[week 5] mechanical testing manual

Design

A criteria in the design that will be tested is that it is totally biodegradable. This means that no synthetic glue or steel will be used, only wood and straw. Straw plates used in this test are from BCA-Boards and have known properties for structural use. Other properties like moisture effects will have to be taken into account with this material.

The design given has a span of nine meters with a limited height. The roof is a major challenge. So selecting, designing and testing of the roof have first priority. Second priority is the ground floor however that is not dealt with in this test.

Three variants for the roof are designed. Each group of 3 students will work on a different variant.

Variant 1, solid wood

This solid wood construction is manufactured by Inholz in Germany. They say no other materials than wood are used. Pieces of wood are connected with wood pins to make a solid floor prevent different bending of the beams.

Theoretical a span of 9 m is possible. Only to find these wood lengths is difficult. This can be solved by making cold connections. The pieces of wood next to the joint will transfer the load. Profiles like in section A will be available.

Variant 2, I-beam

A common FJI-beam has Kerto flenges and a wood particle board with a glue connection. The space between the beams can be filled with insulation.

This has been transformed to an I-shape without the use of glue. The connection between the straw board web and wood flenge is with a milled dove tail. A factory could mill these profiles very precise. We will have to do it with hand milled profiles which take some time to make it fit. Milling will be done by the Civil Engineering staff.

To connect the flanges an interlocking piece of wood can be placed between the flanges. The resulting cross section is half of the solid wood beam.

Variant 3, curved web

Corrugated steel webs are being used in beams. The thin material will not buckle and is strongly attached to the flanges.

This concept could also be applied with boards. The web can be guided trough a curved groove in the flanges.

A more simple solution is to let the web fit in holes in the flange. This can be made in the factory with milling or laser cutting.

To connect the flanges an overlapping board can be placed with wood pins.

Testing

Pressure will be put on the beams to create a bending moment. The distance it deflects is linear related with the time. Occurring force will be measured.