5. Chapter V : The New Techniques of Construction With Bamboo In Colombia

5.1 Introduction.

Many years passed before a great architect from Manizales, one of the coffee regions of Colombia, started to implement new and advanced methods of construction with bamboo and other local timber materials. Simon Velez used bamboo in a way that nobody had before; he expanded bamboo eaves providing maximum capacity and resistance using contemporary materials such as reinforced concrete, steel and fibers. In this chapter I classify and analyze some of his master works, which are considered in Colombia and around the world to be a revolutionary in the use of traditional materials and for introducing new technologies of construction.

In this study one important source of information has been the work of Prof. Oscar Hidalgo, another of several architects who has developed new techniques of bamboo construction. The new techniques he developed are for prefabricated and in-situ use, and some of these I will describe in detail in this chapter.

Another important contribution to this chapter is the recognized work of Prof. Carlos Vergara who died five years ago. His work focused on the employment of rice husk waste, and much of his later research was given to me by his own hand to develop and use in my work, which was enriched by his formulas and important new applications in the techniques of building with bamboo.

The following is a selection form the work of the above-mentioned great architects which represents the most important achievements in the area of alternative bamboo technologies.

5.2. Walls.

The most representative examples of bamboo walls in the modern and improved methods of construction, are mixes of both styles; the Bahareque walls are made out of almost the same materials as the traditional ones, with a variation in the finishing, a mix of low-cost painting components: lime, "marmolina" and water. Even though the following examples of low-cost wall are not made with bamboo, their structural support is.

5.2.1. Rice Husk Walls

Large quantities of rice husk are produced as waste material when the grain is processed, leading to serious pollution problems. In the 60's, Prof. Carlos Vergara from Valle University started to test its utility with different materials, making slabs with sawdust using the ashes of rice husk as a component of Zorel cement. Later, in the 70's, it was used raw as a light filler material in concrete slabs (Los Fundadores residential compound, Cali 28.000 M2), Subsequently a house in a middle income neighborhood and a country house were built with cement panels containing raw rice husk. Then Prof. Vergara tested rice husk with other waste materials which led him to the concept of Rice Husk Walls or Porous Walls (Muros Esponjosos).

The basic recyclable elements are:

• Treated rice husk from rice mills.

• Treated sawdust, a by-product of saw mills.

• Waste coal, resulting from incomplete combustion of coal in ovens and boilers.

• Hydrated lime, cement and water.

If it is possible to get fly ash from the combustion of coal from industrial plants, it could be used by mixing it in ball mills to diminish the quantity of cement up to 50%. (Figs. 5.01.- 5.02).

 

 

Fig. 5.01. Silva house, Amanecer F. Rice Husk panels.

(Source: Deselincourt, E. 1993)

 

Fig. 5.02. Workshop. Amanecer, Quindio

(Source: Deselincourt, E. 1993)

5.2.1.1. Production.

The rice husk and the sawdust are treated in a solution of lime in water (5%) for 24 hours, or else rice husk and sawdust are mixed with lime and water then dried out for use.

5.2.1.2. The mixing.

• 1 cement sack (50 Kg)

• 1/2 hydrated lime sack

• 21/2 waste coal sacks

• 21/2 saw dust sacks

• 4 rice husk sacks

• 40 L of water

The approximate volume resultant from the mixing is 1/4 M3

If it is possible to get fly ash, 1/2 of the cement sack is replaced by 1/2 of fly ash and 21/2 burned and powdered rice husk sacks.

5.2.1.3. Physical characteristics.

• Resistance to compression and flex tension currently being tested.

• weight: 600 and 900 Kg/M3

• Excellent thermic and acoustic insulator

• Seismic resistant due to elastic and plastic characteristics of the material

• Hygroscopic, therefore it is necessary to waterproof the exteriors

 

5.2.1.4. Process of production.

The components of the material are mixed dry; as in any concrete, water is added and the mix stirred again. The mix is poured in a mold, which will have convenient measurements to make blocks or panels. The panels are of 0.90 m*0.45 m-0.10 m.

5.2.1.5. Process of assembly.

First the bamboo structure must be completely finished in order to make the walls. When blocks or panels are used, these are glued on their edges to the bamboo posts and beams with plaster getting the adherence by barbed wire, which is nailed to the bamboo structure. The panels are straightened, to avoid lateral movement.

If the wall is made in situ it is necessary to place the mold on each side of the bamboo posts and make the plaster cast without vibration to avoid its disintegration; it is necessary to compact the material until it adjusts itself without leaving empty spots. Molds could be disassembled after 24 hours.

 

 

5.2.1.6. Comparative analysis.

The physical characteristics of the material and its components offer a comparative advantage to traditional construction systems.

a. The light weight (600 to 900 Kg/M3) gives simplicity and affordability to the structure and foundation.

b. As in any concrete, its load capacity varies according to the mixing dosage, but by the proved tests, a mix with 200 Kg. of cement/M3 gives appropriate characteristics for its use for walls with a slimness = 30

c. It is a good thermic insulator.

d. Its absorption coefficient from 8% to 10% forces the protection of the surfaces exposed to rain with a waterproof coat or at least with a first coat of cement; however, because its surface could be even enough it would not need to be applied with the traditional plaster. A flat finishing could be accomplished, if wanted, with a coat of cement of minimum thickness and then plaster and paint.

e. The ductility of the material makes it resistant to cracking; the same characteristic makes it resistant to seismic movements.

f. Because it is porous, it has good qualities as an acoustic insulator.

g. To add plastic elements, like carboximetil cellulose at 0.5% or povinilic alcohol at 10% in the water, allow the immediate dismolding after pouring the mix into the mold of the prefabricated wall, without collapsing, up to a height of 10 times the thickness of the wall.

h. Qualified labor is needed only in the leveling and plumbing of the bamboo structure and molding; the rest of the activities are carried out with unskilled laborers. This is an ideal system for self-help construction programs.

i. Electrical and hydraulic installations are made before pouring the walls, to avoid their opening and restoration

j. The low-cost of the rice husk walls is based on the bamboo structure and the recycling of waste products. The major costs are in the small amount of cement and in transport.

 

 

 

5.2.2. The Tendinoso Wall.

The Valle University also developed a technique that used bamboo as the main frame for the tendinoso wall, which consists of the rope-like plant fibers of coffee jute sacks, barbed wire and cement. This, a low-cost, ecologically sound building material that is quick to construct and highly resistant to compression, is one of the most effective and secure systems now implemented in the Quindio area, the coffee growing region of Colombia, especially after the recent devastating earthquake which destroyed 60% of the region. It is important to mention that the bamboo buildings and homes remained intact after the earthquake, especially the Tendinoso wall houses at Amanecer near La Tebaida, a little town in Quindio, which was 80% destroyed. Amanecer is entirely built with bamboo, Tendinoso and Rice Husk walls.

To make a Tendinoso wall it is necessary to open up the jute coffee sacks and extend them on a tight barbed wire which is tied up to the knots of the bamboo posts. These posts must be separated by a maximum distance of 3 M. Once the sacks are extended on the barbed wire, they are tied together with thin wire. The sacks must be tied to the cement floor as well as to the top bamboo beams of the structure. When there are no bamboo posts between the wall, but only wooden window or door frames, the barbed wire is extended along them, following the same steps as with bamboo. The next step is to make a cement-sand mixture and load the wall for the first coat; when this is ready - dry enough- the next two or tree coats of thicker and drier plaster are added, the thickness of the wall depending on the design of the space and its internal characteristics. Usually the thickness depends on the width of the frame in order to make a wall continuous and better finished. After the wall is plastered on both sides, it is next painted either with lime or with common acrylic or water base paint. (Figs. 5.03 - 5.04 - 5.05).

 

 

 

 

Fig. 5.03. Tendinoso wall with its first cement coat.

(Source: Amanecer, Bustillo, R. 1993)

 

 

 

Fig. 5.04. Ismail House, Amanecer. Quindio

finished tendinoso wall house

(Source: Amanecer, Bustillo, R. 1993)

 

 

Fig. 5.05. The 'Big Hall'. Amanecer, Quindio.

Tendinoso wall building.

(Source: Amanecer, Bustillo H. 1993)

 

 

5.3. Structure.

In this decade the use of bamboo has changed. Specially with the introduction of bamboo in the construction of haciendas, country houses, and urban houses; new materials, new alternatives and ideas for bamboo structures are being developed by architects

The following is a classification of the most important techniques and forms of bamboo structures, combining it with steel and concrete reinforcements to get greater spans and more innovative ways of creating large spaces, and enriching and beautifying them with color and texture.

 

 

5.3.1. Prefabricated Three-dimensional Bamboo Structures.

A prefabricated framework of bamboo was designed and tested by Oscar Hidalgo in the Science Department of Palmira University. This was a model for rural school rooms measuring: 5.00 M * 8.00 M, with a corridor for circulation and entrance of 2.00 M, with a total of a 64 M of covered area. To cover the interior space it was necessary to build 4 triangular roof trusses, which are 8.00 M long * 2.00 M wide * 1.27 M high.

Trusses were placed on a load-bearing bamboo structure and built with 3 parallel wooden beams of 6.00 cm * 20.00 cm, separated every 2.00 M and 5.00 M respectively. The roof could be built with channels from one side to the other but also, between each three-dimensional truss, with an extra gable roof so that its two channels can take the water to the edge of the overhangs.

5.3.2.1. Norms of Construction.

• The three-dimensional bamboo structures are composed of three main pieces 8.00M long, placed parallel, forming in section an isosceles triangle of 2.14 M at its base and 1.27M high, with two equal sides 1.66M long. These pieces are joined at their sides by other secondary ones which are composed of rafters and diagonal bamboo supports forming a triangular frame, and also by bamboo beams that join the two pieces perpendicularly.

• In these structures only 3-year-old (or more) straight bamboos must be used, which have been previously cured in the bamboo plantation, dried in the shade, and treated against insects. Their average diameter must be 10 cm. or greater and their average thickness one cm. Bamboo with fissures, cracking or insects must not be used, nor should the ones that have flowered, because these have low resistance to traction and compression.

• The main pieces must be cut 9.00M or longer, to facilitate the transport of the finished truss. The remaining pieces will be cut once the structure is placed on the bamboo posts and beams.

• It is not possible to establish an exact length for the rafters and diagonal supports due to the variation in size of the main pieces; however, if these pieces are going to be cut inside the bamboo plantation and then taken to the place where they will be used, they must be cut 1.80M long to be later re-cut to the exact measurement.

• The three-dimensional bamboo structures must not be built on the earth but on four horizontal parallel bamboo bases, raised from the earth at least 30 cm, facilitating the nailing and tying of the joints of the secondary pieces to the two main pieces. These bases can also be made of timber, leveled on its top side at the same height (30 cm). The bases must be 5.00M or longer in order to allow at least the construction of two structures at the same time.

 

 

5.3.2.2. Wooden triangular frames.

To make the bamboo structures the same in width and height, four frames or wooden triangles, are built with three pieces 10 cm wide and 5cm thick. These are assembled by little wooden pieces that help to form an isosceles triangle. Two equal sides which measure in the interior 1.66M long, a longer side or base of 2.14M, and a height of 1.27M. These triangles must be made tight with wire in the joints for further dismantling once the structure is finished. To avoid movement of the structure, they are secured with braces that are placed at each side as is shown in the Figure 5.06.

.

Fig. 5.06 (Source: Hidalgo, 1978:71)

 

 

The rafters are placed every 1M; they must be nailed loose to move them as necessary when the diagonal pieces are placed. (Fig. 5.07).

Fig. 5.07. (Source: Hidalgo, 1978:73).

According to the kind of roof to be used, the structure is covered with Esterilla - unrolled bamboo- or the bamboo supports are placed with the dimensions and separations required. (Fig. 5.08).

Fig. 5.08

Fig. 5.08. (Source: Hidalgo, 1978:73).

5.3.2.3. Assembly of the structure.

Due to its lightness and rigidity, assembly is fast and easy. Trusses could be lifted manually or with a crane, which was used for the assembly of a four-bay experimental structure, which was assembled in just 40 minutes. (Figs. 5.09 to 5.12).

Fig. 5.09. (Source: Hidalgo, 1978:77).

Fig. 5.10.

Fig. 5.11.

 

Fig. 5.12

5.3.2.4. Application of plaster as a roof.

The roof could be made on a bamboo structure using a coat of plaster of cement and sand in a proportion of 1:2, or of soil-cement.

Fig. 5.14.

The esterilla must be covered with a very liquid cement coat and then let to dry. Fig.5.14.

 

Fig. 5.14. Fig. 5.15

 

 

 

In this case it is necessary to make tests with different proportions to obtain the most appropriate mix. To this mixing could be added straw cut 1 cm long.

The quantity of water is determined by the soil-cement when it is handled easily without leaking or deforming. (Fig. 5.14).

Before the application of the soil-cement coat the roof must be humidified. (Fig. 5.15).

Application of the soil-cement to the roof. (Fig. 5.16).

Leveling of the roof. (Fig. 5.17).

Smoothing of the roof. (Fig. 5.18).

 

Fig. 5.16. Fig. 5.17. Fig. 5.18.

Varnishing of the roof. (Fig. 5.19).

Cutting of edges is done with a wooden board. (Fig. 5.20).

 

Fig. 5.19. Fig. 5.20.

The application of the coat must be made vertically. (Fig. 5.21).

The gutter of the roof. (Fig. 5.22).

Exterior view of the finished room. (Fig. 5.23).

 

Fig. 04.21. Fig. 04.22.

(Source: Hidalgo, 1978:85).

 

 

Fig. 5.23. (Source: Hidalgo, 1978:84-86)

 

5.3.2. The Concrete-Reinforced Bamboo, a New Technology

The Concrete reinforced bamboo is a technology that uses the traditional bamboo construction methods combined with modern construction materials like concrete and steel bars, to improve the tensile, compression and flexion properties of bamboo.

As in all cases, bamboo needs to be cured and protected previously in order to be reinforced with concrete. In each joint of the bamboo structure, a screwed 0.50 M steel bar of Ø 1/2" is inserted along or across the bamboo, then the joint is filled with concrete of 3.000 PSI. See Fig. 5.24.

The steel bars must cross the multiple bamboo posts, beams or trusses in order to work as

one load-bearing element. Fig. 5.25. In some cases, the bamboo knots must be removed to allow the steel bars and concrete to penetrate inside it.

 

 

Fig. 5.24. Concrete-Reinforced Bamboo. Fig 5.25. Multiple bamboo truss crossed by the steel bars.

(Source: Gonzalez, 1999) (Source: Villegas, 1989:45)

 

Fig. 5.26. The Coffee Park, Quimbaya, Quindio. Funicular station. Simon Velez.

(Source: Orozco, R. 1998)

This process of reinforcement allows greater spans and interior free column spaces. Overhangs can be easily built with the help of the concrete-reinforced bamboo system, challenging gravity, these daring structures can support heavy roofs and floor loads. (Fig. 5.26).

In the overhangs, joints must be carefully carved , in order to allow the best adherence and accommodation in beams, trusses and posts. (Figs. 5.27).

Fig. 5.27. The Coffee Park, Quimbaya, Quindio, lookout overhang. Simon Velez. (Source: Orozco, R. 1998)

 

 

Figs. 5.28. (Source: Villegas, 1989: 155)

These carved joints are called in Colombia boca de pescado (Fish Mouth) joints, because its shape resembles the open mouth of a fish. Figs. 5.28

 

5.3.2. Super-Structures with Concrete-Reinforced Bamboo. Simon Velez Arch.-

Twenty five years of experience in construction with timber, which was becoming every day scarcer, more expensive, and always badly cut and proportioned, led Simon Velez to give his attention to mangle - very strong and resistant wood from the Pacific coasts of Colombia and to guadua, whose commercial length varies between 9 and 10 M.

As mentioned before, guadua is the wood for the poor of the Old Caldas region. Mangle is the wood of the poor on Pacific coast. A few tests led Simon Velez to learn to use it and to appreciate it. But with guadua he had the most difficult problems especially because of its wholeness. The difficulties arose when he had to resolve problems of structure assembly in joints to work in traction.

At the beginning he used guadua in structures under compression loads; i.e. arches. In this case he developed a technique that allowed him to build structures with up to 20 M spans for roofs with cement plaster and clay tiles, a very heavy type of roof.

For large overhang structures he filled the knots of the joints with cement in order to resist the strong tension forces present. These joints were the ones he used for placing the bolts and steel reinforcements. The bamboo fibers are amazingly resistant to tension; they are called " vegetable steel". In these structures is necessary to calculate the resistance of the bolts, not of the bamboo. (Fig. 5.29).

" With a construction system for structures of Bamboo-Guadua, where the joints for the tension and compression forces are resolved, it is possible to compete in equal conditions with materials such as timber, steel and concrete" - Simon Velez- .

 

 

Fig. 5.29. The Coffee Park, Quimbaya, Quindio, lookout. Simon Velez. (Source: Orozco, R. 1998)

 

5.3.2.1. Km. 41 House, Manizales, Caldas - Colombia.

This house is composed of five main pavilions, each one of them with different structural characteristics. Only the 3 most important pavilions which contain the principal concept of Simon Velez's first approach to concrete reinforced bamboo super-structures are described.

5.3.2.1.1. The Main Pavilion.

In the main pavilion, shown in the pictures, the overhangs are symmetrical spanning 6 M overhangs. Concrete reinforced bamboo supports the heavy cement and clay roof in a way previously never exploited. This simple but very ingenious design allowed Simon Velez to start increasing spans in his constructions. The joint assembly is called: "Flute Supports", which consists of a concrete corbel and capital with bamboo flute supports embedded in concrete at the moment of the concrete pouring. The bamboo is beautifully placed like a flute, without the help of any column or vertical support.

The ceiling is made with plastered chicken wire, and painted, letting bamboo show its beauty. Wooden planks were used as an additional support for the one-coat cement and clay roof. (Fig. 5.30a. to 5.32).

 

 

 

Fig. 5.30b. Fig.5.30c.

Fig. 5.29b Detail of concrete column and capital, with bamboo "fluted" support.

Km. 41, Manizales (Source: Villegas, 1989:40)

Fig. 5.30. Central detail of the truss (Source: Villegas, 1989:45)

Fig. 5.31. Main Pavilion, lateral view. Km 41, Manizales (Source: Villegas, 1989:42)

 

 

Fig. 5.32. Main Pavilion. Rear view, Km. 41, Manizales (Source: Villegas, 1989:43)

5.3.2.1.2. The Children's Pavilion.

This building uses mangle poles as columns and bamboo for the roof structure. Wooden planks are used as an additional support for the roof.

Three pairs of mangle columns are raised from the floor, but only two of them get to the top of the roof joining the three bamboo "flute" gable rafters. The third one has the function of supporting the 2 diagonal guadua braces, which are also tied to the three bamboo "flute" gable rafters. Also these braces are joined to the purlins by the so-called Boca de Pescado ("fish mouth") joint to the bamboo collar beams. A 0.50M king post ties the bamboo rafters and the collar beams. The rafter is composed of groups of three reinforced-concrete bamboos; these have the function of supporting almost the whole load of the clay and cement roof. The 6M long overhangs are, as in the main pavilion, working as one structure with the same elements: the concrete corbel and capital, and three horizontal arms which end at the overhangs in flute-like shapes. (Fig. 5.33a-b.).

 

 

 

Fig. 5.33b. Interior of the Children's Pavilion. Km. 41, Manizales

(Source: Villegas, 1989:44)

5.3.2.1.3. The Stall No1.

As in the Children's Pavilion, the stall has treated mangle posts and a concrete-reinforced bamboo roof structure. The rafters are composed of three fluted bamboos tied with bolts at each union. Also the bamboo collar beams embrace these rafters and the purlins in a "Fish Mouth" joint assembly. The two interior bamboo braces tied to the mangle posts give continuity to the 4M overhangs at each side. As shown in the picture, two mangle posts raised from the ground and the other two meet their companions at the braces joint to form a perfect and balanced structure. The 8M span gives an open and column-free interior space, which is required for the circulation of the animals around the stall. The roof is covered with traditional Spanish clay tile supported by 20 cm timber planks, separated every 35-40 cm. (Fig. 5.34a-b).

 

 

 

Fig. 5.34b. Stall No 1. Km 41, Manizales (Source: Villegas, 1989:170)

 

5.3.2.1.2. The Stall No 2.

This example of the combination of concrete and bamboo gives an idea of how wide a variety of spaces could be conceived when using this type of technique.

In this case the three bamboo fluted rafters are supported by six concrete-reinforced bamboo beams, also flute-like. These beams are at the same time supported by two 0.80 M diameter reinforced concrete columns. Single queen posts help to embrace the bamboo fluted rafters and beams along the whole roof structure. Single king posts help to embrace the braced ridges to the beams. All this joinery is assembled with 0.30 M to 0.50 M long bolts, which combined with steel tensile, give the resistance to this 6.00 M long overhang gabled roof. (Fig. 5.35a-b.).

 

 

Fig. 5.35b. Stall No 2. Km 41, Manizales. (Source: Villegas, 1989:86-87).

 

5.3.2.1.3. The Social Area.

This arched structure is the central and main space of the house. Its 10 M interior span and 3.50 M long overhangs make every structural element work in compression. Concrete-reinforced bamboo in its joints tie the whole structure which has a footing foundation of 1.00 M - 0.50 M. Every footing supports two main bamboo posts and two braces which are tied by the "fish mouth" joint to the double bamboo collar beams. A third brace helps support the double bamboo ridge beams; a star shape is formed and embraced by a single double bamboo king post and four double diagonal bamboo king posts. Fig. 5.36.a- 5.37. Four secondary double beams are placed at the points of the star-like to form the arched structure. As in the above-mentioned examples, the overhangs are held by double bamboo braces and three bamboo fluted rafters. Wooden bamboo planks support the heavy clay tile roof, together with the bamboo purlins. These elements support the esterilla ceiling which is covered with cement, a water-proof material, and white painted chicken wire plastered for interior finishing. (Fig. 5.38).

 

 

 

Fig. 5.36b. Fig. 5.37

(Source: Villegas, 1989:170)

 

Fig. 5.38. (Source: Villegas, 1989:170)

5.3.2.2.The ZERI Pavilion, Manizales

The ZERI Pavilion is a circular building, which was built with bamboo, and also another excellent resistant-to-tension-and-compression Colombian wood called Alizo. This 40 M diameter building was designed and built as a test model for the ZERI (Zero Emissions Research Initiative) Congress in Hanover, Germany. (Figs. 5.38. - 5.40.).

 

Fig 5.38. Longitudinal section of the Pavilion. (Source: http://www.zericongress.org.co/pabellon/pabellon5.htm)

 

 

"It is a prototype of a pavilion to be built at EXPO 2000 in Hanover. The technique is so revolutionary that German building regulations could not permit it to be built in Hanover until the Government was convinced a replica built elsewhere would stand up. Now they are sending a team out to Colombia to see Simon Velez's MASTERPIECE."

This mushroom-like construction was developed for ZERI by Simon Velez and can be considered as one of the most inspiring examples of "sustainability" and the re-usability (and not only of this) of buildings and their construction.

 

 

 

Fig. 5.39.

Fig. 5.40.

Figs.5.39. and 5.40. Pavilion sections. (Source: http://www.zericongress.org.co/pabellon/pabellon5.htm)

5.3.2.2.1. Foundations.

To avoid any contact with the humid soil, raised concrete bases were made and which will also hold the alizo posts. (Fig. 5.41.). The bark from this long and highly resistant wood has to be removed before its use. Sockets are placed in their bases, to avoid contact of the wood with concrete, helping to keep the structure free from humidity.

Fig. 5.41. Alizo posts base socket. (Source: http://www.zeri.org/pavillion/)

 

 

 

 

5.3.2.2.2. The Alizo Posts.

This wood has been used by Simon Velez for a number of years in his structures. Used in combination with bamboo, its resistance allows for great spans and overhangs. The alizo's rounded end allows easier accommodation for the sockets and better adherence to the steal bars.

A hole is made in the base of the post to insert the Ø 3/4" steel bars of 0.8 M long, placed and then inserted into the alizo posts as shown in Figs. 5.42. to 5.44.. Their diagonal position plays an important role in the holding and perfect balance of the immense load of the clay tile roof.

 

Fig. 5.42. Concrete foundation. (Source: http://www.zeri.org/pavillion/).

 

 

 

 

Figs. 5.43 - 5.44. Connection between posts and foundation (Source: http://www.zeri.org/pavillion/).

 

Fig. 5.43. Fig. 5.44.

 

5.3.2.2.3. Bamboo beams and concrete reinforced joints.

The 9 M bamboo beams are assembled on the ground, and water cement is introduced into the joints. Ø 1/2" Steel bars are used. Steel braces are placed at the surfaces of the triple bamboo beams which surround the whole structure. (Figs. 5.45 and 5.47.).

"The architect, Simon Velez, invented the technology for uniting several pieces to maximize the tension strength. He injects fine cement into the inside of the bamboo and tightens it with copper bolts. It is only thanks to this invention that large structures like the pavilion with overhangs of up to 9 meters can be constructed at such a low price, competing with steel and cement structures, while creating an immense visual effect both inside and outside."

Fig. 5.45. Inserting the steel to the bamboo beam. (Source: http://www.zeri.org/pavillion/).

Fig. 5.46. Assembling the bamboo beam. (Source: http://www.zeri.org/pavillion/).

 

Figs 5.47. Detail of joint of reinforced bamboo and alizo. (Source: http://www.zeri.org/pavillion/).

After the on-ground work is finished, scaffolding is assembled to raise the beams and rafters. (Figs. 5.48 to 5.51.).

Fig. 5.48. (Source: http://www.zeri.org/pavillion/).

 

Fig. 5.49. (Source: http://www.zeri.org/pavillion/).

 

 

Fig. 5.50. Overview 1. (Source: http://www.zeri.org/pavillion/).

Fig. 5.51. Overview 2. (Source: http://www.zeri.org/pavillion/).

 

 

At a height of 13.5 M, This 2 M diameter steel ring receives all the compression from the roof structure. (Fig. 5.52 and 5.53.). (Source: http://www.zeri.org/pavillion/).

Fig. 5.52. Metallic Ring. (Source: http://www.zeri.org/pavillion/).

Fig. 5.53. Detail of metallic ring and steel reinforcement. (Source: http://www.zeri.org/pavillion/).

 

5.3.2.2.4. The Overhang.

The most gravity-daring element of the whole structure is this 9 M long overhang. The joint in its base is a knot of four Alizo posts, two fluted bamboo capitals, and six fluted reinforced concrete bamboo overhang beams. (Figs. 5.54 to 5.61.) The quadruple diagonal Alizo posts from the interior hold the quadruple braces that are assembled to the steel ring. Cement is poured into each bamboo joint and then embraced with steel and copper bolts. Steel tensile are assembled to strengthen the joints. Also diagonal braces unify the whole structure, making it very stable and perfectly balanced. Because of the strong concrete reinforcement in every part of the building, this structure is earthquake resistant, one of the elements that have proved to be extremely effective when these natural disasters occur.

Fig. 5.54. Support joinery of overhang 1. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

 

 

Fig. 5.55. Support joinery of Overhang 2. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

Fig. 5.56. Overhang structure. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

 

 

 

Fig. 5.57. Upper floor corridor. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

 

 

Fig. 5.58. Ceiling of overhang area. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

Fig. 5.59. Applying mortar to the ceiling. (Source: http://www.zeri.org/pavillion/pavillion.htm#)

 

Fig. 5.53. . (Source: http://www.zeri.org/pavillion/pavillion.htm#)

Figs. 5.60. Overview of the finished pavilion. (Source: http://www.zeri.org/pavillion/).

Figs. 5.61. The Zeri Pavilion, Manizales, Colombia. (Source: http://www.zeri.org/pavillion/).

 

5.4. Advantages.

5.4.1. Walls.

5.4.1.1. Rice Husk Walls.

• Its lightness makes walls very easy to handle, creating labor savings , since one man can carry two panels at the same time.

• The lightness also saves money in foundations, because the quantity of steel is not the same as in the traditional brick or concrete wall.

• Because of its porosity, this kind of wall has great thermal and acoustical insulation properties.

• High compression resistance.

• The rice husk panels can be cut easily with a saw, allowing many possibilities for shapes and forms when bamboo braces and beams are embedded into the wall.

5.4.1.2. Tendinoso Walls

• This wall is highly resistant to earthquake and seismic movements.

• Very inexpensive materials are needed for its construction. Some of them are recyclable organic products.

• Like rice husk walls, tendinoso walls permit a variety of forms and shapes when braces and beams are embedded into the wall.

• Highly resistant to compression.

• The thickness of the walls can be easily increased by adding more coats of plaster on each side of the wall, according to the function of the space.

 

5.4.2. Structure.

5.4.2.1. Prefabricated Three-Dimensional Bamboo Structures.

The prefabricated three-dimensional bamboo structures have the following advantages compared with timber structures, used commonly in the construction of gabled roofs.

• The prefabrication system allows the structure of the roof to be made on the floor, before or during the construction of the structural bamboo frame. This way the danger of accidents is reduced and also the assembly time could be minimized, depending on the number of workers available.

• Due to the rigidity and lightness of the bamboo structure, this could be prefabricated in places other than the site, where there could be better space, and availability of materials and workers, and then transported to the construction site.

• The construction of the bamboo structures is so simple that it could be done by the peasant or the community without the need of specialized carpenters.

• Their cost is very low, especially where material is abundant and the distances are relatively short. Also the structures do not need the ceiling commonly used in the gabled roofs.

• Due to their shape, they allow better illumination and ventilation in the interior spaces, important requirements in the construction of rural schools.

• These three-dimensional structures are appropriate for anti-seismic construction, due to the resistance and flexibility of bamboo and also to the rigidity given by their triangular shape.

• Besides their use for schools, housing, and rural buildings, these structures are appropriate for the construction of shelters and emergency hospital installations in times of disasters by earthquakes or floods.

5.4.2.2. Super-Structures with Concrete-Reinforced Bamboo.

• Great spans can be covered without much interference by posts in between. Ideal for wide corridors in rural houses.

• Highly inexpensive bamboo structures,

• Because of its natural and chemical treatment, bamboo can last many decades with constant maintenance and care.

• Structures are capable of bearing loads of up to five floors.

• Dynamic and beautiful structures can be used for multiple functions due to the large and open interior spaces they permit.

• A great variety of spaces can be designed using a repetitive portico.

 

5.5. Disadvantages.

5.5.1. Walls.

5.5.1.1. Rice Husk Walls.

• Careless handling can cause wear.

• If experienced labor is not available, the long process in the production can lead to delays.

• When working on site, experienced labor is needed which is hard to find in an innovative system.

• Panels can be difficult to make if the right molding is not available. This could lead to an increase the cost of the walls.

• Transportation of panels can be costly due to their volume.

5.5.1.2. Tendinoso Walls.

• Due to their physical characteristics, tendinoso walls are not thermally and acoustically insulated; therefore, noise can invade interior spaces and temperatures can not be regulated.

• Unlike rice Husk walls, tendinoso walls need a frame to extend the barbed wire, increasing costs for wood and bamboo.

• Once the wall is made, it cannot be changed or corrected unless it is completely demolished.

• Cement can be wasted if there is no control over the thickness of the wall. Also one side might have a different thickness from the other one.

5.5.2. Structure.

5.5.2.1. Prefabricated Three-Dimensional Bamboo Structures.

• Fabrication of this kind of structure requires large areas of land, making it difficult when building in the city.

• If gutters are not properly sealed, leaking could become a problem and eventually the rotting bamboo could cause serious structural problems.

• Steep increases of costs when cranes are used to lift the structures.

• Extra costs in labor could occur when using manpower for lifting structures.

 

 

 

 

5.5.2.1. Super Structures with Concrete-Reinforced Bamboo.

• Large amounts of bamboo are needed for this kind of structure. When there is no control in the municipality, eventual deforestation and damage in the ecosystem could occur.

• Highly experienced labor is needed, and this leads to increased building costs.

• The time required to make the structure makes for high labor costs.