The principles of structural behaviour are determined by applying loads to a theoretical "string line" in much the same way as domed structures were designed in the early 18th century.  Loads were hung off a string simulating the self weight of the dome.  The shape the string took up was mapped and inverted and this was the shape to which the dome was built.  The tension in the string line was then measured and the thickness of the dome designed.  This is just like the loading on a trampoline when a person jumps on it.

ptarch incorporates a similar design process, using the string line to size members in structural steel and to determine the amount of force with which to pre-load (or store energy in) the structure.

Nothing however, is known of deflections using this approach, so these members and the string line are then modelled using sophisticated software which calculates the loads in the members and the deflections of the structure.

In practice, the string line physically exists as a post-tensioned cable system and is loaded to the calculated forces by hydraulic stressing.  This pre-loads energy into the structure before the application of external forces.

A ptarch solutions is unique in its philosophy to store energy in the structure.  It is the subject of several existing and newly filed patents, which by their very nature define ingenuity and originality.

Light-weight 2D ptarch roof frame trusses are typically manufactured from high grade (450Mpa) steel tube, with high tensile stressing strands placed within the bottom chord of the truss. The strand is stressed and bonded to the bottom chord with high-strength grout.

The grouting process locks-in the post-tensioning forces which act in combination with the balance of the ptarch truss members providing an extremely strong structural element.

ptarch post-tensioned truss systems are detailed using simple joint plates, "half moons" and end plate connections.  All lengths are simple curves or straight members, easily bolted together on site.  This means that while large truss elements were produced, all members are easily transported and erected using relatively light lifting equipment.

ptarch can incorporate the specific materials and products of our Licensees, enabling their business to sell solutions in the growing clear span market and move up the value chain.