Projects of IL 31

Straight Rods


Introduction

  
Under the headline "straight rods" the documentation LI 31 treats construction systems with straight rods and the constructive possibilities of the single rod.
In several sketches and photos of modells constructions are shown which fit to the building with straight rods in a special way. Further a way of dimensioning, the BIC diagram, is explained. Besides the traditional manner of construction of South-east Asia the south American manner of construction is described by examples of a bamboo settlement in Manizales that is influenced by the Northamerican platform way of construction. The bamboo tower of the Phänomena in Zürich connects the traditional chinese way of construction with european technics. The transition from straight to bent rods is shown by the example of the development of traditional bamboo umbrellas to tent frames.
It may be anticipated that it's tried to keep the deforment under weight small by using short lengths of the lower stiff section of the bamboo. In addition, short spans and little weights are taken. Only in special cases the full length is used, which means, that you have to pay special attention to the development of details.

Structural Systems

  
konstruktions skizze
Several Systems of Construction

Structural systems with conical rods.

Straight rods can be arranged in a variety of ways. If it is fixed at the base, the characteristic bending curve for conical round poles results under a horizontal load acting on the side as in the case of a fishing rod. The pole can be mounted in an articulated manner, if its stability is assured by means of stays or other structural measures.Highly stable loadbearing systems are produced by joining poles to form tripods.When these are invented, they form a table-like structure which, with minimum contact with the ground, is stable.
In view of the fact that vegetal poles are generally relatively slender, measures to increase the loadbearing capacity are often required. Bundled poles are extremely common in order to transfer larger forces over small paths since bunbles achieve a larger loadbearing capacity than the pure addition of individual poles. The cantilever girder, as "half_beam with central support" requires a support capable of assuming bending moments from the restraint.
konstruktions skizze
Half timbering etc.
 		The combination of suspended and strutted frames is a relatively common feature of root strucutures and even bridge structures , the struts being passed on under the tie beam, thus forming further supports for the tie.Trusses can be described as a further development of suspended structures and,like these,have only vertical reactions from vertical loads.Parallel-boom girders are suitable for bridge and wide-spanned deck structures.
konstruktions skizze
Framework gratings
 Trusses arranged parallel to one another can be connected by means of spatial diagonals or crossing to form framework gratings.
konstruktions skizze
Several roof forms
 Pitched roofs are typival pole structures.Shed roofs are often placed in front of solid buildings as lightweight,hung-in structures;the front support can then be designed as a suspended column mounted in an articulated manner.






Poles joined to one another.





In case of larger spans,the loadbearing capacity of the poles can be increased by means of collar beams which reducse the spans of the rafters and, thus ,their sag.
konstruktions skizze
Curved surfaces with straight rods
 Spatial reinforcement by means of diagonal poles is required in order to transfer the often considerable horizontal loads which occur with towers.





Straight poles can be used to produce curved surfaces,so-called ruled surfaces.As far as building with poles is concerned, the anticlastically curved surfaces of the hyperbolic paraboloid and the hyperboloid of revolution are particularly interesting. The geodesic dome forms an approximation to a synclastically curved surface.In the case of this structure,special importance is placed on the joint with the connections for the poles which are not situated in one plane.

Deflection Curve

  
biegelinien
Conical forms
 Uniform bending results in optimum structural arch and shell forms,as well as suspended roof forms which is basically differ from structures made up of poles of an even thickness.Poles with an even amount of taper do not necessarily have the same deflection curve, even if the material properties are the same.The pole sections a, b and c have the same amount of taper; however they have different deflection curves.The cause of these differences in their deflection curves lies in the fineness of the poles.
schaumstoffversuch
Trials with foamed material
 In order to clearly indicate the general regularities of the deflection curve , trials were conducted using poles made of foamed material. Foamed material is free from the inherent irregularities of natural poles.The advantage of this is that even under their own weight,the deflection curves are more pronounced than in the case of wood or bamboo.











Beams with one support
The centre of gravity of the curved pole is not the same as that of the straight pole,since the length of the lever arms is reduced as result of deflection.The hgest point of the deflection curve is higher than the support point.
schaumstoffversuch
STrials with foamed material, two beams
 Beams with two supports
There are many different possibilities:

1. A certain support position exists at which only vertical reactions accur( both in the case of fixed and movable suports)

2. In the case of movable supports, the sag of the beam can be varied within a certain range before it falls

3. Reduced space between the supports











Inclined beams
The catenary is above the deflection curve in the upper section and below it in the lower section.This shape is well known.It is typical for temple roofs in the far east.


The IL has developed a procedure that makes it possible to provide a sufficiently accurate estimate of the loadbearing behaviour.The BIC-diagram is capable of doing just this.



Constructive details

 At the university in Bogota,Colombia, there is the bamboo research centre CIBAM, organisation whose aim is to use South American gadua for construction purposes.The highly resistant stalks of these bamboo species have a relatively low tensile strength in the transverse plane, thus meaning that when forming details little consideration need be given to the risk of splitting as is usually the case with bamboo

In order to put this building material to effective use, the CIBAM have published a manual of bamboo structures in which individual pilot projects are represented. Therefore is this site.

Fundamental detail connections for a variety of joints for columns, beams and struts have been developped and tested on the basis of the material properties of this species of bamboo.

Here are some examples:

A frame structure with braces,the arrangement of any required reinforcements in the case of large spans or heavy loads, as well as the necessary detail connections.
Effective connections for diagonal struts and posts in a frame work girder.
Umbrella-like tapered roof structure with a suspended column, as well as the arrangement of the struts.
Manufacture water pipes using bamboo tubes with diaphragms which have been drilled open.
Complex bridge structure which operates according to the scissors principle and is suitable for crossing ravines.

Triple Boom Trussed Beam

  
dreigurt-fachwerkträger
Dreigurt Fachwerkträger


 Triple Boom Trussed Beam CIBAM has developped a new lightweight bamboo beam which can be easily produced.The prototype presented here has a width of 2m and is 8m long. Because of the stability and flexibility of bamboo it is highly resistant against earthquakes.The beams can be covered by various materials.


Residential buildings

  
siedlung
Bamboo buildings in Manizales

Residential estate constructed with bamboo in Manizales

Manizales is a small town ca.2500 m above sea level in a coffee growing area west of Bogota.
In order to reduce the housing shortage, the Instituto de Credito Territorial of the Manizales region is pursuing a policy of developing new housing estates which often have a low housing density and are located on expropriated ground and on steep slopes. The ICT is a state organisation for the development of housing programmes for the socially most deprived groups of the population.
grundriss
schnitt

bambusgerüst
bretterschalung
verputzt
Malabar Project

Malabar Project

The Malabar project is one of the residential building projects of the Instituto de Credito Territorial.
They tried to build under consideration of social and cultural values on the one and the use of regional building materials. Most of the building material is bamboo. It grows nearby and its handling is well known by the inhabitants.
Each dwelling unit has a surface area of 6 to 7mThe dwellings consist of living room and bedroom,kitchen and WC.They are lit and ventilated via a patio.
The main columns stand on concrete foundations. They are stiffened by diagonal braces. The dwellings were erected by the residents themselves who had no special training. They organised themselves, however, in an association and carried out the building work under the supervision of the ICT. On completion of the building work, which had progressed swiftly, the individual dwellings were allocated to the members in a raffle.

Engineering

  
der bau
Bamboo tower

Bamboo Tower At The "Phänomena" In Zürich

Among numerous other interesting buildings exhibited at the "Phänomena" 1984 in Zürich, an enormous bamboo structure designed by the Zürich artist Johannes Peter Staub was erected. 250t of bamboo were used over a building period of four months. The canes had been felled in China in previous autumn. The design and size of the building required canes of 6 to 11 cm diameter. Such dimensions are only achieved by bamboo plants whose rhizomes are about 20 years old. They erected a structure consisting of a hexagonal 3-storey building covering an area of 21 to 21m from which two staircase towers projected up to 20m. The design was based on a precise hexagonal grid having an edge length of 2.40m. Single-storey elements fabricated in situ were placed on this grid and on top of these further elements, which also had been fabricated at the site, were placed and suitable braced. The maximum span was 4.8m.
knoten
knoten
Details
turm
Eleavation
In the previous years an experimental structure had been erected in Kunming. The tests were necessary because until them bamboo buildings in China never exceeded a height of 8m and because a bamboo structure the bamboo tower of Zürich can be subjected to oscillations because of its relatively soft joints and nodal points. The equipment of the structure was kept very simple. Since the building was intended to be used only during the summer, the open wall elements were either covered by cloth or left uncovered, and the top platform was protected against rain only by a thin foil cover. From its towers and terraces the building afforded a very good view over the exhibition ground. On the ground floor there was a permanent kitchen which supplied the associated restaurant. The restaurant furniture was constructed from bamboo wast pieces remaining after the completion of the structure.

Umbrellas

  
asiatische schirme
Asian umbrellas

Asian umbrellas

If the umbrella has a simple design, for which 38 bars are normally used, it is now ready for use. Finer umbrellas, for which the bars (up to 60 in number) have a more slender cut, are often painted in an artistic manner, and the handles wound with rattan.
schirm
schirm
European umbrellas

European Umbrellas

Extremely curved bars are possible in the case of European umbrellas with a textile covering which is also cut to size in individual triangular sections.This is possible dut to the fact that the fabric is capable of sustaining considerable tensileforces transverse to the bars, thus enabling the bars to the bent considerably when the umbrella is open.