into the room doubling as luggage storage utility.
Originally this brick work became necessary as the distance between the top of the long walls is so much that the end ferro cement bands of the ‘A’ frame got a bearing of just a few cm on the wall. This is probably due to a mistake in the measurement of the wall separation. But for this mistake, the end bands of the ‘A’ frame should have rested over the top of the long walls directly with about 10 cm bearing on each wall with out the additional brick work over the lentil slab beam.
Purlins and cross ties:
Both the arches and the sloping sides are tied with several round bamboos as purlins parallel to the long walls but obviously at different vertical planes.
Two giant X ties are made with bamboos and these have eight edges in all: four of these edges start from the four corners of the room; two each of the other four edges start from the two mid points of the long walls. The bamboos of these X crosses curve around the different arches of the A frames and are tied to the same at several places with binding wire ties. Further, three bamboos on each side start from the top of the short walls and lean against the fourth arch from the short wall
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and are tied to these securely with several binding wire ties. These help in keeping the A frames in vertical position even when the gable walls are subjected to wind loads.
Gable walls:
Over the short walls, the ‘A’ frames have a big triangular opening. It was decided to close these openings with what are called gable walls.
Round bamboos are tied at three different levels horizontally over the short wall. These are tied to different vertical and cross ties of the over lying ‘A’ frames. Half split bamboos of suitable lengths are then vertically placed above the short walls next to each other with their troughs facing out side closing the triangular space. Chicken mesh is then stretched on the out side of the half split bamboos and tied to the bamboos. This is then plastered with sand cement mortar.
Fig.6.1.5 A photograph of the school building: Plastering of the half split bamboo that make up the gable walls
6.2 3.5 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a small house.
This is located in the second campus of Haritha Ecological Institute.
This has six columns each of 3.35 m long RCC garden post out of which 2.45 m is above the floor level which itself has an elevation of about 0.4m above the natural ground. These are in two rows of three each separated by 3.5m and their tops are joined by 6 round wood beams of dia about 15 cm.
7 of the twin arch bow beams supported ‘A’ frames rest over the wooden beams directly. The walls are of single brick and 10 cm thick.
The roof is of bamboo mat boards which by themselves give an eve of 60 cm on all sides.
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Figs. 6.2.1 to 6.1.3 show some photographs of the house while Fig. 6.2.4 shows a sketch of the plan of the house.
Fig. 6.2.1 A view of the small house with ferro cement band twin bamboo arch supported A frames.
Fig. 6.2.2 A view of the small house with ferro cement band twin bamboo arch supported A frames.
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Fig. 6.2.3 An inside view of the A frames supported by Twin arches with ferro cement band ties
Shelves, 2m high
Verandah,
Room, with 6 windows and two doors
North
Doors(2)
Shelves up to kitchen top
Fig. 6.2.4 A plan of the small house with ferro cement band twin bamboo arch supported A frames and bamboo mat boards as roof.
6.3 3m & 3.4 m Span ‘Flat Roof’ small house over bamboo bow supported beams: bamboo roof panels with ferro cement over lay, in HET campus.
This small house has two portions, one with aspan of 3m and the other with a span of 3.4 m.
The smaller portion is a single room while the larger portion has a verandah and bath cum toilet in it.
Fig. 6.3.1 shows the plan of the house while figs 6.3.2 to 6.3.4 show the photographs of the house.
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| Shelves, 2m high | Dressing | Roof over hang | ||||||||||||||||||||
| Bamboo arches | ||||||||||||||||||||||
| with 3m span | Bath &Toilet | |||||||||||||||||||||
| Room, with 6 | ||||||||||||||||||||||
| windows and | North | |||||||||||||||||||||
| two doors | ||||||||||||||||||||||
| 3.3m span | ||||||||||||||||||||||
| Bamboo arches, | ||||||||||||||||||||||
| Doors(2) | FerCem band ties | |||||||||||||||||||||
| Shelves up to kitchen | Verandah, | |||||||||||||||||||||
| top | ||||||||||||||||||||||
| Fig. 6.3.1 | A plan | of the small house with near horizontal roof. | ||||||||||||||||||||
Fig. 6.3.2 A view of the small house with near horizontal roof of light weight cellular concrete from the top of a building on the south.
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| Fig. 6.3.3 | A view of the small house with near horizontal roof from the |
| north-east. |
Fig. 6.3.4 A view of the small house with near horizontal roof during construction.
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| Shelves, 2m high | Dressing | ||
| room | Bath &Toilet | ||
Room, with 6 windows and two doors
Verandah,
North
Doors(2)
Shelves up to kitchen top
Fig. 6.3.5 Floor plan of the small house with near horizontal roof
6.4 4.2 m span simple bamboo bow supported ‘A’ frames with a thatched roof house of 30 sq.m area, in Paloncha. (Not covered under the project)
Figs 6.4.1 to 6.4.3 show the photographs of the house while Fig. 6.4.4 shows the plan of the house.
Fig. 6.4.1.a An interior view of the small house with thatched roof
over bamboo bows
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