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Structural Assessment of Three-Dee Structures
Based On Auckland University Testing
Three Dee is a construction system primary classified as structural wall and floor systems. In such structures the gravity and lateral loads are carried by a system of wall diaphragms distributed within the building.
Information from overseas research and testing at Auckland University prove that Three Dee walls have excellent structural properties briefly summarized bellow :
Composite Action.
There are no reports from overseas observing de-lamination of the panel due to failure of the diagonal truss spacers. During the testing program at the Auckland University the tested panels behaved as integral structural elements during the entire loading procedure.
Strength.
a) In-plane. The strength of the Three Dee panel was calculated using the conventional concrete theory which was proved by the test results. The mechanical properties of the mesh wire were determined in the lab and actual tensile strength of the steel was used.
b) Out-of-Plane. The strength of the Three Dee panel with only mesh acting was calculated using conventional concrete theory.
In both cases the strength is comparable with reinforced concrete walls (panels) and superior to the walls constructed from concrete blocks.
Ductility.
During the testing program at the Auckland University ductility factor of 4 was achieved (maximum requirement is only 3 cycles). During testing the panels remained mainly elastic with yielding concentrated at the base of the wall.
Axial Load Capacity.
Based on overseas research and theoretical investigations in NZ the capacity of the Three Dee panel to resist axial load was found to be excellent. Due to the composite action of the panel and favorable location of the mesh (not in the middle), higher loads can be successfully supported on the Three Dee panels.
Connection Details.
Practical and cost efficient connection details have been developed to and successfully tested at Auckland University.
Based on these results the following conclusions are made :
Three Dee has a superior strength and ductility.
Structural systems with Three Dee panels have excellent ability to resist gravity loads.
Structural systems with Three Dee panels have superior lateral resistance capacity.
Because of the above, Three Dee is suitable for high risk earthquake zoning, without additional structural elements (columns, beams etc.).
Because the 2 layers of re-mesh are placed off-centres of the wall, Three Dee is very efficient in high walls, having an excellent thickness to height ratio.
Three Dee panels can be successfully used as flooring members for residential buildings, fencing, etc. and provide economic alternatives to the traditional systems.
Three Dee panels have no natural weakness spots and low maintenance during the design life of the structure.
Three Dee System is a superior structure, combining the strength of steel, the insulation of polystyrene and the durability of concrete.
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Summary of Test Report from Auckland University (PDF format)