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(74) Connections of the ZERI-Pavillion

(74) Verbindungen des ZERI-Pavillions

Type A:
Threaded bolt, embedded in mortar

A hole is drilled into 2 or 3 Internodes, as well as through the same number of diaphragms from the end of the tube. A steel bolt is inserted through the holes in the nodes and then mortar is injected through the holes in the culm wall to fix the steel pole.
A second tube can be put perpendicularly on the steel bolt at the end of the tube: This tube is drilled through completely in the middle of an internode and then gets connected to the other culm. Again, this internode is filled up with mortar. A nut with a special curved washer fixes the connection.
This washer has to fit exactly the curve of the culm, otherwise the high forces would easily split the culm wall.

The tests at the FMPA-Stuttgart reached tensile forces of 70 kN. The initial slippage observed was very small. The specimens failed because of splitting of the bamboo at the end of the tube. Load capacity can be increased byadding a clamp.

Type B:
Lateral steel tabs and bolts, embedded in mortar

2 to 3 internodes are drilled through completely at the end of a tube. Drilling has to be carried out from outside everytime to not split the bamboo. Bolts with screw threads are put through these holes and then the internodes are filled up with mortar. Now, a steel sheet is connected with screws to the bolts. This steel sheet holds the second tube.
The steel sheet presses the second tube to the end of the first one like a belt. The internode of the second tube, which is holded by the 'belt', must also be filled up with mortar, to not get "squashed" in this area. Again, special formed washers are used to fix the flat bar.

The connection type B showed a mean initial slip of approximately 1,5 mm, but resulted in approximately 140 kN mean load, which is twice the load of connection type A. This type failed because of extreme deformation of the holes of the steel sheet and splitting of the bamboo tube.

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Author and Copyright: Dipl.-Ing. Christoph Tönges
Translation: Victor Löffler --- 06.08.2002 --- last update: 11.02.2004